Mighty Post-Christmas Nor'easter wallops the Northeast U.S.

A major blizzard continues to pound New England with heavy snow and winds gusting to near hurricane force as the 976 mb low tracks slowly northeastward into the Gulf of Maine. The snow has mostly ended across New York City and the mid-Atlantic, where snowfall rates as high as 3 - 4 inches per hour occurred during "thundersnow" snow squalls at the peak of the storm late last night and early this morning. At the height of the storm, blizzard warnings were in effect for the entire U.S. coast from Maryland to Maine. The heaviest snows fell about 50 miles to the west and north of New York City. Lyndhurst, New Jersey, located about 15 miles northwest of New York City, got 29 inches, and several nearby towns also reported snows in excess of 24 inches. Though the snow has mostly ended in these regions, strong winds will continue through the early afternoon, creating blizzard conditions in blowing snow.


Figure 1. Satellite image from 8am EST December 27 of the Post-Christmas Blizzard of 2010 over New England. Image credit: NASA/Goddard Space Flight Center.

The blizzard is in full swing across much of Massachusetts, Rhode Island, Connecticut, New Hampshire, and Maine, where snowfall rates of 1 - 2 inches per hours are common in heavy snow bands, with high winds creating blizzard conditions. The strongest wind gust from the mighty blizzard was 80mph, measured at Wellfleet on Cape Cod at 10:52pm last night. Wind gusts of 50 - 60 mph have been common along most of the coast of Connecticut, Rhode Island, and Southeast Massachusetts. The storm's strong northeast winds whipped up a storm surge of 2 - 3 feet that affected the coast just north of Boston, and in Central Long Island Sound, during the high tide cycle at 3am this morning. Moderate flooding that shut many roads occurred, and some damage to buildings probably resulted. The flooding danger for Massachusetts and Long Island Sound is now past, as the storm moves into Maine and Canada.

Snowfall amounts at major cities for the December 26-27, 2010 storm, as of 8am EST:

Newark, NJ 20.0"
Atlantic City, NJ 19.0"
East Boston, MA 16.5"
Ocean City, MD 13.5"
NYC Central Park, NY 13.0"
Philadelphia, PA 12.4"
East Providence, RI 12.0"
Danbury, CT 11.1"
Augusta, ME 10.0"
Woodstock, VT 10.0"
Bridgeport, CT 8.0"
Boston, MA 6.5"
Wilmington, DE 3.4"

An unusual Nor'easter for a La Niña year
This winter, we are experiencing La Niña conditions in the Equatorial Eastern Pacific, meaning that cold waters have upwelled from the depths off the coast of South America, cooling a huge region of Pacific waters to below-average levels. In most winters, the presence of La Niña acts to deflect the jet stream in such a way the the predominant storm track takes winter storms into the Pacific Northwest, then down through the Upper Midwest and Ohio Valley. According to Dr. David A. Robinson, the New Jersey State Climatologist and Chairman of the Department of Geography at Rutgers University, this sort of flow pattern keeps New England safe from Nor'easters, as storms tend to move from the Ohio Valley northeastwards into Canada, keeping New England in a warm southwesterly flow of air. However, today's storm defied climatology, and gave the mid-Atlantic and New England one of their worst poundings on record for a La Niña Nor'easter. It was the first storm in at least ten La Niña winters, dating back to 1970, to bring 10" of more of snow to New Jersey, according to Dr. Robinson. In Philadelphia, which got 12.4" from this storm, the National Weather Service stated that only one La Niña winter in the past century has had a storm that dumped more than 10" of snow on city--a December 1909 Nor'easter. The reason for the unusual Nor'easter this year is that it happened to get started right when the atmosphere was transitioning from one major flow pattern to another. Since late November, we have been locked into a pattern featuring very weak low pressure over Iceland, and weak high pressure over the Azores--a strongly negative North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). This pattern, which has allowed a lot of cold air to spill out of the Arctic and into the Eastern U.S. and Western Europe, is now breaking down and transitioning to a very different winter pattern. This new pattern will feature a more typical configuration for winter, with the Icelandic Low and Azores High close to their usual strengths. Today's Nor'easter managed to sneak in just as the atmosphere was transitioning from one major flow pattern to a new one, resulting in the rare La Niña snowstorm for New England. The new winter flow pattern looks to stay in place for at least the first two weeks of January, resulting in warmer than average winter weather for both the U.S. East Coast and Western Europe.

Jeff Masters