Category 6™

CYGNSS Micro Satellites Usher in New Era in Ocean Wind Measurements

By: Jeff Masters , 2:45 PM GMT on January 30, 2017

A new era in measuring hurricane winds began on December 15, 2016, when a Pegasus XL rocket launched by Stargazer—Orbital ATK’s L-1011 carrier aircraft—put into orbit a constellation of eight micro-satellites, the core of a NASA mission called CYGNSS (Cyclone Global Navigation Satellite System). Each CYGNSS micro-satellite uses less power than a 50-watt light bulb, weighs about 64 pounds, and is the size of a full-grown swan when the solar panels are extended. Each satellite is equipped with a scatterometer-like device called a Delay Doppler Mapping Instrument (DDMI). This instrument studies Global Positioning System (GPS) signals emitted by the existing constellation of 30 GPS satellites in medium Earth orbit when these signals are reflected off of the ocean (each CYGNSS satellite works with four GPS satellites at a time.) The amount of scattering of the GPS signals is related to the wind speed at the surface, allowing the CYGNSS satellites to measure the surface wind speed. GPS signals are not affected by heavy rain, which will allow CYGNSS to measure winds in hurricane eyewalls—something a previous scatterometer instrument, QuikSCAT, could not reliably do.


Figure 1. A NASA depiction of one of the CYGNSS satellites.

The CYGNSS satellite constellation joins the European Space Agency’s two ASCAT instruments, launched in 2007, as the only space-borne scatterometer instruments for measuring surface winds. The RapidScat instrument, which was mounted on the International Space Station, failed in December 2016, and QuikScat has been dead since 2009. There are other spaceborne sensors that can measure winds using passive microwave methods (e.g. SSM/I, WindSat, GMI), but measurement from these sensors are subject to interference from rain, and are not as useful in a hurricane environment. Both CYGNSS and ASCAT have the same resolution, 25 km, but the eight CYGNSS satellites allow for much better coverage of the globe than a single satellite, since the eight satellites will pass over the ocean more frequently than a single satellite would. The complete constellation provides nearly gap-free coverage with an average revisit time of seven hours over the prime hurricane breeding grounds between 35 degrees north and south latitude (as far north as North Carolina and as far south as southern Australia.) The CYGNSS satellites fly in Low Earth Orbit at an altitude of about 300 miles and cannot see poleward of 38.5 degrees of latitude. ASCAT measures global winds only twice per day along two parallel swaths 550 km wide, separated by a 720 km gap. This means that ASCAT passes miss the center of circulation of a hurricane more than half the time. However, ASCAT is in polar orbit and can see the entire globe.

CYNGSS costs about $157 million, and is designed to operate for a minimum of two years. The price is relatively cheap for a weather satellite; the highly advanced Geostationary Operational Environmental Satellite-R (GOES-R) is part of a weather and solar activity monitoring program estimated to cost $11 billion. However, funding does not currently exist to provide the CYGNSS data in near real time to hurricane forecasters; up to a six day lag is anticipated between the time a measurement is taken and when the final data is processed and made available. Thus, CYGNSS is a proof-of-concept research mission intended to pave the way for future operational missions that can provide real-time wind data to hurricane forecasters. According to lead mission scientist Dr. Chris Ruf of the University of Michigan’s Climate and Space Sciences and Engineering Program, “discussions have started with NOAA about possibly supplementing our current data downlinks to improve data latency. So we might not have to wait for another mission. But this is still to be determined.”


Figure 2. Flying over the Atlantic Ocean offshore from Daytona Beach, Florida, a Pegasus XL rocket with eight Cyclone Global Navigation Satellite System, or CYGNSS, spacecraft was released from the Orbital ATK L-1011 Stargazer aircraft and the first stage ignited at 8:37 a.m. EST December 15, 2016. Image credit: NASA.

Scatterometer data: a valuable tool for hurricane forecasters
Scatterometer data are extremely valuable for many aspects of hurricane forecasting. It makes intensity estimates more accurate, provides early detection of surface circulations in developing tropical depressions, and helps define gale (34 kts, minimal tropical storm strength) and storm-force (50 kts) wind radii. The information on wind radii from scatterometer data is especially important for tropical storms and hurricanes outside the range of aircraft reconnaissance flights conducted in the Atlantic and Eastern Pacific basins, and for the regions where there are no reconnaissance flights (Central Pacific, Western Pacific, and Indian Ocean). Accurate wind radii are critical to the National Hurricane Center (NHC), Central Pacific Hurricane Center (CPHC), and Guam Weather Forecast Office (WFO) watch and warning process, since they affect the size of tropical storm and hurricane watch and warning areas. Between 2003 and 2006, QuikSCAT data were used at NHC 17% of the time to determine the wind radii, 21% of the time for center fixing, and 62% of the time for storm intensity estimates.

While there is evidence that satellite scatterometer data improves hurricane track forecasts of some computer models, data from CYGNSS may not significantly improve official hurricane track forecasts from NHC, though. NHC uses many models to make hurricane track forecasts, and some of these models may not be helped by scatterometer data. For example, a 2009 model study by Dr. Jim Goerss of the Naval Research Lab found that QuikSCAT winds made no improvement to hurricane track forecasts of the NOGAPS model, one of the key models used by NHC to predict hurricane tracks. Former National Hurricane Center director Bill Proenza laudably made a big push in 2007 for a replacement of the failing QuikSCAT satellite, but unfortunately made claims about the usefulness of QuikSCAT for improving hurricane track forecasts that were not supported by scientific research, an error that may have ultimately led to his downfall.

We'll have a new post on Wednesday.

Jeff Masters

Hurricane Satellites

Updated: 8:19 PM GMT on February 04, 2017

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"Dante's Inferno" in Chile: All-Time National Heat Record Smashed by 6°F

By: Jeff Masters , 3:28 PM GMT on January 27, 2017

The first all-time national heat record of 2017 was set in spectacular fashion on Thursday in Chile, where at least twelve different stations recorded a temperature in excess of the nation’s previous all-time heat record—a 41.6°C (106.9°F) reading at Los Angeles on February 9, 1944. According to international weather records researcher Maximiliano Herrera, the hottest station on Thursday was Cauquenes, which hit 45.0°C (113°F). The margin by which the old record national heat record was smashed: 3.6°C (6.1°F), was extraordinary, and was the second largest such difference Herrera has cataloged (the largest: a 3.8°C margin in New Zealand in 1973, from 38.6°C to 42.4°C.) Herrera cautioned, though, that the extraordinary high temperatures on Thursday in Chile could have been due, in part, to the effects of the severe wildfires burning near the hottest areas, and the new record will need to be verified by the weather service of Chile.


Figure 1. Fires (red squares) in Chile spread smoke over the Pacific Ocean, as seen at 10:35 am EST Thursday January 26, 2017. This MODIS image is from NASA’s Terra satellite.

Here are some of the high temperatures from January 26 in Chile:

Maule Region (near the area affected by wildfires):

Cauquenes, 45.0°C
Coronel de Maule, 41.8°C
Los Despachos, 42.8°C
Santa Sofia, 43.1°C
Sauzal, 41.8°C

Maule Region (outside the area affected by wildfires):

Linares, 41.8°C
Longavi Sur, 42.3°C
Parral, 40.8°C

Bio Bio Region (near the area affected by wildfires):

Bulnes, 42.5°C
Quillon, 44.9°C
Ninhue, 43.0°C

Bio Bio Region (outside the area affected by wildfires):

Portezuelo, 41.2°C
Chillan, 41.4°C (DMC station)
Chillán Quinchamalí, 43.0°C
San Nicolas, 41.1°C
Los Angeles Maria Dolores Airport, 42.2°C


Figure 2. Smoke settles over Santiago, Chile on January 20, 2017. Chile has endured weeks of extreme heat that has smashed numerous heat records, with Pudahuel Airport in western Santiago on January 20 hitting the hottest temperature ever recorded in the Santiago metropolitan area: 37.7°C (99.9°F). Santiago Observatory (with records back to 1866) set its all-time heat record on January 25, 2017 with 37.4°C, and Quinta Normal Observatory broke its all-time heat record in December 2016, with a reading of 37.3°C, beating a record that had stood 101 years. Image credit: Martin Bernetti/AFP/Getty Images.

Record heat and extreme drought lead to deadly Chile wildfires
Record heat and extreme drought in Chile are contributing to their worst wildfires in decades. On Thursday, the entire town of Santa Olga was destroyed by fire, with more than 1,000 building consumed including schools, nurseries, shops and a post office. As reported in The Guardian, Carlos Valenzuela, the mayor of the region, said: “Nobody can imagine what happened in Santa Olga. What we have experienced here is literally like Dante’s Inferno.” Authorities declared a state of emergency in Chile due to wildfires on January 20, and as of January 26, more than 100 fires were burning throughout O’Higgins and Maule regions. At least ten people have been killed by the fires, including four firefighters and two policemen. According to insurance broker Aon Benfield, the fires had consumed 578,000 acres of land as of January 26, and damages to the timber industry alone were estimated at $40 million. Hot, dry weather with high temperatures in the 90s are expected to continue for the next week in the Santiago area.

Chile's ongoing megadrought partially attributed to human-caused climate change
Central Chile is enduring a decades-long megadrought that began in the late 1970s, with precipitation declines of about 7% per decade. According to a 2016 study by Boisier et al., "Anthropogenic and natural contributions to the Southeast Pacific precipitation decline and recent megadrought in central Chile", this drought is unprecedented in historical records. While at least half of the change in precipitation can be blamed on natural causes, primarily due to atmospheric circulation changes from the Pacific Decadal Oscillation, the authors estimated that a quarter of the rainfall deficit affecting this region since 2010 was due to human-caused climate change.

Jeff Masters

Heat Fire

Updated: 4:50 PM GMT on January 27, 2017

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Will Global Warming Make Hurricane Forecasting More Difficult?

By: Jeff Masters , 3:29 PM GMT on January 25, 2017

Will Global Warming Make Hurricane Forecasting More Difficult? That’s the title and provocative premise of a new paper by MIT hurricane scientist Kerry Emanuel (early online PDF available here from the Bulletin of the American Meteorological Society.) Dr. Emanuel makes the case that the most dangerous storms—tropical cyclones that intensify rapidly just before landfall, catching forecasters and populations off guard, thereby risking large casualties—are likely to become increasingly frequent and severe as the globe warms, increasing from one such storm every 100 years to one every 5 - 10 years.




Figure 1. Since 1900, 56% of all U.S. deaths from tropical cyclones have been caused by the three storms shown above.

Tropical cyclone mortality dominated by a small number of events
Since 1971, tropical cyclones (which include all hurricanes, typhoons, tropical storms, and tropical depressions) have killed 470,000 people (about 10,000 per year) and caused $700 billion in damage, according to the international disaster database, EM-DAT. Most of these deaths were caused by just a few storms—for example, three Atlantic hurricanes (the Great Galveston Hurricane of 1900, the 1928 Lake Okeechobee hurricane, and Hurricane Katrina of 2005)—caused 56% of all U.S. hurricane deaths since 1900.

Increased vulnerability due to growing coastal populations
In recent years, better tropical cyclones forecasts have resulted in reduced death tolls and lower damages than would otherwise have occurred. However, a large increase in coastal population resulted in an almost three-fold increase in the global population exposed to tropical cyclone hazards between 1970 and 2010 (Peduzza et al., 2012.) This helped fuel an increase in tropical cyclone damages of about 6% per year between 1970 and 2015, according to EM-DAT. Thus, much improved forecasts and/or major reductions in vulnerability though better preparedness and building codes are needed to avoid increasing tropical cyclone death tolls in the coming decades.

Poor intensity forecasts make us vulnerable
While track forecasts of hurricanes have improved by more than a factor of two over the past 20 years, intensity forecasts have shown little improvement. Dr. Emanuel gives four reasons for this:

1) Very high resolution computer models are needed (1 km resolution or better), which are beyond the capability of modern computers to run economically.

2) We have poor understanding of and models of the processes in the lowest few hundred meters of the atmosphere (the boundary layer).

3) We have difficulty modeling how the top few hundred meters of the ocean responds to a storm.

4) The process of taking observations that show a dramatic variation over short distances and correctly initializing a hurricane model with these observations is difficult.

The 2016 hurricane season gave us two humbling examples of how far we still have to go with intensity forecasts. As Hurricane Matthew drifted across the southern Caribbean Sea in late September, the hurricane rocketed in strength from Category 1 to Category 5 in just 24 hours (from 80 mph sustained winds at 03Z on September 30 to 160 mph at 03Z on October 1). The official NHC forecast at the start of this day-long burst was for Matthew to take three days to top out at high-end Category 2 strength (105 mph). Less dramatic but still eye-opening was Nicole’s surge from Category 1 to Category 4 strength in the Northwest Atlantic over just 21 hours (from 90 mph sustained winds at 06Z on October 12 to 135 mph at 03Z on October 13). Like Matthew, Nicole had also been predicted at the start of its rapid strengthening to remain just below the major hurricane threshold (Category 3). Dr. Emanuel gives an additional troubling example of a rapid intensification evert that was poorly forecasted: Hurricane Patricia of October 2015, which hit a relatively unpopulated portion of the Pacific coast of Mexico as a Category 4 storm with 150 mph winds after topping out as the strongest tropical cyclone ever measured—215 mph sustained winds. During a 24-hour period from October 22 at 06 GMT to October 23 at 06 GMT, Patricia intensified by an astonishing 120 mph—from an 85 mph Category 1 storm to a 205 mph Category 5 storm. During this same period, the National Hurricane Center predicted an intensification by only 35 mph. Dr. Emanuel notes, “Had the storm made landfall at the end of this period of rapid intensification, the result could have been catastrophic given the poor anticipation of the magnitude of the event.” 


Quantifying the probability of rapid intensification just before landfall
Quantifying the probability of rapid intensification just before landfall is difficult using the existing database of global tropical cyclones, which goes back about 60 years in the Atlantic, but only 35 - 45 years in the Southern Hemisphere. Since Dr. Emanuel’s study was interested in rare storms that have a return period of about once every 100 years, a computer model was used. The model generated a set of 22,000 landfalling U.S. hurricanes during the recent climate period of 1979 - 2005, and looked at storms that rapidly intensified just before landfall. The analysis found that about once per century, we should expect to see a hurricane that intensifies by 70 mph or greater in the 24 hours just before landfall. The major metropolitan areas most at risk for surprise intensification just before landfall included Houston, New Orleans, Tampa/St. Petersburg, and Miami.

Hurricanes are heat engines that take heat energy out of the oceans and convert it to the mechanical energy of wind. Thus, hurricane scientists are in broad agreement that global warming should make the strongest hurricanes stronger. The computer modeling results of Dr. Emanuel also found that global warming under a business-as-usual scenario would result in more cases of rapidly intensifying hurricanes making landfall in the United States. The odds of a hurricane that intensified by 70 mph or greater in the 24 hours just before landfall increased from once every 100 years to once every 5 - 10 years by the year 2100 in his simulations. What’s more, 24-hour pre-landfall intensifications of 115 mph or more—which were essentially nonexistent in the late 20th Century simulations—occurred as often as once every 100 years by the year 2100. With increasing coastal populations, limited skill in intensity forecasting, and steadily increasing sea levels, this potential increase in rapidly intensifying hurricanes results in the “risk of an increased frequency of poorly anticipated high-intensity landfalls leading to higher rates of injury and death,” wrote Dr. Emanuel. He recommended that “greater emphasis be placed on improving hurricane intensity prediction and on preparing populations to respond to high intensity landfalling hurricanes at short notice.”


Links
Top Ten Tropical Cyclone Events of 2016 Potentially Influenced by Climate Change (my December 2016 blog post)
Hurricane Patricia's 215 mph Winds: A Warning Shot Across Our Bow (my 2016 blog post)
Fewer but Stronger Global Tropical Cyclones Due to Ocean Warming (my 2015 blog post)
Hurricanes and Climate Change: Huge Dangers, Huge Unknowns (my 2013 blog post)
Climatesignals.org analysis of Hurricane Matthew

Hurricane Patricia Cat-5 fix

Check out this incredible footage of our flight through the eye of Category 5 Hurricane #Patricia off the coast of Mexico. The video was taken from the flight station of #NOAA43 (#NOAA P-3) and provided by Lt. Cmdr. Scott Price (the missions's Aircraft Commander). The video begins inside the eyewall: note that the intense rain and wind combination makes it impossible to see the nose of the aircraft just a few feet away. At 37 seconds, the crew enters the eye of the #Hurricane, where the violent sea-state below becomes visible. Note that due to the storm's incredibly steep gradient, the aircraft is pitched downward as the aircraft descends closer to the ocean. At 57 seconds, the curved eyewall on the opposite side of this very small eye becomes apparent. After a couple of slight turns requested by the Flight Meteorologist to report the exact center of the storm, the crew turns right to avoid the worst of the eyewall. At ~2 minutes into the video, the aircraft reaches the opposite eyewall where the crew loses visibility once again.

