Monthly Archives: March 2019

March 31, 2019

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

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

Issued 31 March 2019

The dry conditions over the Mekong sub-region are expected to gradually ease in the first half of April 2019. More shower activities during the transitional period between the Northeast and Southwest Monsoons may help to improve the hotspot and haze situation in the sub-region. In the southern ASEAN region, hotspot activities are expected to be generally subdued although isolated hotspots may occasionally emerge during brief periods of dry weather.

Subseasonal Weather Outlook (1 Apr – 15 Apr 2019)

Subseasonal Weather Outlook (1 Apr – 15 Apr 2019)

Issued 31 Mar 2019
Valid for weeks 1 and 2: 1 Apr – 15 Apr

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Figure 1: Rainfall Outlook
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Figure 2: Temperature Outlook

During this time of year, the Northeast Monsoon season typically weakens and transitions to the inter-monsoon period, during which more shower activities over the ASEAN region can be expected.

In the second week of April 2019, drier conditions are forecast to redevelop over many areas north of the Equator, except northern Viet Nam and parts of Lao PDR, Myanmar, and Cambodia. There are no other significant regional rainfall anomalies expected during the first fortnight.

Warmer temperatures are expected over Peninsular Malaysia and most parts of the Mekong sub-region except for Myanmar, particularly in the second week.

There is currently no significant signal shown by the Madden-Julian Oscillation (MJO), and most model predictions indicated no significant MJO activity would develop in the first half of April 2019.

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.

March 26, 2019

Review of Regional Weather Conditions for First Fortnight of March 2019

Review of Regional Weather Conditions for First Fortnight of March 2019

Print Version

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

1.1 In the first fortnight of March 2019, northeasterly winds prevailed over the Philippines and the southern ASEAN region, while winds over the Mekong sub-region were light and blew mainly from the southwest. No significant wind anomalies were observed over the ASEAN region during this period. There was a gradual weakening of the northeasterly monsoonal winds during the first fortnight of the month.

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

1.2 The dry air mass that has been extending from the Pacific Ocean to the Southeast Asia region since late-January continued to bring persistent dry weather over the northern ASEAN region, as well as over parts of Peninsular Malaysia, northern and central Sumatra, and northern Borneo in the first half of March 2019. Rainfall was below-average for these areas.

1.3 In the first fortnight of March 2019, most of the rainfall fell over areas south of the equator (Figure 2). Rainfall was near-average to above-average for areas including southern Sumatra, Kalimantan, Java and the eastern archipelago of Indonesia (Figure 3).

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

Figure 3: Percent of average rainfall for 1 – 15 March 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 The Madden-Julian Oscillation (MJO) propagated through Phase 2 – 3 and contributed to increased rainfall activities observed over areas south of the equator, including southern Sumatra, Java and the eastern archipelago of Indonesia. Towards the end of the fortnight, the MJO reached Phase 4, where it rapidly weakened.

Figure 4: The MJO phase diagram (green for March 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 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 Slightly warm sea surface temperature anomalies over the Pacific Ocean are nearing El Niño levels. Sub-surface waters have become warmer than average. Nonetheless, there remained a lack of atmosphere-ocean coupling as atmospheric conditions remained largely neutral and inconsistent with El Nino conditions.

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

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

1.1 Dry conditions persisted over the northern ASEAN region, and widespread smoke haze continued to shroud many parts of the Mekong sub-region. The haze situation was on occasions exacerbated by confluence of prevailing winds with dense smoke haze from persistent hotspot activities extending over eastern Myanmar, northern and northeastern Thailand, and northern Lao PDR. Some of the smoke haze were also blown to northern Viet Nam by the southwesterly winds.

1.2 In the southern ASEAN region, dry weather over northern and central Sumatra, and Peninsular Malaysia led to the emergence of isolated but persistent hotspots with localised smoke plumes in Pahang, Peninsular Malaysia and Riau, Sumatra in the latter part of the fortnight.

Figure 1: Himawari-8 satellite image on 14 March 2019 shows widespread smoke haze over the Mekong sub-region.

