Tropical cyclones (Hurricane) typically form over large bodies of relatively warm water.
  They derive their energy through the evaporation of water from the oceansurface, which ultimately recondenses into clouds and rain when moist air rises and cools to saturation.
   This energy source differs from that of mid-latitude cyclonic storms, such as nor'easters and European windstorms, which are fueled primarily by horizontal temperature contrasts.
   The strong rotating winds of a tropical cyclone are a result of the conservation of angular momentum imparted by the Earth's rotation as air flows inwards toward the axis of rotation.

   Today you see the disaster caused by Hurricane Sandy (i.s.).