Clark
(Meteorologist)
Thu May 31 2007 12:26 AM
Re: Memorial Day Weekend Area to Watch

I don't have a lot to add to what Tip and HF outlined in the past 10 posts or so, so I'll keep this brief. The way the upper level pattern has established itself, anything that develops is likely headed for the Florida panhandle. The trough over the Gulf isn't going anywhere; water vapor loops tonight clearly show it digging in over Mexico and the western Gulf and the system well to its north over the N. Plains isn't going anywhere anytime soon. Basically, what you see is what you get right now unless the pattern unexpectedly changes. Don't bank on it.

Second question is of what degree of development we are going to see. Generally, the sooner it develops, the more likely it gets a tropical classification. Though conditions are not overly favorable there in the NW Caribbean, shear is slightly weaker and upper level diffluence (winds moving apart directionally) is favorable for at least persistent convective development. It does have the Yucatan Peninsula to contend with, however, hindering those prospects in the short-term. The longer it waits to develop, the stronger the baroclinic (midlatitude) forcing it will encounter and thus the more likely it is of the subtropical or extratropical variety.

Tip made a good comment about the improved prospects if/as the storm starts to accelerate to the northeast; this would reduce the storm-relative shear across it and allow for some added development. We have seen a number of Gulf storms get going over the past 10 years under such conditions, with all of them ending up lopsided to the east and not particularly strong overall.

So, if we assume something gets going, what can we expect? Mostly rain. There likely won't be the long fetch or duration (or intensity) of winds to lead to significant surge -- whether tropical or extratropical. Storm intensity should be kept in check due to shear and cool SSTs generally in the mid-upper 70s over a shallow layer in the northern half of the Gulf. If it evolves baroclinically/extratropically, there's just not enough energy aloft over the Gulf to see it significantly deepen in that manner either. Think moderate tropical storm on the high end. It does have plenty of moisture to work with, though, and should spread all of it over Florida and the coastal SE into the coming weekend. As a result, a widespread moderate rain event is possible if not likely; generally 1-2" with spots at 3-6" depending on the track and structural evolution.

All of that said -- a hybrid cyclone heading for Florida into the weekend looks like a good bet, likely with some much needed rains for most if not all of the state. Will it be our second classified storm of the year? Jury is still out; I would tend to say no. One to watch, though.



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