"On the forecast track, the center of Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas Tuesday and Wednesday, and approach the coast of SC or North Carolina on Thursday", the NHC said. Catastrophic floods could follow if the storm stalls inland, it said.
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. More than one million people living along the Carolina-Virginia coast are under mandatory evacuation orders.
Even Wilmington, North Carolina - a coastal city accustomed to severe weather - is bracing for an unusually brutal impact.
Life-threatening storm surges along portions of the coastlines of South Carolina, North Carolina and Virginia.
"People need to leave now before they can't", North Carolina Gov. Roy Cooper said.
Liz Browning Fox was planning to ride out the storm on the Outer Banks, defying evacuation orders. "Don't bet your life on riding out a monster".
If Florence slows to a crawl just off the coast, it could bring torrential rains to the Appalachian mountains and as far away as West Virginia, causing flash floods, mudslides and other risky conditions. Also, looking like a direct hit on North Carolina, South Carolina and Virginia.
Isolated tornadoes are also possible Thursday and Friday. "A lot of local people are staying", she said of the island, which is reachable only by ferry or plane. Even scarier: It could get more intense as it gets closer to the Carolinas.
Now a Category 4 hurricane packing 140 mile-per-hour winds, Florence is due to make landfall somewhere in the Carolinas late Friday or Saturday.
"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)".
President Donald Trump declared states of emergency for North and SC and Virginia, opening the way for federal aid.
Based on the current forecast, Florence could cause storm surges of 3 to 6 feet above ground level in areas along the coast and near the Albemarle Sound, the center said.
Virginia, home to major government and military facilities, declared a state of emergency and 245,000 coastal residents there were ordered to evacuate by 8:00 am Tuesday including from the Eastern Shore, another popular beachfront getaway destination. Other counties are evacuating low lying and flood prone areas. A hospital in Hampton, Virginia, was transferring patients to safer places.
As South Carolina residents and emergency responders prepare for Hurricane Florence, the South Carolina National Guard has mobilized about 1,600 soldiers and airmen to prepare, respond and participate in advance of the major hurricane projected to make landfall near the Carolinas.
"This is one of the worst storms to hit the East Coast in many years", US President Donald Trump tweeted Monday evening.
"We are sparing no expense".
Duke Energy spokesman Ryan Mosier said operators would begin shutting down nuclear plants at least two hours before hurricane-force winds arrive. North Carolina is the top USA turkey producer, ranks third for chicken and is home to more hogs than any state other than Iowa, government data show. Get to the grocery store. "What is flooding going to do to our home, our city?" That would make Florence the costliest storm ever to hit the U.S.in terms of property loss.
"Never have we seen quite this type of a storm approach us".
"If we get more than 25 inches of rain, then we'll start to be concerned", he said.