Hurricane conditions are possible within the hurricane watch area - Guadeloupe, Martinique and Dominica - by Thursday morning, with tropical storm conditions possible early Thursday in both the tropical storm watch area - Antigua, St Kitts and Nevis, and Montserrat - and the hurricane watch areas, the NHC added.
According to the National Hurricane Center's 11 p.m. Tuesday update, Isaac has weakened somewhat in the previous 24 hours and is now expected to enter the Caribbean Thursday evening as a tropical storm, rather than a hurricane.
An extremely powerful hurricane is forecast to make landfall in the southern part of the United States later this week. "The rainfall has been and continues to be a very substantial threat over the entire area".
People walk past storm shuttered buildings on the Myrtle Beach Boardwalk in Myrtle Beach.
There have been warnings that any flooding of hog manure pits, coal ash dumps and other industrial sites could have a lasting effect on communities, with tainted water possibly washing into homes and drinking supplies.More news: Hurricane Florence approaching Carolina coast, will move west this weekend
President Donald Trump at a briefing on Hurricane Florence at the White House yesterday.
The NHC measured wave heights of up to 83 feet - the equivalent of a seven-story building - as Florence churned in the Atlantic Ocean on Wednesday.
Up to 1.7 million people are under voluntary or mandatory evacuation orders, and coastal residents were frantically boarding up homes and businesses and hitting the road on Wednesday as the storm approached. "We are ready. We're as ready as anybody's ever been". Protection of life is the absolute highest priority and that's what we are doing.
However, forecasters say the storm's biggest threat is how much rain it is expected to produce.More news: Matthew Perry has been hospitalized for 3 months
Jeff Byard, who is the FEMA associate administrator for the Office of Response and Recovery, said that Florence is "a very unsafe storm", Fox News reported.
Duke Energy Corp expected between 25 percent and 75 percent of its 4 million customers would lose power in the Carolinas.
The damage occurred even though Sandy spun ashore as the equivalent of only a Category 1 hurricane, with winds of about 80 miles per hour, and was downgraded below hurricane status shortly thereafter. "I encourage Georgians to be prepared for the inland effects of the storm as well as the ensuing storm surge in coastal areas".
A state of emergency has been declared in 5 states including North and SC, as well as the capital, Washington D.C.
In Wilmington, Solange Iliou Thompson closed down her restaurant, Indochine, because all of her employees had left the city.More news: Death toll rises to 7 as Florence pours on the rain