Mesoscale Convective Systems associated with African Easterly Waves

This study examines the mechanisms through which African easterly waves (AEWs) modulate the development of intense mesoscale convective systems (MCSs) over Africa. The spatial relationship between intense MCSs observed by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and AEWs is examined during the period of July-September 1998-2010. Particular attention is paid to the relationship between the orientation of the convective line of the MCSs relative to the low-level structure of the AEWs. In a case study of the AEW that became Hurricane Helene (2006), we examine the relationship between two intense MCSs and the low-level warm-core cyclone found northwest of the mid-level trough of the AEW. We found that the northern low-level cyclone associated with the tilted baroclinic structure of the AEW plays an important role in increasing the shear and moisture transport at low-levels favoring the development of the intense MCSs.