Dr. Jeff Masters' WunderBlog

Why did Hurricane Sandy take such an unusual track into New Jersey?

By: JeffMasters, 4:33 PM GMT on October 31, 2012

We're used to seeing hurricane-battered beaches and flooded cities in Florida, North Carolina, and the Gulf Coast. But to see these images from the Jersey Shore and New York City in the wake of Hurricane Sandy is a shocking experience. New Jersey only rarely gets hit by hurricanes because it lies in a portion of the coast that doesn't stick out much, and is too far north. How did this happen? How was a hurricane able to move from southeast to northwest at landfall, so far north, and so late in hurricane season? We expect hurricanes to move from east to west in the tropics, where the prevailing trade winds blow that direction. But the prevailing wind direction reverses at mid-latitudes, flowing predominately west-to-east, due to the spin of the Earth. Hurricanes that penetrate to about Florida's latitude usually get caught up in these westerly winds, and are whisked northeastwards, out to sea. However, the jet stream, that powerful band of upper-atmosphere west-to-east flowing air, has many dips and bulges. These troughs of low pressure and ridges of high pressure allow winds at mid-latitudes to flow more to the north or to the south. Every so often, a trough in the jet stream bends back on itself when encountering a ridge of high pressure stuck in place ahead of it. These "negatively tilted" troughs have winds that flow from southeast to northwest. It is this sort of negatively tilted trough that sucked in Sandy and allowed the hurricane to take such an unusual path into New Jersey.


Figure 1. Inlet section of Atlantic City, N.J., after Hurricane Sandy. Image credit: 6 ABC Action News.

The 1903 Vagabond Hurricane
The only other hurricane to hit New Jersey since 1851 besides Sandy was the 1903 Category 1 Vagabond Hurricane. According to Wikipedia, the Vagabond Hurricane caused heavy damage along the New Jersey coast ($180 million in 2006 dollars.) The hurricane killed 57 people, and endangered the life of President Theodore Roosevelt, who was sailing on a yacht near Long Island, NY, when the hurricane hit. However, the Vagabond Hurricane hit in September, when the jet stream is typically weaker and farther to the north. It is quite extraordinary that Sandy was able to hit New Jersey in late October, when the jet stream is typically stronger and farther south, making recurvature to the northeast much more likely than in September.


Figure 2. The path of the 1903 Vagabond Hurricane, the only other hurricane to hit New Jersey since 1851.

The blocking ridge that steered Sandy into New Jersey
A strong ridge of high pressure parked itself over Greenland beginning on October 20, creating a "blocking ridge" that prevented the normal west-to-east flow of winds over Eastern North America. Think of the blocking ridge like a big truck parked over Greenland. Storms approaching from the west (like the fall low pressure system that moved across the U.S. from California to Pennsylvania last week) or from the south (Hurricane Sandy) were blocked from heading to the northeast. Caught in the equivalent of an atmospheric traffic jam, the two storms collided over the Northeast U.S., combined into one, and are now waiting for the truck parked over Greenland to move. The strength of the blocking ridge, as measured by the strength of the North Atlantic Oscillation (NAO), was quite high--about two standard deviations from average, something that occurs approximately 5% of the time. When the NAO is in a strong negative phase, we tend to have blocking ridges over Greenland.


Figure 3. Jet stream winds at a pressure of 300 mb on October 29, 2012, as Hurricane Sandy approached the coast of New Jersey. Note that the wind direction over New Jersey (black arrows) was from the southeast, due to a negatively tilted trough of low pressure over the Eastern U.S. caused by a strong blocking ridge of high pressure over Greenland. Image credit: NOAA/ESRL.

Arctic sea ice loss can cause blocking ridges
Blocking ridges occur naturally, but are uncommon over Greenland this time of year. According to NOAA's Climate Prediction Center, blocking near the longitude of Greenland (50°W) only occurs about 2% of the time in the fall. These odds rise to about 6% in winter and spring. As I discussed in an April post, Arctic sea ice loss tied to unusual jet stream patterns, three studies published in the past year have found that the jet stream has been getting stuck in unusually strong blocking patterns in recent years. These studies found that the recent record decline in Arctic sea ice could be responsible, since this heats up the pole, altering the Equator-to-pole temperature difference, forcing the jet stream to slow down, meander, and get stuck in large loops. The 2012 Arctic sea ice melt season was extreme, with sea ice extent hitting a record lows. Could sea ice loss have contributed to the blocking ridge that steered Sandy into New Jersey? It is possible, but we will need to much more research on the subject before we make such a link, as the studies of sea ice loss on jet stream patterns are so new. The author of one of the new studies, Dr. Jennifer Francis of Rutgers, had this say in a recent post by Andy Revkin in his Dot Earth blog: "While it’s impossible to say how this scenario might have unfolded if sea-ice had been as extensive as it was in the 1980s, the situation at hand is completely consistent with what I’d expect to see happen more often as a result of unabated warming and especially the amplification of that warming in the Arctic."

Jeff Masters

Hurricane

Updated: 4:34 PM GMT on October 31, 2012

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Superstorm Sandy delivers a devastating blow to the U.S.

By: JeffMasters, 3:23 PM GMT on October 30, 2012

In a stunning spectacle of atmospheric violence, Superstorm Sandy roared ashore in New Jersey last night with sustained winds of 90 mph and a devastating storm surge that crippled coastal New Jersey and New York. Sandy's record size allowed the historic storm to bring extreme weather to over 100 million Americans, from Chicago to Maine and from Michigan to Florida. Sandy's barometric pressure at landfall was 946 mb, tying the Great Long Island Express Hurricane of 1938 as the most powerful storm ever to hit the Northeast U.S. north of Cape Hatteras, NC. New York City experienced its worst hurricane since its founding in 1624, as Sandy's 9-foot storm surge rode in on top of a high tide to bring water levels to 13.88' at The Battery, smashing the record 11.2' water level recorded during the great hurricane of 1821. Damage from Superstorm Sandy will likely be in the tens of billions, making the storm one of the five most expensive disasters in U.S. history.


Figure 1. Morning satellite image of Superstorm Sandy taken at 10 am EDT Tuesday, October 30, 2012. Image credit: NASA GSFC.


Figure 2. Sandy's storm surge (green line) at New York City hit 9' near 9 pm EDT, right when water levels due to high tide (blue line.) The total storm tide (red line) reached 13.88 above Mean Lower Low Water, an all-time record for NYC. Image credit: NOAA Tides and Currents.


Figure 3. Storm surge forced the Delaware River in Philadelphia to a crest of 10.62 feet at 4 a.m. EDT this morning, breaking the previous record of 10.50 feet set Apr. 17, 2011 and Nov. 25, 1950. Image credit: NOAA.

Sandy sets all-time low pressure records
Sandy's impact has been so severe over such a wide area that it is difficult to adequately document the event. I'll start with some of the major cities that set all-time low pressure records during Sandy, with the new record followed by the old record and date of occurrence (thanks go to wunderground weather historian Christopher C. Burt for putting this list together):

Atlantic City, NJ: 28.01"/948mb 28.37"/961mb 3/6/1932

Philadelphia, PA: 28.12"/953mb 28.43"/963mb 3/13/1993

Harrisburg, PA: 28.46"/964mb 28.62"/969mb 1/3/1913

Scranton, PA: 28.69"/971mb 28.72"/973mb 2/25/1965

Trenton, NJ: 28.31"/958mb 28.43"/963mb 3/13/1993

Baltimore, MD: 28.49"/965mb 28.68"/971mb 3/3/1932

Harrisburg, PA: 28.46"/964mb 28.62"/969mb 1/3/1913

Cities that came close to setting their all-time low pressure record:

Newark, NJ: 28.51"/965mb 28.45"/963 3/13/1993

New York, NY: 28.53"/966mb 28.38"/961mb 3/1/1914

Washington D.C. 28.63"/969mb 28.54/966mb 3/13/1993

Lynchburg, VA: 29.12"/986mb 28.84"/977mb 3/6/1932

Elkins, WV: 29.22"/989mb 28.85"/977mb 2/25/1965

Sandy's snows
Sandy's snows have clobbered the town of Davis, WV with an estimated 26 - 28" of snow. Most of the town is without power, and winds are blowing 20 - 30 mph with 40 mph gusts. Sandy brought the snowiest October day on record to both Elkins, WV (7" of snow) and Bluefield, WV (4.7".)


Video 1. Multiple trees fall during powerful gusts during Superstorm Sandy's landfall in New Jersey Monday evening (warming: foul language.)

There's so much more to say about Sandy--including how the storm may have been influenced by climate change--but I'll save this for later posts, as it's time to get something posted.

Angela Fritz has a 2:30 pm EDT post that discusses the latest on Sandy's impact and forecast.

Jeff Masters

Hurricane

Updated: 7:31 PM GMT on November 05, 2012

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Sandy moving ashore, bringing record storm surge flooding

By: JeffMasters, 10:40 PM GMT on October 29, 2012

Hurricane Sandy is making its final approach, and will be ashore near the Delaware/new Jersey border early this evening. The scale of this massive storm truly earns Sandy the title of "superstorm", and no storm since at least 1988 has struck the U.S. with a wider area of tropical storm-force winds. High wind warnings are posted from Northern Michigan to Lake Okeechobee, Florida, and from Chicago to Maine. All-time low pressure records have been set at Atlantic City, NJ, Philadelphia, PA, and Wilmington Delaware. The rain is coming down in sheets along the east coast, where heavy rain stretches from Virginia to Pennsylvania and New York. Virginia Beach, VA has seen 9.26", Dover, DE has seen 6.36" and Ocean City, MD has seen 6.31". Some of the heaviest rain, apart from close to the center, is actually on the far western side, where a strong band of precipitation has set up running north to south from Erie, PA south to Pittsburgh, PA. This strong band of rain is moving west into Ohio. Wind gusts have been peaking above 80 mph in New York, Rhode Island, and Massachusetts this afternoon. The strongest gusts we've seen today include 86 mph at Westerly, RI, 84 mph on Plum Island, NY, and 83 mph on Cuttyhunk Island, MA. Sustained winds speeds of 40+ mph stretch from Delaware to Rhode island, with the strongest sustained wind closest to the center of circulation in Lewes, DE. All of this strong, onshore wind has been pushing huge amounts of water toward the shore, where it has nothing to do but pile up over land. As of 5pm EDT, here are the highest storm surges seen:

Kings Point, NY: 7.85 ft
Sandy Hook, NJ: 7.55 ft
Bridgeport, CT: 7.3 ft
New Haven, CT: 6.82 ft
The Battery, NY: 6.7 ft
New London, CT: 5.76 ft
Atlantic City, NJ: 5.69 ft
Lewes, DE: 4.46 ft

We just added live tide gauge heights on our wundermap, so you can follow the changes in surge as Sandy roars ashore.


Figure 1. MODIS satellite image of Hurricane Sandy taken at 2:20 pm EDT Monday, October 29, 2012. At the time, Sandy was a Category 1 storm with 90 mph winds. Image credit: NASA.

Sandy bringing high winds all the way to Chicago
The scope of this storm is truly astonishing. As Sandy combines with the fall low pressure system over the Northeast U.S., its circulation will intensify, and winds over the Great Lakes will increase. Storm warnings are posted for Tuesday on Lake Michigan near Chicago, where sustained 55 - 60 mph winds and waves of 20 - 25 feet are expected. Storm warnings are posted on Lake Erie and Lake Ontario, and high winds from Sandy blowing off of Lake Erie caused damage to signs in Port Clinton, Ohio this afternoon. Check out this webcam view of a very angry Lake Erie. High wind warnings extend from northern Michigan to Central Florida.

Sandy's storm tide peaking early this evening
Storm surge should peak between 7 - 8 pm, and high tide will peak a little later, 8 - 9 pm, depending upon location. The storm tide--how high the water gets above some reference point, commonly chosen to be the average of the daily lowest low tide of the month (Mean Lower Low Water, MLLW) is what we use to discuss how bad storm surge flooding is. The storm tide is the combination of the storm surge and the tide. At Sandy Hook, NJ, the storm tide has reached 10.11', and is still rising. This breaks the old record set by Hurricane Donna in 1960, and the Nor'easter of Dec 11th, 1992. As of 6 pm EDT, the storm tide at The Battery in New York City was 10.1'. The record is 10.5', set during Hurricane Donna of 1960. That also happens to be the level the Lower Manhattan subway system will flood, unless the defenses have been improved since last year's Hurricane Irene. High tide is at 8:53 pm. The rise in surge has slowed down, but the surge may not be slowing down fast enough to avoid record flooding in New York City.

Links for Sandy
An impressive 1-minute resolution satellite loop of Sandy today is at the CSU RAMMB website.

Hurricane Sandy info from NASA.

Joe Romm at climateprogress.org has a thoughtful piece called, How Does Global Warming Make Hurricanes Like Irene More Destructive?

Storm Surge prediction model from the Stevens Institute of Technology, which use a highly detailed 3D ocean model and even includes rainfall and tributary inflows.

Research storm surge model run by SUNY Stonybrook for New York City.

I have to cut this post a bit short due to the many media interviews I'm involved with, but will be back in the morning with much more.

Jeff Masters and Angela Fritz

Hurricane

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Superstorm Sandy intensifying, bringing record storm surges

By: JeffMasters, 2:54 PM GMT on October 29, 2012

The final countdown to Hurricane Sandy's arrival has begun, and this extraordinary and historic storm is already causing havoc all along the U.S. coast from North Carolina to Massachusetts. The scale of this massive storm truly earns Sandy the title of "superstorm". Sandy's tropical storm-force winds span an area of ocean 940 miles in diameter, and both North Carolina and the island of Bermuda, 700 miles to the east, are under tropical storm warnings. The region of ocean covered by 12-foot high seas spans an area of ocean an incredible 1560 miles in diameter. Winds near hurricane force are expected to affect waters from Virginia to Massachusetts today. Record storm surge flooding has already occurred in regions along the New Jersey coast this morning, and the highest water levels recorded in over a century of record keeping are expected over much of the New Jersey and New York coasts this evening during the 8 - 9 pm EDT high tide cycle. Sandy brought sustained winds of 60 mph and waves 30 feet high early this morning to the buoy east of Cape Hatteras, NC. A wind gust of 58 mph occurred at New York City's La Guardia Airport at 9:51 am EDT, and a buoy at Robins Reef, NJ recorded sustained winds of 42 mph, gusting to 55 mph. As of 8 am EDT, Sandy has dumped heavy rains of 7.87" at Cape Hatteras, NC; 4.01" at Ocean City, MD; 3.12" at Dover, DE; and 3.22" at Virginia Beach, VA. As of 9 am EDT, peak storm surge values of 5" were observed at Lewes, Delaware, 4.2' at Cape May, NJ, 4' at Atlantic City, NJ, 2.9' at Philadelphia, and 3.9' at New York City.

Latest data from the Hurricane Hunters shows that Sandy is intensifying as its core traverses the warm waters of the Gulf Stream. At 8 am EDT, an Air Force hurricane hunter aircraft found top winds of 98 mph in the heavy thunderstorms to the southwest of Sandy's center, at a point about 150 miles east-northeast of Cape Hatteras, NC. A dropsonde released in the eye measured a central pressure of 945 mb, but observed winds of 19 knots at the surface, so Sandy is probably a 943 mb hurricane that is very close to Category 2 strength. The Hurricane Hunters did not observe an eyewall, and saw very little temperature difference from inside to outside the eye, so Sandy is not going to be able to undergo rapid intensification. The storm could still see an increase of 5 mph in its winds before landfall tonight between 6 pm - 10 pm EDT, due, in part, to interaction with the low pressure system to its west that is pulling the hurricane towards the coast. The new, higher winds of Sandy don't have a lot of time to pile up additional storm surge water, so the NHC storm surge forecasts will probably not change today. But it is clear that Sandy is not going to pull its punch, and this superstorm is going to deliver a punishing multi-billion dollar blow to a huge area of the Eastern U.S.


Figure 1. Morning satellite image of Hurricane Sandy.

Sandy already producing a record storm surge
The National Weather Service in Atlantic City, NJ said that isolated record storm surge flooding already occurred along portions of the New Jersey coast with this morning's 7:30 am EDT high tide cycle. As the tide goes out late this morning and this afternoon, water levels will fall, since the difference in water levels between low tide and high tide is about 5'. However, this evening, as the core of Sandy moves ashore, the storm will carry with it a gigantic bulge of water that will raise waters levels to the highest storm tides ever seen in over a century of record keeping, along much of the coastline of New Jersey and New York. The peak danger will be between 7 pm - 10 pm, when storm surge rides in on top of the high tide. The full moon is today, which means astronomical high tide will be about 5% higher than the average high tide for the month, adding another 2 - 3" to water levels. This morning's 9:30 am EDT H*Wind analysis from NOAA's Hurricane Research Division put the destructive potential of Sandy's winds at a modest 2.9 on a scale of 0 to 6. However, the destructive potential of the storm surge was record high: 5.8 on a scale of 0 to 6. This is a higher destructive potential than any hurricane observed since 1969, including Category 5 storms like Katrina, Rita, Wilma, Camille, and Andrew. The previous highest destructive potential for storm surge was 5.6 on a scale of 0 to 6, set during Hurricane Isabel of 2003. Sandy's storm surge will be capable of overtopping the flood walls in Manhattan, which are only five feet above mean sea level. On August 28, 2011, Tropical Storm Irene brought a storm surge of 4.13' and a storm tide of 9.5' above MLLW to Battery Park on the south side of Manhattan. The waters poured over the flood walls into Lower Manhattan, but came 8 - 12" shy of being able to flood the New York City subway system. According to the latest storm surge forecast for NYC from NHC, Sandy's storm surge is expected to be 10 - 12' above MLLW. Since a storm tide of 10.5' is needed to flood the subway system, it appears likely that portions of the NYC subway system will flood. The record highest storm tide at The Battery was 10.5', set on September 15, 1960, during Hurricane Donna.


Figure 2. Observed storm tide (red line) and predicted storm surge for Hurricane Sandy at The Battery on the south shore of Manhattan, New York City, from the experimental Extratropical Storm Surge model, run by NOAA"s Meteorological Development Laboratory (green line) and the NYHOPS model from the Stevens Institute of Technology (pink curve), which uses a highly detailed 3D ocean model and even includes rainfall and tributary inflows. These models have a storm surge of 5 - 6', which brings the maximum storm tide--the water level reached as a result of the combined action of the tide and the storm surge--to 11' above MLLW (Mean Lower Low Water.) Irene brought a storm tide of 9.5' above MLLW to The Battery in 2011. At a storm tide of 10.5', water will likely pour into the Lower Manhattan subway system, unless efforts to sandbag the entrances are successful. The NWS in NYC is predicting a 10 - 12' storm tide at The Battery during tonight's 9 pm high tide cycle.


Figure 3. Observed storm tide (red line) and predicted storm surge for Hurricane Sandy at Atlantic City, New Jersey, from the experimental Extratropical Storm Surge model, run by NOAA"s Meteorological Development Laboratory (green line) and the NYHOPS model from the Stevens Institute of Technology (pink curve), which uses a highly detailed 3D ocean model and even includes rainfall and tributary inflows. These models predict a maximum storm tide--the water level reached as a result of the combined action of the tide and the storm surge--of ' above MLLW (Mean Lower Low Water.) Irene brought a storm tide of 9.5' above MLLW to The Battery in 2011. At a storm tide of 10.5', water will likely pour into the Lower Manhattan subway system, unless efforts to sandbag the entrances are successful. The NWS in Atlantic City is predicting a 9.5' storm tide for the city during tonight's 8 pm high tide cycle, which would be the highest water levels ever observed in Atlantic City.

Links for Sandy
To find out if you need to evacuate, please contact your local emergency management office. They will have the latest information. People living in New York City can find their evacuation zone here or use this map. FEMA has information on preparing for hurricanes.

People with disabilities and caregivers seeking information on accessible shelter and transportation can contact portlight.org

Atlantic City beach cam

Ocean City, MD webcam

Statue of Liberty cam

An impressive 1-minute resolution satellite loop of Sandy today is at the CSU RAMMB website.

Our Weather Historian, Christopher C. Burt, has an excellent post on Late Season Tropical Storms that have affected the U.S. north of Hatteras. He also has a post, Historic Hurricanes from New Jersey to New England.

Hurricane Sandy info from NASA.

Joe Romm at climateprogress.org has a thoughtful piece called, How Does Global Warming Make Hurricanes Like Irene More Destructive?

For those of you wanting to know your odds of receiving hurricane force or tropical storm force winds, I recommend the NHC wind probability product.

Wunderground has detailed storm surge maps for the U.S. coast.

The National Hurricane Center's Interactive Storm Surge RIsk Map, which allows one to pick a particular Category hurricane and zoom in, is a good source of storm surge risk information.

Storm Surge prediction model from the Stevens Institute of Technology, which use a highly detailed 3D ocean model and even includes rainfall and tributary inflows.

Research storm surge model run by SUNY Stonybrook for New York City.

Climate Central has a nice satellite image showing which parts of New York Harbor are below five feet in elevation.

I'll have an update this afternoon.

Jeff Masters

Hurricane

Updated: 3:15 PM GMT on October 29, 2012

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Dangerous Hurricane Sandy continues north past North Carolina

By: JeffMasters, 9:58 PM GMT on October 28, 2012

Hurricane Sandy has changed little in intensity today, and remains a very large, powerful hurricane. Sandy is going to cause billions of dollars in damage Monday and Tuesday in the Eastern U.S. due to storm surge, high winds, and heavy rains. Sandy is of near record-size, with tropical storm-force winds extending up to 520 miles from its center, covering an area larger than a Texas-and-a-half. This afternoon, Sandy brought winds gusting to 64 mph at Cape Hatteras, NC, 60 mph at Kitty Hawk, NC, and 60 mph at Cape Henry, VA. Sandy's rain is onshore from North Carolina to New Jersey and Pennsylvania. Jacksonville, NC and Suffolk, NC have recorded 2 inches of rain today, Greenville, NC has seen 1.6 inches, and Ahoskie, NC has seen 1.5 inches.

