Monthly Archives: September 2018

September 25, 2018

Review of Land Fires and Smoke Haze Situation for First Fortnight of September 2018

Review of Land Fires and Smoke Haze Situation for first fortnight of September 2018

1.1 Rainy weather in the northern ASEAN region helped to keep hotspot activities in the region subdued.

1.2 In the southern ASEAN region, dry air from the southern hemisphere affected the region on some days in the first fortnight of September 2018. In the first week of the fortnight, isolated hotspots with localised smoke plumes were detected mainly in West Kalimantan. In the latter half of the fortnight, the drier weather led to an increase in hotspot activities on some days in Sumatra and Kalimantan. Hotspots with smoke plumes and haze were observed mostly in southern Sumatra and southern and central Kalimantan.

1.3 Figures below show the satellite images over the ASEAN region in the first fortnight of September 2018.

Figure 1: Aqua satellite image on 2 Sep 2018 shows localised smoke plumes in Central Kalimantan.

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Figure 2: NOAA-19 satellite image on 11 Sep 2018 shows smoke plumes from clusters of hotspots in South Kalimantan.

Figure 3: Himawari-8 satellite image on 14 Sep 2018 shows an isolated smoke plumes from hotspots in South Sumatra.

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Figure 4: Himawari-8 satellite image on 15 Sep 2018 shows smoke plumes in the provinces of South Sumatra and Lampung.

Review of Regional Weather Conditions for First Fortnight of September 2018

Print Version

1. Review of Regional Weather Conditions for First Fortnight of September 2018

1.1 Southwest Monsoon conditions prevailed in the first fortnight of September 2018. During the period, the monsoon rainband situated between latitudes 5°N and 15°N, brought rainy conditions to the northern ASEAN region. Near- to below normal rainfall was recorded over most parts of the northern ASEAN region, except for parts of Myanmar and southern Viet Nam where above-normal rainfall was received. The northern parts of Philippines received above-normal rainfall, contributed partly by the tropical storm activities during the fortnight.

1.2 In the southern ASEAN region, the incursion of dry air from the southern hemisphere brought dry conditions over most parts of the region. Most parts of the southern ASEAN region experienced below-normal rainfall, except for Peninsular Malaysia and the northern half of Sumatra where near-normal rainfall was received.

1.3 The daily average rainfall and the percentage normal of rainfall for the first fortnight of September 2018 are shown in Figure 1 and Figure 2.

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

Figure 2: Percentage of Normal Rainfall for 1 – 15 September 2018. The rainfall data may be less representative for areas with a less dense rainfall network. (Source: IRI NOAA/NCEP CPC Unified Precipitation Analyses)

1.4 During the second week of September 2018, Typhoon Mangkhut, developed over the western Pacific Ocean and tracked west to northwestwards toward the Philippines. The storm intensified rapidly into a Super Typhoon and brought heavy rains accompanied by strong winds as it made landfall over Luzon, the Philippines on 15 September 2018. The rainband associated with the Super Typhoon brought wet weather over most parts of the northern ASEAN region, northern Peninsular Malaysia and northern Sumatra.

Figure 3: Himawari-8 image on 14 September 2018 shows Super Typhoon Mangkhut over the western Pacific Ocean before it made landfall in the Philippines.

1.5 During the first half of September 2018, anomalous northwesterly winds were observed over southern Thailand and Peninsular Malaysia while over the South China Sea, slightly stronger than usual westerly winds were observed. The anomalous winds were due to the influence of Super Typhoon Mangkhut, as well as Typhoon Jebi (Typhoon Jebi developed in the Pacific Ocean and affected Japan). Figure 4 shows the average and anomalous winds at 5000 feet.

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Figure 4: 5000 ft average winds (left) and anomalies (right) for 1 – 15 September 2018. (Source: JMA)

1.6 During the period, the sea surface temperatures were observed to be warmer than average in the central and eastern Pacific Ocean, and the trade winds were observed to be slightly weaker in the western Pacific Ocean. However, the El Niño-Southern Oscillation (ENSO) continued to remain in the neutral state (neither El Niño nor La Niña).

1.7 The Madden Julian Oscillation (MJO) signal was generally weak and non-discernible during the first fortnight of September 2018, and had little or no influence on the weather in the region.

Figure 5: The MJO phase diagram for September 2018 (blue for September). 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)

September 16, 2018

Outlook for Land Fires and Smoke Haze Situation (16 – 30 Sep 2018)

Issued 16 Sep 2018

In the northern ASEAN region, hotspot activities are expected to remain subdued by the rainy weather. In the southern ASEAN region, the expected drier weather could contribute to an increased risk of hotspot activities, in particular in southern Sumatra and parts of Kalimantan, and may lead to occurrences of transboundary smoke haze in the region.

September 14, 2018

Subseasonal Weather Outlook (16 Sep – 30 Sep 2018)

Issued 14 Sep 2018
valid for weeks 3 and 4: 16 Sep – 30 Sep 2018

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the second half of September 2018, wet weather conditions and above-average rainfall are expected in the region around 10⁰ N in the third week of the month. This region is likely to return to normal conditions in the last week of September with the weakening of the Southwest Monsoon winds. For most of the southern ASEAN region, slightly drier conditions are expected.

