"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 centre said.
The third hurricane in the Atlantic, Hurricane Florence, could pose a danger to parts of the U.S.
For Central Florida, it is becoming likely that Florence will bring significant wave activity in the Atlantic, along with a risky high rip current threat and possible coastal erosion.
Issac is expected to gain strength in the next days, but then weaken by the middle of the week when it approaches the Caribbean.
While there is potential for tropical storm force winds in the Valley, the biggest threat by far here would be flooding.
As of Sunday afternoon, hurricane-force winds extended outward up to 25 miles from Florence's center, while tropical storm winds extended up to 125 miles.More news: Tropical Storm Helene forms in eastern Atlantic
"As we have seen with hurricanes in most recent years, such as Lane in Hawaii earlier this summer and Harvey last year in Texas, feet of rain can fall when these tropical storms stall", Sosnowski said.
Elsewhere in the tropics, officials say Tropical Storm Helene is approaching islands off the western coast of Africa.
But forecasters said that the risk of "direct impacts continues to increase" and that a huge coastal area from northern Florida to North Carolina should prepare for a major hit.
All government services will remain in operation today as Hurricane Florence passes to the south of the island.
"Pretend, assume, presume that a major hurricane is going to hit right smack dab in the middle of SC and is going to go way inshore", McMaster said at a press conference.
There are now no coastal watches or warnings in effect.
"Review your emergency plans and gather your supplies now", North Carolina Governor Roy Cooper said in a statement on Sunday.
The NWS Central Pacific Hurricane Center inHonolulu issued an update on Hurricane Olivia on Sunday, Sept. 9, 2018.