Howling winds and sheets of rains accompanied the storm overnight, signaling the approach of its core. Part of the pier at Atlantic Beach, N.C., collapsed before dawn on Saturday, according to television reports, and a hurricane-force wind gust was reported at Hatteras on the Outer Banks.
Radar images showed that the ragged eye of the storm appeared to reach land during the 7 a.m. hour. It is expected to force a storm surge into the bays and sounds here, inundating low-lying areas. An hour after dawn, the wide beach here in Nags Head had become a wide pool of water as waves began to erode the dunes of the Outer Banks.
Irene’s landfall marked the first time since 2008 that a hurricane made landfall in the continental United States.
The storm is forecast to continue churning north-northeast toward New York, where mandatory evacuations were issued on Friday in parts of the city.
On Saturday morning, the National Hurricane Centerin Miami downgraded the storm from a Category 2 to a Category 1, indicating that further weakening had occurred overnight. The storm’s maximum sustained winds are 90 miles per hour, with higher gusts, the hurricane center said, but forecasters reminded residents that it remained a very powerful storm.
“Some weakening is expected after Irene reaches the coast of North Carolina,” the hurricane center’s update said, “but Irene is forecast to remain a hurricane as it moves near or over the mid-Atlantic states and New England.”
According to The Associated Press, a hurricane specialist at the center, Mike Brennan, said: “The hazards are still the same.” The emphasis for this storm is on its size and duration, not necessarily how strong the strongest winds are.”
At 8:30 a.m., Progress Energy said that almost 200,000 customers had lost power in North Carolina, with the number expected to grow. Power was out in Wilmington, with wind gusts up to 72 m.p.h., but there was a sense that that part of North Carolina had made it through the worst of it.
Damage has been relatively light in the Wilmington area. Trees and a few billboards are down, but flooding remains the big concern. The ocean breached the dunes at the communities of Wrightsville Beach and Carolina Beach, and some homes are flooded. Signs still abounded of the storm’s potency — spotty power outages, downed trees on roads near the coast and damage to municipal buildings were all reported overnight, and rescuers in New Hanover County had to end a search for a possible drowning victim in the Cape Fear River because the weather had made it too dangerous to continue.
Scattered power outages were also reported in Virginia.
“The storm is moving more slowly than expected,” said Mazie Swindell Smith, the county manager in Hyde County, which is expecting storm surge from the inland bay that it abuts. “That’s not good as far as rainfall, because it’ll just sit here and dump rain.”
With an estimated 55 million people in the path of a storm the size of California, the East Coast’s major cities were preparing for the worst. Hurricane watches were posted and states of emergency declared for Delaware, Maryland, North Carolina, Pennsylvania, New England, New Jersey, New York and Virginia. Amtrak canceled train service for the weekend, and airlines began canceling flights, urging travelers to stay home.
For the first time in its history, New York City planned to shut down its entire mass transit and subway system — the nation’s largest — beginning at noon on Saturday. New Jersey Transit was set to suspend service then as well. At least 370,000 people in the city were ordered to evacuate from low-lying areas.
Organizations from the Pentagon to the American Red Cross were positioning mobile units and preparing shelters with food and water. The Defense Department amassed 18 helicopters to be ready with lifesaving equipment and put them on the Wasp, an aircraft carrier that was moved out to sea from Norfolk, Va., to get out of Hurricane Irene’s way.
“All of us have to take this storm seriously,” said President Obama, who cut short his family vacation on Martha’s Vineyard, Mass., to head back to Washington on Friday. “All indications,” he said, “point to this being a historic hurricane.”
The town manager of Wrightsville Beach, Robert Simpson, said the ocean started pouring over the dunes on Friday and flooded the small beachside community.
With a storm this big and this wet — the hurricane center said its tropical-storm-force winds stretched 290 miles — when it hits land, the power of the winds might not be as important as the amount of rainfall.
Such a huge dump of sustained rain along with high winds will most likely uproot trees from soggy ground and cause wide-scale loss of power.
Flooding is the biggest concern, said Steve Pfaff, a meteorologist with the weather service’s office in Wilmington. As much as 9 to 10 inches of rain will fall over the easternmost areas here, overwhelming drainage systems.
Most airlines have grounded flights this weekend, in the New York City area and beyond, and Newark Liberty International Airport, Kennedy International Airport and La Guardia Airport were set to close at noon on Saturday in anticipation of the severe weather.
Michael Trevino, a spokesman for the merged United Airlines and Continental Airlines, said 2,300 flights would be canceled.
“Our efforts have been focused at doing an orderly pre-cancellation so that customers can avoid having to go to airport only to find out their flight has been canceled,” Mr. Trevino said.
A JetBlue spokesman said the airline had grounded 1,252 flights in the New York area and beyond starting Saturday.
Not only were flights being grounded, but rebooking could be tricky. On Friday, Continental’s customer service line was overloaded and a recorded message told customers to try back later.
Federal officials warned that whatever the force of the winds, this storm was powerful and its effects would be felt well inland, as far as West Virginia, western Pennsylvania, western New York and interior New England.
“This is not just a coastal event,” said Bill Read, director of the National Hurricane Center. He said he was highly confident of the storm’s track, meaning that it would be a rare hurricane that travels right along the densely populated Interstate 95 corridor.
In Washington, officials postponed the dedication of the new memorial to the Rev. Dr. Martin Luther King Jr., which had been scheduled for Sunday. Mayor Vincent C. Gray declared a state of emergency and said that starting Saturday, the city would distribute five sandbags per household to those preparing their homes to withstand flooding. Pepco, a major power provider for the area, warned of extensive blackouts and said it had engaged additional crews, including one from Ohio. The Metro system was expected to continue running, officials said.
The potential power of the coming storm did not frighten everyone.
Along the Caratoke Highway in North Carolina, the road out of the Outer Banks to the north, things were unusually quiet along a road usually crawling with vacationers. There were signs that some local residents had actually heeded the mandatory evacuation order for Currituck County.
But not everyone.
Right after the last sandbag was put in place at the front door of the Cavalier Surf Shop in Nags Head, in Dare County, the store manager, Jerry Slayton, said the weekend would be a “hurri-cation.”
“We go home, play games and wait the storm out,” Jerry’s father, Ken Slayton, said.
It did not seem to matter that county officials warned on Friday afternoon that “those who do not evacuate should be prepared to sustain themselves for at least 72 hours and could experience hazards and a major disruption of services for an extended period of time.”
Others were taking things more seriously, and thinking about what mattered the most.
Daniel and Shari Sacchi secured their home near Carolina Beach on Friday before heading to her father’s house deeper inland. They packed what mattered: three days’ worth of clothes for their two sons, important documents and photo albums.
Oh, and three of Mr. Sacchi’s surfboards.
“As soon the storm passes, I’m getting in the water,” he said.