Monthly Archives: October 2018

October 23, 2018

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

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

1.1 During the first half of October 2018, hotspot activities in the northern ASEAN region were subdued. While there were hotspots with smoke haze observed in the southern parts of Sumatra and Kalimantan in early October, the hotspot activities were generally subdued due to an increase in rain showers with the transition to inter-monsoon conditions and the southward migration of monsoon rainband.

1.2 Figures 1 and 2 show the satellite images over the ASEAN region in the first fortnight of October 2018.

Figure 1: Himawari-8 satellite image on 3 Oct 2018 shows smoke haze from hotspots in southern Sumatra.

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Figure 2: Moderate smoke haze over Kalimantan as shown in the Himawari-8 satellite image on 2 Oct 2018.

Review of Regional Weather Conditions for First Fortnight of October 2018

Print Version

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

1.1 The Southwest Monsoon season transitioned into the inter-monsoon period around mid-October 2018. During the first half of October 2018, the monsoon rainband shifted southward to the equatorial ASEAN region. This southward shift was driven by stronger-than-usual northeasterly and easterly winds over the South China Sea, due to an outflow of dry air from a high pressure system over north Asia. As a result, most parts of the northern ASEAN region received below normal rainfall, except for Myanmar where above normal rainfall was contributed by rain associated with a low pressure weather system that developed over the Andaman Sea and Bay of Bengal.

1.2 The monsoon rainband brought above-normal rainfall to the equatorial ASEAN region, viz northern half of Sumatra, Indonesia, Peninsular Malaysia, and parts of Kalimantan. Below normal rainfall was received in southern Sumatra and Java due to the incursion of dry air from the southern hemisphere.

1.3 The rainfall distribution and the percentage of average rainfall for the first fortnight of October 2018 are shown in Figure 1 and 2, respectively.

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

Figure 2: Percentage of Average Rainfall for 1 – 15 October 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 Under the influence of an intense high pressure system over north Asia, there were anomalous easterly winds over the northern ASEAN region and the South China Sea. Elsewhere in the region, winds were close to near normal conditions.

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Figure 3: 5000 ft average winds (left) and anomalies (right) for 1 – 15 October 2018. (Source: JMA)

1.5 In the first fortnight of October 2018, there are indications of El Niño conditions developing in the tropical Pacific Ocean. For instance, the sea surface temperatures were observed to be warmer than average along the equator in the Pacific Ocean, and trade winds were also observed to have weakened. Over the Indian Ocean, sea surface temperatures were observed to be cooler than usual in the eastern Indian Ocean – signs of a nascent positive Indian Ocean Dipole (IOD) event.

1.6 The Madden Julian Oscillation (MJO) which was active and propagated through Phases 1 and 2 during the first fortnight of October 2018, significantly influenced the weather in the region. The drier than usual conditions over parts of the northern ASEAN region and around the Java Sea area, as well as the anomalous easterly winds over the South China Sea were characteristic of the MJO signal in Phases 1 and 2 over the ASEAN region.

Figure 4: The MJO phase diagram for October 2018 (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)

October 18, 2018

Review of Regional Weather Conditions for Second Fortnight of September 2018

Print Version

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

1.1 Southwest Monsoon conditions continued to prevail in the second fortnight of September 2018. During the period, the northern ASEAN region experienced rainy weather on most days. The southward shift of the monsoon rainband brought an increase in rainfall in the equatorial region including southern Thailand, Peninsular Malaysia, northern Sumatra, Sabah and Sarawak, which is typical for this period of the year.

1.2 In southern Sumatra and Kalimantan, there were showers interspersed with brief periods of dry weather. The Java region continued to remain generally dry. Generally, the observed conditions were consistent with the outlook provided for the period.

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

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

Figure 2: Percentage of Normal Rainfall for 16 – 30 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 Light and variable winds prevailed over the northern ASEAN region. In the southern ASEAN region, prevailing winds blew generally from the southeast or south. There were no significant wind anomalies observed in the region during the review period. Figure 3 shows the average and anomalous winds at 5000 feet.

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Figure 4: 5000 ft average winds (left) and anomalies (right) for 16 – 30 September 2018. (Source: JMA)

1.5 The sea surface temperatures of the eastern Pacific Ocean reflected neutral El Niño-Southern Oscillation (ENSO) conditions (neither El Niño nor La Niña). The key atmospheric indicators also suggested neutral conditions, although weak westerly low-level wind anomalies have developed recently.

1.6 The Madden Julian Oscillation (MJO) was largely weak and non-discernible during the review period. Nonetheless, the MJO (Phase 8) began to strengthen and develop toward the end of the fortnight. The MJO had no significant influence on the weather in the region during this period.

