At 0300 GMT Issac was about 1,305 miles east of the Windward Islands - a region still recovering from last year´s powerful Hurricane Maria - with winds of 75 miles per hour. It says the hurricane should approach the US coast on Thursday.
By 11 p.m. Sunday, Florence was moving across the Atlantic Ocean at about 7 miles per hour, and it was almost a Category 2 hurricane, with peak winds of 90 miles per hour.
The center of the hurricane was forecast to move between Bermuda and the Bahamas on Tuesday and Wednesday and approach the southeastern coast of the United States on Thursday as a Category 3 storm or higher, according to the hurricane center.
As of 11 p.m. EDT, Florence was centered about 685 miles (1,100 kilometers) southeast of Bermuda, moving west at 7 mph (11 kmh).
The Navy said all ships in Virginia's coastal Hampton Roads area were preparing to leave port for open seas Monday. These can range from high winds and storm surge in coastal Virginia to significant flooding both along the coast and in rivers and streams in the western part of the state. Hurricane Florence has the potential to provide us with multiple inches of rain, but we're continuing to watch its track closely to better determine how much rain we could get.
The former is expected to weaken by the time it hits the Caribbean, and the latter is not expected to pose a threat to land.
Henry McMaster declared a state of emergency Saturday to give his state time to prepare for the possible arrival of a hurricane.More news: Fortnite Monopoly: Tabletop version of game released in time for Christmas
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"All indications are that Florence will be an extremely unsafe Category 4 hurricane while it moves over the western Atlantic toward the southeastern United States", the hurricane center said.
The latest track for Florence still shows it making landfall sometime Thursday afternoon along the Carolina coast as a category 4. Florida-based Carnival Cruise Line re-routed its cruise ships.
The 2018 hurricane season blew into high gear on Sunday.
Officials say heavy rainfall on the islands could produce life-threatening flash floods.
Officials in North Carolina are already bracing for impact. The governors urged residents to assemble emergency kits including food, water, medications, pet supplies and important documents that might be needed if evacuations are necessary. The state's emergency management agency said it's "preparing for the possibility of a large-scale disaster".
Rapidly intensifying Hurricane Florence could strike a direct and risky blow anywhere from the Carolinas to the Mid-Atlantic region later this week.