The Response of Atlantic Tropical Cyclones to Suppression of African Easterly Waves

Atlantic tropical cyclone (TC) genesis is strongly linked with African easterly waves (AEWs) on the synoptic timescale. However, the TC – AEW relationship is unclear on interannual to climate timescales, and it is unknown whether TCs are limited by AEWs. We investigated the impact of AEW suppression on seasonal Atlantic TC activity using a 10-member ensemble of regional climate model simulations in which AEWs were either prescribed or removed through the lateral boundary condition. The climate model experiments produced no significant change in seasonal Atlantic TC number, indicating that AEWs are not necessary to maintain climatological basin-wide TC frequency even though TCs readily originate from these types of disturbances. This suggests that the specific type of “seedling” disturbance is unimportant for determining basin-wide seasonal Atlantic TC number, and that in the absence of AEWs, TCs will generate by other mechanisms. The results imply that changes in AEW activity are not reliable predictors of seasonal variability and future change in Atlantic TC frequency.