Florence is forecast to become a major hurricane by Monday as it continues to approach the U.S. East Coast, the U.S. National Hurricane Center (NHC) said late Saturday.
The tropical storm is centered about 1,270 km southeast of Bermuda and moving west at 9 km per hour, the NHC said.
"Florence is expected to become a hurricane at any time soon and rapid intensification is likely to begin on Sunday," it said.
Although Florence's exact path is unclear, North Carolina Governor Roy Cooper issued an emergency alert on Friday to get emergency operations rolling. South Carolina followed suit on Saturday.
"Interests along the U.S. East Coast, particularly Florida through North Carolina, should closely monitor the progress of Florence, ensure they have their hurricane plan in place and follow any advice given by local officials," the NHC said.
It also warned that swells generated by Florence are affecting Bermuda and are beginning to reach portions of the East Coast.
"These swells are likely to cause life-threatening surf and rip current conditions," it added.
Florence, the first major hurricane of the 2018 Atlantic hurricane season, was upgraded to a Category 4 hurricane Thursday, packing maximum sustained winds of 215 km per hour.
Besides Florence, two other storms, Isaac and Helene, are churning in the Atlantic basin.
Tropical Storm Isaac formed on Saturday and was located 2,540 km east of the Windward Islands, whose major islands are St. Lucia, Dominica, Martinique and Grenada. It had maximum sustained winds of 85 km per hour on Saturday and a westward motion with an increase in forward speed is expected during the next few days. .
Helene, which formed Friday night, is expected to bring tropical storm conditions to the Cabo Verde islands, off the coast of Africa, on Sunday. It could cause rain, with up to six inches in isolated spots, through Sunday. Flash floods are possible, the NHC said.
Forecasters said the hurricane season will reach its peak on Sept. 10-11.
They are expecting nine to 13 named storms with winds of 60 km per hour or higher, of which four to seven will strengthen into hurricanes.
