The Influence of the Mid-Tropospheric Circulation on Developing and Nondeveloping African Easterly Waves: A Case Study

It is well known that most of the Atlantic tropical cyclones (TCs) form in association with African Easterly Waves (AEWs). However, not all AEWs spawn into a tropical storm. We do not have a conclusive understanding why some initiate TCs and some don’t. Different AEWs with similar amplitude or intensity as they leave off the African coast and propagate into the Atlantic would not have similar impact on tropical cyclo-genesis (TC-genesis). The reason for this is less well understood. We followed a case study approach to compare and contrast the environment of three different AEWs that crossed the coast of west Africa but have different fates with respect of their role in TC-genesis. The selected waves show similar intensity as measured by their relative vorticity at the time of crossing coastal Africa. Despite this, one wave developed into a named TC, one developed into a tropical depression (TD) and decayed later, and the third one did not have a role on TC-genesis at all. We will present the evolution of a wave activity and associated convective activity to shed light into why similar intensity waves have different roles. We will also present results to show the wave-convection interaction. Additional analysis comparing the mid-tropospheric environment of the three AEW cases and their relationship to TC-genesis will also be presented. This study is done by using MERRA and CLAUS datasets.