With peak impact still 24 to 36 hours away, water levels are already 2 - 4 feet above normal from Virginia to New York. At 4 pm EDT, Lewes, Delaware was at 3.3 feet above normal, Cape May, New Jersey was at 3.1 feet above normal, Wachapreague, Virginia was at 3.6 feet above normal, and Chesapeake Bay Bridge Tunnel station was at 3.6 feet above normal, up more than half a foot since 10:30am. The National Weather Service in Upton, New York mentioned today that the predicted maximum water level of 11.7 feet at The Battery in New York City, which is expected to occur at 8:13pm ET on Monday, would break the record of 10.5 feet which was set on September 15, 1960 in Hurricane Donna.

In a poignant, powerful Public Information Statement this afternoon, the National Weather Service in New Jersey is begging that people heed warnings, and evacuate if they are asked to. They write, "If you are reluctant [to evacuate], think about your loved ones, think about the emergency responders who will be unable to reach you when you make the panicked phone call to be rescued, think about the rescue/recovery teams who will rescue you if you are injured or recover your remains if you do not survive."


Figure 1. High resolution MODIS visible satellite image of Hurricane Sandy on October 28, 2012.

Intensity and Track Forecast for Sandy
Most of Sandy's heavy thunderstorm activity is on the storm's west side, in a thick band several hundred miles removed from the center, giving Sandy more the appearance of a subtropical storm rather than a hurricane. However, satellite loops show Sandy is steadily looking more tropical, with heavy thunderstorms increasing in areal extent near the center, due to a reduction in wind shear from 35 - 40 knots last night to 20 - 25 knots this afternoon. Wind shear is expected to remain near 20 knots until landfall, and Sandy will be traversing the warm waters of the Gulf Stream. These factors may allow Sandy to intensify by 5 - 10 mph over the next 24 hours. Sandy does not have time to build a complete eyewall and undergo rapid intensification. By Monday afternoon, Sandy will be moving over cool 25°C waters, which should slow down intensification by pulling heat energy our of the ocean. However, the trough of low pressure that will be sucking in Sandy to the northwest towards landfall will strengthen the storm by injecting "baroclinic" energy--the energy one can derive from the atmosphere when warm and cold air masses lie in close proximity to each other. Sandy should have sustained winds at hurricane force, 75 - 80 mph, at landfall. Sandy's central pressure is expected to drop from its current 953 mb to 945 - 950 mb at landfall Monday night. A pressure this low is extremely rare; according to wunderground weather historian Christopher C. Burt, the lowest pressure ever measured anywhere in the U.S. north of Cape Hatteras, NC, is 946 mb (27.94") measured at the Bellport Coast Guard Station on Long Island, NY on September 21, 1938 during the great "Long Island Express" hurricane. The latest set of 12Z (8 am EDT) computer model runs show a little faster motion for Sandy, bringing the center ashore in New Jersey Monday evening near 8 pm EDT.


Figure 2. Predicted storm surge for Hurricane Sandy at The Battery on the south shore of Manhattan, New York City, from the experimental Extratropical Storm Surge model, run by NOAA"s Meteorological Development Laboratory (green line) and the NYHOPS model from the Stevens Institute of Technology (pink curve), which use a highly detailed 3D ocean model and even includes rainfall and tributary inflows. These models have a storm surge of 5 - 6', which brings the maximum storm tide--the water level reached as a result of the combined action of the tide and the storm surge--to 9.7 - 10.8'. Irene brought a storm tide of 9.5' to The Battery in 2011. At a storm tide of 10.5', water will likely pour into the Lower Manhattan subway system, unless efforts to sandbag the entrances are successful. Notice: these are not an official NHC storm surge forecast.


Figure 3. Predicted and forecast water level for Atlantic City, NJ. The dark red line is the observation, rom the experimental Extratropical Storm Surge model, run by NOAA"s Meteorological Development Laboratory (green line) and the NYHOPS model from the Stevens Institute of Technology (pink curve), which use a highly detailed 3D ocean model and even includes rainfall and tributary inflows.

Sandy's storm surge a huge threat
This afternoon's 3:30 pm EDT H*Wind analysis from NOAA's Hurricane Research Division put the destructive potential of Sandy's winds at a modest 2.8 on a scale of 0 to 6. However, the destructive potential of the storm surge was record high: 5.8 on a scale of 0 to 6. This is a higher destructive potential than any hurricane observed since 1969, including Category 5 storms like Katrina, Rita, Wilma, Camille, and Andrew. The previous highest destructive potential for storm surge was 5.6 on a scale of 0 to 6, set during Hurricane Isabel of 2003. Sandy is now forecast to bring a near-record storm surge of 6 - 11 feet to Northern New Jersey and Long Island Sound, including the New York City Harbor. This storm surge has the potential to cause many billions of dollars in damage if it hits near high tide at 9 pm EDT on Monday. The full moon is on Monday, which means astronomical high tide will be about 5% higher than the average high tide for the month. This will add another 2 - 3" to water levels. Fortunately, Sandy is now predicted to make a fairly rapid approach to the coast, meaning that the peak storm surge will not affect the coast for multiple high tide cycles. Sandy's storm surge will be capable of overtopping the flood walls in Manhattan, which are only five feet above mean sea level. On August 28, 2011, Tropical Storm Irene brought a storm surge of 4.13' and a storm tide of 9.5' above MLLW to Battery Park on the south side of Manhattan. The waters poured over the flood walls into Lower Manhattan, but came 8 - 12" shy of being able to flood the New York City subway system. According to the latest storm surge forecast for NYC from NHC, Sandy's storm surge is expected to be at least a foot higher than Irene's. If the peak surge arrives near Monday evening's high tide at 9 pm EDT, a portion of New York City's subway system could flood, resulting in billions of dollars in damage. I give a 50% chance that Sandy's storm surge will end up flooding a portion of the New York City subway system.

Sandy's winds
Sandy will bring sustained winds of tropical storm-force to a 1000-mile swath of coast on Monday and Tuesday. Winds of 55 - 75 mph with gusts over hurricane force will occur along a 500 mile-wide section of coast. With most of the trees still in leaf, there will be widespread power outages due to downed trees, and the potential for several billion dollars in wind damage. A power outage computer model run by Johns Hopkins University predicts that 10 million people will lose power from the storm.

Sandy's rains
Sandy's heavy rains are going to cause major but probably not catastrophic river flooding. If we compare the predicted rainfall amounts for Sandy with those from Hurricane Irene of 2011, Sandy's are expected to be about 30% less. Hurricane Irene caused $15.8 billion in damage, most of it from river flooding due to heavy rains. However, the region most heavily impacted by Irene's heavy rains had very wet soils and very high river levels before Irene arrived, due to heavy rains that occurred in the weeks before the hurricane hit. That is not the case for Sandy; soil moisture is near average over most of the mid-Atlantic, and is in the lowest 30th percentile in recorded history over much of Delaware and Southeastern Maryland. One region of possible concern is the Susquehanna River Valley in Eastern Pennsylvania, where soil moisture is in the 70th percentile, and river levels are in the 76th - 90th percentile. This area is currently expected to receive 3 - 6 inches of rain, which is probably not enough to cause catastrophic flooding like occurred for Hurricane Irene. I expect that river flooding from Sandy will cause less than $1 billion in damage.

Links for Sandy
To find out if you need to evacuate, please contact your local emergency management office. They will have the latest information. People living in New York City can find their evacuation zone here or use this map. FEMA has information on preparing for hurricanes.

People with disabilities and caregivers seeking information on accessible shelter and transportation can contact portlight.org

Atlantic City beach cam

Statue of Liberty cam

An impressive 1-minute resolution satellite loop of Sandy today is at the CSU RAMMB website.

Our Weather Historian, Christopher C. Burt, has an excellent post on Late Season Tropical Storms that have affected the U.S. north of Hatteras. He also has a post, Historic Hurricanes from New Jersey to New England.

Hurricane Sandy info from NASA.

Joe Romm at climateprogress.org has a thoughtful piece called, How Does Global Warming Make Hurricanes Like Irene More Destructive?

For those of you wanting to know your odds of receiving hurricane force or tropical storm force winds, I recommend the NHC wind probability product.

Wunderground has detailed storm surge maps for the U.S. coast.

The National Hurricane Center's Interactive Storm Surge RIsk Map, which allows one to pick a particular Category hurricane and zoom in, is a good source of storm surge risk information.

Storm Surge prediction model from the Stevens Institute of Technology, which use a highly detailed 3D ocean model and even includes rainfall and tributary inflows.

Research storm surge model run by SUNY Stonybrook for New York City.

Climate Central has a nice satellite image showing which parts of New York Harbor are below five feet in elevation.

We'll have an update on Sandy Monday morning.

Angela Fritz and Jeff Masters

Hurricane

Updated: 11:32 PM GMT on October 28, 2012

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Massive Hurricane Sandy building a huge and destructive storm surge

By: JeffMasters, 2:34 PM GMT on October 28, 2012

Massive and dangerous Hurricane Sandy has grown to record size as it barrels northeastwards along the North Carolina coast at 10 mph. At 8 am EDT, Sandy's tropical storm-force winds extended northeastwards 520 miles from the center, and twelve-foot high seas covered a diameter of ocean 1,030 miles across. Since records of storm size began in 1988, only one tropical storm or hurricane has been larger--Tropical Storm Olga of 2001, which had a 690 mile radius of tropical storm-force winds when it was near Bermuda (note: I earlier reported this was a subtropical storm, as per the original NHC advisory, but it was later re-analyzed as a tropical storm.) Sandy has put an colossal volume of ocean water in motion with its widespread and powerful winds, and the hurricane's massive storm surge is already impacting the coast. A 2' storm surge has been recorded at numerous locations this morning from Virginia to Connecticut, including a 3' surge at Virginia's Chesapeake Bay Bridge Tunnel and Sewells Point at 9 am EDT. Huge, 10 - 15 foot-high battering waves on top of the storm surge have washed over Highway 12 connecting North Carolina's Outer Banks to the mainland at South Nags Head this morning. The highway is now impassable, and has been closed. The coast guard station on Cape Hatteras, NC, recorded sustained winds of 50 mph, gusting to 61 mph, at 5:53 am EDT this morning. In Delaware, the coastal highway Route 1 between Dewey Beach and Bethany Beach has been closed due to high water. Even though Sandy is a minimal Category 1 hurricane, its storm surge is extremely dangerous, and if you are in a low-lying area that is asked to evacuate, I strongly recommend that you leave.


Figure 1. A fright to behold: morning satellite image of massive Hurricane Sandy.

Sandy's death toll now at 65
Sandy was a brutal storm for the Caribbean, the storm's death toll now stands at 65. The death toll is highest in Haiti, with 51 deaths. Prime Minister Laurent Lamothe told the Associated Press that "This is a disaster of major proportions. The whole south is under water." Approximately 8 - 10" of rain (200 - 250 mm) fell in the capital of Port-au-Prince. Eleven people were killed in Cuba, where 35,000 homes were damaged or destroyed. Sandy is also being blamed for 1 death in Jamaica, 1 in Puerto Rico, and 1 in the Bahamas.


Figure 2. A resident carries a metal sheet from a house after heavy rains damaged by Hurricane Sandy in Port-au-Prince, Haiti, Thursday, Oct. 25, 2012. Sandy is being blamed for 51 deaths in Haiti. (AP Photo/Dieu Nalio Chery)


Figure 3. Satellite-estimated rainfall amounts from NASA's TRMM satellite show that portions of Haiti received over 12.75" (325 mm) of rain (pink colors) from Hurricane Sandy. The capital of Port-au-Prince received 8 - 10" (200 - 250 mm.) Image credit: NASA.

Intensity and Track Forecast for Sandy
Sandy has a rather unusual structure, with the strongest winds on the southwest side of the center, but a larger area of tropical storm-force winds to the northeast of the center. Most of the storm's heavy thunderstorm activity is on the storm's west side, in a thick band several hundred miles removed from the center, giving Sandy more the appearance of a subtropical storm rather than a hurricane. Satellite loops show that the low-level center of Sandy is no longer exposed to view, and heavy thunderstorms are increasing in areal extent near the center, due to a reduction in wind shear from 35 - 40 knots last night to 25 - 30 knots this morning. Wind shear is expected to drop another 5 knots today, which may allow the storm to build an increased amount of heavy thunderstorms near its center and intensify by 5 - 10 mph over the next 24 hours. The NOAA Hurricane Hunters noted this morning that Sandy had a partial eyewall on the west through SE sides of the center, and the storm may be able to build a nearly complete eyewall by Monday morning. By Monday afternoon, though, Sandy will be moving over cool 25°C waters, which should slow down this intensification process. However, the trough of low pressure that will be pulling Sandy to the northwest towards landfall on Monday will strengthen the storm by injecting "baroclinic" energy--the energy one can derive from the atmosphere when warm and cold air masses lie in close proximity to each other. Sandy should have sustained winds at hurricane force, 75 - 80 mph, at landfall. Sandy's central pressure is expected to drop from its current 951 mb to 945 - 950 mb at landfall Monday night. A pressure this low is extremely rare; according to wunderground weather historian Christopher C. Burt, the lowest pressure ever measured anywhere in the U.S. north of Cape Hatteras, NC, is 946 mb (27.94") measured at the Bellport Coast Guard Station on Long Island, NY on September 21, 1938 during the great "Long Island Express" hurricane. The latest set of 00Z (8 pm EDT) and 06Z (2 am EDT) computer model runs are in agreement that Sandy will make landfall between 10 pm Monday night and 4 am Tuesday morning in New Jersey.


Figure 4. Predicted maximum storm surge from Hurricane Sandy. There is a 10% chance that the storm surge could exceed the heights given here, so most regions will receive a surge lower than this forecast. The greatest surge is expected in the waters surrounding New York City, since the shape of the bays will act to funnel the water to higher levels.

Sandy's storm surge a huge threat
Last night's 9:30 pm EDT H*Wind analysis from NOAA's Hurricane Research Division put the destructive potential of Sandy's winds at a modest 2.6 on a scale of 0 to 6. However, the destructive potential of the storm surge was exceptionally high: 5.7 on a scale of 0 to 6. This is a higher destructive potential than any hurricane observed between 1969 - 2005, including Category 5 storms like Katrina, Rita, Wilma, Camille, and Andrew. The previous highest destructive potential for storm surge was 5.6 on a scale of 0 to 6, set during Hurricane Isabel of 2003. Sandy is now forecast to bring a near-record storm surge of 6 - 11 feet to Northern New Jersey and Long Island Sound, including the New York City Harbor. While Sandy's storm surge will be nowhere near as destructive as Katrina's, the storm surge does have the potential to cause many billions of dollars in damage if it hits near high tide at 9 pm EDT on Monday. The full moon is on Monday, which means astronomical high tide will be about 5% higher than the average high tide for the month. This will add another 2 - 3" to water levels. Fortunately, Sandy is now predicted to make a fairly rapid approach to the coast, meaning that the peak storm surge will not affect the coast for multiple high tide cycles. Sandy's storm surge will be capable of overtopping the flood walls in Manhattan, which are only five feet above mean sea level. On August 28, 2011, Tropical Storm Irene brought a storm surge of 4.13' to Battery Park on the south side of Manhattan. The waters poured over the flood walls into Lower Manhattan, but came 8 - 12" shy of being able to flood the New York City subway system. According to the latest storm surge forecast for NYC from NHC, Sandy's storm surge is expected to be several feet higher than Irene's. If the peak surge arrives near Monday evening's high tide at 9 pm EDT, a portion of New York City's subway system could flood, resulting in billions of dollars in damage. I give a 50% chance that Sandy's storm surge will end up flooding a portion of the New York City subway system.

An excellent September 2012 article in the New York Times titled, "New York Is Lagging as Seas and Risks Rise, Critics Warn" quoted Dr. Klaus H. Jacob, a research scientist at Columbia University’s Earth Institute, on how lucky New York City got with Hurricane Irene. If the storm surge from Irene had been just one foot higher, "subway tunnels would have flooded, segments of the Franklin D. Roosevelt Drive and roads along the Hudson River would have turned into rivers, and sections of the commuter rail system would have been impassable or bereft of power," he said, and the subway tunnels under the Harlem and East Rivers would have been unusable for nearly a month, or longer, at an economic loss of about $55 billion. Dr. Jacob is an adviser to the city on climate change, and an author of the 2011 state study that laid out the flooding prospects. “We’ve been extremely lucky,” he said. “I’m disappointed that the political process hasn’t recognized that we’re playing Russian roulette.”

Sandy's winds
Sandy will bring sustained winds of tropical storm-force to a 1000-mile swath of coast on Monday and Tuesday. Winds of 55 - 75 mph with gusts over hurricane force will occur along a 500 mile-wide section of coast. With most of the trees still in leaf, there will be widespread power outages due to downed trees, and the potential for several billion dollars in wind damage. A power outage computer model run by Johns Hopkins University predicts that 10 million people will lose power from the storm.

Sandy's rains
Sandy's heavy rains are going to cause major but probably not catastrophic river flooding. If we compare the predicted rainfall amounts for Sandy (Figure 5) with those from Hurricane Irene of 2011 (Figure 6), Sandy's are expected to be about 30% less. Hurricane Irene caused $15.8 billion in damage, most of it from river flooding due to heavy rains. However, the region most heavily impacted by Irene's heavy rains had very wet soils and very high river levels before Irene arrived, due to heavy rains that occurred in the weeks before the hurricane hit. That is not the case for Sandy; soil moisture is near average over most of the mid-Atlantic, and is in the lowest 30th percentile in recorded history over much of Delaware and Southeastern Maryland. One region of possible concern is the Susquehanna River Valley in Eastern Pennsylvania, where soil moisture is in the 70th percentile, and river levels are in the 76th - 90th percentile. This area is currently expected to receive 3 - 6 inches of rain (Figure 4), which is probably not enough to cause catastrophic flooding like occurred for Hurricane Irene. I expect that river flooding from Sandy will cause less than $1 billion in damage.


Figure 5. Predicted 5-day rainfall for the period ending Friday morning, November 2, 2012, at 8am EDT. Image credit: NOAA/HPC.


Figure 6. Actual rainfall for 2011's Hurricane Irene, which caused $15.8 billion in damage, most of it from river flooding due to heavy rains. Sandy's rains are predicted to be about 30% less than Irene's. Image credit: NOAA/HPC.

Sandy's snows
You can add heavy snow to the list of weather frights coming for the Eastern U.S. from Sandy. A WInter Storm Watch is posted for much of southeastern West Virginia for Sunday night through Monday, when 2 - 6 inches of wet, heavy snow is expected to fall at elevations below 2000 feet. At higher elevation above 3,000 feet, 1 - 2 feet of snow is possible. With high wind gusts of 35 - 45 mph and many trees still in leaf, the affected area can expect plenty of tree damage and power outages. Lesser snows are expected in the mountains of Virginia, Tennessee, and North Carolina.

Sandy's tornado threat is minimal
The severe thunderstorm and tornado threat from Sandy Sunday and Monday looks low, due to minimal instability.

Links for Sandy
To find out if you need to evacuate, please contact your local emergency management office. They will have the latest information. People living in New York City can find their evacuation zone here or use this map. FEMA has information on preparing for hurricanes.

People with disabilities and caregivers seeking information on accessible shelter and transportation can contact portlight.org

Corolla, NC webcam

Atlantic City beach cam

Statue of Liberty cam

An impressive 1-minute resolution satellite loop of Sandy today is at the CSU RAMMB website.

This impressive 1-min GOES loop beginning at dawn Saturday shows Sandy's heavy thunderstorms fighting against high wind shear, and the tilt of the vortex to the northeast with height.

Our Weather Historian, Christopher C. Burt, has an excellent post on Late Season Tropical Storms that have affected the U.S. north of Hatteras. He also has a post, Historic Hurricanes from New Jersey to New England.

3-D "fly-around: of the rain towers of Sandy

Hurricane Sandy info from NASA.

Joe Romm at climateprogress.org has a thoughtful piece called, How Does Global Warming Make Hurricanes Like Irene More Destructive?

For those of you wanting to know your odds of receiving hurricane force or tropical storm force winds, I recommend the NHC wind probability product.

Wunderground has detailed storm surge maps for the U.S. coast.

The National Hurricane Center's Interactive Storm Surge RIsk Map, which allows one to pick a particular Category hurricane and zoom in, is a good source of storm surge risk information.

Storm Surge prediction model from the Stevens Institute of Technology, which use a highly detailed 3D ocean model and even includes rainfall and tributary inflows.

Research storm surge model run by SUNY Stonybrook for New York City.

Climate Central has a nice satellite image showing which parts of New York Harbor are below five feet in elevation.


Figure 7. Tide gauge in Kahului, Maui, Hawaii, showing the 2.5' tsunami that hit at approximately 09 UTC Sunday, October 29, 2012. Image credit: NOAA Tides and Currents.

Three-foot tsunami his Hawaii after big quake in Canada
A major magnitude 7.7 earthquake hit 25 miles (40 km) south of Sandspit, British Columbia last night at 8:04 pm PDT. The quake generated a tsunami that raced across the Pacific Ocean and struck Hawaii six hours later. The tsunami reached a height of 2.5 feet in Kahului, Maui, 1.2' at Hilo, and 0.5' in Honolulu. The earthquake was Canada's third largest since 1900. The last stronger quake was a magnitude 7.9 that hit in 1958. The other stronger quake was a magnitude 8.1 that hit in 1949, with an epicenter very close to last night's trembler.

I'll have an update on Sandy this afternoon.

Jeff Masters

Hurricane

Updated: 8:51 PM GMT on October 28, 2012

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Sandy likely to be a multi-billion dollar disaster for the U.S.

By: JeffMasters, 5:28 PM GMT on October 27, 2012

Hurricane Sandy is holding its own against high wind shear of 30 - 40 knots, and has regained its Category 1 strength after falling to tropical storm strength early this morning. Sandy is a massive storm, with tropical storm-force winds that span a 660-mile diameter area of ocean from a point even with central Florida northwards to a point off the central North Carolina coast. Twelve-foot high seas cover a diameter of ocean 1,000 miles across. A buoy 150 miles east of Cape Canaveral, Florida reported sustained winds of 63 mph, gusting to 76 mph, at 9:43 am EDT. Another buoy about 100 miles east of the coast of Georgia reported sustained winds of 69 mph at 11:52 am EDT. Due to the high wind shear and interaction with a trough of low pressure to Sandy's west, the storm has a rather unusual structure, with the strongest winds on the southwest side of the center, but a larger area of tropical storm-force winds to the northeast of the center. Satellite loops show that the low-level center of Sandy is partially exposed to view, with a small clump of heavy thunderstorms near the center. Most of the storm's heavy thunderstorm activity is on the storm's west side, in a thick band several hundred miles removed from the center, giving Sandy more the appearance of a subtropical storm rather than a hurricane.


