Rainfall
Seasonal Rainfall Outlook: October-December 2021 (OND)
Issued: 30 Sep 2021
For OND 2021, there is an increased chance of above-normal rainfall over southern and eastern parts of the Maritime Continent, and some chance of above-normal rainfall over central and eastern parts of Mainland Southeast Asia.
For OND 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, with highest likelihood over southern and eastern parts of the Maritime Continent. No dominant or below-normal terciles are predicted for the Malay Peninsula and northern Sumatra by the three models. The models’ skill is moderate to relatively high for much of the Maritime Continent, apart from northern Sumatra and the Malay Peninsula where the skill is low.
For Mainland Southeast Asia, there is a slight increase in chance of above-normal rainfall predicted by ECMWF and UKMO models for the central and eastern regions, while NCEP model is predicting above-normal rainfall for central Viet Nam and below-normal rainfall for most parts of Mainland Southeast Asia. However, the model skill for Mainland Southeast Asia is low for this season.
Figure 1: Rainfall tercile summary predictions of NCEP model for OND 2021.
Figure 2: Rainfall tercile summary predictions of ECMWF model for OND 2021 (contains modified Copernicus C3S information).
Figure 5: Average climatological rainfall's lower tercile boundary for OND based on CHIRPS (Reference period: 1991-2020).
Figure 6: Average climatological rainfall's upper tercile boundary for OND 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.