THE EFFECT OF THE MADDEN-JULIAN OSCILLATION ON THE PROBABILITY OF RAPID INTENSIFICATION OF TROPICAL CYCLONES IN THE GULF OF MEXICO AND CARIBBEAN

Abstract

This thesis seeks to identify a relationship between the phase of the Madden Julian Oscillation (MJO) and the probability of rapid intensification (RI) of tropical cyclones (TCs) in the Gulf of Mexico and the Caribbean Sea. The following methods were used to investigate the effect of the MJO on the likelihood of RI in the Gulf and Caribbean: the probabilities of TCs undergoing RI in the Gulf of Mexico and Caribbean (and in the entire North Atlantic) were calculated for each phase of the MJO (using the eight-phase index developed by Wheeler and Hendon 2004). Phases 2 and 8 exhibited enhanced probabilities of RI in the Gulf of Mexico and Caribbean (and the entire North Atlantic). The probabilities of TC genesis were also calculated for each MJO phase in the Gulf of Mexico and Caribbean (and the North Atlantic) in order to determine whether the increased probability of RI in certain phases is mostly attributable to an increased probability of TC genesis or whether other environmental conditions largely independent of genesis are responsible for enhanced RI in certain phases. Additionally, vertical wind shear anomaly maps, outgoing longwave radiation (OLR) anomaly maps, sea surface temperature (SST) anomaly maps, and maps of the temperature anomaly at 250 hPa were made for each phase of the MJO in order to determine which large-scale conditions affected RI the most and whether there was a constructive relationship between wind shear and OLR for certain phases. None of these variables explains the MJO’s modulation of RI, although there is a constructive relationship between negative OLR anomalies, negative wind shear anomalies, and positive SST anomalies in phase 2 that (at least partially) explain its high probability of RI. Finally, relationship between the Madden Julian Oscillation and the El Niño Southern Oscillation (ENSO) was briefly discussed. Diverging theories about how ENSO is expected to change with warming were introduced, and future projections of the MJO were made (using bandpass-filtered variances of OLR and monthly SST climatology maps) and analyzed in the context of the relationship between the MJO and ENSO.