Monthly Archives: May 2019

May 31, 2019

12th ASEAN COF (May 2019, Online Correspondence)

Twelfth Session of the ASEAN Climate Outlook Forum (ASEANCOF-12)

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

Consensus Bulletin for June-July-August (JJA) 2019 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.

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 Twelfth ASEANCOF (ASEANCOF-12) 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 Summer Monsoon 2019 in the ASEAN region. The consensus for June-July-August (JJA) 2019 outlooks was achieved through online correspondence. The consensus was made based on completed questionnaires regarding current conditions and predictions for the Southeast Asia region as well as an online discussion. 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 system over Southeast Asia.

Conditions and Outlook

Recent analysis of Sea Surface Temperature (SST) anomalies over the Equatorial Pacific indicate above average SSTs across most of the Pacific Ocean. Borderline El Niño conditions have been present since SON 2018. The international climate outlooks predict El Niño conditions are likely to continue during JJA 2019. The present neutral Indian Ocean Dipole (IOD) is expected to develop into a positive IOD in JJA 2019 and the later part of the year.

The Summer Monsoon is predicted to be normal throughout Southeast Asia. As such, near normal occurrence of tropical cyclones is expected over the Bay of Bengal. Due to the prediction of a normal Summer Monsoon along with El Niño conditions, the occurrence of tropical cyclones in the Philippines is expected to be below normal.

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 JJA 2019 for the Southeast Asia region:

RAINFALL

For the upcoming Northern Hemisphere Summer Monsoon season (June-July-August), below normal conditions are expected over most parts of the Southeast Asia. However, there is a slightly enhanced probability of wetter than normal conditions over western and southern Myanmar and parts of Sumatra, Northern Celebes, Moluccas, and Papua islands of Indonesia.

TEMPERATURE

Above normal temperatures are expected over much of central and eastern Southeast Asia, including parts of Peninsular Malaysia, Singapore, central and western Indonesia. Normal to above normal temperature are expected elsewhere, including Philippines, Moluccas and Papua islands of Indonesia.

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 JJA 2019

The following maps provide the probabilistic outlooks for JJA 2019 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-12 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.

May 23, 2019

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

1.1 The first half of May saw a gradual improvement in the fire and smoke haze situation over the Mekong sub-region. Some smoke haze was observed over parts of Myanmar and the northern parts of Thailand and Lao PDR early in the month. With an increase in scattered shower activities over the northern parts of the Mekong sub-region, no significant smoke haze was observed.

1.2 In the southern ASEAN region, hotspot activities remained generally subdued although there were isolated hotspots with localised plumes in West Kalimantan and Sarawak during brief periods of dry weather.

Figure 1: Smoke haze in Myanmar and the northern parts of Thailand and Lao PDR in early May 2019

Figure 2: Localised smoke haze confined within Myanmar

Figure 3: Localised smoke plumes from isolated hotspots in Sarawak and West Kalimantan

Review of Regional Weather Conditions for First Fortnight of May 2019

Print Version

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

1.1 Under inter-monsoon conditions, the prevailing winds over the equatorial region were mostly light and variable in direction over the past fortnight. Over the northern ASEAN region, there were anomalous westerly winds (Figure 1).

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

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

Figure 3: Percentage of average rainfall for 1 – 15 May 2019. The rainfall data may be less representative for areas with a less dense rainfall network. (Source: IRI NOAA/NCEP CPC Unified Precipitation Analyses)

1.2 There were scattered showers over the region in the first half of May (Figure 2), with the exception of Myanmar where generally dry weather prevailed. Myanmar and the northern parts of Lao PDR and Thailand received below-average rainfall, which could have been due to dry air from the Bay of Bengal that persisted over these areas early in the month. Many areas along the equatorial region (including southern parts of Peninsular Malaysia, Sumatra, and Borneo) received below-normal rainfall (Figure 3), and this could in part be attributed to the Madden-Julian Oscillation (MJO) activities from Phase 5 to Phase 8 during the fortnight.

