Modulation of Atlantic Basin Tropical Cyclone Activity by the Madden–Julian Oscillation

The Madden–Julian oscillation (MJO) has been demonstrated to play a role in tropical cyclone (TC) activity around the globe in a number of recent studies. While the impact of the MJO on TCs in the Atlantic basin since themid-1970s has beenwell documented, a newly developed 107-yr-long index for theMJO allows for additional analysis of the impacts of theMJO onAtlantic TC activity. TC activity in the Atlantic increases whenMJO-related convection is enhanced overAfrica and the IndianOcean, while TCactivity in theAtlantic is suppressed when theMJO enhances convection over the western Pacific. This long-term record of theMJOalso allows for the analysis of how the MJO’s impacts may be modulated by other climate modes, such as the El Niño–Southern Oscillation (ENSO) over interannual time scales and the Atlantic multidecadal oscillation (AMO) over multidecadal time scales. When climatologically unfavorable conditions such as an El Niño event or a negative AMO phase are present, even TC-favorable MJO conditions are not enough to generate statistically significant increases in TC activity from the long-term average across the Atlantic basin. However, climatologically favorable conditions during a LaNiña event or a warmAMOphase act to enhance themodulation of TC activity over the Atlantic basin by the MJO.