Development of Shallow Convection and the Slow Eastward Propagation of Super Cloud Clusters in the Madden‐Julian Oscillation

Abstract Eastward‐propagating super cloud clusters (SCCs) are the primary convective features of the Madden‐Julian Oscillation (MJO) envelope and play a crucial role in determining its propagation speed. While the dynamical structures of SCCs resemble those of typical Kelvin waves, their phase speeds are much slower. This study investigates the physical processes underlying the eastward propagation of SCCs using a cloud‐permitting simulation of an MJO event over the tropical Indian Ocean. The results show that the eastward propagation of SCCs is hindered due to intersections with westward‐propagating waves originating from the western edge of the Maritime Continent. During these intersections, new cloud clusters, dominated by shallow convection, are triggered to the east. This shallow convection temporarily stalls the SCC due to positive feedback between shallow convective heating and moisture convergence. As shallow convection transitions to deep convection and new clusters replace the old ones, the system begins to move. Latent heat release causes low surface pressure to build to the east of the new clusters, setting the stage for the next intersection. The timescale of non‐instantaneous convection‐convergence feedback, which quantifies the time lag between moisture convergence and convective heating, governs the stagnation period during cloud cluster replacement and ultimately influences the propagation speed of SCCs.