MIAMI • A rapidly strengthening Hurricane Florence chugged across the Atlantic on Sunday toward a possible direct hit on the U.S. Southeast late this week, triggering warnings to people up and down the coast to get their emergency kits ready, map out escape routes and fill sandbags.

Red flags flying on beaches warned swimmers to stay out of waters already roiled by the distant storm, and cruise ships and Navy vessels were being steered out of harm’s way. People rushed to buy bottled water, plywood and other supplies. Florence crossed the 74 mph threshold from tropical storm to hurricane Sunday morning, and by evening its winds were up to 85 mph . As of 5 p.m., it was centered about 720 miles southeast of Bermuda, moving west at 7 mph .

Drawing energy from the warm water, it could be a fearsome Category 4 with winds of 130 mph or more by Tuesday, the National Hurricane Center said.

The Miami-based hurricane center said that it is too early to know what path the storm will take but that it could roll ashore in the Carolinas by Friday.

Forecasters urged residents from South Carolina to the mid-Atlantic to get ready — and not just for a direct blow against the coast. They warned that Florence could slow or stall after coming ashore, with some forecasting models showing it could unload a foot or two of rain in places, causing devastating inland flooding.

“Pretend, assume, presume that a major hurricane is going to hit right smack dab in the middle of South Carolina and is going to go way inshore,” South Carolina Gov. Henry McMaster said. The state’s emergency management agency said it is “preparing for the possibility of a large-scale disaster.”

In Charleston, S.C., along the coast, city officials offered sandbags to residents. Myrtle Beach Mayor Brenda Bethune urged people to secure their homes but said it’s too early to know if evacuations will be ordered.

Myrtle Beach hardware stores and supermarkets were busy ringing up sales of bottled water, plywood and generators.

“Literally, they are filling buggies full of water, shopping carts full of water,” Ryan Deeck, grocery department manager at a Walmart, told The Sun News.

“They’re coming in and buying water and plates, and that’s about all they’re buying.”

Across the Southeast, people were urged to put together emergency supply kits, prepare their homes and research evacuation routes.

This enhanced satellite image made available by NOAA shows Tropical Storm Florence, center, in the Atlantic Ocean on Saturday, Sept. 8, 2018 at 2:45 p.m. EDT. (NOAA via AP)

the associated press
This satellite image made available by NOAA shows strengthening Hurricane Florence, center, in the Atlantic Ocean on Sunday. The U.S. Southeast could take a direct hit from the hurricane.