The Miami-based centre defines a major hurricane as one with a wind speed greater than 177 km/h.
The Navy said all ships in Virginia's coastal Hampton Roads area were preparing to leave port for open seas Monday. We will closely be monitoring its track in the coming days.
The storm will be crashing through a region already sodden from heavy rains, making flooding a major concern.
"We are entering the peak of hurricane season and we know well the unpredictability and power of these storms", Cooper said.
Virginia and North Carolina also declared states of emergency in preparation for Florence. McMaster on Sunday predicted Florence will likely deliver "a strong hit on SC", though he cautioned that it's still uncertain how bad the Palmetto State will be affected.
Delaware Gov. John Carney says state officials are closely monitoring the approach of Hurricane Florence, which is heading toward the US for what forecasters said could be a direct hit on the Southeast toward the end of the week.
In Charleston, South Carolina, along the coast, city officials offered sandbags to residents.
The Met Office said Trinidad and Tobagi is not under any tropical storm watch or warning at this time.
"Action today can avoid losses due to Florence", he said. Some forecast models have shown Florence slamming into land by late next week, while others indicated the storm would curve away from shore.
Tropical Storm Isaac is set to become a hurricane late on Sunday as it gathers in strength and makes its way towards the Caribbean. The state's emergency management agency said it is "preparing for the possibility of a large-scale disaster". 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 National Hurricane Center said Florence had re-strengthened into a Category 1 hurricane Sunday as it was located about 710 miles (1,142 kilometers) southeast of Bermuda.
Spaghetti models are in a general agreement of landfall on the U.S. East Coast somewhere along SC and North Carolina.