Rainfall

For ASO 2023, below-normal rainfall is predicted for much of the southern ASEAN region based on the multi-model ensemble (Figure 4). The UK Met Office model (Figure 3) shows the highest confidence for below-normal rainfall over the mentioned regions, followed by the ECMWF and then the NCEP models (Figures 1 and 2). The UK Met Office model predicts below-normal rainfall over much of the southern ASEAN region, while the ECMWF and NCEP models predict below-normal rainfall over the western and central Maritime Continent, and near-normal rainfall over much of the eastern Maritime Continent. Models’ skill is moderate to good skill for below-normal rainfall and moderate to low for near-normal rainfall over the southern ASEAN region.

For the northern ASEAN region, above-normal rainfall is predicted over parts of southwestern and southeastern Mainland Southeast Asia and the Philippines, and no dominant tercile elsewhere, based on the multi-model ensemble (Figure 4). The ECMWF model (Figure 2) predicts above-normal rainfall or no dominant tercile over much of the Mainland Southeast Asia, while the NCEP and UK Met Office models (Figures 1 and 3) predict a mix of below- to above-normal rainfall over this region. Over the Philippines, the ECMWF model predicts above-normal rainfall while the NCEP and UK Met Office models predicts a mix of below- to above-normal rainfall. The models’ skill is generally low to moderate over Mainland Southeast Asia and the Philippines for all three tercile categories.