Monthly Archives: December 2019

December 23, 2019

Review of Land Fires and Smoke Haze Situation for First Fortnight of December 2019

1.1 Following the onset of the dry season in the Mekong sub-region, there has been a gradual increase in the hotspot activities. Isolated hotspots with localised smoke plumes were detected in many areas in the Mekong sub-region. In Thailand, smoke haze from persistent hotspots in central Thailand was blown towards the southwest by the prevailing winds. Air quality at “Very Unhealthy” levels were reported in the Samut Sakhon and Saraburi provinces on occasions.

1.2 In the southern ASEAN region, hotspot activities were largely subdued due to the rainy weather.

Figure 1: Hotspots detected in many parts of the Mekong sub-region during the period of review. There were persistent hotspots detected in central Thailand.

Figure 2: Image from Himawari-8 satellite showing smoke haze from persistent hotspots in central Thailand and localised plumes from isolated hotspots in Cambodia, Myanmar and northeastern Thailand

Review of Regional Weather Conditions for First Fortnight of December 2019

Print Version

1. Review of Regional Weather Conditions for First Fortnight of December 2019

1.1 Northeast Monsoon conditions prevailed over the region in the first half of December 2019. A monsoon surge brought strong northeasterly winds over the South China Sea and rainy weather to the equatorial ASEAN region. Parts of Malaysia, Singapore, Sumatra and Kalimantan recorded above-average rainfall. Tropical Storm ‘Kammuri’ made landfall over the Philippines in early December and contributed to the above-average rainfall recorded there. In contrast, dry weather prevailed over the Mekong sub-region.

Figure 1: 5000 ft average winds (left) and anomalies (right) for 1 – 15 Dec 2019 (Source: JMA)

Figure 2: Daily average rainfall for the ASEAN region in the first fortnight of December 2019. (Source: JAXA Global Satellite Mapping of Precipitation)

Figure 3: Percent of average rainfall in the first fortnight of December 2019. The rainfall data is less representative for areas with a less dense rainfall network. Hatched areas indicate climatology dry mask (average daily rainfall below 1 mm). (Source: IRI NOAA/NCEP CPC Unified Precipitation Analyses)

Figure 4: Track of Tropical Storm Kammuri (Source: JAXA)

Figure 5: The MJO phase diagram (blue for December 2019). 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 correlates with the strength of MJO. MJO is weak or indiscernible when the index falls within the circle. (Source: Bureau of Meteorology)

1.2 The Madden – Julian Oscillation’s (MJO) signal was indiscernible for much of the fortnight, and was weak in Phases 2 and 3 over the last few days of the fortnight. Its contributions to the wetter conditions over the region during this period was therefore limited.

1.3 The El Niño – Southern Oscillation (ENSO) remained in its neutral state, while the positive Indian Ocean Dipole (IOD) continued to weaken over the fortnight.

December 17, 2019

First Module on Weather Prediction by Numerical Methods (18-22 Nov 2019)

First Module on Weather Prediction by Numerical Methods (18 – 22 Nov 2019)

The ASEAN Specialised Meteorological Centre (ASMC) conducted the Weather Prediction by Numerical Methods Module 1 (WPNM-M1) in Singapore from 18 to 22 November 2019, as part of its 5-year Regional Capability Building Programme rolled out in 2018. The 5-day capability building and knowledge sharing training module was attended by 18 participants from 9 ASEAN National Meteorological and Hydrological Services (NMHS) and was delivered by lecturers from the Centre for Climate Research Singapore (CCRS) and Singapore University of Social Sciences (SUSS).

Participants from the ASEAN NMHS with lecturers from CCRS and SUSS at the training module conducted by ASMC in Singapore

The objectives of the training module were to provide participants with a deep understanding of the conceptualisation, formulation and limitations of numerical weather prediction (NWP) models; to equip participants with knowledge on the governing equations used in NWP models; and to equip participants with numerical methods to solve these equations and their associated limitations.

Dr Teo Chee Kiat, a CCRS lecturer, facilitating the hands-on practical sessions using simplified models

A series of 9 lectures were conducted during the WPNM-M1, covering a wide range of topics ranging from the various approximations used in the governing equations, to various numerical methods commonly used in operational NWP systems and key considerations for operational implementation. Hands-on practical sessions were conducted using simplified models which were coded in-house by CCRS lecturers, to illustrate the concepts highlighted during the lectures and to help bridge theory with practical applications.

Overall, the training module was well-received by the participants. Almost all participants indicated interest to attend future training modules and expressed support for the continuation of the training series. Participants also commended the use of simplified models for pedagogical purposes. Plans were made to prepare a peer-reviewed publication consolidating the current and possible future NWP efforts in ASEAN.

