Thomas Abdallah has seen a lot of water in his 26 years of work for New York City's transit system. In December 1992 a nor'easter storm killed the subway's power, forcing rescue crews to evacuate passengers from flooding tunnels. In August 2007 a five-inch deluge that meteorologists called an “extreme climate event” shut down the system again. So did Hurricane Irene in August 2011. Then came Hurricane Sandy.