Rainfall

For September 2024, above-normal rainfall is predicted over the eastern equatorial region, based on the multi-model ensemble (Figure 4). The UK Met Office model (Figure 3) shows the highest confidence of above-normal rainfall for this region, followed by the ECMWF model (Figure 2). The NCEP model (Figure 1) predicts a higher chance of near-normal rainfall over this region. Elsewhere in the southern ASEAN region, the models disagree on the dominant tercile for the western equatorial region (the NCEP model predicts below normal rainfall while the ECMWF and UK Met Office models predict near-normal and near- to above-normal rainfall), while below-normal and near-normal rainfall are the dominant terciles for the southern part of the region. The models’ skill for the southern ASEAN region is moderate to good for predicting below- and above-normal rainfall and low to moderate for predicting near-normal rainfall.

For the northern ASEAN region, near- to above-normal rainfall is predicted for much of the region based on the multi-model ensemble, however there is some disagreement between the individual models (Figure 4). The NCEP model predicts the highest chance of above-normal rainfall over the region, apart from much of Myanmar, northern Lao PDR, and northern Viet Nam where below- to near-normal rainfall is predicted. In contrast, the UK Met Office model predicts a small increase in chance of above-normal rainfall over Myanmar and northern Lao PDR and Viet Nam, while the ECMWF model predicts a small increase in chance of above-normal rainfall for most of the northern ASEAN region. Furthermore, model skill is generally low for the northern ASEAN region at this time of the year.