By:
Jeff Masters and Bob Henson
, 4:46PM,GMT on January 27,2015
Although the New York City metropolitan area was largely spared, the
Blizzard of 2015 is pulling no punches this morning across much of
eastern New England. Some locations in Massachusetts have already topped
two feet of snow, with heavy snowbands still pounding the Boston
metropolitan area and Cape Cod, extending northeast into coastal Maine.
Although the heaviest snow will exit New England later this afternoon,
lighter snow could persist into tonight in some areas.
According to the 10,EST Tuesday NWS Storm Summary and reports from the Boston NWS and New York City NWS, total snowfall amounts as of 9AM,EST Tuesday at some Northeast U.S. locations included:
26.0" Worcester, MA
20.9" Islip, NY
18.0" New Bedford, MA
14.8" Portland, ME
11.0" Providence, RI
11.0" NYC La Guardia Airport
8.6" NYC JFK Airport
7.8" NYC Central Park
4.5" East Hartford, CT
3.5" Bridgeport, CT
7.0" New Haven, CT
6.0" Newark, NJ
1.1" Washington DC
At 10:10AM,EST, an observer in Framingham, MA, reported 30.0”.
Top wind gusts:
78 mph, Nantucket Island, MA
78 mph, Mount Washington, NH
74 mph, Humarock, MA
70 mph, Sagamore on Cape Cod, MA
The highest sustained winds thus far have occurred at Nantucket Island: 59-mph at 6:09 am Tuesday.
Figure 1. Photo credit: A vehicle buried under a night’s worth of heavy snow in East Lyme, Connecticut. Photo credit: Wunderphotographer Xchange.
The Massachusetts coastline experienced high waves, moderate coastal flooding, and a few areas of major coastal flooding this morning. According to the Boston Globe, Scituate, located southeast of Boston, reported “rapidly deteriorating conditions’’ after the predawn high tide, with residents along Central Avenue and Surfside Road calling for help to evacuate their flooded homes. Preliminary data from the NOAA Tides and Currents website shows that the storm surge in Boston Harbor (the amount delivered by the storm above normal high and low tides) was exceeding 4.5 feet as of 11:00 am EST--considerably higher than expected. This surge is higher than the maximum storm surge observed in the blizzard of February 1978, but slightly less than the 5 feet observed in the “Perfect Storm” of Halloween 1991. Fortunately, the maximum surge occurred as the tide was going out; during the 4:30 am Tuesday high tide, the surge was lower, about 3.2 feet.
Figure 2. Infrared satellite images of the “Storm of the Century” (March 13, 1993) and the Blizzard of 2015 (January 27, 2015). Image credit: CIMMS Satellite Blog (left), WunderMap (right).
Why was the snowfall forecast for New York City too high?
On Monday morning, the National Weather Service predicted storm-total snowfall amounts of 20 - 30" for New York City. As of 9 am EST Tuesday, snowfall amounts in the city ranged from 7.8" in Central Park to 11" at La Guardia Airport, with just 1 - 2" more snow likely. So what went wrong with the forecast? Heavy snow forecasts are notoriously difficult, since our computer models struggle to accurately predict where the very narrow bands of heavy snow with snowfall rates of 2 - 4" per hour will set up. Furthermore, an error of 50 miles in predicting the track of the storm can make a huge difference in snowfall amounts, and a 50-mile error in track in a 24-hour forecast is fairly common for a storm system 1000 miles across. The 7 am EST (12 UTC) Monday run of what is usually our top forecast model, the European model, predicted that the storm would track about 100 miles farther west than it actually did. The American GFS model, which just underwent a significant upgrade over the past month to give it increased horizontal resolution, performed better, putting the storm farther to the east. Forecasts that relied too heavily on the European model put too much snow over New York City. The heaviest snows were about 50 miles east of the city, over central Long Island (Islip Airport, located 50 miles east of New York City, got 20.9" of snow as of 9 am EST Tuesday.) Moral of the story: the European model, which famously out-predicted the GFS model during Hurricane Sandy, is not always right. The GFS model is also a top-notch model, and will sometimes outperform the European model. The Weather Channel forecasts relied less heavily on the European model, and predicted 15" of snow for NYC early on Sunday. The forecast snow amounts were cut to less than 10" by Sunday evening, and stayed that way for the duration of the storm.
