Meantime, Isaac is expected to build strength once the storm enters the Gulf of Mexico. Warm water there made conditions favorable to help fuel the system, which so far has been poorly organized for much of its meandering journey across the Caribbean.

“It may take a little longer to become a hurricane but we’re still forecasting that,”’ said David Zelinsky, a meteorologist at NHC.

Isaac was forecast to be a dangerous Category 2, 105-mph hurricane as it approaches the Gulf Coast early Tuesday but Zelinsky cautioned that it could be stronger. Forecasting intensity is difficult, he said, and the average error, two days out, is a full category, plus or minus.

There was also considerable uncertainty about its path, with anywhere from coastal Louisiana, west of New Orleans, to the northeastern Florida Panhandle a possibility. “Two of our best performing models are at opposite ends of the spectrum,”’ said Zelinsky. “One turns it farther right toward Florida, the other goes left.”

Either way, both scenarios suggested a nasty couple of days in Tampa, scene of this year’s Republican National Convention — no direct hit but a possible storm surge and certainly rain and tropical force winds.

Further south, the Caribbean mostly weathered the storm well with the exception of Haiti, whose Office of Civil Protection confirmed seven deaths from Isaac — up from four deaths reported Saturday night. The deaths included a young man killed in a landslide in DonDon, a town in northern Haiti, and a 10-year-old girl who was killed when her home collapsed north of Port au Prince.

Miami Herald correspondent Jacqueline Charles reported signs of particular devastation in the tourist town of Jacmel, in Haiti’s southern peninsula. Houses were still standing. But people’s crops, their livelihoods, were washed away.

Isaac came to Miami-Dade and Broward counties earlier than anticipated on Sunday with wind gusts of 55 to 60 mph began at about 6:30 a.m., felling trees and blowing debris that have knocked out power to thousands of homes in Miami-Dade and Broward counties.

In addition to strong winds, Isaac is expected to dump four to eight inches of rain on South Florida, potentially flooding already saturated neighborhoods. Rough seas and storm surge also could spill over roads and docks.

In Broward’s coastal cities of Hallandale Beach and Hollywood, where low-lying neighborhoods are prone to flooding, officials continued to hand out sandbags on Sunday morning after filling thousands the day before.

MIAMI, BROWARD SPARED

In Miami-Dade, the threat of Isaac appeared to fizzle almost as soon as it rose.

The county’s Emergency Operations Center launched to Level 1 Sunday morning — its highest alert, with the center fully activated, and all agencies represented.

By noon, after the hurricane watch had been lifted for Miami-Dade, Mayor Carlos Gimenez was calling the county’s storm preparations a good exercise.

“We got prepared for the worst,’’ he said.

County crews will clean up on Monday, when non-essential employees have been given the day off, and it’s back to business on Tuesday, Gimenez said.

Bad weather was to blame for two fatalities on the roads Sunday morning, though no major emergencies were reported.