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Fay is not strengthing much yet

By: Dr. Jeff Masters, 8:40 PM GMT on August 17, 2008

Tropical Storm Fay continues to look unimpressive as it tracks south of Cuba. Radar imagery from Punta del Este, Cuba shows that the low-level spiral bands are sparse and poorly organized. Visible satellite loops show that heavy thunderstorm activity only surrounds about 1/3 of the center of the storm. Fay is in a moderately favorable wind shear environment, with upper-level winds from the west creating about 10 knots of wind shear. Upper level outflow is well-established only to the north and east. The highest surface winds found between 2pm and 4pm EDT by the latest Hurricane Hunter flight were 47 mph. However, the pressure is falling, and stood at 1003 mb at 3:11 pm EDT.

The forecast for Fay
Fay is gradually building an eyewall this afternoon, but probably does not have time to complete this process before crossing Cuba. This means that the storm will have to start this process all over again Monday morning, delaying intensification longer than the models had predicted.

The computer models have come into better agreement, predicting that Fay will stay south of Cuba a bit longer and move further west than expected before turning northwest and crossing the island. This reduces the threat to Key West and Southwest Florida, but increases the threat to the Florida coast between Sarasota and the Florida Panhandle. This also increases the chances that Fay will hit Florida as a hurricane, since it will have more time over water.

The latest (8 am EDT) run of the GFDL model puts Fay ashore Monday night near Sarasota as a Category 1 hurricane with a 976 mb pressure and 80-85 mph winds. The HWRF model foresees a landfall on Tuesday morning further north, past Cedar Key, and makes Fay a strong Category 2 hurricane with a 945 mb pressure and 110 mph winds. Both of these forecasts are probably too intense, given Fay's current state of disorganization. Only the ECMWF model is currently forecasting a motion all the way across the Florida Peninsula and out into the open Atlantic. This model then foresees a triple hit on Florida--motion back across Florida from east to west, followed by a third Florida landfall int he Panhandle. The UKMET and NOGAPS models continue to show a threat to the Florida Panhandle.

If Fay hits the Sarasota/Tampa Bay region, these are the kind of probabilities for intensity I'm thinking:

Tropical storm: 50%
Category 1 Hurricane: 35%
Category 2 hurricane: 10%
Category 3+ Hurricane: 5%

For a landfall further north in the Panhandle, my probabilities are:

Tropical storm: 35%
Category 1 Hurricane: 35%
Category 2 Hurricane: 20%
Category 3+ Hurricane: 10%

Links to follow
Wundermap for Cuba and the Florida Keys
Punta del Este, Cuba radar
Key West, FL weather

Elsewhere in the tropics
Several of the reliable computer models are predicting development of a tropical wave currently located off the coast of Africa, just south of the Cape Verde Islands. This system is expected to track west-northwest and be near or just north of the Northern Lesser Antilles Islands 5-7 days from now.

I'll have an update Monday morning (or later this evening, if there's some significant development to report).

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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