December 16, 2019

Outlook for Land Fires and Smoke Haze Situation (16 – 31 December 2019)

Issued 16 December 2019

With the dry season prevailing over the northern ASEAN region, a gradual increase in hotspot activities can be expected. In the southern ASEAN region, hotspot activities are likely to remain subdued due to the rainy conditions.

Subseasonal Weather Outlook (16- 31 December 2019)

Subseasonal Weather Outlook (16 – 31 December 2019)

Issued 16 December 2019
Valid for weeks 1 and 2: 16 – 31 December 2019

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For the second half of December 2019, drier conditions are expected in some parts of the region, including northern Philippines, southern Viet Nam and southern Thailand. In Java, wetter conditions are expected in the last week of the month.

Most parts of the Mekong sub-region are expected to experience warmer conditions during the coming fortnight. Warmer conditions are also predicted for the areas surrounding the Java Sea, but are expected to ease in the second week of the fortnight.

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 12, 2019

Review of Regional Weather Conditions for Second Fortnight of November 2019

Print Version

1. Review of Regional Weather Conditions for Second Fortnight of November 2019

1.1 Northeast Monsoon conditions began to set in over the northern ASEAN region in mid November. Persistent north-easterly winds prevailed over the northern ASEAN region and the South China Sea. Winds to the south of the equator were light and blew mainly from the southeast.

Figure 1: 5000 ft average winds (left) and winds anomaly (right) for 16 – 30 November 2019. (Source: JMA)

1.2 Most of the rainfall fell over the equatorial region, including Brunei, Malaysia, Singapore, Sumatra and Kalimantan. Typhoon Kalmaegi, which developed over the sea areas east of the Philippines, brought heavy showers to the northern parts of Luzon between 18 – 20 November 2019. Dry weather prevailed over most parts of the Mekong sub-region during the review period.

Figure 2: Historical track of Typhoon Kalmaegi. (Source: JAXA)

1.3 Because of the dry weather in the northern ASEAN region, many parts of the Mekong sub-region experienced below-average rainfall during the review period. In the southern ASEAN region, rainfall was near-average to above-average over the equatorial region. Rainfall was below-average over the eastern archipelago of Indonesia.

Figure 3: Daily average rainfall for the ASEAN region in the second fortnight of November 2019. (Source: JAXA Global Satellite Mapping of Precipitation)

Figure 4: Percent of average rainfall for 16 – 30 November 2019. The rainfall data is less representative for areas with a less dense rainfall network. Hatched areas indicate climatology dry mask (average daily rainfall below 1 mm). (Source: IRI NOAA/NCEP CPC Unified Precipitation Analyses)

1.4 In the second half of November 2019, the Madden-Julian Oscillation (MJO) began to weaken but continued to propagate through Phase 8 – 1 into the Indian Ocean. The MJO although weak, could have contributed to the easterly wind anomalies observed over the Indian Ocean and Java Sea.

Figure 5: The MJO phase diagram for November 2019 (blue). 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)

1.5 The El-Niño Southern Oscillation (ENSO) continued to remain in the neutral state (i.e neither El Niño nor La Niña conditions). The Indian Ocean Dipole (IOD) remained in the positive phase, but was declining.

Review of Land Fires and Smoke Haze Situation for Second Fortnight of November 2019

1.1 During the second fortnight of November 2019, isolated hotspots began to emerge in the Mekong sub-region as dry weather prevailed. These hotspots were mostly short-lived. Localised smoke plumes were observed to emanate from some of the hotspots, particularly from those detected in central Thailand.

1.2 With the end of the dry season and increase in shower activities over the southern ASEAN region, hotspot activities were subdued.

Figure 1: Distribution of hotspots detected based on NOAA-20 satellite surveillance and mean winds at 2500 ft in the second fortnight of November 2019 (Source of wind data: JMA)

Figure 2: Isolated hotspots detected mainly in Thailand on 30 Nov 2019.

December 5, 2019

13th ASEAN COF (18-21 November 2019, Thailand)

Thirteenth Session of the ASEAN Climate Outlook Forum (ASEANCOF-13)

November 2019, Thai Meteorological Department in collaboration with the ASEAN Specialised Meteorological Centre (ASMC)

Consensus Bulletin for December-January-February (DJF) 2019-2020 Season

The ASEAN Climate Outlook Forum (ASEANCOF) is an avenue to collaboratively develop consensus-based seasonal climate outlooks and related information on a regional scale for Southeast Asia.

