Sunday, January 23, 2011

Update on Eastern Storm Potential

The weather situation is interesting this morning ("interesting" is a euphemism used by meteorologists to mean "really challenging").

Forecasting winter storms is very much a chess game. We have to figure out where the low and high pressure systems will move, the "coldness" of the air and its configuration above the earth (if it is warm aloft, it will be freezing rain rather than snow at the ground even if the ground temperature is below freezing), and how much moisture/humidity the storm has to work with the create the precipitation.

The worldwide computer model run last night by the European Consortium for Medium Range Forecasting continues to show the upper atmospheric low pressure system ("L" on the map) in the right position to produce heavy snow, or even a blizzard, in the Middle Atlantic and Northeast states.
However, temperatures are too warm for much snow to fall -- most of the precipitation would be rain (accompanied by a lot of wind) -- if this forecast is correct.

This morning's Global Forecast System model run by the U.S. National Weather Service shows a much weaker system (designated by an "X" because it no longer has the 360° wind circulation needed to be a low) going out to sea.  This model is somewhat colder than the European, so there are moderate snows forecast along the coast (not shown).
Note that the X is farther east than the "L" on the above graphic. 
The article linked to below about the progress we have made in forecasting winter storms is correct. But, a lot of that progress is in the 48 hour range. These forecasts are valid Wednesday, so we aren't within the 48 hour range as yet.

Stay tuned.


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