"These conditions are expected to lead to significant strengthening during the next 12 to 24 hours, and Florence is forecast to be a very powerful major hurricane on its approach to the southeastern United States", the NHC said in a statement this morning.
In its 11 p.m. Sunday advisory, the National Hurricane Center upgraded Tropical Storm Isaac to a Category 1 hurricane, with winds of almost 75 miles per hour.
As of early Monday, the storm was getting stronger, with maximum sustained winds of 105 miles per hour.
"Swells generated by Florence are affecting Bermuda and portions of the U.S. East Coast", the it added.
The state of SC is preparing for some level of impact from Hurricane Florence, Gov. Henry McMaster announced Sunday.
Mr Cooper said he had asked Mr Trump to declare a federal state of emergency for North Carolina. More evacuation orders are likely to come. Florence "is expected to remain an extremely risky major hurricane through Thursday", the NHC said in a statement. The early projections show a 20-30"+ rainfall forecast, winds over 110 miles per hour, and a major storm surge!"
Hurricane Isaac, with winds of 75 mph, is located roughly 1,300 miles east of the Windward Islands and is expected to continue moving westward, across the lesser Antilles and into the eastern Caribbean Sea, by Wednesday night or Thursday.
Even if a direct blow is avoided, if Hurricane Florence slows or stalls near the shore it could cause devastating inland flooding, by unloading a foot or two of rain.
Both Tropical Storm Isaac and Tropical Storm Helene are expected to reach hurricane strength but neither is considered a threat to Bermuda.
Florence is anticipated to possibly develop into a Category 5 an extremely unsafe major hurricane.
Though no coastal advisories are yet in place, the update said that those warnings would likely be forthcoming. Latest forecasts have Florence making landfall in the vicinity of Wilmington, North Carolina Thursday evening/night.
At this statistical height of the Atlantic hurricane season, Florence was being trailed on east-to-west paths by Hurricane Helene near the Cabo Verde islands, and Tropical Storm Isaac. Given the way Florence intensified before it seems either are possible over the coming few days.
In North Carolina, some schools had already canceled classes for the week by early Monday, as the state braced for what would be only its second brush with a Category 4 hurricane since record-keeping began in the 1800s - the other was 1954's Hazel.