Do Easterly Waves Matter for Atlantic Tropical Cyclogenesis?

In our current climate, African easterly waves (AEWs) are the primary precursors to tropical cyclones (TCs) in the Atlantic. These waves are usually abundant and only a fraction become TCs. As a result, seasonal TC genesis is not strongly constrained by AEW variability. In this study, we seek to determine whether there exists a threshold of AEW activity below which TC genesis may be robustly constrained by wave variability. We use the weather research and forecast model to simulate TC genesis over the Atlantic for selected seasons. In each case, we tune the easterly wave activity using two different methods. In one method, we alter the topography over North Africa and in the other we adjust the the initial and boundary conditions. Both methods reduce AEW activity in physically meaningful ways but do not significantly change the large scale flow. Based on these simulations, we will present statistics of TC genesis from AEW and non-AEW sources in the reduced wave activity regimes.