Transverse vertical circulations

What?!? My synoptic meteorology students may remember how direct and indirect transverse vertical circulations lead to enhanced precipitation in winter storms. Looking at the 120 hr model of the 12z run from Thursday, you can clearly see two jet streaks that are off-set, with the northern jet streak leading the southern jet streak. What does this mean?

Due to this arrangement, there will be rising air to the southwest of the northern jet streak and rising air to the northeast of the southern jet streak. Note that both areas of rising air from the jet streak will occur right over the TN valley. This jet streak setup will continue as the surface low moves all the way to the coast, which means that liquid precipitation amounts of 1-2″ are likely in a band north of the surface low. Right now, it looks like this band will go right over the mid-south. Unfortunately for anyone who likes snow, it appears as if this will be mainly a rain event for south-central KY although we may get a small amount of accumulating snow at the end of the storm. Areas in the mid-Atlantic and/or southern New England though could get snowfall amounts >12″.

A bigger deal in the world of weather is the potential storm for President’s day weekend. Now there’s never any reason to get too excited about a storm depicted on the 276 hour model (12z Thursday), but this storm, as depicted by the models, has the appearance of an all-timer for the East Coast. Of course, the very next model run (18z Thursday) shows a much weaker storm that goes straight out to sea. I’ll wait until the Valentine’s storm comes through before I start talking much about the next one.

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