Clark
(Meteorologist)
Wed Sep 07 2005 12:41 AM
Re: Tropical Storm Warnings Up Titusville to Jupiter Tropical Depression 16 Forms Off Florida Coast

About a NE Florida landfall: history is against it, but a number of other storms have made landfall there. A tropical depression a few years back was the most recent storm to do so. It's certainly not unprecedented.

With regards to the colder air: air temperatures over the southeast US and over the open waters (e.g. the Gulf Stream) are pretty warm, averaging in the mid-upper 80s. Tropical cyclones by definition have a warm-core, where temperatures in the center of the storm are warmer than those found outside of the storm; this is the case for TD 16, with warmer temperatures found by recon in the center of the storm than outside of it (about 1-2 deg C; the greater the differential, the stronger the storm...usually). I won't go into the discussion of how this occurs right now; maybe during the off-season in a series of mini-featurettes I've got planned.

Midlatitude systems -- those associated with cold fronts -- are generally cold-core by nature (though warm-core extratropical cyclones do exist). Their growth mechanisms differ from hurricanes -- again, a long topic for another day after the season -- but one of the things associated with these systems and one of the potential causes for storms to either develop in an extratropical fashion or undergo extratropical transition is a temperature gradient. With a cold air infusion from the midlatitudes, you set up a strong temperature gradient (either at the surface or aloft) between the environment of the tropical cyclone and the midlatitude environment, with some of this latter environment potentially encroaching upon the storm. It would not lead to tropical development; instead, it would either lead to the storm weakening or beginning to undergo extratropical transition (at least to the point of taking on more of a hybrid structure).

This changes what you can expect in terms of the wind field and precipitation distributions with the storm as the wind field expands outward and the precipitation distribution taking on more of an asymmetric (almost frontal-like) nature. Were this storm to undergo such an evolution, most of the weather may remain offshore given the preferential nature for this to occur on the east side of the storm; it is certainly not a given that this will occur, however. It's a tough forecast for this storm from all angles -- the spread in the models has that classic "squashed spider" movement that the NHC loves to split down the middle and take slowly, often with good results -- and everyone along the northern Gulf coast to the Carolinas needs to watch this one, just in case.



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