The authorities warned Wednesday that in “the worst case scenario” Hurricane Irene could reach New York City this weekend as a Category 1 hurricane, with winds surpassing 72 miles an hour that produce a storm surge of 6 to 12 feet.
Under another scenario, New Yorkers would experience Irene as a strong tropical storm dropping as much as a foot of rain, said Joseph F. Bruno, the commissioner of the city’s office of emergency management, who was joined by Caswell F. Holloway, the deputy mayor for operations.
Mr. Bruno and Mr. Holloway used their news conference to ask New Yorkers to begin planning for the possibility that the storm could cause serious damage. If it strikes as hurricane, Mr. Bruno said, New Yorkers who live in the low-lying areas of the city could be evacuated.
“There is still a significant chance that it could be a hurricane-strength storm by the time it gets up here,” Mr. Holloway said.
Under an evacuation plan devised in 2007, city officials have grouped neighborhoods into various zones, depending on their risk of flooding in the event of a major storm surge.
The first areas to be evacuated, Zone A, include parts of Lower Manhattan closest to the Hudson and East Rivers, a strip of the Brooklyn waterfront along the East River and the Upper Bay, as well as Brighton Beach, Coney Island, parts of the Rockaways, and the coastal areas of Staten Island, according to a map produced by the Office of Emergency Management.
Irene is expected to make landfall in the United States as a Category 3 storm in eastern North Carolina on Saturday, according to the National Hurricane Center in Miami, and head north.
Over the next few days, city workers will prepare for the storm by cleaning up storm sewers and visiting construction sites to warn workers to tie down loose building material, said Stu Loeser, a spokesman for the mayor.