Rainfall
Monthly Rainfall Outlook: December 2021
Issued: 30 Nov 2021
For December 2021, there is an increase in chance of above-normal rainfall over the eastern Maritime Continent and southeastern Mainland Southeast Asia.
For December 2021, based on the multi-model ensemble (Figure 4), there is an increase in chance of above-normal rainfall over the eastern Maritime Continent. The highest likelihood of above-normal rainfall is over the Philippines for all three models (Figures 1 to 3). The models predict below- to near-normal rainfall over the central and western Maritime Continent with the NCEP model predicting the highest probability of below-normal rainfall. However, the model’s skill is only low to moderate for this region. Over the eastern Maritime Continent, the models’ skill is moderate to relatively high for eastern parts of the region.
For Mainland Southeast Asia, based on the multi-model ensemble (Figure 4), there is an increase in chance of above-normal rainfall over the southeastern region and below-normal rainfall over the northeastern region. Elsewhere, there is either no dominant tercile predicted or disagreement between the models. The models’ skill is generally low to moderate for Mainland Southeast Asia, with moderate skill over southeastern parts.
Figure 1: Rainfall tercile summary predictions of NCEP model for December 2021.
Figure 2: Rainfall tercile summary predictions of ECMWF model for December 2021 (contains modified Copernicus C3S information).
Figure 3: Rainfall tercile summary predictions of UK Met Office model for December 2021 (contains modified Copernicus C3S information).
Figure 4: Rainfall tercile summary predictions of the multi-model ensemble for December 2021 (contains modified Copernicus C3S information).
Figure 5: Average climatological rainfall's lower tercile boundary for December based on CHIRPS (Reference period: 1991-2020).
Figure 6: Average climatological rainfall's upper tercile boundary for December 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.