Rainfall
Seasonal Rainfall Outlook: August-October 2021 (ASO)
Issued: 30 Jul 2021
For ASO 2021, there is an increased chance of above-normal rainfall for most of the Maritime Continent.
For ASO 2021, all three models – NCEP, ECMWF and UK Met Office (Figures 1-3) predict an increased chance of above-normal rainfall for much of the Maritime Continent, although the increased chance is only small for northern Sumatra, the Malay Peninsula, and the Philippines. The model skill for the above-normal tercile category is moderate to relatively high for much of the Maritime Continent, with higher skill where the probability of above-normal rainfall is highest in Figure 4.
For Mainland Southeast Asia, there is slight increase in chance of above-normal rainfall for northern parts of Myanmar, Lao PDR, and Vietnam, however, the model skill is only low for these regions. Elsewhere, there is also either no dominant terciles between the models or the models' skill is low for this season.
Figure 1: Rainfall tercile summary predictions of NCEP model for ASO 2021.
Figure 2: Rainfall tercile summary predictions of ECMWF model for ASO 2021 (contains modified Copernicus C3S information).
Figure 5: Average climatological rainfall's lower tercile boundary for ASO based on CHIRPS (Reference period: 1991-2020).
Figure 6: Average climatological rainfall's upper tercile boundary for ASO 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.