"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".
"I don't think we're quite done yet", he said, "but certainly as far as September goes, this is the big week".
Forecasters are also keeping an eye on two storms gathering behind Florence.
In Charleston, South Carolina, along the coast, city officials offered sandbags to residents.
Florence's top wind speeds were still hovering at about 130 miles per hour on Tuesday, making Florence a Category 4 hurricane.
The South Carolina Emergency Management Division tweeted Sunday that officials there are "preparing for the possibility of a large-scale disaster". "They're coming in and buying water and plates, and that's about all they're buying".
"So when this is all said and done this is probably going to be the costliest storm in the history of the Carolinas because not only are you dealing with a major hurricane hit, but you're dealing with flooding of biblical proportions", Bastardi explains.
The Navy said Saturday that it may be necessary to send ships in the Norfolk, Virginia, area out to sea because of the coming storm.
Still, there's a chance it could be pushed farther north and strike along the mid-Atlantic or New England coast, threatening to make landfall between Virginia and MA.
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. And it would be the first major hurricane (Category 3 or higher) to hit the East Coast since Jeanne, which struck Florida in 2004.
U.S. President Donald Trump, whose administration was criticized as being slow to respond to Hurricane Maria in Puerto Rico past year, canceled a political rally planned for Friday in Jackson, Mississippi, over safety concerns related to Florence, his campaign said. Then, the storm was expected to weaken a bit as it encounters storm-hindering wind shear, or fluctuations of wind speeds in the atmosphere.
Hurricane Florence appears to be taking aim at the largest U.S. Marine Corps base on the East Coast. Florence is expected to remain an extremely unsafe major hurricane through Thursday. Jeff Masters, co-founder of the Weather Underground service, says airplanes gathering weather information began flying into Florence on Saturday, which should provide data that will lead to a major boost in the reliability of models on Sunday.
Hurricane Isaac is holding steady in strength over the Atlantic.
"None of the guidance suggest that Florence has peaked in intensity, and this is supported by a continuation of a low-shear environment, and even warmer waters over he next 36 hours".
Hurricane-force winds extend outward up to 10 miles (20kilometers) from the center and tropical-storm-force winds extend outward up to 45 miles (75 kilometers). Isaac, which was moving toward the lesser Antilles in the Caribbean Sea, could bring heavy rain and become a hurricane overnight, CNN meteorologist Tom Sater said.
Rapidly intensifying Hurricane Florence could strike a direct and unsafe blow anywhere from the Carolinas to the Mid-Atlantic region later this week.
As of 5 a.m. EDT, Florence was centered about 625 miles (1,005 kilometers) southeast of Bermuda, moving west at 9 mph (15 kph).
These swells, already affecting Bermuda, "are likely to cause life-threatening surf and rip current conditions", the NHC warned.