And it would be the first major hurricane (Category 3 or higher) to hit the East Coast since Jeanne, which struck Florida in 2004.
USA residents have been warned to prepare for the hurricane's impact.
The storm's potential path also includes half a dozen nuclear power plants, pits holding coal-ash and other industrial waste, and numerous hog farms that store animal waste in massive open-air lagoons. South Carolina Gov. Henry McMaster also suspended his campaign and asked President Donald Trump for a federal emergency declaration.
Storms increase in frequency and intensity by mid-August and into September as temperatures in the Atlantic climb to their highest levels, Javaheri said. A few models depict the storm brushing the coast.
Some computer models predicted Wilmington area south of the Outer Banks, but it was still too early to predict an exact path for the storm.
The major hurricane is expected to travel between Bermuda and the Bahamas on Tuesday and Wednesday before reaching the USA on Thursday.
Residents as far north as Virginia were warned that Florence posed an increasing risk of life-threatening coastal storm surge, as well as flooding from heavy rainfall inland should the slow-moving storm system stall over the Southeast. People in coastal communities are taking all precautions.
No hurricane has made landfall as a Category 5 in this region on record.
As of the 5 PM advisory from the National Hurricane Center, Florence remains a very powerful category 4 hurricane. Hugo in 1989 was the one before that and was a Category 4 at landfall.
"I'll see by Wednesday how that goes - we got over 48 hours before that happens", Cesal said.
Camp Lejeune says in a statement that it's urging personnel to prepare now, and will open shelters on the base if necessary. The island state is still recovering from Hurricane Lane, which brought flooding rains to many areas last month.
The NHC predicts it could become a major hurricane by Monday and remain that way through Thursday.
At 5 a.m. EDT, the hurricane center said Florence's maximum sustained winds were estimated to be 70 miles per hour (110 kph).
At this point, it appears like it will be moving into the Central Caribbean by the middle to end of the week as Hurricane Isaac.
Tropical storm force winds extend outward up to 140 miles from the storm's center.
The other storms Tropical Storm Isaac and Tropical Storm Helene are both expected to become hurricanes Sunday or Monday.
The storm's sustained winds reached 121 km/h, just over the threshold for a hurricane, on Sunday morning as it was moving across the Atlantic, about 1,210 km/h southeast of Bermuda.