Rainfall
Monthly Rainfall Outlook: October 2023
Issued: 29 Sep 2023
For October 2023, below-normal rainfall is predicted over most the southern ASEAN region.
For October 2023, below-normal rainfall is predicted over most of the southern ASEAN region, with highest likelihood over the southwestern Maritime Continent based on the multi-model ensemble (Figure 4). The ECMWF model (Figure 2) shows the highest confidence for below-normal rainfall, followed by the UKMO and the NCEP models (Figures 1 and 3). Models’ skill is moderate to good skill for below-normal rainfall over the southern ASEAN region.
For the northern ASEAN region, there is a mix of small increase in chance of below-normal rainfall to a small chance of above-normal rainfall over some of the central the region (Figure 4). A small increase in chance of above-normal rainfall is predicted over the central parts Mainland Southeast Asia in all three models (Figures 1-3). Elsewhere over Mainland Southeast Asia, as well as over the Philippines, either there is no dominant tercile or disagreement between the models (mostly eastern parts of Mainland Southeast Asia and the Philippines), or the model skill is generally low (northwestern Mainland Southeast Asia). Models’ skill for above-normal and below-normal rainfall is low to moderate for most of the northern ASEAN region.
Figure 1: Rainfall tercile summary predictions of NCEP model for October 2023 (contains modified Copernicus C3S information).
Figure 2: Rainfall tercile summary predictions of ECMWF model for October 2023 (contains modified Copernicus C3S information).
Figure 3: Rainfall tercile summary predictions of UK Met Office model for October 2023 (contains modified Copernicus C3S information).
Figure 4: Rainfall tercile summary predictions of the multi-model ensemble for October 2023 (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.