Rainfall
Seasonal Rainfall Outlook: June-August 2021 (JJA)
Issued: 31 May 2021
For JJA 2021, there is a small increase in chance of above-normal rainfall over parts of the southwestern Maritime Continent.
For JJA 2021, no dominant tercile for rainfall is predicted for much of the ASEAN region as seen from the multi-model ensemble (Figure 4) and the disagreement between the models (Figures 1 – 3).
For the Maritime Continent, a small increase in chance of above-normal rainfall is predicted for parts of the Maritime Continent, particularly the southwestern region. Elsewhere, the NCEP (Figure 1) and ECMWF (Figure 2) models predict an increase chance of above-normal rainfall in the northeastern part of the Maritime Continent, while the UK Met Office (Figure 3) model predicts and increased chance over the central and southeastern part. The model skill is low to moderate for the western Maritime continent, and moderate to high for the central and eastern Maritime Continent.
For Mainland Southeast Asia overall, there is either no dominant tercile or disagreement between the models. The models’ skill is low for Mainland Southeast Asia for this season.
Figure 1: Rainfall tercile summary predictions of NCEP model for JJA 2021.
Figure 2: Rainfall tercile summary predictions of ECMWF model for JJA 2021 (contains modified Copernicus C3S information).
Figure 5: Average climatological rainfall's lower tercile boundary for JJA based on CHIRPS (Reference period: 1981-2010).
Figure 6: Average climatological rainfall's upper tercile boundary for JJA based on CHIRPS (Reference period: 1981-2010).
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.