Subseasonal Weather Outlook and Review

1.1    The Northeast Monsoon conditions prevailed in the region in January 2016. With the monsoon rain belt located between the Equator and 10 S, areas such as western Kalimantan, southern Sumatra and the Java Islands have been experiencing shower activities on most days in January 2016.

1.2    In the third week of January 2016, the northern ASEAN region experienced very cold weather conditions due to a surge of cold air from the Arctic that pushed south over East Asia and the northern ASEAN region. The very cold air outbreak brought record low temperatures to places in Vietnam and Thailand. Cities such as Hanoi and Bangkok recording recorded low of 6 degrees Celsius and 17.5 degrees Celsius respectively, which are well below the respective long-term climatological mean minimum temperatures of 15.4 and 23.9 degrees Celsius. Sa Pa, a city in the northern Vietnamese province of Lao Cai, received snowfall on 24 January 2016. In addition, the surge of cold air brought rough sea conditions in the Gulf of Thailand and Gulf of Tonkin.

1.3    Under the prevailing strong El Niño conditions, drier than usual conditions were observed in the eastern parts of ASEAN region. In near-equatorial region, including parts of Peninsular Malaysia, Sabah and Sarawak received below-normal rainfall. Most parts of Philippines also experienced drier than usual conditions. For the Mekong sub-region, near-normal to above-normal rainfall was received. The regional rainfall distribution for January 2016 is shown in Figure Fig. 1A.

2.1    In the southern ASEAN region, hotspot activities remained subdued under the prevailing wet weather conditions. However, some localised smoke haze was observed to emanate from East Kalimantan around end-January 2016.

2.2    The northern ASEAN region has entered its traditional dry season. As compared to December 2015, further escalations of hotspot activities were observed, in particular in Myanmar, Thailand, Cambodia and Vietnam. In addition, high number of hotspots was detected in Nakhon Sawan and Uthaithani in the central Thai province of Kamphaeng-Phet, and in the eastern Cambodian provinces of Ratanakiri and Mondulkiri. While these hotspots were mostly related to localised burning activities, the persistent dry weather conditions during the second half of January had led to gradual accumulation of smoke haze near the hotspot areas.

3.1    The tropical Pacific Ocean is at strong El Niño conditions in January 2016, with the sea-surface temperatures closely similar to that of the 1982-83 and 1997-98 strong El Niño events.3.2    Large-scale rainfall response to the El Niño in terms of widespread drier than usual conditions were still observed over the Southeast Asia region in January 2016. The consensus forecast based on assessments from international climate models and expert opinion suggests that the current El Niño conditions to continue through the first quarter of 2016, and is likely to weaken to Neutral conditions by around mid-2016.

3.3    The region is currently in the Northeast Monsoon season (late Nov – Mar),and the impact of El Niño is usually less pronounced as compared to the Southwest Monsoon season (Jun – Sep). Typically, El Niño will bring drier than average rainfall conditions over to the southern and eastern parts of the region but less significant impact to the northern and western parts of the region during November to March. More locally-specific impact differs from place to place and for different seasons.

1.1    The Northeast Monsoon conditions prevailed in the region in January 2016. With the monsoon rain belt located between the Equator and 10 S, areas such as western Kalimantan, southern Sumatra and the Java Islands have been experiencing shower activities on most days in January 2016.

1.2    In the third week of January 2016, the northern ASEAN region experienced very cold weather conditions due to a surge of cold air from the Arctic that pushed south over East Asia and the northern ASEAN region. The very cold air outbreak brought record low temperatures to places in Vietnam and Thailand. Cities such as Hanoi and Bangkok recording recorded low of 6 degrees Celsius and 17.5 degrees Celsius respectively, which are well below the respective long-term climatological mean minimum temperatures of 15.4 and 23.9 degrees Celsius. Sa Pa, a city in the northern Vietnamese province of Lao Cai, received snowfall on 24 January 2016. In addition, the surge of cold air brought rough sea conditions in the Gulf of Thailand and Gulf of Tonkin.

1.3    Under the prevailing strong El Niño conditions, drier than usual conditions were observed in the eastern parts of ASEAN region. In near-equatorial region, including parts of Peninsular Malaysia, Sabah and Sarawak received below-normal rainfall. Most parts of Philippines also experienced drier than usual conditions. For the Mekong sub-region, near-normal to above-normal rainfall was received. The regional rainfall distribution for January 2016 is shown in Figure Fig. 1A.

2.1    In the southern ASEAN region, hotspot activities remained subdued under the prevailing wet weather conditions. However, some localised smoke haze was observed to emanate from East Kalimantan around end-January 2016.

2.2    The northern ASEAN region has entered its traditional dry season. As compared to December 2015, further escalations of hotspot activities were observed, in particular in Myanmar, Thailand, Cambodia and Vietnam. In addition, high number of hotspots was detected in Nakhon Sawan and Uthaithani in the central Thai province of Kamphaeng-Phet, and in the eastern Cambodian provinces of Ratanakiri and Mondulkiri. While these hotspots were mostly related to localised burning activities, the persistent dry weather conditions during the second half of January had led to gradual accumulation of smoke haze near the hotspot areas.

3.1    The tropical Pacific Ocean is at strong El Niño conditions in January 2016, with the sea-surface temperatures closely similar to that of the 1982-83 and 1997-98 strong El Niño events.3.2    Large-scale rainfall response to the El Niño in terms of widespread drier than usual conditions were still observed over the Southeast Asia region in January 2016. The consensus forecast based on assessments from international climate models and expert opinion suggests that the current El Niño conditions to continue through the first quarter of 2016, and is likely to weaken to Neutral conditions by around mid-2016.

3.3    The region is currently in the Northeast Monsoon season (late Nov – Mar),and the impact of El Niño is usually less pronounced as compared to the Southwest Monsoon season (Jun – Sep). Typically, El Niño will bring drier than average rainfall conditions over to the southern and eastern parts of the region but less significant impact to the northern and western parts of the region during November to March. More locally-specific impact differs from place to place and for different seasons.