Saturday, February 9, 2013

President's Day Potential Nor'easter

The new American GFS model is predicting a massive Nor'easter to develop off the coast of New England around President's Day.

The energy for this storm is projected to drop south from the Pacific Northwest and strengthen as it enters the southern Plains. From there, it swings east and develops a negative tilt as it pushes northeast into the East Coast. The development of a negative tilt means the highest vorticity values at the 500 millibar level are positioned to the southeast. This is observed in the upper left hand panel of the above forecast image, which is valid for the night just before President's Day.  Typically, negatively-tilted storm systems are watched in the spring, when cold air can run aloft and provoke stronger thunderstorms than positively-tilted storm systems. As you might guess, positively-tilted storm systems have their highest vorticity values tilted towards the Southwest. The presence of a negatively-tilted winter storm would likely increase precipitation totals as cold air runs aloft and convective snow bands are enhanced. Thundersnow would naturally be more widespread in the presence of cold air aloft.

Snow totals from this system in a 24 hour period would approach the one foot mark, especially in western Pennsylvania. West Virginia and eastern Kentucky could surpass 6 inches, as well as western parts of the state of Virginia (not the state WV). New York, eastern Tennessee and portions of Maine could see shovelable snow, while other states get more of a quick, light accumulation. This forecast is certainly going to change, but this potential must be closely monitored. High latitude blocking will be increasing, leading to higher chances for these Nor'easters.


1 comment:

Eric said...

Now Andrew, when was the last time we such a strong model consensus on a potentially monster storm so far out by ALL the models even the NOGAPS? Look no farther than the March 1993 Superstorm, but we'll see what happens still about a week out.