By JONATHAN DREW, Associated Press

RALEIGH, N.C. (AP) — Mandatory evacuations were imposed for parts of three East Coast states Tuesday as millions of Americans prepared for what could become one of the most catastrophic hurricanes to hit the Eastern Seaboard in decades.Hurricane Florence's top winds dipped to 130 mph (215 kph) Tuesday morning, but it remains a Category 4 storm and is expected to approach the most-damaging Category 5 status as it slows and strengthens over very warm ocean water off the coast of North and South Carolina.The center of the massive storm is then forecast to meander Thursday, Friday and Saturday over a stretch of coastline saturated by rising seas, inundating several states with rainfall and triggering life-threatening floods.

The size of Florence is "staggering," National Hurricane Center Director Ken Graham warned.

"We could cover several states easily with the cloud cover alone," Graham said. "This is not just a coastal event."

Rainfall will be extremely heavy, dumping up to 10 to 20 inches over the next 7 days over much of North Carolina and Virginia, and even 30 inches in some places. Combined with high tides, the storm surge could reach 12 feet at the center of the storm, forecasters said Tuesday.

"The water could overtake some of these barrier islands and keep on going. With time, the wind pushes the water into every nook and cranny you can think of," Graham said. "All you have to do is look up at your ceiling, and think about 12 feet (of floodwater). That, folks, is extremely life-threatening."

North Carolina Gov. Roy Cooper said his state is "in the bullseye" and urged people to "get ready now."

The very center of that bullseye may be Camp Lejeune, the sprawling Marine Corps training base, where authorities were opening emergency operation centers and staging equipment.

"Please be prepared, be careful and be SAFE!" tweeted President Donald Trump, adding: "WE are here for you."

South Carolina's governor ordered the state's entire coastline evacuated starting at noon Tuesday and predicted that 1 million people would flee as highways reverse directions. Virginia's governor ordered a mandatory evacuation for some residents of low-lying coastal areas, while some coastal counties in North Carolina have done the same.

Tuesday's 7-day rainfall forecast showed 20 inches or more falling there, part of a wide swath of rainfall that could total ten inches or more over much of Virginia and drench the nation's capital. Some isolated areas could get 30 inches, forecasters said.

Florence could hit the Carolinas harder than any hurricane since Hazel packed 130 mph (209 kph) winds in 1954. That Category 4 storm destroyed 15,000 buildings and killed 19 people in North Carolina. In the six decades since then, many thousands of people have moved to the coast.

Ahead of Florence's arrival, barrier islands were already seeing dangerous rip currents and seawater flowed over a state highway — the harbinger of a storm surge that could wipe out dunes and submerge entire communities.

Watches were in effect Tuesday for a storm surge that could reach up to 12 feet at high tide on a stretch from Cape Fear to Cape Lookout in North Carolina, forecasters said. A hurricane watch was in effect for Edisto Beach, South Carolina, to Virginia's southern border, and the first hurricane-force winds arriving late Thursday.

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 all the way into the Appalachian mountains and as far away as West Virginia, causing flash floods, mudslides and other dangerous conditions in places that don't usually get much tropical weather.

"This is going to produce heavy rainfall, and it may not move very fast. The threat will be inland, so I'm afraid, based on my experience at FEMA, that the public is probably not as prepared as everybody would like," said Craig Fugate, former director of the Federal Emergency Management Agency.

Florence is expected to linger once onshore, downing trees, knocking out electricity and causing widespread flooding along a path that includes half a dozen nuclear power plants, pits holding coal-ash and other industrial waste, and numerous hog farms that store animal waste in massive open-air lagoons.

A warm ocean is the fuel that powers hurricanes, and this area of the ocean is seeing temperatures peak near 85 degrees (30 Celsius), hurricane specialist Eric Blake wrote. And with little wind shear to pull the storm apart, Florence's hurricane-strength winds were expanding, reaching 40 miles (64 kilometers) from the eye of the storm.

"Unfortunately, the models were right. Florence has rapidly intensified into an extremely dangerous hurricane," Blake wrote Monday evening, predicting that the hurricane's top sustained winds would approach the 157 mph (253 kph) threshold for a wost-case Category 5 scenario. Tuesday morning's forecast still supports this, the National Hurricane Center said.

By 8 a.m. Tuesday, Florence was centered about 950 miles (1,530 kilometers) east-southeast of Cape Fear, North Carolina, and moving west-northwest at 15 mph (24 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.

Two other storms were spinning in the Atlantic as the 2018 hurricane season reaches its peak. Isaac became a tropical storm again approaching the Caribbean, while Hurricane Helene was veering northward, no threat to land.

In the Pacific, Olivia became a tropical storm again on a path to hit the Hawaiian islands early Wednesday.

Airlines, including American, Southwest, Delta and JetBlue, have begun letting affected passengers change travel plans without the usual fees.

South Carolina Gov. Henry McMaster said an estimated 1 million people would be fleeing his state's coast, with eastbound lanes of Interstate 26 heading into Charleston and U.S. 501 heading into Myrtle Beach reversed to ease the exodus.

Virginia Gov. Ralph Northam's evacuation order applies to about 245,000 people, including parts of the Hampton Roads area and Eastern Shore.

Liz Browning Fox was planning to ride out the storm nevertheless on the Outer Banks. She said her house, built in 2009 in Buxton, North Carolina, is on a ridge and built to withstand a hurricane. But even the most secure homes could be surrounded by water, or penetrated by wind-launched debris.

"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."

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Associated Press writers Seth Borenstein in Washington; Jennifer Kay in Miami; Jeffrey Collins and Meg Kinnard in Columbia, South Carolina; and Jeff Martin in Atlanta contributed to this report.

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For the latest on Hurricane Florence, visit www.apnews.com/tag/Hurricanes.

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