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1. Convectively Coupled Kelvin Waves and Tropical Cyclogenesis: Connections through Convection and Moisture

   https://doi.org/10.1175/MWR-D-23-0005.1  

   Lawton, Quinton A.; Majumdar, Sharanya J. (July 2023, Monthly Weather Review)

   Abstract Recent research has demonstrated a relationship between convectively coupled Kelvin waves (CCKWs) and tropical cyclogenesis, likely due to the influence of CCKWs on the large-scale environment. However, it remains unclear which environmental factors are most important and how they connect to TC genesis processes. Using a 39-yr database of African easterly waves (AEWs) to create composites of reanalysis and satellite data, it is shown that genesis may be facilitated by CCKW-driven modifications to convection and moisture. First, stand-alone composites of genesis demonstrate the significant role of environmental preconditioning and convective aggregation. A moist static energy variance budget indicates that convective aggregation during genesis is dominated by feedbacks between convection and longwave radiation. These processes begin over two days prior to genesis, supporting previous observational work. Shifting attention to CCKWs, up to 76% of developing AEWs encounter at least one CCKW in their lifetime. An increase in genesis events following convectively active CCKW phases is found, corroborating earlier studies. A decrease in genesis events following convectively suppressed phases is also identified. Using CCKW-centered composites, we show that the convectively active CCKW phases enhance convection and moisture content in the vicinity of AEWs prior to genesis. Furthermore, enhanced convective activity is the main discriminator between AEW–CCKW interactions that result in genesis versus those that do not. This analysis suggests that CCKWs may influence genesis through environmental preconditioning and radiative–convective feedbacks, among other factors. A secondary finding is that AEW attributes as far east as central Africa may be predictive of downstream genesis. Significance StatementThe purpose of this work is to investigate how one type of atmospheric wave, known as convectively coupled Kelvin waves (CCKWs), impacts the formation (“genesis”) of tropical cyclones. Forecasting of genesis remains a significant challenge, so identifying how CCKWs influence this process could help improve forecasts and give communities greater lead times. Our results show that CCKWs could temporarily make genesis more likely by increasing atmospheric moisture content and convective activity. While not all CCKWs lead to genesis, those that do are associated with a particularly strong increase in convection. This provides a potential tool for forecasters monitoring CCKWs and TC genesis in real time and motivates follow-up work on this topic in numerical models. 

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2. Global coupled dynamics of tropical easterly waves and tropical cyclone genesis

   https://doi.org/10.1038/s41612-025-01014-y  

   Du, Xueqing; Chu, Jung-Eun; Jin, Fei-Fei; Cheung, Hung Ming (December 2025, npj Climate and Atmospheric Science)

   Tropical easterly waves (TEWs) are westward-moving waves often within trade winds but occur ubiquitously in the tropics and play a significant role in the genesis of tropical cyclones (TCs). They are well-known as primary precursors of TCs in the Atlantic, yet their global relationship with TCs has been less explored. This study, for the first time, presents the global distribution of TEW activity using a combined thermodynamic and dynamic framework based on 6-hourly Outgoing Longwave Radiation and curvature vorticity. We then demonstrate that TEWs play a dominant role in approximately 22–71% of global TC genesis, with their highest impacts in the North Atlantic (71%) and Western Pacific (54%). We further identify that TEWs, in their general coupling with TC genesis dynamics, act to intensify TC convection and vorticity in all TC main development regions, albeit the vorticity enhancement is relatively weaker in the North Atlantic. To understand the cross-basin differences in this general TEW-TC relationship, we further investigated background conditions for TC genesis in each basin and found an additional dry environment constraint in the Atlantic TC genesis, yet still delineating the critical role of TEWs in TC development. 

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3. Machine Learning Approaches to Identifying Tropical Waves That Develop into Hurricanes

   Luo, Haochang; Hill, Spencer (December 2025, NeurIPS Climate Change AI Workshop)

   African Easterly Waves (AEWs) are synoptic-scale atmospheric disturbances that serve as precursors to tropical cyclones (TCs) in the North Atlantic and North Africa. As climate changes, TC activities are increasingly frequent, leading to exponentially growing socio-economic losses. So understanding the physical mechanisms governing the tropical cyclogenesis (TCG) of AEWs remains a crucial problem. Competing theoretical frameworks, including baroclinic instability, barotropic instability, and moisture-vortex instability (MVI) have been proposed, but their relative importance and temporal evolution during storm development remain unclear. In this study, machine learning algorithms are used to empirically analyze the governing mechanisms of AEW development based on 40 years of reanalysis data (1979-2018). We develop a computer vision framework utilizing convolutional neural networks (CNNs) and transformer architectures to identify developing AEWs (DAEWs) from non-developing AEWs (NDAEWs) based on wave-centered composites of key thermodynamic and dynamic variables for storm development. The model results suggest that the MVI framework is a critical factor for high classification accuracy in distinguishing developers from non-developers. 

