Monthly Archives: January 2019

January 31, 2019

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January 30, 2019

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

1.1 In the Mekong sub-region, prolonged dry weather led to an escalation of hotspot activities in Cambodia. A build-up of smoke haze was observed around persistent hotspot clusters in Cambodia and smoke haze was blown westward toward Thailand. In Thailand, isolated hotspots with localised smoke plumes were also observed. In the southern ASEAN region, hotspot activities were subdued under the prevailing wet conditions.

Figures 1: AQUA satellite image on 7 Jan 2019 shows moderate to dense smoke haze observed in Cambodia.

Figures 2: Himawari-8 satellite image on 13 Jan 2019 shows moderate smoke haze observed in Cambodia. Localized smoke plumes were also observed in the vicinity of isolated hotspots in northeastern Thailand.

Review of Regional Weather Conditions for First Fortnight of January 2019

Print Version

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

1.1 Northeast Monsoon conditions prevailed over the ASEAN region. In the Mekong sub-region, dry weather persisted over most parts of the region, except for some isolated showers that fell over coastal Viet Nam on a few days due to the strengthening of northeasterly and easterly winds over the South China Sea. Rainy conditions were also experienced in southern Thailand and northern Peninsular Malaysia due to the passage of Typhoon Pabuk during the first week of the month. This resulted in above-average rainfall over southern Thailand and northern Peninsular Malaysia.

1.2 There were scattered shower activities over the southern ASEAN region, and most parts of the region received average to above-average rainfall. However, there were some areas where below-average rainfall was received, namely parts of Malaysia, northern Sumatra, and Java.

1.3 The rainfall distribution and the percent of average rainfall for the first fortnight of January 2019 are shown in Figure 1 and 2.

Figure 1: Daily average rainfall for the ASEAN region in the first fortnight of January 2019. (Source: JAXA Global Satellite Mapping of Precipitation)

Figure 2: Percent of average rainfall for 1 – 15 January 2019. The rainfall data may be 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 northern ASEAN region, moderate to strong easterly winds prevailed over the South China Sea area. There were also anomalously southwesterly winds under the influence of the Typhoon Pabuk. In the southern ASEAN region, anomalous westerly winds were recorded.

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Figure 3: 5000 ft average winds (left) and anomalies (right) for 1 – 15 January 2019. (Source: JMA)

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Figure 4: Track of Typhoon Pabuk between 1 and 6 January 2019.

1.5 The sea surface temperature (SST) over the tropical Pacific Ocean is warmer than average, but temperatures remained in weak El Nino conditions and have weakened further. Prevailing atmospheric response, viz the cloudiness and trade winds over the tropical Pacific Ocean have remained neutral.
1.6 During the fortnight, moderate to strong Madden Julian Oscillation (MJO) signals propagated through Phase 6 – 8. The signal weakened towards the end of the second week of the fortnight. Although MJO signals in Phase 6 – 8 typically brought dry weather to the region, the MJO did not significantly influenced the weather in Southeast Asia during this period.

Figure 5: The MJO phase diagram for Jan 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)

January 28, 2019

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

Issued 26 January 2019

Hotspot activities in the Mekong sub-region are expected to remain elevated as the dry season progresses. In the southern ASEAN region, hotspot activities remained generally subdued.

Subseasonal Weather Outlook (16 Jan – 31 Jan 2019)

Issued 26 Jan 2019
valid for weeks 3 and 4: 16 Jan – 31 Jan

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Under the prevailing Northeast Monsoon condition, weather over the northern ASEAN region is expected to remain dry while scattered rain showers are expected over the southern ASEAN region.

No significant regional-scale rainfall anomaly is expected for most parts of the region, but coastal Viet Nam may experience wetter-than-normal weather in Week 3 due to a strengthening of northeasterly winds. Warmer temperatures experienced in many parts of western Southeast Asia region are expected to ease.

The MJO that has been active in the Pacific Ocean is expected to rapidly weaken by the start of the fortnight. However, it may re-emerge in the Indian Ocean or the western Maritime Continent during Week 4.

