Isaac, which became a tropical storm Saturday afternoon, was intensifying and expected to become a hurricane, the National Hurricane Center said Sunday. It is about 1,230 miles east of the Windward Islands, moving west at 14 mph. It is expected to continue strengthening over the next day or two, then weaken again by the middle of the week as it approaches the Lesser Antilles.
"With this order government agencies will begin to mobilize in anticipation of a hurricane", McMaster said.
As of 11 a.m., Florence had a maximum wind speed of 115 miles per hour, bringing it to major hurricane status.
"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.
"While it is too soon to determine the exact timing, location and magnitude of these impacts, interest at the coast and inland from SC into the mid-Atlantic region should closely monitor the progress of Florence", said a NOAA statement.
Florence was producing large swells expected to reach from the northern Caribbean to the southern coasts of Canada´s Maritime provinces.
Maximum sustained winds have increased to near 75 miles per hour (120 km/h) with higher gusts.
A third storm, Hurricane Helene, was spinning in the Atlantic off West Africa's Cabo Verde Islands with 75-mph (121-kph) winds on Sunday, but did not appear to pose an immediate threat to land.
Tropical Storm or Hurricane Watches may be required for portions of the Hawaiian Islands later today or tonight.
For Central Florida, it is becoming likely that Florence will bring significant wave activity in the Atlantic, along with a unsafe high rip current threat and possible coastal erosion. It has only a 10 percent chance of forming into a tropical storm.
"Review your emergency plans and gather your supplies now", North Carolina Governor Roy Cooper said in a statement on Sunday.
The National Hurricane Center announced Sunday morning that Florence escalated into a hurricane with winds reaching 75mph as it swirls across the Atlantic.