Top sustained winds are now about 65 miles per hour (100 kph) and the storm is moving to the west-southwest at 5 miles per hour (7 kph) - a track that is expected to continue through early Saturday.
Isaac is expected to be near hurricane strength when it moves through the Lesser Antilles, with some weakening forecast afterward on Friday and Saturday.
"We do not anticipate experiencing any tropical storm or hurricane force winds, but we could experience rain and will be placed under a flash flood watch", said Governor Kenneth Mapp in a release issued late Thursday.
The mammoth waves were spotted early Wednesday in the storm's northeast quadrant, said the NHC's Tropical Analysis and Forecast Branch, which has been documenting Florence's waves all week. As a result, the water is pushed onto the shore, above the normal sea level, because the winds are immensely strong.
In North Carolina, a storm-surge pushed floodwater miles inland.
Tropical storm warnings were issued for Martinique, Dominica, and Guadeloupe.
Observation stations at the coast recorded wind speeds of more than 80 miles per hour, the advisory said.
Prisoners were affected, too. "We should also continue to keep our brothers and sisters located in the Carolinas in our thoughts and prayers as Hurricane Florence approaches their area".
Federal states of emergency have been declared in all three states, and collectively about 1.5 million people have fled the coast under mandatory evacuation orders.
The hurricane center is giving the system a 50 percent chance of becoming a tropical depression or storm within the next five days.
Spanish moss waved in the trees as the winds picked up in Wilmington, and floating docks bounced atop swells at Morehead City. Rain will continue through Sunday, dumping feet of water over a wide area.
Coastal towns in the Carolinas were largely empty, and schools and businesses closed as far south as Georgia.
Earlier forecasts showed that the storm was slated to directly hit around North and SC.
The storm now appears to be on track to enter the Gulf of Mexico as a tropical wave early next week, meaning South Florida will hardly notice a thing.
In the latest information from the National Hurricane Center, Hurricane Florence has been downgraded to a Category 2 event. "And you don't need power to sling booze", owner Eli Ellsworth said. "We have a safe basement and generator that comes on automatically".
That's almost double the wave heights documented on Tuesday, when the NHC said satellites had observed "an expansive area of wave heights 12 feet or greater" circulating around Hurricane Florence and peak waves of 45 feet near its center. Tropical Storm Joyce is almost 1,100 miles west-southwest of the Azores.