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Fay pounds the Florida Keys, begins to form an eyewall

By: Dr. Jeff Masters, 7:36 PM GMT on August 18, 2008

Tropical Storm Fay is pounding the Florida Keys with high winds and heavy rain, as it churns north-northwestward towards a landfall in Southwest Florida. Winds at the Sand Point Buoy near Key West were sustained at 56 mph last hour, and the center of Fay passed over Key West at about 3:30 pm EDT. Sombrero Key buoy, at an elevation of 159 feet, reported sustained winds of 60 mph last hour. The latest Hurricane Hunter missions have found a large areas of 50-60 mph winds in the heaviest thunderstorms. However, the pressure has not fallen significantly, and was 1001 mb at 3pm.

From wunderground member keeywester:

Wow...Fay is really hitting us hard right now (1:52 p.m.) I'm guessing we are sustained at close to 50 with higher gusts out of the ENE. I have water spilling in under my east facing door on the third floor. We are in a really intense band and visibility is really low. Just thought I'd give you a quick update.

Dan Hogberg in Key West (Sunset Marina Condos)

Indeed, radar estimated rainfall (Figure 1) shows that about 5 inches of rain fell in Key West in just a few hours this afternoon. Long-range radar out of Key West shows that Fay is beginning to build an eyewall, which is about 40% complete. Fay's spiral bands are steadily organizing and growing more plentiful. Visible satellite loops show a lack of heavy thunderstorm activity and upper-level outflow on Fay's west side, where wind shear from an upper-level low to the west is interfering with the storm. Wind shear of 10-15 knots is expected to continue over Fay until the storm makes landfall on the southwest coast of Florida. This amount of wind shear usually means only modest intensification can occur, and Fay is unlikely to make it to Category 2 strength (96 mph or greater).

Figure 1. Latest radar-estimated precipitation for Fay.

Impact on the Caribbean islands
Fay dumped up to 8 inches of rain in southern Haiti, the southern Dominican Republic, and central Cuba, according to satellite estimates. The resulting flooding has probably killed at least 36 people. Thirty of those deaths came in Haiti when an overloaded bus attempted to cross a flooded river and flipped. Flooding from Fay also killed two people in Jamaica and four people in the Dominican Republic.

Impact on the west coast of Florida
The west coast of Florida will take the full brunt of Fay's fury early Tuesday morning. With the exception of the NOGAPS model, the computer models have finally come into agreement on a landfall, with their 8 am EDT runs. The consensus is that landfall will be in Southwest Florida, between Marco Island and Fort Myers. Marco Island is my guess of a landfall location given the trend of Fay to track to the right of the forecast. With Fay's expected track nearly parallel to the shore, though, a slight deviation in the path will result in a large change in where the eye comes ashore. Storm surge will be a major concern to the region just to the right of where the center comes ashore. For the Naples region, a Category 1 hurricane can generate storm surges of 4-8 feet (Figure 2). Both the GFDL and HWRF models are forecasting a Category 1 hurricane with winds of 80-90 mph at landfall. Fay does not have time to intensify into a Category 3 hurricane before a landfall in Southwest Florida. If Fay follows a track further north and makes landfall near Tampa Bay, as the NOGAPS model predicts, there is a 10% chance it couuld intensify into a Category 3 hurricane.

South Carolina? New Orleans? Where will Fay go next?
The computer models continue to show an unusual amount of disagreement about the longer term path of Fay. The official NHC forecast follows the GFDL and HWRF models, which takes Fay northwards through the Florida Peninsula. However, the latest runs of these models now predict Fay will emerge off the east coast of Florida, restrengthen a bit to a 60-70 mph tropical storm, then make landfall Wednesday along the Georgia/South Carolina coast. This solution assumes that the trough of low pressure turning Fay northward will be strong and enough and be moving slow enough to pull Fay all the way northwards into the U.S.

A weaker trough is predicted by the rest of the models, which foresee that Fay will stall over central Florida or the adjacent Atlantic Ocean on Wednesday. A ridge of high pressure will then build in, forcing Fay westward across the northern Gulf of Mexico. A second landfall in the Florida Panhandle or in Louisiana near New Orleans is then a possibility. Since more and more of the models are trending this way, I believe this solution has an equal chance of being correct. "The Joker" may be around to trouble us for another full week or longer.

Links to follow
Wundermap for the Florida Keys
Key West, FL weather
Naples, FL weather
Fort Myers, FL weather
Miami, FL weather

Figure 2. Worst-probable storm tide inundation (inundation from storm surge plus an adjustment for the mean high tide that occurs in the Naples area). The colors scale to various Category hurricanes--1, 2, 3, 4, and 5. The map was compiled using data from NOAA's SLOSH model. Image credit: floridadisaster.org.

Figure 3. Worst-probable storm tide inundation (inundation from storm surge plus adjustment for the mean high tide that occurs in the Fort Myers area). The colors scale to various Category hurricanes--1, 2, 3, 4, and 5. The map was compiled using data from NOAA's SLOSH model. Image credit: floridadisaster.org.

Elsewhere in the tropics
A tropical wave near 13N 36W, about 700 miles west-southwest of the Cape Verde Islands, has gotten better organized this afternoon. This system (94L) shows signs of rotation on visible satellite imagery, and heavy thunderstorm activity has steadily increased near the center in recent hours. Wind shear is a low 5-10 knots over this disturbance, and is expected to drop below 5 knots Tuesday. The storm is over warm 28°C waters, and is in a moist environment, so continued development is likely. NHC is currently giving this system a medium (20%-50% chance) of developing into a tropical depression by Wednesday afternoon. This storm is expected to track west-northwest and be near the Lesser Antilles Islands on Saturday. Wind shear is forecast to remain below 15 knots for the next five days, which will favor development. However, there is a large area of dry air and Saharan dust to the northwest of the storm, as seen on water vapor satellite imagery, and this will probably begin to interfere with 94L's development by Wednesday. The GFDL, HWRF, and SHIPS models all develop 94L into a tropical storm that moves just north of the Lesser Antilles Islands by Saturday.

I'll have updates throughout the day.

Jeff Masters
Fay in all her wet and windy glory.
Fay in all her wet and windy glory.
Unfortunately the only working camera I have at the moment is in my cellphone, 3.2 mp LG Dare. But not too shabby :)

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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