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Posted at 02:40 PM ET, 08/22/2012

All eyes on Isaac as it enters the Caribbean Sea; RNC impacts?

At 2 p.m. EDT, Isaac’s maximum sustained winds were still near 45 mph. Tropical-storm-force winds extended up to 60 miles from the storm center with Isaac racing westward at 21 mph, ready to move through the Leeward Islands during the next several hours. There are quite a number of hurricane watches, tropical storm warnings, and tropical storm watches in effect, and you should always find the latest at the National Hurricane Center’s website.


Tropical Storm Isaac. (NOAA/NESDIS - NOAA/NESDIS)
A radar loop from Martinique will capture the passage of the developing storm across the Leeward Islands, and later, it will be in range of other radar sites as well, and those loops will be added to that list.

There is still a bit of model spread in the track forecast. However, in the near future, there is good agreement that Isaac will pass over the mountainous island of Hispaniola on Friday, which should put a hefty brake on whatever intensification occurs prior to then in the eastern Caribbean.

Right now, the large-scale environment is generally conducive for further strengthening, with the biggest exception being light vertical wind shear allowing some dry air to the north to possibly sneak into the circulation.


Latest model track guidance from 8am EDT today. (NCAR/TCGP - NCAR/TCGP)

The two plots below are from two leading global models (GFS and ECMWF) and show the surface pressure and mid-level steering valid at the same time: next Monday at 8 p.m. EDT. A weaker storm will be allowed to track further west, while a stronger storm is more likely to recurve toward the north a little sooner.

In addition, the strength of the mid-level steering ridge is forecast to be weaker in the top scenario. This is a case where anyone in the U.S . between the north-central Gulf coast clear over to the Carolinas should be paying very close attention. While that is a large length of coastline, it actually represents a fairly small 5-day track error.


Comparison of two global model Monday evening. Adapted from Weather Examiner. (original figures courtesy of Raleigh - original figures courtesy of Raleigh)
Republican National Convention

For people arriving in Tampa this weekend for next week’s Republican National Convention, I’d say there’s a large chance that the airports will be negatively affected around there, but it’s far too early to say anything about a hurricane landfall near Tampa. It does seem safe to say, however, that the RNC will experience some adverse weather from Monday-Tuesday.

Tropical Depression #10

Much further east in the Atlantic, Tropical Depression 10 has also just formed about 700 miles west of the Cape Verde islands, or about 1700 miles east of the Lesser Antilles. While it is forecast to intensify and become Tropical Storm Joyce in the coming days, it is not near land and won’t be any time soon

By Brian McNoldy  |  02:40 PM ET, 08/22/2012

Categories:  Latest, Tropical Weather

 
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