December 21, 2018
1.1 Isolated hotspots with smoke plumes were observed in the Mekong sub-region due to persistent dry conditions (Figures 1 and 2). In the southern ASEAN region, hotspot activities remained generally subdued.
Figures 1: Localised smoke haze around hotspots in Thailand in early December 2018
Figures 1: Smoke haze from hotspot cluster in Cambodia on 14 December 2018
1.1 Northeast Monsoon conditions prevailed over the ASEAN region in the first half of December 2018. In the northern ASEAN region, weather was generally dry. Prevailing winds blew mainly from the northeast or east in general except in Myanmar, where winds were more variable. In the southern ASEAN region, winds were generally light and variable except for the moderate to strong northeasterly winds over parts of Malaysia. Confluence of winds along the equatorial region gave rise to rainy weather and above-average rainfall in many areas.
1.2 The daily average rainfall and the percentage of average rainfall for the first fortnight of December 2018 are shown in Figures 1 and 2 respectively. The 5000ft average winds and wind anomalies in the first half of December 2018 are shown in Figures 3 and 4 respectively.
Figure 1: Daily average rainfall for the ASEAN region in the first fortnight of December 2018. (Source: JAXA Global Satellite Mapping of Precipitation)
Figure 2: Percentage of Average Rainfall for 1 – 15 December 2018. The rainfall data may be less representative for areas with a less dense rainfall network. (Source: IRI NOAA/NCEP CPC Unified Precipitation Analyses)
Figure 4: 5000 ft average winds (left) and anomalies (right) for 1 – 15 December 2018. (Source: JMA)
1.3 The Madden – Julian Oscillation (MJO) transitioned from Phase 8 to Phase 4 in the first half of December 2018, with slightly stronger amplitude of signals registered in Phase 2 to Phase 4. The stronger MJO activities in Phase 2 to Phase 4 are also associated with the rainy conditions experienced in the Indian Ocean and many parts of the southern ASEAN region.
Figure 5: The MJO phase diagram for Nov – Dec 2018 (blue for December). The diagram illustrates the movement of the MJO through different phases, which correspond to different locations along the equator. The distance of the index from the centre of the diagram is correlated with the strength of MJO. When the index falls within the circle, the MJO is considered weak or indiscernible. (Source: Bureau of Meteorology)
1.6 Although above-average sea surface temperatures persisted across the equatorial Pacific Ocean, the atmospheric indicators of El Niño – Southern Oscillation (ENSO) remained close to average. Sustained El-Niño conditions have yet been established.
As the dry season of the Mekong sub-region approached, the ASEAN Specialised Meteorological Centres (ASMC) conducted another round of the Workshop on the “Use and Interpretation of Data for Fire and Haze Monitoring” for the Mekong sub-region on 4 – 6 December 2018 in Singapore to aid preparatory efforts. The workshop brought together experts from the different sectors, such as forestry, environment, pollution control, meteorology and research – all of them part of the larger community working together to address the transboundary haze pollution issue affecting the region. Each participant brought with them invaluable experiences from their work to share with others.
Experts from the Mekong sub-region’s forestry, environment, pollution control, meteorology and research sectors attended the ASMC Workshop on the Use and Interpretation of Data for Fires and Haze Monitoring.
During the Workshop, participants were introduced to a range of products and information services availed by the ASMC for applications in the monitoring and assessment of land / forest fires and haze, as well as the scientific concepts and theories enabling such applications. These products include satellite imageries, hotspot and haze information derived from satellite data, and numerical model outputs. The Workshop also covered the interpretation of ASMC’s sub-seasonal and seasonal prediction products, and how such information could be applied in the planning. Participants were also introduced to the World Meteorological Organisation (WMO) Information System portal (WIS portal), an online data catalogue of ASMC’s products that facilitates convenient access and further downstream processing. The ASMC WIS Portal enables functions such automatic updates disseminated via email and/or File Transfer Protocol (FTP), depending on users’ preference.
