PORT-AU-PRINCE Tropical Storm Isaac strengthened on Friday as its lashing rains took aim at flood-prone Haiti, but it was not expected to become a hurricane until it barreled into the Gulf of Mexico early next week.
On its current path, forecasters said Isaac would hit Cuba and the southern tip of Florida before making landfall anywhere from the Florida Panhandle in the northwestern part of the state to Alabama and as far west as New Orleans.
Forecasters put the entire coast of south Florida under tropical storm watch as of 5 p.m. EDT (2100 GMT) on Friday.
But the biggest immediate concern was heavily deforested Haiti, where the U.S. National Hurricane Center (NHC) said the full force of the storm was expected to be felt by Friday evening.
Isaac comes as Republicans gather in Tampa, on Florida's central Gulf coast, for Monday's start of their national convention ahead of the November presidential election.
The convention is still due to proceed as planned but Gulf of Mexico operators began shutting down offshore oil and gas rigs on Friday ahead of the storm.
On Friday afternoon torrential rains began falling on the Dominican Republic, which shares the island of Hispaniola with Haiti.
Life-threatening flash-floods and mudslides, which are common in Haiti, could add to the misery of about 350,000 people still living in tent cities and camps after the January 2010 earthquake that killed more than 250,000 people.
The NHC said Isaac was centered about 100 milessouth-southeast of the seaside Haitian capital Port-au-Prince late Friday afternoon, packing top sustained winds of 65 miles per hour.
The storm was moving northwest at 16 mph and it was expected to dump between 8 and 12 inches of rain over parts of Haiti, with total accumulations of up to 20 inches in some areas.
The storm prompted Haitian President Michel Martelly to announce on Thursday night that he was cancelling a planned trip to Japan.
"I known your worries," Martelly said in an address to the nation. "I also know we're a strong people."
About 3,000 volunteers from the government's Civil Protection office have been dispatched across Haiti, to warn people about flood and landslide risks, and about 1,250 shelters -- schools, churches or other community buildings -- have opened their doors to house people seeking refuge from the storm.
But Red Cross officials said the number of shelters could be grossly inadequate and Prime Minister Laurent Lamothe acknowledged Haiti had "limited means" to ensure public safety.
Red Cross and International Organization for Migration representatives joined Martelly and other government officials in trying to evacuate 8,000 people, including 2,500 sick and disabled, from 18 tent camps in low-lying coastal areas of Port-au-Prince on Friday.
"NOTHING WE CAN DO"
But Bradley Mellicker, head of disaster management for the IOM, said many people refused to abandon their makeshift homes, apparently due to fears of theft.
"There's a lot of people who are resisting because they are scared of losing what little they have now," Mellicker said.
Many Haitians, most of whom scrape by on less than $1 per day, consider disaster an inevitable part of life in the poorest country in the Americas.
"We live under tents. If there's too much rain and wind, water comes in. There's nothing we can do," said Nicholas Absolouis, an unemployed 34-year-old mechanic at one camp for homeless people on the northern edge of the chaotic capital.
"If he's coming, he's already on the way," added Juliette Jean-Baptiste, 26, another resident of the camp. "Our tents leak already."
"We're not worried," said Olivier Oge, who was playing dominoes with friends as wind kicked up the tarp over their heads in Tapis Rouge, a sprawling camp for quake survivors near a ravine on the outskirts of Port-au-Prince.
When Isaac comes, "we'll still be playing until the pieces fly away," he said.
"The next 24 hours will be critical for the population of Haiti," said France Hurtubise of the International Federation of Red Cross and Red Crescent Societies in Haiti. "There are still too many people living in the camps. There's a good chance that those might be destroyed with the passage of the cyclone."
Flooding could also help rekindle a cholera epidemic in Haiti, which has killed more than 7,500 people since the disease first appeared in October 2010, foreign aid workers said.
Isaac has drawn especially close scrutiny because of the Republican Party's convention, a four-day meeting during which former Massachusetts Governor Mitt Romney will receive the party's presidential nomination.
Party officials insist the convention will go ahead, even if they have to alter the schedule. But NHC meteorologist Rick Danielson said Tampa could potentially be hit by coastal flooding and driving winds or rain.
"There is still a full range of possible impacts on Tampa at this point," he said.
The NHC is no longer forecasting Isaac to rev up to hurricane force until Monday night or early Tuesday, long after it crosses Haiti and Cuba.
Danielson said it was very hard to project intensity before Isaac passes over mountainous Cuba on Saturday and Sunday and enters the Florida Straits. But the Florida Keys, the island chain off the southernmost part of the state, were definitely in harm's way.
Florida has not been hit by a major hurricane since 2005, and forecasts showed Isaac was not expected to strengthen beyond weak Category 1, with top sustained wind speeds of about 85 mph.
(Writing by Tom Brown; Additional reporting by David Adams in Miami, Manuel Jimenez in the Dominican Republic and Kristen Hays in Houston; Editing by Xavier Briand)