Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 1:41 PM GMT on November 07, 2012
A deepening low pressure off the eastern seaboard with create nor'easter-like conditions across the Northeast over the next 36 hours. Heavy snow inland with rain and gusty winds along the coast will affect many areas greatly impacted from Hurricane Sandy condinuing to dampen clean-up efforts. Power outages with winds in excess of 50mph sustained can be expected within 20mi of the coast. Further inland across the higher elevations, up to a foot of snow is possible. Stay tuned for this major weather event!
Current Surface Plot...
(Courtesy of HPC)
November 7-8 Nor'easter Timeline and Discussion...
A deepening low pressure center off of the New Jersey coast will continue undergoing impressive cyclogenesis throughout the next 24 hours as surface pressures fall to sub 996mb. As the trough becomes negatively tilted intensification will further in association with an expanding wind and precipitation shield.
A 1032mb anticyclone over Newfoundland will tighten the pressure gradient increasing winds during the day on Wednesday particularly along the coast. Winds aloft a few thousand feet are gusting above 60 knots, and as precipitation rates increase mixing will pull these gusts down to the surface. High wind warning criteria winds are likely from southern New Jersey up through coastal Massachusetts where sustained winds will approach 50mph and an occasional gust to 65mph is expected. Already current metar reports out of Atlantic City show winds gusting to 60mph. Farther inland a more defined stable layer will limit winds to sustained around 20mph, so power outages and tree damage is not expected.
Current storm surge prognostics are indicating a water rise of 1-4 feet from New Jersey to Connecticut. A northeasterly component to the wind will allow water to pull along the favored inlets and bays including once again the Long Island Sound. The high tide of greatest concern is the Thursday morning one where water levels may approach moderate flooding in some areas. Beach erosion is expected. Overall general conditions along the shoreline can be anticipated with a moderate to severe nor'easter. Areas along the Delaware and Chesapeake Bays will generally be spared. I am especially concerned for areas along the coast in Connecticut and New York where clean up is just beginning and will greatly be affected by flooding during the Thursday morning high tide.
Rainfall and associated flooding is not a threat for any locations in the Northeast. Total QPF is only expected to max out around 1.5 inches across southern England. Given current flash flood guidance, no threats are expected.
The 500mb setup is very reminscent of a mid winter nor'easter with banana high system to the north, negative NAO, and rapidly deeping low pressure along the immediate coastline. As the precipitation shield expands inland, a stagnant but dense cooler air mass will allow for the threat of significant snow accumulations in some areas. While it is early November, the sun is not a factor and actually equivalent to an early February sun angle. Looking at the areas under the highest vertical velocity rates and omega growth, dynamic cooling will allow areas even hovering around 33-35F to change to a wet snow. For the time being the combination of best vertical lift and highest QPF will be focused across the Pennsylvania Poconos up through northwestern New Jersey. Ice crystal growth will begin to increase as the column begins to cool below -7C allowing for a period of excellent dendritic growth. Snow ratios may actually approach 15:1 for these areas. Impressive CCB banding will allow for a short period (2-3 hours) of snow rates up to 2in/hr. Snow accumulations will exceed 10in across a few locations in this area especially above 1300ft. Another area of snow concern will be across southeastern Pennsylvania including the Philadelphia metro where latest guidance suggests an impressive mesoscale banding setup that may allow areas to see moderate accumulations of snow in the range of 3-6in. Towards New England mesocale banding features will setup across the Berkshires and parts of northern Connecticut where it is possible for a period of very heavy snow with total accumulations of 5-10in over the higher elevations. Elsewhere most valley locations will see 1-4in generally over grassy surfaces and colder surfaces.
There is still a question as to how far west the precipitation shield expands and therefore the extension of any snow accumulation. For the time being I like my snow map as to a general outline of the precipitation shield. Areas farther west will have a harder time seeing accumulations despite being closer to the heart of the cold air mass as precipitation rates will be lower in association with poor ice crystal growth.
Overall the impacts of this nor'easter will be greatly felt up and down the Middle Atlantic and New England regions. It does appear the low does not linger too long and pulls out of the area by Thursday. Warmer air will also move in by the weekend allowing any snow to melt within 48 hours.
8am-11am Thursday- Precipitation will begin to expand west as the low pressure becomes better organized. A tight pressure gradient already in place will allow coastal areas to see gusts in excess of 55mph from Cape Cod south to Ocean City, MD. Dry air entrenched over the Middle Atlantic will allow for substantial virga with rain/snow not making it north of the Delmarva.