No significant regional temperature anomalies are expected during the second half of September 2018.

No significant MJO signal is currently present. Most models predict no coherent MJO to develop during the second half of September.

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.

September 12, 2018

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

1.1 Hotspot activities remained subdued in the northern ASEAN region due to rainy weather.

1.2 In the southern ASEAN region, there were significant hotspot activities observed in Riau, Sumatra and West Kalimantan during the third week of August 2018. On 16 August 2018, visible smoke haze from fire hotspots in Riau, central Sumatra spread across the Strait of Malacca, and brought hazy conditions to parts of Peninsular Malaysia. The return of shower activities over the following days helped to improve the haze situation in Riau Province.

1.3 The hotspot activities in Kalimantan persisted for a longer period than that in Riau, central Sumatra due to an extended period of dry weather conditions over the southern half of Borneo island. Hotspots with moderate to dense smoke haze were detected in West, Central and South Kalimantan. Smoke haze from the persistent hotspots in West Kalimantan reduced visibility in Pontianak, West Kalimantan to 2 km, and was blown by the prevailing winds to affect parts of western Sarawak. In the last week of August 2018, increased shower activities over Kalimantan helped to subdue the hotspot activities there and brought some relief to the haze situation in Kalimantan and Sarawak.

1.4 Figures below show the satellite images over the ASEAN region in the second fortnight of August 2018.

Figure 1: Himawari-8 satellite image on 16 Aug 2018 shows moderate smoke haze from Riau, Sumatra spread across the Strait of Malacca.

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Figure 2: Himawari-8 satellite image on 18 Aug 2018 shows moderate to dense smoke haze from fire hotspots detected in several parts of Kalimantan.

Figure 3: Himawari-8 satellite image on 21 Aug 2018 shows the return of shower activities that helped to alleviate the haze situation in Sumatra and Peninsular Malaysia.

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Figure 4: Himawari-8 satellite image on 22 Aug 2018 shows fire hotspots and smoke haze in Kalimantan.

Figure 5: Himawari-8 satellite image on 25 Aug 2018 shows widespread showers over Kalimantan which helped subdue hotspot activities there.

Review of Regional Weather Conditions for Second Fortnight of August 2018

Print Version

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

1.1 Southwest Monsoon conditions prevailed in the second fortnight of August 2018. During the period, rainy weather persisted over most parts of the northern ASEAN region. For the northern parts of Myanmar, Lao PDR and Vietnam and parts of the Philippines, above-average rainfall was recorded.

1.2 In the southern ASEAN region, Sumatra and Kalimantan experienced drier conditions during the first half of the fortnight. This was followed by a gradual increase of shower activities in the latter half of the fortnight. The Java region remained generally dry throughout the period.

1.3 The daily average rainfall and the percentage normal of rainfall for the second fortnight of August 2018 are shown in Figure 1 and Figure 2.

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

Figure 2: Percentage of Normal Rainfall for 16 – 31 August 2018. The rainfall data may be less representative for areas with a less dense rainfall network. (Source: IRI NOAA/NCEP CPC Unified Precipitation Analyses)

1.4 Stronger-than-usual southwesterly winds prevailed over the northern ASEAN region. In the southern ASEAN region, there were no significant wind anomalies observed, and the prevailing winds generally blew from the southeast or southwest. Figure 3 shows the average and anomalous winds at 5000 feet.

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Figure 3: 5000 ft average winds (left) and anomalies (right) for 16 – 31 August 2018. (Source: JMA)

1.5 The El-Southern Oscillation (ENSO) remained in the neutral state(neither El Niño nor La Niña), and other atmospheric indicators continued to show neutral conditions.

1.6 The Madden Julian Oscillation (MJO), which started in Phase 6, weakened and became non-discernible throughout the review period. The weakening of the MJO Phase 6 partly contributed to the cessation of drier conditions over the southern ASEAN region in the second fortnight of August 2018.

Figure 4: The MJO phase diagram for August 2018 (green for August). 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)

September 4, 2018

ASMC Bulletin (Issue #2, Sep 2018)

September 2, 2018

Alert20180902 – Downgrade of Alert Level from 2 to 1 for the southern ASEAN region

Downgrade of Alert Level from 2 to 1 for the southern ASEAN region

In the past week, there has been an improvement in the hotspot and haze situation in Sumatra and Kalimantan due to increased shower activities. No significant smoke haze has been observed in the region in recent days. Visibility and air quality readings across the region have been good in general.

Based on surveillance by the NOAA-19 satellite, 11 and 1 hotspots were detected in Sumatra, and 22 and 3 hotspots were detected in Kalimantan on 31 Aug and 1 Sep respectively. This is a significant reduction from an earlier dry period in mid-August where the number of hotspots exceeded 100 in Kalimantan on several days.

Over the next one to two weeks, rainy weather is forecast over most parts of Sumatra and Kalimantan, with brief, interspersed periods of dry weather in the southern parts of Sumatra and Kalimantan. Hotspot activities in the southern ASEAN region are thus expected to be generally subdued during this period.