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Posted at 02:00 PM ET, 05/25/2012

Another Tropical Storm off the Southeast coast?

Not yet. Right now, the National Hurricane Center (NHC) is monitoring an area of low pressure just off the Southeast coast for possible development. This feature (named AL94) is roughly 150 miles east of the Florida coast.


Infrared satellite picture from this morning (UW-CIMSS)

Though it is not expected to move very much during the next day or two, it is somewhat concerning that the model consensus shows AL94 turning back to the west and approaching, if not crossing, the U.S. coast in 2-3 days.


Track guidance for AL94.(TCPG/NCAR)

However, the good news is that AL94 is currently an ill-formed and diffuse system, battling an environment highly unfavorable for tropical cyclone genesis. And though it may evolve further, it has a long way to go.

In fact, AL94 is not really a tropical system (yet). It is an elongated area of disturbed weather, whose surface pressure falls have so far been largely accounted for by non tropical processes tied to a nearly stationary upper trough in the region.

As anticipated by our last post the presence of this upper-level feature (shown below on the left) has introduced strong wind shear and a fetch of exceptionally dry air over this part of the world (shown by the orange shading in the picture on the right). Most of the clouds you see in the satellite picture below are high-level cirrus clouds blown a long way downstream from the surface pressure trough.


Upper-level winds (left) and water vapor imagery (right). (TwisterData.com and UCAR)

That said, this particularly unfavorable setup is expected to become a little more supportive over the next couple of days. The global weather models suggest the upper trough will weaken somewhat, contract in scale, and ostensibly lose some of its wind shear. But because the extratropical presence probably won’t ever leave AL94, the odds should remain stacked against significant tropical development. 

And though water temperatures are warm and deep enough to support a hurricane over the Gulf Stream, some 100+ miles or so offshore, closer in, the water is cooler and the heat content drops off considerably. As such, the experts at NHC have rightly suggested AL94 might evolve into a subtropical storm instead.

Still, residents along the Southeast U.S. coast should monitor the progress of AL94. Even in the likely scenario that it never turns into a hurricane, rainy and breezy conditions are quite possible during the second half of the holiday weekend from central Florida to South Carolina.  We’ll keep you posted.

By  |  02:00 PM ET, 05/25/2012

Categories:  Latest, Tropical Weather

 
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