Hurricanes: Aren't the only tropical storm systems that warrant caution. Tropical Depression Gaston (2004) and Tropical Storms Jeanne (2004) and Floyd (1999) all caused major damage and prompted federal disaster declarations. Tropical depressions, tropical storms and hurricanes are low pressure areas that develop in the tropical regions of the ocean (between 20 degrees N latitude and the equator). These storms, called tropical cyclones, are masses of thunderstorms that organize and begin to rotate. See: Thunderstorms and Lightning