Modulation of Atlantic Basin Tropical Cyclone Activity by the Madden-Julian Oscillation (MJO) from 1905 to 2011

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 the mid-1970s has been well documented, a newly developed 107-yr-long index for the MJO allows for additional analysis of the impacts of the MJO on Atlantic TC activity. TC activity in the Atlantic increases when MJO-related convection is enhanced over Africa and the Indian Ocean, while TC activity in the Atlantic is suppressed when the MJO enhances convection over the western Pacific. This long-term record of the MJO also allows for the analysis of how the MJO's impacts may be modulated by other climate modes, such as the El Nino-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 Nino 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 La Nina event or a warm AMO phase act to enhance the modulation of TC activity over the Atlantic basin by the MJO.