Why Snowmageddon? Gulf Stream surface temperatures at record levels, 11.5C (21F) above normal
Alex Brown
http://www.washingtonpost.com/news/energy-environment/wp/2015/02/10/what-the-massive-snowfall-in-boston-tells-us-about-global-warming/
“Sea surface temperatures off the coast of New England right now are at record levels, 11.5C (21F) warmer than normal in some locations,” says Penn State climate researcher Michael Mann. “There is [a] direct relationship between the surface warmth of the ocean and the amount of moisture in the air. What that means is that this storm will be feeding off these very warm seas, producing very large amounts of snow as spiraling winds of the storm squeeze that moisture out of the air, cool, it, and deposit it as snow inland.”
Warmer oceans also increase the temperature contrasts that winter storms encounter when they hit the East Coast, notes Mann — and this ups their strength.
“Heavy snows mean the temperature is just below freezing, any cooler and the amount would be a lot less,” adds Kevin Trenberth, a climate expert at the National Center for Atmospheric Research. “Warmer waters off the coast help elevate winter temperatures and contribute to the greater snow amounts. This is how global warming plays a role.” ...
What we’re seeing also fits a trend for New England. As the U.S. National Climate Assessment so helpfully illustrates, the region has seen a dramatic 71 percent upswing in extreme precipitation from 1958 to 2012: see http://img.washingtonpost.com/news/energy-environment/wp-content/uploads/sites/43/2015/02/CS_very-heavy-precip_V8-1.png