Hurricane Irene zeroed in on land Saturday, losing some power but threatening a catastrophic run up the US East Coast. More than 2 million people were told to flee, and New York City ordered the nation's biggest subway system shut down for the first time because of a natural disaster.
The National Hurricane Center in Miami said the enormous storm's top sustained winds slipped to 90 mph (150 kph) early Saturday from 100 mph (160 kph) overnight but warned Irene would remain a hurricane as it moves up the mid-Atlantic coast, still on track to hit the New York City area and New England.
"The hazards are still the same," NHC hurricane specialist Mike Brennan said. "The emphasis for this storm is on its size and duration, not necessarily how strong the strongest winds are."
As the storm's outer bands of wind and rain lashed the North Carolina coast, knocking out power in places, authorities farther north begged people to get out of harm's way.
"Don't wait. Don't delay," said President Barack Obama, who cut short his summer vacation and return to Washington. "I cannot stress this highly enough: If you are in the projected path of this hurricane, you have to take precautions now."
The storm's center was about 35 miles (55 kilometers) south of Cape Lookout on North Carolina's Outer Banks early Saturday and lumbering north-northeastward at 14 mph (22 kph).
Tropical storm-force winds were already blowing ashore ahead of Irene, and wind and rain knocked out power to more than 80,000 customers along the North Carolina coast, including a hospital in Morehead City. A woman who answered the phone there said the hospital was running on generators.
A coastal town official in North Carolina said witnesses believed a tornado spawned by Irene lifted the roof off a car dealership warehouse in Belhaven on Friday night.
Forecasters said the core of Irene would make landfall in the next few hours, roll up the mid-Atlantic coast Saturday night and over southern New England on Sunday.
Hurricane warnings were issued from North Carolina to New York and farther north to the islands of Nantucket and Martha's Vineyard off Massachusetts. Evacuation orders covered at least 2.3 million people, including 1 million in New Jersey, 315,000 in Maryland, 300,000 in North Carolina, 200,000 in Virginia and 100,000 in Delaware.
"This is probably the largest number of people that have been threatened by a single hurricane in the United States," said Jay Baker, a geography professor at Florida State University.
U.S. airlines canceled at least 6,100 flights through Monday, grounding hundreds of thousands of passengers as the storm could strike major airports from Washington to Boston.
New York City ordered more than 300,000 people who live in flood-prone areas to leave, including Battery Park City at the southern tip of Manhattan, Coney Island and the beachfront Rockaways. But most New Yorkers don't have a car, and city was shutting down public transportation at noon Saturday.
The New York City transit system carries about 5 million people on an average weekday, fewer on weekends. It has been shut down several times before, including during a 2005 transit workers' strike and after the Sept. 11 attacks a decade ago, but never for weather.
Aviation officials said they would close the five main New York City-area airports to arriving domestic and international flights beginning at noon on Saturday. Many departures also were canceled.
Mayor Michael Bloomberg said there was little authorities could do to force people to leave and warned: "But if you don't follow this, people may die."
Shelters in New York were opening Friday afternoon, and the city was placed under its first hurricane warning since 1985.