11am-3pm- The precipitation shield will rapidly expand as the low begins to undergo its most rapid strengthening. High precipitation rates will overcome the low dew points and dry air expanding precipitation to as far west as the I-81 corridor. Given the low wetbulb temperatures precipitation will start as a mix of rain/snow/sleet despite surface temperatures in the upper 30s to even near 40F. Before precipitation rates increase further, it may even change over to all rain before the snow especially for parts of New Jersey and southeastern Pennsylvania.
3pm-8pm- The nor'easter event will be completely underway as precipitation spreads north to NYC and rain changes over to snow across the inland areas of the Middle Atlantic. Snow rates may exceed 1in/hr over eastern Pennsylvania in this period and will accumulate especially after sunset. Winds will be gusting to high wind warning criteria force from Delaware to Maine.
8pm-12am- This period will feature the heaviest snow over the Middle Atlantic while rain falls along the coast. Total QPF alone over eastern Pennsylvania and all of New Jersey in these four hours may exceed 0.5 inches. Dynamic cooling may allow for some snow even in unexpected areas where temperatures are more moderate. High winds and waves up to 15 feet will lash against the Atlantic coast.
12am-6am- The surface low will finally begin to pull northeast spreading the greatest effects towards New England with heavy snow falling over inland areas while severe nor'easter-type impacts are felt along the immediate coast. Precipitation will begin to end over the Middle Atlantic. High tide will be approach during the end of this time period with moderate coastal flooding expected.
6am-10am- Precipitation rates will begin to lighten over the entire Northeast as conditions begin to improve. Nevertheless lingering effects will be felt much of the day.
(Courtesy of Intellicast)
(Courtesy of NOAA)
This is my current rain/snow line...
Baltimore, MD - Dover, DE - Vineland, NJ - Jackson, NJ - White Plains, NY - Danbury, CT - Hartford, CT - Worcestor, MA - Portland, ME
***Areas north of this line will have the greatest threat of snow accumulation in excess of two inches. Many areas will see a mix of precipitation given the lack of an arctic air mass source and the time of year. Also a warm northeasterly flow off the Atlantic will keep most coastal areas predominately rain. Nevertheless snow accumulations this early in the year will cause many problems even in areas that receive a rain and snow mix.
1. Strong winds along the coast exceeding 50-60mph expected from New Jersey to New England.
2. Storm surge estimates will allow water to rise an additional 1-4 ft especially along the Long Island Sound.
3. Heavy snow rates briefly expected inland to exceed 1in/hr.
4. Quick movement of storm will allow effects to last less than 24 hours.
5. Conditions will greatly hamper clean-up efforts across the Middle Atlantic.
***The highest elevations of the Poconos and Berkshires will receive the heaviest snowfall. Accumulations may exceed 10 inches in this region especially in the region located around Mt. Pocono where brief snow rates may exceed 2in/hr. Light accumulations and more mixed precipitation is expected to the coast, but a slushy 1-2in cannot be ruled out.
Current Great Lakes Water Temperatures...
(Courtesy of NOAA)
Selected City Accumulations for the Northeast...
Hagerstown, MD- Up to 1in of wet snow expected
Baltimore, MD- 1-2in of wet snow possible
Salisbury, MD- Mix of rain/snow/sleet. Snow accumulations up to 1in
Pittsburgh, PA- Mostly cloudy skies
State College PA- A few light snow showers
Williamsport, PA- A few light snow showers
Altoona, PA- A few light snow showers
Harrisburg, PA- Short period of moderate snow; accumulations 1-3in
Lancaster, PA- Period of moderate to heavy snow; accumulations 2-5in
Philadelphia, PA- Rain changing to heav snow with accumulations of 3-5in
Allentown, PA- Moderate snow expected with accumulations around 2-5in
Scranton, PA- Period of light to moderate snow; accumulations up to 2in
Washington, DC- Light rain/snow mix; Up to 1in of snow is possible
Wilmington, DE- Rain changing to heavy snow; accumulations 3-7in
Dover, DE- Rain/snow mix; snow accumulations 1-3in are possible
Trenton, NJ- Rain changing to heavy snow; accumulations 2-4in
New York City, NY- Rain briefly mixing with snow; snow accumulations up to 1in
Poughkeepsie, NY- Brief period of moderate to heavy snow; accumulations 2-5in
Binghamton, NY- Flurries
Ithaca, NY- Cloudy
Albany, NY- Light rain/snow mix; snow accumulations up to 1in
Hartford, CT- Snow changing to rain/snow; accumulations 1-4in
Concord, NH- Rain/snow mix; snow accumulations of 2-4in
Providence, RI- Rain occasionally mixing with snow; accumulations of 1-3in are possible
Worcester, MA- Brief period of moderate to heavy snow; accumulations of 2-6in can be expected
Boston, MA- Rain mixing occasionally with snow; snow accumulations up to 2in possible
Nantucket, MA- Heavy rain and high wind gusts upwards of 65mph
Hyannis, MA- Heavy rain and high wind gusts upwards of 60mph
Burlington, VT- A few flurries
Portland, ME- Light to moderate snow; snow accumulations 1-4in
Bangor, ME- Moderate snow; snow accumulations 3-6in
"Subject to Change"
Current Northeast Snow Depth and Northeast Wind chills...
