Rainfall

For October’s rainfall, all three models – NCEP CFSv2, ECMWF, and the UK Met Office (Figures 1-3) predict below-normal to near-normal conditions over much of the Maritime Continent (around southern Sumatra, Kalimantan, Java, Sulawesi, Papua, and the Philippines). The spatial extent and magnitude of the likelihood for below-normal to near-normal conditions differ across the different models. In particular, for NCEP CFSv2, the likelihood for below-normal rainfall is higher than ECMWF or the UK Met Office.

In the near equatorial parts of the ASEAN region from 0°N to 10°N (Peninsular Malaysia and northern Borneo), above-normal rainfall is favoured by both the ECMWF and UK Met Office models while NCEP model expects a below-normal rainfall outlook. However, it should be noted the models’ skill is generally poor for this region at this time of the year.

The NCEP model also differs from the ECMWF and UK Met Office models for mainland Southeast Asia. While the NCEP model predicts drier conditions, the ECMWF and UK Met Office models have no strongly dominant tercile.

The models’ skill for rainfall prediction are very good over south of the equator and moderate northwards of the 10˚N stretch.

Figure 1: Rainfall tercile summary predictions of NCEP model for October 2018.