Figure 2: Himawari-8 satellite image on 15 March 2019 shows isolated hotspots with smoke plumes in Peninsular Malaysia and central Sumatra.

March 15, 2019

Subseasonal Weather Outlook (16 Mar – 31 Mar 2019)

Subseasonal Weather Outlook (16 Mar – 31 Mar 2019)

Issued 15 Mar 2019
valid for weeks 3 and 4: 16 Mar – 31 Mar

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Figure 1: Rainfall Outlook
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Figure 2: Temperature Outlook

In the coming fortnight, drier-than-average conditions are expected to continue over the Philippines and the equatorial region around the South China Sea.

Wetter-than-average conditions are expected to continue over the southern Maritime Continent during Week 3 but an easing of conditions are expected in in Week 4.

The Madden-Julian Oscillation (MJO) that has been active in Phase 4 since the second week of March 2019 is weakening and is expected to weaken further in the coming fortnight. This could bring wet weather to the southern parts of the Maritime Continent, in particular over the Java and Banda Sea areas in Week 3.

The prevailing dry and warm conditions over the Southeast Asia region can be attributed to the mass of dry air from a high pressure system in the Pacific Ocean that has extended over the Southeast Asia region. The dry mass of air is forecast to persist in Week 3, and is expected to bring warmer-than-average temperatures over most parts of the Mekong sub-region, Peninsular Malaysia and northern Sumatra.

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.

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

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

Issued 15 March 2019

The Mekong sub-region has been affected by smoke haze from hotspot activities that persisted under prolonged dry conditions. In the southern ASEAN region, hotspot activities are likely to remain generally subdued due to shower activities. However, there may still be isolated hotspots with localised smoke plumes during occasional periods of dry weather.

March 8, 2019

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

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

1.1 The prolonged dry conditions in the northern ASEAN region contributed to the widespread smoke haze that continued enveloping most parts of the Mekong sub-region. Dense smoke haze was observed over parts of Cambodia, Lao PDR and Thailand during the first half of February 2019. There were also occurrences of transboundary haze as some smoke haze was blown towards Lao PDR and Viet Nam from the neighbouring countries during this period.

Figure 1: Widespread smoke haze over the Mekong sub-region

1.2 In the southern ASEAN region, localised smoke plumes were observed from isolated hotspots in Riau, Sumatra and in Johor, Peninsular Malaysia. Otherwise, hotspot activities remained generally subdued.

Figure 2: Smoke plumes from isolated hotspots in Riau, Sumatra and Johor, Malaysia

Review of Regional Weather Conditions for Second Fortnight of February 2019

Review of Regional Weather Conditions for Second Fortnight of February 2019

Print Version

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

1.1 Northeast Monsoon conditions persisted over the ASEAN region in the second half of February 2019. Northeasterly or easterly winds prevailed over the Philippines, southern Thailand and most parts of the southern ASEAN region. Over the Mekong sub-region, prevailing winds were generally blowing from the southeast or southwest, with confluence of winds over parts of the Mekong sub-region.

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Figure 1: 5000 ft average winds (left) and anomalies (right) for 16 – 28 February 2019. (Source: JMA)

1.2 A confluence of winds typically favours shower activity development, but weather over the Mekong sub-region remained dry mainly due to the presence of dry air mass that has extended from the Pacific Ocean over the Southeast Asia region. Elsewhere in the ASEAN region, rainfall distribution over the fortnight was also likely associated with the Madden – Julian Oscillation (MJO) which transitioned from phase 8 to phase 2 . Well below-average rainfall was recorded in the Philippines, Peninsular Malaysia, Sabah, western Kalimantan and parts of Java, while above-average rainfall was received in other parts of the southern ASEAN region.

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

Figure 3: Percent of average rainfall for 16 – 28 February 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)

Figure 4: The MJO phase diagram (green for February 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 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)

March 7, 2019

ASMC Bulletin (Issue #3, Mar 2019)

ASMC Bulletin (Issue #3, Mar 2019)