Figure 4: The MJO phase diagram for March 2019-May 2019 (green for April). 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)

1.3 In the first half of May, although there was a slight cooling of the sea surface, the sea surface temperatures of the equatorial Pacific Ocean remained warmer than average. There was no consistent coupling between the sea surface temperatures and the atmosphere, indicating that full-fledged El Niño conditions have not developed.

May 16, 2019

Alert20190516 – End of Dry Season for the Northern ASEAN Region

End of Dry Season for the Northern ASEAN Region

There have been scattered showers over the northern ASEAN region in the past week. Based on surveillance by the NOAA-19 satellite, the total hotspot count in the Mekong sub-region remained low, with 20 and 47 hotspots detected on 14th May 2019 and 15th May 2019 respectively.

With rainy conditions forecast to persist over the northern ASEAN region, hotspot activities are expected to remain generally subdued.

May 15, 2019

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

Issued 15 May 2019

Hotspot activities in the ASEAN region are expected to remain generally subdued during this period. However, isolated hotspots with localised smoke haze can be expected during periods of dry weather.

Subseasonal Weather Outlook (16 – 31 May 2019)

Subseasonal Weather Outlook (16 May – 31 May 2019)

Issued 15 May 2019
Valid for weeks 3 and 4: 16 May – 31 May

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For the second half of May, drier-than-usual conditions are expected to persist in Myanmar, the southern Philippines, as well as northern and central Thailand. By the second week of the fortnight, the drier conditions are expected to extend over most parts of the northern ASEAN region.

In the southern ASEAN region, wetter-than-usual conditions are expected to develop over parts of Peninsular Malaysia, Sumatra and West Kalimantan towards the middle of the fortnight, and subsequently ease in the last week of May. The wetter conditions are associated with the Madden-Julian Oscillation (MJO), which is predicted to propagate eastwards through Phase 7 and Phase 8, and into Phase 1.

Most parts of the northern ASEAN region are expected to experience warmer-than-average conditions in the coming 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.

May 13, 2019

Alert20190513 – Downgrade of Alert Level 2 to Alert Level 1 for the Mekong sub-region

Downgrade of Alert Level 2 to Alert Level 1 for the Mekong sub-region

There has been further improvement of the haze situation over the Mekong sub-region due to an increase of shower activities in the past 2 weeks. No significant smoke haze was observed over the sub-region, except for localised haze in parts of Myanmar. With rainy weather forecast to persist, the haze situation over the Mekong sub-region is expected to improve.

Based on surveillance by the NOAA-19 satellite, the total hotspot count in the Mekong sub-region has been on a declining trend, with 31 and 21 hotspots were detected on 11 and 12 May 2019 respectively.

May 2, 2019

Outlook for Land Fires and Smoke Haze Situation (1 – 15 May 2019)

Issued 1 May 2019

During the inter-monsoon period, some showers are expected over the Mekong sub-region in the coming fortnight. This may help subdue the hotspot activities, in particular over the northern Mekong sub-region, and bring some improvement to the hazy conditions there. In the southern ASEAN region, the hotspot activities are expected to remain subdued although isolated hotspots may emerge during occasional periods of dry weather.

May 1, 2019

Subseasonal Weather Outlook (1 – 15 May 2019)

Subseasonal Weather Outlook (1 May – 15 May 2019)

Issued 1 May 2019
Valid for weeks 1 and 2: 1 May – 15 May

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

May lies within the inter-monsoon period where prevailing winds over the Southeast Asia region are typically light and variable in direction. During this period, the monsoon rain band lies over the equatorial region and usually brings rainy weather over most parts of the Southeast Asia region.

In the coming fortnight, drier-than-usual conditions are expected to persist over parts of the Mekong sub-region, particularly over Myanmar. Meanwhile, wetter-than-usual conditions are forecast over the southwestern Maritime Continent, including the Java region. This is associated with the passage of Madden-Julian Oscillation (MJO) through the western Maritime Continent in Week 1. In the eastern Maritime Continent, drier-than-usual conditions are forecast to develop north of the equator in Week 1, spreading to the south of the equator in Week 2.

Warm conditions are expected to persist over most of the northern ASEAN region, as well as Peninsular Malaysia and Singapore.

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.