Figure 1. Early afternoon satellite image of Sandy.

Sandy's death toll at 48
Sandy was a brutal storm for the Caribbean, with a total death toll that now stands at 48. The death toll is highest in Haiti, with 34 dead. The toll will likely rise as remote areas cut off from communications are reached. Cuban state media is reporting that eleven people were killed on Cuba, and damage was heavy, with 35,000 homes damaged or destroyed. Cuba is probably the most hurricane-prepared nation in the world, and it is unusual for them to experience such a high death toll in a hurricane. Sandy was Cuba's deadliest hurricane since Category 4 Hurricane Dennis killed sixteen people in 2005. Sandy is also being blamed for 1 death in Jamaica, 1 in the Bahamas, and 1 in Puerto Rico.

Forecast for Sandy
Wind shear is expected to remain a high 30 - 40 knots for the next two days, as Sandy interacts with a trough of low pressure to its west. The high shear should keep Sandy from intensifying the way most hurricanes do--by pulling heat energy out of the ocean. However, a trough of low pressure approaching from the west will inject "baroclinic" energy--the energy one can derive from the atmosphere when warm and cold air masses lie in close proximity to each other. Sandy's drop in central pressure from 969 mb at 5 am to 960 mb at 8 am this morning may be due, in part, to some baroclinic energy helping intensify the storm. This sort of effect helps spread out the storm's strong winds over a wider area of ocean; Sandy's diameter of tropical storm-force winds are predicted to expand from 660 miles to 760 miles by Sunday afternoon. This will increase the total amount of wind energy of the storm, keeping the storm surge threat very high. This morning's 9:30 am EDT H*Wind analysis from NOAA's Hurricane Research Division put the destructive potential of Sandy's winds at a modest 2.3 on a scale of 0 to 6, However, the destructive potential of the storm surge was exceptionally high: 5.2 on a scale of 0 to 6. Sandy's large wind field will drive a damaging storm surge of 3 - 6 feet to the right of where the center makes landfall. These storm surge heights will be among the highest ever recorded along the affected coasts, and will have the potential to cause billions of dollars in damage. The latest set of 00Z (8 pm EDT) and 06Z (2 am EDT) computer model runs have come into better agreement on the timing and landfall location of Sandy. Our two top models, the ECMWF and GFS, both call for landfall between 10 pm Monday night and 4 am Tuesday morning, with the center coming ashore between Delaware and New York City.

A multi-billion dollar disaster likely in the U.S.
I expect Sandy's impacts along the mid-Atlantic coast and New England coasts to cost at least $2 billion in insured damage and lost business, and there is a danger the storm could cost much more. Steve Bowen, meteorologist for insurance broker AON Benfield, put it this way for me this morning: "Given the level of losses associated with Irene last year and the current projections of extended high wind, heavy rainfall, coastal surge and an inland flooding threat for many of the same areas with Sandy, it would not come as a complete surprise to see a multi-billion dollar economic loss." Sandy should bring sustained winds of 50 - 70 mph with gusts over hurricane force to a large section of coast. With most of the trees still in leaf, there will be widespread power outages due to downed trees, and the potential for a billion dollars in wind damage.


Figure 2. Storm surge from Tropical Storm Irene at The Battery on the south end of New York City's Manhattan Island on Sunday, August 28, 2011. The green line is the storm surge, which is the difference between the observed water level (red line) and what the water level should have been without the hurricane (blue line). At 4:48 am, the storm surge peaked at 4.13 feet. The storm tide--how high the water got when factoring in both the tide and the storm surge--peaked at 9.5' above Mean Lower Low Water (MLLW) at 8:42 am. Image credit: NOAA Tides and Currents.


Figure 3. Predicted storm surge for Hurricane Sandy at The Battery on the south shore of Manhattan, New York City, from the experimental Extratropical Storm Surge model, run by NOAA"s Meteorological Development Laboratory. This model used winds from this morning's 12Z (8 am EDT) run of the GFS model, and predicts that the peak storm surge from Sandy will reach 5.5' on Monday night October 29, which is 1.4' higher than Irene's storm surge. This forecast has the peak surge occurring near high tide, bringing the maximum storm tide--the water level reached as a result of the combined action of the tide and the storm surge--to 10.5', a foot higher than Irene. At this level, water will very likely pour into the Lower Manhattan subway system, unless efforts to sandbag the entrances are successful. Notice: this is not an official NHC storm surge forecast, and the storm surge may be higher or lower than this, depending upon the strength, track, and timing of Sandy.

Sandy's storm surge may flood New York City's subway system, costing billions
Sandy is expected to have tropical storm-force winds that extend out more than 400 miles from the center, which will drive a much larger storm surge than its peak winds would ordinarily suggest. The full moon is on Monday, which means astronomical tides will be about 5% higher than typical, increasing the potential for damaging storm surge flooding. Fortunately, Sandy is now predicted to make a fairly rapid approach to the coast, meaning that the storm surge will not affect the coast for multiple high tide cycles. If Sandy hits near New York City, as the GFS model predicts, the storm surge will be capable of overtopping the flood walls in Manhattan, which are only five feet above mean sea level. On August 28, 2011, Tropical Storm Irene brought a storm surge of 4.13' to Battery Park on the south side of Manhattan. The waters poured over the flood walls into Lower Manhattan, but came 8 - 12" shy of being able to flood the New York City subway system. However, the town of Lindenhurst (population 28,000), on the south side of Long Island, was mostly under water due to the storm surge, and fresh water run-off from Irene's torrential rains, riding on top of a 3 to 4-foot storm surge, allowed the swollen East and Hudson Rivers to overflow at the edges of Manhattan. New York was not as lucky on December 12, 1992, when a 990 mb Nor'easter drove an 8-foot storm surge into Battery Park, flooding the NYC subway and the Port Authority Trans-Hudson Corporation (PATH) train systems in Hoboken New Jersey. FDR Drive in lower Manhattan was flooded with 4 feet of water, which stranded more than 50 cars and required scuba divers to rescue some of the drivers. Mass transit between New Jersey and New York was down for ten days, and the storm did hundreds of millions in damage to the city. The highest water level recorded at the Battery in the past century came in September 1960 during Hurricane Donna, which brought a storm surge of 8.36 feet to the Battery and flooded lower Manhattan to West and Cortland Streets. According to the latest storm surge forecast for NYC from the experimental Extratropical Storm Surge model, run by NOAA"s Meteorological Development Laboratory, Sandy's storm surge may be higher than Irene's, and has the potential to flood New York City's subway system (Figure 4.) The amount of water will depend critically upon whether or not the peak storm surge arrives at high tide or not. If the peak surge arrives near Monday evening's high tide near 9 pm EDT, a portion of New York City's subway system could flood, resulting in billions of dollars in damage. I give a 30% chance that Sandy's storm surge will end up flooding a portion of the New York City subway system.

An excellent September 2012 article in the New York Times titled, "New York Is Lagging as Seas and Risks Rise, Critics Warn" quoted Dr. Klaus H. Jacob, a research scientist at Columbia University’s Earth Institute, on how lucky New York City got with Hurricane Irene. If the storm surge from Irene had been just one foot higher, "subway tunnels would have flooded, segments of the Franklin D. Roosevelt Drive and roads along the Hudson River would have turned into rivers, and sections of the commuter rail system would have been impassable or bereft of power," he said, and the subway tunnels under the Harlem and East Rivers would have been unusable for nearly a month, or longer, at an economic loss of about $55 billion. Dr. Jacob is an adviser to the city on climate change, and an author of the 2011 state study that laid out the flooding prospects. “We’ve been extremely lucky,” he said. “I’m disappointed that the political process hasn’t recognized that we’re playing Russian roulette.” A substantial portion of New York City's electrical system is underground in flood-prone areas. Consolidated Edison, the utility that supplies electricity to most of the city, estimates that adaptations like installing submersible switches and moving high-voltage transformers above ground level would cost at least $250 million. Lacking the means, it is making gradual adjustments, with about $24 million spent in flood zones since 2007. At a conference I attended this summer in Hoboken on natural hazards on urban coasts, I talked to an official with Consolidated Edison, who was responsible for turning off Lower Manhattan's power if a storm surge floods the subway system. He said that he was ready to throw the switch during Irene, but was glad it turned out not to be needed.


Figure 4. Predicted 5-day rainfall for the period ending Thursday morning, November 1, 2012, at 8am EDT. Image credit: NOAA/HPC.


Figure 5. Actual rainfall for 2011's Hurricane Irene, which caused $15.8 billion in damage, most of it from river flooding due to heavy rains. Sandy's rains are predicted to be about 20% less than Irene's. Image credit: NOAA/HPC.



Figure 6. Top: Current soil moisture profiles over the mid-Atlantic show mostly near-average amounts of moisture, with some dry areas in the lowest 30th percentile in recorded history over much of Delaware and Southeastern Maryland. In contrast, soil moisture profiles just before Hurricane Irene arrived, on August 24, 2011 (bottom) ranked in the top 1% in recorded history (dark green colors) over portions of NJ, PA, and NY. Image credit: NOAA/CPC.


Figure 7. A comparison of river levels just before Hurricane Sandy's arrival (left) and just before Hurricane Irene of 2011 (right) shows that river levels were much higher in the mid-Atlantic and Northeast prior to the arrival of Irene. The area of highest concern for river flooding for Sandy is eastern Pennsylvania, where river levels are in the 76 - 90th percentile, and soil moisture is in the 70th percentile. Image credit: USGS.

Sandy's rains
Sandy is expected to dump 5 - 10 inches of rain along the coast near the point the center comes ashore, and 3 - 4 inches several hundred miles inland. Higher isolated rainfall amounts of fifteen inches are likely. Rains of this magnitude are going to cause trouble. If we compare the predicted rainfall amounts for Sandy (Figure 4) with those from Hurricane Irene of 2011 (Figure 5), Sandy's are expected to be about 20% less. Hurricane Irene caused $15.8 billion in damage, most of it from river flooding due to heavy rains. However, the region most heavily impacted by Irene's heavy rains had very wet soils and very high river levels before Irene arrived, due to heavy rains that occurred in the weeks before the hurricane hit. That is not the case for Sandy; soil moisture is near average over most of the mid-Atlantic, and is in the lowest 30th percentile in recorded history over much of Delaware and Southeastern Maryland (Figure 6.) One region of possible concern is the Susquehanna River Valley in Eastern Pennsylvania, where soil moisture is in the 70th percentile, and river levels are in the 76th - 90th percentile. This area is currently expected to receive 2 - 4 inches of rain (Figure 4), which is not enough to cause catastrophic flooding like occurred for Hurricane Irene. However, it is quite possible that the axis of heaviest rains will shift northwards from this forecast. I expect that river flooding from Sandy will cause less than $1 billion in damage.

Links
To find out if you need to evacuate, please contact your local emergency management office. They will have the latest information. People living in New York City can find their evacuation zone here or use this map. FEMA has information on preparing for hurricanes.

People with disabilities and caregivers seeking information on accessible shelter and transportation can contact portlight.org

Our Weather Historian, Christopher C. Burt, has an excellent post on Late Season Tropical Storms that have affected the U.S. north of Hatteras. He also has a post, Historic Hurricanes from New Jersey to New England.

Joe Romm at climateprogress.org has a thoughtful piece called, How Does Global Warming Make Hurricanes Like Irene More Destructive?

For those of you wanting to know your odds of receiving hurricane force or tropical storm force winds, I recommend the NHC wind probability product.

Wunderground has detailed storm surge maps for the U.S. coast.

The National Hurricane Center's Interactive Storm Surge RIsk Map, which allows one to pick a particular Category hurricane and zoom in, is a good source of storm surge risk information.

Research storm surge model run by SUNY Stonybrook for New York City.

Climate Central has a nice satellite image showing which parts of New York Harbor are below five feet in elevation.
Five-minute video of Hurricane Sandy on Thursday as seen from the International Space Station.

I'll probably leave this post up until late morning Sunday, unless there are some significant changes to report.

Jeff Masters

Hurricane

Updated: 11:51 PM GMT on October 27, 2012

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Sandy remains a hurricane, slowly leaving the Bahamas

By: angelafritz , 9:28 PM GMT on October 26, 2012

Reuters reports that the death toll from Sandy in the Caribbean is now up to 41 people as Hurricane Sandy continues its track toward the U.S. East Coast this afternoon, slowly leaving the Bahamas. States of Emergency have been declared in North Carolina, Virginia, Maryland, and New York. The hurricane is just barely still a Category 1 with surface winds of 75 mph and a minimum central pressure of 971 mb. Ocean buoys off the coasts of Florida and the Carolinas are recording sustained winds of around 45 mph this afternoon, with gusts steadily increasing and now up to 60 mph. Sandy's rainfall, which is limited to the north and northeast parts of the storm, is reaching eastern Florida, though most of it is staying offshore.

Satellite loops show an asymmetric Sandy, with almost all of the thunderstorm activity on its north side. The hurricane still has a very clear center of surface circulation which you can see on visible and infrared loops. Though the hurricane is leaving the influence of an upper level low pressure area over western Cuba, water vapor imagery shows a large area of dry air being pulled into the storm from the south, which is leading to the lack of thunderstorm activity and contributing to the weakening that Sandy is experiencing right now. The hurricane's tropical storm-force winds now extend 240 miles from the center, and could grow to 400 miles from the center by the time it reaches the East Coast.


Figure 1. Visible/infrared satellite image of Sandy as it leaves the Bahamas this afternoon. The mid-latitude trough, which Sandy will interact with over the next few days, is seen approaching from the northwest. The cold front associated with this trough is draped from upstate New York south to Louisiana, and appears as a line of clouds draped across the Midwest and South in this image.

Forecast For Hurricane Sandy

As a tropical cyclone approaches land, the worst storm surge is almost always where the winds are blowing from ocean to shore, where the wind pushes the water toward and onto the shore. In the case of Sandy's potential track, this region is on the north side of the center. In this morning's GFS scenario, Sandy's center passes over eastern Long Island, Connecticut, and Rhode Island. This would result in the highest surge north of New York City: Rhode Island, Massachusetts, New Hampshire, and possibly Maine. The ECMWF forecast from this morning is a bit further to the south. It's suggesting Sandy's center will meet land in New Jersey. This scenario opens up New York City, Long Island, Connecticut, Rhode Island, and southern coastal Mass. to the largest surge. In general, the places that will avoid the largest storm surge are those that are south of where the center of the storm makes landfall. The National Hurricane Center's forecast is similar to the ECMWF, but most importantly, its forecast is also to not focus on the exact point of landfall because of the size of the storm, and that widespread impact is expected.

The Mid-Atlantic and Northeast coasts should be prepared for a storm surge no matter their exact location. A large portion of the coast will feel the impact of up to 60 mph winds and heavy rain. According to the most recent H*Wind analysis from the Hurricane Research Division is that storm surge has a destructive potential of 4.8 out of 6.0, which is a slight increase from previous analyses. Wind damage potential is holding steady around 2.3 out of 6.0. NOAA's HPC is forecasting rainfall totals of 5 to 10 inches in the Mid-Atlantic and Northeast, and possibly more in coastal locations close to the core of the storm. Widespread power outages from Maine south to Virginia are likely, due to the combination of long-lived gale-force winds, leaves on trees, and rain that will moisten the soil and possibly increase the chances of falling trees. Snow in the Appalachians is also possible as the intense moisture meets the cold air being pulled south by the mid-latitude trough.


Figure 2. Departure of sea surface temperature from average for the Atlantic shows a large area of unusually warm waters up to 9°F above average off the U.S. mid-Atlantic coast.

Sandy to feed off near-record warm waters off the mid-Atlantic coast
During September 2012, ocean temperatures off the mid-Atlantic coast in the 5x10° latitude-longitude box between 35 - 40°N, 65 - 75° W were 2.3°F (1.3°C) above average, according to the UK Met Office. This is the 2nd greatest departure from average for ocean temperatures in this region since reliable ocean temperature measurements began over a century ago (all-time record: 2.0°C above average in September 1947.) These unusually warm waters have persisted into October, and will enable Sandy to pull more energy from the ocean than a typical October hurricane. The warm waters will also help increase Sandy's rains, since more water vapor will evaporate into the air from a warm ocean. I expect Sandy will dump the heaviest October rains on record over a large swath of the mid-Atlantic and New England.

Hurricane rains and climate change
Hurricanes are expected to dump 20% more rain in their cores by the year 2100, according to modeling studies (Knutson et al., 2010). This occurs since a warmer atmosphere holds more water vapor, which can then condense into heavier rains. Furthermore, the condensation process releases heat energy (latent heat), which invigorates the storm, making its updrafts stronger and creating even more rain. We may already be seeing an increase in rainfall from hurricanes due to a warmer atmosphere. A 2010 study by Kunkel et al. "Recent increases in U.S. heavy precipitation associated with tropical cyclones", found that although there is no evidence for a long-term increase in North American mainland land-falling tropical cyclones (which include both hurricanes and tropical storms), the number of heavy precipitation events, defined as 1-in-5-year events, more than doubled between 1994 - 2008, compared to the long-term average from 1895 - 2008. As I discussed in a 2011 post "Tropical Storm Lee's flood in Binghamton: was global warming the final straw?", an increase in heavy precipitation events in the 21st Century due to climate change is going to be a big problem for a flood control system designed for the 20th Century's climate.


Figure 3. Time series of the 15-yr running average (plotted at the end point of the 15-yr blocks) of the tropical cyclone Heavy Precipitation Index (red) and the associated 15-yr total of U.S. landfalling hurricanes from Atlantic HURDAT hurricane data base, from 1895 - 2008 (blue). Note the steep rise in heavy precipitation events from tropical cyclones over the past 20 years, which has not been accompanied by a corresponding increase in landfalling hurricanes. Image credit: Kunkel et al., 2010, Geophysical Research Letters.

Angela Fritz and Jeff Masters

Hurricane

Updated: 1:08 AM GMT on October 27, 2012

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Hurricane Sandy kills 21, heads towards the U.S.

By: JeffMasters, 3:34 PM GMT on October 26, 2012

Hurricane Sandy plowed through the Bahama Islands as a powerful Category 2 hurricane with 105 mph winds yesterday, but high wind shear has destroyed the hurricane's eyewall and reduced Sandy to Category 1 strength, with 80 mph winds. Satellite loops show that the low-level center of Sandy is now exposed to view, with most of the storm's heavy thunderstorm activity pushed to the north side by strong upper level winds from the south-southwest. Cuban state media is reporting that eleven people were killed on Cuba, and damage was heavy, with thousands of homes damaged or destroyed. It was Cuba's deadliest hurricane since Category 5 Hurricane Dennis killed sixteen people in 2005. Damage was also substantial on Jamaica, where one person was killed, and power was knocked out for 70% of the island's residents. Nine deaths have been reported in Haiti due to flooding, and heavy rains from Sandy continue there this morning.


Figure 1. Morning satellite image of Sandy.

Forecast for Sandy
Wind shear is expected to remain a high 30 - 55 knots for the next four days, as Sandy interacts with a trough of low pressure to its west. The high shear should keep Sandy from intensifying the way most hurricanes do--by pulling heat energy out of the ocean. However, the trough approaching from the west will inject into Sandy what is called "baroclinic" energy--the energy one can derive from the atmosphere when warm and cold air masses lie in close proximity to each other. This transition will reduce the hurricane's peak winds, but strong winds will spread out over a wider area of ocean. This will increase the total amount of wind energy of the storm, keeping the storm surge threat high. This large wind field will likely drive a storm surge of 3 - 6 feet on Monday and Tuesday to the right of where the center makes landfall, on the mid-Atlantic or New York coasts. These storm surge heights will be among the highest ever recorded along the affected coasts, and will have the potential to cause hundreds of millions of dollars in damage.

The latest set of 00Z (8 pm EDT) and 06Z (2 am EDT) computer model runs still have wide differences in the timing and landfall location for Sandy. The ECMWF has been very consistent in its handling of Sandy, and continues to predict that Sandy will hit Delaware or Maryland on Monday afternoon--basically the same forecast it has had for three days. Our other top model for forecasting hurricane tracks, the GFS, has been more inconsistent, and predicts a landfall on Long Island, New York on Tuesday afternoon.


Figure 2. Predicted 5-day precipitation total for Hurricane Sandy as forecast by the 2 am EDT October 26, 2012 run of the HWRF model. A wide swath of 8 - 16" of rain (dark yellow colors) is predicted for North Carolina, Virginia, and Maryland. Image credit: Morris Bender, NOAA/GFDL.


Figure 3. A customized version of the Weather Research and Forecasting (WRF) Model run by Weather Decision Technologies (http://www.wdtinc.com/) computed the precipitation expected to fall from Sandy over the 5-day period ending at 5 am EDT Tuesday, October 30. Using the predicted precipitation, METSTAT, Inc. (http://www.metstat.com) computed the Extreme Precipitation Index (EPI) to represent how unusual the storms' precipitation is expected to be in terms of an average recurrence interval ("return period"). Several swaths of 24-hour rainfall amounts that one would expect to recur on average every 100 years (red through pink colors) are predicted. The recurrence interval statistics were computed based on precipitation frequency estimates from NOAA Atlas 14 Volume 2, published in 2004 (http://dipper.nws.noaa.gov/hdsc/pfds/.) Metstat does not supply the forecast EPIs for free, anyone can monitor the real-time EPI analysis (observed) at: http://metstat.com/solutions/extreme-precipitation-index-analysis/

Severe impacts likely in the U.S.
Sandy's expected landfall along the mid-Atlantic coast is likely to be a billion-dollar disaster. Sandy should bring sustained winds of 50 - 60 mph with gusts over hurricane force to a large section of coast, and the storm may be moving slowly enough that these conditions will persist for a full 24 hours. With most of the trees still in leaf, there will be widespread power outages due to downed trees. Sandy is expected to have tropical storm-force winds that extend out more than 400 miles from the center, which will drive a much larger storm surge than its winds would ordinarily suggest. The latest H*Wind analysis from NOAA's Hurricane Research Division put the destructive potential of Sandy's winds at 2.1 on a scale of 0 to 6, and the destructive potential of the storm surge much higher, at 4.2 on a scale of 0 to 6. The full moon is on Monday, which means astronomical tides will be at their peak for the month, increasing potential storm surge flooding. With Sandy's strongest winds expected to last at least 12 hours near the time of landfall, the peak storm surge will affect the coast for at least one high tide cycle, and possibly two. This will greatly increase the potential for storm surge damage and coastal erosion. If Sandy hits Long Island, as the GFS model predicts, the storm surge will be capable of over-topping the flood walls in Manhattan and flooding portions of the New York City subway system. Fresh water flooding from heavy rains is also a huge concern. Rainfall amounts of 5 - 10 inches will occur over several hundred mile-long swath of coast, with isolated amounts of 15 inches possible. Fortunately, soils are dry and river levels are low over most of the threatened region, which should keep Sandy's river flooding lower than that experienced last year during Hurricane Irene. Nevertheless, Sandy is shaping up to be a historic storm for the mid-Atlantic and Northeast U.S. that has few precedents.

