A Global Survey of Kelvin Waves and Tropical Cyclogenesis

Convectively coupled atmospheric Kelvin waves are among the most prominent sources of synoptic scale rainfall variability in the tropics, but large uncertainties surround their role in tropical cyclogenesis. It is hypothesized that Kelvin waves may promote tropical cyclogenesis in four primary ways: 1) enhancing deep moist convection; 2) generating low-level cyclonic potential vorticity through diabatic heating; 3) decreasing the vertical wind shear through their vertical circulations; and 4) providing equatorial westerly anomalies that enhance the recirculation of moisture. Each of these pathways will be most prominent in different phases of the waves. This presentation will examine how tropical cyclone activity varies by Kelvin wave phase in each basin. Wave-relative composites will show how the basic ingredients for tropical cyclone genesis and intensification are affected by these waves. Because Kelvin waves often circumnavigate the globe over the course of 1–2 weeks, the results will have implications for long-range forecasting of tropical cyclone activity.