Posted by The NOAA Hurricane Hunters on Thursday, November 5, 2015


Video 1. Incredible footage taken during the flight of NOAA hurricane hunter aircraft N43RF through the eye of Category 5 Hurricane Patricia on the afternoon of October 23, 2015, when the storm was near peak strength, with 205 mph sustained surface winds and a central pressure of 878 mb. Lt. Cmdr. Scott Price (the mission's Aircraft Commander) made the video using a GoPro camera. The video begins inside the eyewall: note that the intense rain and wind combination makes it impossible to see the nose of the aircraft just a few feet away. Since the aircraft is flying perpendicular to the wind in order to find the center, the rainfall is blowing from left to right in front of the pilot's vision. At 37 seconds, the crew enters the eye of the hurricane, where the violent sea-state below becomes visible. Note that due to the storm's incredibly steep pressure gradient, the aircraft is pitched downward as the aircraft descends closer to the ocean, in order to keep flying at a constant pressure altitude. At 57 seconds, the curved eyewall on the opposite side of this very small eye becomes apparent. After a couple of slight turns requested by the Flight Meteorologist to report the exact center of the storm, the crew turns right to avoid the worst of the eyewall. At ~2 minutes into the video, the aircraft reaches the opposite eyewall where the crew loses visibility once again. Posted by The NOAA Hurricane Hunters on Thursday, November 5, 2015.

Jeff Masters

Hurricane Climate Change

Updated: 7:29 AM GMT on January 26, 2017

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At Least 18 Killed in Midwinter Tornado Outbreak

By: Bob Henson , 1:27 PM GMT on January 23, 2017

After the least-deadly year for U.S. tornadoes in three decades, 2017 is off to a troublesome start. At least 18 people died over the weekend in two consecutive nights of tornadoes across the Deep South, compared to the total of 17 fatalities recorded for the entire year of 2016. Although midwinter outbreaks don’t happen every year in the United States, they’re most likely to be across the South when they do occur. Many of the deadliest tornadoes in these outbreaks happen overnight, when residents may be caught asleep or otherwise unaware and when getting to shelter can be difficult. The high proportion of manufactured/mobile homes across the South adds to the vulnerability of residents.


Figure 1. Among the structures damaged by a tornado that moved through Albany, GA, on Sunday, Jan. 22, 2017, was this gas station. Image credit: AP Photo/Branden Camp.


Figure 2. Winds at jet-stream level (250 mb, or about 34,000 feet) show a strong upper-level trough over the lower Mississippi Valley at 7:00 pm EST Sunday, Jan. 22, 2017 (00Z Monday). An unusually strong surface low of 989 mb was located over far north Georgia. Image credit: tropicaltidbits.com.

This past weekend’s activity was fed by a powerful disturbance rolling through the polar jet stream atop very sultry air for midwinter at ground level. Jacksonville, FL, set a record high of 84°F on Saturday, and air with dew points well above 70°F streamed onshore through the weekend.

The severe weather occurred in three distinct rounds, as shown in the satellite loop embedded at bottom.

--A pre-dawn supercell tore across southeast Mississippi and southwest Alabama early Saturday. Five tornadoes were reported. The most extensive damage occurred in and near Hattiesburg, MS, around 4:00 am CST by a long-track tornado (31 miles), a half-mile wide at its peak, that was rated EF3 on the enhanced Fujita intensity scale. This tornado produced 4 deaths and 56 injuries, according to the National Weather Service office in Jackson, MS. Insured damages are likely to top $200 million in Hattiesburg alone, Insurance Commissioner Mike Chaney said. Just four years ago, on February 10, 2013, Hattiesburg was extensively damaged by an EF4 twister that caused more than 80 injuries in two counties.


Figure 3. The William Carey University's School of Business on Saturday, Jan. 21, 2007, after it was damaged by a pre-dawn tornado that moved through Hattiesburg, MS. Image credit: AP Photo/Rogelio V. Solis.

--A more extended, widespread round of 31 tornadoes occurred from midday Saturday into Sunday morning. The main culprits were two long-lived supercell storms, the first of which rolled from extreme eastern AL across central GA to extreme western SC from about 10 am to 4 pm EST. The second supercell tore across southern GA after midnight. Eight people were killed when a tornado ripped through a mobile home park southeast of Adel, GA, around 3:45 am EST Sunday. Two others died in the same storm a few minutes later.

--Conditions became increasingly volatile by midday Sunday, leading the NOAA Storm Prediction Center to issue a rare “high risk” outlook (its first anywhere since 2014) for parts of southeast Georgia and northern Florida. Instability was more than adequate for severe weather, and wind shear was at extreme levels, with very high storm helicity (the amount of rotation imparted to a storm by winds at various levels). By early afternoon, thunderstorms were sweeping from the Gulf of Mexico into the Florida Panhandle with well-developed rotation evident on radar, a rare occurrence along this coast. The worst storm of the day produced a tornado that ravaged a mobile home park in Albany, GA, killing at least 4 people.

The afternoon’s other thunderstorms developed so quickly and vigorously that they competed with each other, reducing the odds that another long-lived tornadic supercell would emerge. Four other tornadoes were reported on Sunday afternoon and evening, but none of them produced widespread destruction.


Figure 4. WU radar depiction from 6:35 pm EST Sunday, Jan. 22, 2017, shows a broken line of intense thunderstorms extending from coastal SC and GA well into the eastern Gulf of Mexico.

A noteworthy January for tornadoes
All told, NOAA/SPC logged more than 40 tornado reports from early Saturday through early Monday, scattered from western Louisiana to far southeast Georgia. Loosely speaking, this whole event might be considered a single outbreak, since it emerged from the same overall weather pattern. However, experts often define an outbreak as a string of tornadoes with no more than six hours of tornado-free conditions. By that standard, we could label the early-Sunday tornadoes (round #2 above) as an “outbreak”, and all three periods above as a “sequence.”

Only a few Januarys since 1950 have produced outbreaks or sequences topping this one, according to a compilation from ustornadoes.com. The reigning champion is the outbreak of January 21-23, 1999, which led to nine deaths and produced 129 tornadoes from east Texas to southern Illinois. There was one F4 tornado in that event in far northeast Arkansas, and 11 other tornadoes were given F3 ratings on the original Fujita tornado intensity scale that was in use at the time.

The nation’s deadliest individual tornadoes on record in January, as noted by weather.com, were two Arkansas twisters that each led to 55 fatalities: one in Fort Smith on January 11, 1898, and the other in Warren on January 3, 1949.

Echoes of another El-Niño-to-La-Niña winter
Through early Monday, SPC had logged a total of 91 preliminary tornado reports for the month so far. The upcoming pattern will be much less conducive to severe weather throughout the week, and perhaps all the way to the end of the month. Even so, if all or most of these reports are confirmed, this could end up as the second most active January for tornadoes since comprehensive records began in 1950, according to ustornadoes.com. The clear record-holder is January 1999, when a total of 212 tornadoes were notched.

Interestingly, the twister-packed January of 1999 occurred during a moderately strong La Niña event that was in place one year after the record-setting 1997-98 El Niño event. Similarly, we’re now one year past the comparably strong 2015-16 El Niño event, and again experiencing La Niña, albeit a weak one. The only other “super El Niño” on par with these was in 1982-83; the following January of 1984 was very quiet tornado-wise, with only one confirmed twister. That year as a whole was quite active, though, with a devastating tornado outbreak in the Carolinas on March 28, 1984, killing 57 people and injuring more than 1000. In general, La Niña years appear to be a bit more favorable than El Niño years for early-spring tornado outbreaks, but this applies mainly to La Niña events that are at least moderately strong, which the current one isn’t. Recent work led by John Allen (now at Central Michigan University) has bolstered the idea that La Niña is more favorable than El Niño for springtime hailstorms and tornadoes.

Bob Henson


Tornado

Updated: 5:09 PM GMT on March 06, 2017

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More than 20 Deaths Feared in Italian Hotel Buried by Avalanche

By: Bob Henson , 4:14 PM GMT on January 20, 2017

An unusually frigid and snowy winter across southern Europe delivered its most dramatic blow yet on Wednesday evening, when a four-star resort in the Abruzzo province of central Italy, Hotel Rigopiano, was buried in an avalanche. About 30 people were believed to be in the hotel when the avalanche struck, with two others having survived because they were outside the building. Inside, rescuers carefully combed through the ruined structure. Imagery from inside the hotel showed massive amounts of snow piled in hallways and pushed against windows (see Figure 2). On Friday morning, six of the missing people were found alive in an air pocket in the building, and several others may have survived, according to rescuers.

Central Italy has been rocked by multiple earthquakes over the last few months, the deadliest being a temblor on August 24 centered about 30 miles (45 kilometers) north of L’Aquila that killed nearly 300 people. Four quakes of magnitudes 5.3 to 5.6 struck over a four-hour period on Wednesday about 15 mi (25 km) northwest of L’Aquila. It appears these quakes likely triggered the avalanche at the hotel, which is located near the town of Farindola on the east side of the rugged central Apennines mountain range.

Very heavy amounts of snow fell on the east slopes of the central Apennines in the days leading up to Wednesday’s quake. At Valle Castellana, about 30 mi (45 km) northwest of Farindola, roughly three meters (118 inches) of snow fell in a 48-hour period early this week at a surprisingly low elevation of around 2000 feet (700 meters), according to international weather records researcher Maximiliano Herrera.


Figure 1. Italian firefighters search for survivors after an avalanche buried a hotel near Farindola in central Italy, on Thursday, Jan. 19, 2017. Rescue workers on skis reported no signs of life as they searched for around 30 people believed trapped inside. Image credit: Italian Firefighters/ANSA via Italian Firefighters.


Figure 2. This image, made available by the Italian Guardia di Finanza (finance police) shows the avalanche inside the Rigopiano Hotel, near Farindola, Italy, Thursday, Jan. 19, 2017. Rescue workers reported no signs of life Thursday at a four-star hotel buried by an avalanche in the mountains of earthquake-stricken central Italy. Image credit: Guardia di Finanza/ANSA via Finance Police.

Italy’s worst avalanche in a century
The Farindola avalanche may end up being among the worst on record in the Apennines, and Europe’s deadliest since an avalanche took 30 lives in the Austrian Alps village of Galtür on February 23, 1999. By far the worst avalanche disaster in modern European history was the White Friday sequence of avalanches that struck the Italian Alps in December 1916 during World War I. Many thousands of soldiers were stationed across the region, and very heavy early-season snows made the soldiers vulnerable to avalanches, some of which may have been triggered (intentionally or not) by shells fired into the snow. On a single day, December 13 (White Friday), some 270 soldiers were lost as an Austrian set of barracks was buried. More avalanches followed in the subsequent week, killing as many as 10,000 soldiers.

This winter’s snowy grip on southern Europe
Record cold and widespread snow have plagued large parts of Europe over the last several weeks. At least 60 cold-related deaths were reported in Poland and other European nations during the first 10 days of January, according to weather.com. On January 7, Moscow dipped to –30°C (–22°F), making it the city’s coldest Orthodox Christmas in official records going back 120 years. Before then, the city endured an unofficial –35°C (–31°F) on Orthodox Christmas 1881. Also on January 7, the Naples (Italy) International Airport dipped to –5.6°C (21.9°F), tying its all-time low set in January 1981. (Records at this site go back to 1949.) All-time lows were also set in Albania at Vlore, with –9.4°C (15.1°F) and Durres, with –9.0°C (15.8°F).


Figure 3. A migrant sits on a chair outside a tent at the snow-covered refugee camp of Vagiohori village, about 45 kilometers (28 miles) east of the Greek city of Thessaloniki, on Thursday, Jan. 12, 2017. The European Commission said conditions for refugees on islands and other camps where they are housed in tents despite severe cold weather, is "untenable.” Image credit: AP Photo/Giannis Papanikos.

The cold blast has been especially vivid in southeastern Europe, thanks in part to snowfall across places that rarely see it. The town of Taormina, on Sicily’s east coast, received more than 10 cm (4 in) of snow on January 7, its heaviest accumulation since 1956, according to Herrera. Last week, he added, several parts of the Peloponnese region of Greece reported their first snow cover in living memory, including the port of Lefkada. Historic sea-level snow also fell on the Greek coastal town of Kiato and on the islands of Othonio, Kefalonia, Meganisi, and Zante, according to Herrera. One of the first snowfalls in decades whitened the beaches of southeastern Spain on Wednesday night in the province of Alicante, though no snow was reported in the cities of Valencia and Alicante. The coastal town of Torrevieja last saw accumulating snow in December 1926.

Ice from the sky, Moroccan style
The cold air aloft made it all the way to northern Africa, where it fed the development of thunderstorms despite chilly surface air. The beach at Raf Raf, Tunisia, was partially covered by snow, the first sea-level accumulation in the country since 1981. A thunderstorm hit Tunis, Tunisia, on Tuesday while the surface temperature was just 3°C (37°F). Another thunderstorm left Morocco’s capital city of Rabat covered in a rare coating of graupel on Thursday afternoon, as shown in this clip from Morocco World News and in the embedded video at bottom. Graupel is produced when supercooled water droplets are captured by falling snowflakes, leading to dense showers of small, soft frozen pellets distinct from either hailstones or snowflakes. Temperatures at the Rabat airport dropped to 48°F (9°C) during the graupel shower.

Another stormy weekend for both U.S. coasts
The highly progressive parade of upper-level storms that’s been racing across the United States in recent days will continue this weekend. Several quick-hitting rounds of heavy rain and mountain snow are expected in California, including what could be the biggest deluge and highest surf to hit southern California in years. As much as 6” of rain could fall in coastal locations, including Los Angeles, and up to 9” in foothill and mountain areas, according to the NWS/Los Angeles office. Waves of up to 30 feet could crash into the central California coast from Friday into Saturday, with 15-foot waves possible along LA-area beaches. Waterspouts and hail are possible on Friday as short lines of thunderstorms, and perhaps low-topped supercell storms, swing across the southern California coast.

Farther downstream, a very intense surface low will spin up over the Southern Plains and push into the Southeast by early next week. NOAA’s Storm Prediction Center is highlighting an enhanced risk of severe weather on Saturday over parts of the lower Mississippi Valley (with some potential for tornadoes) and on Sunday across northeast Florida and southeast Georgia. The surface low’s central pressure is expected to dip below 990 millibars, possibly challenging some local records for the all-time lowest pressures observed in January, as noted by Eric Webb (@webberweather). You can compare the observations as they come in with this handy NWS guide to month-by-month surface pressure records.

Thanks go to Maximiliano Herrera for several of the European and African statistics cited here. We’ll be back with a new post on Monday. Have a great weekend, everyone!

Bob Henson


Video 1. A rare graupel thundershower pelts the capital city of Morocco, Rabat, on Thursday, January 19, 2017. Video credit: HESPRESS.


Winter Weather Severe Weather

Updated: 5:08 PM GMT on March 06, 2017

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Confirmed: 2016 the Warmest Year in History of Global Recordkeeping

By: Jeff Masters and Bob Henson , 4:28 PM GMT on January 18, 2017

For the third year in a row, Earth has experienced the warmest surface temperatures in global data extending back to 1880. In its annual climate summary released on Wednesday, NOAA’s National Centers for Environmental Information (NCEI) calculated that the average global temperature across both land and ocean surfaces for 2016 was 1.69°F (0.94°C) above the 20th-century average of 13.9°C (57.0°F). This made 2016 the warmest calendar year on record, coming in 0.07°F (0.04°C) ahead of the record set just last year. Using a slightly different technique, NASA also confirmed that 2016 was the warmest year in this 136-year period.

Last year was also the warmest on record for satellite-based estimates of temperature through the lowest five miles of the atmosphere, as calculated by the University of Alabama in Huntsville (UAH). In the UAH dataset, 2016 came in just 0.02°C (0.04°F) ahead of 1998. Because these calculations are indirect, large-scale estimates of temperature well above ground level, derived from satellite data, they need not correspond to trends in direct ground-based measurements of surface temperature.

The second year of a major El Niño tends to warm the global atmosphere even more than the first, as the atmosphere gradually adjusts to the ocean-surface warming. This gave 2016 a very good shot at breaking the global temperature record that was just set by 2015, which in turn beat out 2014. The absence of a strong El Niño heading into 2017 tells us that the coming year, while expected to be very warm by 20th-century standards, is unlikely to continue the remarkable three-year string of consecutive global heat records set by 2014, 2015, and 2016.

