http://community.galveston.com/blogs/weather/archive/2009/07/11/the-saharan-air-layer-sal-helping-to-suppress-tropical-storm-activity.aspxTropical Storms and Hurricanes need deep layers of moist air in order to develop. That is why they only form over water and not over land. Their enegy is derived from the warm, moist, unstable air that eixsts over the tropical oceans during the summerenCommunityServer 2008 SP2 (Build: 31104.93)