The Influence of African Easterly Waves on Atlantic Tropical Cyclone Tracks and Landfall in Large Ensembles
African Easterly Waves (AEWs) are an important precursor for Atlantic tropical cyclone (TC) development, with 60-80% of major hurricanes observed to originate from AEWs. However, some climate model simulations indicate that AEWs have no significant effect on annual Atlantic TC frequency, whereas others indicate that suppressing AEWs can even increase Atlantic TC frequency. Furthermore, small ensembles of simulations suggest that AEWs may influence the distribution of TC genesis location and TC environmental conditions, suggesting that AEWs may have an impact on the spatial distribution and landfall of Atlantic TCs. Here, we investigated the influence of AEWs on the spatial distribution of Atlantic TC tracks and landfall using 50-member ensembles of TC-permitting regional model simulations. The simulations were run for five hurricane seasons characterized by different levels of TC activity and by different ratios of landfalling to the total number of TCs generated from AEWs, including: two above-average seasons (2010 and 2005), two average seasons (2001 and 1996), and one below-average season (1992). The control simulations are seasonal hindcasts in which AEWs are prescribed through the eastern lateral boundary condition using reanalysis. In the experiments, we suppressed AEWs by applying a 2-10 day filter to the eastern lateral boundary condition. In response to AEW suppression, Atlantic TC seasonal frequency statistically significantly increased for both landfalling TCs (15.7-27.2%) and all TCs (10.3-26.0%) across all seasons considered. In addition, the response of TC tracks, landfall regions, and genesis locations to AEW suppression were also analyzed, with responses varying across the seasons with respect to space, time, and magnitude. Our findings indicate that suppressing AEWs not only increases seasonal Atlantic TC activity, but also influences TC tracks and increases the probability of landfall in varying regions depending on the year. Further analysis is planned to investigate how AEW suppression changes TC environmental favorability and TC steering flow and to identify physical mechanisms that can explain the increase in TC activity and landfall in response to AEW suppression. By uncovering the connections between TC precursors and the likelihood of TC genesis, landfall, and impacts, this research can provide Atlantic coastal and island communities with useful information to prepare for the risk of TCs.