It’s worth noting that only about 0.2°C of last year’s departure from long-term average temperature can be explained by El Niño, especially given that the tropical Pacific transitioned to a weak La Nina by late 2016. The fact that 2016 was still the warmest year on record can mostly be attributed to the steady build-up of heat-trapping greenhouse gases due to human activities.


Figure 1. Departure from the 20th-century average for the global January-through-December temperature for the years 1880 - 2016. Last year saw the warmest temperatures on record, following previous global record highs in 2014 and 2015. Image credit: NOAA/National Centers for Environmental Information (NCEI).

Third warmest December on record
December 2016 was Earth's third warmest December since record keeping began in 1880, reported NOAA/NCEI on Wednesday. December 2016 was 0.79°C (1.42°F) warmer than the 20th-century December average, but 0.33°C (0.60°F) cooler than the record warmth of 2015. NASA reported that December 2016 was the second warmest December in its database, behind December 2015 and just ahead of December 2014. The difference between the two data sets is, in large part, due to how they handle the data-sparse areas in the Arctic, which was record warm in December. NOAA does not include most of the Arctic in their global analysis, while NASA does.


Figure 2. Departure of temperature from average by region for December 2016, the third warmest December for the globe since record keeping began in 1880. Record warmth was observed across parts of southern Mexico and Central America, western Norway, parts of sub-Saharan Africa, and parts of the Middle East and southern Asia along a belt from Iran to eastern China. Cooler-than-average conditions were observed across the northwest United States, southeast Europe, and western Russia. Image credit: NOAA National Centers for Environmental Information (NCEI).

As noted above, a weak La Niña event is now under way in the eastern tropical Pacific, and the cool waters present there have helped cool the planet slightly below the record warm levels observed during the strong El Niño event that ended in May 2016. The fact that December 2016 was still among the three warmest Decembers on record despite the presence of La Niña can mostly be attributed to the steady build-up of heat-trapping greenhouse gases due to human activities.

Ocean-only, land-only, and lower atmosphere temperatures in December
Ocean-only temperatures this December were the fourth warmest on record, while land-only temperatures were the sixth warmest on record. (Since most of Earth’s surface is covered by ocean, the land-plus-ocean reading is dominated by the ocean-only temperatures.) For the lowest 8 km of the atmosphere, global satellite-measured temperatures in December 2016 were the third warmest in the 38-year record, behind December 2016 and 1997, according to the University of Alabama in Huntsville.

Arctic sea ice hits its second lowest December extent on record
December 2016 Arctic sea ice extent was the second lowest in the 38-year satellite record, according to the National Snow and Ice Data Center (NSIDC). Arctic sea ice set new records for low extent in 2016 for the months of January, February, April, May, June, October,and November. Ice extent has also been very low in the Antarctic, where record lows were set in both November and December. As we discussed in a November post, sea ice extents in the Arctic and Antarctic vary through mostly independent processes, so the simultaneous record lows in recent months are somewhat unexpected.


Figure 3. Daily mean temperatures by Julian day for 2016 over the Arctic north of 80°N, as compiled by the Danish Meteorological Institute (DMI). Temperatures for 2016 (red line) are compared to the long-term averages (green line.) Temperatures in October, November, and December were 5 -  20°C (9 - 36°F) above average. This is by far the warmest multi-month anomaly measured since DMI began tracking Arctic temperatures in 1956. According to the 2016 Arctic Report Card, issued last week, the average surface air temperature of the Arctic for the year ending September 2016 was by far the highest since 1900. Temperatures in the Arctic are continuing to warm at roughly twice the pace of the global average, which is an expected outcome of climate change caused by human-produced greenhouse gases.

No billion-dollar weather disasters in December 2016
According to the December 2016 Catastrophe Report from insurance broker Aon Benfield, no billion-dollar weather-related disasters hit the planet in December. During 2016, there were 31 billion-dollar weather disasters globally. This is the fourth greatest number of such disasters in any year since 1990. See our post from January 17 for a full summary.

Notable global heat and cold marks set in December 2016
Hottest temperature in the Northern Hemisphere: 42.8°C (109.0°F) at Diourbel, Senegal, 2 December
Coldest temperature in the Northern Hemisphere: -56.9°C (-70.4°F) at Suhana, Russia, 31 December
Hottest temperature in the Southern Hemisphere: 46.3°C (115.3°F) at Birdsville Airport, Australia, 2 December
Coldest temperature in the Southern Hemisphere: -44.0°C (-77.1°F) at Dome A, Antarctica, 2 December
(Courtesy of Maximiliano Herrera.)

Major weather stations that set (not tied) new all-time heat or cold records in December 2016 (Courtesy of Maximiliano Herrera)
Santiago (Chile) max. 37.3°C, 14 December
Santiago Airport (Chile) max. 37.0°C, 14 December
Rapel (Chile) max. 36.4°C, 14 December
Oruro (Bolivia) max. 27.6°C, 18 December
Big Bend (Swaziland) max. 46.1°C, 22 December
Vuvulane (Swaziland) max. 44.3°C, 22 December
Ambon (Indonesia) max. 36.4°C, 22 December
Mouyondzi (Congo Brazzaville) max. 36.4°C, 22 December
Luanda (Angola) max. 36.9°C, 22 December

More nations set all-time highs in 2016 than in any other year
From January through December 31, 2016, a total of 22 nations or territories tied or set all-time records for their hottest temperature in recorded history.  This breaks the record of eighteen all-time heat records in 2010 for the greatest number of such records set in one year. Just one nation or territory—Hong Kong—set an all-time cold temperature record in 2016. "All-time" record here refers to the warmest or coldest temperature ever reliably reported in a nation or territory. The period of record varies from country to country and station to station, but it is typically a few decades to a century or more. Most nations do not maintain official databases of extreme temperature records, so the national temperature records reported here are in many cases not official. Our data source is international weather records researcher Maximiliano Herrera, one of the world's top climatologists, who maintains a comprehensive list of extreme temperature records for every nation in the world on his website. If you reproduce this list of extremes, please cite Maximiliano Herrera as the primary source of the weather records. Here are 2016's all-time heat and cold records:

The Comoros: December 22, 2016, 35.6°C (96.1°F) at Hahaya Airport (tie).
French Guiana : September 27, 2016, 38.0°C (100.3°F) at Saint Laurent du Moroni.
The Marshall Islands: August 24, 2016, 35.6°C (96.1°F) at Utirik Atoll.
The Cayman Islands (United Kingdom territory) : August 21, 2016, 34.9°C (94.8°F) at Owen International Airport (tie).
The British Virgin Islands [United Kingdom territory]: July 22, 2016, 35.0°C (95.0°F] at Terrance B. Lettsome International Airport.
Iraq: July 22, 2016, 53.9°C (129.0°F) at Basrah.
Iran: July 22, 2016, 53.0°C (127.4°F) at Delhoran (tie).
Kuwait : July 21, 2016, when the mercury hit 54.0°C (129.2°F) at Mitribah.
Guernsey (United Kingdom territory): July 19, 2016, 35.0°C (95°F) at the small island of Alderney (tie).
Hong Kong Territory (China): July 9, 2016, 37.9°C (100.2°F) at Happy Valley (tie).
Niger: June 8, 2016, 49.0°C (120.2°F) at Bilma.
Palau: June 8, 2016, 34.4°C (93.9°F) at Koror AWS (tie).
India : May 19, 2016, 51.0°C (123.8°F) at Phalodi.
Maldives: April 30, 2016, 35.0°C (95.0°F) at Hanimaadhoo.
Thailand: April 28, 2016, 44.6°C (112.3°F) at Mae Hong Son.
Cambodia: April 15, 2016, 42.6°C (108.7°F) at Preah Vihea.
Burkina Faso: April 13, 2016, 47.5°C (117.5°F) at Dori.
Laos: April 12, 2016, 42.3°C (108.1°F) at Seno.
Vanuatu in the South Pacific: February 8, 2016, 36.2°C (97.2°F) at Lamap Malekula.
Tonga: February 1, 2016, 35.5°C (95.9°F) at Niuafoou.
Wallis and Futuna Territory (France): January 10, 35.8°C (96.4°F) at Futuna Airport.
Botswana: January 7, 2016, 43.8°C (110.8°F) at Maun.

Hong Kong Territory (China) set its all-time coldest mark on January 24, 2016, -6.0°C (21.2°F) at Tai Mo Shan (elevation 950 meters.) Tai Mo Shan has a period of record going back to 1996; the coldest temperature near sea level since record keeping began at the Hong Kong Observatory in 1884 was 0°C (32°F) on January 18, 1893.

Monthly national and territorial records of highest temperature beaten or tied (excluding records valid for any month):  145
Monthly national and territorial records of lowest temperature beaten or tied  (excluding records valid for any month):  4

Station records (not including tied records)
Number of stations that beat their all-time highest temperature: 316
Number of stations that beat their all-time lowest temperature: 21

Worldwide extreme temperatures for 2016
Highest in Northern Hemisphere:  54.0°C (129.2°F) at Mitribah, Kuwait, on July 21
Lowest in Northern Hemisphere:  –61.3°C (–78.3°F) at Geo Summit, Greenland, on February 11

Highest in Southern Hemisphere:  48.6°C (119.5°F) at Augrabies Falls, South Africa, on January 5
Lowest in Southern Hemisphere:  –82.4°C (–116.3°F) at Concordia, Antarctica, on July 8

Global, hemispheric and continental records for 2016
Highest temperature ever recorded in February in Northern Hemisphere:  45.0°C at Nguigmi (Niger) on February 26 (tie)
Highest reliable minimum temperature ever recorded in Africa:  37.5°C at Yelimane (Mali) on May 1
Highest minimum temperature ever recorded in May in Australia+Oceania:  29.6°C at Troughton Island (Australia) on May 2
Highest temperature ever recorded in May in South America:  41.4°C at Valledupar, Colombia, on May 23
Highest temperature ever recorded in May in Antarctica: 17.2°C at Esperanza on May 26
Highest minimum temperature ever recorded in Antarctica: 8.8°C at Esperanza on May 27
Highest temperature ever recorded in June in Southern Hemisphere:  39.5°C at Picos, Brazil, on June 4
Highest minimum temperature ever recorded in June in Australia+Oceania:  28.8°C at Troughton Island, Australia, on June 6
Highest temperature ever recorded in June in Australian+Oceania:  37.9°C at Bradshaw, Australia, on June 7
Highest temperature ever recorded in Asia:  54.0°C at Mitribah, Kuwait, on July 21
Highest temperature ever recorded in July in Australia+Oceania:  38.3°C at Kalumburu, Australia, on July 24
Lowest temperature ever recorded in Northern Hemisphere in July:  –30.5°C at Geo Summit, Greenland, on July 31
Highest minimum temperature ever recorded in the world in August:  40.8°C at Delhoran, Iran, on August 2
Highest temperature ever recorded in September in Asia:  51.2°C at Mitribah, Kuwait, on September 4
Highest temperature ever recorded in September in Europe:  45.7°C at Montoro, Spain, on September 6
Highest minimum temperature ever recorded in September in Australia+Oceania:  30.0°C at Warmun, Australia, on September 28
Lowest temperature ever recorded in October in Africa:  –10.5°C at Buffelsfontein, South Africa, on October 5
Highest temperature ever recorded in December in the Northern Hemisphere:  42.8°C in Diourbel, Senegal, on December 2

The reading of 54°C at Mitribah, Kuwait, on July 21 ties the highest global temperature that has been measured reliably by contemporary standards. See the October blog post from WU weather historian Christopher Burt for a discussion of the WMO world heat record of 134°F (56.7°C), recorded in Death Valley, California, on July 10, 1913. For a variety of reasons, Burt concluded, “the best explanation for the record high report(s) in July 1913 is observer error.”

We'll be back with a new post on Friday.

Jeff Masters and Bob Henson

Climate Summaries

Updated: 4:52 PM GMT on March 06, 2017

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A Swarm of 31 Billion-Dollar Weather Disasters Socked the Planet in 2016

By: Jeff Masters and Bob Henson , 5:41 PM GMT on January 17, 2017

Earth had a tough year for billion-dollar weather-related natural disasters in 2016, with 31. This is the fourth-largest number on record going back to 1990, said insurance broker Aon Benfield in their Annual Global Climate and Catastrophe Report issued January 17 (updated January 23 to include a 31st billion-dollar disaster, the Gatlinburg, Tennessee fire.) The average from 1990 - 2016 was 22 billion-dollar weather disasters; the highest number since 1990 was 41, in 2013. The combined economic losses from all 315 weather and earthquake disasters catalogued by Aon Benfield in 2016 was $210 billion, which is 21% above the 16-year average of $174 billion. The U.S. had the most billion-dollar weather disasters of any country, with fifteen included on the Aon Benfield list (plus one more catalogued by NOAA--see below). China came in second, with seven. Flooding was the most expensive peril globally for the fourth year in a row.

The report noted: “…it can be concluded that there has been an increase in both annual and individual weather disaster costs in the last nearly four decades. It can reasonably be assumed that the combination of effects from climate change, more intense weather events, greater coastal exposures and population migration patterns are all equal contributors to the loss trend.”

Natural disasters (including earthquakes) killed approximately 8250 people in 2016, a small fraction of the 2001 - 2015 average of around 71,000 fatalities per year and also far below the median number per year (around 22,500). The deadliest weather disaster of 2016 was Hurricane Matthew (605 killed in the U.S. and Caribbean, with unofficial estimates in Haiti as high as 1600), while the costliest weather-related disaster was the $28 billion Yangtze River floods in China.

Munich Re, the world's largest reinsurance firm, put global losses from natural disasters at $175 billion in 2016, compared to $71 billion in 2015. The high losses in 2016 were driven by increasingly powerful storms and an “exceptionally" high number of severe floods, with flooding causing more than a third of all losses, well above the 10-year average of 21%.


Figure 1. The yearly number of billion-dollar global weather disasters, adjusted for inflation, as compiled by insurance broker Aon Benfield in their Annual Global Climate and Catastrophe Reports. The increasing trend in weather disaster losses is at least partially due to increases in wealth and population, and to people moving to more vulnerable areas--though the studies attempting to correct damage losses for these factors are highly uncertain. Climate change may also be partly to blame for the rise in disaster losses. We discussed this topic in more detail in a 2012 post, Damage Losses and Climate Change.

Four nations see their costliest weather disasters in history
By comparing the Aon Benfield numbers to historical disaster costs at EM-DAT, the International Disaster Database, we see that at least four nations set records for their all-time most expensive weather-related disaster in 2016. For comparison, nine nations had their most expensive weather-related natural disasters in history in 2015. Here are the nations that set records in 2016 for their most expensive weather-related disaster in history:

Fiji suffered $1.4 billion in damage from Tropical Cyclone Winston in February 2016 (32% of GDP.) This beats the $167 million cost of Tropical Cyclone Kina of January 1993 (2016 dollars) for most expensive disaster in Fiji’s history. (Note: EM-DAT puts Winston’s damage in Fiji at $470 million.)

Zimbabwe suffered $1.6 billion in damage from its drought in 2016 (11% of GDP.) Their previous most expensive weather-related disaster was the $262 million cost (2016 dollars) of a February 25, 2003 flood.

Haiti suffered $1.9 billion in damage from Hurricane Matthew (21% of GDP.) Haiti’s previous most expensive hurricane: $1.17 billion (2016 dollars) from Hurricane Allen in 1980.

Sri Lanka suffered $1.8 billion in damage from Tropical Cyclone Roanu in May 2016 (2.2% of GDP.) Their previous most expensive disaster was the $321 million cost (2016 dollars) of the February 1, 2011 flood. (Note: EM-DAT puts Roanu’s damage in Sri Lanka at $2 billion.)


