Forecasters say the hurricane's strength is expected to fluctuate but it still will be a unsafe storm by the time it reaches the coast of SC or North Carolina on Thursday.
Hurricane Hugo was an example on September 22, 1989, when it made landfall on Sullivan's Island, South Carolina.
In their forecast discussion, the BWS said, "Moderate east-southeasterly winds Tuesday morning will gradually increase moderate to strong in the evening as Hurricane Florence - by then expected to be a category 4 storm, passes it's closest point of approach 300nm to our south".
With little wind shear to pull the storm apart, hurricane-strength winds have been expanding to 40 miles (64 kilometers) from the eye of the storm, and tropical-storm-force winds 150 miles from the center. Hurricane Isaac, churning in the mid-Atlantic Ocean with wind speeds of around 75 miles per hour, is following closely behind Florence.
"You never know, there could be tree missiles coming from any direction", she said. She said it was built in 2009 in Buxton, North Carolina, up on a ridge, and made to withstand a hurricane. Residents and visitors in popular tourist spots such as Duck and Corolla faced a Tuesday deadline. She grew up on the island chain, and says this will be only the second time she's evacuated.
Hurricane season runs through November 30. An estimated 250,000 more people from the northern Outer Banks were due to be sent to higher ground starting Tuesday at midday. The order applies to all eight counties along the coast: Jasper, Beaufort, Colleton, Charleston, Dorchester, Georgetown, Horry and Berkeley counties.
Concerns about the monster storm extended even into Virginia.
Florence is now a Category 4 storm, reaching that status a day earlier than experts had predicted.
A tropical storm warning means that tropical storm conditions are expected somewhere in the warning area within 36 hours, and a watch within 48 hours. Isaac is expected to be near hurricane strength when it moves through the central Lesser Antilles, with some weakening forecast afterward on Friday.
A "major" hurricane is one with sustained winds of more than 110 miles per hour.
Hurricane Helene turns northward, no landfall expected
The center of the strong storm is about 1,240 miles east-southeast of Bald Head Island, with the hurricane moving westward at roughly 13 mph.
"Red, no-swimming flags are flying, and everyone must stay out of the water", Dare County Emergency Management Director Drew Pearson said.
North and SC and Virginia ordered mass evacuations along the coast. That system is moving northwest and should enter the Gulf of Mexico.
"This is very scary rain event potentially setting up this week", Rossi said. Rain could reach as much as 10 inches (25 centimeters) elsewhere in North Carolina, Virginia, parts of Maryland and Washington, D.C.
Feltgen said it's important that people don't get "hung up on the cone", and prepare for the possibility of impacts in areas outside of it.
"The storm has a long way to travel", Dixon said. "The best safety plan is preparation and common sense".
As of Monday night, there are three hurricanes in the Atlantic Ocean.
Many newcomers have moved to the coast in the almost 19 years since the last strong hurricane - Floyd - threatened the area.
"Meteorologists don't see any environmental factors that would help to weaken the storm", Weather Channel meteorologist Dale Eck said in an interview today.
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