West African Storm Tracks and Their Relationship to Atlantic Tropical Cyclones

Author: Susanna Hopsch, C.D. Thorncroft, K. Hodges and A. Aiyyer
Date: 
June 10, 2007
Type: 
Journal Article
Venue: 
Journal of Climate
Citation: 

Hopsch, Susanna B., Chris D. Thorncroft, Kevin Hodges, Anantha Aiyyer, 2007: West African Storm Tracks and Their Relationship to Atlantic Tropical Cyclones. J. Climate, 20, 2468–2483.
doi: 10.1175/JCLI4139.1

The automatic tracking technique used by Thorncroft and Hodges has been used to identify coherent vorticity structures at 850 hPa over West Africa and the tropical Atlantic in the 40-yr ECMWF Re-Analysis. The presence of two dominant source regions, north and south of 15°N over West Africa, for storm tracks over the Atlantic was confirmed. Results show that the southern storm track provides most of the storms that reach the main development region where most tropical cyclones develop. There exists marked seasonal variability in location and intensity of the storms leaving the West African coast, which may influence the likelihood of downstream intensification and longevity.
There exists considerable year-to-year variability in the number of West African storm tracks, both in numbers over the land and continuing out over the tropical Atlantic Ocean. While the low-frequency variability is well correlated with Atlantic tropical cyclone activity, West African rainfall, and SSTs, the interannual variability is found to be uncorrelated with these. In contrast, variance of the 2–6-day-filtered meridional wind, which provides a synoptic-scale measure of African easterly wave activity, shows a significant, positive correlation with tropical cyclone activity at interannual time scales.

*Susanna conducted this research at Department of Earth and Atmospheric Sciences, University at Albany, State University of New York, Albany, New York prior to joining AER in January of 2010.