These alerts are usually issued about 48 hours before storms are set to touch down, when the arrival of tropical force winds would make any last-minute preparation hard.
The vessels would get underway from Naval Station Norfolk and Joint Expeditionary Base Little Creek to avoid potential damage from winds and tidal surges, said Colonel Rob Manning, a Pentagon spokesman.
As of 11 a.m. Tuesday, Hurricane Florence had maximum sustained winds of about 130 miles per hour, a slight weakening from earlier the morning.
Along the Cumberland Plateau, where several inches of rain fell Sunday and early Monday as remnants of Tropical Storm Gordon interacted with a cold front that swept in from the northwest, Hurricane Florence was not expected to have much of an impact. While wind damage is still ordinarily covered, insurers that were stung by storms such as Sandy in 2012, which swamped NY and New Jersey, have inserted clauses in their policies that limit coverage and set high deductibles, particularly when storms reach hurricane status.
Florence is so wide that a life-threatening storm surge was being pushed 300 miles (485 kilometres) ahead of its eye, and so wet that a swath from SC to OH and Pennsylvania could get deluged.
More than 5.4 million people live in areas now under hurricane warnings or watches on the U.S. East Coast, according to the National Weather Service.
Part of the danger may come later in the week, due to increased fears Florence "will slow considerably or stall, leading to a prolonged and exceptionally heavy and unsafe rainfall event Friday-Sunday", says the Center on Tuesday.
"We're talking 12-foot seas stretching 300 miles away from the center", the NHC's Graham said. And the longer a hurricane hovers over land, the more rain it dumps on the same place.
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Florence will unload up to 40 inches of rain in parts of North Carolina. "One of our biggest challenges is too much rain at the wrong time", McIntosh says. "The ground is already saturated and any winds could put down some trees and pose a problem". "We are expecting more wind than we had with Hugo and more water than we had with Matthew".
"Inland flooding will be a major threat and something people far from the landfall location should be concerned about", CNN meteorologist Brandon Miller said. But that part of the East Coast rarely sees any major hurricanes.
And in the 29 years since Hurricane Hugo struck, the population of the coastal Carolinas has skyrocketed.
Florence interrupted their almost two-week stay on North Carolina's Outer Banks.
A storm covering enormous area, to drench and lash more people. Make sure you have your medications.
The U.S. Coast Guard closed ports in Wilmington and Morehead City, North Carolina and Hampton Roads, Virginia to inbound vessels greater than 500 tons and was requiring vessels of that size to leave if they did not have permission to be in the ports. A year ago, people would have laughed off such a forecast, but the European model was accurate in predicting 60 inches (150 centimetres) for Hurricane Harvey in the Houston area, so "you start to wonder what these models know that we don't", University of Miami hurricane expert Brian McNoldy said.
'We have guard members preparing throughout the state, ready to meet the requests from our partnered agencies and emergency managers, ' said Army Maj. Gen.