A monstrous Hurricane Irene tightened its aim Thursday on the Eastern Seaboard, threatening 65 million people along a shore-hugging path from North Carolina to New England. One of the nation's top experts called it his "nightmare" scenario.
The Category 3 storm with winds of 115 mph -- the threshold for a major hurricane -- would be the strongest to strike the East Coast in seven years, and people were already getting out of the way.
Tens of thousands fled North Carolina beach towns, farmers pulled up their crops and the Navy ordered ships to sea so they could endure the punishing wind and waves in open water.
All eyes were on Irene's projected path, which showed it bringing misery to every city along the I-95 corridor, including Washington, New York and Boston. The former chief of the National Hurricane Center called it one of his three worst possible situations.
"One of my greatest nightmares was having a major hurricane go up the whole Northeast Coast," Max Mayfield, the center's retired director, told the Associated Press.
He said the damage will probably climb into billions of dollars: "This is going to have an impact on the United States economy."
The head of the Federal Emergency Management Agency said damages could exceed most previous storms because so many people live along the East Coast, and property values are high.
"We've got a lot more people that are potentially in the path of this storm," FEMA Director Craig Fugate said in an interview with the AP. "This is one of the largest populations that will be impacted by one storm at one time."
The storm would "have a lot of impact well away from the coastline," he added. "A little bit of damage over big areas with large populations can add up fast."
Irene was massive, with tropical-force winds extending almost twice as far as normal, about the same size as Katrina, which devastated New Orleans in 2005.
"It's not going to be a Katrina, but it's serious," said MIT meteorology professor Kerry Emanuel. "People have to take it seriously."
The governors of North Carolina, Virginia, Maryland, Delaware, New York and New Jersey declared emergencies to free up resources, and authorities all the way to New England urged residents in low-lying areas to gather supplies and learn the way to a safe location.
Irene was expected to come ashore Saturday in North Carolina with 115 mph winds and a storm surge of 5 to 10 feet. It could dump a foot of rain, with as much as 15 inches falling in some places along the coast and around Chesapeake Bay.
With heavy rain and storm surge predicted for the nation's capital, organizers postponed Sunday's dedication of the Martin Luther King Jr. Memorial on the National Mall.
Already in South Florida near West Palm Beach, authorities blame the rough ocean churned up by the outer bands of Irene caused eight people to be injured when a wave knocked them off a jetty.
Scientists predict Irene will then chug up the coast. Some forecasts showed it taking dead aim at New York City, with its eye passing over Brooklyn and Manhattan before weakening and trudging through New England.
If the storm strikes New York, it will probably be a Category 1 or 2, depending on its exact track, hurricane specialist John Cangialosi said. Hurricanes are rare in the Northeast because the region's cooler seas tend to weaken storms as they approach, and they have to take a narrow track to strike New York without first hitting other parts of the coast and weakening there.
Still, strong storms have been known to unleash serious damage in an urban environment already surrounded by water.
A September 1821 hurricane raised tides by 13 feet in an hour and flooded all of Manhattan south of Canal Street -- an area that now includes the nation's financial capital.
Mayor Michael R. Bloomberg ordered mandatory evacuations of the sick and elderly, and officials began preparations to shut down the nation's largest mass transit system Thursday.
The mayor said he expected the city would shut down its entire transit system at some point Saturday afternoon, with buses, subways and trains unlikely to be available again until sometime Monday and perhaps later.
Thursday, Ocean City, Md., officials ordered thousands of residents and tourists to abandon the beach community. Earlier in North Carolina, three coastal counties issued evacuation orders covering more than 200,000 people, including tourists and full-time residents. President Obama declared an emergency for the state, allowing for federal help.
Farmers grimly accepted the fate of their crops. Strong winds and widespread flooding could mean billions of dollars in losses for corn, cotton, soybean, tobacco and timber growers.
In Washington, where residents were rattled by a rare earthquake Tuesday, officials warned people to be prepared for stormy conditions regardless of Irene's exact path and to stay away from the beaches in the region.
The Philadelphia area could get more than a half-foot of rain, accompanied by sustained winds up to 50 mph. Mayor Michael Nutter said it could be the worst storm in at least 50 years.
New Jersey Gov. Chris Christie asked all visitors to the shore to get out by midday today. He said Irene was poised to be a "serious, significant event," with flooding a threat across the entire state. A mandatory evacuation was ordered for Cape May County.