Here is a great series from the NOAA GOES 13 and GOES 15 weather satellites of the formation of Sandy October 21 as a depression in the Caribbean to become a Category 2 hurricane passing over Jamaica and Cuba then as a strong wave in the jet stream moves across the U.S, watch as it.almost grabs Sandy and turns it left into the New Jersey coast.  Two entirely seperate types of systems in the atmosphere that unfortunately combined at just the wrong time for the east coast.  From the great NASA GOES Project