Aon Benfield’s tally of billion-dollar weather disasters globally for 2016
1) Flooding, Yangtze Basin, China, 5/1 - 8/1, $28.0 billion, 475 killed
2) Hurricane Matthew, Caribbean, Bahamas, U.S., 9/28 - 10/10, $15.5 billion, 603+ killed
3) Flooding, Louisiana U.S., 8/9 - 8/16, $10 - $15 Billion, 13 killed
4) Drought, China, 6/1 - 8/31, $6 billion, 0 killed
5) Flooding, Germany, France, Austria, Poland, 5/26 - 6/6, $5.5 billion, 17 killed
6) Drought, India, 1/1 - 6/30, $5.0 billion, 0 killed
7) Flooding, Northeast China 7/16 - 7/24, $4.7 billion, 289 killed
8) Wildfire, Fort McMurray, Canada, 5/2- 6/1, $4.5 billion, 0 killed
9) Severe Weather, Plains-Southeast U.S., 4/10 - 4/13, $4.3 billion, 1 killed
10) Drought, West-Northeast-Southeast U.S., 1/1 - 12/31, $3.5 billion, 0 killed
11) Drought, Thailand, 1/1 - 6/30, $3.3 billion, 0 killed
12) Severe Weather, Rockies-Plains-Southeast-Midwest U.S., 3/22 - 3/25, $2.5 billion, 0 killed
13) Super Typhoon Meranti, China, Taiwan, Philippines, 9/13 - 9/16, $2.5 billion, 44 killed
14) Flooding, Texas U.S., 4/15 - 4/19, $2.0 billion, 9 killed
15) Winter Weather, East Asia, 1/20 - 1/26, $2.0 billion, 116 killed
16) Severe Weather, Plains-Midwest U.S., 4/29 - 5/3, $1.8 billion, 6 killed
17) Tropical Cyclone Roanu, Sri Lanka, India, Bangladesh, Myanmar, China, 5/14 - 5/21, $1.8 billion, 135 killed
18) Severe Weather, Plains-Rockies U.S., 7/28 - 7/29, $1.6 billion, 0 killed
19) Drought, Zimbabwe, 6/1 - 8/10, $1.6 billion, 0 killed
20) Flooding and Severe Weather, Plains-Midwest-Southeast-Northeast U.S., 3/4 - 3/12, $1.5 billion, 6 killed
21) Super Typhoon Nepartak, Philippines, Taiwan, China, 7/8 - 7/12, $1.4 billion, 111 killed
22) Severe Weather, Plains-Southeast U.S., 3/17 - 3/18, $1.4 billion, 0 killed
23) Tropical Cyclone Winston, Fiji, 2/16 - 2/22, $1.4 billion, 44 killed
24) Flooding, Argentina and Uruguay, 4/4 - 4/10, $1.3 billion, 0 killed
25) Severe Weather, Plains-Midwest U.S., 5/21 - 5/28, $1.3 billion, 1 killed
26) Severe Weather, Plains-Midwest-Southeast-Northeast U.S., 2/22 - 2/25, $1.2 billion, 10 killed
27) Severe Weather, Netherlands, 6/23 - 6/24, $1.1 billion, 0 killed
28) Severe Weather, Plains-Midwest-Mississippi Valley U.S., 5/7 - 5/10, $1.1 billion, 2 killed
29) Winter Weather, Eastern U.S., 1/21 - 1/24, $1.0 billion, 58 killed
30) Super Typhoon Chaba, South Korea, Japan, 10/5 - 10/6, $1.0 billion, 10 killed
31) Wildfire, Tennessee U.S., 11/28, $1.0 billion, 14 killed


Figure 2. The yearly number of billion-dollar U.S. weather disasters, adjusted for inflation, as compiled by NOAA/NCEI.

U.S. sees 15 billion-dollar weather disasters
In the U.S., there were fifteen billion-dollar weather disasters in 2016, according to NOAA's National Centers for Environmental Information (NCEI). Aon Benfield did not include the aggregated U.S. wildfire toll as a billion-dollar disaster in its list, whereas NOAA categorized it as a $2.0 billion disaster, with 21 deaths. (There are two other differences in the lists: Aon Benfeld rated the winter weather outbreak on January 21 as costing a billion dollars, while NOAA had lower damages, and NOAA rated a flood disaster centered in West Virginia on June 22 - 24 as costing $1.0 billion, while Aon Benfield had lower damages.) NOAA's fifteen billion-dollar weather disasters of 2016 marked the 2nd highest yearly total for the U.S. since 1980. The ten-year average is eight. Billion-dollar events account for roughly 80% of the total U.S. losses for all weather-related disasters. An unprecedented four billion-dollar flood disasters (non-hurricane related) hit the U.S. in 2016.

The 31 billion-dollar weather disasters of 2016

Multi-Month Drought Disaster 1. El Niño-related drought conditions began in India in 2015 and intensified during 2016, causing at least $5 billion in losses, making it by far the nation’s most expensive drought in history. The drought was worsened by a May heat wave that brought the hottest temperature ever recorded in India--51.0°C (123.8°F) at Phalodi on May 19, 2016. Temperatures hit a record 46°C (114.8°F) at Indira Gandhi International Airport that day. as well. In this photo, we see Indian vendors sell bottles of drinking water to passengers at a bus stop on a hot day in Allahabad on May 21, 2016. Image credit: Sanjay Kanojia, Getty Images.


Multi-Month Drought Disaster 2. The El Niño event of 2015 - 2016 brought deficient rains and devastating drought to Thailand during the first half of 2016, causing $3.3 billion in agricultural losses. This picture taken on March 23, 2016 shows a farmer walking on his drought-hit rice field in Nonthaburi province outside Bangkok. Thailand has long served as one of the globe's biggest rice bowls, but a growing water shortage is now pushing the country to move away from the grain that dominates its fields and has defined a way of life for generations. Image credit: AFP/ Christophe Archambault.


Multi-Month Drought Disaster 3. Drought in Zimbabwe cost the nation $1.6 billion in 2016--by far their most expensive natural disaster in history. In this image, we see a cow grazing in the distance in the dry area of the decommissioned Upper Ncema Dam, which sank below 2 percent of its capacity on November 24, 2016 at Esigodini, South of Matabeleland. Image credit: Zinyange Auntony/AFP/Getty Images.


Multi-Month Drought Disaster 4. Severe drought began in June and intensified during August across northeastern China in the Inner Mongolia, Jilin and Heilongjiang provinces. The Ministry of Civil Affairs (MCA) reported well-above-normal temperatures and reduced rainfall that damaged more than 3.1 million hectares (7.6 million acres), with total economic losses at $6 billion. In this image, we see drought conditions in China as of September 1, 2016. Image credit: Beijing Climate Center.


Multi-Month Drought Disaster 5. Drought struck two widely separated parts of the United States in 2016. California continued to feel the impacts of a severe multiyear drought that began in 2012, including major crop losses and the death of more than 100 million trees. During the summer and autumn, drought intensified across parts of the Northeast and New England as well as the South. The southern and central Appalachians were especially hard hit, as rainfall dropped to record-low levels during autumn. Dozens of wildfires erupted in the tinder-dry forest, including a blaze that ravaged large parts of the Gatlinburg, Tennessee, area on November 28-29, 2016. Pictured above are dead and dying ponderosa and sugar pine in California’s Sequioa National Forest. Image credit: USDA Forest Service, via phys.org.

January

Disaster 1. A massive blizzard rocked the Mid-Atlantic and Northeast U.S. January 21 - 24, killing 58 and causing at least $1 billion in damage. The snowstorm was rated the 4th most severe to hit the area in the past 66 years, according to NOAA. In this image, we see residents being forced to walk in the streets of Washington, D.C. during the storm. Image credit: Joe Flood, NOAA.


Disaster 2. One of the most intense cold air outbreaks in decades brought record low temperatures and heavy snowfall throughout much of East Asia January 20 - 25, killing a combined 116 people in Taiwan, Thailand, China, Japan and South Korea. China reported more than $1.6 billion in damage from cold and snow, and Taiwan’s agricultural sector recorded its highest losses in 17 years. Total damage from the winter weather was estimated at $2 billion. In this image, we see row boats stuck in the ice of the frozen coastal waters of Jiaozhou Bay in Qingdao in eastern China's Shandong province on January 25, 2016. Image credit: STR/AFP/Getty Images.

February

Disaster 1. A powerful spring-like winter storm brought severe thunderstorms and heavy snowfall across much of the Central and Eastern U.S. from February 22 - 25, killing 10 and injuring dozens more. The National Weather Service confirmed 59 tornadoes, including four rated EF3. Total damage was estimated at $1.2 billion. In this image, we see damage in Waverly, Virginia, a day after a tornado barreled through the small community on February 25, 2016. Tornadoes killed four people in Virginia on February 24. Image credit: Jay Paul/Getty Images.

March
Disaster 1. A record-strength upper-level low pressure system that stalled out over Northern Mexico and Southern Texas brought widespread severe weather and at least $1.25 billion in damage to the U.S. from March 4 to 12. In this photo, we see flood damage in Haughton, Louisiana, on March 9, 2016, after rainfall in excess of 20" in a four-day period hit the Shreveport area, bringing historic flooding. Image credit: Michael Dean Newman.


Disaster 2.  A stationary front draped over Texas and the Gulf Coast on March 17 - 18 triggered widespread severe weather. Large hail and damaging winds hit Texas, Mississippi, Arkansas, Louisiana and Florida. The greatest damage occurred in Dallas-Fort Worth, where tennis ball-sized hail pummeled southern Tarrant County. Parts of southern Mississippi recorded baseball-sized hail. Total economic losses were expected to be $1 billion. In this photo, we see menacing mammatus clouds over Boerne Stage Field, Texas, on March 18, 2016. Image credit: wunderphotographer agrant414.


Disaster 3. A strong storm system tracked across central and eastern sections of the United States from March 22 - 25, injuring several people. The storm brought tornadoes, large hail, damaging straight-line winds and heavy snow to portions of the Rockies, Plains, Midwest, and Southeast. The costliest damage resulted from hail and thunderstorm winds in Texas, Oklahoma, Louisiana, Arkansas, Mississippi, Alabama and Florida. Heavy snow and near hurricane-force winds caused property damage and travel delays throughout the Rockies and the High Plains. In this photo, we see an impressive shelf cloud from a thunderstorm over Tampa, Florida, on March 25, 2016. Image credit: wunderphotographer chelina.

April

Disaster 1. Torrential rains led to severe flooding across portions of Argentina and Uruguay from April 4 - 10. No serious injuries or fatalities were reported. Hardest hit was northeast Argentina, where seven-day rainfall totals tallied as much as 750 millimeters (29.53 inches] in parts of the provincial regions of Entre Rios, Corrientes, Santa Fe, Chaco, Formosa, and Santiago del Estero. More than 15,000 people were affected, with most of the damage occurring along the overflowing Paraná and Salado rivers. Substantial damage occurred to 4 percent of the country’s soybean crop. Total economic losses to agriculture in Argentina alone were estimated at $1.3 billion. In this image, we see flooding in Villa Paranacito, Entre Rios, Argentina, on April 28, 2016. (AP Photo/Natacha Pisarenko)


Disaster 2. Severe thunderstorms caused catastrophic hail damage across parts of the Plains and Southeast from April 10 - 13, killing at least one person and injuring dozens more. The Dallas-Fort Worth and San Antonio metro regions in Texas were the hardest hit, where softball- and baseball-sized hail fell. Damage was estimated at $4.3 billion. In this photo, we see an impressive shelf cloud from a thunderstorm over Royce City, Texas, on April 11, 2016. Image credit: wunderphotographer Gweduc.


Disaster 3. Extreme rainfall of up to 17” created widespread urban flooding in Houston and surrounding suburbs April 15 - 19, killing eight people. Over 1,000 homes and businesses were damaged, and there were more than 1,800 high water rescues. It was the most widespread flood event to affect Houston since Tropical Storm Allison in 2001. The same storm also brought heavy snow and severe thunderstorms from April 15 - 19 to parts of the Rockies and Plains, killing one person. Damage was estimated at $2.0 billion. Above, we see a drone image of flooding in north Houston on April 20, 2016. Image credit: wunderphotographer Moussifer.


Disaster 4. A large outbreak of tornadoes affected numerous states across the South and Southeast April 29 - May 3, killing six people. Additional damage came from large hail and straight-line winds during the multi-day thunderstorm event, with total damage reaching $1.8 billion. In this image, we see a hailstorm hitting Mebane, NC on April 28, 2016. Image credit: wunderphotographer birdyboo.

May

Disaster 1. A devastating wildfire roared through Fort McMurray, Alberta in early May 2016, causing at least $4.5 billion in damage. In this photo, we see a group trying to rescue animals from Fort McMurray waiting at a roadblock as smoke rises from the fire on May 6, 2016. Image credit: Cole Burston/AFP/Getty Images.


Disaster 2. Tornadoes and severe storms caused widespread damage totaling $1.0 billion across the Plains and Central states (NE, MO, TX, OK, KS, CO, IL, KY, TN) May 7 - 10. The damage was greatest in Nebraska and Missouri. In this image, we see a rotating supercell thunderstorm with a wall cloud over Stillwater, OK, on May 9, 2016. Image credit: wunderphotographer gunhilda. 


Disaster 3.  Cyclone Roanu brought torrential rainfall and devastating floods and landslides to much of Sri Lanka and portions of India, Bangladesh, Myanmar, and China on May 14 - 21, 2016. At least 135 people were killed and damages were estimated at over $1.8 billion, making the most expensive weather-related disaster in Sri Lankan history. In this image, we see Sri Lankan military personnel take part in relief and rescue efforts following a landslide in the village of Bulathkohupitiya on May 18, 2016. (STR/AFP/Getty Images)


Disaster 4. A sustained period of severe thunderstorms and tornadoes affected several states including Montana, Colorado, Kansas, Missouri and Texas on May 21 - 28. The most concentrated days for tornado development were on May 22 and 24. Additional damage was created by straight-line high wind and hail damage, with total damage reaching $1.3 billion. In this image, we see a hailstone collected in Holyoke, CO on May 24, 2016. Image credit: wunderphotographer Imway.


Disaster 5. Extratropical storm "Elvira" spawned numerous severe thunderstorms and torrential rains across parts of northern Europe between May 26 and June 6, killing at least 17 people and causing $5.5 billion in damage. The heaviest damage was in Germany, France, Austria, Poland and Belgium. In this image, we see firemen rescuing two women on June 3, 2016 in Simbach am Inn, Germany. Image credit: Sebastian Widmann/Getty Images.

June

Disaster 1. Severe thunderstorms swept through the Netherlands, causing hail, wind and isolated flash flood damage in South Holland and Utrecht provinces on June 23 - 24, with damages estimated at $1.1 billion. In this image, we an arcus cloud from a severe thunderstorm over the A2 highway between Utrecht and Amsterdam on June 23, 2016. Image credit: ROBIN VAN LONKHUIJSEN/AFP/Getty Images.

July

Disaster 1. Super Typhoon Nepartak hit Taiwan on July 7 as a Category 4 storm with 150-mph winds, killing 3 and causing over $20 million in damage. After weakening to a tropical storm, Nepartak made landfall in mainland China, where it killed at least 83 people and caused $1.4 billion in damage. Here, we see a radar image of Super Typhoon Nepartak taken at 11:30 am EDT July 7, 2016 (11:30 pm local time in Taiwan), when Nepartak was a Category 5 storm with 160 mph winds. Image credit: Taiwan CWB.


Disaster 2. Torrential rains fell in northern sections of China from July 16 - 24, leaving at least 289 people dead or missing, and causing $4.7 billion in damage. The hardest-hit provinces included Beijing, Hebei, Henan, Shanxi, Tianjin, and Shandong. More than 300,000 homes were damaged or destroyed and as many as 1.2 million hectares (3.0 million acres) of cropland was submerged. This photo taken on July 21, 2016 shows people making their way through a flooded area in Changping District in Beijing. Image credit: STR/AFP/Getty Images.


Disaster 3. Severe thunderstorms across the Rockies and Northeastern states (CO, WY, VA, MD, PA, NJ, NY) on July 28 - 29 caused large hail and high wind damage. Storm damage in Colorado was the most costly, due to hail, and total damage was estimated at $1.6 billion. In this image, we see a supercell thunderstorm hitting Wichita, Kansas, on July 28, 2016. Image credit: wunderphotographer GameShow.


Disaster 4. Earth's official most expensive weather-related disaster of 2016--and the third most expensive non-U.S. weather-related disaster in world history--was the extreme summer flooding in China’s Yangtze River basin. Torrential rains began in mid-May and peaked in July, causing catastrophic flooding that killed 475 and did $28 billion in damage. In this photo, we see a stadium in Wuhan, China on July 6, 2016, after the city received 7.09” (180 mm) of rain in the twelve hours ending at 8 am July 6. Wuhan received over 560 mm (1.8 feet) of rain over the ten day period before the July 6 deluge, causing widespread damage and chaos. Image credit: Wang He/Getty Images.

August

Disaster 1. Torrential rains of 20 - 30” fell over portions of Louisiana August 9 - 16 from a tropical depression-like storm that moved slowly across the southern U.S. for a week. Catastrophic flooding killed thirteen people, and damaged as many as 110,000 homes and 100,000 vehicles. Damage was estimated at $10 - $15 billion, which will likely make it the second most expensive non-hurricane related flood in U.S. history, behind the $35 billion in damage from the summer 1993 flooding in the Midwest. In this image, we see an aerial view of flooding in Hammond, Louisiana on August 13, 2016. Image credit: AP Photo/Max Becherer.


