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Posted by: JeffMasters, 3:07 PM GMT on December 27, 2010

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 Ni�a year
This winter, we are experiencing La Ni�a 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 Ni�a 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 Ni�a Nor'easter. It was the first storm in at least ten La Ni�a 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 Ni�a 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 Ni�a 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.

Northeast U.S. digs out from yet another history-making snowstorm

Posted by: JeffMasters, 4:53 PM GMT on December 28, 2010

The remarkable Post-Christmas blizzard of 2010 has ended for the United States, as the storm has trekked northeastward into Canada. The blizzard dropped epic amounts of snow during its rampage up the U.S. Northeast coast Sunday and Monday, with an incredible 32" falling in Rahway, New Jersey, about 15 miles southwest of New York City. The highest populated areas of New Jersey received over two feet of snow, including the Newark Airport, which received 24.1". Snowfall amounts were slightly lower across New York City. The blizzard of 2010 dumped 20.0" inches on New York City's Central Park, making it the 6th largest snowstorm for the city in recorded history, and the second top-ten snowstorm this year. Remarkably, New York City has had four of its top-ten snowfalls in the past decade (highlighted in the list below.) According to the National Weather Service, the top ten snowstorms on record for New York City's Central Park since 1869 should now read:

1) 26.9" Feb 11-12, 2006
2) 26.4" Dec 26-27, 1947
3) 21.0" Mar 12-14, 1888
4) 20.8" Feb 25-26, 2010
5) 20.2" Jan 7-8, 1996
6) 20.0" Dec 26-27, 2010
7) 19.8" Feb 16-17, 2003
8) 18.1" Mar 7-8, 1941
9) 17.7" Feb 5-7, 1978
10) 17.6" Feb 11-12, 1983

Newark's 24.2" was one of that city's top-ten snowstorms of all-time, and the 20.1" that fell on Atlantic City, NJ was the city's second largest snowfall in history. Atlantic City's three biggest snowstorms have all occurred in the past ten years:

1) 21.6" Feb 15-18, 2003
2) 20.1" Dec 26-27, 2010
3) 18.2" Feb 5-6, 2010

Philadelphia, PA picked up 12.4", the city's fourth one-foot plus snowstorm in just over a year--a remarkable string of storms, considering the city has had just 24 such snowfalls in history, since 1884. According to phillyweather.net, the latest snowstorm brought Philadelphia's 2010 snowfall for the calendar year to 67.3", breaking the mark for snowiest year ever (previous record: 57.0" in 1978.)


Figure 1. Scene from Brooklyn, New York after the Post-Christmas blizzard of 2010. Image credit: Wunderphotographer AK2NY.

Some selected city snowfall amounts for the December 26-27, 2010 storm:

Rahway, NJ 32.0"
Great Kills, NY 29.0"
Piermont, NH 25.0"
Newark, NJ 24.2"
Landgrove, VT 21.0"
Atlantic City, NJ 20.1"
NYC Central Park, NY 20.0"
Boston, MA 18.2"
Ocean City, MD 13.5"
Philadelphia, PA 12.4"
East Providence, RI 10.0"
Danbury, CT 11.1"
Augusta, ME 15.0"
Dover, DE 9.0"
Asheville, NC 9.0"
Bridgeport, CT 8.0"
Huntsville, AL 6.0"
Chattanooga, TN 3.0"


Figure 2. The annual average number of snowstorms with a 6 inch (15.2 cm) or greater accumulation, from the years 1901 - 2001. A value of 0.1 means an average of one 6+ inch snowstorm every ten years. Image credit: Changnon, S.A., D. Changnon, and T.R. Karl, 2006, Temporal and Spatial Characteristics of Snowstorms in the Contiguous United States, J. Applied Meteorology and Climatology, 45, 8, pp. 1141-1155, DOI: 10.1175/JAM2395.1.

An unusual number of top-ten snowstorms for the Northeast in recent years
The Northeast has seen an inordinate number of top-ten snowstorms in the past ten years, raising the question of whether this is due to random chance or a change in the climate. A study by Houston and Changnon (2009) on the top ten heaviest snows on record for each of 121 major U.S. cities showed no upward or downward trend in these very heaviest snowstorms during the period 1948 - 2001. It would be interesting to see if they repeated their study using data from the past decade if the answer would change. As I stated in my blog post, The United States of Snow in February, bigger snowstorms are not an indication that global warming is not occurring. The old adage, "it's too cold to snow", has some truth to it, and there is research supporting the idea that the average climate in the U.S. is colder than optimal to support the heaviest snowstorms. For example, Changnon et al. (2006) found that for the contiguous U.S. between 1900 - 2001, 61% - 80% of all heavy snowstorms of 6+ inches occurred during winters with above normal temperatures. The authors also found that 61% - 85% of all heavy snowstorms of 6+ inches occurred during winters that were wetter than average. The authors conclude, "a future with wetter and warmer winters, which is one outcome expected (National Assessment Synthesis Team 2001), will bring more heavy snowstorms of 6+ inches than in 1901 - 2000." The authors found that over the U.S. as a whole, there had been a slight but significant increase in heavy snowstorms of 6+ inches than in 1901 - 2000. If the climate continues to warm, we should expect an increase in heavy snow events for a few decades, until the climate grows so warm that we pass the point where winter temperatures are at the optimum for heavy snow events.

I've done some other posts of interest I've done on snow and climate change over the past year:

Hot Arctic-Cold Continents Pattern is back (December 2010)
The future of intense winter storms (March 2010)
Heavy snowfall in a warming world (February 2010)

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