NASA’s 2013 Hurricane and Severe Storms Sentinel or HS3 mission will investigate whether Saharan dust and its associated warm and dry air, known as the Saharan Air Layer or SAL, favors or suppresses the development of tropical cyclones in the Atlantic Ocean. The effects of Saharan dust on tropical cyclones is a controversial area of science. During the 2012 campaign, NASA’s Global Hawk unmanned aircraft gathered valuable data on the dust layer that swirled around Tropical Storm Nadine for several days.