Disaster 2. Severe thunderstorms swept across parts of the Rockies and Plains on July 28 - 29, causing $1 billion in damage. Hardest hit was Colorado, where golf-ball-and-larger-sized hail struck the Colorado Springs metro area. Hail accumulations up to one feet (0.3 meters) fell in some areas, and torrential rains led to flash flooding. Heavy losses were also reported in Wyoming, Kansas, Nebraska, and South Dakota. In this image, we see an intense thunderstorm building over Boulder, Colorado on July 29, 2016. Image credit: wunderphotographer austncitylimits.

September

Disaster 1. After topping out as one of Earth’s top-ten strongest tropical cyclones on record, with a central pressure of 890 mb and sustained winds of 190 mph, Super Typhoon Meranti weakened to Category 2 strength before making landfall in China’s Fujian Province on September 15. Meranti killed 42 people and did $2.5 billion in damage to China. In Tawian, two people were killed, and damage was over $70 million. Above, we see the eye of Meranti directly over the Philippines’ Itbayat Island in a moonlight image from Japan’s Himiwari-8 satellite taken at 17:32 UTC September 13, 2016. Itbayat recorded sustained winds of 112 mph (10-minute average) and a pressure of 934 mb at 1 am local time, 32 minutes prior to this image. At the time, Meranti was a Category 5 storm with 190 mph winds--tied for the strongest landfalling tropical cyclone in world recorded history. No deaths or injuries were reported on the island, but there was heavy damage.

October

Disaster 1. Category 5 Super Typhoon Chaba peaked at 165 mph winds south of Okinawa, Japan on October 3 before weakening to a Category 1 storm as it grazed South Korea on October 5. Southern South Korea was the hardest hit, with 10 fatalities as well as the large majority of the $1 billion in damage from the storm. In this image, we see an International Space Station view of the typhoon taken at 08 UTC October 3, 2016 when the storm was at peak intensity: a 905-mb central pressure and sustained winds of 165 mph.


Disaster 2. Category 4 Hurricane Matthew devastated Haiti on October 4, killing 546, making it the Atlantic’s deadliest hurricane in 11 years. Damage in Haiti was estimated at $1.9 billion--a staggering 21% of the impoverished nation’s GDP, and by far Haiti’s costliest hurricane on record, according to the international disaster database, EM-DAT. Matthew battered Cuba as a Category 4 storm, causing $2.6 billion in damage (3.2% of their GDP.) The Bahamas suffered $600 million in damage from Matthew (6.8% of GDP). Matthew grazed the coast of Florida and Georgia before making landfall in South Carolina on October 8 as a Category 1 hurricane with 75 mph winds. Matthew killed 49 people in the U.S., 28 of them in North Carolina. U.S. damage was estimated at up to $10 billion. This would make Matthew the 17th most expensive hurricane in U.S. history. Remnant moisture from Matthew also brought flooding rains and high winds to parts of the Maritime Provinces of Canada, causing tens of millions of dollars in damage. In this image, we see a small town along the southwestern coast of Haiti that suffered extreme storm surge damage from Hurricane Matthew. For a detailed look at Matthew’s aftermath at Haiti, see our guest post from December 16, 2016, by Andrew Kennedy and Tracy Kijewski-Correa, who visited the most-affected regions and evaluated the storm’s impact. Image credit: United Nations Stabilization Mission in Haiti (MINUSTAH), via univision.com.

November

Disaster 1. Extreme drought contributed to deadly fires that roared through Gatlinburg, Tennessee on November 28, killing 14 and causing at least $1 billion in damage. In this image, we see smoke rising from destroyed buildings on November 29, 2016, at the Westgate Smoky Mountain Resort & Spa above Gatlinburg. Image credit: Paul Efird/Knoxville News Sentinel via AP.

A big thanks goes to Steve Bowen of Aon Benfield for helping out with our many questions on disaster stats. We’ll be back with a new post on Wednesday afternoon.

Jeff Masters and Bob Henson

Climate Summaries

Updated: 4:54 PM GMT on March 06, 2017

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From Freezing Rain to Giant Hail, Great Plains Endure An Icy Weekend

By: Bob Henson , 4:47 PM GMT on January 16, 2017

Freezing rain materialized as expected during the weekend over a large swath of the central U.S., from Texas to Illinois. The ice has been widespread and prolonged, yet the ingredients haven’t come together as they could have for a truly catastrophic ice storm. Temperatures have been borderline--near or just below freezing over large parts of the affected area--and in many cases the ground was still warm enough to help keep surface ice to a minimum. Rainfall wasn’t quite as heavy as feared on the cold side of this storm; ice accumulations have been below 0.5” in most areas. In addition, temperatures crept upward through the weekend across the southern part of the ice belt, which allowed much of the ice to melt in place. Also helping reduce the storm’s impact: winds were mostly on the light side, which reduced damage to ice-coated trees and power lines.

There was still plenty of slipping and sliding for many thousands of central U.S. residents. At least six highway deaths have occurred during the storm, according to a weather.com roundup. Some 10,000 customers reported lost power in Oklahoma, mainly in the state’s northwest half, together with more than 12,000 customers still without power in the Texas Panhandle as of Monday morning. The hardest-hit area extended from the Texas and Oklahoma Panhandles into southwest Kansas, which experienced several rounds of showers and even thunderstorms gliding atop surface air that stayed below freezing. In Dodge City, KS, power was knocked out to hundreds of customers. Embedded at bottom is a photo from Liberal, KS, where photographer Michael Strickland tweeted, “It almost sounds like thunder from all the branches.”


Figure 1. Mary Zinser scrapes a thick layer of ice off her windshield in Arnold, MO, on Friday, Jan. 13, 2017. A thick glaze of ice covered roads from Oklahoma to southern Illinois on Friday amid a winter storm that caused numerous wrecks, forced school cancellations, grounded flights and prompted dire warnings for people to stay home. (David Carson/St. Louis Post-Dispatch via AP)

By early Monday, the main upper-level system and surface low had become stacked over Kansas, which pushed a surge of freezing rain further north into southeast Nebraska and most of Iowa. Air temperatures hovered close to freezing, but colder ground temperatures in this area facilitated glazing on untreated and less-traveled highways, streets, and sidewalks. Ice storm warnings remained in effect on Monday morning from southwest Kansas to central Iowa, with rainfall and drizzle expected to decrease from southwest to northeast as the day wears on.

Below are the largest state-by-state ice accumulations for the entire storm as of 8:00 AM CST Monday, as reported by the NOAA/NWS Weather Prediction Center.

Iowa: 0.25”, Knoxville
Illinois: 0.37”, near Maeystown
Kansas: 0.60”, Columbus
Missouri: 0.75”, near Aldrich
Nebraska: 0.30”, Grand Island
Oklahoma: 1.00”, Beaver
Texas: 0.50”, Canadian


Figure 2. Ice hangs from trees along a creek bed in North Tulsa, Saturday Jan. 14, 2017. Image credit: Jessie Wardarski/Tulsa World via AP.

Stormy night of football
One of two big pro-football playoff games--the Pittsburgh Steelers at the Kansas City Chiefs--was moved from Sunday afternoon to Sunday night to avoid the worst of the ice. Temperatures were just above freezing (33°F) by game time in Kansas City, with ice impacts minimal.

A much scarier situation developed with another playoff game--the Green Bay Packers at the Dallas Cowboys--that took place on the warm side of the central U.S. storm. A tornadic thunderstorm approached Arlington, TX, after the Packers-Cowboys game wrapped up on Sunday night. About 1000 people who had yet to leave AT&T Stadium were forced to shelter in place from just after 8:00 pm to 9:40 pm CDT as the storm swept overhead, with a tornado warning for Arlington at one point. Of the two confirmed tornadoes on Sunday, one struck in Grand Prairie, only about 5 miles southeast of the stadium. Severe weather will be on the decrease starting Monday, though a few storms could reach severe levels along and near the Gulf Coast during the week. Meanwhile, the eastern half of the United States and Canada are in for a long stretch of relatively mild weather for January.

Dallas-Fort Worth ended up with 3.16” of rain on Sunday, making it their second-wettest January day on record behind the 3.54” that fell on January 25, 2012. Fittingly for this weekend, one of the most dramatic severe weather reports was ice-related. Hailstones up to 4” in diameter crashed to the ground Sunday evening in Medina, about 40 miles west of San Antonio (see embedded photo below). Only a few storms produce hail this large in the United States during the month of January, according to Patrick Marsh (NOAA/NWS Storm Prediction Center). Hailstones as big as 5” fell in Arkansas on January 21, 1999, and Missouri on January 7, 2008.

We’ll be back with a new post by Tuesday afternoon. Happy Martin Luther King Jr. Day!

Bob Henson








Winter Weather Severe Weather

Updated: 5:07 PM GMT on March 06, 2017

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Icy Weekend for Central Plains; La Niña’s Days Are Numbered

By: Bob Henson , 5:33 PM GMT on January 13, 2017

Near-record levels of moisture for January will be flowing toward the Central Plains this weekend atop a paper-thin cold air mass at the surface--a classic set-up for widespread freezing rain. Ice storm warnings were in place Friday morning along a strip from northwest Oklahoma to southwest Illinois. These warnings indicate that enough freezing rain is expected in the next 12 to 36 hours (typically 1/4” to 1/2”, depending on location) to cause significant problems. Freezing rain advisories for lesser accumulations flanked the south side of the ice-storm-warning belt from the Texas Panhandle all the way to western Virginia, and winter storm warnings for a mix of frozen precipitation extended to the north of the ice storm warning from eastern Colorado to western Illinois. See the WU severe weather page for state-by-state warning roundups.

Ground Zero for the worst icing is likely to run from northwest Oklahoma into western Kansas, where the swath of heavy rain associated with an upper-level low moving through on Saturday night and Sunday will intersect with ground-level temperatures just cold enough for the rain to freeze. Odds are that some parts of the area will experience at least 0.5” of ice accumulation, according to the National Weather Service (see Figure 1). Travel could be quite rough for people heading to Kansas City, MO, for the pro-football playoff game on Sunday between the Pittsburgh Steelers and Kansas City Chiefs. An ice storm warning is in effect till midnight Sunday night. It appears that temperatures above freezing will sweep north across the city during the day on Sunday, but as with football, timing is everything.


Figure 1. The highest odds for at least 0.5” of freezing rain accumulations this weekend (from 6:00 AM CST Friday, January 13 to 6 AM CST Monday, January 16) are across western and central Kansas, where some areas have a better-than-70% chance. Image credit: NWS Weather Prediction Center.

How long can the surface cold last?
A big limiting factor that could keep this ice storm short of widespread devastation is the steady erosion of the surface cold air mass expected this weekend. There’s little push behind the cold air mass at this point, while southerly winds just above the surface will be intensifying throughout the weekend. Thus, most of the ice-affected areas will transition to milder temperatures by the end of the storm. The rain itself will help warm up the surface air mass by releasing heat as it freezes and by pulling down warmer air from above, especially where it’s raining the hardest. Thunderstorms could develop as far north as Kansas by late Saturday, and there’s even a slight chance of severe weather over parts of west Texas on Sunday, according to NOAA’s Storm Prediction Center.

Ice storms aren’t uncommon in the central states in midwinter, but the degree of warmth and moisture flowing atop this one is quite unusual. The 06Z Friday run of the NAM model projected that the amount of water in a column above the surface (precipitable water, or PW) will be close to record levels for January in some of the ice-affected areas, especially as the storm shifts to a non-frozen rain event. Here are some of the peak NAM-predicted ranges compared to January records in radiosonde databases that extend back to the mid-20th century:

Amarillo, TX: 0.80” - 0.90” (Jan. record 0.84”)
Dodge City, KS: 0.80” - 0.90” (Jan. record 0.85”)
North Platte, NE: 0.55” - 0.65” (Jan. record 0.65”)
Topeka, KS: 0.90 - 1.00” (Jan. record 1.08”)
Omaha, NE: 0.80” - 0.90” (Jan. record 0.95”)


Figure 2. Winds about a mile above sea level (850 mb) will bring very moist air for midwinter into the Southern and Central Plains this weekend. By 6:00 PM CST Saturday, the amount of precipitable water through the depth of the atmosphere will be 4 to 6 standard deviations above average in the blue-shaded areas. Image credit: tropicaltidbits.com.

The ground is well above freezing across much of Oklahoma, with soil temperatures Friday morning between 35°F and 45°F, so it’s quite possible that icing in central Oklahoma will be more prominent on bridges and overpasses, trees, and power lines than on roads, especially toward the southern parts of the affected areas. The radius of ice accumulation on items such as limbs and power lines is typically about 20% to 40% of the total amount of rain that falls during an ice storm, according to a recent Weather and Forecasting paper by meteorologists Kristopher Sanders and Brian Barjenbruch (NWS/Topeka, KS).

Power outages may affect many thousands of people across the Central Plains this weekend--and these can take days to repair, especially if they’re widespread. Fortunately, the odds of widespread inch-or-more ice accumulations seen in the worst ice storms (see this weather.com roundup for graphic examples) appear to be on the low side. “While this storm will not likely be equivalent to the catastrophic ice events of the past 16 years, it'll be bad enough,” predicts Oklahoma-based meteorologist Jim Ladue.

Warmest Inauguration Day on record? It’s possible
In the wake of the ice storm, westerly Pacific flow will sweep across the nation, bringing a sharp mid-January warm-up to most areas east of the Rockies. Readings of 20°F - 30°F above average will be widespread, with temperatures above 50°F possible as far north as Michigan and New York by next weekend.


Figure 3. As of Friday morning, January 13, 2017, WU’s forecast for Ronald Reagan Washington National Airport is for temperatures in the mid-50s around noon on Friday, January 20.


Presidential inaugurations were held on March 4 from 1793 until 1937, when the date was shifted to January 20 (when those dates fell on Sundays, the inaugurals occurred a day later, as was the case in 2013). Capital Weather Gang notes that, perhaps surprisingly, the highest midday temperature recorded for any inauguration was just 55°F, measured at noon on both March 4, 1913 (Woodrow Wilson) and January 20, 1981 (Ronald Reagan). In records going back to 1872, daily highs in D.C. have been as high as 70°F on January 20 (in 1950) and 82°F on March 4 (in 1983), but since inaugurals happen only every four years, the historical temperature range for these events is quite constricted. WU’s most recent forecast for Washington, D.C., is for a noontime temperature around 56°F on Friday, January 20. There is inherent imprecision in a 7-day temperature forecast, but the basic outlook for a warm inaugural--perhaps the warmest on record, apart from out-of-season swearings-in--appears quite solid.

So long, La Niña
In its latest monthly advisory, issued Thursday, NOAA’s Climate Prediction Center all but sounded the death knell for the 2016-17 La Niña. Sea surface temperatures in the benchmark Niño3.4 region have remained in the weak range for La Niña (0.5°C to 1.0°C below the seasonal average), and the subsurface cold relative to average across the equatorial Pacific has almost completely vanished. In a new ENSO Blog entry, NOAA/CPC’s Emily Becker reviews global weather conditions and how they’ve stacked up against La Niña expectations (fairly well, especially for temperature).

Models are close to unanimous in bringing the Niño3.4 region into the neutral range over the next couple of months. There are some model indications of a weak El Niño kicking in by summer 2017. That wouldn’t shock me, given the continued predominance of a positive Pacific Decadal Oscillation. Positive PDOs are associated with a higher frequency of El Niño events, and the PDO has now been in positive territory in each month from January 2014 through December 2016—the first time this has happened across three consecutive calendar years in records that go back to 1900. Even so, NOAA’s Emily Becker isn’t ready to predict a 2017-18 El Niño: “A three-year series of El Niño/La Niña/El Niño has only happened once since 1950, in 1963/1964/1965. This doesn’t make it impossible that El Niño could develop, but it means that we aren’t counting on it.”

We’ll be back with a new post on Monday. Have a safe weekend, everyone!

Bob Henson


Figure 4. One of the worst ice storms in the region’s history struck northeast TX, southeast OK, Arkansas, and northern LA in late December 2000, knocking out power to more than half a million people. J.D. Willhelm took this shot in Fort Smith, Arkansas, the day after Christmas. “If you don’t think people sweat during this kind of weather you should have seen the folks in the house below this tree,” he wrote. “Fortunately the tree survived but many in the area didn’t.” Image credit: wunduerphotographer JDWillhelm.



Winter Weather El Niño La Niña

Updated: 5:06 PM GMT on March 06, 2017

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As Earth Warms Up, The Sun Is Remarkably Quiet

By: Bob Henson , 8:09 PM GMT on January 11, 2017

If you’re looking toward the sun to help explain this decade’s record global heat on Earth, look again. Solar activity has been below average for more than a decade, and the pattern appears set to continue, according to several top solar researchers. Solar Cycle 24, the one that will wrap up in the late 2010s, was the least active in more than a century. We now have outlooks for Cycle 25, the one that will prevail during the 2020s, and they’re calling for a cycle only about as strong as--and perhaps even less active than--Cycle 24.

