Thursday, October 21, 2010

Oct 28 Cold will Blast then Pass

The weather event scheduled on or shortly after Oct 28 now has some detail that can be added.  Last week the signal that something is coming came from Darwin, AU and Tahiti.  This week the expected path of Typhoon Megi provides more detail.

How does a West Pacific typhoon help us here in NC and VA?  It clearly defines the shape and extent of the oceanic ridge of high pressure and on occasion the exact timing of passing mid-latitude troughs.  Waves in the atmospheric circulation then can be observed crossing the Pacific ocean with no interference from land masses.

The track of a Typhoon indicates whether a ridge or a trough will
be in the Eastern US in 6-10 days.

Typhoon Megi is expected to turn east of north for about 2 days before turning NW and hitting land.  If this scenario is correct a cold front will draw the storm system N and NE but fail to be strong enough to hold on.

Joint Typhoon Warning Center forecast for Typhoon Megi

Therefore my expectation is that a strong cold front will pass through the eastern US near Oct 28th but the associated cold air will blast in and lift out in 2-3 days.   If we are fortunate, perhaps the rapid movement of the system will prevent frost from ending summer tomatoes and peppers (Yes, I have 11 tomatoes!!!).  Do the models agree? Here is the GFS depiction of a front passage near Oct 28 and cold high pressure.

Arctic Vortex in Central Canada is expected to retrograde (move westward)
Cold air masses must go around then underneath.

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