Along the equator, the acceleration of easterly momentum is in phase with mid-tropospheric upward vertical motion, suggesting that the easterly tendency may provide upper tropospheric divergence which acts to decrease large-scale subsidence over the region. For most of the cases, the pressure gradient force is the leading source of easterly acceleration over the equatorial western Indian Ocean. However, the spatial evolution of the term suggests that the pressure gradient force does not propagate eastwards over the region, which is inconsistent with Kelvin type wave dynamics. Rather, equatorward propagation of the signal from the extratropics is associated with intrusions of mid-tropospheric cold anomalies and upper-tropospheric low-pressure anomalies likely related to extratropical Rossby wavebreaking. Thus, results demonstrate a mechanism by which extratropical signals may act to initiate MJO convection.