Jeff Masters

Hurricane

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Hurricane Sandy remains a Category 2, continues on its track toward the East Coast

By: angelafritz , 9:48 PM GMT on October 25, 2012

Hurricane Sandy is tracking north through the Bahamas this afternoon as a Category 2 hurricane. Maximum wind speeds in the hurricane are 105 mph, with a minimum central pressure of 963 mb. Sandy's center is moving through the eastern Bahamas, about 100 miles southeast of Nassau. The hurricane's eye is still not apparent on satellite nor was it clear in the data from today's Hurricane Hunter mission. Gusts in Nassau have reached 39 mph so far today as the hurricane approaches from the south. Buoys west of Nassau have been recording surface winds up to 39 mph, as well. On Abaco Island, just over an inch of rain has fallen today, and almost an inch of rain has fallen in Miami, where rain started last night.

Sandy's appearance on satellite is a bit ragged this afternoon as it approaches very high wind shear (40-50 knots). The hurricane is obviously already undergoing structural changes this afternoon, caused in part by an upper level low over western Cuba. This low is prohibiting Sandy's outflow on the west side, and as a result, the storm appears asymmetrical with a large area of outflow and circulation to the north, and only a tail of circulation on the southeast of the hurricane. Visually, Sandy is a huge storm. Based on clouds alone, Sandy stretches from Jacksonville, Florida, east to Bermuda, and south to the southern Caribbean Sea. Sandy's radius of outer closed isobar is 350 miles, though tropical storm-force winds only extend around 200 miles from the center.


Figure 1. High resolution MODIS visible satellite imagery of Hurricane Sandy early this morning.

Forecast For Hurricane Sandy
As Sandy moves north, it will grow larger and the hurricane's energy will spread out even more, which will lead to a slight decrease in maximum wind speed. Models agree on this steady decrease in intensity over the next few days, though beyond that, the intensity forecast is still in question since Sandy could begin to gain non-tropical energy as it transitions into a non-tropical storm. The track through Saturday evening remains well understood by the models: Sandy will move north with a slight turn to the west before being yanked north-northeast again by the approaching mid-latitude trough. It's at this point in the forecast that the models diverge, though all but the HWRF are forecasting the unfortunate turn back to the west and into the Northeast U.S. Furthest south along the East Coast is the ECMWF, which forecasts a turn into Maryland/North Carolina on Monday. The GFS forecast is a bit further north than the ECMWF, pushing Sandy onshore near Long Island late Tuesday night. However, this represents a large shift south from earlier GFS runs, and puts the Mid-Atlantic into play more than it was in earlier forecasts. The forecast from the National Hurricane Center appears to be a compromise between the ECMWF and the GFS. The Center is forecasting Sandy to approach the New Jersey coast on Tuesday afternoon.

There are many questions surrounding this hurricane and its forecast, but I find it important to convey that Sandy's impacts will be widespread, no matter the location of "landfall." Risk to the Mid-Atlantic seems higher this afternoon, and as Jeff noted in his morning blog, Sandy will be a very large and possibly non-tropical storm as it approaches the coast, with gale-force winds extending up to 300 miles from its center. This increases the probability of storm surge extending far from the center of the storm, which, combined with the timing of a full moon tide, is a big concern, along with freshwater and river flooding from heavy, extended periods of rain.

Angela


Figure 2. Today's "extra" 18Z (2pm EDT) weather balloon launched from the Peachtree City office of the National Weather Service. The National Weather Service is launching extra weather balloons all over the country to improve the quality of forecasts as Sandy approaches. Thanks to NWS Meteorologist Alex Gibbs for snapping this shot just before launch!

Hurricane

Updated: 10:05 PM GMT on October 25, 2012

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Sandy slams Cuba, intensifies over the Bahamas

By: JeffMasters, 2:39 PM GMT on October 25, 2012

Hurricane Sandy shrugged off wind shear of 20 knots and passage over the southeastern tip of Jamaica yesterday afternoon, explosively deepening into a top-end Category 2 hurricane with 110 mph winds. Sandy made landfall in Southeastern Cuba around 1 am EDT this morning near Santiago de Cuba, which experienced sustained winds of 78 mph, gusting to 114 mph. Winds at Guantanamo Bay, Cuba peaked at 58 mph, gusting to 72 mph, at 3 am local time this morning, and the base received 3.51" of rain from Sandy as of 8 am EDT this morning. Punta Lucrecia, Cuba on the north coast of Cuba received 8.42" of rain from Sandy as of 8 am EDT. Cuban state media is reporting that one person was killed on Cuba, and damage was heavy, with thousands of homes damaged or destroyed. Damage was also substantial on Jamaica, where one person was killed, and power was knocked out for 70% of the island's residents. One death has been reported in Haiti due to flooding.

Sandy survived the crossing of Cuba's high mountains with its inner core relatively intact, and is now re-intensifying over the warm waters of the Central Bahama Islands. The latest 9:30 am center fix from the Hurricane Hunters found a central pressure of 965 mb, down 3 mb in 1.5 hours. The eye is intermittently visible on satellite loops, and Sandy appears to be holding its own against the high 30 knots of wind shear affecting it.


Figure 1. Hurricane Sandy approaching landfall in Southeast Cuba as seen by Cuban radar at 10:15 pm EDT Wednesday, October 24, 2012. Image credit: Cuban Institute of Meteorology.


Figure 2. Morning satellite image of Sandy.

Forecast for Sandy
Wind shear is expected to rise to 40 - 55 knots by Friday, as Sandy interacts with a trough of low pressure to its west. The high shear should disrupt Sandy's inner core and reduce the maximum winds. However, the trough will also inject energy into Sandy, and the hurricane's winds will spread out over a wider area of ocean, keeping the storm surge threat high. This large wind field will likely drive a storm surge of 5 - 8 feet in the Bahamas. Sandy will make its closest pass by Nassau around 8 am EDT Friday.

The latest set of 00Z (8 pm EDT) and 06Z (2 am EDT) computer model runs are in substantial agreement for the next 3 days, but Sandy's future is as clear as mud after that. Sandy will continue to punish the Bahamas today and Friday, as it tracks north to north-northwest. Sandy will probably come close enough to the Southeast U.S. on Saturday afternoon to spread heavy rains to the coasts of South Carolina and North Carolina. However, the 4 - 6 day computer model forecasts for Sunday - Tuesday diverge widely. The GFS model, which has been one of our two top models for predicting hurricane tracks the past two years, has been very inconsistent with its handling of Sandy. Runs of the GFS model done 6 hours apart, at 8 pm last night and 2 am EDT this morning, were 300 miles apart in their position for Sandy on Tuesday, with the latest run predicting a landfall in Maine on Wednesday morning. On the other hand, the ECMWF model, our other top model for predicting hurricane tracks, has been very consistent in its handling of Sandy. The ECMWF model has Sandy hitting Delaware on Monday afternoon, the same forecast it has had for three consecutive runs. The other models tend to follow one extreme or the other, and NHC is picking a solution somewhere in the middle of these two extremes. An extra set of balloon-borne radiosondes is going to be launched at 2 pm EDT Thursday all across the U.S., which should help this evening's model runs. Extra radiosondes will be launched every 6 hours through Saturday afternoon.


Figure 3. This Maximum Water Depth storm surge image for the Bahamas shows the worst-case inundation scenarios for a Category 2 hurricane with 105 mph winds, as predicted using dozens of runs of NOAA's SLOSH model. For example, if you are inland at an elevation of ten feet above mean sea level, and the combined storm surge and tide (the "storm tide") is fifteen feet at your location, the water depth image will show five feet of inundation. No single storm will be able to cause the level of flooding depicted in this image. Sandy's maximum storm surge may reach levels portrayed in this image for some islands in the Bahamas. See wunderground's storm surge pages for more storm surge info.

The Northeast U.S. scenario
If Sandy makes landfall farther to the north near Maine and Nova Scotia, heavy rains will be the main threat, since the cold waters will weaken the storm significantly before landfall. The trees have fewer leaves farther to the north, which will reduce the amount of tree damage and power failures compared to a more southerly track. However, given that ocean temperatures along the Northeast U.S. coast are about 5°F above average, there will be an unusually large amount of water vapor available to make heavy rain. If the trough of low pressure approaching the East Coast taps into the large reservoir of cold air over Canada and pulls down a significant amount of Arctic air, the potential exists for the unusually moist air from Sandy to collide with this cold air from Canada and unleash the heaviest October rains ever recorded in the Northeast U.S., Nova Scotia, and New Brunswick. This Northeast U.S. scenario would probably cause damages near $100 million dollars.

The mid-Atlantic U.S. scenario
Landfall Monday along the mid-Atlantic coast on Monday, as predicted by the ECMWF and NOGAPS models, would likely be a billion-dollar disaster. In this scenario, Sandy would be able to bring sustained winds near hurricane force over a wide stretch of heavily populated coast, causing massive power outages, as trees still in leaf fall and take out power lines. Sandy is expected to have tropical storm-force winds that extend out more than 300 miles from the center, which will drive a much larger storm surge than its winds would ordinarily suggest. The full moon is on Monday, which means astronomical tides will be at their peak for the month, increasing potential storm surge flooding. Fresh water flooding from heavy rains would also be a huge concern. Given the ECMWF's consistent handling of Sandy, I believe this mid-Atlantic scenario has a higher probability of occurring than the Northeast U.S. scenario. However, it is likely that the models are overdoing the strength of Sandy at landfall. The models have trouble handling the transition from tropical storm to extratropical storm in these type of situations, and I expect that the 940 mb central pressure of Sandy predicted at landfall Monday in Delaware by the ECMWF model is substantially overdone.

Jeff Masters

Hurricane

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Hurricane Sandy hits Jamaica, dumps heavy rains on Haiti

By: JeffMasters, 8:54 PM GMT on October 24, 2012

Hurricane Sandy hit the southeastern tip of Jamaica near 3:20 pm EDT this afternoon, as a Category 1 hurricane with 80 mph winds and a 973 mb pressure. According to NOAA's Historical Hurricane Tracks website, Sandy is the thirteenth hurricane to make a direct hit on the island, and the first since Hurricane Gilbert of 1988. Kingston, Jamaica recorded sustained winds of 44 mph and a pressure of 972 mb in the west eyewall of Sandy at 4 pm EDT. The eastern tip of Jamaica will see the strongest winds of the right-front quadrant and the heaviest damage, though. A distorted eye is apparent on visible satellite loops, but Sandy is showing only minor disruption to its inner core structure as a result of hitting Jamaica. According to the Jamaica Observer, "Alligator Pond [in St Elizabeth] was inundated with the high waves that came ashore. We are now getting reports of impacts out in St. Catherine, Portland and St. Thomas as the ground becomes saturated. We are now seeing where light poles are toppling and landslides being reported and roadway being flooded to the point where there is impeded access in east St. Thomas." Heavy rains from Sandy are falling in Haiti. A NOAA forecast based on microwave satellite data predicts 12 inches of rain for the tip of Haiti's southwestern Peninsula, which will likely cause life-threatening flash flooding. Fortunately, much lighter rainfall amounts are predicted for the capital of Port-au-Prince, where 350,000 people still live in the open under tarps in the wake of the January 2010 earthquake. In August, flooding from Hurricane Isaac killed at least 29 people in Haiti.


Figure 1. Hurricane Sandy over Jamaica. The large 55-mile diameter eye hit the island at 3:20 pm EDT, and crossed over the eastern tip of the island. The eye has been distorted into an odd triangular shape, due to interaction with the land area of Jamaica.


Figure 2. Predicted 24-hour rain amounts from Hurricane Sandy for the period ending at 8 am EDT Thursday, October 25, 2012. The prediction is based on microwave satellite data of precipitation. Image credit: NOAA/NESDIS.

Near-term forecast for Sandy
Sandy doesn't have much time over water before it makes landfall on the southeastern coast of Cuba near 10 pm EDT this Wednesday night, and the strongest the storm is likely to be then is a 90 mph Category 1. Passage over the rugged terrain of Cuba should weaken Sandy's winds by 20 - 30 mph, and will likely destroy the hurricane's eyewall. It will be difficult for the storm to rebuild its eyewall and regain all of that lost strength, in the face of the high wind shear of 20 - 30 knots it will encounter Thursday and Friday. However, the loss of the eyewall will cause Sandy's radius of tropical storm-force winds to expand, spreading out the winds over a wider area of ocean, and increasing the storm surge threat. This large wind field will likely drive a storm surge of 5 - 8 feet in the Bahamas, which is more characteristic of a storm with winds 20 mph higher. I expect that Sandy will be a 65 - 70 mph tropical storm as it traverses the Bahamas, and the storm will make its closest pass by Nassau around 10 pm EDT Thursday.


Figure 3. This Maximum Water Depth storm surge image for the Bahamas shows the worst-case inundation scenarios for a Category 1 hurricane with 85 mph winds, as predicted using dozens of runs of NOAA's SLOSH model. For example, if you are inland at an elevation of ten feet above mean sea level, and the combined storm surge and tide (the "storm tide") is fifteen feet at your location, the water depth image will show five feet of inundation. No single storm will be able to cause the level of flooding depicted in this image. Sandy's maximum storm surge may reach levels portrayed in this image for some islands in the Bahamas. See wunderground's storm surge pages for more storm surge info.

Sandy: a potential billion-dollar storm for the mid-Atlantic, New England, and Canada
The latest set of 12Z (8 am EDT) model runs are in, and they portray an increased risk to the U.S. and Canadian East Coasts for early next week. The GFS model, which had been showing that Sandy would head to the northeast out to sea, now has changed its tune, and predicts that Sandy will double back and hit Maine on Tuesday evening. The ECMWF model, which has been very consistent in its handling of Sandy, now has the storm hitting Delaware on Monday afternoon. These models are predicting that Sandy will get caught up by the trough approaching the Eastern U.S., which will inject a large amount of energy into the storm, converting it to a powerful subtropical storm with a central pressure below 960 mb and sustained winds of 60 - 70 mph. Winds of this strength would likely cause massive power outages, as trees still in leaf take out power lines. Also of great concern are Sandy's rains. Given that ocean temperatures along the Northeast U.S. coast are about 5°F above average, there will be an unusually large amount of water vapor available to make heavy rain. If the trough of low pressure approaching the East Coast taps into the large reservoir of cold air over Canada and pulls down a significant amount of Arctic air, as predicted, the potential exists for the unusually moist air from Sandy to collide with this cold air from Canada and unleash the heaviest October rains ever recorded in the Northeast U.S. Another huge concern is storm surge flooding. Sandy is expected to have tropical storm-force winds that extend out more than 300 miles from the center, which will drive a much larger storm surge than its winds would ordinarily suggest. The full moon is on Monday, which means astronomical tides will be at their peak for the month, increasing potential storm surge flooding.

There remains a lot of model uncertainty on where Sandy might go, and I still give a 30% chance that the storm will have a minimal impact on the U.S. An extra set of balloon-borne radiosondes is going to be launched at 2 pm EDT on Thursday all across the U.S., which should help tomorrow evening's model runs make better forecasts of where Sandy might go. Extra radiosondes will be launched every 6 hours through Saturday afternoon.

Jeff Masters

Hurricane

Updated: 9:49 PM GMT on October 24, 2012

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Hurricane Sandy pounding Jamaica, may hit U.S. this weekend; TS Tony forms

By: JeffMasters, 2:21 PM GMT on October 24, 2012

Hurricane warnings are flying for Jamaica and Eastern Cuba, as an intensifying Hurricane Sandy plows north-northeast at 13 mph towards landfall. The Hurricane Hunters are in the storm, and measured surface winds of hurricane strength--75 to 80 mph--in the storm's northeast quadrant near 9:25 am EDT. Sandy's pressure at the time of the 9:28 am center fix was 973 mb, and the temperature in the eye had warmed 2°C since the 7:48 am fix, a sign of strengthening. Intermittent rain squalls from Sandy have been affecting Jamaica since Monday night, and Kingston, Jamaica has picked up 2.12" of rain from Sandy as of 9 am EDT. Winds in Jamaica have been below 20 mph as of 10 am EDT, but will start to rise quickly in the next few hours. The Hurricane Hunters found a large 55 mile-diameter eye that was open to the WNW this morning, and it is likely that Kingston will receive high winds of 55 - 65 mph from the western eyewall, which will cause considerable damage to Jamaica's capital. The eastern tip of Jamaica will likely see the eye pass overhead, and will receive the strongest winds. The eye is beginning to appear on visible satellite loops, and Sandy is showing an increasing degree of organization as it closes in on Jamaica. Sandy is the tenth hurricane of the 2012 hurricane season, which is now tied for eighth place for most hurricanes in a year since record keeping began in 1851.


Figure 1. Morning microwave satellite image of Tropical Storm Sandy taken at 8:45 am EDT. The large 55-mile diameter eye was just south of Jamaica. Image credit: Navy Research Lab, Monterey.

Near-term forecast for Sandy
Wind shear is forecast to be in the moderate range and ocean temperatures will be a warm 28°C through Thursday morning, which will favor intensification. However, Sandy doesn't have much time left over water before it encounters the high mountains of Jamaica this afternoon, which should interrupt the intensification process. The strongest Sandy is likely to be at landfall in Jamaica is a 90 mph Category 1 hurricanes. After encountering Jamaica, Sandy won't have time to re-organize much before making landfall in Eastern Cuba near 10 pm EDT tonight, and the strongest the storm is likely to be then is a 90 mph Category 1. Passage over the rugged terrain of Cuba should weaken Sandy's winds by 20 - 30 mph, and it will be difficult for the storm to regain all of that lost strength in the face of the high wind shear of 20 - 30 knots it will encounter Thursday and Friday. I expect that Sandy will be a 60 - 70 mph tropical storm as it traverses the Bahamas.


Figure 2. MODIS satellite image of Tropical Storm Sandy taken at 11:45 am EDT Tuesday, October 23, 2012. At the time, Sandy had top winds of 50 mph. Image credit: NASA.

Sandy: a potential billion-dollar storm for the mid-Atlantic and New England
On Friday, a very complicated meteorological situation unfolds, as Sandy interacts with a trough of low pressure approaching the U.S. East Coast and trough of low pressure over the Central Atlantic. The Central Atlantic trough may be strong enough to pull Sandy northeastwards, out to sea, as predicted by the official NHC forecast, and the 06Z GFS, 00Z UKMET, 00Z Canadian, and 06Z HWRF models (00Z is 8 pm EDT, and 06Z is 2 am EDT.) However, an alternative solution, shown by the 00Z ECMWF, 06Z GFDL, and 06Z NOGAPS models, is for Sandy to get caught up by the trough approaching the Eastern U.S., which will inject a large amount of energy into Sandy, converting it to a powerful subtropical storm that hits the mid-Atlantic or New England early next week with a central pressure below 960 mb and sustained winds of 60 - 70 mph. Such a storm would likely cause massive power outages and over a billion dollars in damage, as trees still in leaf take out power grids, and heavy rains and coastal storm surges create damaging flooding. The full moon is on Monday, which means astronomical tides will be at their peak for the month, increasing potential storm surge flooding. A similar meteorological situation occurred in October 1991, when Hurricane Grace became absorbed by a Nor'easter, becoming the so-called "Perfect Storm" that killed 13 people and did over $200 million in damage in the Northeast U.S.


Figure 3. The Wednesday morning 06Z (2 am EDT) run of the GFS model was done 20 times at lower resolution with slightly varying initial conditions of temperature, pressure, and moisture to generate an ensemble of forecast tracks for Sandy (pink lines). These forecasts show substantial uncertainty in Sandy's path after Friday, with a minority of the forecasts taking Sandy to the northeast, out to sea, and the majority now predicting a landfall in the Northeast or mid-Atlantic states of the U.S. The white line shows the official GFS forecast, run at higher resolution.

When might Sandy arrive in the mid-Atlantic and New England?
The models vary significantly in their predictions of when Sandy might arrive along the U.S. coast. The 06Z NOGAPS model predicts Sandy's heavy rains will arrive on North Carolina's Outer Banks on Saturday, then spread into the mid-Atlantic and New England on Sunday. The 00Z ECMWF model predicts that Sandy's rains won't affect North Carolina until Sunday, with the storm making landfall in New Jersey on Monday night. The GFDL model is in-between these extremes, taking Sandy ashore in Delaware on Monday morning. The trough of low pressure that Sandy will be interacting with just moved ashore over the Western U.S. this morning, and got sampled by the 12Z (8 am EDT) set of land-based balloon-borne radiosondes for the first time. One of the reasons the models have been in such poor agreement on the long-term fate of Sandy is that the strength of this trough has not been very well known, since it has been over the ocean where we have limited data. Now that the trough is over land, it will be better sampled, and the next set of 12Z model runs, due out this afternoon between 2 pm - 4pm EDT, will hopefully begin to converge on a common solution. I'll have an update this afternoon once the 12Z model runs are in.


Figure 4. Morning satellite image of Tropical Storm Tony.

Tropical Storm Tony forms in the middle Atlantic
Tropical Storm Tony formed Tuesday night in the middle Atlantic, becoming the nineteenth named storm of this very busy 2012 Atlantic hurricane season. Tony has a modest area of heavy thunderstorms, as seen on visible satellite images, but is battling dry air , wind shear, and ocean temperatures that have fallen below 26°C. Tony will not threaten any land areas, and will likely be dead by Thursday night.

