The Post Christmas Day Blizzard of 26-27 December 2010

 

A major Nor’easter brought significant snows and blizzard conditions to much of the northeastern US from Sunday to Monday 26-27 DEC 2010. Low pressure developed along the Gulf Coast on Christmas. Once the low reached the southeast coast Christmas night it intensified and strengthened and headed northeastward along the East Coast. Explosive cyclogenesis occurred Sunday night, as the low move northward toward Long Island with the low passing near Cape Cod early Monday morning. The low then proceeded up the New England coast during the day. Bands of heavy snow with snowfall rates of 1 to 3 inches an hour occurred across the region. Snow totals of 1 to 2 feet occurred mainly east of the Hudson River and across adjacent western New England. Snowfall totals decreased dramatically north and west of the Capital Region. Strong and gusty winds caused significant blowing and drifting of the snow. Winds gusts across the local area were 35 to 45 mph with gusts of 50 to 70 mph reported across southeastern NY, CT, RI, and eastern MA. Here is a timeline on the storm on what occurred with headlines:

 

The medium range guidance had this storm roughly a week in advance, and then it disappeared for a few days. The HWO had the storm in it in Days 5-7, and then the majority of the guidance shifted it out to sea with little or no impact on the County Warning Area. There was a lot of discussion on the strength of the ECMWF with medium range systems in the extended portion of the forecast, but it did not have a favorable track for the forecast area getting warning level snowfall until about 48-60 hrs in advance. The ECMWF did have a major storm in days 6 and 7…and then it disappeared. The GFS/Ensembles did a better job with the storm track and evolution 60-84 hours in advance. The Canadian GGEM struggled with the system. HPC struggled to deviate from the ECMWF for the system. Various forecasters continually discounted the GFS…even after 3 consecutive model runs at 1200 UTC and 1800 UTC 24 DEC…and 0000 UTC 25 DEC.

 

Some of the uncertainty can be illustrated by an incident where forecasters at area NWS offices and at HPC communicated different interpretations of deterministic model guidance and ensemble guidance.  The GFS and its Ensemble mean indicated a solution further offshore, and due to run-to-run consistency this was favored by HPC.  Although area NWS offices saw some signals for trends of a more coastal storm track, there was still considerable uncertainty, so there was no justification for changing the forecast at that time.  The official forecasted storm track remained offshore until the 0000 UTC 26 December ECMWF and CAN GGEM were in line with the storm track and evolution. The official forecasted storm track was changed to indicate coastal northeastern impact once this new guidance arrived.   The bottom lines with this lessoned learned is to go with the way the new trends are leading…and we must put out the best forecast as possible based on the trends and the majority of the guidance. We can not stick with “favorites”. Sometimes the best performing models have problems. This is not a new trend over the past few decades. The guidance with memorable storms such as the 29-30 DEC 2000 and the Surprise Snowstorm of late January 2000 was inconsistent at times.  There has been some discussion within the NWS and academia regarding this post Christmas Day 2010 snowstorm, that reconnaissance aircraft was not able to deploy dropsondes over data sparse regions of the Pacific at routine intervals, so critical upstream data was missing when the forecast models were initiated, resulting in forecast errors.  This will continue to be investigated.

 

25 DEC 2010…0900 UTC….A watch was put out for the Berkshires and locations south of the Capital Region. The AFD discussed if the trends persisted in the 0600 and 1200 UTC model guidance that more zones would likely be added to watch. More coordination with surrounding NWS offices stated that SREF probabilistic snow graphics supported less snow in their area of the Catskills so they were reluctant to be aggressive about headlines in their portion of the Catskills. We told neighboring offices we did not want to leave the Catskills out of the Watch since we thought higher snow ratios of 15:1 or so would be common…and we had no idea how well the SREF snow graphics verified. Bottom line…go with your reasoning and try your best to communicate with surrounding offices.

 

Discussion began of possible blizzard conditions on the midnight shift of 26 DEC. The initial watch was changed to a warning…and the watch was expanded northward to include the Capital region…Mohawk Valley…most of the Lake George Region…and Southern Vermont. The Albany Office collaborated with neighboring offices about a potential upgrade to a Blizzard Warning for NW CTDutchess…and Berkshire counties. There were some differences in opinion between surrounding offices. We were on the fence…and couldn’t really do it in CT without full collaboration from surrounding offices. The best approach was to wait another shift to get a better look at it. The warning was expanded northward to include the Northern Catskills…southern VT…the Greater Capital Region…and the Schoharie Valley. Advisories were issued for all other locations except the southern Adirondacks. Later collaboration with surrounding offices resulted in including Litchfield and Dutchess counties in a Blizzard Warning later that day.

