Subseasonal Weather Outlook and Review

Wetter conditions are predicted for central and eastern Mainland Southeast Asia and the northern half of the Philippines in Week 1 (16 – 22 September). In Week 2 (23 – 29 September), wetter conditions are predicted over much of the Maritime Continent, with the highest likelihood over the western half of the region.

Warmer than usual temperature is predicted over much of the Maritime Continent in Week 1 (16 – 22 September). These warmer conditions are predicted to ease in Week 2 (23 – 29 September), in line with the predicted wetter conditions. Elsewhere, warmer than usual temperature is predicted over southern Mainland Southeast Asia in Week 2.

No clear Madden-Julian Oscillation (MJO) signal was present during the second week of September, based on the RMM index. Most models predict an MJO signal to strengthen over the Maritime Continent (Phase 5), before propagating to the Western Pacific (Phase 6) by the start of Week 1. Most models predict this signal to continue propagating through the Western Pacific (Phases 6 and 7) during Week 1 and become inactive during Week 2.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Wetter conditions are predicted for central and eastern Mainland Southeast Asia and the northern half of the Philippines in Week 1 (16 – 22 September). In Week 2 (23 – 29 September), wetter conditions are predicted over much of the Maritime Continent, with the highest likelihood over the western half of the region.

Warmer than usual temperature is predicted over much of the Maritime Continent in Week 1 (16 – 22 September). These warmer conditions are predicted to ease in Week 2 (23 – 29 September), in line with the predicted wetter conditions. Elsewhere, warmer than usual temperature is predicted over southern Mainland Southeast Asia in Week 2.

No clear Madden-Julian Oscillation (MJO) signal was present during the second week of September, based on the RMM index. Most models predict an MJO signal to strengthen over the Maritime Continent (Phase 5), before propagating to the Western Pacific (Phase 6) by the start of Week 1. Most models predict this signal to continue propagating through the Western Pacific (Phases 6 and 7) during Week 1 and become inactive during Week 2.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.