New York City's mayor has told residents who need to evacuate ahead of the anticipated arrival of Hurricane Irene that they should do so immediately.
Mayor Michael Bloomberg, speaking at a news conference, said residents who have to leave the city should go straight away because transit systems will shut down at noon (1600 GMT) on Saturday, bridges may close and the city does not have enough resources to evacuate everyone after the weather worsens.
Mandatory evacuations have been ordered for 370,000 New Yorkers who live mostly in low-lying areas. The storm is expected to reach New York on Sunday.
The unprecedented orders, which affect New Yorkers from Manhattan and out to the beaches of Brooklyn and Queens, dealt the congested metropolis a formidable logistical challenge that raised more questions than it resolved.
Some questioned where all the people in New York's flood-prone areas were supposed to go and, more pointedly, how they were going to get there since many do not own a car.
Subways, buses and trains in one of the world's largest public transportation systems are to stop running at noon on Saturday. Bridges and tunnels could also be closed as the storm approaches, clogging traffic in an already congested city.
The five main New York City-area airports are also scheduled to close at noon on Saturday for arriving passenger flights. Three of them, John F Kennedy International Airport, LaGuardia International Airport and Newark Liberty International Airport, are among the busiest airports in the nation.
Officials hoped most residents would stay with family and friends, and for the rest the city opened nearly 100 shelters with a capacity of 71,000 people.
Many people scoffed at the danger and vowed to ride it out at home.
Irene made landfall in North Carolina on today and is expected to roll up the east coast, reaching New York on Sunday. A hurricane warning was issued for the city on Friday afternoon, the first time this has happened since Gloria in 1985.
If the storm stays on its current path, skyscraper windows could shatter, tree branches would fall and debris would be tossed around. Streets in the southern tip of the city could be under a few feet of water, and police readied rescue boats but said they would not go out if conditions were poor.
Mr Bloomberg said he was confident people would get out of the storm's way.
"We do not have the manpower to go door-to-door and drag people out of their homes," he said. "Nobody's going to get fined. Nobody's going to go to jail. But if you don't follow this, people might die."
Several New York landmarks were under the evacuation order, including the Battery Park City area, where tourists catch ferries to the Statue of Liberty. Construction was stopping throughout the city, and workers at the site of the World Trade Centre were dismantling a crane and securing equipment.
Mr Bloomberg said there would be no effect on the September 11 memorial opening the day after the 10th anniversary of the 2001 terrorist attacks.
Sporting events, concerts and even Broadway are going dark.
Mr Bloomberg weathered criticism after a December 26 storm dumped nearly 2ft of snow that seemed to catch officials by surprise. Subway trains, buses and ambulances got stuck in the snow, some for hours, and streets were impassable for days. Mr Bloomberg ultimately called it an "inadequate and unacceptable" response.
This time officials are not taking any chances. Transit officials said they cannot run once sustained winds reach 39mph, and they need eight hours to move trains and equipment to safety.
The subway system will not reopen until at least Monday, after pumps remove water from flooded stations. Even on a dry day, about 200 pump rooms remove up to 15 million gallons of water that seeps into the tunnels deep underground.
There are about 1.6 million people in Manhattan and about 6.8 million in the city's other four boroughs.
Mr Bloomberg warned residents not to be fooled by the sunny weather on Friday and said police officers would use loudspeakers on patrol vehicles to spread the word about the evacuation.
For those with cars, parking was available at the city's evacuation centres. From there, each family will be assigned to a shelter and be taken there by bus.
In the Queens community of the Rockaways, more than 111,000 people live on a barrier peninsula connected to the city by two bridges and to Long Island to the west.
The city's public transit system carries about five million passengers on an average weekday, and the entire system has never before been halted because of natural disaster.
It was seriously hobbled by an August 2007 rainstorm that disabled or delayed every one of the city's subway lines. And it was shut down after the 9/11 attacks and during a 2005 strike.
"It's possible to evacuate without going very far," said John Nielsen-Gammon, a Texas A&M University meteorologist who has been involved in disaster planning in his role as the state climatologist.
"The big wild card for New York is the fact that nobody there is used to a hurricane and can't rely on common sense or past experience as a guide. And what we learned from evacuations in Houston is that people rely on their friends and their own experience as much as, or more than, they rely on public officials."Reuse content