Tony's place in history
Tony is the Nineteenth named storm of the 2012 Atlantic hurricane season, tying this year with 1887, 1995, 2010, and 2011 for third busiest Atlantic season since the HURDAT historical data base began in 1851. With five more weeks left before the November 30 end of hurricane season, 2012 is likely to move into second place for most named storms before the year is out, as all six prior Atlantic hurricane seasons with nineteen or more named storms have had at least one named storm form after October 24. Here, then, is a list of the seven busiest Atlantic hurricane seasons on record:

2005 (28 named storms)
1933 (20 named storms, according to a new re-analysis)
2012 (19 named storms)
1887 (19 named storms)
2010 (19 named storms)
2011 (19 named storms)
1995 (19 named storms)

It's pretty remarkable that we've now had three straight years with nineteen named storms in the Atlantic. But how many of these storms might not have been counted in the pre-satellite era (before 1960)? Here's a list of weak and short-lived storms from 2010 - 2012 that stayed far out sea, and would likely have gone unnoticed in the pre-satellite era:

2012:
Tropical Storm Joyce
Tropical Storm Oscar
Tropical Storm Tony

2011:
Tropical Storm Jose
Tropical Storm Franklin

2010:
Tropical Storm Gaston

Even if we correct for the possible over-count of approximately two named storms per year during the 2010, 2011, and 2012 hurricane seasons, compared to the pre-satellite era, there is nothing in the HURDAT data base that compares to the type of activity we've seen the past three years. One likely contributor to the unusual string of active years is the fact hurricane season has gotten longer, perhaps due to warming ocean temperatures. I discussed in a 2008 blog post that Dr. Jim Kossin of the University of Wisconsin published a 2008 paper in Geophysical Research Letters titled, "Is the North Atlantic hurricane season getting longer?" He concluded that yes, there is a "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high".

Jeff Masters

Hurricane

Updated: 3:34 PM GMT on October 24, 2012

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Sandy intensifying, headed towards Jamaica

By: JeffMasters, 2:49 PM GMT on October 23, 2012

Tropical Storm Sandy is on the move northwards towards Jamaica, and is slowly intensifying. The Hurricane Hunters are in the storm, and measured surface winds near 50 mph in the storm's northeast quadrant at 9 am EDT. The latest center fix, taken at 10:20 am EDT, found that Sandy's pressure had fallen 2 mb since early this morning, to 995 mb. Intermittent rain squalls from Sandy have been affecting Jamaica since Monday night, and Kingston, Jamaica has picked up 0.82" of rain from Sandy as of 9 am EDT. and Sandy is over very warm waters of 29.5°C, is in an unusually moist environment with relative humidities above 80%, and is experiencing light wind shear of 5 - 10 knots. These conditions are very favorable for intensification, and Sandy's heavy thunderstorms have increased in areal extent, intensity, and organization this morning, as seen on satellite loops.


Figure 1. Morning satellite image of Tropical Storm Sandy.

Sandy a potential threat to New England
Wind shear is forecast to be in the low to moderate range, 5 - 20 knots, through Thursday morning. This should allow continued development of Sandy, and rapid development is possible. The 8 am EDT SHIPS model forecast predicted a 62% chance that Sandy's winds would increase by 30 mph over a 24-hour period. However, the Hurricane Hunters found this morning that the center at 5,000 feet was displaced 7 miles from the surface center, and there was no indication that Sandy was building an eyewall, so I expect that the earliest Sandy could become a hurricane is Wednesday morning. The 5 am EDT NHC Wind Probability Forecast gave a 49% chance that Sandy would be a hurricane by 2 pm EDT Wednesday, when the center should be close to Jamaica. Wind shear will rise to a high 25 - 30 knots by Thursday and the storm will have to cross the rugged terrain of Cuba, which should weaken Sandy's winds by 20 - 30 mph. By Friday, Sandy should be over warm waters in the Central Bahamas, but only modest re-intensification by 10 - 20 mph should occur, due to high wind shear. At that point, a very complicated meteorological situation unfolds, as Sandy interacts with a trough of low pressure approaching the U.S. East Coast. The trough may steer Sandy northeastwards, out to sea, as predicted by the GFS, HWRF, and GFDL models. However, an alternative solution, shown by the ECMWF and NOGAPS models, is for the trough to inject a large amount of energy into Sandy, converting it to a powerful subtropical storm that hits New England early next week with a central pressure of 948 mb and winds near hurricane-force. The ECMWF and NOGAPS models are off by a full day in their predictions of when the storm would arrive, with the 06Z NOGAPS model predicting Sandy's heavy rains will arrive on North Carolina's Outer Banks on Sunday, then spread into the mid-Atlantic and New England on Sunday. The 00Z ECMWF model forecast predicts that Sandy will arrive in New England on Monday night. Stay tuned.


Figure 2. The Tuesday morning 06Z (2 am EDT) run of the GFS model was done 20 times at lower resolution with slightly varying initial conditions of temperature, pressure, and moisture to generate an ensemble of forecast tracks for Sandy (pink lines). These forecasts show substantial uncertainty in Sandy's path after Friday, with the majority of the forecasts taking Sandy to the northeast, out to sea, but a substantial number predicting a landfall in the Northeast or mid-Atlantic states of the U.S. The white line shows the official GFS forecast, run at higher resolution.


Figure 3. Morning satellite image of Tropical Depression Nineteen.

Tropical Depression Nineteen in the middle Atlantic
There has been little change to Tropical Depression Nineteen since it formed Monday in the middle Atlantic. TD 19 has a modest area of heavy thunderstorms, as seen on visible satellite images, and dry air from an upper-level low pressure system on its west side is slowing development. TD 19 is moving north-northeast at 15 mph, and has moved over waters that are 27°C, a full degree cooler what the storm had to work with on Monday. Wind shear is a moderate 10 - 20 knots, but is forecast to increase to the high range, 20 - 40 knots, on Wednesday. Ocean temperatures will drop below 26°C on Wednesday, so TD 19 has until Wednesday morning to get its act together and develop into Tropical Storm Tony. TD 19 will not threaten any land areas, and will likely be dead by Friday.


Video 1. Impressive weather video of the week: Baseball-sized hail splashing into a swimming pool during a hailstorm in South Africa on Saturday, October 20, 2012. The action gets interesting at about 1 minute into the video.

Tonight (October 23), PBS Frontline airs "Climate of Doubt", which examines the politics of climate change, and how a once generally accepted fact--that humans have contributed to, if not caused, global warming--has been dismissed by many politicians. It's on at 10 pm here in Michigan, but times may vary, depending upon the station.

Jeff Masters

Hurricane

Updated: 8:21 PM GMT on October 23, 2012

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Sandy forms south of Jamaica; TD 19 forms in middle Atlantic

By: JeffMasters, 9:48 PM GMT on October 22, 2012

The Hurricane Hunters found a band of 40 mph winds on the southeast side of Tropical Depression Eighteen this afternoon, prompting NHC to upgrade the system to Tropical Storm Sandy. Sandy is over very warm waters of 29.5°C, is in a moist environment, and has light wind shear of 5 - 10 knots. These conditions are very favorable for intensification, and Sandy's heavy thunderstorms are steadily organizing into curved spiral bands, as seen on satellite loops.


Figure 1. Late afternoon satellite image of Tropical Storm Sandy.

Forecast for Sandy
Wind shear is forecast to be in the low to moderate range, 5 - 20 knots, through Wednesday afternoon. This should allow continued development of Sandy, and rapid development is possible. The latest SHIPS model forecast is calling for a 52% chance that Sandy's winds will increase by 30 mph over a 24-hour period. The 5 pm EDT NHC Wind Probability Forecast gave a 25% chance that Sandy will be a hurricane by 2 pm EDT Wednesday, when the center should be close to Jamaica. Wind shear will rise to a high 25 - 30 knots by Thursday, which should weaken Sandy. By Friday, Sandy should be in the Central or Eastern Bahamas, and wind shear may increase further, making Sandy more of a hybrid subtropical storm. It is unclear at this point whether or not the trough pulling Sandy to the north will be strong enough to pull the storm all the way out to sea to the northeast; a very complicated steering environment will develop late this week, and it is possible that a narrow ridge of high pressure could build in over Sandy, and force the storm to the northwest, with a potential threat to the Northwestern Bahamas and U.S. East Coast by Saturday, as predicted by the ECMWF model. Sandy is not a threat to be a hurricane at that time, due to very high wind shear. Heavy rains are the main threat from Sandy.

Sandy's place in history
Sandy is the eighteenth named storm of the 2012 Atlantic hurricane season, tying this year with 1969 for seventh busiest Atlantic season since record keeping began in 1851. Here are the busiest Atlantic hurricane seasons on record:

2005 (28 named storms)
1933 (20 named storms, according to a new re-analysis)
1887 (19 named storms)
2010 (19 named storms)
2011 (19 named storms)
1995 (19 named storms)
1969 (18 named storms)
2012 (18 named storms)

There are two weak and short-lived storms from 2012 that stayed far out sea, and would likely have gone unnoticed in the pre-satellite era (before 1960): Tropical Storm Joyce and Tropical Storm Oscar. And while this season has been very busy for total number of named storms, we've had a below-average number of major hurricanes (just Hurricane Michael), and the total destructive power of the 2012 hurricane season as measured by the Accumulated Cyclone Energy (ACE) is only about 20% above average. See our newly-launched Accumulated Cyclone Energy (ACE) page for a storm-by-storm breakdown of this years ACE, plus historical ACE stats for each ocean basin. Thanks go to Angela Fritz for putting this together!


Figure 2. MODIS satellite image of TD 19 taken at 12:30 pm EDT October 22, 2012. Image credit: Navy Research Lab, Monterey.

Tropical Depression Nineteen forms in the middle Atlantic
Tropical Depression Nineteen is here, and appears poised to become Tropical Storm Tony by early Tuesday morning. TD 19 has a modest area of heavy thunderstorms, as seen on visible satellite images, and dry air from the upper-level low pressure system that it formed underneath is slowing development. TD 19 is over warm waters of 28°C, and wind shear is a moderate 10 - 20 knots. This shear is forecast to remain in the moderate range until Wednesday morning, which should allow TD 19 to develop into Tropical Storm Tony over the next day. On Wednesday, TD 19 is expected to encounter high wind shear of 20 - 30 knots, which should prevent further strengthening. TD 19 will not threaten any land areas, and is unlikely to reach hurricane strength.

Jeff Masters

Hurricane

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Tropical Depression 18 forms south of Jamaica

By: JeffMasters, 3:34 PM GMT on October 22, 2012

Tropical Depression Eighteen is here, and appears poised to become Tropical Storm Sandy by early Tuesday morning. TD 18 is over very warm waters of 29.5°C, is in a moist environment, and has light wind shear of 5 - 10 knots. These conditions are very favorable for intensification, and TD 18's heavy thunderstorms are steadily organizing into curved spiral bands, as seen on visible satellite loops. An Air Force hurricane hunter aircraft will investigate TD 18 this afternoon.


Figure 1. Morning satellite image of Tropical Depression Eighteen.

Forecast for TD 18
Wind shear is forecast to be in the low to moderate range, 5 - 20 knots, through Tuesday night. This should allow for some steady development of TD 18. On Tuesday, a trough of low pressure to the north is expected to pull TD 18 to the north-northeast, which should put the storm in the vicinity of Jamaica on Wednesday and Eastern Cuba on Thursday. The 11 am EDT NHC Wind Probability Forecast gives a 32% chance that TD 18 will be a hurricane by 8 am EDT Wednesday, when the center should be close to Jamaica. Wind shear will rise to a high 25 - 30 knots by Thursday, which should make it difficult for TD 18 to intensify. By Friday, TD 18 should be in the Central or Eastern Bahamas, and wind shear may increase further, making TD 18 more of a hybrid subtropical storm. It is unclear at this point whether or not the trough pulling TD 18 to the north will be strong enough to pull the storm all the way out to sea to the northeast; a very complicated steering environment will develop late this week, and it is possible that a narrow ridge of high pressure could build in over TD 18 and force the storm to the west-northwest, with a potential threat to the Northwestern Bahamas and U.S. East Coast by Saturday, as predicted by the ECMWF model. TD 18 will be capable of bringing heavy rains of 5 - 10 inches, with isolated amounts of up to 15 inches in mountainous areas, to Jamaica and Haiti, Monday night through Thursday. Heavy rains will begin on Tuesday in Eastern Cuba, and spread northwards into the Central and Eastern Bahamas by Wednesday. Heavy rains of 3 - 6 inches can be expected in the Cayman Islands and Dominican Republic, Tuesday through Thursday.

Invest 90L in the middle Atlantic
A small low pressure system (Invest 90L) about 700 miles east-northeast of the northernmost Lesser Antilles Islands is headed northward at about 10 mph. The disturbance has a modest area of heavy thunderstorms, as seen on visible satellite images, and is struggling with cool, dry air from the upper-level low pressure system that it is trying to form underneath. This upper-level low has provided 90L the spin it needs to become a tropical cyclone, though. Wind shear is a moderate 10 - 20 knots, and is forecast to remain in the moderate range until Wednesday morning. This may allow 90L to develop into a tropical cyclone before it encounters high wind shear of 20 - 30 knots on Wednesday. It's unlikely that 90L will affect any land areas. In their 8 am EDT tropical weather outlook, NHC gave 90L a 50% chance of developing into a tropical cyclone by Wednesday morning.

Jeff Masters

Hurricane

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99L south of Jamaica close to tropical depression status

By: JeffMasters, 2:33 PM GMT on October 22, 2012

A tropical disturbance centered about 300 hundred miles south of Jamaica (Invest 99L) is close to tropical depression status. The disturbance is nearly stationary over very warm waters of 29.5°C, and is in a moist environment. 99L has a large area of heavy thunderstorms that have a good degree of spin. These thunderstorms are steadily organizing into curved spiral bands, as seen on visible satellite loops. There are no obvious signs of a surface circulation, but an Air Force hurricane hunter aircraft will investigate 99L this afternoon to see if a tropical depression has formed.


Figure 1. Morning satellite image of Invest 99L.

Forecast for 99L
Wind shear is a low 5 - 10 knots, and is forecast to be in the low to moderate range, 5 - 20 knots, through Tuesday night. This should allow for some steady development of 99L, and there is strong model support for 99L becoming a tropical depression by Wednesday. Steering currents have collapsed, and 99L should move little today. On Tuesday, a trough of low pressure to the north of 99L is expected to turn the storm to the north or north-northeast, which should put the storm in the vicinity of Jamaica on Wednesday and Eastern Cuba on Thursday. By Friday, 99L should be in the Central or Eastern Bahamas. It is unclear at this point whether or not the trough pulling 99L to the north will be strong enough to pull the storm all the way out to sea to the northeast; a very complicated steering environment will develop late this week, and it is possible that a narrow ridge of high pressure could build in over 99L and force the storm to the west-northwest, with a potential threat to the Northwestern Bahamas and U.S. East Coast by Saturday. In their 8 am EDT tropical weather outlook, NHC gave 99L a 90% chance of developing into a tropical cyclone by Wednesday morning. 99L will be capable of bringing heavy rains of 5 - 10 inches, with isolated amounts of up to 15 inches in mountainous areas, to Jamaica and Haiti, Monday night through Thursday. Heavy rains will begin on Tuesday in Eastern Cuba, and spread northwards into the Central and Eastern Bahamas by Wednesday. Heavy rains of 3 - 6 inches can be expected in the Cayman Islands and Dominican Republic, Tuesday through Thursday.

Invest 90L in the middle Atlantic
A small low pressure system (Invest 90L) about 700 miles east-northeast of the northernmost Lesser Antilles Islands is headed northward at about 10 mph. The disturbance has a modest area of heavy thunderstorms, as seen on visible satellite images, and is struggling with cool, dry air from the upper-level low pressure system that it is trying to form underneath. This upper-level low has provided 90L the spin it needs to become a tropical cyclone, though. Wind shear is a moderate 10 - 20 knots, and is forecast to remain in the moderate range until Wednesday morning. This may allow 90L to develop into a tropical cyclone before it encounters high wind shear of 20 - 30 knots on Wednesday. It's unlikely that 90L will affect any land areas. In their 8 am EDT tropical weather outlook, NHC gave 90L a 50% chance of developing into a tropical cyclone by Wednesday morning.

The next name on the list of Atlantic tropical storms for 2012 is Sandy.

Jeff Masters

Hurricane

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99L a heavy rainfall threat for Jamaica, Haiti, and Eastern Cuba

By: JeffMasters, 2:35 PM GMT on October 21, 2012

A tropical wave embedded in a large trough of low pressure (Invest 99L) covers a large portion of the Central Caribbean between Hispaniola and the northern coast of South America. This storm has the potential to be a dangerous rainfall threat for Haiti, Jamaica, and eastern Cuba. The disturbance is headed west at less than 5 mph, is over very warm waters of 29°C, and is in a moist environment. 99L has a large area of heavy thunderstorms that have a good degree of spin. These thunderstorms are beginning to organize into spiral bands, as seen on visible satellite loops. However, the amount of heavy thunderstorm activity is about the same as yesterday, and there are no signs of a surface circulation. An Air Force hurricane hunter aircraft is scheduled to investigate 99L this afternoon, but I expect this flight will be rescheduled for later.


Figure 1. Morning satellite image of Invest 99L.

Forecast for 99L
Wind shear is a low 5 - 10 knots, and is forecast to be in the low to moderate range, 5 - 20 knots, through Tuesday. This should allow for some steady development of 99L, and there has been a good deal of model support for 99L becoming a tropical depression by Wednesday. Steering currents favor a continued slow westward movement for 99L through Tuesday. On Wednesday, a strong trough of low pressure to the north of 99L is expected to turn the storm to the north or north-northeast, which should put 99L in the vicinity of Jamaica on Wednesday and Eastern Cuba on Thursday. By Friday, 99L should be in the Central or Eastern Bahamas. It is unclear at this point whether or not the trough pulling 99L to the north will be strong enough to pull the storm all the way out to sea to the northeast; a narrow ridge of high pressure has the potential to build in over 99L late this week and force the storm west-northwest, with a potential threat to the western Bahamas and U.S. East Coast by next weekend. In their 8 am EDT tropical weather outlook, NHC gave 99L a 70% chance of developing into a tropical cyclone by Tuesday morning. 99L will be capable of bringing heavy rains of 5 - 10 inches, with isolated amounts of up to 15 inches in mountainous areas, to Jamaica and Haiti, Monday through Wednesday. Heavy rains will begin on Tuesday in Eastern Cuba, and spread northwards into the Central and Eastern Bahamas by Wednesday.

Invest 90L in the middle Atlantic
A tropical wave (Invest 90L) about 830 miles east-northeast of the northernmost Lesser Antilles Islands is headed west-northwest at about 10 mph. The disturbance has a small amount of heavy thunderstorms, as seen on visible satellite images, and has gotten tangled up with an upper-level low pressure system. This upper-level low is providing 90L the spin it needs to become a tropical cyclone, but is also pumping cool, dry air into the disturbance, which will keep any development slow over the next few days. Wind shear is a moderate 10 - 20 knots, and is forecast to remain in the moderate range until Tuesday. This may allow for some slow development of 90L before it encounters high wind shear of 20 - 30 knots on Tuesday night through Thursday. None of the reliable computer models develop 90L into a tropical cyclone, and it's unlikely that 90L will affect any land areas. In their 8 am EDT tropical weather outlook, NHC gave 90L a 30% chance of developing into a tropical cyclone by Tuesday morning.

The next name on the list of Atlantic tropical storms for 2012 is Sandy.

Jeff Masters

Hurricane

Updated: 2:36 PM GMT on October 21, 2012

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Caribbean disturbance 99L a dangerous rainfall threat for Haiti, Jamaica, and Cuba

By: JeffMasters, 4:12 PM GMT on October 20, 2012

A tropical wave embedded in a large trough of low pressure (Invest 99L) covers a large portion of the Central Caribbean between Hispaniola and the northern coast of South America. This storm has the potential to be a dangerous rainfall threat for Haiti, Jamaica, and eastern Cuba. The disturbance is headed west at less than 5 mph, is over very warm waters of 29°C, and is in a moist environment. 99L has a large area of heavy thunderstorms that are beginning to show some organization, as seen on visible satellite loops. Wind shear is a low 5 - 10 knots, and is forecast to be in the low to moderate range, 5 - 20 knots, through Tuesday. This should allow for some steady development of 99L, and there has been a good deal of model support for 99L becoming a tropical depression by Wednesday. Steering currents favor a continued slow westward movement for 99L through Tuesday, which will bring a multi-day period of heavy rains to Haiti, Jamaica, and eastern Cuba beginning on Sunday. The Dominican Republic may also see some heavy rains, though not as great. On Wednesday, a strong trough of low pressure will approaching the Eastern U.S., and the GFS and ECMWF models predict that this trough will turn 99L to the north, bringing the storm into the southeast Bahama Islands on Thursday or Friday. In their 8 am EDT tropical weather outlook, NHC gave 99L a 30% chance of developing into a tropical cyclone by Monday morning. I put these odds higher, at 40%. An Air Force hurricane hunter aircraft is scheduled to investigate 99L on Sunday afternoon.


Figure 1. Morning satellite image of Invest 99L.

Invest 90L in the middle Atlantic
A tropical wave (Invest 90L) about 1000 miles east-northeast of the northernmost Lesser Antilles Islands is headed west-northwest at about 10 mph. The disturbance has a modest amount of heavy thunderstorms, as seen on visible satellite images, and has gotten tangled up with an upper-level low pressure system. This upper-level low is pumping cool, dry air into the disturbance, which will keep any development slow over the next few days. Wind shear is a high 20 - 25 knots, but is forecast to drop to the moderate range, 10 - 20 knots, Sunday through Monday. This may allow for some slow development of 90L before it encounters very high wind shear of 20 - 40 knots on Tuesday and Wednesday. None of the reliable computer models develop 90L into a tropical cyclone. It's unlikely that 90L will affect any land areas. In their 8 am EDT tropical weather outlook, NHC gave 90L a 20% chance of developing into a tropical cyclone by Monday morning.

