African Easterly Wave Strength and Observed Atlantic Tropical Cyclone Genesis and Characteristics
Image courtesy of Bercos-Hickey and Patricola (2024). Caption: (a) Genesis locations of Atlantic TCs with AEW origins between 1980-2020 and the curvature vorticity (CV) (s-1) at the African coast of the associated AEWs (colors); the vertical red line shows the location of 40oW. (b) Probability density function curves of developing AEW CV at the African coast for TCs that form east (purple) and west (red) of 40oW; p < 0.05 from a two-sided t-test.
African easterly waves (AEWs) are known precursors to Atlantic tropical cyclones (TCs). Many previous studies have focused on the differences between AEWs that do and do not develop into TCs, but less attention has been paid to the spectrum of only developing AEWs. This research examines how the strength of developing AEWs affects the genesis and characteristics of TCs. We found that the strength of developing AEWs is a good indicator of Atlantic TC genesis location, landfall potential and location, and the sea surface temperature during TC genesis.
TCs can have devastating impacts, and these impacts may worsen with future climate change. The development of TCs involves the co-occurrence of many factors, including an initial disturbance, which is often an AEW in the North Atlantic. In this study, we found that the strength of AEWs that develop into TCs has a statistically significant relationship with TC genesis location, landfall potential and location, and TC genesis sea surface temperatures. Weaker developing AEWs tend to develop into TCs closer to the Americas than stronger developing AEWs. Consequently, TCs that develop from weaker AEWs are more likely to make landfall due to the close proximity of their genesis locations to land. This demonstrates the importance of understanding the relationship between developing AEWs and the characteristics of their associated TCs.
In this study, we examined the relationship between the strength of AEWs that develop into Atlantic TCs and the characteristics of the associated TCs. We used the observational record and reanalysis data to examine 41-years of developing AEWs and TCs with AEW origins. An objective tracking algorithm was used to identify the developing AEWs in the reanalysis data. We found that the strength of developing AEWs is a good indicator of TC genesis location, landfall potential and location, and the sea surface temperature during TC genesis. Weaker developing AEWs tend to develop into TCs closer to the Americas in a region with warmer sea surface temperatures than those of the stronger developing AEWs, which tend to develop into TCs closer to Africa. Consequently, the TCs that develop from weaker AEWs are more likely to make landfall due to the close proximity of their genesis locations to the Americas.