Florence may grow to a Category 5 hurricane by the time it hits the North Carolina coast early Friday morning.
The center of the storm is expected to move between Bermuda and the Bahamas on Tuesday and Wednesday and will approach the Carolinas by Thursday. A Storm Surge watch means the possibility of "life-threatening inundation from rising water moving inland" over the next 48 hours.
A warm ocean gives hurricanes their fuel, and Florence is moving over an area with water temperatures nearing 85 degrees (30 Celsius), hurricane specialist Eric Blake wrote.
The U.S. Coast Guard closed ports in Wilmington and Morehead City, North Carolina and Hampton Roads, Virginia to inbound vessels greater than 500 tons and was requiring vessels of that size to leave if they did not have permission to be in the ports.
According to the Saffir-Simpson Hurricane Wind Scale, people caught in a Category 4 storm can expect to see "catastrophic damage".
Authorities are warning about Florence's potential to unleash prolonged torrential rains and life-threatening floods, down trees, knock out electricity and submerge entire communities - especially if it slows to a crawl and lingers inland for several days, just as Hurricane Harvey stalled over Texas in 2017. It was located farther north in the Atlantic than any other storm to ever hit the Carolinas, so what we're forecasting is unprecedented.
"There's 25% more people living between Charleston (South Carolina) and Morehead City (North Carolina) than there were when Hugo was making landfall", CNN meteorologist Myers said. "A lot of local people are staying", she said of the island, which is reachable only by ferry or plane.
One trusted computer model, the European simulation, predicted more than 115cm in parts of North Carolina.
If the latest forecast holds, Florence will strike farther north on the East Coast than any other Category 4 hurricane in history.
"Hurricane-force winds extend outward up to 40 miles (65 km) from the center and tropical-storm-force winds extend outward up to 150 miles (240 km)".
A hurricane watch is now in effect for Edisto Beach South Carolina to the North Carolina-Virginia border as well as Albemarle and Pamlico Sounds, including the Neuse and Pamlico rivers, the NHC said.
There was little change in Florence's track during the 11 a.m. forecast from the National Hurricane Center.
Power companies warned residents may be without power for days or weeks.
Utilities deployed crews and gear in advance, with workers en route to the region from at least 15 states, according to trade group, the Edison Electric Institute. "The threat will be inland, so I'm afraid, based on my experience at FEMA, that the public is probably not as prepared as everybody would like", said Craig Fugate, former director of the Federal Emergency Management Agency. One power station, Duke Energy Corp's Brunswick plant, the closest to the area where landfall is forecast, faced a likely shutdown as a precaution.
A Category 4 Hurricane is a force to be reckoned with. A hospital in Hampton, Virginia, was transferring patients to safer places.
Florence could hit the Carolinas harder than any hurricane since Hazel packed 130 miles per hour winds in 1954.
"We are sparing no expense". Some 3,000 people died in the aftermath of that storm.
"The governor said that North Carolina is the bull's eye of this hurricane", Larry Wooten, president of the North Carolina Farm Bureau, said in an interview.
Smithfield Foods Inc [SFII.UL] said it would shut down the world's largest hog-slaughtering facility in Tar Heel, North Carolina, on Thursday and Friday due to the hurricane. Get to the grocery store.