Much of the Workshop focused on interactive and practical exercises to equip the participants with the skills to interpret the products and derive information that could be applied in ground operations. In addition to the lectures and exercises, participants were taken out of the classroom for technical visits to an Air Quality Monitoring station and the Central Forecast Office of the Meteorological Service Singapore (MSS). Mr Somdet Champee from the Royal Forestry Department of Thailand felt that the workshop was useful for operational staff and policy-makers alike, and commended the organisers for including relevant topics that met the learning objectives of participants.
ASMC has rolled out subseasonal-to-seasonal (S2S) prediction products for the Southeast Asia region in 2018. During the Workshop, the interpretation of S2S prediction was demonstrated using scenario-based simulations. The exercise was designed to enable participants to make informed decisions for each scenario using S2S predictions.
Interpreting satellite data requires an understanding of the basic principles of remote sensing and how satellite data are processed. The Workshop included hands-on exercises for participants to practise applying the concepts taught by interpreting satellite imageries of past haze episodes.
Interpreting satellite data requires an understanding of the basic principles of remote sensing and how satellite data are processed. The Workshop included hands-on exercises for participants to practise applying the concepts taught by interpreting satellite imageries of past haze episodes.
Training is a continuous process. As the regional centre for monitoring, assessing and providing early warning for transboundary haze, ASMC will continue to deliver capability building programmes focusing on remote sensing technologies and their applications in environmental monitoring. The aim remains to enable the community to take advantage of the advances afforded by the latest technologies through sharing of expertise and knowledge transfer.
December 14, 2018
Issued 14 December 2018
As the dry season of the northern ASEAN season has set in, occasional increases in hotspot activities and occurrence of smoke haze can be expected in parts of the Mekong sub-region during the coming fortnight. In the southern ASEAN region, hotspot activities are forecast to remain subdued.
Issued 14 Dec 2018
valid for weeks 3 and 4: 16 Dec – 31 Dec
For the first week of the fortnight, wetter-than-average conditions are forecast over southern Thailand and along coastal Myanmar due to possible tropical cyclone formation over the Bay of Bengal.
Meanwhile, the Madden-Julian Oscillation (MJO) is forecast to propagate eastwards from Phase 3 to Phase 5 and possibly further in the coming fortnight. The MJO, together with a possible Northeast Monsoon surge, is expected to bring above-average rainfall over southern Viet Nam, Cambodia, southern Thailand and northern Peninsular Malaysia in the last week of December.
In the southern ASEAN region, drier-than-average conditions are likely over Java and its surrounding vicinity in the second half of the month.
Above-average temperatures are expected in parts of Thailand, northern Lao PDR, northern Viet Nam and western Cambodia for the second half of December. Elsewhere, temperatures are likely to be near-average.
The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.
December 13, 2018
1.1 Under prevailing Northeast Monsoon conditions, dry conditions set in over the northern ASEAN region. Rainfall was generally below-average for the northern ASEAN region, except in central Philippines and southern Viet Nam where tropical storms brought heavy rains, and the northern parts of Lao PDR and Viet Nam. Most parts of the southern ASEAN region received near-average to above-average rainfall.
1.2 The rainfall distribution and the percent of average rainfall for the second fortnight of November 2018 are shown in Figure 1 and 2.
Figure 1: Daily average rainfall for the ASEAN region in the second fortnight of November 2018. (Source: JAXA Global Satellite Mapping of Precipitation)
Figure 2: Percent of Average Rainfall for 16 – 30 November 2018. The rainfall data may be less representative for areas with a less dense rainfall network. (Source: IRI NOAA/NCEP CPC Unified Precipitation Analyses)
1.3 Tropical Storm Toraji developed off the east coast Viet Nam on 18 November and made landfall in southern Viet Nam on the same day. The tropical storm was short-lived and quickly dissipated thereafter. Typhoon Usagi first developed over the western Pacific Ocean on 18 November before tracking westward across the South China Sea. Typhoon Usagi made landfall on 25 November and brought heavy rains and strong winds to southern Viet Nam and Cambodia.
