Final Blizzard Of 2010 Summary

Last night into this morning, the NYC area was affected by one of its worst blizzards in recorded history. Heavy snow fell at rates of over 2-3 inches per hour, wind gust exceeded 50 mph and even peaked 68 mph in New London, CT and Bayville, NY, and snowfall amounts exceeded 20 inches in most of the immediate NYC area. What was almost as amazing as the storm itself, however, was the surprise as it came, as 2 days before the storm there were very little signs on the models that the storm would be anything even close to being what it was.

Forecasting The Storm:

Up to the day before the storm, it was very difficult to make a forecast for this storm, as the models had two separate solutions with no real consensus. The storm started showing up on the GFS model as a notable snowstorm for the area on Christmas day on December 17, which I did a section in that day's update focusing on the storm potential, and from the following day, a split in the model solutions began that lasted until a few days before the storm, with some models following an out to sea solution, bringing barely some snow to eastern Long Island and Cape Cod, while other models took the storm up the coast, bringing heavy snow to the area. At that time, there was evidence to support both solutions, but despite the majority of the models keeping the storm out to sea, the reliable ECMWF model was showing the blizzard solution consistently, being why I decided to go with a solution close to the ECMWF, showing the big snowstorm potential areas from Long Island into southern New England.

On Wednesday the 22nd, the storm's energy moved inland into the western United States, producing another round of heavy rain and snow to California, which was already hit with heavy rain and snow prior to this storm. Usually, once the storm's energy moves inland, it can be sampled better, and the models start to reach a consensus that usually lasts until the storm arrives. That consensus, however, was an out to sea solution, and even the ECMWF model that was consistent with a blizzard for the area having trended well to the east. The pattern up to that point supported an out to sea solution, and since this was in the short range, when the models typically start to reach a consensus, I also followed along with this trend. The models, however, still had some trouble handling the storm, which was the reason why I did not remove snow chances from the forecast in case it would trend west.

Between Friday afternoon and Saturday afternoon, however, a very unusual short range trend took place that put the area back in the big snowstorm potential. Up to that point, there was uncertainty whether the storm would move up the coast and intensify, or whether it would stay weak and well east of the area. On Friday afternoon, 2 days before the storm, a run of the GFS model came in that suddenly showed the storm moving up the coast, bringing a blizzard to the area. While this run was originally discarded due to apparent initialization errors, the 00z run of the NAM, which uses new data, also showed a much further west solution, the GFS trended even more west, and the UKMET also trended west. Such a big trend is very rare in the 48 hour range, which is when models would usually be consistent with the final solution. This last minute trend was mentioned as a possibility in the discussion on Friday, and became reality on Saturday when every model finally showed a big snowstorm, less than 36 hours before the storm started.

Storm Summary:

**The radar image below is from the peak of the storm, taken around 8:28 PM.**

The storm first affected parts of the Southeast into the Carolinas and Virginia on Saturday, bringing a rare white Christmas to these areas, however the storm did not start moving up the coast until Sunday morning, when it was off the coast of North Carolina and only starting to rapidly intensify. Snow started spreading into the area between 10-11 AM, and with temperatures only in the 20s, was able to start accumulating from the start. By 12 PM, a steady moderate snow was already falling in the central and eastern parts of the area with light accumulations up to at least an inch, and winds started to increase a little, but the worst was still to come.

By 2 PM, heavy snow bands already set up in central NJ and were starting to move into New York City and Connecticut. Winds were steadily increasing across the area with decreasing visibility, and the snow continued to become heavier in the western and central parts of the area. Around 4 PM, eastern Long Island was already starting to mix with sleet as precipitation became much lighter and a dry slot moved in, meanwhile the snow band that affected NYC was starting to set itself up in northeastern New Jersey, where it would stall for the rest of the evening and produce the heaviest snow amounts.

The worst of the storm started around 5 PM, when snow amounts were still light, only between 2 and 5 inches across most of the area. The heavy snow band set itself up in NE NJ, and wind gusts were already starting to increase, frequently gusting over 50 mph, and with temperatures only in the upper 10s to lower 20s away from the coast, wind chills were well into the single digits. The heavy snow and blowing snow created whiteout conditions, with near zero visibility for several hours, and snow rates were near 2 to 3 inches per hour. Thundersnow was even observed in the immediate NYC area. The eastern parts of the area started seeing heavy snow again as heavy snow bands moved in from the ocean, while the western parts of the area, being west of the heavy snow band, saw a steady moderate to locally heavy snow.

By the overnight hours, after 11 PM, the snow bands started weakening as the storm briefly stalled close to Long Island. As the worst of the storm moved into New England, the snow started weakening across the area, ending by the morning hours on Monday.


Storm's Aftermath:

**The map below shows estimated snowfall from the storm, which may be off in some places.**

While heavy snow amounts were widespread from North Carolina to Maine, the heaviest snow amounts from this storm ended up in New Jersey, with a report of 31 inches in Elizabeth, New Jersey. The heaviest snow amounts ended up in the immediate NYC area with widespread 20-30 inch amounts, with smaller amounts further west where there sharp cut off between the light and heavy snow was, leading to anywhere between 4 inches to as much as 20 inches in the western parts of the area. Long Island generally saw between 10 and 20 inches of snow, and southern Connecticut saw anywhere between 5 inches further east to as much as 18 inches further southwest. With 20 inches observed in Central Park, this was the 6th biggest snowstorm there on record.

While the storm verified for the area and even overperformed, the storm underperformed in some areas. Washington DC was expected to see between 3 and 6 inches of snow but as the map above shows, ended up with less than an inch. The storm's heavy snow axis ended up over the immediate NYC area as expected, but moved north northeast from there, not northeast, with lighter snow amounts than expected from eastern Connecticut into parts of Rhode Island and Massachusetts.

What made this storm different than some of the big snowstorms last year was that this storm was a true blizzard. While last year's snowstorms brought heavy snow and strong winds, none of them had these conditions as strong or as long lasting as this storm had, where many places observed wind gusts over 40 mph and near zero visibility for as much as 5-8 hours. The big snowstorm at the end of February last winter was mainly a wet snow event, which led to trees and roofs collapsing, while this storm produced powder snow, and the winds with this storm were so strong that they caused the snow to blow all over the place, reducing the risk of collapsing roofs and trees but created huge snow drifts.

Overall, this storm was one of the worst to affect the New York City area on record, and its surprise was just as bad as its impact, as it was not expected to be a major snow producer until the day before the storm. After a year of extreme weather events, ranging from the February blizzards to extreme rainstorms, hurricane force wind gusts, extreme heat waves and tornadoes in New York City, this blizzard is only an addition to a year of extremes that will be remembered for a long time.