The storm, a wide and relentless mass that had had lurched onto the Outer Banks of North Carolina in the early daylight hours of Saturday, heaved clumsily but implacably north, leaving in its wake at least nine deaths. After crawling slowly from North Carolina into Virginia, the storm weaved out to sea and onto a path that forecasters said would take it to Long Island and New York City.

The storm was a spinning kaleidoscope of weather, sometimes pounding windows with rain, sometimes flashing the sky with lightning, sometimes blacking out the horizon with ominous, low-riding clouds. As the hurricane moved up the East Coast, tornado watches had moved right along with it, and that lockstep continued as the storm closed in on the New York area: early Sunday, the National Weather Service announced a tornado watch for the city, along with Westchester, Suffolk, Nassau and Rockland Counties. “It’s actually common when we have these tropical systems,” said Brian Ceimnecki, a meteorologist with the Weather Service.

The Nassau County executive, Edward P. Mangano, said that “thousands” of people were spending the night in county facilities, including Nassau County Community College. He asked people in areas that were in danger to stay with friends or relatives, if possible.

The city opened 78 emergency shelters that could take in 70,000 people. But officials said that only 8,700 had arrived by 11 p.m. on Saturday. The only other statistics available pointed to the difficulty of getting people to abide by the mayor’s mandatory evacuation order in what the city calls Zone A low-lying areas: The mayor had said several hours earlier that 80 percent of the residents in some city-run buildings — but only 50 percent in others — had left.

Gov. Andrew M. Cuomo ordered 2,000 National Guard troops called up. Mr. Cuomo saw the first of them off from the 69th Regiment Armory, on Lexington Avenue at 26th Street, after saying they would assist the police, the Metropolitan Transportation Authority and the Port Authority of New York and New Jersey. He also said that some would be sent to Long Island, which could face heavy damage in the storm.