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)

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

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

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

1.2 In the southern ASEAN region, rainy weather helped to subdue hotspot activities in the first half of the fortnight. In the second half of the fortnight, drier weather led to increased hotspot activities in the central and southern parts of Sumatra and Kalimantan. The haze situation in Kalimantan was more severe as compared to that in Sumatra. There were scattered hotspots with large extent of moderate smoke haze observed in Central and South Kalimantan which persisted until the end of September.

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

Figure 1: Himawari-8 satellite image on 18 Sep 2018 shows hotspot activities subdued by shower activities.

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Figure 2: Himawari-8 satellite image on 27 Sep 2018 shows moderate smoke haze observed in central Sumatra during brief period of dry weather.

Figure 3: NOAA-19 satellite image on 28 Sep 2018 shows hotspots and smoke haze detected in several parts of Kalimantan as dry weather persisted.

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Figure 4: Himawari-8 satellite image on 28 Sep 2018 shows hotspot activities subdued by scattered showers in the northern ASEAN region.

Alert20181018 – Downgrade of Alert Level from 2 to 1 for the southern ASEAN region

Downgrade of Alert Level from 1 to 0 for the southern ASEAN region

With the onset of inter-monsoon conditions in mid-October 2018, the southern ASEAN region, including Sumatra and Kalimantan has been experiencing an increase in shower activities.

The number of hotspots detected in Sumatra and Kalimantan has remained low in recent days. Based on surveillance by the NOAA-19 satellite, no hotspots were detected in Sumatra, and 6 and 0 hotspots were detected in Kalimantan on 17 and 18 Oct 2018 respectively. No significant smoke haze was observed in the region.

More rainy weather can be expected over the region with a gradual transition to the Northeast Monsoon season in the coming weeks. Hotspot activities in the southern ASEAN region are expected to remain generally subdued. While isolated hotspots may still emerge during brief periods of dry weather, these hotspots are likely to be localised and short-lived.

October 16, 2018

Outlook for Land Fires and Smoke Haze Situation (16 – 31 Oct 2018)

Outlook for Land Fires and Smoke Haze Situation (16- 31 Oct 2018)

Issued 15 October 2018

Hotspot activities in the northern ASEAN region are expected to remain subdued. In the southern ASEAN region, sporadic hotpot activities are expected during brief periods of dry weather.

October 15, 2018

Subseasonal Weather Outlook (16 Oct – 31 Oct 2018)

Issued 15 Oct 2018
valid for weeks 3 and 4: 16 Oct – 31 Oct

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

From mid-October, wetter conditions may develop over Myanmar, especially over the coastal areas, due to an increase in rain showers that may be brought by tropical cyclones developing over the Bay of Bengal. The drier than normal conditions experienced by much of the Mekong sub-region in the first half of the month are likely to rescind, and a return to normal conditions can be expected for parts of the sub-region. Conditions are likely to be drier than normal in Viet Nam and the Philippines.

For the southern ASEAN region, drier conditions around the Java Sea area, including southern parts of Sumatra and Kalimantan, can be expected.

Warmer temperatures are forecast for the Mekong sub-region, and in Java and southern Sumatra.

The MJO signal is active in Phase 2 and may contribute to the development of tropical lows over the Bay of Bengal and the wet anomaly over coastal Myanmar. Most models predict the weakening of the MJO as it moves into the Maritime Continent.

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.

October 3, 2018

Outlook for Land Fires and Smoke Haze Situation (1 – 15 Oct 2018)

Outlook for Land Fires and Smoke Haze Situation (1- 15 Oct 2018)

Issued 3 October 2018

Hotspot activities in the northern ASEAN region are expected to remain subdued. In the southern ASEAN region, hotspot activities in the southern parts of Sumatra and Kalimantan may persist due to dry conditions. An increase in shower activities in the later half of the fortnight can help to subdue the hotpots.

Subseasonal Weather Outlook (1 Oct – 15 Oct 2018)

Issued 3 Oct 2018
valid for weeks 1 and 2: 1 Oct – 15 Oct

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Prevailing drier conditions are expected to persist over the northern ASEAN region, although the extent and magnitude of the conditions around the South China Sea could be influenced by the presence of typhoons in the surrounding region.

A band of above-average rainfall is predicted to develop around the equator and is expected to persist until the end of the first fortnight in October.

During the outlook period, the drier-than-average conditions surrounding Java are expected to continue. These conditions are in part related to cooler sea surface temperatures in the southeast tropical Indian Ocean.

Slightly warmer temperatures are expected over the northern and central ASEAN region, including Thailand, parts of Laos and Vietnam, Cambodia, Malaysia, and the southern Philippines.

An MJO signal has developed in Phase 8. The MJO is expected to strengthen and propagate eastward during the first fortnight of October and contribute to the above-average rainfall around the equator.

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.