Rainfall
Monthly Rainfall Outlook: December 2020
Issued: 28 Nov 2020
For December 2020, models predict above-normal rainfall over much of Southeast Asia, although an increased chance of below-normal rainfall is predicted over parts of the equatorial region.
For December 2020, near- to above-normal rainfall is predicted over much of northern ASEAN region, as seen in the multi-model ensemble (Figure 4). NCEP (Figure 1) predicts the highest probability of above-normal rainfall for this region, followed by ECMWF (Figure 2), while the UK Met Office model confines the increased chance of above-normal rainfall to the Philippines and parts of Viet Nam and Myanmar. All three models also predict above-normal rainfall for the southernmost part of the ASEAN region as well. The models’ skill is moderate for the southernmost part of the ASEAN region and the Philippines, with low to no skill over much of the rest of the northern ASEAN region.
All three models – NCEP, ECMWF and UK Met Office (Figures 1-3) predict near- to below-normal rainfall for much the equatorial region, highlighted by the increased chance of below-normal rainfall for this region in the multi-model ensemble (Figure 4). However, the models’ skill is poor to moderate for the equatorial region for this time of year.
Figure 1: Rainfall tercile summary predictions of NCEP model for December 2020.
Figure 2: Rainfall tercile summary predictions of ECMWF model for December 2020 (contains modified Copernicus C3S information).
Figure 3: Rainfall tercile summary predictions of UK Met Office model for December 2020 (contains modified Copernicus C3S information).
Figure 4: Rainfall tercile summary predictions of the multi-model ensemble for December 2020 (contains modified Copernicus C3S information).
Figure 5: Average climatological rainfall's lower tercile boundary for December based on CHIRPS (Reference period: 1981-2010).
Figure 6: Average climatological rainfall's upper tercile boundary for December 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.