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.

January 18, 2019

Review of Regional Weather Conditions for Second Fortnight of December 2018

Print Version

1. Review of Regional Weather Conditions for Second Fortnight of December 2018

1.1 Northeast Monsoon conditions prevailed over the ASEAN region in the second fortnight of December 2018. Dry weather persisted over the Mekong sub-region, and there were occasional dry periods in parts of Sumatra and Peninsular Malaysia. Rainfall was above-average over the Philippines, and below- to near-average in the southern ASEAN region.

1.2 The rainfall distribution and the percent of average rainfall for the second fortnight of December 2018 are shown in Figure 1 and 2.

Figure 1: Daily average rainfall for the ASEAN region in the second fortnight of December 2018. (Source: JAXA Global Satellite Mapping of Precipitation)

Figure 2: Percent of average rainfall for 16 – 31 December 2018. The rainfall data may be 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)

1.3 Moderate to strong north-easterly winds prevailed over the northern ASEAN region while in the southern ASEAN region, winds were generally blowing from the west or north-west. During the period, there were westerly wind anomalies over the equatorial ASEAN region.

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Figure 4: 5000 ft average winds (left) and anomalies (right) for 16 – 31 December 2018. (Source: JMA)

1.4 The tropical Pacific Ocean’s sea surface temperature (SST) anomalies over the Nino3.4 region continue to be above El Niño threshold. However, most of the atmospheric indicators of El Niño/La Niña over the tropical Pacific remained neutral. Without the atmosphere-ocean coupling, El Niño has yet to be fully establish.

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)

1.5 There were moderate to strong Madden Julian Oscillation (MJO) signals, which propagated through Phase 4 – 5 during the review period. The MJO signals were consistent with the eastward shift of the rainfall pattern and the westerly wind anomalies observed in the region.

Review of Land Fires and Smoke Haze Situation for Second Fortnight of December 2018

1.1 Hotspot activities in the ASEAN region remained generally subdued except in Cambodia, where there were occasional increases in hotspot activities. Localised smoke plumes were observed in the vicinity of these hotspots.

Figures 1: NOAA-19 satellite image on 21 Dec 2018 shows hotspots with localised smoke plumes detected in Cambodia.

January 8, 2019

Alert20190108 – Activation of Alert Level 2 for the Mekong sub-region

Activation of Alert Level 2 for the Mekong sub-region

There has been an increase in hotspot activities in parts of the Mekong sub-region in recent days with persistent hotspot clusters and smoke haze observed in Cambodia. Isolated hotspots were also observed in Lao PDR and Thailand. Based on the NOAA-19 satellite, a total of 217 and 44 hotspots were detected in Cambodia on 7 and 8 Jan 2019 respectively.

With dry weather persisting over most parts of the Mekong sub-region in the coming days and prevailing winds blowing from the north or northeast, there could be a further escalation of hotspot activities and an increase in the risk of transboundary haze occurrence.

January 2, 2019

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

Issued 2 January 2019

An increase in hotspot activities can be expected over the Mekong sub-region as the dry season progresses. In the southern ASEAN region, hotspot activities are likely to remain generally subdued.

Subseasonal Weather Outlook (1 Jan – 15 Jan 2019)

Issued 2 Jan 2019
valid for weeks 1 and 2: 1 Jan – 15 Jan

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the first week of the fortnight, a northeast monsoon surge is expected to bring wetter conditions over the South China Sea and over coastal Thailand and Viet Nam. Elsewhere in the Mekong sub-region, cooler conditions can be expected. The stronger monsoonal winds are likely to bring wetter weather to areas around the Java Sea as well. Conversely drier conditions are expected over the Philippines.

By week 2, the wetter conditions over the South China Sea are likely to spread southward to affect the north-eastern coast of Peninsular Malaysia and southern Thailand. Areas around the Java Sea are likely to become drier during the week.

The MJO is currently active in the western Pacific Ocean and is expected to continue propagating eastward. However, the strength and speed of the MJO are uncertain.

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.