A combination of warm water and weak westerly winds encourages tropical cyclones to move over land — often ending droughts — in the southeastern United States.
Justin Maxwell at Indiana University in Bloomington and his colleagues analysed climate records dating from between 1895 and 2011 for drought severity and cyclone activity. Tropical cyclones ended about 13% of the droughts in states along the Gulf coast and south Atlantic coast.
The number of drought-ending cyclones rose in the Atlantic region; the numbers did not rise significantly in the Gulf states, but the area of land relieved of drought conditions by cyclones did increase. The team suggests that the boost in such storms could be because warming surface waters in the north Atlantic Ocean increased the number of tropical cyclones over the past 100 years or so, and that those storms were more likely to make landfall when westerly winds were weak.
J. Clim. http://dx.doi.org/10.1175/JCLI-D-12-00824.1 (2013)