Rainfall
Monthly Rainfall Outlook: October 2021
Issued: 30 Sep 2021
For October 2021, there is an increase in chance of above-normal rainfall over central and eastern parts of the Maritime Continent, and some chance of above-normal rainfall over northeastern parts of Mainland Southeast Asia.
For October 2021, based on the multi-model ensemble (Figure 4), there is an increase in chance of above-normal rainfall over much of the Maritime Continent, apart from northern Sumatra and Peninsular Malaysia with below-normal rainfall. The ECMWF and UK Met Office models (Figures 2 and 3) have the highest likelihood of above-normal rainfall over central and eastern parts of the Maritime Continent, while the NCEP model predicts the highest likelihood over Java (Figure 1). The models’ skill is relatively high for much of the Maritime Continent, apart from northern Sumatra, the Malay Peninsula, and the Philippines where the skill is only low to moderate.
For Mainland Southeast Asia, there is disagreement between the NCEP model and the other two models, with the NCEP model predicting below-normal rainfall over much of the region while the ECMWF and UK Met Office models predicting an increase in chance of above-normal rainfall over central and eastern parts of Mainland Southeast Asia. The models’ skill is low for Mainland Southeast Asia, apart from northeastern parts of Mainland Southeast Asia where there is some moderate skill for the above-normal tercile category.
Figure 1: Rainfall tercile summary predictions of NCEP model for October 2021.
Figure 2: Rainfall tercile summary predictions of ECMWF model for October 2021 (contains modified Copernicus C3S information).
Figure 3: Rainfall tercile summary predictions of UK Met Office model for October 2021 (contains modified Copernicus C3S information).
Figure 4: Rainfall tercile summary predictions of the multi-model ensemble for October 2021 (contains modified Copernicus C3S information).
Figure 5: Average climatological rainfall's lower tercile boundary for October based on CHIRPS (Reference period: 1991-2020).
Figure 6: Average climatological rainfall's upper tercile boundary for October 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.