1. Review of Regional Weather Conditions in May 2016
1.1 Inter Monsoon conditions prevailed in May 2016 and shower activities returned to most parts of the ASEAN region as El Niño conditions in the equatorial Pacific Ocean continued to further weaken in May 2016.
1.2 Diurnal shower activities and light wind conditions prevailed on most days in both the southern and northern ASEAN regions. Around the end of May 2016, the Inter Monsoon conditions gradually transitioned to the Southwest Monsoon conditions, and a strengthening of winds over the South China Sea was observed. Shower in the region were gradually becoming less active over the Java Sea as the monsoon rain belt migrated further north.
1.3 For May 2016, most parts of the southern ASEAN region received near-normal rainfall except in parts of Kalimantan and Java Island where above-normal rainfall was received. In the northern ASEAN region, less than 100% of the normal rainfall was received mainly in Thailand, Cambodia and Lao PDR. The regional rainfall distribution for May 2016 is shown in Figure Fig. 1A.
2. Review of Land/Forest Fires and Smoke Haze Situation
2.1 Isolated hotspot activities with localised smoke haze were observed in the northern parts of Mekong sub-region and in parts of Peninsular Malaysia, in particular in early-May. An increase in the occurrence of showers in the rest of May 2016 helped to subdue hotspot activities in the ASEAN region. There was no significant transboundary haze situation.
2.3 The hotspot charts for May 2016 for
- Cambodia, Myanmar, Thailand, Lao PDR and Vietnam;
- Sumatra, Borneo and Peninsular Malaysia;
3. Status of El Niño/La Niña
3.1 The prevailing El Niño weakened further in May 2016, approaching neutral levels based on Niño3.4 sea-surface temperature (SST) readings. The large-scale atmospheric patterns, such as the trade winds near the equatorial Pacific Ocean returning to near average conditions and the cloud patterns showing less of the typical El Niño characteristics, continue to respond to the weakening of the El Niño conditions.
3.2 International climate models and expert assessment predict the end of El Niño by mid-2016. While there has yet to be consensus among experts if La Niña or neutral conditions are to occur in the second half of 2016, model outlook increasingly suggest that La Niña conditions are favored more than neutral conditions, but the possibility of neutral conditions prevailing for the rest of the year cannot be ruled out.
3.3 The ASEAN region is currently in the Southwest Monsoon season (June-September/early October), where the La-Niña is known to have considerable impact (wetness) on the western part of the Maritime Continent.