Rainfall
Seasonal Rainfall Outlook: May-July 2021 (MJJ)
Issued: 30 Apr 2021
For MJJ 2021, there is an increased chance of below-normal rainfall over parts of the western and central Maritime Continent.
For MJJ 2021, all three models – NCEP, ECMWF, and UK Met Office (Figures 1-3) – predict an increased chance of below-normal rainfall for parts of Sumatra, Peninsular Malaysia, and Borneo in the western and central Maritime Continent. The ECMWF model (Figure 2) predicts below-normal rainfall over most of Sumatra, Peninsular Malaysia, and western and central Borneo, while the UK Met Office model (Figure 3), only predicts below-normal rainfall for northern Sumatra, southern Peninsular Malaysia, and western Borneo. The NCEP model (Figure 1) shifts the highest likelihood for below-normal rainfall further south and east, covering much of the region south of the equator. The model skill for below-normal rainfall is low to moderate for the western Maritime continent, and moderate to high for the central Maritime Continent.
Elsewhere, there is either disagreement between the models (eastern Maritime Continent), or the skill is low for this season (Mainland Southeast Asia).
Figure 1: Rainfall tercile summary predictions of NCEP model for MJJ 2021.
Figure 2: Rainfall tercile summary predictions of ECMWF model for MJJ 2021 (contains modified Copernicus C3S information).
Figure 5: Average climatological rainfall's lower tercile boundary for MJJ based on CHIRPS (Reference period: 1981-2010).
Figure 6: Average climatological rainfall's upper tercile boundary for MJJ 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.