1.4 North-easterly and easterly winds prevailed over the northern ASEAN region under the Northeast Monsoon. However, there were south-westerly wind anomalies over the South China Sea due to the intensification of Typhoon Usagi over the area in the last week of November.
Figure 4: 5000 ft average winds (left) and winds anomaly (right) for 16 – 30 November 2018. (Source: JMA)
1.5 The tropical Pacific Ocean’s Nino 3.4 region sea surface temperature (SST) anomalies have crossed the El Niño threshold by a small margin and are at weak El Niño levels. However, most of the atmospheric indicators of El Niño/La Niña over the tropical Pacific have yet to show sustained El Niño characteristics.
Figure 5: The MJO phase diagram for Nov 2018 (green for November). The diagram illustrates the movement of the MJO through different phases, which correspond to different locations along the equator. The distance of the index from the centre of the diagram is correlated with the strength of MJO. When the index falls within the circle, the MJO is considered weak or indiscernible. (Source: Bureau of Meteorology)
1.6 The Madden Julian Oscillation (MJO) weakened slightly but continued to propagate eastward through Phase 5 – 8 during this period. The progression of MJO through Phase 7 – 8 could have contributed to the drier-than-usual weather over some parts of the region.
1.1 Apart from the occasional increases in some parts of the Mekong sub-region (Figure 1), hotspot activities in the ASEAN region remained generally subdued.
Figures 1: NOAA-19 satellite image on 24 Nov 2018 shows isolated hotspots detected in parts of central Thailand. Typhoon Usagi was also observed in South China Sea, to the east of southern Viet Nam.
December 12, 2018
The Eleventh ASEAN Climate Outlook Forum (ASEANCOF-11) was held in Kuala Lumpur, Malaysia from 29 October – 01 November 2018. This forum was organised by the Malaysian Meteorological Department in collaboration with the ASEAN Specialised Meteorological Centre (ASMC). The ASEANCOF was started in 2013, as part of the World Meteorological Organisation/Climate Information and Prediction Services (WMO/CLIPS) project for Regional Climate Outlook Forum (RCOFs) in cooperation with National Meteorological and Hydrological Services (NMHSs). It is a platform for regional NMHSs and international partners such as the WMO Global Producing Centres (GPCs) to collaboratively develop a consensus-based seasonal climate outlook and related information on a regional scale. It also provides an avenue for NMHSs to share best practices and get updated on the latest scientific advances in seasonal predictions. The ASEANCOF-11 event was co-funded by the ASEAN Science Technology and Innovation Fund (ASTIF), World Meteorological Organization (WMO) through its partners, and Malaysian Meteorological Department.
The forum’s outlook and activities contribute significantly to one of the key roles of the ASMC, which is to conduct climate and seasonal prediction for ASEAN region through pooling the expertise of ASEAN NMHSs. The Forum also supports the activities of the Southeast Asia Regional Climate Centre Network (SEA RCC-Network) – which entered the demonstration phase on 7 November 2017 – by providing the consensus outlook as well as the platform to discuss issues on provision of climate services in the Southeast Asia region.
The forum was attended by representatives from the region’s NMHSs, i.e. Brunei, Indonesia, Lao, Malaysia, Myanmar, Philippines, Singapore, Thailand, and Vietnam who presented on their national rainfall and temperature outlook for the upcoming December 2018 – February 2019 (DJF 2018-19) boreal winter monsoon season. The NMHSs were joined by experts from the Bureau of Meteorology, Australia (BoM), China Meteorological Administration (CMA), European Centre for Medium-range Weather Forecast (ECMWF), Japan Meteorological Agency (JMA), UK MetOffice (UKMO), and the WMO Lead Center for Long Range Forecast Multi-Model Ensemble (WMO LC-LRFMME), who presented on the regional outlook from their respective models. To provide scientific basis for the outlook of DJF 2018-19, the Forum also assessed the various global and regional climatic factors that influence the DJF season in the area. In particular, the Forum took into account the influence on the climate over Southeast Asia from the El Niño Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), tropical cyclones, and the monsoon circulation patterns.
