Subseasonal Weather Outlook and Review

1.1    The Inter-monsoon season, which is characterised by winds that are light and variable in direction and diurnal shower activities, prevailed in November 2015 before transiting into the Northeast Monsoon towards the end of the month. Both the northern and southern ASEAN regions experienced increased shower activities and wet weather conditions prevailed for most parts of the month.

1.2    The El Niño strengthened further in November 2015. However, as the impact of El Niño was usually less significant during the boreal winter season, drier than usual weather conditions were experienced mainly in the Philippines. Near-normal rainfall was received mainly over the northern ASEAN region. Above-normal rainfall was also received in the near-equatorial region especially in parts of Peninsular Malaysia, Sumatra and parts of Borneo island. The regional rainfall distribution for November 2015 is shown in Figure Fig. 1A.

2.1    In the northern ASEAN region, hotspot activities continued to be subdued by shower activities. There were some isolated hotspots detected towards the end of the November 2015 as dry weather conditions in the region started to set in.

2.2    The hotspot activities in the southern ASEAN region eased gradually in November 2015 as increased shower activities over most parts of the region helped to subdue the fires. In particular, the smoke haze in Kalimantan dissipated rapidly in early November 2015 after days of persistent heavy showers over hotspot areas.

2.3    Smoke haze in Sumatra however persisted slightly longer as the showers fell mostly away from the hotspot areas. Moderate smoke haze and scattered hotspots were observed in South Sumatra and these persisted into the second week of November 2015. The haze situation improved rapidly in the second half of November with the occurrence of more showers over the southern ASEAN region. This brought an end to the Southeast Asia smoke haze event that started in late August 2015. Satellite images depicting some of the hotspot activities over the ASEAN region in October 2015 are shown in Figs. 2A to 2E.

Fig. 2E: AQUA satellite picture on 24 November 2015 shows widespread shower activities over the Borneo island.

3.1    The mature El Niño in the tropical Pacific Ocean continues to be at a strong level. The sea-surface temperatures are similar to the 1982-83 and 1997-98 strong El Niño events.

3.2    Atmospheric conditions in the ASEAN region continue to show a clear response to the strong El Niño conditions. Large-scale drier-than-normal conditions have been observed particularly in the southern and eastern parts of the ASEAN region. The consensus forecast based on assessments from international climate models and expert opinion suggests that El Niño conditions to continue through the first quarter of 2016. The strength of El Niño conditions is likely to peak in December 2015 and is expected to gradually decay in 1Q 2016.

3.3    Typically the impact of El Niño for the Southeast Asia region is drier than average rainfall conditions, especially for the southern parts of the ASEAN region during June to October. More locally-specific impact differs from place to place and for different seasons.

3.4    The region is currently in the Northeast Monsoon season (late Nov – Mar). The impact of El Niño is usually less pronounced during the Northeast Monsoon season as compared to the Southwest Monsoon season (Jun – Sep).

1.1    The Inter-monsoon season, which is characterised by winds that are light and variable in direction and diurnal shower activities, prevailed in November 2015 before transiting into the Northeast Monsoon towards the end of the month. Both the northern and southern ASEAN regions experienced increased shower activities and wet weather conditions prevailed for most parts of the month.

1.2    The El Niño strengthened further in November 2015. However, as the impact of El Niño was usually less significant during the boreal winter season, drier than usual weather conditions were experienced mainly in the Philippines. Near-normal rainfall was received mainly over the northern ASEAN region. Above-normal rainfall was also received in the near-equatorial region especially in parts of Peninsular Malaysia, Sumatra and parts of Borneo island. The regional rainfall distribution for November 2015 is shown in Figure Fig. 1A.

2.1    In the northern ASEAN region, hotspot activities continued to be subdued by shower activities. There were some isolated hotspots detected towards the end of the November 2015 as dry weather conditions in the region started to set in.

2.2    The hotspot activities in the southern ASEAN region eased gradually in November 2015 as increased shower activities over most parts of the region helped to subdue the fires. In particular, the smoke haze in Kalimantan dissipated rapidly in early November 2015 after days of persistent heavy showers over hotspot areas.

2.3    Smoke haze in Sumatra however persisted slightly longer as the showers fell mostly away from the hotspot areas. Moderate smoke haze and scattered hotspots were observed in South Sumatra and these persisted into the second week of November 2015. The haze situation improved rapidly in the second half of November with the occurrence of more showers over the southern ASEAN region. This brought an end to the Southeast Asia smoke haze event that started in late August 2015. Satellite images depicting some of the hotspot activities over the ASEAN region in October 2015 are shown in Figs. 2A to 2E.

Fig. 2E: AQUA satellite picture on 24 November 2015 shows widespread shower activities over the Borneo island.

3.1    The mature El Niño in the tropical Pacific Ocean continues to be at a strong level. The sea-surface temperatures are similar to the 1982-83 and 1997-98 strong El Niño events.

3.2    Atmospheric conditions in the ASEAN region continue to show a clear response to the strong El Niño conditions. Large-scale drier-than-normal conditions have been observed particularly in the southern and eastern parts of the ASEAN region. The consensus forecast based on assessments from international climate models and expert opinion suggests that El Niño conditions to continue through the first quarter of 2016. The strength of El Niño conditions is likely to peak in December 2015 and is expected to gradually decay in 1Q 2016.

3.3    Typically the impact of El Niño for the Southeast Asia region is drier than average rainfall conditions, especially for the southern parts of the ASEAN region during June to October. More locally-specific impact differs from place to place and for different seasons.

3.4    The region is currently in the Northeast Monsoon season (late Nov – Mar). The impact of El Niño is usually less pronounced during the Northeast Monsoon season as compared to the Southwest Monsoon season (Jun – Sep).