According to the NY Daily News, the New York City subway system could be shut down as early as late Saturday afternoon, ahead of the expected arrival of Irene on Sunday morning. The MTA's hurricane plan describes a "worst possible scenario" in which the hurricane hits south of the city, sending of a wall of water onto New York:
See here for the possibility that NYC evacuations will take place on Shabbat and here for a map of potential NYC evacuation zones. You can also call 311 and give your address to check if you are in an area which may be under evacuation on Saturday morning.The MTA battle plan, created in 2007, but still valid today, says the worst possible scenario is a hurricane making landfall at Atlantic City, 100 miles south of the city. Hurricanes spin counter-clockwise, so a big storm making landfall to the south would push a wall of ocean water onto New York.
Federal scientists say a Category 2 hurricane could drive a 20-foot storm surge into Manhattan, Queens and Brooklyn. If that is what appears to be looming, the MTA hurricane plan calls for bus service to begin to be curtailed at least 12 hours before landfall.
At least eight hours before landfall, the subways would start shutting down. At "zero hour" - approximately six hours before landfall, when winds reach 39 mph - all rail and bus service would be suspended, the MTA plan says.