Figure 3. Surface pressure (blue contours) and precipitation (color-fill) forecast for 7 am Tuesday January 27, 2015, as predicted by the 7 am EST (12 UTC) Monday January 26 run of the European model. The model's predicted center location of the blizzard (marked with an "L") was about 100 miles farther west than the what actually occurred. Image taken from our wundermap with the model maps layer turned on.
As recently as Monday morning, the Short-Range Ensemble Forecast system suggested a wide range of possibilities for total snowfall in the New York area (considerably wider than for Boston, where models were in closer agreement on a big storm). Forecasters are increasingly looking to probabilistic tools as a way to convey the uncertainty inherent in multiple model solutions. As we noted yesterday, the NWS Boston office released maps showing the lowest and highest 10% of accumulations that might be expected based on a range of model guidance. Such maps remain experimental, and it is not yet clear what formats will be most useful to the wide range of public and specialized users of NWS forecasts. The recent growth in collaboration among social scientists and meteorologists could shed light on the best routes forward as probabilistic guidance grows in complexity (and potential usefulness). For more on the probabilistic aspects of the Blizzard of 2015, see Lee Grenci’s Wunderground post “Misleading Snowfall Forecasts.” We will continue to update our live blog on the storm through the day.
Figure 4. Cumulative snowfall predictions for New York (LaGuardia Airport) from the Short-Range Ensemble Forecast system issued at 5 pm EST (21 UTC) Monday, January 26. The SREF ensemble is drawn from several independent runs using the NAM, WRF-NMM, and WRF-ARW models. A split between model clusters is evident in the large spread of projected accumulations, with predicted snowfall amounts ranging from 4" to 40". Image credit: NOAA Storm Prediction Center.
Bob Henson and Jeff Masters
According to the 10,EST Tuesday NWS Storm Summary and reports from the Boston NWS and New York City NWS, total snowfall amounts as of 9AM,EST Tuesday at some Northeast U.S. locations included:
26.0" Worcester, MA
20.9" Islip, NY
18.0" New Bedford, MA
14.8" Portland, ME
11.0" Providence, RI
11.0" NYC La Guardia Airport
8.6" NYC JFK Airport
7.8" NYC Central Park
4.5" East Hartford, CT
3.5" Bridgeport, CT
7.0" New Haven, CT
6.0" Newark, NJ
1.1" Washington DC
At 10:10AM,EST, an observer in Framingham, MA, reported 30.0”.
Top wind gusts:
78 mph, Nantucket Island, MA
78 mph, Mount Washington, NH
74 mph, Humarock, MA
70 mph, Sagamore on Cape Cod, MA
The highest sustained winds thus far have occurred at Nantucket Island: 59-mph at 6:09 am Tuesday.
Figure 1. Photo credit: A vehicle buried under a night’s worth of heavy snow in East Lyme, Connecticut. Photo credit: Wunderphotographer Xchange.
The Massachusetts coastline experienced high waves, moderate coastal flooding, and a few areas of major coastal flooding this morning. According to the Boston Globe, Scituate, located southeast of Boston, reported “rapidly deteriorating conditions’’ after the predawn high tide, with residents along Central Avenue and Surfside Road calling for help to evacuate their flooded homes. Preliminary data from the NOAA Tides and Currents website shows that the storm surge in Boston Harbor (the amount delivered by the storm above normal high and low tides) was exceeding 4.5 feet as of 11:00 am EST--considerably higher than expected. This surge is higher than the maximum storm surge observed in the blizzard of February 1978, but slightly less than the 5 feet observed in the “Perfect Storm” of Halloween 1991. Fortunately, the maximum surge occurred as the tide was going out; during the 4:30 am Tuesday high tide, the surge was lower, about 3.2 feet.
