Forecasters expect Tropical Storm Florence to become a "major hurricane" Monday as it continues to approach the southeastern U.S. East Coast.
Forecasters at the NHC said Florence would continue to strengthen and "is expected to remain an extremely risky major hurricane through Thursday".
Florence rapidly strengthened into a potentially catastrophic Category 4 hurricane Monday as it closed in on North and SC, carrying winds and water that could wreak havoc over a wide stretch of the eastern United States later this week.
Hurricane Helene, was spinning in the Atlantic off West Africa's Cabo Verde Islands with 85-mph (140-kph) winds on Sunday, but did not appear to pose an immediate threat to land.
The center of Florence was forecast to sweep between Bermuda and the Bahamas on Tuesday and Wednesday before making its assault on the US coast.
Residents as far north as Virginia were warned that Florence could bring a life-threatening coastal storm surge, as well as inland flooding from "prolonged and exceptionally heavy rainfall", the NHC said.
According to an 11 a.m. update from the National Hurricane Center, Hurricane Florence's maximum sustained winds have intensified to 75 miles per hour.
The National Hurricane Center reclassified Florence as a hurricane in its 11 a.m. report while also issuing advisories in the Atlantic for two other tropical storms expected to become hurricanes: Isaac and Helene.
This enhanced satellite image made available by NOAA shows Tropical Storm Florence, third from right, in the Atlantic Ocean on Saturday, Sept. 8, 2018 at 3 p.m. EDT.
Met Service said neither of the storms are a threat to Jamaica.
Computer models agree Florence is on track to hit the Carolinas.
"While it's still too early to know the storm's path, we know we have to be prepared", he said in a written statement.
A hurricane hunter plane found Florence strengthening quickly after it became a hurricane Sunday.
Officials in North Carolina were already bracing for impact. "Accordingly, I am declaring a state of emergency so that we can begin to prepare state assets, and I encourage Virginians to monitor forecasts and make their own preparations now". It is about 1,400 miles east of South Florida. The Navy planned to send ships from the Hampton Roads area of Virginia out to sea.