"However, there is still very large uncertainty in model forecasts of Florence's track beyond day five, making it too soon to determine the exact location, magnitude, and timing of these impacts".
The storm's center was 750 miles southeast of Bermuda at 11 a.m. EDT on Sunday.
Meteorologist Eric Holthaus warned on Twitter that it could become one of the worst storms in United States history.
Florence was forecast to become a Category 3 hurricane by Monday with sustained winds of more than 110 miles per hour.
Think your friends would be interested?More news: Ayanna Pressley ousts longtime Democrat in Massachusetts House primary
More news: Leaked image shows a Nokia smartphone with five camera lenses
More news: Trump calls on Sessions to uncover critic behind article
All indications are that Florence will be an extremely risky Category 4 hurricane while it moves over the western Atlantic toward the southeastern United States.
It is forecast to approach the southeastern USA coast on Thursday.
What we can say is that Florence will not directly impact Southwest Florida. Florence is looking more organized Sunday morning on satellite. But it is now entering a warmer zone, meteorologists said.
Tropical Depression Nine became Tropical Storm Isaac on Saturday afternoon over the eastern tropical Atlantic, the National Hurricane Center said. And it's not likely to weaken before reaching the shores of North and SC and Virginia on Thursday, AccuWeather meteorologist Brett Rossi said.
And another storm, Tropical Storm Isaac spinning farther out in the Atlantic, could also become a hurricane by Monday as it gains strength, forecasters with the National Hurricane Center (NHC) in Miami said in an advisory early Sunday. Yesterday, data pointed to a landfall smack dab in the middle of the Palmetto coastline between Charleston and Myrtle Beach - near where category three monster Hurricane Hugo, roared ashore back in 1989.
Since 1951, at least 67 named storms have passed within 200 nautical miles of where Florence has been travelling.
Some swells generated by the storm have already been reported and can potentially cause unsafe surf conditions and rip currents. It later weakened to a tropical storm after encountering strong wind shear and cooler waters.