(Adds details from latest NHC advisory, U.S. Navy)
By Joseph Ax
Sept 8 (Reuters) - Tropical Storm Florence was expected to strengthen back into a hurricane by Saturday night and then rapidly intensify on Sunday as it headed for a possible landfall on the U.S. East Coast next week.
Florence was spinning across the Atlantic Ocean about 810 miles (1,305 km) southeast of Bermuda on Saturday afternoon, moving west at around 5 miles per hour (7 kph), according to the Miami-based National Hurricane Center (NHC).
Data from an official Hurricane Hunter aircraft showed its maximum sustained winds had risen to near 70 mph (110 kph), from 65 mph earlier on Saturday, with stronger gusts, the NHC said in its latest advisory.
The storm was at hurricane strength earlier this week before weakening to a tropical storm. It is expected to intensify rapidly on Sunday and could become a major hurricane by Monday with sustained wind speeds of at least 111 miles per hour (179 km per hour), forecasters said.
Its center will move between Bermuda and the Bahamas on Tuesday and Wednesday, and approach the southeastern U.S. coast on Thursday, the NHC said.
Swells generated by Florence were affecting Bermuda and starting to reach parts of the U.S. East Coast. They were likely to cause life-threatening surf and rip current conditions, the NHC said.
Florence's precise path remained uncertain on Saturday, but the NHC said the "risk of direct impact" somewhere between Florida and North Carolina was increasing.
The governors of North Carolina and South Carolina declared states of emergency and urged people to prepare for Florence's arrival. Authorities in Florida said they were closely monitoring the storm.
"We are now in the peak of hurricane season - disaster preparedness should be a major priority for your family," Florida Governor Rick Scott wrote on Twitter.
The U.S. military was also preparing: the Navy on Saturday told all its ships in the Hampton Roads, Virginia - home to more than a fifth of the fleet - to prepare for an order to take to sea to avoid storm damage from any storm surge or destructive winds.
"Our ships can better weather storms of this magnitude when they are underway," U.S. Fleet Forces Commander Admiral Christopher Grady said in a statement. (Reporting by Joseph Ax in New York; Editing by Paul Simao and Grant McCool)
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