Isaac, with winds of 50 miles per hour, had weakened as it tracked westward toward the Caribbean, according to the National Hurricane Center, and may not survive beyond the next few days.
Winds of up to 80mph could hit the county on Monday night, forecasters warned.
As three powerful storms march one by one across the Atlantic Ocean toward the U.S. East Coast and the Caribbean, a fourth is getting ready to roll over the Hawaiian Islands.
Gradual weakening is forecast during the next 48 hours, but Olivia is expected to remain a tropical storm as it moves over the main Hawaiian Islands.
At noon, The National Hurricane Center issued hurricane watches for Dominica, Guadeloupe, and Martinique while a tropical storm watch was issued for Antigua and Montserrat.
Over in the Pacific, this storm is still moving toward Hawaii, where tropical storm warnings and watches have been issued, the hurricane center said.
Tropical Storm Isaac was edging towards the Leeward Islands Thursday morning on a path that could bring the storm into the Cayman Islands area.More news: Inbox, Google’s playground for email innovation, is going bye-bye
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The official track has Florence hovering off the southern North Carolina coast from Thursday night until landfall Saturday morning or so, then veering south through SC and Georgia into Monday.
The storm is likely to die out by Wednesday. Florence is expected to slow down as it approaches the Carolina coast over the next several days.
"The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves", the NHC said.
Britain is bracing itself for strong winds and heavy rain as Hurricane Helene makes its way across the Atlantic.
The Portuguese weather service said that wind gusts of up to 74 mph are possible by the weekend in the Azores, an island chain about 850 miles west of Portugal.
Although Florence was downgraded from Category 4 status, it is still considered an extremely unsafe storm with maximum sustained winds near 125 miles per hour.