Review of Regional Weather and Smoke Haze for Oct 2014
1. Review of Regional Weather Conditions in October 2014
1.1 The Southwest Monsoon season continued to prevail in the first half of October 2014 and gradually transitioned to the Inter-Monsoon season in the second half of the month.
1.2 Two typhoons and one tropical storm affected the north-western Pacific Ocean in October 2014, namely Typhoon Phanfone, Typhoon Vongfong and Tropical Storm Nuri. Typhoon Phanfone, developed in the last week of September 2014 and made landfall over Honshu, Japan on 04 October 2014 resulting in seven deaths and more than 62 injured. Shortly after Typhoon Phanfone made landfall, the wrath of Typhoon Vongfong swept across the islands of Kyushu and Honshu, Japan on 13 and 14 October 2014 respectively, bringing strong winds and heavy rainfall to islands. In addition, Typhoon Vongfong led to the cancellation of a few hundred flights to and from Japan.
1.3 The presence of the monsoon trough over the northern ASEAN region during the first fortnight of October 2014 enhanced convective activities there and brought more than 100% of normal rainfall to parts of the Philippines, Laos PDR, Thailand and Vietnam.
1.4 Generally wet conditions affected the southern ASEAN region during the month. Brief periods of drier weather condition were observed in parts of southern ASEAN region, in particular, in Java island, southern Kalimantan and southern Sumatra. Less than 75% of normal rainfall was received in southern parts of Kalimantan and Sumatra, Java Island and Sulawesi while more than 125% of normal rainfall was felt in northern Sumatra, Peninsular Malaysia and Sabah in East Malaysia. The regional rainfall distribution for October 2014 is shown in Fig. 1A.
2. Review of Land/Forest Fires and Smoke Haze Situation
2.1 In the northern ASEAN region, wet weather conditions continued to keep the hotspot activities subdued. In the southern ASEAN region, dry weather conditions affected mainly the southern half of Sumatra and Kalimantan during the first two weeks of October 2014 and again in the last week of October 2014. Persistent hotspots with smoke plumes and moderate to dense smoke haze were observed emanating from the hotspots in southern Sumatra and Kalimantan. The widespread smoke haze was blown by the prevailing winds which led to the deterioration in the air quality and visibility in parts of central and southern Sumatra, and Kalimantan. Smoke haze was also transported by the prevailing winds to affect parts of Peninsular Malaysia and Singapore on some days in October 2014. Satellite images depicting some of the hotspot activities in the ASEAN region in October 2014 are shown in Figs. 2A to 2E.
2.3 The hotspot charts for October 2014 for
- Cambodia, Myanmar, Thailand, Lao PDR and Vietnam;
- Sumatra, Borneo and Peninsular Malaysia;
3. Status of El Niño/La Niña
3.1 The past two months have seen steady warming of the tropical Pacific Ocean resulting in the sea-surface temperatures (SST) reaching weak El Niño levels. However the atmosphere above it has yet to respond fully, with only some atmospheric indicators (e.g. large-scale change in upper and low level winds) reaching El Niño levels. As other indicators of atmospheric response to El Niño such as cloudiness and rainfall are still within neutral thresholds, the El Niño Southern Oscillation (ENSO) is not yet considered to be fully established.
3.2 Typically the impact from El Niño for the Southeast Asia region is drier than average rainfall conditions for the southern and eastern parts of the region in June to October. More locally-specific, the impact differs from place to place and for different seasons.
3.3 During the Northeast Monsoon season, the El Niño is known to have little impact in the western part of the Maritime Continent, the possibility of a weak El Niño developing in the next one to two months is not expected to pose significant risks of extended periods of drier and warmer conditions in the ASEAN region.