Three regional end-user agencies from the water resources management and agricultural sectors were also invited, namely, the ASEAN Hydroinformatics Data Centre (AHC), the International Rice Research Institute (IRRI), and the Mekong River Commission (MRC). The agencies shared on their activities that serve the respective communities and, in line with this year’s meeting theme, they shared on their requirements for seasonal predictions and monitoring of extreme weather and climate.
The ENSO was in warm-neutral conditions in late October 2018. There is a 70% chance for an El Niño event to develop in the season DJF 2018-19 but its intensity is unlikely to be strong, and more likely to be weak than moderate. The Indian Ocean Dipole (IOD) index was also slightly positive (warmer western Indian ocean SST, and cooler eastern Indian Ocean SST). But the IOD is predicted to be neutral in DJF 2018-19.
For monsoon activity, due to warmer conditions predicted over East Asia in the DJF 2018-19 season, a weaker high pressure system is generally expected and consequently may result in weaker northeast monsoon winds. This coupled with potential changes in the Walker Circulation due to El Niño, convective rainfall activity is expected to be relatively suppressed in general for the region in DJF 2018-2019. Typically, during El Niño events, tropical cyclone activity in the Southwest Pacific tends to be less active (less frequent). However, as the El Niño event is not expected to be a strong one, and models are not showing significantly reduced tropical cyclone activity in the DJF 2018-19; a near-normal situation is more likely.
Taking into consideration the national level forecasts, the present state of the climate, and the forecasts available from GPCs and other global centres, the forum agreed on the following consensus-based outlook for DJF 2018-19 for the Southeast Asia region:
For the upcoming boreal winter monsoon season (DJF 2018-19), below-normal conditions are favoured over parts of the Philippines, southern Vietnam, northern Laos, central and southern Myanmar, southern Thailand, and northern Borneo. Elsewhere near- to above-normal rainfall conditions are favoured, with relatively less confident probabilities.
Above-normal temperatures are favoured over much of the Southeast Asia region for the upcoming boreal winter monsoon season (DJF 2018-19). Near-normal to above-normal temperatures are favoured over southern Vietnam, Brunei, and northern-central Myanmar.
Refer to Annex A for reference on what is meant by “above, near, or below normal” in the outlook. For more information on the Northern Hemisphere winter monsoon outlook and further updates on the national scale, the relevant NMHSs should be consulted (see Annex B).
The following maps provide the probabilistic outlooks for DJF 2018-19 season in terms of tercile categories of “Above-Normal” (AN: upper tercile), “Near-Normal (NN: middle tercile) and “Below-Normal” (BN: lower tercile).
The Forum would like to convey its appreciation to the National Meteorological Services of the ASEAN Member States for sharing their national-level forecasts, the Global Producing Centres and other participating international climate modelling centres for their products and expertise made available for this Climate Outlook Forum. The Forum would also like to thank the ASEAN Secretariat, the WMO Secretariat, and the local organising committee from MMD for the administrative and funding support provided to the meeting.
December 7, 2018
Start of Dry Season for the Northern ASEAN Region
With the onset of the dry season, isolated hotspots with localised smoke plumes have been detected in the Mekong sub-region in the past few days. Based on surveillance by the NOAA-19 satellite, there were 20 and 157 hotspots detected in Mekong sub-region on 5 and 6 December 2018 respectively.
The prevailing Northeast Monsoon is expected to persist until March 2019. Occasional extended periods of dry weather may lead to an increase in hotspot activities in the northern ASEAN region during this period.
December 3, 2018
Issued 3 Dec 2018
A gradual increase of hotspot activities can be expected in the Mekong sub-region as the dry season sets in. Hotspot activities in the southern ASEAN region are expected to remain generally subdued.