Update Wednesday 5 pm: The first advisory was issued on Potential Tropical Cyclone Five (formally Invest 97L) in the central Atlantic, as it is likely to become the season's fifth tropical storm as it approaches the Windward Islands Friday. Tropical Storm Watches were issued for the island nations of Barbados, St. Vincent, the Grenadines, St. Lucia, Martinique and Guadeloupe.
The forecast track brings the future tropical storm into the eastern Caribbean by Saturday, then potentially nearing Cuba by Monday as a strong tropical storm. However, the National Hurricane Center expressed unusual uncertainty in the track and strength of the developing system beyond Saturday due to potential interaction with land and differences in model forecasts.
Original story published Wednesday morning, with the system identified as "97L"...
There is an increasing chance of a tropical storm in the Caribbean this upcoming holiday weekend -- sooner than what is average in early July.
The tropical wave, what meteorologists are calling "97L" for tracking purposes, is located about midway between Africa and the Lesser Antilles on Wednesday. 97L is moving rapidly toward the west-northwest at about 20 mph. On this track and forward motion, it will approach the Lesser Antilles on Friday, and is likely to be situated over the northeastern Caribbean near or south of Puerto Rico and Hispaniola this weekend.
A sprawling ridge of high pressure covers the Atlantic from the South Carolina coast eastward to a position north of the developing tropical system. This will force the tropical system to move rapidly from east-southeast to west-northwest beneath the ridge at a rapid pace. Normally, weather patterns like this are predictable over long periods, so confidence is high that whatever develops in the tropical Atlantic will be in the Caribbean this weekend.
A strong trough of low pressure and cold front is forecast to move off the Southeastern coast of the United States this weekend. Most computer model simulations indicate that this trough will weaken the steering ridge. Initially, this would cause the tropical system to slow down in the central Caribbean later this weekend. The steering pattern is highly uncertain early next week and any direct interaction with the islands of Hispaniola or Cuba also complicate the forecast.
Upper-level winds are forecast to be weaker than usual over the Caribbean. Oftentimes, strong wind shear in June and July limit the number of storms that develop in the central and eastern Caribbean. The global models are forecasting much lower-than-normal wind shear late this week and weekend over the Caribbean, which would favor strengthening of the developing system.
The National Hurricane Center says interests in the Leeward and Windward Islands should monitor the progress of 97L over the coming few days. Those with interests or plans in the Caribbean this holiday weekend should factor possible tropical development into their plans also.