Interaction Between Deep Convection and African Easterly Waves using Convectively Tracked MCSs

The development of deep convection over tropical North Africa is often associated with African Easterly Waves (AEWs). Analysis of the International Satellite Cloud Climatology Product (ISCCP) Convective Tracking (CT) and ERA-Interim meridional wind datasets provided the opportunity to relate tracked MCSs and AEWs with other cloud properties such as cloud size, lifetimes and low-level shear. ISCCP CT data are produced by tracking the applicable MCS data (IR < 245 K and at least one cloud cluster of IR < 220 K) and their evolution based on an analysis of consecutive images. The most significant finding from this study is that AEWs are not only a strong modulator of tracked MCS frequencies but also a strong factor in tracked MCS size and for MCSs that last a day or longer. This MCS-conducive environment may be due to AEWs organizing the scattered convection along with existing MCSs and squall lines. Additionally, it was found that enhanced low-level convergence and low-level shear in the trough area may help to maintain the enhanced convection. Suppressed low-level shear may have a dampening effect on convection since downdrafts could be close to the MCS center while enhanced low-level shear could help extend convection with downdrafts away from the MCS center.