Weak solar cycles tend to produce fewer solar storms, those dramatic bursts of magnetized material from the sun that generate spectacular auroral displays and play havoc with satellite-based systems and power grids on Earth. However, solar storms that do emerge during weak cycles can be among the most potent, notes Scott McIntosh (National Center for Atmospheric Research). Just as a catastrophic hurricane can occur in an otherwise quiet season, a quiet solar cycle can still cause devastating space weather, McIntosh told me. “If you look at the record of extreme events from the sun, they most often occur in weak cycles, and they almost always occur in the deep, descending part of the cycle,” he said.

When scientists like McIntosh fret about the potential consequences of a solar storm, they often point to the Big One: the outburst from September 1-2, 1859, that’s been dubbed the Carrington Event. Occurring near the peak of a fairly quiet cycle, the Carrington Event was an extremely intense solar flare aimed directly at Earth. It produced stunning auroral displays around the globe, even in Cuba and Hawaii. The barrage of magnetized particles also knocked out telegraph communications across Europe and North America. A 2013 study from Lloyds of London (see PDF) found that a similar event today could cause up to $2.6 trillion in damage, with up to 40 million Americans losing power for anywhere from two weeks to two years. “While the probability of an extreme storm occurring is relatively low at any given time, it is almost inevitable that one will occur eventually,” noted the report. In fact, we dodged a major solar bullet in July 2012, when a flare roughly as strong as the one in 1859 happened to point away from Earth instead of toward it. See this 2009 post by Jeff Masters for more on how a solar storm can disable electric grids.



Figure 1. Solar material bursts from the sun in this close-up from a video captured on July 9-10, 2016, by NASA’s Solar Dynamics Observatory, or SDO. The sun is composed of plasma, a gas in which the negative electrons move freely around the positive ions, forming a powerful mix of charged particles. SDO captured this image in wavelengths of extreme ultraviolet light, which are typically invisible to our eyes. The imagery is colorized here in red for easy viewing. Image credit: NASA/SDO/GSFC/Joy Ng.


Climate and the solar cycle
The solar cycle, which is about 11.5 years long on average (it varies from 9 to 14 years), can be measured in various sophisticated ways. It’s also trackable simply by counting sunspots, an activity that dates back to the 1600s. The weakest cycles on record occurred during the so-called Maunder Minimum, from about 1645 to 1715. This happens to coincide with the peak of the Little Ice Age, which brought long stretches of conditions far colder than today’s climate to parts of North America and Europe. We can’t pin the Little Ice Age entirely on the Maunder Minimum, though, since volcanic eruptions appear to have kicked things off centuries earlier. It’s now believed that the Maunder Minimum played a minor role at best in sustaining the chill, though it does appear that weak solar periods can lead to colder winters in Europe, based on centuries of data from central England.


Figure 2. International Sunspot Numbers (one of two leading measures of sunspot activity) show the dip in sunspots during the Maunder Minimum as well as the ups and downs of each solar cycle through the mid-2010s. The current solar cycle (Cycle 24, only partially depicted here) reached dual peaks in 2011 and 2014, with a top ISN just over 100. This was the lowest top ISN for a solar cycle since Cycle 14, which peaked in 1906. Image credit: David Hathaway, NASA.


Newly precise measurements confirm that the total solar energy reaching Earth actually doesn’t change all that much from cycle to cycle. As a single cycle ramps up from minimum to maximum, the sun spits out as much as 10 times more energy in extreme ultraviolet wavelengths. However, the sun’s total energy output (irradiance) goes up by a mere 0.1% during a solar cycle, and this boosts global surface temperature by no more than 0.1°C per cycle, according to the Intergovernmental Panel on Climate Change.


Figure 3. Global temperature change (thin light red line), as reported by NASA/GISS, together with the annual total solar irradiance, or TSI (thin light blue). The dark red and dark blue lines show the 11-year moving averages. Data sources: Temperature from NASA GISS, and TSI from 1880 to 1978 from Krivova et al 2007 (data). TSI from 1979 to 2015 from PMOD (see the PMOD index page for data updates). Image credit: Courtesy skepticalscience.com.

What makes a solar cycle?
As with many solar cycles, Cycle 24 had a double peak, in 2011 and 2014, and it’s still on its downward swing, as evident in the Solar Cycle Progression graphics at the website of NOAA's Space Weather Prediction Center. Cycle 24 isn't expected to end until around 2020. (Each cycle is defined as starting when the previous one bottoms out). New approaches to prediction are lending more confidence in scientists’ ability to predict how the upcoming minimum and the following maximum--which should arrive in the mid-2020s--will unfold.

The prevailing notion among solar experts is that plasma flows through the sun in two giant loops that cause the solar cycles to wax and wane. As it flows equatorward, the plasma carries magnetic fields with it, generating sunspots and other features at the surface. Magnetic fields that rise to the surface of the poles during solar minimum are believed to serve as the raw material for the subsequent cycle’s strength. As these magnetic fields drift toward the solar equator, they get stretched and distorted, which helps to trigger sunspots as well as outbursts of charged plasma that can hurtle toward Earth and cause solar storms. The distortion occurs because the gaseous solar sphere actually moves with a faster rotation rate as you go toward its equator, like a sphere made of taffy that’s mounted on a spindle and spun along its midsection. (This NASA animation shows the process in three dimensions, including a rendition of the poorly understood flow beneath the solar surface.)

Unfortunately, the sun’s magnetic fields are very hard to observe, especially near the poles, which complicates the task of predicting the next solar cycle. However, some phenomena related to the polar fields are easier to measure, such as a minimum in geomagnetic activity (the flow of energy reaching Earth via the solar wind). Over the last several cycles, such indices have been extremely well correlated with the strength of the following cycle peak, with correlations as high as 0.99.

Outlook for the 2020s: Another modest cycle
The community of solar researchers has only recently come into consensus on the “polar predictor” method of using polar magnetic fields as the best predictor of solar cycles. A decade ago, various methods produced conflicting results on how strong Cycle 24 would end up. Forecasts based on polar fields at solar minimum did remarkably well; others had more trouble in capturing the cycle’s length and strength. “One of the things we learned is that the difference between the hemispheres is critical,” said McIntosh. The north half of the sun ran about two years ahead of the south during Cycle 24, and that overlap led to the double-peaked maximum (2011 and 2014) while lessening the cycle’s overall peak strength.

Researchers are now trying to push the limits of prediction further. They’re using statistical and dynamical models, plus some data-based intuition, to predict several years in advance how the subsurface magnetic fields will look when they emerge near the poles around 2020, and what, in turn, those fields may tell us about Cycle 25.

• David Hathaway (recently retired from NASA) and Lisa Upton (NCAR and Space Systems Research Corporation) expect a Cycle 25 about as strong as Cycle 24, or perhaps slightly weaker. They published their outlook in November in the Journal of Geophysical Research. Hathaway and Upton used an ensemble model to project the polar fields from now to the end of 2019, with the ensemble showing an uncertainty by that point of about 15%. Natural solar variations in the early 2020s could add to the uncertainty, they note.

• Leif Svalgaard (Stanford University) pioneered the idea of using solar polar fields as prediction tools with colleagues in the 1970s, and he successfully pegged the eventual weakness of Cycle 24 back in 2005. Svalgaard is calling for a weak Cycle 25, but perhaps just a bit stronger than Cycle 24, based on precursors that appear slightly more active this time around.

• NCAR’s McIntosh believes Cycle 25 could extend the recent string of progressively weaker cycles. “We anticipate that the growing degree of overlap between cycles means that Cycle 25 will be weaker than Cycle 24,” he told me.

• Also at NCAR, Mausumi Dikpati will release her outlook for Cycle 25 in a paper to be published later this year. Dikpati and colleagues predicted a stronger-than-average Cycle 24 (as did Hathaway and others). This didn’t materialize, but Dikpati did correctly forecast that Cycle 24 would begin later than usual. Dikpati is now doing a post-mortem on her Cycle 24 forecast, which was based on a pioneering model of the solar dynamo (the flow of plasma that produces magnetism within the sun). As with weather models, she expects that improved data assimilation--bringing the latest observations into the solar dynamo model--will help boost its accuracy.


Figure 4. A composite of 25 separate images from NASA's SDO, spanning one year from April 2012 to April 2013. The image reveals the migration tracks of active regions towards the equator during that period. Image credit: NASA/SDO/Goddard.

Tweaking the time frame of solar forecasts
Even if we have several more decades of a quiet sun ahead of us--a “grand minimum,” which is quite plausible according to recent work published by McIntosh and others--we know that quiet cycles can produce dangerous solar storms, so there’s plenty of motivation to push ahead with solar forecasting. This includes predicting variations that last only a few months to a year or two. Dikpati is leading a team with participants from NCAR, NOAA, Stanford, and the University of Colorado Boulder in order to help advance this type of prediction. Their goal is to use data-infused models to predict solar activity and the likelihood of solar storms a few months in advance. “A seven-day lead-time forecast of weather on Earth covers a period of seven Earth rotations,” Dikpati said in an email. “Similarly, forecasting bursts of solar activity up to seven solar rotations ahead would mean about six months of lead time, since one solar rotation takes about 27 days.”

Every bit of advance notice on the likelihood of dangerous solar storms could be invaluable in a world ever more dependent on reliable power and communications. The potential benefits of cycle forecasts include making satellite projects less risky and more efficient. That’s because the solar cycle can cause air density at low-earth-orbit heights to vary tenfold, vastly altering the atmospheric drag on satellites. Even the most ambitious plans for outer space have a stake in better solar outlooks, according to Svalgaard, who cites this quote from colleague Dean Pesnell (NASA): “A society that travels to other planets needs forecasts of the solar activity visible from any point in the solar system several years in advance.”

We’ll be back with a new post on Friday, including a look at a major late-week/weekend storm that’s still on track to coat large parts of the central U.S. with dangerous freezing rain.

Bob Henson

Space Weather Climate Change

Updated: 5:00 PM GMT on March 06, 2017

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Second-Warmest Year in U.S. Weather History, and Among the Wettest

By: Bob Henson , 5:33 PM GMT on January 10, 2017

Only 2012 ranks ahead of 2016 for average temperature across the 48 contiguous states, said NOAA’s National Centers for Environmental Information on Monday in its yearly U.S. climate report. The second-place showing follows a third-place ranking in 2015 (see Figure 1), which means that the last five years (2012 - 2016) have produced the three warmest years in U.S. records extending back to 1895. This national-scale warmth is a reflection of global-scale trends consistent with a climate being warmed by human-produced greenhouse gases. It’s virtually certain that 2016 will be certified this month as the warmest year on record globally, which would make it the third such record-setter in a row.

The average 48-state reading of 54.91°F in 2016 was 2.89°F ahead of the 20th-century average and 0.37°F shy of the 2012 record. Geographically, the nation’s warmth in 2016 was astoundingly uniform, with every contiguous U.S. state having at least its seventh warmest year (see Figure 2). Georgia had its warmest year on record, as did Alaska, which isn’t part of the contiguous U.S. database.


Figure 1. Year-by-year average temperature for the 48 contiguous U.S. states from 1895 to 2016. The three warmest years have all occurred since 2012. The current U.S. climate is roughly 1.5°F warmer than it was a century ago, with much of that warming observed since the 1980s. Image credit: NOAA/NCEI.


Figure 2. Statewide rankings for average temperature in 2016 as compared to each calendar year since 1895. Darker shades of orange indicate higher rankings for warmth, with 1 denoting the coldest year on record and 122 the warmest. Image credit: NOAA/NCEI.


Figure 3. Month-by-month rankings for U.S. temperature and precipitation in 2016, including the average temperature, daily maximum and minimum temperature (each calculated locally before being averaged nationally), and precipitation. Higher numbers denote a warmer or wetter placement among the 122 years in the NOAA database, which extends back to 1895. Data credit: NOAA/NCEI.


Warmest nights on record
Sultry summer nights--and mild winter nights--did more than their share to put 2016 near the top of the U.S. temperature heap. Averaged across the nation and year, the daily minimum temperature was the warmest in U.S. history, at 3.09°F above the long-term mean (beating out 2012). The average daily maximum temperature came in at 2.69°F above the 20th-century average, placing third behind 2012 and 1934. Relative to average, lows were warmer than highs for every month in 2016 except February and March, as shown in Figure 3.

The year’s U.S. warmth was well distributed across the calendar, with two noteworthy exceptions evident in Figure 3 above: May and December.

Record highs outdid record lows by an unprecedented ratio
What’s not obvious in the maps and figures above is how seldom U.S. towns and cities set or tied daily record lows in 2016, thanks in large part to the mild nights noted above. The preliminary total of daily record lows for the year was 5188--barely half of the total recorded in any other year since 30-year climatologies became established in the 1920s, according to independent meteorologist Guy Walton, who has compiled and tracked NOAA records data for more than a decade. Meanwhile, there were 29,729 daily record highs, a large but not unusual number for recent years. Juxtaposed, the ratio of daily highs to daily lows was around 5.7 to 1, the largest for any year in the post-1920s database, according to Walton. Overall for the 2010s (defined as 2010 - 2016), we’ve seen more than double the number of daily record highs versus lows, with the ratio of 2.1 to 1 just above the 1.9-to-1 ratio observed in the 2000s.

A wet year overall, but with plenty of variability
Wild spatial and temporal swings were the order of the year in 2016 when it comes to precipitation. Averaged by month, June was the 14th driest on record for the contiguous U.S., while August was the 2nd wettest, as shown in Figure 3. The tendency toward drought east of the Mississippi, and the very moist conditions that prevailed in the upper Midwest (as well as flood-hammered Louisiana), is evident in the state-by-state precipitation map (Figure 5 below). The year as a whole was the 24th wettest on record. Three states had a top-ten driest year--Connecticut, Georgia, and Massachusetts--while Michigan, Minnesota, North Dakota, Wisconsin saw top-ten wet years.

Averaged linearly and nationally, the contiguous U.S. has seen annual precipitation climb from about 29” in the 1890s to about 31” in the 2010s. Of course, that overall rise masks the hugely important swings observed from region to region and year to year.


Figure 4. Year-by-year ranking of average precipitation for the 48 contiguous U.S. states from 1895 to 2016. Image credit: NOAA/NCEI.


Figure 5. Statewide rankings for average precipitation in 2016, as compared to each year since 1895. Darker shades of green indicate higher rankings for moisture, with 1 denoting the driest year on record and 122 the wettest. Image credit: NOAA/NCEI.

A less-crazy December
The parade of midlatitude storms marching across the U.S. in December, a feature characteristic of La Niña winters, led to a fairly unremarkable monthly temperature outcome. It was the 54th coldest and 34th wettest out of the 122 Decembers on record. The La Niña tendency toward cooler-than-average readings toward the northwest and warmer-than-average readings toward the southeast is evident in Figure 6. Florida was the only state with a top-ten temperature result, as it sweated its way through the fourth warmest December on record. Five states--Minnesota, Nevada, North Dakota, South Dakota, and Wyoming--saw a top-ten wettest December (see Figure 7). Moisture has been plentiful across the West apart from the Northern Rockies, and the widespread snowpack now building up (see Figure 8) will be much appreciated by skiers and boarders this winter and by farmers and ranchers next summer.

Jeff Masters and I will have more next week on the natural disasters of 2016, both national and global, as well as how 2016 stacked up in terms of global temperature. We’ll be back with our next post by Wednesday afternoon.

Bob Henson


Figure 6. Statewide rankings for average temperature during December 2016, as compared to each December since 1895. Darker shades of orange indicate higher rankings for warmth, with 1 denoting the coldest December on record and 122 the warmest. Image credit: NOAA/NCEI.


Figure 7. Statewide rankings for average precipitation during December 2016, as compared to each December since 1895. Darker shades of green indicate higher rankings for moisture, with 1 denoting the driest December on record and 122 the wettest. Image credit: NOAA/NCEI.


Figure 8. The amount of water held in snowpack as of January 10, 2017, relative to the average for this date for the period 1981-2010. Image credit: USDA/NRCS and National Water and Climate Center.

