Tropical Cyclones

Tropical cyclones are low-pressure rotating weather systems that are created in the atmosphere by the transfer of heat from the ocean basins to the atmosphere. These low latitude systems (23.5 N and S of the equator) spin clockwise in the Southern hemisphere and counterclockwise in the Northern hemisphere and are referred to by different names depending on the ocean basin. In the Atlantic Ocean, they are known as tropical storms and hurricanes when the wind speed exceeds 119 km/hr, whereas in the western Pacific Ocean they are referred to as tropical cyclones and typhoons respectively. In both cases, tropical cyclones have the capability to generate very large, high waves that have the potential to devastate the natural environments of a coastal zone as well as any human infrastructure that is present where the storms make landfall. Another critically important component to understand about tropical cyclones are the storm surges, or elevated levels of sea level, that occur as these low pressure systems move through an ocean basin. Very large storm surges can be created depending upon the morphology of the coast, the gradient and width of the neighboring continental shelf, the strength of the storm and the rate of forward motion of the storm. For example, a storm surge in excess of 7 m was created along parts of the northern Gulf of Mexico shore by Hurricane Katrina in 2005 and resulted in inland flooding several kilometers from the non-storm-surge shoreline.