Westward‐Propagating Disturbances Shape Diverse MJO Propagation

Abstract Understanding eastward‐propagating mechanisms of the Madden–Julian Oscillation (MJO) is of great importance for the subseasonal prediction of extreme weather and climate worldwide. Using global satellite observations and reanalysis data, this study unravels that dual combinations of strong/weak westward‐ (ISOw) and eastward‐propagating intraseasonal oscillation (ISOe) can shape diverse MJO propagations documented previously using clustering analysis. The dry ISOw signals from the Central Pacific strengthen the leading suppressed convection over the Western Pacific (WP) and, on the contrary, weaken the moist ISOe convection over the Maritime Continent. Thus, when ISOe is weak over the WP, the strong (weak) dryness of ISOw likely causes a jump‐like (stand‐like) MJO mode. In contrast, a propagating MJO is supported when ISOe becomes strong over the WP, and a further strengthening of the ISOw dryness will presumably accelerate MJO; moreover, a weakening of ISOw might slow down the MJO speed.