Climate Summaries

Updated: 4:58 PM GMT on March 06, 2017

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Winter Storms Hustle Across United States; Ice Potential Rears Its Head for Late Week

By: Bob Henson , 7:00 PM GMT on January 09, 2017

The much-anticipated twin winter storms affecting the U.S. West and East Coasts over the weekend brought many, if not most, of the predicted impacts. A nose of warm air pushed further inland than expected over the Southeast, which kept snow totals near the low end of hopes and/or fears from northern Georgia (central Atlanta missed out completely on snow accumulations) to southeast Virginia. Update: Parts of the Hampton Roads, VA, area picked up less than 6", but updated maps show that a swath of 9" - 12" totals extended from central VA across the northern Hampton Roads area and onward to the Delmarva.


Figure 1. Snow lovers in the Atlanta area were mostly disappointed as freezing rain and sleet predominated during the winter storm on Friday and Saturday, January 6-7, 2017. In this scene, ice covers a fence in Atlanta’s Piedmont Park on Saturday. Image credit: AP Photo/David Goldman.


Figure 2. Snow totals from this past weekend (Jan. 6-8, 2017) illustrate how dramatically accumulations from a snowstorm can vary across the New York/Long Island area. Image credit: NWS/New York.

It did turn out to be a wild Saturday night across eastern Long Island and southeast Massachusetts, where blizzard and near-blizzard conditions were the rule and snow amounts were impressive. Orient Point, NY, racked up a storm total of 12.5”, and an observer in East Bridgewater, MA, reported 19.5”.

A brief but intense shot of cold followed the snows across the South and mid-Atlantic. Oklahoma City, OK, dipped to -3°F on Sunday, tying the record for the date; it’s only the second time OKC has made it below 0°F this century (the other was -5°F on Feb. 10, 2011). Richmond, VA, dropped to 0°F on Monday, breaking the daily record of 1°F set in 1940, and Westhampton, NY, plummeted to -9°F, among the coldest readings since observations began there in 1951.


Figure 3. A firefighter from Sparks, NV, takes a picture of the rising Truckee River on Sunday, January 8, 2017, where it runs near the Grand Sierra hotel-casino along a line that divides the cities of Reno and Sparks. The Truckee crested in Reno early Monday morning. More than 1,000 homes were evacuated due to overflowing streams and drainage ditches in the area, which remains under a flood warning through Tuesday. Image credit: AP Photo/Scott Sonner.

Hellacious winds, rain, and snow batter the Sierra
Residents of central California and western Nevada dodged floods and mudslides on Monday after a powerful Pacific storm system blitzed the area. Rainfall amounts ended up falling short of the most ominous projections across most lower elevations of central California, with about 2” falling in San Francisco and about 2.5” in Sacramento. Although street flooding was widespread across the Bay Area, it wasn’t extreme by historical standards. At mid-morning Monday, only 21 of 397 river gauges across central California and western Nevada were experiencing flood conditions.

The storm came closer to expectations in and near the Sierra, where huge amounts of precipitation fell, switching from snow to rain and back to snow at some elevations. Liquid-water equivalents (rain and snowmelt equivalent) for the 48 hours through Monday morning ranged from 5” to more than 13” across the northern Sierra. The inundation pushed the Truckee River out of its banks in the downtown Reno/Sparks area. Many roads were closed in the area, including parts of Interstate 80 in both Nevada and California. About 25 miles east of Reno, the Truckee was in major flood stage near Wadsworth on Monday morning. Perhaps the single most impressive statistic of the event came on Sunday morning, as wind gusts hit a phenomenal 174 mph near the summits of the Squaw Valley ski area.


Figure 4. Wind gusts topped out at 174 mph at an automated station on the summit of California’s Ward Mountain, located in the Squaw Valley ski area just west of Lake Tahoe, at 11:00 am PST Sunday, January 8, 2017. Sustained winds were in the vicinity of 100 mph for hours. Image credit: NWS/MesoWest.


Figure 5. A 2006 photo of California’s Pioneer Cabin Tree and its iconic tunnel in Calavares Big Trees State Park. Image credit: Wikimedia Commons/NX1Z.

Pioneer Cabin tree bites the dust
The most famous victim of the weekend storm was the Pioneer Cabin tree in Calavares Big Trees State Park. Iconic for the passageway carved into its base in the 1880s, it was one of the oldest and most venerable of the “drive-through” trees that were a California staple for decades until the rise of environmental consciousness put them out of style. Located in a grove of dozens of giant sequoia trees, some believed to be as old as 2000 years, Pioneer Cabin tree was barely hanging on. Joan Allday, a volunteer at the state park, told SFGate that “there was one branch alive at the top.” A combination of high wind and sodden soil dealt the tree its final blow early on Sunday afternoon. Calaveras Big Trees Association has a memorial page on Facebook in honor of the felled giant.

More winter storminess ahead this week
There’s not much of a break in store for storm-battered central California. Another wet system will roll through the region Tuesday and Wednesday, and there is no sign of the active Pacific storm track leaving the area anytime soon, which will boost the risk of significant flooding over time. Floodgates on the Sacramento River upstream from the city of Sacramento are being opened by the California Department of Water Resources for the first time since 2005.

Toward Friday and Saturday, we’ll have to keep a close eye on a late-week Pacific storm that may pull extreme amounts of moisture for midwinter atop an Arctic air mass predicted to be lodged over the southern and central Great Plains and mid-Mississippi Valley. The cold surface air will be too shallow for snow, and perhaps even for sleet, so rain and freezing rain appear to be the most likely precipitation types--and the amounts could be quite large (see Figure 6 below). This set-up bears many of the classic earmarks of a major ice storm, but it’s way too early to know whether reality will Iive up to some of the high-end model projections, which are indeed ominous. To produce a worst-case scenario, the arrival and departure of the Arctic air mass would have to be well synchronized with the timing of the heaviest rain. Even if the ice does materialize, it could affect only a narrow strip along the north edge of the heavier rain, and that location will be difficult to pin down more than a day or two in advance. The potential is worth taking seriously, though, especially from the Texas Panhandle to Missouri and perhaps eastward as far as Ohio. NOAA’s Weather Prediction Center warned on Monday in its national extended forecast discussion that “a major icing event is possible” across parts of OK/KS/MO, and the NWS office in OKC/Norman issued an extensive and candid discussion of the scenario.

We’ll be back with a new post on Tuesday on the U.S. climate roundup for December 2016 and the year as a whole.

Bob Henson


Figure 6. Predicted 7-day precipitation totals (rain and snowmelt equivalent) for the period from 12Z (7:00 am EST) Monday, January 9, 2017, through Monday, January 16. Nearly all of the precipitation depicted in the southern Great Plains is forecast to occur from Thursday into the weekend. Image credit: NOAA/NWS/WPC.


Updated: 3:07 PM GMT on February 21, 2017

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From California to Virginia, Winter Storminess Will Gird the U.S. This Weekend

By: Bob Henson , 5:05 PM GMT on January 06, 2017

Two storms carried by a powerful Pacific jet stream will play havoc with the lives of millions of Americans during the first full weekend of 2017. We can expect some of the heaviest wind-whipped rain and snow in years to strike parts of central California this weekend. In the Southeast, a significant belt of snow and/or ice will stretch from Atlanta to Norfolk, accompanied by high winds and bitter cold. The setups in both the East and West have the potential to produce localized record-setting amounts of rain and snow. Power outages in the Southeast could affect many thousands, while floods and avalanches will become a growing concern in California.


Figure 1. Winds at the jet-stream level (250 mb, or roughly 33,000 feet) were howling across the southern U.S. at speeds topping 120 mph in spots on Friday, January 6, 2017. The energy was undercutting a massive ridge of high pressure extending north into Alaska and eastern Siberia, with a weaker jet arcing above the ridge (top left). Image credit: Climate Reanalyzer/University of Maine.

California drenchin’
The atmospheric river predicted for days to strike the U.S. West Coast is still on track to arrive within about 100 miles of San Francisco Bay and proceed headlong into the Sierra Nevada over the weekend. Carrying vast amounts of moisture--more than four standard deviations above the mean--this onslaught of strong southwest flow should deliver widespread rains on the order of 4” or more from late Saturday into Monday across much of central California, including the cities of San Francisco and Sacramento. Single-day rainfall records include 5.59” for San Francisco International Airport (January 4, 1982; records go back to 1945) and 3.77” at Sacramento Executive Airport (October 13, 1962; records go back to 1941).

Where the flow impinges on mountains, the lower-elevation rain and higher-elevation snow will be phenomenal. As of Thursday, the new year (Sunday to Thursday) had already delivered 70” of snow to the Mt. Rose ski area, with 40” - 84” at Mammoth Mountain. A moderate avalanche risk will continue into at least Saturday, according to the Sierra Avalanche Center. Even with the snow level rising as warm, moist air is pumped in, the highest elevations of the Sierra will likely rack up several more feet of snow in just a day or two.

After the weekend system abates, at least two more significant winter storms could sweep across California during the following week, which will raise the potential for serious flooding. The National Weather Service in Sacramento is already noting that flood impacts in the area this weekend into early next week could be the worst since at least December 2005. The office warned in a tweet:

“Precipitation totals are forecast to be:
• once in a 10-25 year storm for areas SOUTH of I-80
• once in a 5-10 year storm for areas near and NORTH of I-80”



Figure 2. Precipitation totals predicted as of Friday morning, January 6, 2017, for the period from Saturday to Monday, Jan. 7-9. Image credit: NWS/Sacramento.

Complex winter storm across the Southeast
Ahead of California’s atmospheric river, another segment of the jet stream pushed Pacific moisture atop an Arctic air mass, producing heavy snow along Colorado’s Front Range. Boulder recorded 13.8” on Thursday, making it the city’s snowiest January day since 1962. The upper-level impulse continued racing across the Texas Panhandle and much of Oklahoma late Thursday, with several inches of fluffy snow on the ground from Amarillo to Oklahoma City by mid-morning and a second round of snow moving through the area.

A new low-level storm center organizing over the Gulf of Mexico on Friday will help wrap in moisture from the Gulf and Atlantic. The result will be a messy mix of wintry precipitation across much of the Southeast. Winter weather advisories for potential sleet and freezing rain extended to parts of southeast Louisiana and southern Mississippi, while the Atlanta area braced for 4” - 6” of snow expected late Friday. Even heavier snow could fall if the atmosphere chills down quickly enough, while a nose of warm air will favor sleet and cold rain closer to the Southeast coast.

The storm (dubbed Helena by The Weather Channel) will pack additional punch from the western and northern Carolinas into southeast Virginia. Widespread snowfall of 4” to 12” is expected across the region on Saturday, accompanied by strong winds and temperatures that will drop into the single digits by Monday morning. Experimental snowfall potential maps on Friday morning showed the risk of snow amounts as high as 13” north of Raleigh, NC, with up to a foot expected across the Hampton Roads area of southeast Virginia and the southern Delmarva. Even the northern Outer Banks of NC could pick up 3” or more; a winter storm warning was in effect for all of Dare County.

See the weather.com article on Helena for continuously updated state-by-state summaries from the Southeast. We'll be back with a new post on Monday. Stay safe this weekend, especially if you're in one of the storm-affected regions!

Bob Henson






Winter Weather

Updated: 5:01 PM GMT on March 06, 2017

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Top Ten Weather Events of 2016: #1 is No Surprise; #2 Will Surprise You

By: Jeff Masters , 2:27 AM GMT on January 05, 2017

The top weather story of 2016: Earth had its warmest year on record (again!) While the final numbers are not officially tabulated, 2016 appears certain to be the warmest year in every major dataset scientists use to track global warmth. The previous warmest year on record for Earth’s surface was set in 2015, which in turn broke the record set in 2014. The 3-year string of warmest years on record is the first time such an event has happened since record keeping began in 1880. One official record has already been announced: Earth’s warmest year in the 38-year satellite-measured lower atmosphere temperature record was 2016, beating a record that had stood since 1998, according to the University of Alabama-Huntsville (UAH.)

The first seven months of 2016 all set new monthly records for global heat in the NOAA database, giving the planet an unprecedented streak of fifteen consecutive record-warm months. February 2016 had the warmest departure from average of any month in recorded history, and July 2016 was the warmest month in recorded history in absolute terms. According to the World Meteorological Organization (WMO), 2016’s global temperatures were approximately 1.2°C above pre-industrial levels. About 0.2°C of this warming was due to the strong El Niño event that ended in May 2016, and the remainder was due to the long-term warming of the planet from human-caused emissions of heat-trapping gases like carbon dioxide. Assuming that all nations who agreed to the Paris Climate Accord in 2015 fulfill their pledges, Earth is on track to see 2.3°C of warming over pre-industrial levels by 2050. This is above the “dangerous” 2°C level of warming considered likely to greatly increase the risk of hunger, thirst, disease, refugees, and war.


Figure 1. Departure of the global surface temperature from average for the period January - November, for all years from 1880 to 2016. The year 2016 will easily beat 2015 as the warmest year on record. Image credit: NOAA.

2) Air Pollution in 2016 Likely Killed Over 5 Million and Cost Over $5 Trillion Globally
The deadliest and costliest weather events of 2016 were very likely high pressure systems with light winds and stagnant air that led to lethal build-ups of dangerous air pollutants in Asia. One such event, a severe air pollution episode being called The Great Smog of Delhi, hit the most polluted major city in the world—New Delhi, India—on November 1 - 9, 2016. On November 7, Delhi’s levels of the deadliest air pollutant—fine particulate matter (PM 2.5)—hit 999 micrograms per cubic meter, which is 40 times higher than the World Health Organization guideline of 25 micrograms per cubic meter for a 24-hour period. Sustained breathing of air pollution at these levels is like smoking more than two packs of cigarettes per day.


Figure 2. Traffic moving slowly under thick smog at ITO on November 4, 2016 in New Delhi, India. It was the worst smog in Delhi in 17 years. (Photo by Raj K Raj/Hindustan Times via Getty Images)

The worst air pollution episode of 2016 in China occurred the week of December 19, when levels of fine particle pollution in Shijiazhuang, capital of northern Hebei province, hit 1,000 micrograms per cubic meter—40 times the WHO standard. According to mashable.com, over 200 flights were cancelled in Beijing due to smog that week, schools and factories were ordered shut, and 23 cities declared smog red alerts. Too often, we hear about the costs of air pollution regulations, but nothing on the savings in lives and money that result from breathing clean air. Part of the problem is that quantifying the deaths and damage due to air pollution episodes is difficult. However, there are over 2,000 peer-reviewed scientific studies linking air pollution to "premature deaths”—mortality caused by air pollution that is only partly attributable to breathing bad air, but that would not have occurred otherwise. The World Bank estimated in 2016 that premature deaths due to air pollution in 2013 (the most recent year statistics were available) were 5.5 million people, at a cost of over $5 trillion. The total costs to countries in East and South Asia related to air pollution mortality were about 7.5 percent of GDP, they estimated. Additional health care costs to people who did not die were not considered, and neither was pollution damage done to agriculture. Computer modeling by Stanford professor Mark Jacobson in 2016 predicted that the total cost of air pollution globally under a business-as-usual emissions path will reach $23 trillion per year (7.6% of global GDP) by 2050.


Figure 3. Students took exams in an outdoor playground on December 19, 2016 in heavy smog at Linzhou, Anyang, in Central China's Henan Province. The fine particulate matter (PM 2.5) levels were in excess of 500 micrograms per cubic meter, which is 20 times higher than the World Health Organization guideline of 25 micrograms per cubic meter for a 24-hour period. The principal of the school was suspended after a public outcry. Image credit: An irate Linqi resident.

3) Longest Global Coral Bleaching Event on Record Devastates Great Barrier Reef
Earth’s third global coral bleaching event on record began in mid-2014, according to NOAA, and by mid-2016 had become the longest on record. The beaching event hit Australia’s Great Barrier Reef particularly hard, causing its greatest coral die-off ever observed. About two-thirds of the shallow-water coral on the reef’s previously pristine, 430-mile northern stretch died. The only thing that saved the southern portion of the 1,400-mile long reef was the passage of Tropical Cyclone Winston, which churned up the waters and cooled water temperatures by up to 3°C. The bleaching event was due to widespread ocean warming related to long-term climate change, as well as regional warmings triggered by a strong El Niño that began in early 2015. The prolonged nature of the bleaching event caused multiple years of damage during seasonal peaks in upper-ocean temperature, giving the reefs less time to recover, and the bleaching event is expected to continue into April of 2017, according to the latest four-month forecast from NOAA’s Coral Reef Watch. The alert level is lower in 2017 than it was in 2015 and 2016, though, thanks to the modest cooling of ocean waters in the Pacific due to the demise of the record-strength El Niño that had been in place. However, Dr. Mark Eakin, coordinator of NOAA’s Coral Reef Watch, said that “so many corals are pre-stressed that this could be enough to push more over the edge.”


