The U.S. National Weather Service said Saturday there was an increasing risk that Tropical Storm Florence would make a "direct impact" on the U.S. East Coast as a major hurricane.
National Hurricane Center forecasters said the storm, now southeast of Bermuda, was expected to intensify rapidly Sunday and become a major hurricane by Tuesday. The Washington Post said the storm could reach Category 4 status, one notch below the top level of intensity on the U.S. storm classification system, and remain that way until Thursday.
North Carolina Governor Roy Cooper on Friday declared a state of emergency and encouraged residents near the coast to prepare. Authorities in Florida and South Carolina said they were keeping an eye on the storm.
Florence intensified to hurricane strength and weakened again in the past week, while whirling over the open water of the Atlantic Ocean.
Florence could affect eastern U.S. coastal areas far to the north of the impact area, producing dangerous riptides and coastal flooding on the New Jersey shore, forecasters said.
Saturday afternoon, the storm packed winds of 110 kilometers per hour (70 mph). It was located about 1,305 kilometers (810 miles) southeast of the island of Bermuda and moving west at 7 kph (5 mph).
Hurricane experts said there was still a chance the storm would remain over water near the U.S. coastline and eventually move back out to sea to die out.
With the Atlantic hurricane season at its height, the next named storm, Tropical Storm Helene, has already formed near the coast of Africa, moving west across the Atlantic toward North America.