Rainfall

For January’s rainfall, all three models – NCEP CFSv2, ECMWF and the UK Met Office (Figures 1-3) predict near-normal to above-normal conditions over much of the equatorial region (around Sumatra, Peninsular Malaysia, Borneo, Sulawesi, and Papua). The spatial extent and magnitude of the likelihood for above-normal conditions differ across the different models. In particular, for the UK Met Office model, the likelihood for above-normal rainfall is higher than ECMWF or NCEP CFSv2 models. Also for the NCEP CFSv2 model, above-normal conditions are mainly confined to western Maritime Continent. It should be noted that there is only low to moderate skill for the equatorial region in January across models.

For southern Philippines, the three models favour below-normal rainfall and for this region the models’ skill are good. For the southernmost part of the region, NCEP CFSv2 model predicts below-normal rainfall over eastern Java and Sulawesi, with the ECMWF and UK Met Office models confining the below-normal rainfall only to the south, and extending to the region around Java. The disagreement between the models indicates a lower confidence in the below-normal rainfall for this region compared to over southern Philippines.

For the rest of the Southeast Asia region, the model skill is either low, or there is no dominant tercile from the three models.

Figure 1: Rainfall tercile summary predictions of NCEP model for January 2019.