A composite analysis reveals that moist, cyclonic and upper-level divergence anomalies are found on average as a result of several tropical waves. The equatorial Rossby wave (ER) dominates at large scale providing a moist and convectively-active anomaly over the northern Sahel together with a smaller-scale African Easterly Wave (AEW). The Madden-Julian Oscillation provides upper-level divergence anomalies and a Kelvin wave increases convection during the EPE. Statistics show the prevalence of AEW and emphasize ER as a key driver of EPE. The co-occurrences of several tropical waves, especially those involving AEW, ER, and Kelvin waves, increase the probability of EPE. Monitoring these tropical waves combinations could improve EPEs forecasts.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023GL103715