According to the experts, it will take 18 hours to evacuate one million people from New York in the event of a major storm, but there may only be six hours notice.

The infrequency of such storms leads to a lackadaisical attitude in terms of preparation, and could make residents reluctant to evacuate when the time comes, said New York State Insurance Superintendent Howard Mills.

“Many New Yorkers believe that unless you live in an area where there are swaying palm trees and guys playing ukuleles, there is just no risk,” Mr. Mills said.

Nicholas Coch, City University of New York professor of geology, asserted that if a hurricane hits New York, the city's unique location at something of a right angle from New Jersey to Connecticut along with its skyscrapers will produce a storm-surge amplification that could lead to a Category 3 storm producing Category 5 damage.

According to Professor Coch, using the five-point Saffir-Simpson Scale, it takes a Category 3 storm to generate a 13-foot storm surge, but in Manhattan it takes only a Category 1 storm to push waters to that level.

A major storm hitting Manhattan could send a wave of water 20-to-30 feet high over a mile from the southern tip of the island up as high as Broome Street, he said.

Bridges and subways will not serve as evacuation routes once the storm floods them, and flooded underground electrical systems will take far longer to fix than those seemingly interminable delays down south, because of the damage to cables from salt water, Mr. Coch added.

While the death from storms has decreased in recent years as the dollar value of the damage has risen, Mr. Coch sees the death toll rising in the event of a Northeast hurricane. “These residents are just not going to evacuate,” he said. “I tell my friends the denial is not just a river in Egypt,” Mr. Coch remarked.

Urban trees with their shallow roots will also be vulnerable, while flying debris will present a new kind of danger that has not been calculated into many risk models, he added.

“When a storm hits the Northeast it will be twice as large and come three times faster than what you see down south,” he warned.

Despite the peril, Northeasterners, according to a federal official, are also more lax when it comes to buying flood insurance compared to the nationwide norm.

David Maurstad, who heads up the National Flood Insurance Program, said rough estimates indicate that about 50 percent of homeowners in high-risk areas fail to purchase flood insurance, while in the Northeast the number rises to 71 percent.