Jeff Masters

Hurricane

Updated: 4:12 PM GMT on October 20, 2012

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Forecast for the winter of 2012 - 2013

By: JeffMasters, 4:53 PM GMT on October 18, 2012

Expect increased chances of a warmer than average winter across most of the western U.S., and a cooler than average winter across much of Florida, said NOAA in their annual Winter Outlook, released on October 18. The forecast also called for increased chances of a wetter than average winter along the Gulf Coast, and drier than average conditions in the Pacific Northwest and Upper Midwest. This year's forecast was more difficult than usual to make, said Mike Halpert, deputy director of NOAA’s Climate Prediction Center, due to the uncertainty about what El Niño may do. El Niño strongly impacts winter weather patterns, by altering the path of the jet stream and the associated winter storms that travel along the axis of the jet stream. We currently have neutral El Niño conditions over the tropical Pacific ocean, which means that ocean temperatures are near average along the Equator from the coast of South America to the Date Line. But from early July to mid-September, a borderline weak El Niño event appeared to be consolidating, and most of the El Niño computer models were calling for a full-fledged El Niño event to be in place by winter. That is now seriously in question, as we've had four straight weeks with neutral conditions. NOAA's Climate Prediction Center has dropped their odds of a winter El Niño event to 55%. El Niño events typically cause cooler and wetter winter conditions across the Southern U.S., and warmer than average conditions across much of the Northern U.S.



Figure 1. Forecast temperature (top) and precipitation (bottom) for the U.S. for the upcoming winter, as predicted in the NOAA Winter Outlook, released on October 18.

What will the Arctic Oscillation and North Atlantic Oscillation do?
While El Niño is usually a key factor controlling winter weather patterns, it is often overshadowed by the North Atlantic Oscillation (NAO)--a climate pattern in the North Atlantic Ocean of fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores High. The NAO controls the strength and direction of westerly winds and storm tracks across the North Atlantic. A large difference in the pressure between Iceland and the Azores (positive NAO) leads to increased westerly winds and mild and wet winters in Europe. Positive NAO conditions also cause the Icelandic Low to draw a stronger south-westerly flow of air over eastern North America, preventing Arctic air from plunging southward. In contrast, if the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), westerly winds are suppressed, allowing Arctic air to spill southwards into eastern North America and Europe more readily. This pattern is kind of like leaving the refrigerator door ajar--the Arctic refrigerator warms up, but all the cold air spills out into the house where people live. The NAO is a close cousin of the Arctic Oscillation (AO), and can be thought of as the North Atlantic component of the larger-scale Arctic Oscillation. Since the AO is a larger-scale pattern, scientists refer to the AO instead of the NAO when discussing large-scale winter circulation patterns. The winter of 2009 - 2010 had the most extremely negative NAO pattern (and AO pattern) since record keeping began in 1950. Vicious "Snowmageddon" winter storms occurred in both the U.K. and the United States that winter, as both Europe and North America suffered though an unusually cold and snowy winter (the NAO index was -1.67, beating the previous record of -1.47 set in the winter of 1962 - 1963.) Thus, the phase and strength of the AO/NAO pattern is a key factor controlling winter weather. Unfortunately, this pattern is not predictable more than about two weeks in advance, and thus was not considered by NOAA in their forecast for the upcoming winter.


Figure 2. The forecast for the winter of 2011 - 2012 released October 20, 2011 by NOAA called for a classic La Niña weather pattern over the U.S.--increased chances of warmer and drier weather over the Southern U.S., and cooler and wetter over the northern tier of states (top panels.) Nearly the entire nation ended up having a warmer than average winter, with the winter of 2011 - 2012 ranking as the 4th warmest winter on record. While the Southeast U.S. did see a very dry winter, as is typical in a La Niña year, Texas had an unusually wet winter. Part of the reason for the very mild winter was because the North Atlantic Oscillation (NAO), averaged over the winter, reached its most extreme positive value (+1.37) since record keeping began in 1950 (previous record: +1.36 during the winter of 1994 - 1995.)

Winter weather and the sunspot cycle
Another major influence on the AO and winter circulation patterns may be the 11-year solar cycle. Recent satellite measurements of ultraviolet light changes due to the 11-year sunspot cycle show that these variations are larger than was previously thought, and may have major impacts on winter circulation patterns. A climate model study published in Nature Geosciences by Ineson et al. (2011) concluded that during the minimum of the 11-year sunspot cycle, the sharp drop in UV light can drive a strongly negative AO pattern, resulting in "cold winters in northern Europe and the United States, and mild winters over southern Europe and Canada, with little direct change in globally averaged temperature." The winters of 2009 - 2010 and 2010 - 2011 both occurred during a minimum in the 11-year sunspot cycle and fit this pattern, with strongly negative AO conditions leading to cold and snowy winters in northern Europe and the Eastern U.S. There was more solar activity during the winter of 2011 - 2012, which may have contributed to the fact that AO conditions reversed, ending up positive. The coming winter of 2012 - 2013 will have even more solar activity than last winter (Figure 3), potentially increasing the odds of a warm, positive-AO winter in northern Europe and the United States.


Figure 3. The number of sunspots from 2000 - 2012 shows that solar minimum occurred during the winter of 2008 - 2009, and that solar activity is now approaching a peak, expected to arrive sometime in 2013. Image credit: NOAA Space Weather Prediction Center.

How will Arctic sea ice loss affect the winter?
Francis et al. (2009) found that during 1979 - 2006, years that had unusually low summertime Arctic sea ice had a 10 - 20% reduction in the temperature difference between the Equator and North Pole. This resulted in a weaker jet stream with slower winds that lasted a full six months, through fall and winter. The weaker jet caused a weaker Aleutian Low and Icelandic Low during the winter, resulting in a more negative Arctic Oscillation (AO), allowing cold air to spill out of the Arctic and into Europe and the Eastern U.S. Thus, summers with high Arctic sea ice loss may increase the odds of cold, snowy winters in Europe and the Eastern U.S. In my April 2, 2012 blog post, Arctic sea ice loss tied to unusual jet stream patterns, I discuss three additional research papers published in 2012 that argue for a major impact of Arctic sea ice loss on Northern Hemisphere weather in fall and winter, with sea ice loss causing an increase in the probability of negative-AO winters. But cold air may also be more likely to spill out of the Arctic in winter due to the decades-long pattern of warming and cooling of Atlantic Ocean waters known as the Atlantic Multidecadal Oscillation (AMO). A 2012 study by NASA scientists found that the warm phase of the AMO (like we have been in since 1995) causes more instances of atmospheric blocking, where the jet stream gets "stuck" in place, leading to long periods of extreme weather. It will be interesting to see how all these factors play out in the coming years. If these three newly-published studies are correct, the U.S. should see an increase in cold, snowy winters like 2010 - 2011 and 2009 - 2010 in coming decades, as Arctic sea ice continues to melt, affecting fall and winter atmospheric circulation patterns more strongly.

What happened during past winters with similar atmospheric conditions?
During a press conference today, Mike Halpert, deputy director of NOAA’s Climate Prediction Center, was asked to compare weather conditions this fall to those observed in previous years. The idea is that by looking at previous "analogue" years with similar progressions of the El Niño pattern, one might anticipate what the winter climate might be like. Halpert emphasized that this year is totally unique in the 63 years we've been keeping statistics on El Niño. Never before has an El Niño event begun to form in July and August, then quit in mid-September. Even if we did have a few analogue years, it wouldn't do any good, though--Halpert stated that we would need a data base of at least 1,000 years of historical data to make a skillful winter forecast based on analogue years.

Summary
I'm often asked by friends and neighbors what my forecast for the coming winter is, but I tell them to flip a coin, or catch some woolley bear caterpillars for me so I can count their stripes and make a woolley bear winter forecast (this year's Woolley Worm Festival in Banner Elk, North Carolina is this weekend, so we'll know then what the official Woolley Worm winter forecast is.) Making an accurate winter forecast is very difficult, as the interplay between El Niño, the AO/NAO, the AMO, Arctic sea ice loss, and the 11-year sunspot cycle is complex and poorly understood. I've learned to expect the unexpected and unprecedented from our weather over the past few winters; perhaps the most unexpected thing would be a very average winter during 2012 - 2013.

References
Francis, J. A., W. Chan, D. J. Leathers, J. R. Miller, and D. E. Veron, 2009: Winter northern hemisphere weather patterns remember summer Arctic sea-ice extent. Geophys. Res. Lett., 36, L07503, doi:10.1029/2009GL037274.

Honda, M., J. Inoue, and S. Yamane, 2009: Influence of low Arctic sea-ice minima on anomalously cold Eurasian winters. Geophys. Res. Lett., 36, L08707, doi:10.1029/2008GL037079.

Ineson, S., et al., 2011, Solar forcing of winter climate variability in the Northern Hemisphere, Nature Geoscience (2011) doi:10.1038/ngeo1282

Overland, J. E., and M. Wang, 2010: Large-scale atmospheric circulation changes associated with the recent loss of Arctic sea ice. Tellus, 62A, 1.9.

Petoukhov, V., and V. Semenov, 2010: A link between reduced Barents-Kara sea ice and cold winter extremes over northern continents. J. Geophys. Res.-Atmos., ISSN 0148-0227.

Seager, R., Y. Kushnir, J. Nakamura, M. Ting, and N. Naik (2010), Northern Hemisphere winter snow anomalies: ENSO, NAO and the winter of 2009/10, Geophys. Res. Lett., 37, L14703, doi:10.1029/2010GL043830.

Quiet in the Atlantic and Eastern Pacific
Forecasters at the National Hurricane Center get a rare break today, as there are no tropical cyclones or threat areas in either the Atlantic or Eastern Pacific to discuss. Most of the models are predicting that an area of disturbed weather capable of becoming a tropical depression will form in the Central Caribbean Sea south of Jamaica by the end of next week. Residents of Central America, Jamaica, Cuba, Haiti, and the Cayman Islands should anticipate the possibility of a multi-day period of very heavy rains affecting them late next week.

I'll have a new post on Saturday.

Jeff Masters

Winter Weather

Updated: 1:34 AM GMT on October 20, 2012

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Paul pulls its punch before hitting Baja; Rafael brushes Bermuda

By: JeffMasters, 12:31 PM GMT on October 17, 2012

Hurricane Paul weakened rapidly just before landfall on Mexico's Baja coast on Tuesday evening, as wind shear of 30 - 40 knots tore into the storm. Paul peaked as a Category 3 hurricane with 120 mph winds at 2 pm PDT on Monday, but was just a tropical storm with 60 mph winds Tuesday evening when the center finally reached the coast of Baja. Paul hit a region of coast that is very sparsely populated, and I expect damage from the weakening storm was relatively light. Rainfall amounts of 2 - 3" were common over Baja from Paul, but there have been no reports of damaging flooding thus far. Paul has weakened to a tropical storm with 40 mph winds this morning, and will likely be declared dead later today or on Thursday. Significant moisture from Paul is not expected to reach the U.S.


Figure 1. MODIS satellite image of Hurricane Paul taken at 4:25 pm EDT Tuesday, October 16, 2012. At the time, Paul was approaching landfall on the Mexican Baja coast as a Category 1 hurricane with 75 mph winds. Image credit: NASA.

Rafael brushes Bermuda
Hurricane Rafael cruised by Bermuda Tuesday night as a Category 1 storm with 85 mph winds. At its closest point of approach, the center of Rafael passed about 110 miles east of Bermuda. The Bermuda Airport recorded top winds of 34 mph, gusting to 51 mph, at 9 pm AST Tuesday night. The hurricane dumped 1.71" of rain on Bermuda, and did no significant damage. Rafael is beginning to transition to an extratropical storm today as it heads northeastward out to sea, and it will likely be declared post-tropical on Thursday.


Figure 2. Radar image of Hurricane Rafael as seen by the Bermuda radar at 8:03 pm AST on October 16, 2012. At the time, Rafael was a Category 1 hurricane with 85 mph winds, and was bringing sustained winds of 31 mph, gusting to 44 mph, to Bermuda.


Figure 3. MODIS satellite image of Hurricane Rafael approaching Bermuda, taken at 12:10 pm EDT Tuesday, October 16, 2012. At the time, Rafael was at peak strength as a Category 1 hurricane with 90 mph winds. Image credit: NASA.

Elsewhere in the Atlantic
Most of the models are predicting that the Southwest Caribbean Sea off the coast of Nicaragua will see a broad area of low pressure develop by the middle of next week. This low will likely bring a multi-day period of heavy rains to portions of Central America, Jamaica, Cuba, and the Cayman Islands late next week. None of the reliable models are predicting formation of a new tropical cyclone in the Atlantic through October 23, though we will need to watch the Southwest Caribbean late next week.

Jeff Masters

Hurricane

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Hurricane Paul pounding Baja; Hurricane Rafael brushing Bermuda

By: JeffMasters, 3:06 PM GMT on October 16, 2012

Hurricane Paul put on an impressive burst of rapid intensification on Monday, topping out as a Category 3 hurricane with 120 mph winds at 2 pm PDT on Monday. Paul has weakened some this morning, due to high wind shear of 30 knots, but remains a potent Category 2 hurricane with 105 mph winds as it heads towards landfall this afternoon on the Baja Mexico coast. The 3006-passenger cruise ship Carnival Splendor made a daring run southeastwards along the Baja coast in front of Hurricane Paul, and encountered some very heavy weather this morning. At 2 am PDT, the vessel reported sustained winds of 54 mph and hail in a heavy squall located about 160 miles northeast of Paul's eye. Four hours later, at 6 am PDT, the ship was still measuring 54 mph winds, at point about 140 miles east of the eye and 40 miles northwest of the Cabo San Lucas on the southern tip of the Baja Peninsula. The winds were measured on top of the ship, at an altitude more than 100 feet above the standard 10 meter (32.8') altitude used to report winds. If you know of a passenger who was on the ship, tell them to upload a wunderphoto and a report of what is was like! The view from the deck webcam shows that not too many passengers were out taking wunderphotos this morning, though.

Since the region of coast where Paul will hit is very sparsely populated, heavy rains will be the main threat from the storm. Cabo San Lucas has picked up 2.23" of rain from Paul as of 7 am PDT this morning, and San Jose Del Cabo picked up 2.00". Neither city is expected to get tropical storm-force winds from Paul, according to the latest wind probability forecast from NHC. Paul's formation brings this year's tally in the Eastern Pacific to 16 named storms, 10 hurricanes, and 5 major hurricanes. An average Eastern Pacific season has 15 named storms, 8 hurricanes, and 3 major hurricanes.


Figure 1. MODIS satellite image of Hurricane Paul taken at 2:15 pm EDT Monday, October 15, 2012. At the time, Paul was peaking in intensity--a Category 3 hurricane with 120 mph winds. Image credit: NASA.

Rafael becomes a hurricane
Hurricane Rafael became the ninth hurricane of this busy 2012 Atlantic hurricane season on Monday afternoon. Data from the Hurricane Hunters and satellite loops show that Rafael is holding its own against high wind shear near 30 knots. Rafael has even managed to intensify slightly this morning, to a Category 1 storm with 90 mph winds, as it heads north-northeast on a path that is expected to take the center about 140 miles east of Bermuda near 8 pm EDT this Tuesday night. Images from the Bermuda radar show that the outer spiral bands of Rafael have reached the island, and very heavy rains lie just to Bermuda's south. Wind shear is expected to increase to an extremely high 40 knots on Wednesday, which should be able to weaken Rafael to a tropical storm. The 11 am EDT wind probability forecast from NHC gave Bermuda a 44% chance of experiencing tropical storm-force winds from Rafael. The models are pretty tightly clustered showing a track for Rafael to the east of Bermuda, putting the island on the weaker (left front) side of the storm.


Figure 2. MODIS satellite image of Tropical Storm Rafael taken at 11:55 am EDT Monday, October 15, 2012. At the time, Rafael was intensifying, with top winds of 70 mph. Image credit: NASA.

Possible Caribbean development next week
Most of the models are predicting that an area of disturbed weather capable of becoming a tropical depression will form in the Southwest Caribbean Sea off the coast of Nicaragua by the middle of next week. It's too early speculate on where such a storm might go, but residents of Central America, Jamaica, Cuba, and the Cayman Islands should anticipate the possibility of a multi-day period of very heavy rains affecting them late next week, even if a tropical depression does not form.


Figure 3. I couldn't resist reposting this image: a coronal mass ejection (CME) hit Earth's magnetic field on Oct. 8, 2012, sparking a dramatic display of Northern Lights that lasted for several days. The aurora combined with clouds to create this remarkable scene over Lekangsund, Norway, on Oct. 10, 2012, as captured by Hugo Løhre. Larger versions of the image are available at nasa.gov.

Jeff Masters

Hurricane

Updated: 3:07 PM GMT on October 16, 2012

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September 2012: Earth's warmest September on record

By: JeffMasters, 5:01 PM GMT on October 15, 2012

September 2012 was tied with 2005 as the globe's warmest September on record, according to the National Oceanic and Atmospheric Administration's National Climatic Data Center (NCDC). Global temperature records begin in 1880. NASA rated September 2012 the 4th warmest September on record. September 2012 global land temperatures were the 3rd warmest on record, and global ocean temperatures were the 2nd warmest on record. September 2012 was the 331st consecutive month with global temperatures warmer than the 20th century average. The last time Earth had a below-average September global temperature was in 1976, and the last below-average month of any kind was February 1985. Global satellite-measured temperatures in September 2012 for the lowest 8 km of the atmosphere were 5th or 3rd warmest in the 34-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH). Wunderground's weather historian, Christopher C. Burt, has a comprehensive post on the notable weather events of September 2012 in his September 2012 Global Weather Extremes Summary.


Figure 1. Departure of temperature from average for September 2012, which tied 2005 as the warmest September on record. Parts of east central Russia observed record warmth, as did parts of Venezuela, French Guinea, and northern Brazil. Nearly all of South America was much warmer than average, as were western Australia and central to eastern Europe. Far eastern Russia, a few regions in southern Africa, and parts of China were cooler than average. Image credit: National Climatic Data Center (NCDC) .

El Niño watch continues
Neutral El Niño conditions exist in the equatorial Pacific, where sea surface temperatures were 0.1°C above average as of October 15. NOAA's Climate Prediction Center (CPC) has issued an El Niño watch, and gives a 55% chance that an El Niño event will be in place during the October - November - December period. Temperatures in the equatorial Eastern Pacific need to be 0.5°C above average or warmer to be considered an El Niño. El Niño conditions tend to bring cooler and wetter winter weather to the Southern U.S.


Figure 2. Arctic sea ice extent in September 2012 was the lowest measured, since satellite records began in 1979. Image credit: National Snow and Ice Data Center (NSIDC).

Arctic sea ice falls to lowest extent on record in September
Arctic sea ice extent during September reached its lowest extent in the 35-year satellite record, according to the National Snow and Ice Data Center (NSIDC). As of October 14, Arctic sea extent had set a new record low for the date every day since July 27. I have much more to say about this year's extraordinary loss of Arctic sea ice in my September 20, 2012 post, Earth's attic is on fire: Arctic sea ice bottoms out at a new record low.

Jeff Masters

Climate Summaries

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Rafael expected to brush Bermuda; Hurricane Paul headed towards Baja

By: JeffMasters, 3:24 PM GMT on October 15, 2012

Tropical Storm Rafael is intensifying as it pulls away from the Lesser Antilles Islands. Data from the Hurricane Hunters and satellite loops show that Rafael has gotten more organized this morning, with a blow-up of very heavy thunderstorms near the center that have created a large Central Dense Overcast (CDO), the hallmark of an intensifying tropical storm that is near hurricane strength. Rafael is experiencing high wind shear near 20 knots, and this shear is expected to remain constant through Tuesday, which should allow Rafael to intensify into a Category 1 hurricane. Sporadic heavy rains from Rafael will gradually diminish today over the Leeward Islands, Puerto Rico, and the Virgin Islands. A tropical storm warning has been posted for Bermuda, but if Rafael follows the official NHC forecast track, tropical storm-force winds will remain just offshore from Bermuda as Rafael makes its closest pass by the island on Tuesday evening. The 11 am EDT wind probability forecast from NHC gave Bermuda a 29% chance of experiencing tropical storm-force winds between Monday night and Wednesday morning, and a 1% chance of experiencing hurricane-force winds. The models are pretty tightly clustered showing a track for Rafael to the east of Bermuda, putting the island on the weaker (left front) side of the storm.


Figure 1. Morning satellite image of Tropical Storm Rafael.

Hurricane Paul forms in the Eastern Pacific
Hurricane Paul is putting on a burst of rapid intensification, and is a strong Category 1 hurricane with 90 mph as it heads northwards towards Mexico's Baja Peninsula. Paul will have favorable conditions for intensification through Tuesday morning, when wind shear is predicted to rise to the high range, above 20 knots. Paul should be weakening quickly as it approaches the coast of Baja Tuesday night and Wednesday morning, but heavy rains from the storm will spread over Baja beginning on Tuesday night, and these rains will be capable of causing flooding problems. Paul's formation brings this year's tally of named storms in the East Pacific to sixteen, making 2012 just the third year since records began in 1949 that both the Eastern Pacific and Atlantic have had at least sixteen named storms. The other years were 2003 and 2008. On average, the Eastern Pacific experiences one named storm after October 15, which would bring this season's total activity to 17 named storms, 10 hurricanes, and 4 major hurricanes. An average Eastern Pacific season has 15 named storms, 8 hurricanes, and 3 major hurricanes.


Figure 2. Morning satellite image of Hurricane Paul.

A rare early-season major tropical cyclone in the Southwest Pacific
It's springtime in the Southern Hemisphere, where Category 3 Tropical Cyclone Anais is churning southwestwards towards Madgascar. According to Meteo France in La Reunion Island, Anais is the earliest major hurricane to form during the Southwest Indian Ocean's tropical cyclone season, which typically runs from November to May. Anais' formation in mid-October is akin to getting a major hurricane in the Atlantic during April--something which has never occurred (the earliest major hurricane on record in the Atlantic occurred on May 21, 1951.) Anais is the second earliest hurricane of any kind to form so early in the Southwest Indian Ocean tropical cyclone season, after Tropical Cyclone Blanche of October 10, 1969. Anais has moved over cooler waters, and has weakened slightly to 115 mph winds, down from the peak 120 mph it had on Sunday. Further weakening is expected over the next few days as wind shear increases and the waters beneath continue to cool, and Anais is not expected to directly impact any land areas.


