Air Force C130J aircraft now near center of #Isaac, to see if winds or central pressure have changed.
Ann Romney now has Secret Service protection, on eve of husband's formal GOP presidential nomination - @AP
Tropical Storm Isaac is now 80 miles southeast of Key West, Fla., with maximum sustained winds of 65 mph
Hurricane watch for Florida's east coast from Golden Beach southward to Ocean Reef is discontinued - @NHC_Atlantic
Isaac approaching #KeyWest http://t.co/sbedeaWz
Buildings boarded up in downtown #Tampa, FL in preparation of #Isaac's arrival. http://t.co/abxIp4EU
Report: Empire State Building shooting suspect was being evicted from apartment, police source says - @NewYorkPost
Storm surge of 3-5 feet still expected along coast & #TampaBay. Also a risk of tornadoes, heavy rainfall and flooding http://t.co/cLdEQrKv
Isaac likely to drench Cuba, enter Gulf
By Eric Berger
Tropical Storm Isaac bore down on Haiti's southern peninsula early Saturday, threatening a city prone to flooding and dousing other areas of the poor nation still trying to recover from the terrible 2010 earthquake.
The storm swirled past the southern coast of the neighboring Dominican Republic on Friday, dropping heavy rain on that country and on Haiti. Forecasts put it on a path over eastern Cuba and on to the Gulf of Mexico, with it still posing a potential threat to Florida as a hurricane just as the Republicans gather for their national convention.
Forecasters said Isaac could dump as much as eight to 12 inches and even up to 20 inches on Hispaniola, which is shared by Haiti and the Dominican Republic, as well as produce a storm surge of up to 3 feet.
Tropical Storm Isaac slowly strengthened Friday as it neared the Caribbean islands of Hispaniola and Cuba.
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Those islands and the southeastern United States closely watched the storm as it promised to make for a wet weekend and early next week, and possibly bring hurricane-force winds to the northern Gulf of Mexico coast.
Forecasters with the National Hurricane Center predicted Isaac, which had maximum winds to 65 mph on Friday evening, to cross Cuba on Saturday.
U.S. landfall sites
By Tuesday, most computer models predicted a landfall in Alabama or the Florida Panhandle.
Because the storm was not expected to track over the Gulf's warmest waters, forecasters predicted it would not intensify into a major hurricane.
On Friday, the storm already was making its mark in the Caribbean.
In Haiti, the government and international aid groups announced plans to evacuate several thousand people from one of the settlement camps that sprang up in the aftermath of the 2010 earthquake.
Isaac was expected to dump 8 to 12 inches of rain on the island of Hispaniola.
"That kind of rain is going to cause some life-threatening flash floods and mudslides," said Dennis Feltgen, a spokesman for the Hurricane Center in Miami.
Commercial airlines including American Airlines, canceled flights to and from the Dominican Republic, Haiti and Puerto Rico.
United Airlines also said it will waive change fees for customers who want to reschedule flights in the coming days to, from or through destinations in Florida, the Bahamas and the Caribbean, as well as offer full refunds to those who would rather cancel their flights entirely.
Organizers of next week's Republican National Convention in Tampa said they were working closely with state and federal authorities on monitoring the storm as they prepared for the arrival of 70,000 delegates, journalists and protesters. Florida Gov. Rick Scott said there were no plans to cancel the convention.
Oil firms prepare
Oil companies were paying close attention to Isaac's progress and preparing for possible disruptions. In the Gulf, oil companies started evacuating workers from platforms, and one halted production at an offshore facility.
BP said it was in the process of clearing workers from a major offshore platform 150 miles southeast of New Orleans. The company stopped drawing oil and gas at the site, which is capable of producing 250,000 barrels of oil a day.
Shell, Chevron, Apache Corp. and Transocean were evacuating non-essential personnel from offshore facilities, the companies said. Shell also ceased drilling operations at several locations in the Gulf.
How strong Isaac becomes in the Gulf of Mexico will depend upon several factors, including how much interaction with the Cuban landmass disrupts the storm's circulation.
Where it goes in the Gulf will also impact its ability to strengthen, forecasters say. If the storm hugs the Florida coast, it will have less opportunity to become a major storm.
Waters northwest of Cuba would be under the influence of Isaac's easterly winds, and colder water would be churned to the surface.
Of more concern would be a track that is 100 or more miles off the Florida coast, taking the storm over waters with slightly higher heat potential.
Thus, the more time Isaac spends over the open Gulf of Mexico, and the further it remains from the western coast of Florida, the more opportunity it will have to strengthen.
If the track forecast is correct, Houston would not see significant weather effects from the storm. But Isaac would generate a northeasterly flow, bringing warm - but drier - air into Houston next week.
Zain Shauk, Kiah Collier and the Associated Press contributed to this report.