The Impact of Tropical Cyclones on Drought Alleviation in the Atlantic and Gulf Coasts

Hill, C. M., Fitzpatrick, P. J., Jiang, H., Klotzbach, P. J., Lau, Y. H., & Roth, D. (2012). The Impact of Tropical Cyclones on Drought Alleviation in the Atlantic and Gulf Coasts. 30th Conference on Hurricanes and Tropical Meteorology. Ponte Vedra Beach, FL.

Tropical cyclones have been established as a significant source of precipitation for the eastern United States (e.g. Noguiera and Keim 2010). Tropical cyclones provide enough rainfall capable of alleviating ongoing drought conditions in a given area, yet not since Sugg (1968) has a study been published to directly associate tropical cyclone rainfall with the termination of drought events across the eastern United States. The Palmer Drought Severity Index (PDSI) is used in this study to assess the state of the local precipitation budget of coastally based climate divisions, as defined by the National Climatic Data Center (NCDC). Events of significant drought alleviation are identified during June through November, over the period of 1960 to 2010, in which the monthly PDSI has increased by one or more units from an original value of -2 or less, representing an alleviation of moderate, severe, or extreme drought conditions. Records of tropical cyclone rainfall, compiled by the Hydrological Prediction Center (HPC), are compared against the drought alleviation events to determine the extent to which tropical cyclones contribute to the alleviation of drought conditions at the local and regional scale. Preliminary, tropical cyclones are found to alleviate an average of 20-30% of drought events observed within some coastal climate divisions. Specific case events in which one or more tropical cyclones are found to have terminated a drought event will be highlighted in a manner analogous to that of Sugg (1968). Statistics specifying the climatological impact of tropical cyclones to drought conditions at individual climate divisions over the period of 1960 to 2010 will be presented. Noguiera, R. C., and B. D. Keim, 2010: Annual volume and area variations in tropical cyclone rainfall over the eastern United States. J. Climate, 23, 4363-4374. Sugg, A. L., 1968: Beneficial aspects of the tropical cyclone. J. Appl. Meteor., 7, 39-45