Role of Multiscale Interactions within the Westerly Wind Bursts in MJO Prediction

This study reveals the critical role of multiscale interaction within the westerly wind bursts (WWBs) west of the MJO convection in modulating the prediction skill for the November MJO event during the DYNAMO (Dynamics of the Madden–Julian Oscillation) field campaign. The characteristics of the MJO convection envelope are obtained by the large-scale precipitation tracking method, and a novel metric is introduced to quantify the prediction skill for the MJO convection in the ECMWF reforecast. The ECMWF forecast exhibits approximately 17 days in skillful prediction for the MJO convection—significantly lower than that derived from the global measure. The reforecast ensembles are further classified into high and low skill catalogs based on the mean prediction skill during the observed WWBs period. High-skill ensembles exhibit significantly enhanced low-level westerlies, amplified MJO convection, and reduced spatial separation between the low-level westerlies and MJO convection during the WWBs period, indicating stronger coupling between the large-scale circulation and the convection. Mechanistic analysis reveals that enhanced westerlies in high-skill ensembles can transfer more high-frequency energy to the MJO convection through the flux convergence of interaction energy for MJO convection development, resulting in better prediction skill.