Yet another record snowstorm wallops New England

The epic winter of 2010 - 2011 delivered yet another major pounding to New England yesterday and today, and residents are digging out today from the winter's third record snowstorm. The heaviest snows from this newest onslaught hit coastal New Jersey and New York City, where snowfall rates up to 4 inches per hour were accompanied by hundreds of lightning strikes. The 19.0" inches that fell in New York City's Central Park made it the 8th largest snowstorm for the city in recorded history. When combined with the heavy snows of 1 - 2 feet that fell during the Nor'easter just two weeks ago, January 2011 now ranks as the snowiest January on record in New York City, Newark, Bridgeport, and Hartford.


Figure 1. Scene from Times Square, New York during the peak of the January 26 - 27, 2011 Nor'easter. Near midnight, snowfall rates reached 4 inches per hour in thunderstorms. Image credit: Earthcam.com web cam, and captured by Christopher C. Burt.

Remarkably, five of New York City's top-ten snowfalls of the past 142 years have occurred 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) 19.0" Jan 26-27, 2011
9) 18.1" Mar 7-8, 1941
10) 17.7" Feb 5-7, 1978

Philadelphia, PA picked up 15.1", from today's storm, making it the tenth largest snowstorm in city history. Philadelphia has now had four of its top ten snowfalls in just over a year--a remarkable string of storms, considering record keeping began 127 years ago, in 1884. So far this winter, Philadelphia has picked up 37.8" of snow. An average winter should have had just 7.5" by now.

The top ten snowstorms on record for Philadelphia:

1. 30.7", Jan 7-8, 1996
2. 28.5", Feb 5-6, 2010 (Snowmageddon)
3. 23.2", Dec 19-20, 2009 (Snowpocalypse)
4. 21.3", Feb 11-12, 1983
5. 21.0", Dec 25-26, 1909
6. 19.4", Apr 3-4, 1915
7. 18.9", Feb 12-14, 1899
8. 16.7", Jan 22-24, 1935
9. 15.8", Feb 10-11, 2010
10. 15.1", Jan 26-27, 2011
10. 15.1", Feb 28-Mar 1, 1941


Figure 2. Change in snow depth for the 24 hours ending at 1am today shows that an area of 12 - 20" of snow fell from just southwest of Philadelphia, PA to near Bridgeport, CT. The heaviest snows had not quite ended by this time in Connecticut, Rhode Island, and Massachusetts. Up to two inches of snow melted in upstate New York (orange colors) during this period. Image credit: NOAA.

Just an ordinary-strength Nor'easter
The Nor'easter was of very ordinary strength, with a central pressure of just 987 mb this morning as it passed Cape Cod. Typically, a Nor'easter needs to have a central pressure in the 960 - 980 mb range to dump the kind of heavy snows that this storm generated. The storm did not have a widespread area of strong winds, though Provincetown on Massachusetts' Cape Cod recorded sustained winds of 40 mph, gusting to 60 mph, at 2am EST this morning. Only minor coastal flooding was reported in New England from the storm. However, like the January 12 - 13 Nor'easter of just two weeks ago, this week's rather ordinary-strength Nor'easter managed to assemble the perfect mix of conditions needed to transport moisture to a region of the storm highly favorable for heavy snow formation. Many heavy snow bands with snowfall rates up to 4 inches per hour formed over New England, with some of these bands intense enough to generate lightning and thunder.

Some selected city snowfall amounts for the January 26 - 27, 2011 storm:

NYC Central Park, NY 19.0"
Newark, NJ 18.9"
Philadelphia, PA 15.1"
Wilmington, DE 10.4"
Providence, RI 10.5"
Boston, MA 9.9"

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, particularly so in mid- late-winter. 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, both the December 26 and 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. These two storms were the first Nor'easters 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. Philadelphia got 12.4" from the December 26 Nor'easter and 15.1" from today's storm. The National Weather Service stated in December that prior to this winter, only one La Niña winter in the past century has had a storm that dumped more than 10" of snow on the city--a December 1909 Nor'easter.


Figure 3. 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.

Why such 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. This year's record snow storms were all the more unusual, as they came during La Niña conditions in the Eastern Pacific. Is it random chance, or did climate change play role? Well, it could be either, and we simply don't know the answer. 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)

Jeff Masters