Figure 3. MODIS satellite image of Tropical Cyclone Anais in the Southwest Pacific taken at 5:40 am EDT Monday October 15, 2012. At the time, Anais was a Category 3 storm with 115 mph winds, and was the strongest tropical cyclone ever observed in the Southwest Pacific so early in their hurricane season. Image credit: NASA.

Jeff Masters

Hurricane

Updated: 6:22 PM GMT on October 15, 2012

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Rafael intensifying, but is pulling away from the Lesser Antilles

By: JeffMasters, 3:55 PM GMT on October 14, 2012

Tropical Storm Rafael is intensifying, but is headed northwards away from the Lesser Antilles Islands, after bringing gusty winds and heavy rains to the islands over the past two days. Three-day rainfall amounts of 2 - 3" were common over the Leeward Islands, but the winds mostly stayed below tropical storm-force. Here are some of the peak wind gusts from Rafael and rainfall totals from Oct 11 through 10 am EDT October 14:

Barbados, 47 mph, 0.81"
Antigua: 37 mph, 3.66"
Martinique: 30 mph, 3.10"
St. Lucia: 39 mph, 2.07"
St. Martin: 45 mph, 2.56"
Guadaloupe: 36 mph, 2.51"
Dominica: 25 mph, 2.68"
St. Kiits: 34 mph, 3.47"

Satellite loops show that Rafael has gotten much more organized late this morning, with an impressive spiral band with very heavy thunderstorms to the east of the center. Heavy thunderstorms with cold cloud tops are forming over the center, the hallmark of an intensifying tropical storm. The Hurricane Hunters found a central pressure of 997 mb, and winds at their 5,000-foot flight level of 68 mph this morning. Rafael is experiencing a moderate 10 - 20 knots of wind shear.


Figure 1. Morning satellite image of Tropical Storm Rafael.

Forecast for Rafael
Wind shear is expected to remain in the moderate range through Tuesday, which should allow Rafael to intensify into a Category 1 hurricane. Heavy rains will continue over the Leeward Islands today and diminish on Monday. A tropical storm watch has been posted for Bermuda, which is at risk of seeing tropical storm-force winds from Rafael on Tuesday. The 11 am EDT wind probability forecast from NHC gave Bermuda a 40% chance of experiencing tropical storm-force winds between Monday night and Wednesday morning, and a 6% chance of experiencing hurricane-force winds. The models are pretty tightly clustered showing a track for Rafael to the east of Bermuda, which would put the island on the weaker (left front) side of the storm.

Tropical Storm Paul forms in the Eastern Pacific
Tropical Storm Paul formed yesterday in the East Pacific, and is headed northwards towards Mexico's Baja Peninsula. Paul's formation brings this year's tally of named storms in the East Pacific to sixteen, making 2012 just the third year since records began in 1949 that both the Eastern Pacific and Atlantic have had at least sixteen named storms. The other years were 2003 and 2008.


Figure 2. MODIS satellite image of Tropical Cyclone Anais in the Southwest Pacific taken at 2:05 am EDT Sunday October 14, 2012. At the time, Anais was a Category 3 storm with 120 mph winds, the strongest tropical cyclone ever observed in the Southwest Pacific so early in their hurricane season. Image credit: NASA.

A rare early-season major tropical cyclone in the Southwest Indian Ocean
It's springtime in the Southern Hemisphere, where an unusual tropical cyclone has formed--Tropical Cyclone Anais, which hit Category 3 strength with 120 mph winds. According to Meteo France in La Reunion Island, Anais is the earliest major hurricane to form during the Southwest Indian Ocean's tropical cyclone season, which typically runs from November to May. Anais' formation in mid-October is akin to getting a major hurricane in the Atlantic during April, something which has never occurred (the earliest major hurricane on record in the Atlantic occurred on May 21, 1951.) Anais is the second earliest hurricane of any kind to form so early in the Southwest Indian Ocean tropical cyclone season, after Tropical Cyclone Blanche of October 10, 1969. Anais may reach Category 4 strength before cooler waters and increased wind shear weaken the storm as it approaches Madagascar.

Jeff Masters

Hurricane

Updated: 6:23 PM GMT on October 15, 2012

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Tropical Storm Rafael drenching the Lesser Antilles

By: JeffMasters, 4:15 PM GMT on October 13, 2012

Tropical Storm Rafael formed late yesterday afternoon over the Lesser Antilles Islands, and is bringing gusty winds and very heavy rains to the islands today. Two-day rainfall amounts of 1 - 3" have been common over the Leeward Islands from Rafael, but the winds have stayed below tropical storm-force so far. Here are some of the peak gusts from Rafael as of noon EDT on Saturday:

Antigua: 37 mph
Martinique: 28 mph
St. Lucia: 39 mph
St. Martin: 26 mph

Satellite loops and radar loops show that Rafael has a large area of heavy thunderstorms to the east and southeast of the center. These thunderstorms are poorly organized, but were beginning to show a more organized spiral banding look late this morning. An upper-level low centered a few hundred miles south of the eastern Dominican Republic is pumping dry air into the west side of Rafael, and is creating a moderate 10 - 20 knots of wind shear.


Figure 1. Radar image out of Martinique from 11:45 am EDT Saturday, October 13, 2012 showed a large area of heavy rain over nearly the entire Lesser Antilles Island chain due to Tropical Storm Rafael. Image credit: Meteo France.

Forecast for Rafael
The shear has dropped since Friday, and is is expected to remain in the moderate range through Monday, which should allow for some slow intensification of Rafael over the next few days. Heavy rains will continue over the entire Lesser Antilles Island chain, plus the Virgin Islands, today through Sunday. Puerto Rico can expect heavy rains on Sunday, but the dry air on the west side of Rafael should keep the Dominican Republic from seeing heavy rains. Rafael's strongest winds will be to the right of the center, and islands of Barbuda, Antigua, Montserrat, St. Kitts and Nevis, St. Barthelemy, St. Eustatis, Anguilla, St. Martin, and Saba may see sustained winds as high as 45 mph Saturday night through Sunday as the strongest bands of Rafael move through. The only island at risk of seeing hurricane-force winds from Rafael is Bermuda. The 11 am EDT wind probability forecast from NHC gave Bermuda a 3% chance of experiencing hurricane-force winds on Tuesday, and a 27% chance of experiencing tropical storm-force winds.

Rafael's place in history
Rafael is the seventeenth named storm of the 2012 Atlantic hurricane season, putting this year in eighth place for busiest Atlantic season since record keeping began in 1851. Here are the busiest Atlantic hurricane seasons on record:

2005 (28 named storms)
1933 (20 named storms, according to a new re-analysis)
1887 (19 named storms)
2010 (19 named storms)
2011 (19 named storms)
1995 (19 named storms)
1969 (18 named storms)
2012 (17 named storms)

There are two weak and short-lived storms from 2012 that stayed far out sea, and would likely have gone unnoticed in the pre-satellite era (before 1960): Tropical Storm Joyce and Tropical Storm Oscar. And while this season has been very busy for total number of named storms, we've had a below-average number of major hurricanes (just Hurricane Michael), and the total destructive power of the 2012 hurricane season as measured by the Accumulated Cyclone Energy (ACE) is only about 20% above average. See our newly-launched Accumulated Cyclone Energy (ACE) page for a storm-by-storm breakdown of this years ACE, plus historical ACE stats for each ocean basin. Thanks go to Angela Fritz for putting this together!


Figure 2. MODIS satellite image of Tropical Storm Patty taken at 1:30 pm EDT Friday, October 12, 2012. At the time, Patty had top winds of 40 mph. High wind shear had exposed the lower-level circulation to view. Late on Saturday morning, wind shear had ripped Patty apart and the storm was declared dead. Image credit: NASA.

Jeff Masters

Hurricane

Updated: 4:18 PM GMT on October 13, 2012

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Patty little threat to the Bahamas; 98L close to tropical storm status

By: JeffMasters, 2:50 PM GMT on October 12, 2012

Tropical Storm Patty formed late yesterday afternoon just east of the Central Bahama Islands. Patty is the sixteenth named storm of the 2012 Atlantic hurricane season, putting this year in a tie for eighth place for busiest Atlantic season since record keeping began in 1851. Patty isn't going to be around for long, though. Satellite loops show a very sickly storm, with the low-level circulation center exposed to view, and the storm's heavy thunderstorm all pushed to the northeast side of the center of circulation due to strong upper-level winds out of the southwest creating a high 20 - 30 knots of wind shear. An approaching cold front is dumping dry, stable air into Patty, and the cold front and high shear will likely destroy the storm by Saturday evening. Patty will likely have a minimal impact on the Bahamas. The storm has brought a few sporadic heavy rain showers to the Southeast Bahama Islands this morning, and this activity may continue through Saturday morning. A hurricane hunter aircraft is on its way to Patty, and will be there early this afternoon.


Figure 1. MODIS satellite image of Tropical Depression 16 taken at 11:16 am EDT Thursday, October 11, 2012. At the time, TD 16 had 35 mph winds, and was named Tropical Storm Patty six hours later. Image credit: NASA.

98L bringing heavy rain, high winds to Lesser Antilles
A strong tropical wave (Invest 98L) is bringing tropical-storm force winds and heavy rains to the Lesser Antilles this morning. At 9 am local time, winds at Barbados's Grantly Adams Airport hit a sustained 39 mph, which is minimum tropical storm-force. Wind gusts as high as 47 mph were observed on Barbados this morning. A pass from the Windsat satellite at 12:38 am EDT found that 98L had top winds of 35 mph near 17°N latitude, a few hundred miles east of Antigua. The storm is headed north-northwest to northwest at about 10 - 15 mph, and will bring tropical storm conditions to much of the Lesser Antilles Islands today and Saturday. The disturbance has plenty of spin and a large amount of moderately well-organized heavy thunderstorms, as seen on Martinique radar and satellite loops. An elongated, poorly-defined surface circulation is apparent just west of the central Lesser Antilles Islands, but satellite imagery and airport observations from the islands do not show the well-defined closed surface circulation needed for 98L to be classified as a tropical storm. An upper-level low centered a few hundred miles south of the eastern Dominican Republic is pumping dry air into the west side of 98L, and creating a high 15 - 30 knots of wind shear. An Air Force hurricane hunter aircraft is scheduled to investigate 98L this afternoon.


Figure 2. Morning satellite image of Invest 98L over the Lesser Antilles Islands.

Forecast for 98L
Wind shear is predicted to diminish to the moderate range, 15 - 20 knots, tonight through Saturday night. Given 98L's current degree of organization, the forecast drop in wind shear, and a high degree of model support for development, NHC's 8 am Tropical Weather Outlook forecast of an 80% chance of development by Sunday morning for 98L looks reasonable. I expect 98L to be upgraded later today, and it will probably skip being classified as a tropical depression and immediately be named Tropical Storm Rafael. The models are pretty well clustered for the track of 98L, taking it north-northwest through the Lesser Antilles towards Bermuda. With most of the storm's heavy thunderstorms on its east side due to dry air to the west, the Virgin Islands, Puerto Rico, and the eastern Dominican Republic are likely to see much weaker winds and less heavy rain than the Leeward Islands. The Leeward Islands can expect tropical storm conditions with occasional sustained winds of 35 - 45 mph today and Saturday as 98L moves through. The storm will make its closest pass to Bermuda on Tuesday morning, and it is possible that 98L will be capable of bringing tropical storm conditions to Bermuda. However, the track of 98L on Monday and Tuesday is rather uncertain, due to the possible interaction of the storm with the remnants of Tropical Storm Patty. 98L is not a threat to the U.S., though it could affect Newfoundland, Canada next week.

Jeff Masters

Hurricane

Updated: 3:29 PM GMT on October 13, 2012

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Tropical Depression Sixteen has formed; 98L likely to develop

By: angelafritz , 6:06 PM GMT on October 11, 2012

Tropical Depression Sixteen formed from 97L this morning, though continues to be no threat and is expected to dissipate by Friday night. The depression is located east of the Bahamas and north of the Turks and Caicos Islands, and has had organized thunderstorm activity over the past couple of days, though an approaching cold front is beginning to take its toll on the system, which is apparent on satellite loops. Wind shear is around 20 knots from the southwest and increasing, which is exposing the cyclone's center of circulation and will result in the cyclone's demise. The system's thunderstorm activity could reach the far eastern Bahamas on Friday, but it's likely that Sixteen will not impact the islands before dissipating.


Figure 1. Visible satellite imagery of Tropical Depression Sixteen captured at 1:17pm EDT.

98L still likely to develop

Strong thunderstorm activity continues in 98L today, despite strong wind shear to its north, around 30 knots. This wind shear is expected to decrease over the next few days, providing a window for the wave to develop over the weekend. Most of the models are expecting 98L to to strengthen to a tropical storm by Sunday. The GFS and the GFDL even go as far to say that 98L could reach Category 1 hurricane strength. In terms of track, all of the models are forecasting a recurving pattern. The ECMWF pushes the potential cyclone farthest west, possibly reaching Hispaniola. The HWRF carries the system northwest over the next three days, and across Puerto Rico. The GFS has a similar solution this morning, as well. The model with the eastern-most forecast is the GFDL, which expects 98L to track north-northwest, scraping the eastern side of the Lesser Antilles, and avoiding land thereafter.

The National Hurricane Center gives 98L a 50% chance of development over the next 48 hours.

Angela

Hurricane

Updated: 6:12 PM GMT on October 12, 2012

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98L may develop this weekend; 97L no threat

By: JeffMasters, 11:57 AM GMT on October 11, 2012

A tropical wave located about 350 miles east of the Lesser Antilles Islands (Invest 98L) is headed west-northwest at about 10 - 15 mph, and is a threat to develop into a tropical depression this weekend. The disturbance has a modest amount of spin and a large amount of heavy thunderstorms, as seen on satellite loops and Barbados radar. The thunderstorms have shown more organization this morning, but there is no obvious surface circulation visible on satellite imagery. This morning's ASCAT pass showed top winds of 30 - 35 mph near 15°N, 55°W. Wind shear is a high 20 - 30 knots over 98L, the atmosphere is moist, and ocean temperatures are a very warm 30°C. With wind shear expected to diminish on Saturday to the moderate range, 10 - 20 knots, 98L may be able to develop into a tropical cyclone this weekend. The disturbance has a high amount of support for development among the reliable computer models. The NOGAPS model predicts 98L will develop into a tropical depression or tropical storm on Sunday, about 400 hundred miles north of Puerto Rico. The GFS model predicts 98L will develop on Saturday, when the center will be very close to the northernmost Lesser Antilles Islands. The ECMWF model predicts a more westerly path for 98L into the southeast Bahama Islands, with development delayed until Monday. The models are unified in forecasting that 98L will turn to the north by Monday and be drawn into a trough of low pressure. It does not appear that 98L will be a threat to the U.S. In their 8 am Tropical Weather Outlook, NHC gave 98L a 50% chance of becoming a tropical cyclone by Saturday morning. A hurricane hunter aircraft is scheduled to visit 98L on Friday afternoon.


Figure 1. Morning satellite image of Invest 98L approaching the Lesser Antilles Islands.

Invest 97L east of the Bahamas
A tropical wave located about 250 miles east of the central Bahama Islands (Invest 97L) is headed slowly southwards. The disturbance is well-organized, with a developing surface circulation and a respectable area of heavy thunderstorms, as seen on satellite loops. Wind shear is a high 20 knots over 97L, and the shear has pushed all the storm's heavy thunderstorms to its east side. Shear is expected to increase sharply later today as a cold front overtakes the system. This cold front should be capable of destroying 97L by Friday.

Jeff Masters

Hurricane

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98L may develop early next week

By: JeffMasters, 2:13 PM GMT on October 10, 2012

A tropical wave located about 500 miles east of the Lesser Antilles Islands (Invest 98L) is headed west-northwest at about 15 mph, and is a threat to develop into a tropical depression early next week. The disturbance has a modest amount of spin and a large amount of disorganized heavy thunderstorms, as seen on satellite loops, but there is no sign of a surface circulation. Wind shear is a moderate 10 - 20 knots over 98L, the atmosphere is moist, and ocean temperatures are a very warm 30°C. With wind shear expected to rise to the high range, 20 - 30 knots, Wednesday night though Friday, any development the next few days should be slow. The shear is due to an upper-level trough of low pressure centered a few hundred miles northeast of the Lesser Antilles Islands. Once 98L passes beyond the Lesser Antilles on Saturday, the shearing winds of the trough will diminish to the moderate range, 10 - 20 knots. Most of the models predict that 98L will show increasing development beginning on Saturday. The NOGAPS model has 98L developing into a tropical depression on Monday, a few hundred miles northeast of the southeastern Bahama Islands. The GFS model is much slower with the system, predicting it will develop into a tropical depression on Monday, a few hundred miles north of Puerto Rico. Moisture from 98L should affect the Lesser Antilles Islands on Thursday and Friday, and Puerto Rico and the Virgin Islands on Friday and Saturday. It is uncertain if heavy rains from 98L will affect the Dominican Republic early next week; the storm may stay too far to the northeast. In their 8 am Tropical Weather Outlook, NHC gave 98L a 30% chance of becoming a tropical cyclone by Friday morning. The long range fate of 98L is uncertain; the ECMWF model shows 98L becoming absorbed by a cold front and bringing heavy rains to Canada and New England on Tuesday and Wednesday next week, while the GFS and NOGAPS models predict that 98L will stay out to sea for at least the next week.


Figure 1. Morning satellite image of Invest 98L approaching the Lesser Antilles Islands.

Jeff Masters

Hurricane

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September 2012 the 23rd warmest on record for the U.S.

By: JeffMasters, 4:25 PM GMT on October 09, 2012

September 2012 was the 23rd warmest September on record for the contiguous U.S, said NOAA's National Climatic Data Center (NCDC) in today's State of the Climate report. The month was also the driest on record for Montana, North Dakota, South Dakota, and Minnesota, and was a top-ten driest month for six surrounding states. The warm September temperatures helped make the year-to-date period of January - September the warmest such period on record for the contiguous U.S.--a remarkable 1.2°F above the previous record. Even if the remainder of 2012 ranks historically in the coldest one-third of October - Decembers on record, 2012 will beat out 1998 for the warmest year on record in the U.S. The first week of October has been one of the coldest weeks of the year, relative to average, with record cold lows outpacing record warm highs by a ratio of four-to-one in the contiguous U.S. However, next week will be warmer than average for the U.S., and it is highly unlikely that October 2012 will rank in the coldest one-third of Octobers on record. The October 2011-September 2012 period was the warmest such 12-month period on record for the contiguous U.S., and was the 3rd warmest 12-month period on record. The six warmest 12-month periods since record keeping began in 1895 have all ended during 2012.


Figure 1. Year-to-date temperatures for the contiguous U.S. through September, compared to the previous record warmest years in U.S. history. Outcome scenarios based on persistence of temperature from October through December, the remaining three months of 2012, are shown. Even if the remainder of 2012 ranks historically in the coldest one-third of October - Decembers on record (dark blue line), 2012 will beat out 1998 for the warmest year on record. The data for 2012 are preliminary. Image credit: NOAA/NCDC.

Most extreme January - September period on record
The year-to-date period was the most extreme in U.S. history, according to NOAA's U.S. Climate Extremes Index (CEI), which tracks the percentage area of the contiguous U.S. experiencing top-10% and bottom-10% extremes in temperature, precipitation, and drought. The CEI was 45% during the year-to-date January - September period. This is the highest value since CEI record-keeping began in 1910, and more than double the average value of 20%. Remarkably, 86% of the contiguous U.S. had maximum temperatures that were in the warmest 10% historically during the first nine months of 2012, and 79% of the U.S. of the U.S. had warm minimum temperatures in the top 10%. Both are records. The percentage area of the U.S. experiencing top-10% drought conditions was 24%, which was the 8th greatest since 1910.


Figure 2. NOAA's U.S. Climate Extremes Index (CEI) for January - September shows that 2012 had the most extreme first nine months of the year on record, with 45% of the contiguous U.S. experiencing top-10% extreme weather.

Jeff Masters

Climate Summaries

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98L may develop next week; 97L not a threat to land

By: JeffMasters, 1:59 PM GMT on October 09, 2012

A tropical wave located about 1000 miles east of the Lesser Antilles Islands (Invest 98L) has a large amount of disorganized heavy thunderstorms, and is headed west-northwest at about 15 mph. Wind shear is a light to moderate 5 - 15 knots over 98L, the atmosphere is moist, and ocean temperatures are a very warm 29°C. With wind shear expected to remain in the moderate range through Wednesday morning, some slow development is likely until 98L encounters much higher wind shear of 20 - 35 knots Wednesday night though Friday. This shear will be due to an upper-level trough of low pressure centered a few hundred miles northeast of the Lesser Antilles Islands. Moisture from 98L could arrive in the Lesser Antilles Islands as early as Thursday night. Wind shear may drop to levels capable of allowing 98L to develop into a tropical depression by Saturday, as predicted by the NOGAPS model. The GFS model predicts shear will remain high until early next week. The GFS develops 98L into a tropical depression on Tuesday, a few hundred miles northeast of the northernmost Lesser Antilles Islands. In their 8 am Tropical Weather Outlook, NHC gave 98L a 20% chance of becoming a tropical cyclone by Thursday morning. The long range fate of 98L is uncertain; the ECMWF model shows 98L coming close to the U.S. East Coast in ten or so days, while the other models keep 98L far out to sea.


Figure 1. Morning satellite image of Invest 98L headed towards the Lesser Antilles Islands.

97L near the Bahamas little threat to develop
A tropical disturbance a few hundred miles northeast of the Bahama Islands (Invest 97L) has a moderate amount of disorganized heavy thunderstorms, and is headed northeast at about 10 mph. Satellite loops show that heavy showers from 97L are affecting portions of the Southeast Bahama Islands, and this activity will continue today. Wind shear is a moderate 15 - 20 knots over 97L, but is expected to rise to the high range, 20 - 30 knots, on Tuesday night. This high shear should prevent 97L from developing as it heads northeastwards out to sea. In their 8 am Tropical Weather Outlook, NHC gave 97L a 10% chance of becoming a tropical cyclone by Thursday morning. Rains from 97L will not affect the U.S.