(Courtesy of Wunderground)
I think it will be important to focus on mesocale and high resolution models throughout the next 24 hours to look at where the mesoscale and CCB bands will set up. These areas will get some of the higher winds to mix to the surface along with the heaviest snow where I cannot rule out up to 3in per hour. The latest 4km HIRES WRF notes an impressive UVV and omega bursts over portions of southeastern Pennsylvania up through northwestern New Jersey. I really think some of the areas in this region will see upwards of 8-14in of snow. Overall model guidance is in a fairly decent correspondance although the exact track is still a bit uncertain. This will throw into question how far west the precipitation shield reaches. The SREF mean is probably the way to go for this event and allows the .1in contour as far west as 25mi past the I-81 corridor which looks fairly reasonable. The only thing the models may not be grasping in this aspect is the amount of dry air present over the area. Dew points are in the low 20s for many areas this Wednesday morning. Overall the ECWMF scores highest on the verification charts for spotting this threat, but was certainly overamplified therefore pulling a track too far to the west. The GFS did a fairly nice job, and throwing out is progressive nature bias, I will be interested in seeing the actual accuracy charts from the NCEP. The HRRR simulated radar already has a fairly good hold on this system; keep in mind as we advance in time that the composite radar often pulls precipitation too far to the west. I will be posting near term model updates throughout the day.
After the Storm
The latest NAEFS prognostics in association with changes in selection teleconnections are signaling a pattern change for the next coming two weeks. The NAO will begin to tip towards the positive scale again deamplifying the polar jet into a more progressive and zonal flow. This is also in correspondance with a -PNA forming across the Pacific. Latest monsoonal maps out of the Indian Ocean indicate the MJO rotating through phases the support ridging across eastern North America particularly in the southeastern United States. Meanwhile very cold air will begin to drop down across the Rockies and inner mountain west in association with a steep trough that will leave plenty of snow in the higher elevations. This will be good news for water tables after an ongoing mult-year drought.
The milder temperatures and drier air will flood the east coast in the rough estimate period of November 11-20. Latest long range prognostics report the MJO coming around to phases 7,8,1 by Thanksgiving along with a return to a -NAO. This may signal another cooler air mass towards the end of the month. Unlike the current nor'easter that was spotted nearly two to three weeks in advance, there are no signs of any long range major winter storm at this point.
In general I expect November to average slightly above normal given means around +4 compared to normal are likely during this two week warm spell. My next blog, since the weather finally begins to quiet, will be my winter forecast for the meteorological winter for 2012-2013. While it has been delayed later than normal this year, that has helped solidify a slightly higher confidence forecast. This blog can be expected within the next seven days. Stay tuned!
Please post storm reports in this blog from across the Northeast during the winter storm and please post location of observation in each report...
This blog is in progress. Check back soon...
Follow my 24hr forecasts on Twitter... Link and Facebook... Link.
Lower Susquehanna Valley Doppler...
(Courtesy of WGAL)
"10mi northeast of Harrisburg 2012-2013 winter statistics"
Monthly Total (October)- 0.0in
Monthly Total (November)- 0.0in
Seasonal Total- 0.0in
Winter Weather Advisories- 0
Winter Storm Warnings- 0
Ice Storm Warnings- 0
Blizzard Warnings- 0
Freezing Rain Advisories- 0
Winter Storm Watches- 0
Lowest High Temperature- ---
Lowest Low Temperature- ---
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Snow Storms Stats)
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.