Figure 2. Infrared satellite images of the “Storm of the Century” (March 13, 1993) and the Blizzard of 2015 (January 27, 2015). Image credit: CIMMS Satellite Blog (left), WunderMap (right).
Why was the snowfall forecast for New York City too high?
On Monday morning, the National Weather Service predicted storm-total snowfall amounts of 20 - 30" for New York City. As of 9 am EST Tuesday, snowfall amounts in the city ranged from 7.8" in Central Park to 11" at La Guardia Airport, with just 1 - 2" more snow likely. So what went wrong with the forecast? Heavy snow forecasts are notoriously difficult, since our computer models struggle to accurately predict where the very narrow bands of heavy snow with snowfall rates of 2 - 4" per hour will set up. Furthermore, an error of 50 miles in predicting the track of the storm can make a huge difference in snowfall amounts, and a 50-mile error in track in a 24-hour forecast is fairly common for a storm system 1000 miles across. The 7 am EST (12 UTC) Monday run of what is usually our top forecast model, the European model, predicted that the storm would track about 100 miles farther west than it actually did. The American GFS model, which just underwent a significant upgrade over the past month to give it increased horizontal resolution, performed better, putting the storm farther to the east. Forecasts that relied too heavily on the European model put too much snow over New York City. The heaviest snows were about 50 miles east of the city, over central Long Island (Islip Airport, located 50 miles east of New York City, got 20.9" of snow as of 9 am EST Tuesday.) Moral of the story: the European model, which famously out-predicted the GFS model during Hurricane Sandy, is not always right. The GFS model is also a top-notch model, and will sometimes outperform the European model. The Weather Channel forecasts relied less heavily on the European model, and predicted 15" of snow for NYC early on Sunday. The forecast snow amounts were cut to less than 10" by Sunday evening, and stayed that way for the duration of the storm.
Figure 3. Surface pressure (blue contours) and precipitation (color-fill) forecast for 7 am Tuesday January 27, 2015, as predicted by the 7 am EST (12 UTC) Monday January 26 run of the European model. The model's predicted center location of the blizzard (marked with an "L") was about 100 miles farther west than the what actually occurred. Image taken from our wundermap with the model maps layer turned on.
As recently as Monday morning, the Short-Range Ensemble Forecast system suggested a wide range of possibilities for total snowfall in the New York area (considerably wider than for Boston, where models were in closer agreement on a big storm). Forecasters are increasingly looking to probabilistic tools as a way to convey the uncertainty inherent in multiple model solutions. As we noted yesterday, the NWS Boston office released maps showing the lowest and highest 10% of accumulations that might be expected based on a range of model guidance. Such maps remain experimental, and it is not yet clear what formats will be most useful to the wide range of public and specialized users of NWS forecasts. The recent growth in collaboration among social scientists and meteorologists could shed light on the best routes forward as probabilistic guidance grows in complexity (and potential usefulness). For more on the probabilistic aspects of the Blizzard of 2015, see Lee Grenci’s Wunderground post “Misleading Snowfall Forecasts.” We will continue to update our live blog on the storm through the day.
Figure 4. Cumulative snowfall predictions for New York (LaGuardia Airport) from the Short-Range Ensemble Forecast system issued at 5 pm EST (21 UTC) Monday, January 26. The SREF ensemble is drawn from several independent runs using the NAM, WRF-NMM, and WRF-ARW models. A split between model clusters is evident in the large spread of projected accumulations, with predicted snowfall amounts ranging from 4" to 40". Image credit: NOAA Storm Prediction Center.
Bob Henson and Jeff Masters
whoa! open my back door and saw this! (Weathernanny)
snow gremlin gives good sense of accumulation in Boston (Weathernanny)
E 83rd snow love (victoid)
MORE SMITHTOWN, NEW YORK. LONG ISLAND. (joealaska)
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