Figure 4. Damage to the Great Barrier Reef in 2016 (left) as compiled by the Australian Government Great Barrier Reef Marine Park Authority, along with an image of bleached leather corals (right.) Only 7% of the reef escaped bleaching, and huge swaths of coral died. The Great Barrier Reef is the world’s largest living structure, and the only one visible from space. It contains more biodiversity than all of Europe combined, with 1,625 species of fish, 3,000 species of mollusk, 450 species of coral, 220 species of birds and 30 species of whales and dolphins. Image credit: Sirachai Arunrugstichai/Getty Images.

4) Drought Losses Low in the U.S., but Disturbingly High Globally
For the first year since 2011, losses from the multi-year drought in California in 2016 did not exceed $1 billion. There were no billion-dollar drought disasters in the United States in 2016, the first time that has occurred since 2010. However, drought losses globally were at least $17.6 billion in 2016, according to the November 2016 Catastrophe Report from insurance broker Aon Benfield. This ranked as the third highest economic loss due to drought in the past ten years, continuing a disturbing trend towards higher drought losses in recent years. Here is Aon Benfiled's list of drought damages globally since 2006:

2006: $11.0 billion
2007: $5.9 billion
2008: $3.7 billion
2009: $6.8 billion
2010: $9.0 billion
2011: $16.3 billion
2012: $34.8 billion
2013: $30.7 billion
2014: $13.7 billion
2015: $14.4 billion
2016: $17.6 billion

The trend towards higher drought losses in recent years is concerning, since drought is the greatest threat we face from climate change. I predict that an extreme global warming-amplified drought is likely to cause a Great Climate Disruption to civilization sometime in the next 40 years. As I wrote in my April 2016 post, Food System Shock: Climate Change's Greatest Threat to Civilization, I predict that the odds of climate change-amplified extreme weather events hitting multiple bread baskets where the majority of the world’s food supply is grown will increase to about a 2% chance per year by the middle of this century. This means it is likely that sometime in the next 40 years we will see a significant disruption of the global economy, intense political turmoil, war and the threat of mass famine due to extreme weather, with a global warming-amplified drought likely being the key catalyst. If you think modern civilization cannot collapse due to drought, history suggests otherwise: see my March 2016 post, Ten Civilizations or Nations That Collapsed From Drought.


Figure 5. Villagers throw containers attached to ropes into a well to collect their daily supply of potable water after a tanker made its daily delivery at Shahapur, India, on May 13, 2016. El Niño brought a second consecutive year of deficient monsoon rains in India during 2015. The resulting severe drought during the first half of 2016 cost India $5 billion and left 330 million people—a quarter of the population—with acute shortages of water. Image credit: INDRANIL MUKHERJEE/AFP/Getty Images

5) China’s $28 Billion Yangtze River Flooding: Most Expensive Disaster of 2016
Earth's official most expensive weather-related disaster of 2016—and the third most expensive non-U.S. weather-related disaster in world history—was the disastrous summer flooding in China’s Yangtze River basin. Torrential rains began in mid-May along the Mei-yu (or baiu) front, a semi-permanent feature that extends from eastern China across Taiwan into the Pacific south of Japan, associated with the southwest monsoon that pushes northward each spring and summer. A number of studies have found that the Mei-yu rainfall tends to be particularly heavy in the summer following an El Niño event, as occurred in 2016--and occurred in 1998, the only year to experience a more damaging flood in China. Heavier Mei-yu rains are expected in a warming climate; in the 2015 book “The Monsoons and Climate Change: Observations and Modeling,” Hirokazu Endo (MRI) and Akio Kitoh (University of Tsukuba, Japan) concluded: “State-of-the-art climate models project that both the amount and intensity of Asian summer monsoon rainfall are likely to increase under global warming, and that the rates of increase will be higher than those in other monsoon regions.”


Figure 6. A stadium in Wuhan, China on July 6, 2016, after the city received 7.09” (180 mm) of rain in the twelve hours ending at 8 am July 6. Wuhan received over 560 mm (1.8 feet) of rain over the ten day period before the July 6 deluge, causing widespread damage and chaos. (Photo by Wang He/Getty Images)


Figure 7. The 2016 Yangtze River floods in China would rank as the third most expensive weather-related natural disaster on record outside of the U.S., according to Aon Benfield and the international disaster database EM-DAT.


Figure 8. The U.S. has seen twelve weather-related disasters costing at least $20 billion, with eight of them more expensive than the 2016 Chinese floods. Data source: NOAA/NCEI.

Events 6 - 10: Hurricane Matthew, Tropical Cyclone Winston, Lousiana’s “No-Name” storm, Super Typhoon Meranti and Tropical Cyclone Fantala
The remainder of the top ten weather events of 2016 were all tropical cyclones. I discussed these five storms in a late-December post, Top Ten Tropical Cyclone Events of 2016 Potentially Influenced by Climate Change:

6) Hurricane Matthew in Haiti, The Bahamas, and the Southeast U.S.
7) Tropical Cyclone Winston: Earth's Strongest Southern Hemisphere Tropical Cyclone Ever Measured
8) Louisiana’s “No-Name” storm: the most damaging weather disaster of 2016 in the U.S.
9) Super Typhoon Meranti: Earth’s strongest landfalling tropical cyclone on record
10) Tropical Cyclone Fantala: strongest storm ever observed in the Indian Ocean

Other weather and climate of 2016 review articles
The Guardian: Climate change in 2016: the good, the bad, and the ugly
Climate Central: These Are the 10 Most Important Climate Stories of 2016
The Weather Channel: The Top 10 Weather Stories of 2016
Capital Weather Gang: Year of the flood: The nation’s 10 most extreme weather events of 2016

We'll have a new post on Friday.

Jeff Masters

Climate Summaries Air and Water Pollution

Updated: 4:55 PM GMT on March 06, 2017

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California's New Year Is Awash in Moisture--and There's Much More to Come

By: Bob Henson , 5:10 PM GMT on January 04, 2017

After five years dominated by a grinding, near-statewide drought, it’s a bit disorienting to find ourselves looking at a dramatically wet pattern enveloping much of California as 2017 gets under way. One major slug of heavy rain and mountain snow moved through the heart of the state from Tuesday into Wednesday. As of 4 am PST (12Z) Wednesday morning, central California had racked up some impressive 24-hour rainfall amounts, including widespread 3” - 5” amounts and a few 5” - 7” totals. In Monterey County, Anderson Peak was inundated with 7.25”. Large swaths of the mountainous West were under winter storm warnings on Wednesday, from northern California and southern Oregon to central Colorado, with 2 to 4 additional feet of snow possible above 7000-8000 feet in the Sierra (where an avalanche warning was in effect). Winter weather advisories for lighter snow have been hoisted along the storm’s projected track through Kansas City and St. Louis.

An even more intense round of heavy precipitation is on track to strike California this weekend, setting the stage for a potential major flood threat in some areas. Already, on Wednesday morning, a flash flood warning was posted for the California coast near Big Sur in the steep mountains where the Soberanes Fire burned last summer, and the Big Sur River was already at moderate stage.


Figure 1. Parts of the Sierra Nevada may rack up more than 20” in precipitation (including rain and the moisture within snow) over the seven-day period from 00Z January 4 to 11 (4:00 pm PST Jan. 3 to 10), based on this projection from the 0Z Wednesday run of the GFS model. Image credit: www.tropicaltidbits.com

Firehose of moisture for a thirsty state
Computer guidance, including multiple runs of the ECMWF and GFS models, are in strong agreement that a powerful, long-duration atmospheric river (AR) will set up across a southwest-to-northeast swath of California over the weekend, although there are differences on timing and location from run to run and model to model. See my post from last August for background on ARs, which deliver beneficial rains and snows to California and other areas but can also lead to rampaging floods. This weekend’s AR is projected to pull moisture from the midlatitudes and subtropics and channel it into a relatively narrow swath that will push directly into coastal mountains and on into the Sierra Nevada. The heaviest coastal rains this weekend will probably strike somewhere between Santa Barbara and the north CA coast, although it’s too soon to nail down the exact location of the AR, as noted on Tuesday evening by Daniel Swain (California Weather Blog).

“Since this system is expected to be slow moving, the associated atmospheric river may stall over some portion of northern or central California on Sunday or Monday--or even waver back northward temporarily,” Swain wrote. “If and when this occurs (as has been suggested by recent runs of both the ECMWF and GFS), there may be a 100-200 mile wide band of even higher precipitation totals. It’s impossible to say at this time where any stalling or frontal waves might occur, but that has the potential to be a serious situation locally.”

Some model runs have been generating mind-boggling amounts of snowfall in the Sierra over the next few days, on the order of 8 to 10 feet (and much more in some cases). There’s no question that enormous amounts of moisture are likely to fall over these mountains, and the very highest elevations will be slammed with massive amounts of snow. However, any model projection of snowfall needs to be taken with several grains of salt, as the actual on-the-ground snow totals will hinge on the precise location of the AR, how much moisture it hauls inland, and how much warmth accompanies that moisture. The lowest snow levels in the Sierra could jump from as low as 2000 feet on Friday to as high as 10,000 feet by Sunday, according to Swain.


Figure 2. Very large amounts of integrated water vapor (IVT) will be pushed by an atmospheric river into the heart of California on Sunday, January 8, based on calculations from the 00Z Wednesday GFS model run. IVT measures the amount of water vapor, in kilograms, carried per second in the air flowing above and across an imaginary meter-wide threshold that is oriented perpendicular to the atmospheric river. Arrow lengths denote the intensity of the moisture transport. Image credit: NOAA/ESRL Physical Sciences Division.


Figure 3. Jared Gaston, 25, hesitated before jumping flooded Fairview Street to meet a friend during rains on Thursday, Dec. 22, 2016, in Garden Grove, California. Image credit: Ken Steinhardt/The Orange County Register via AP.

A water year that’s already in the black moisture-wise (but not snow-wise)
The Pacific jet stream took aim at the U.S. West Coast for much of the autumn and early winter, which led to the wettest fall on record in Washington and one of the 20 wettest for both Oregon and California. Now the jet has shifted bodily into California, as is typical in midwinter, carrying rich slugs of deep Pacific moisture into the state. Compared to the paltry moisture totals racked up during most of this decade, California has already seen generous amounts for the 2016-17 water year, which began on October 1.



What hasn’t changed much since the multiyear drought began in 2011 is the year-to-year prevalence of milder-than-average temperatures over most of the state, including the Sierra Nevada. The extreme heat of recent years has intensified the impact of drought in concrete ways--by baking the already-dry landscape during midsummer, for example, and by eroding the Sierra’s winter snowpack prematurely. But unusual warmth can also torque the hydrologic system during wet periods, such as the water year now under way.


Figure 4. Frank Gehrke, chief of the California Cooperative Snow Surveys Program for the Department of Water Resources, crosses a snow-covered meadow as he conducts the first snow survey of the season at Phillips Station Tuesday, Jan. 3, 2017, near Echo Summit, CA. Although the scene looks wintry enough, the survey showed the snowpack was only at 53% of normal for this site at this time of year. Image credit: AP Photo/Rich Pedroncelli.


Figure 5. The amount of water held in snowpack across California’s three Sierra regions was only about a quarter of its way to the typical April 1 total as of January 3, 2016. Collectively, the three regions had about 70% of the amount of snow water content observed on a typical January 3. Image credit: California Department of Water Resources.

Through January 2, South Lake Tahoe had received 162% of its average precipitation for the water year to date (including rain and melted snow). However, as of January 3, the three Sierra regions held only about 70% of the typical amount of moisture found within snowpack (snow water equivalent) for the time of year, and only 53% of normal at the traditional measuring site of Phillips Station, as reported in the season’s first official monthly snow survey. This discrepancy is due to mild Pacific storms with high snow levels as well as to extensive melting in between storms, especially during a fairly dry November. While midwinter snowmelt does help replenish reservoirs and aquifers at lower elevation, it’s also important that a hefty amount of snow remain in the Sierra till at least early spring, in order to help protect the region’s ecosystems from early-summer heat and to sustain a healthy flow through rivers and creeks as far into the hot season as possible.

If the air in this weekend’s atmospheric river is as warm and moist as models suggest, the Sierra could end up with an even bigger gap between how much moisture falls and how much snowpack remains. Even so, water is water, and a series of big storms like this could make a major contribution to quenching California’s fierce multiyear drought. Let’s hope that residents and visitors take this weekend’s potential flood threat seriously--as weird as it is to be on guard against water’s power after craving moisture for so long.

Jeff Masters will be posting his roundup of the top ten weather and climate events of 2016 later today. I’ll be back on Friday with an update on the impending atmospheric river in California, as well as the potential for a significant weekend snowstorm across parts of the U.S. South.

Bob Henson





Flood Winter Weather

Updated: 5:03 PM GMT on March 06, 2017

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How to Save $23 Trillion Per Year: 100% Renewable Energy for the World

By: Jeff Masters , 4:02 PM GMT on January 02, 2017

Here’s a 2017 New Year’s resolution I’d like to see the nations of the world adopt: an immediate international effort to invest in a world where 100% of our electricity will be generated by wind, water, and solar power by 2050. Such an effort is technically and economically feasible, and has been championed by Stanford professor Mark Jacobson since 2009. His latest research on the subject was laid out in a series of talks last month in San Francisco at the annual meeting of The American Geophysical Union—the world’s largest conference on climate change. During his talks, Dr. Jacobson outlined a plan to power 139 nations of the world for all purposes—including electricity, transportation, heating/cooling, industry, and agriculture/forestry/fishing—using a mix of approximately 37% wind, 58% solar, 4% hydropower, and 1% geothermal, wave, and tidal power. He argued that his plan would:

1) Replace 80% of business-as-usual power by 2030, and 100% by 2050
2) Reduce power consumption by 42.5% because of electricity’s better work:energy ratio, efficiency, and lack of mining needed
3) Create 24.3 million more jobs than lost
4) Eliminate 3.5 million premature air pollution deaths per year and save $23 trillion (7.6% of GDP) in air pollution health costs per year by 2050 (for comparison: the World Bank estimated in 2016 that air pollution in 2013 killed 5.5 million people, with non-health care costs of over $5 trillion)
5) Save $28.5 trillion per year in avoided climate change costs by potentially keeping global warming less than 1.5°C above pre-industrial levels
6) Reduce war by creating energy-independent countries
7) Decentralize energy production, thereby reducing power outages, terrorism threats to energy installations, and energy poverty


Figure 1. Dr. Mark Jacobson of Stanford addresses an audience in San Francisco at the annual meeting of The American Geophysical Union on December 17, 2016.

OK, this New Year’s resolution does not come cheap. The up-front cost of such an energy system is $124.7 trillion for converting the 139 nations of the world Dr. Jacobson studied. However, it’s critical to consider the savings, not just the costs. He estimates that by 2050, an $85 per person per year savings in electricity costs will be realized using a 100% wind, water, and solar powered world compared to the current business-as-usual system. This does not include the savings due to reduced air pollution and reduced climate change costs, which would be an additional $5,800 per person per year.


Figure 2. The total surface area (in square kilometers) of the Earth including oceans (large blue circle) and land surface area of the 139 countries studied (pink circle) are compared to the areal footprint of the renewable energy systems (beyond what was installed as of 2015) needed to provide 100% of power by 2050 in Dr. Jacobson’s road map. The plan requires approximately 653,200 square km offshore wind turbines, 1,105,000 square km of onshore wind turbines, 87,410 square km of rooftop solar photovoltaic (PV) panels, and 260,500 square km of photovoltaic and concentrated solar power (CSP) systems run by utility companies. For hydropower, no new installations are proposed, so the additional footprint is zero. About 1% of the world’s land area would be needed for the power systems proposed. Image credit: Dr. Mark Jacobson, Stanford.

His road map to a 100% renewable energy future uses existing generator technologies, along with existing electrical transportation, heating/cooling, and industrial devices and appliances. Electricity storage is done using existing storage technologies—Concentrated Solar Power (CSP) with storage, pumped hydroelectric storage, and existing heat/cold storage technologies (water, ice, and rocks). No stationary storage batteries, biomass, nuclear power, carbon capture, or natural gas are required. No new dams would be needed, but existing dams would be made more efficient. Aircraft flying less than 600 km would be electric, and those flying longer distances would be powered by hydrogen fuel cells. He modeled the seasonal and daily variation in solar energy and wind power in the 139 countries, with storage, and was able to show that the power grid was stable—the load on the grid matched the electricity supply. The 2.5 million wind turbines required would cause approximately a 0.6% reduction in world’s average wind speed, which he argued should not cause major disturbances to the weather. Dr. Jacobson acknowledged that political obstacles would make his plan difficult to implement, but stressed that a solution to global warming is technically and economically feasible. A detailed discussion of his plan is here.

Jeff Masters

Climate Change

Updated: 4:56 PM GMT on March 06, 2017

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The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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