SHIP BOTTOM, N.J. -- Shelters opened and tens of thousands of people were ordered to evacuate coastal areas Sunday as big cities and small towns across the Northeast buttoned up against the onslaught of a superstorm threatening some 50 million people along the most heavily populated corridor in the nation.
"The time for preparing and talking is about over," Federal Emergency Management Administrator Craig Fugate warned as a monster Hurricane Sandy headed up the Eastern Seaboard on a collision course with two other weather systems. "People need to be acting now.”
New York City announced its subways, buses and trains would stop running Sunday night, and its 1.1 million-student school system would be closed on Monday. Mayor Michael Bloomberg also ordered the evacuation of part of lower Manhattan and other low-lying neighborhoods.
"If you don't evacuate, you are not only endangering your life, you are also endangering the lives of the first responders who are going in to rescue you," he said. "This is a serious and dangerous storm.”
Tens of thousands of people along the coast in Delaware, New Jersey, Connecticut and other threatened areas were also under orders to clear out because of the danger of as much as a foot of rain, punishing winds of 80 mph and a potentially deadly tidal surge of 4 to 8 feet.
Sandy was headed north from the Caribbean, where it left nearly five dozen people dead, and was expected to hook left toward the mid-Atlantic coast and come ashore late Monday or early Tuesday, most likely in New Jersey, colliding with a wintry storm moving in from the west and cold air streaming down from the Arctic.
Forecasters warned that the resulting megastorm could wreak havoc over 800 miles from the East Coast to the Great Lakes. Parts of West Virginia, Virginia, Kentucky and North Carolina could get snow -- 2 feet or more in places.
Amtrak began canceling train service Saturday night to parts of the East Coast, including between Washington and New York. Airlines started moving planes out of airports to avoid damage and added Sunday flights out of New York and Washington in preparation for flight cancellations on Monday.
The Virginia National Guard was authorized to call up to 500 troops for debris removal and road-clearing, while homeowners stacked sandbags at their front doors in coastal towns.
'Worst case scenario'
The projected storm surge from Hurricane Sandy is a "worst case scenario" with devastating waves and tides predicted for the highly populated New York City metro area, government forecasters said Sunday.
The more they look, the more the experts worry about the water -- which usually kills and does more damage than winds in hurricanes.
In this case, seas will be amped up by giant waves and full-moon-powered high tides. That will combine with drenching rains, triggering inland flooding as the hurricane merges with a winter storm system that will worsen it and hold it in place for days.
Louis Uccellini, environmental prediction chief for the National Oceanic and Atmospheric Administration, told The Associated Press that given Sandy's due east-to-west track into New Jersey, that puts the worst of the storm surge just north in New York City, Long Island and Northern New Jersey. "Yes, this is the worst case scenario," he said.
In a measurement of pure kinetic energy, NOAA's hurricane research division on Sunday ranked the surge and wave "destruction potential" for Sandy -- just the hurricane, not the hybrid storm it will eventually become -- at 5.8 on a 0 to 6 scale. The damage expected from winds will be far less, experts said. Weather Underground meteorologist Jeff Masters says that storm surge destruction potential number is a record and it's due to the storm's massive size.
"You have a lot of wind acting over a long distance of water for hundreds of miles" and that piles the storm surge up when it finally comes ashore, Masters said. Even though it doesn't pack much power in maximum wind speed, the tremendous size of Sandy -- more than 1,000 miles across with tropical storm force winds -- adds to the pummeling power when it comes ashore, he said.
The storm surge energy numbers are bigger than the deadly 2005 Hurricane Katrina, but that can be misleading. Katrina's destruction was concentrated in a small area, making it much worse, Masters said. Sandy's storm surge energy is spread over a wider area. Also, Katrina hit a city that is below sea level and had problems with levees.
National Hurricane Center Director Rick Knabb said Hurricane Sandy's size means some coastal parts of New York and New Jersey may see water rise from 6 to 11 feet above ground from surge and waves. New York will close its subways starting Sunday evening. The rest of the coast north of Virginia can expect 4 to 8 feet of surge.
Knabb said millions of people may be harmed by inland flooding.
A NOAA map of inland and coastal flood watches covers practically the entire Northeast: All of Maryland, New Jersey, Delaware, and Connecticut; most of Pennsylvania, New York, Massachusetts and Vermont, and parts of northeastern Ohio, eastern Virginia, North Carolina, and western New Hampshire.
Along the mid-Atlantic coast, storm surge is already starting to build, Uccellini said. NOAA's Coastal Services Center chief Margaret Davidson said to expect "bodacious impacts" in the area.
The surge -- in which water steadily increases from the ocean-- will be worst in the areas north of where Sandy comes ashore.
New York will have the most intense storm surge if Sandy comes ashore anywhere in New Jersey, Uccellini said. Only if it arrives farther south, such as in Delaware, will New York see a slightly, only slightly, smaller storm surge.
In general, areas to the south and west of landfall will get the heaviest of rains. Some areas of Delaware and the Maryland and Virginia peninsula will see a foot of rain over the several days the storm parks in the East, Uccellini said.
The good news about inland flooding is that the rivers and ground aren't as saturated as they were last year when Hurricane Irene struck, causing nearly $16 billion in damage, much of it from inland flooding in places like Vermont, Uccellini and Masters said.