Subseasonal Weather Outlook (18 September – 1 October 2023)

Issued: 15 September 2023
First forecast week: 18 September – 24 September 2023
Second forecast week: 25 September – 1 October 2023


Figure 1: Rainfall Outlook


Figure 2: Temperature Outlook


Wetter conditions are predicted over the parts of the equatorial region, including the northwestern Maritime Continent, northern Borneo and the southern Philippines in Week 1 (18 – 24 September). Wetter conditions are also predicted over southern Mainland Southeast Asia in Week 2 (25 September – 1 October).

Drier conditions are predicted over most of the southern Maritime Continent in Week 1 (18 – 24 September). These drier conditions are predicted to extend northwards during Week 2 (25 September – 1 October) to cover much of the southern ASEAN region.

Warmer than usual temperature is predicted over much of Mainland Southeast Asia in the next fortnight (18 September – 1 October). In Week 1 (18 – 24 September), warmer than usual temperature is predicted to develop over parts of the equatorial region. By Week 2 (25 September – 1 October), warmer temperature is predicted over much of the southern ASEAN region, in line with the predicted drier conditions.

By the middle of September, there was no clear Madden-Julian Oscillation (MJO) signal. Most models predict no significant MJO activity during the forecast period.

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.