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4. Thermodynamic Processes Governing the Evolution of Developing and Strong Nondeveloping African Easterly Waves

   https://doi.org/10.1175/JAS-D-24-0125.1  

   Mayta, Víctor C; Adames_Corraliza, Ángel F; Torres_Maldonado, Kayleen; Luo, Haochang; Núñez_Ocasio, Kelly M (June 2025, Journal of the Atmospheric Sciences)

   Abstract It is well known that African easterly waves (AEWs) can develop into tropical cyclones. However, the processes leading to development are not well understood. To this end, we examine a 38-yr climatology of AEW tracks sorted into developing AEWs (DAEWs) and strong nondeveloping AEWs (SNDAEWs). Wave-centered composites for tracks in the eastern Atlantic (40°–10°W, 5°S–30°N) and West African monsoon regions (10°W–20°E, 5°S–30°N) reveal that DAEWs occur over a more humid background state in both regions. The more humid environment causes DAEWs to exhibit heavier precipitation and wave amplification via vortex stretching. Examination of the column moist static energy (MSE) budget reveals that DAEWs exhibit stronger radiative heating and more moistening via horizontal MSE advection than SNDAEWs. The stronger horizontal MSE advection in DAEWs is due to a northeast shift in the maximum MSE relative to the wave axis, causing the northerlies in the wave to advect a higher MSE into the maximum precipitation. In contrast, MSE is maximum near the center of NDAEWs, making the moistening of the rainfall by horizontal MSE advection weaker. DAEWs exhibit stronger radiative heating per unit of rainfall relative to NDAEWs, suggesting that cloud-radiative feedbacks are stronger in these systems. The sum of horizontal MSE advection and radiative heating explains the buildup in MSE seen over the rainy region of the DAEWs that is not seen in SNDAEWs. These results underscore the importance of moisture, cloud–radiation interactions, and horizontal MSE advection in tropical cyclone (TC) development over these regions. Significance StatementAfrican easterly waves are the most common precursors of tropical cyclones in the Atlantic basin. Despite significant progress in understanding the processes that distinguish waves that develop into tropical cyclones versus those that do not, important gaps in knowledge remain. In this study, we employed a wave-centered compositing scheme and the moist static energy budget to understand the differences between easterly waves that develop and the strongest nondeveloping waves. Our results show that waves that develop into tropical cyclones occur in a more humid environment where less dry air is transported toward the wave’s rainy region. The more humid environment is also associated with stronger rainfall as well as stronger radiative heating in developing waves, the latter which favors the buildup of moisture in developing waves. Our results underscore the importance of water vapor and its horizontal distribution in determining the development of African easterly waves. 

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5. Passive versus Active Transport of Saharan Dust Aerosols by African Easterly Waves

   https://doi.org/10.3390/atmos12111509  

   Grogan, Dustin F.; Nathan, Terrence R. (November 2021, Atmosphere)

   Theory and modeling are combined to reveal the physical and dynamical processes that control Saharan dust transport by amplifying African easterly waves (AEWs). Two cases are examined: active transport, in which the dust is radiatively coupled to the circulation; passive transport, in which the dust is radiatively decoupled from the circulation. The theory is built around a dust conservation equation for dust-coupled AEWs in zonal-mean African easterly jets. The theory predicts that, for both the passive and active cases, the dust transports will be largest where the zonal-mean dust gradients are maximized on an AEW critical surface. Whether the dust transports are largest for the radiatively passive or radiatively active case depends on the growth rate of the AEWs, which is modulated by the dust heating. The theoretical predictions are confirmed via experiments carried out with the Weather Research and Forecasting model, which is coupled to a dust conservation equation. The experiments show that the meridional dust transports dominate in the passive case, while the vertical dust transports dominate in the active case. 

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