Jeff Masters

Hurricane

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Bahamas disturbance 97L little threat; 98L worth keeping an eye on

By: JeffMasters, 2:06 PM GMT on October 08, 2012

A tropical wave a few hundred miles northeast of the Bahama Islands (Invest 97L) has a moderate amount of disorganized heavy thunderstorms, and is headed northwest at 10 mph. Satellite loops show that heavy showers from 97L are affecting portions of the Bahama Islands, and this activity will continue through Tuesday. Wind shear is a moderate 10 - 20 knots over 97L, the atmosphere is moist, and ocean temperatures are a very warm 29.5°C. With wind shear expected to remain in the moderate range through Tuesday night, some slow development is possible today and Tuesday. However, by Wednesday, 97L will turn to the north and then northeast, encountering high wind shear of 20 - 40 knots. This high shear should be able to destroy 97L. In their 8 am Tropical Weather Outlook, NHC gave 97L a 10% chance of becoming a tropical cyclone by Wednesday morning. Rains from 97L will not affect the U.S.


Figure 1. Morning satellite image of Invest 97L just northeast of the Bahamas. Image credit: NOAA.

98L midway between Africa and Lesser Antilles
A tropical wave midway between Africa and the Lesser Antilles Islands (Invest 98L) has a moderate amount of disorganized heavy thunderstorms, and is headed west to west-northwest at 15 - 20 mph. Wind shear is a moderate 10 - 20 knots over 98L, the atmosphere is moist, and ocean temperatures are a very warm 29°C. With wind shear expected to remain in the moderate range through Tuesday night, some slow development is likely until 98L encounters much higher wind shear of 20 - 40 knots Wednesday though Saturday. Moisture from 98L could arrive in the Lesser Antilles Islands as early as Thursday, though Friday is more likely. On Monday, the GFS model predicts that wind shear will fall low enough for 98L to develop into a tropical depression a few hundred miles northeast of Puerto Rico. The NOGAPS model shows some weak support for this idea, but the ECMWF model does not. In their 8 am Tropical Weather Outlook, NHC gave 98L a 10% chance of becoming a tropical cyclone by Wednesday morning.

Jeff Masters

Hurricane

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El Niño falters

By: JeffMasters, 2:31 PM GMT on October 05, 2012

The progression of oceanic conditions in the Equatorial Eastern Pacific towards El Niño has been interrupted by a marked cooling over the past two weeks, and the onset of a full-fledged El Niño event this fall and winter is now in considerable doubt. Sea surface temperatures in the Equatorial Eastern Pacific were approximately 0.5°C above average--the threshold for a weak El Niño event--from the beginning of July through mid-September. However, for the past two weeks, these temperatures have fallen to just 0.2°C above average--solidly in the neutral category. In addition, over the past three months, winds, pressures, and cloud cover over the Pacific have not responded in the fashion typically associated with an El Niño (one exception: some stronger westerly surface winds than usual have developed near New Guinea and Indonesia, which could act to push warm water eastwards towards South America in coming months and tip the ocean more towards El Niño.) NOAA's Climate Prediction Center (CPC) classified conditions as being neutral in their monthly El Niño discussion, issued October 4, but continued their El Niño watch, giving a 55% chance that an El Niño event will be in place for the October-November-December period. This is a big reduction from 69% odds given in their September forecast. NOAA's final take on the matter:

Due to the recent slowdown in the development of El Niño, it is not clear whether a fully coupled El Niño will emerge. The majority of models indicate that borderline ENSO-neutral/ weak El Niño conditions will continue, and about half suggest that El Niño could develop, but remain weak. The official forecast therefore favors the continuation of borderline ENSO-neutral/ weak El Niño conditions into Northern Hemisphere winter 2012-13, with the possibility of strengthening during the next few months.

The lack of a progression towards El Niño so far this October means that the Atlantic hurricane season is likely to extend into November, as has been the norm over the past decade. El Niño events tend to increase wind shear over the tropical Atlantic, suppressing hurricane activity. However, the latest 2-week wind shear forecast from the GFS model shows continued near-average wind shear levels over the Caribbean and tropical Atlantic through mid-October. Given the recent faltering of El Niño, I expect that near-average wind shear levels will continue over the tropical Atlantic into November, and that we will see one or two more tropical storms in the Atlantic this hurricane season.


Figure 1. Departure of sea surface temperature (SST) from average between October 2011 and October 2012 in the Equatorial Eastern Pacific between 5°S - 5°N, 170°W - 120°W (the Niño 3.4 region.) A La Niña episode occurs when SSTs in the Niño 3.4 region are 0.5°C cooler than average for an extended period (below the thick blue line.) La Niña conditions were in place between October 2011 - March 2012. El Niño conditions occur when SSTs in the El Niño 3.4 region are more than 0.5°C warmer than average (above the thick red line.) El Niño conditions developed in early July, but have fallen below the threshold for a weak El Niño event over the past two weeks. Image credit: NOAA's Climate Prediction Center (CPC).

Oscar about to meet its Waterloo
Tropical Storm Oscar continues to battle high wind shear, which has exposed the low-level center to view and pushed all of the storm's heavy thunderstorms well away from the center of circulation, to the storm's southeast side. Satellite images show a cold front attached to a large extratropical storm is closing in on Oscar, and this front will overtake Oscar Friday night and absorb the storm by Saturday morning. Oscar is a classic example of a weak, short-lived tropical cyclone that would have gotten missed before satellites came around.


Figure 2. Morning satellite image of Tropical Storm Oscar. It's looking none too healthy, with the low-level circulation exposed to view, and a cold front to the north beginning to overtake it.

Elsewhere in the Atlantic
None of the computers is predicting development of a new tropical cyclone over the Atlantic in the coming seven days. Beginning on Tuesday, we will need to watch the waters between the Bahama Islands and Bermuda, where the remains of a cold front pushing off the U.S. East Coast may serve as the focal point for development of a tropical disturbance.

Have a great weekend, everyone, and I'll be back on Monday at the latest with a new post.

Jeff Masters

Hurricane Climate Summaries

Updated: 4:39 PM GMT on October 05, 2012

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You only die twice: Atlantic's 2nd longest TS of all-time is dead

By: JeffMasters, 3:14 PM GMT on October 04, 2012

The interminable, long-lived, pesky, persistent, perpetual, never-say-day, tenacious, non-stop, I'm-not-dead-yet, Energizer-bunny-like Methuselah of Atlantic tropical cyclones, Tropical Storm Nadine, finally met its permanent doom this morning, but not before bringing tropical storm conditions to the northwest Azores Islands. Sustained winds of 43 mph, gusting to 54 mph, were recorded at Lajes at 8 am local time, as Nadine was completing its transition to an extratropical storm. Today is Nadine's 2nd death; the storm also became extratropical for just over a day on September 22. Nadine logged 21.75 days as a tropical or subtropical cyclone as of 2 am today, making it the fifth longest-lived Atlantic tropical cyclone of all-time (tropical cyclones include tropical depressions, tropical storms, and hurricanes, but not extratropical storms.) Nadine's 21.25 days as a tropical or subtropical storm make it tied with Hurricane Ginger of 1971 as the Atlantic's second longest tropical storm on record. Only the San Ciriaco Hurricane of 1899 (28 days) was longer-lived. About one-quarter of this year's total Accumulated Cyclone Energy (ACE) in the Atlantic basin so far is due to Nadine. According to the official HURDAT Atlantic database, which goes back to 1851, here are the four previous Atlantic tropical cyclones have lasted longer than Nadine (thanks go to Brian McNoldy for these stats):

1) San Ciriaco Hurricane of 1899: 28 days
2) Ginger, 1971: 27.25 days
3) Inga, 1969: 24.75 days
4) Kyle, 2002: 22 days
5) Nadine, 2012: 21.75 days

The National Hurricane Center issued 88 advisories on Nadine, and lucky NHC hurricane specialist Lixion Avila got to write the final epitaph in today's 11 am EDT advisory: "Bye bye Nadine...what a long strange trip its been." See you again in 2018, Nadine.


Figure 1. MODIS satellite image of Hurricane Nadine taken at 11:35 am EDT September 30, 2012. At the time, Nadine was at peak strength, with top winds of 90 mph. Image credit: NASA.

Oscar becomes the 15th named storm of 2012
The first new tropical storm in the Atlantic since September 12 is Tropical Storm Oscar, which was upgraded to a 40 mph tropical storm on Wednesday night. Oscar won't be around very long, and will not be a threat to any land areas. The storm is already suffering significantly from moderate wind shear of 15 - 20 knots, which has exposed the low-level center to view, and pushed all of Oscar's heavy thunderstorms well away from the center of circulation, to the storm's east side. Wind shear is expected to rise to a high 20 - 25 knots tonight, and ocean temperatures will cool from 28°C today to 27°C by Friday. All of the computer models show Oscar ceasing to exist by Saturday, as the storm becomes absorbed by a cold front attached to a large extratropical storm. Oscar is a classic example of a weak, short-lived tropical cyclone that would have gotten missed before satellites came around. Oscar's formation brings this year's tally of named storms to fifteen, tying 2012 for 11th place for most tropical storms in a year. This puts 2012 in the top 10% of busiest Atlantic hurricane seasons for number of storms, since record keeping began in 1851. Despite the large number of named storms this year, we've had a pretty average number of strong hurricanes, so this year's Accumulated Cyclone Energy (ACE) is only about 20% higher than average for this time of year.


Figure 2. Morning satellite image of Tropical Storm Oscar.

Elsewhere in the Atlantic
None of the computers is predicting development of a new tropical cyclone over the Atlantic in the coming seven days. We will need to watch the waters between the Bahama Islands and Bermuda early next week, though, where the tail end of a cold front pushing off the U.S. East Coast may serve as the focal point for development of a tropical disturbance.

Jeff Masters

Hurricane

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TD 15 forms; tropical storm warnings in the Azores for Nadine

By: JeffMasters, 4:12 PM GMT on October 03, 2012

The first new tropical depression in the Atlantic since September 11 is here, Tropical Depression Fifteen. TD 15 is destined for a short life, though, and will not be a threat to any land areas. The storm is already showing signs that moderate wind shear of 10 - 20 knots is interfering with development, with most of the storm's heavy thunderstorms displaced away from the center of circulation. Wind shear is expected to rise to the high range, above 20 knots, on Thursday and Friday as the storm turns north and then northeast. Ocean temperatures will cool from 28°C today to 25°C by Saturday, and all of the computer models show TD 15 ceasing to exist by Saturday, as the storm becomes absorbed by a large extratropical storm. TD 15 is a classic example of a weak, short-lived tropical cyclone that would have gotten missed before satellites came around. If TD 15 strengthens, it will be called Tropical Storm Oscar.


Figure 1. MODIS satellite image of TD 15 taken at 8:52 am EDT Wednesday, October 3, 2012. At the time, TD 15 was just forming and had top winds of 35 mph. Image credit: Navy Research Lab, Monterey.

Nadine touring the Azores Islands--again
I'm-not-dead-yet Tropical Storm Nadine is back for a second tour of the Azores Islands, where tropical storm warnings are up for the storm's expected arrival tonight. Nadine is struggling with cool 21 - 22°C waters and high wind shear of 20 - 30 knots, and could transition to an extratropical storm later today or on Thursday as it heads east at 14 mph. Nadine is up to 21 days as a tropical or subtropical cyclone as of 2 pm today, making it the fifth longest-lived Atlantic tropical cyclone of all-time (tropical cyclones include tropical depressions, tropical storms, and hurricanes, but not extratropical storms.) According to the official HURDAT Atlantic database, which goes back to 1851, only five previous Atlantic tropical cyclones have lasted 21 days or longer (thanks go to Brian McNoldy for these stats):

1) San Ciriaco Hurricane of 1899: 28 days
2) Ginger, 1971: 27.25 days
3) Inga, 1969: 24.75 days
4) Kyle, 2002: 22 days
5) Nadine, 2012: 21 days
5) Hurricane Four, 1926: 21 days

According to the Hurricane FAQ, the all-time world record is held by Hurricane John in the Eastern Pacific, which lasted 31 days as it traveled both the Northeast and Northwest Pacific basins during August and September 1994. (It formed in the Northeast Pacific, reached hurricane force there, moved across the dateline and was renamed Typhoon John, and then finally recurved back across the dateline and renamed Hurricane John again.) Of course, there may have been some longer-lived storms prior to 1961 that we didn't observe, due to the lack of satellite data.


Figure 2. MODIS satellite image of Hurricane Nadine taken at 8:45 am EDT Wednesday, October 3, 2012. At the time, Nadine had top winds of 50 mph. Image credit: NASA.

Jeff Masters

Hurricane

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Major U.S. Winter Storms to get names

By: JeffMasters, 1:50 PM GMT on October 02, 2012

October is here, and its time to start thinking about how the coming winter's storm might compare to mighty blizzards of years past. Do you remember the North American blizzard of February 4, 2010? No? Well, do you remember Snowmageddon, the massive February 2010 Nor'easter that dumped up to 38" of snow in the mid-Atlantic, and killed 41 people? The two storms are the same, but having a simple name for the snowstorm like "Snowmageddon" helps us identify and remember the impacts of the storm. Naming a major winter storm makes even more sense if it is done before the storm hits, to aid in raising awareness of the storm, and to reduce the risks the public faces. That's exactly what The Weather Channel is going to do for the U.S. this winter, they announced in a press release today. A group of senior meteorologists at The Weather Channel chose 26 names for the upcoming winter of 2012 - 2013. The only criteria was to select names that are not and have never been on any of the hurricane lists produced by the National Hurricane Center or National Weather Service. Naming of a winter storm will occur no earlier than three days prior to it hitting, to ensure there is strong confidence that the system could have significant impact on large populations. There is no national center for monitoring winter storms like we have for hurricanes with the National Hurricane Center, so I think it makes sense for The Weather Channel to take this step.


Figure 1. Snowmageddon in Maryland: February 4, 2010. Image credit: wunderphotographer chills.

U.S. winter storm names for winter of 2012 - 2013
Athena -- The Greek goddess of wisdom, courage, inspirations, justice, mathematics and all things wonderful

Brutus -- Roman Senator and best known assassin of Julius
Caesar -- Title used by Roman and Byzantine Emperors 

Draco -- The first legislator of Athens in Ancient
Euclid -- A mathematician in Ancient Greece, the Father of Geometry
Freyr -- A Norse god associated with fair weather, among other things

Gandolf -- A character in a 1896 fantasy novel in a pseudo-medieval countryside

Helen – In Greek mythology, Helen of Troy was the daughter of Zeus

Iago -- Enemy of Othello in Shakespeare’s play, Othello

Jove -- The English name for Jupiter, the Roman god of light and sky.

Kahn -- Mongolian conqueror and emperor of the Mongol Empire

Luna -- The divine embodiment of the moon in Roman mythology

Magnus -- The Father of Europe, Charlemagne the Great, in Latin: Carolus Magnus 

Nemo -- A Greek boy’s name meaning “from the valley”, means “nobody” in Latin 

Orko -- The thunder god in Basque mythology

Plato -- Greek philosopher and mathematician, who was named by his wrestling coach

Q -- The Broadway Express subway line in New York City

Rocky -- A single mountain in the Rockies

Saturn -- Roman god of time, among other things who had a planet named after him

Triton -- In Greek mythology, the messenger of the deep sea, son of Poseidon

Ukko -- In Finnish mythology, the god of the sky and weather

Virgil -- One of ancient Rome’s greatest poets

Walda -- Name from Old German meaning “ruler”

Xerxes -- The fourth king of the Persian Achaemenid Empire, Xerxes the Great

Yogi -- People who do yoga

Zeus -- In Greek mythology, the supreme ruler of Mount Olympus and the gods who lived there

I expect that this year The Weather Channel will be pretty conservative about assigning names, and only the very strongest winter storms will get named. For the eastern 2/3 of the country, storms that receive a ranking of "notable" or higher on NOAA's Regional Snowfall Index (RSI) or Northeast Snowfall Impact Scale (NESIS) are the only ones fairly certain to get named this winter. We only had one such storm during the winter of 2011 - 2012 (Snowtober, on October 29 - 31, 2011.) Thus, if we have another wimpy winter like last winter, we probably won't get to see the Wrath of Khan.

Naming of Winter Storms in Europe
Various organizations in Europe have been naming their winter storms since 1954, and the public has reacted positively to this practice. The names given by the Free University of Berlin are the most widely used, and have been in existence since 1954. Their meteorologists traditionally name all lows and highs that influence the Central European weather. In November 2002, the Free University began an Adopt-a-Vortex scheme, which allows anyone to buy a storm name. The money raised is used by the meteorology department to maintain weather observations at the university. Over 1,800 participants from 15 European countries plus Brazil, Japan and the United States have participated. So far in 2012, 90 European low pressure systems have been given names.


Figure 2. A huge wave from Winter Storm Klaus rolls into Santander, Spain, in this wunderphoto taken by wunderphotographer lunada on January 24, 2009. Klaus had a central pressure of 967 mb at its peak on the morning of January 24, and brought sustained winds of 59 mph, gusting to 81 mph, to Santander. Wind gusts as high as 124 mph (199 km/hr) occurred along the northern coast of Spain, and the storm killed at least 26 people in Spain, France, and Italy.

Naming of Lake Effect Winter Storms by NWS Buffalo
Tom Niziol, The Weather Channel's winter storm expert, was meteorologist-in-charge of the Buffalo, New York NWS office until January 2012. He tells me that for over ten years, the Buffalo NWS has been naming lake-effect storms. This was done only after the event occurred, to avoid any confusion, but was very popular with users. The names were chosen on a yearly basis by having the office staff vote for one of several themes--such as insects, heavenly bodies, famous scientists, minerals, Native American tribes, etc. Last winter, eight storms were named after breeds of cows (?!), as seen at the NWS Buffalo Lake Effect web page. I was not asked to contribute to this year's list of U.S. winter storms, but will lobby for next year's list of names to be taken from famous monsters--Rodan, Ghidorah, Nessie, Kong, Bunnicula, etc.


Figure 3. The most significant lake-effect snow storm of the winter of 2011 - 2012 was named Lake Effect Storm Evolene by the NWS office in Buffalo, New York. Image credit: NWS Buffalo Lake Effect web page.

Nadine
The Methuselah of Atlantic tropical storms, Tropical Storm Nadine, is slowly weakening over cool 22 - 24°C waters. Nadine will have accumulated 20 days as a tropical cyclone later today, but the end is in sight. Wind shear will rise to 30 knots and ocean temperatures will drop to 20°C by Thursday, which should cause Nadine to transition to an extratropical storm as it passes by the northern Azores Islands on Thursday and Friday.

96L off the coast of Africa no threat to land
A tropical wave that emerged off the coast of Africa over the weekend (Invest 96L) has a moderate amount of spin and a large area of heavy thunderstorms that is growing more organized. The storm is located about 925 miles west of the Cape Verde Islands, and is headed northwest at 10 - 15 mph. Wind shear is a moderate 10 knots, and is predicted to remain light to moderate, 5 - 15 knots, through Friday. The atmosphere surrounding 96L is fairly moist, and the disturbance does have a good degree of model support for becoming a tropical depression by late in the week. In their 8 am EDT Tropical Weather Outlook, NHC gave 96L a 70% chance of becoming a tropical depression by Thursday morning. 96L is likely to get pulled northwards by a large trough of low pressure over the Central Atlantic late this week, and should not be a threat to the Lesser Antilles Islands.

Jeff Masters

Winter Weather

Updated: 6:28 PM GMT on October 02, 2012

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End in sight for Nadine; 96L no threat to land

By: JeffMasters, 3:05 PM GMT on October 01, 2012

Never-ending Tropical Storm Nadine hit its peak intensity of 90 mph on Sunday afternoon, but is now steadily weakening as it encounters cool 22 - 23°C waters. Nadine is responsible for these cool waters, as the storm passed over the same location earlier in its life and mixed the cool waters to the surface. Nadine will have accumulated 19 days as a tropical cyclone later today, but the end is in sight. Nadine will be over waters no warmer than 24°C this week, and wind shear will increase to 30 knots by Wednesday. The HWRF model shows Nadine dissipating on Thursday as it moves through the Azores Islands; the ECMWF model predicts that Nadine will pass through the Azores on Thursday as a minimum-strength tropical storm with 40 mph winds, then dissipate on Friday. If Nadine lasts until Wednesday evening, it will become one of the five longest-lived Atlantic tropical cyclones of all-time. Tropical cyclones include tropical depressions, tropical storms, and hurricanes, but not extratropical storms; I am counting Nadine's 24-hour stint as a subtropical storm as it being a tropical cyclone.) According to the official HURDAT Atlantic database, which goes back to 1851, only five Atlantic tropical cyclones have lasted 21 days or longer (thanks go to Brian McNoldy for these stats):

1) San Ciriaco Hurricane of 1899: 28 days
2) Ginger, 1971: 27.25 days
3) Inga, 1969: 24.75 days
4) Kyle, 2002: 22 days
5) Hurricane Four, 1926: 21 days

According to the Hurricane FAQ, the all-time world record is held by Hurricane John in the Eastern Pacific, which lasted 31 days as it traveled both the Northeast and Northwest Pacific basins during August and September 1994. (It formed in the Northeast Pacific, reached hurricane force there, moved across the dateline and was renamed Typhoon John, and then finally recurved back across the dateline and renamed Hurricane John again.) Of course, there may have been some longer-lived storms prior to 1961 that we didn't observe, due to the lack of satellite data.


Figure 1. MODIS satellite image of Hurricane Nadine taken at 11:53 am EDT Sunday, September 30, 2012. At the time, Nadine was at peak strength, with top winds of 90 mph. Image credit: Navy Research Lab, Monterey.

96L off the coast of Africa no threat to land
A tropical wave that emerged off the coast of Africa over the weekend (Invest 96L) has a moderate amount of spin and a small area of disorganized heavy thunderstorms. The storm is located about 500 miles southwest of the Cape Verde Islands, and is headed west-northwest at 10 - 15 mph. Wind shear is a moderate 10 knots, and is predicted to remain light to moderate, 5 - 15 knots, through Friday. The atmosphere surrounding 96L is fairly moist, and the disturbance does have a good degree of model support for becoming a tropical depression by late in the week. In their 8 am EDT Tropical Weather Outlook, NHC gave 96L a 30% chance of becoming a tropical depression by Wednesday morning. 96L is likely to get pulled northwards by a large trough of low pressure over the Central Atlantic late this week, and should not be a threat to the Lesser Antilles Islands.

Jeff Masters

Hurricane

Updated: 3:12 PM GMT on October 01, 2012

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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