One year ago today, the weather system that would later become Superstorm Sandy, first formed as Tropical Depression 18 in the Caribbean Sea. Before the day was out, it had strengthened into Tropical Storm Sandy, the 18th named storm of the 2012 Atlantic hurricane season.
Two days later, the storm hit Jamaica as a Category 1 hurricane, where it caused millions of dollars in damage. It re-emerged over the warm ocean waters and rapidly strengthened into a Category 3 storm, making it the second major hurricane of the season. After traveling over Cuba, Sandy was weakened, and meandered across the Bahamas, before moving parallel to the U.S. East Coast and regaining strength. It regained hurricane status and became a Category 2 storm before becoming an extratropical cyclone (one powered by the temperature difference across a storm front, instead of the warm water and convection that fuel tropical cyclones).
Sandy made landfall near Atlantic City, N.J., around 8 p.m. EDT on Oct 29, 2012. It caused significant storm surge and flooding along the Jersey coast and up through New York City and along Long Island. Sandy's surge came in part from its considerable size — it was the second largest Atlantic tropical cyclone on record. (Tropical cyclone is the generic term used to describe hurricanes, typhoons and tropical storms.)