RALEIGH, N.C. — Florence exploded into a potentially catastrophic Category 4 hurricane Monday as it closed in on North and South Carolina, carrying wind and water that could wreak havoc over a wide stretch of the eastern United States later this week.
The South Carolina governor ordered the state’s entire coastline to be evacuated starting at noon Tuesday.
The first effects were already being seen on barrier islands as dangerous rip currents hit beaches and seawater flowed over a state highway. Communities along a stretch of coastline that is vulnerable to rising sea levels due to climate change prepared to evacuate.
For many people, the challenge could be finding a safe refuge: If Florence slows to a crawl just off the coast, it could bring torrential rains to the Appalachian mountains and as far away as West Virginia, causing flash floods, mudslides and other dangerous conditions.
The storm’s potential path also includes half a dozen nuclear power plants, pits holding coal-ash and other industrial waste, and numerous eastern hog farms that store animal waste in massive open-air lagoons.
National Hurricane Center Director Ken Graham warned that Florence was forecast to linger over the Carolinas once it reaches shore. People living well inland should prepare to lose power and endure flooding and other hazards, he warned.
‘‘It’s not just the coast,’’ Graham said. ‘‘When you stall a system like this and it moves real slow, some of that rainfall can extend well away from the center.’’
A warm ocean is the fuel that powers hurricanes, and Florence will be moving over waters where temperatures are peaking near 85 degrees (30 Celsius), hurricane specialist Eric Blake wrote. And with little wind shear to pull the storm apart, Florence’s hurricane wind field was expected to expand over the coming days, increasing its storm surge and inland wind threats.
By noon Monday, Florence had top sustained winds of 130 mph (195 kph). It was centered about 1,230 miles (1,985 kilometers) east-southeast of Cape Fear, North Carolina, and moving west at 13 mph (20 kph). Its center will move between Bermuda and the Bahamas on Tuesday and Wednesday and approach the coast of South Carolina or North Carolina on Thursday, the National Hurricane Center said.
Meanwhile, two other storms were also spinning in the Atlantic. Hurricane Isaac was expected to lose strength as it reaches the Caribbean, and Helene, much farther out to sea, may veer northward into the open ocean as the 2018 hurricane season reaches its peak.
Preparations for Florence were intensifying up and down the densely populated coast. Since reliable record-keeping began more than 150 years ago, North Carolina has only been hit by one Category 4 hurricane: Hazel, with 130 mph winds, in 1954.
The parking lot has been full for three days at the Ace Hardware store in coastal Calabash, North Carolina, where manager Tom Roberts said he sold 150 gas cans in two hours Monday, along with generators, plywood, rope, manual can openers, sand bags and a plethora of other items.
‘‘I’ve been doing this since 1983,’’ Roberts said as he completed an order for another 18-wheeler full of supplies. ‘‘This is the craziest one.’’
Many newcomers have moved to the coast in the nearly 19 years since the last strong hurricane — Floyd — threatened the area. Roberts said he’s telling them to get out of town.
‘‘I’m telling them to go inland, but I’m worried about the rain and tornadoes too,’’ Roberts said.
Several meteorologists said Florence could do what Hurricane Harvey did over Texas, dumping days of rain, although not quite as bad.
‘‘I think this is very Harvey-esque,’’ said University of Miami hurricane expert Brian McNoldy. ‘‘Normally, a landfalling tropical cyclone just keeps on going inland, gradually dissipating and raining itself out. But on rare occasions, the steering patterns can line up such that a storm slips into a dead zone between troughs and ridges.’’
On North Carolina’s Outer Banks, Dawn Farrow Taylor, 50, was gathering photos and important documents and filling prescriptions Monday before heading inland. She grew up on the island chain, and says this will be only the second time she’s evacuated.
‘‘I don’t think many of us have ever been through a Category 4. And out here we’re so fragile. We’re just a strip of land — we’re a barrier island,’’ she said.
To the south in the village of Buxton, Liz Browning Fox plans to ride the storm out in her house on top of a ridge, but she worries about the roads washing out. She believes her home, built in 2009, will be secure, but it’s hard to foresee all potential hazards.
‘‘You never know, there could be tree missiles coming from any direction,’’ she said. ‘‘There is no way to be completely safe.’’
But, she added, she’s not sure whether going inland would be much safer: ‘‘I don’t know where to go from here.’’
The governors of North and South Carolina and Virginia declared states of emergency far ahead of the approaching storm. South Carolina Gov. Henry McMaster also suspended his campaign and asked President Donald Trump for a federal emergency declaration.
Navy ships off Virginia’s coast were preparing to sail out of the path. The University of North Carolina at Wilmington canceled classes as people stocked up on supplies.
North Carolina Gov. Roy Cooper said his state was ‘‘in the bullseye’’ of the storm.
‘‘Let me be clear: North Carolina is taking Hurricane Florence seriously and you should too,’’ Cooper said at a news conference. ‘‘Get ready now.’’
In coastal Charleston, South Carolina, city officials offered sandbags to residents, while Myrtle Beach officials urged people to secure their homes.
Lining up behind Florence, Isaac was about 1,150 miles (1,855 kilometers) east of the Windward Islands with top winds of 75 mph (120 kph) early Monday, accelerating on a path to cross into the lower Caribbean Thursday as a weak hurricane.
Helene was still in the Atlantic’s spawning ground for hurricanes off the coast of Africa, swirling with 105 mph (165 kmh) winds and forecast to become a major hurricane, about 375 miles (600 kilometers) west of the Cape Verde islands.