Rainfall
Seasonal Rainfall Outlook: June-August 2023 (JJA)
Issued: 31 May 2023
For JJA 2023, models predict an increased chance of below-normal rainfall for much of the southern ASEAN region and above-normal rainfall over western Mainland Southeast Asia and parts of the Philippines.
For JJA 2023, below-normal rainfall is predicted for much of the southern ASEAN region based on the multi-model ensemble (Figure 4). The ECMWF and UK Met Office models show high confidence for blow-normal rainfall over the western and central Maritime Continent (Figures 2 and 3, respectively), while the NCEP model is less certain of below-normal rainfall over these regions (Figure 1). The models show moderate to good skill for below-normal rainfall over most of the southern ASEAN region.
All models predict above-normal rainfall over western Mainland Southeast Asia and parts of the Philippines (Figures 1 – 3), with low to moderate model skill for below-normal rainfall for this region. Elsewhere in the northern ASEAN region, there is disagreement between the models, although there is a slight increase in chance of above-normal rainfall over southeastern Mainland Southeast Asia based on the multi-model ensemble (Figure 4).
Figure 1: Rainfall tercile summary predictions of NCEP model for JJA 2023 (contains modified Copernicus C3S information).
Figure 2: Rainfall tercile summary predictions of ECMWF model for JJA 2023 (contains modified Copernicus C3S information).
Figure 3: Rainfall tercile summary predictions of UK Met Office model for JJA 2023 (contains modified Copernicus C3S information).
Figure 4: Rainfall tercile summary predictions of the multi-model ensemble for JJA 2023 (contains modified Copernicus C3S information).
Figure 5: Average climatological rainfall's lower tercile boundary for JJA based on CHIRPS (Reference period: 1991-2020).
Figure 6: Average climatological rainfall's upper tercile boundary for JJA based on CHIRPS (Reference period: 1991-2020).
The qualitative outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.