NEW YORK -- Hundreds of thousands of New Yorkers were told Thursday to pack a bag and prepare to be evacuated as the nation's biggest city braced for its first hurricane in decades.
Mayor Michael Bloomberg ordered nursing homes and five hospitals in low-lying areas evacuated beginning Friday and said he would order 270,000 other people moved by Saturday if the storm stays on its current path.
Hurricane Irene was on track to make landfall Saturday in North Carolina and then move up the East Coast, reaching the New York area by late Sunday.
"For the general public, it's a good idea to move Friday," Bloomberg said. "Keep in mind, it is possible - I don't know that I want to say likely - but it is very conceivable ... that Saturday morning at 8 o'clock, we're going to say, `Look, the forecast has not changed. The storm is still barreling down on us. It's still very dangerous. You must get out of these areas.'"
Evacuating hundreds of thousands of people would be particularly difficult in New York, where there are about 1.6 million people in Manhattan, many without cars. There are about 6.8 million in the city's other four boroughs. (Check here to see NYC evacuation zones).
"Don't wait until the last minute," the mayor said. "If you can move out on Friday, that's great."
Bloomberg advised residents on the southern tip of Manhattan and on Brooklyn's Coney Island to start moving items upstairs and to be ready to leave immediately. Apartment building managers emailed residents, telling them to close windows and expect power outages. Flyers were posted in building lobbies.
"If you have a car and you live in a low-lying area, my suggestion is to park on top of a hill, not in the valley," Bloomberg said. "It's those kinds of things. Take some precautions now, so that if it gets to that you'll have less to do."
Irene rolled toward the Carolinas on Thursday with winds of 115 mph. The storm was expected to weaken after brushing North Carolina's Outer Banks, but it will still likely be a hurricane when it rumbles toward the Northeast.
Forecasters said passing near Manhattan could lead to a nightmare scenario: shattered glass falling from skyscrapers, flooded subways and seawater coursing through the streets.
In the last 200 years, New York has seen only a few significant hurricanes. In September of 1821, a hurricane raised tides by 13 feet in an hour and flooded all of Manhattan south of Canal Street, the southernmost tip of the city. The area now includes Wall Street and the World Trade Center memorial.
In 1938, a storm dubbed the Long Island Express came ashore about 75 miles east of the city on neighboring Long Island and then hit New England, killing 700 people and leaving 63,000 homeless.
Craig Fugate, head of the Federal Emergency Management Agency, worries about a storm surge coming into Manhattan, home to some of the most valuable real estate in the country. He noted pictures from a 1944 hurricane where police in Midtown, where Times Square, Broadway theaters and the Empire State Building are located, were standing in waist-deep water.
"This is going to have a lot of impacts well away from the coastline," Fugate said. "A little bit of damage over big areas with large populations can add up fast."
In Lower Manhattan, few seemed preoccupied with preparations.
"I live on the 10th floor of a 30-story building," said Sam Laury, who lives in Battery Park City, one of the areas that Bloomberg said might be evacuated. "I'm sure I'll be fine."
Irene is a large storm, with tropical storm-force winds extending nearly 300 miles from its center. And the storm could hit at a time when high tides reach their highest levels, which could amplify flooding in a city built around bays and rivers. Some experts predict a storm surge of five feet or more. Lower Manhattan could see streets under a few feet of water.
"In many ways, a Category 2 or stronger storm hitting New York is a lot of people's nightmare, for a number of reasons," said Susan Cutter, director of the Hazards and Vulnerability Research Institute at the University of South Carolina.
Even if the winds aren't strong enough to damage buildings made largely of brick, concrete and steel, a lot of New York's subway system and power lines are underground. The city's airports are close to the water, too, and could be inundated, as could densely packed neighborhoods. Hospitals were told to make sure generators were ready.
Poised to brush one of the most densely populated parts of the country, Irene could cause billions or even hundreds of billions of dollars in damage, said Kathleen Tierney, director of the Natural Hazards Center at the University of Colorado.