The Madden–Julian Oscillation’s Impacts on Worldwide Tropical Cyclone Activity

Abstract The 30–60-day Madden–Julian oscillation (MJO) has been documented in previous research to impact tropical cyclone (TC) activity for various tropical cyclone basins around the globe. The MJO modulates large-scale convective activity throughout the tropics, and concomitantly modulates other fields known to impact tropical cyclone activity such as vertical wind shear, midlevel moisture, vertical motion, and sea level pressure. The Atlantic basin typically shows the smallest modulations in most large-scale fields of any tropical cyclone basins; however, it still experiences significant modulations in tropical cyclone activity. The convectively enhanced phases of the MJO and the phases immediately following them are typically associated with above-average tropical cyclone frequency for each of the global TC basins, while the convectively suppressed phases of the MJO are typically associated with below-average tropical cyclone frequency. The number of rapid intensification periods are also shown to increase when the convectively enhanced phase of the MJO is impacting a particular tropical cyclone basin.