 

This was an extremely complex and historic snowstorm/blizzard that will be studied for years to come in terms of the predictability issues and the societal impacts. This snowstorm was rated a Category 3 on the Northeast Snowfall Impact Scale. The lowest measured pressure associated with the Miller Type A snowstorm was 963.8 hPa measured at KACK at 1153 UTC 27 DEC 2010.

 

KACK 271153Z 36027G36KT 5SM RA BR OVC012 03/01 A2846 RMK AO2 PK WND 01037/1139 SLP638 P0013 60023 70101 T00280011 10067 20022 56079

 

Guidance and ensembles

 

ECMWF ensembles

 

 

Above:  Loops of consecutive 00Z ECMWF ensemble mean (left), and operational (right) runs of MSLP.

 

 

Above:  Loops of consecutive 12Z ECMWF ensemble mean (left), and operational (right) runs of MSLP.

 

 

 

Above:  00Z 25 December ECMWF 500 hPa ensemble mean (left) and operational (right) heights and anomalies valid 00Z 27 December.

 

 

Above:  00Z 25 December ECMWF 500 hPa ensemble mean (left) and operational (right) heights and anomalies valid 00Z 28 December.

 

 

Above:  12Z 25 December ECMWF 500 hPa ensemble mean (left) and operational (right) heights and anomalies valid 12Z 27 December.

 

 

 

Above:  12Z 25 December ECMWF 500 hPa ensemble mean (left) and operational (right) heights and anomalies valid 12Z 28 December.

 

 

Above:  00Z 26 December ECMWF 500 hPa ensemble mean (left) and operational (right) heights and anomalies valid 00Z 28 December.

 

 

Above:  12Z 26 December ECMWF 500 hPa ensemble mean (left) and operational (right) heights and anomalies valid 12Z 27 December.

 

GEFS Ensembles

Above:  Loops of consecutive GEFS MSLP spaghetti plots, mean and anomalies valid 00Z 27 December (left) and 12Z December (right).

 

 

Above:  Loops of consecutive GEFS 500 hPa spaghetti plots, mean and anomalies valid 00Z 27 December (left) and 12Z December (right).

 

 

 

Above:  Loop of consecutive GEFS 850 winds and anomalies valid 00Z 27 December. 

 

 

 

 

Above:  Loops of consecutive GEFS 850 hPa (left) and 700 hPa (right) temperature spaghetti plots, means and anomalies valid 00Z 27 December.

 

 

Above:  Loop of GEFS probabilities for 0.05” liquid equivalent valid 00Z 27 December.

 

Above:  Loop of consecutive SREF MSLP spaghetti plots, mean and anomalies valid 12Z 27 December.

 

 

Above:  Loop of consecutive SREF 850 winds and anomalies valid 00Z 27 December.  

 

 

Above:  Loop of SREF probabilities for 1.00” liquid equivalent valid 12Z 27 December.

 

 

 

 

Above:  GEFS loop of plumes from Albany, NY (left, and SREF plumes from Albany, NY (center left), Islip, NY (center right) and Bradley, CT (right).

 

 

Above:  Comparison of liquid equivalent QPF from the GFS (upper left), NAM (upper right), ECMWF (lower left) and GEM (lower right).

 

 

Above:  Comparison of liquid equivalent QPF from the next run of the GFS (upper left), NAM (upper right), ECMWF (lower left) and GEM (lower right).

 

  

 

Above:  NCEP HPC hazardous threats issued 24 December (left), and HPC winter weather desk forecast issued at 0708Z 25 December.

 

   

 

Above:  NCEP HPC winter weather desk forecasts issued at 0815Z 25 December (left), 1723Z 25 December (left center), 0628Z 26 December (right center), and 1819Z 26 December (right).

 

  

 

Above:  Graphic of winter weather headlines, with Advisories in blue, Warnings in pink, and Blizzard in red, valid times on top of graphics.

 

    

 

Above:  Loops of heights, winds and temperatures for 300 hPa (left), 500 hPa (left center), 700 hPa (center), 850 hPa (right center), and 925 hPa (right).

 

 

 

Above:  MSLP loops from MSAS (left) and NCEP HPC (right).

 

 

Above:  KENX radar loop of the intense snow band in western New England, southern and eastern NY.

 

 

Above:  Regional radar loop of the evolution of the storm.

 

 

Above:  The preliminary ranking of the storm on the NESIS scale is 3, which is major.