Rainfall

Based on the NCEP CFSv2 model for NDJ, there is no dominant tercile for most of the ASEAN region, indicating climatological probabilities for rainfall (Figure 1). The exception is for some southern coastal areas of Mainland Southeast Asia, including parts of southern Thailand, coastal Vietnam and Cambodia, where below normal rainfall is more likely. Other models consulted (ECMWF, UK Met Office, and JMA) show a similar area of below normal rainfall, although over a reduced area. These three models also have a consistent signal of above normal rainfall expected over the Philippines, larger than what is found in the NCEP CFSv2 model. Above normal rainfall over the Philippines and not extending further into the Maritime Continent is consistent with a weak La Niña event.

The skill of the NCEP CFSv2 model over the north-eastern parts of Southeast Asia region is generally high for this time of year (Figures 2 and 3).

Figure 1: Rainfall anomaly for NDJ 2017 – 2018.