Tuesday, 22 January 2008: 8:30 AM
Lightning as a precursor of Atlantic hurricane activity
222 (Ernest N. Morial Convention Center)
Recent years have shown the tremendous damage and loss of life that can be caused by Atlantic Ocean hurricanes. In addition, there is evidence that the intensity and number of intense hurricanes in the Atlantic may be increasing. The majority of these hurricanes start as African Easterly Waves (AEWs) over continental West Africa. These waves form in the African Easterly Jet (AEJ) and appear to be triggered by intense thunderstorms in tropical east Africa. We have analyzed both meteorological data related to AEWs (NCEP/NCAR reanalysis) and VLF lightning data from east Africa (WWLLN). A strong connection is found between lightning activity over eastern Africa, and the AEWs that leave the west coast of Africa a week later, some of which develop into hurricanes. We have analyzed the 2005 and 2006 hurricane seasons (June-September), one a very active hurricane year (2005), and the other a very quiet year (2006). Approximately 90% of the tropical storms and hurricanes during these 2 years were preceded by periods of intense thunderstorm activity in eastern Africa, approximately 7 days prior to the AEWs entering the Atlantic Ocean. In addition, during 2006 not only was the mean east African lightning activity 23% lower than during 2005, but there was 36% less lightning over the entire African continent during the summer of 2006. We suggest the possibility that lightning activity in tropical Africa may represent an important precursor of Atlantic hurricane formation.