The Effects of an Active Phase of the Madden-Julian Oscillation on the Extreme Precipitation Event over Western Java Island in January 2013

An extreme precipitation/flood event that occurred in the Indonesian capital of Jakarta on Java Island in the middle of January 2013 coincided with an active phase of the Madden-Julian Oscillation (MJO) with the enhanced convective phase centered on the western Pacific. Analysis of upper-air sounding data showed that strong to moderate upper westerly to northwesterly winds persisted over the island prior to and during the heavy rain event, which were caused by the active phase of the MJO, while northwesterly winds occurred near the surface. Meteorological radar observations indicated regular genesis of convection at night over the sea to the northwest of the island, and southeastward propagation over the island from the nighttime to early morning. The movement of the precipitation systems was dominated by the upper northwesterly winds. The results suggest that the eastward propagation of an active phase of the MJO exerted a strong influence on the formation of extreme heavy rain over western Java Island.