The forum outlook and its activities contribute significantly to one of the key roles of the ASEAN Specialised Meteorological Centre (ASMC), which is to conduct climate and seasonal prediction for ASEAN region through pooling the expertise of ASEAN National Meteorological Services.

The Thirteenth ASEANCOF (ASEANCOF-13) was organised by the Thai Meteorological Department in collaboration with Meteorological Service Singapore as host of the ASEAN Specialised Meteorological Centre.

Representatives from National Meteorological and Hydrological Services (NMHSs) of ASEAN Member States created a consensus forecast for the boreal winter 2019-2020 in the ASEAN region. The consensus for December-January-February (DJF) 2019-2020 outlooks was achieved through the Thirteenth ASEAN Climate Outlook Forum and Training in Bangkok, Thailand from 18 to 21 November 2019. The consensus was made based on presentations and discussions on current conditions and predictions for the Southeast Asia region. In particular, the forum took into account the significant influence of the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on the climate over Southeast Asia.

Conditions and Outlook

Recent analysis of sea surface temperature (SST) anomalies over the equatorial Pacific indicate slightly above average SSTs across most of the Pacific Ocean. The ENSO neutral conditions have been present since July 2019. The international climate outlooks predict ENSO neutral conditions are likely to continue during DJF 2019-2020. The present positive Indian Ocean Dipole (IOD) is expected to weaken in DJF 2019-2020. The Northeast monsoon for the southern half of the region is expected to be delayed due to the strong positive IOD at the start of the season.

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 2019-2020 for the Southeast Asia region:

RAINFALL

For the upcoming Northern Hemisphere winter season (December-January-February), near-normal conditions are expected over most parts of Mainland Southeast Asia, and parts of the equatorial region. However, there is a slightly enhanced probability of wetter than normal conditions over northern Vietnam, the eastern part of Malaysia, the eastern part of Celebes, Moluccas and northern part of Papua. There is a slightly increased probability of drier than normal conditions over the southern part of Myanmar, parts of Thailand (the northern, central, eastern and south-eastern of region), Philippines, northern and southern Sumatra, Java, the western part of Celebes, Bali, Nusa Tenggara, the southern part of Borneo and the southern part of Papua.

TEMPERATURE

Above normal temperatures are expected for most of Southeast Asia, apart from northern Myanmar, southern Thailand and northern Sumatra, where near normal temperatures are expected. For the regions with expected above normal temperature, the highest probability is over northern Vietnam, Lao PDR, Cambodia, northern Thailand and southern 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 Summer Monsoon outlook and further updates on the national scale, the relevant NMHSs should be consulted (see Annex B).

Consensus Maps for DJF 2019-2020

The following maps provide the probabilistic outlooks for DJF 2019-2020 season in terms of tercile categories of “Above Normal” (AN: upper tercile), “Near Normal (NN: middle tercile) and “Below Normal” (BN: lower tercile).

PROBABILISTIC RAINFALL OUTLOOK

PROBABILISTIC TEMPERATURE OUTLOOK

Meeting Documents

ASEANCOF-13 Outlook Bulletin

Acknowledgements

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 TMD for the administrative and funding support provided to the meeting.

Alert20191205 – Start of Dry Season for the northern ASEAN region

Start of dry season for the northern ASEAN region

In recent days, dry conditions have contributed to an increase in hotspot activities in the Mekong sub-region. Localised smoke plumes have also been observed emanating from some of these hotspots. Based on surveillance by the NOAA-20 satellite, there were 114 and 257 hotspots detected in the Mekong sub-region on 3 and 4 December 2019 respectively.

The prevailing Northeast Monsoon is expected to persist until March 2020, during which extended periods of dry weather may lead to further increase in hotspot activities in the Mekong sub-region.

December 3, 2019

Subseasonal Weather Outlook (1- 15 December 2019)

Issued 3 December 2019
Valid for weeks 1 and 2: 1 – 15 December 2019

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the first fortnight of December 2019, wetter conditions are expected over the western Maritime Continent, including central Sumatra, Peninsular Malaysia, Singapore and parts of western Borneo.

In Week 1, wetter conditions are forecast for the Philippines as Typhoon Kammuri continues its track northwest during the period.

Over the other parts of the ASEAN region including most parts of the Mekong sub-region and the eastern Indonesian Archipelago, it is forecast to be dry.

With a surge of cool air from the northern Asian landmass expected to blow toward the Equatorial Southeast Asia region, the Mekong sub-region, South China Sea and the surrounding areas, including Peninsular Malaysia and parts of Sumatra can expect cooler temperatures during the outlook period. In contrast, warm conditions are forecast over the Indonesian Archipelago around the Java Sea region. These conditions are expected to ease slightly in Week 2.

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.