Monthly Archives: November 2019

November 27, 2019

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

1.1 In the first fortnight of November 2019, hotspot activities in the northern ASEAN region remained subdued.

1.2 In the southern ASEAN region, there were persistent hotspot clusters and moderate to dense smoke haze mainly in the Sumatran provinces of South Sumatra and Lampung. There were also isolated hotspots with localised smoke plumes detected in southern Kalimantan and some parts of the Lesser Sunda Islands.

Figure 1: Distribution of hotspots detected based on NOAA-20 satellite surveillance and mean winds at 2500 ft in the first fortnight of November 2019 (Source of wind data: JMA)

Figure 2: NOAA-20 satellite image on 7 November 2019 shows smoke haze from hotspot clusters in the southern parts of Sumatra.

Review of Regional Weather Conditions for First Fortnight of November 2019

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

1.1 In the first fortnight of November 2019, northeasterly winds prevailed over many parts of the northern ASEAN region (Figure 1). Under the influence of Tropical Stroms Matmo and Nakri (Figure 2), there were anomalously strong westerly winds to the east of Viet Nam and west of the Philippines. Over the equatorial region, winds were weak and variable in direction. In parts of the southern ASEAN region south of the equator, the prevailing winds blew mainly from the southeast.

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

Figure 2: Historical track of Tropical Storm Matmo (left) and Tropical Storm Nakri (right). (Source: JAXA)

1.2 In the northern ASEAN region, the occurrence of the tropical storms resulted in above-average rainfall over the Philippines and Viet Nam, while drier conditions prevailed over many parts in the Mekong sub-region. In the southern ASEAN region, the monsoon rain band over the equatorial areas brought above-average rainfall over Sumatra, western Java, Malaysia, and most parts of Kalimantan. Figures 3 and 4 shows the daily average rainfall and the percentage of average rainfall respectively for the second fortnight of November 2019.

Figure 3: Daily average rainfall for the ASEAN region in the first fortnight of November 2019. (Source: JAXA Global Satellite Mapping of Precipitation)

Figure 4: Percentage of average rainfall for 1 – 15 November 2019. The rainfall data may be less representative for areas with a less dense rainfall network. (Source: IRI NOAA/NCEP CPC Unified Precipitation Analyses)

1.3 The Madden-Julian Oscillation (MJO) strengthened and propagated from Phase 5 to Phase 8 in the first fortnight of November 2019. However, its effect in moderating the rainfall over the southern ASEAN region was offset by the development of low-pressure systems over the South China Sea during the period.

Figure 5: The MJO phase diagram for November 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)

1.4 The El Niño – Southern Oscillation (ENSO) remained in the neutral state in the first half of November 2019, and the sea-surface temperatures (SST) over the tropical Pacific Ocean continued to cool. Over the Indian Ocean, the positive phase of the Indian Ocean Dipole (IOD) persisted.

November 20, 2019

Alert20191120 – End of Dry Season for the southern ASEAN region

End of Dry Season for the southern ASEAN region

The gradual transition to Northeast Monsoon conditions over the past few weeks has brought an increase in showers over the southern ASEAN region. Based on surveillance by the NOAA-20 satellite, a total of 21 and 8 hotspots were detected in Sumatra, while 5 and 6 hotspots were detected in Kalimantan, on 18 and 19 Nov
2019 respectively.

With Northeast Monsoon conditions expected to prevail, rainy weather can be expected over most parts of the region. However, occasional dry conditions can be expected in the southern parts of Sumatra and Kalimantan. Hotspots with smoke haze can still be expected there. With the prevailing winds forecast to blow from the north or northeast, transboundary haze occurrences are unlikely.

November 15, 2019

Outlook for Land Fires and Smoke Haze Situation (16 – 30 November 2019)

Issued 15 November 2019

Hotspot activities in the northern ASEAN region are expected to remain generally subdued. Hotspots with smoke haze may still emerge in southern Sumatra and Kalimantan during periods of dry weather.

Subseasonal Weather Outlook (16 – 30 November 2019)

Issued 15 November 2019
Valid for weeks 3 and 4: 16 November – 30 November

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

The positive Indian Ocean Dipole (IOD) is expected to persist into the second fortnight of November 2019 and contribute to the drier-than-average weather over areas south of the Equator. Drier-than-average conditions can also be expected in the southern parts of Thailand and Cambodia in the first week of the fortnight.

In contrast, wetter-than-average weather is expected over northern Philippines. The Madden-Julian Oscillation (MJO) is expected to continue to propagate eastwards from Phase 8, contributing to the wetter-than-average conditions over northern Sumatra and Peninsular Malaysia in Week 4.

Warmer-than-average conditions can be expected over many parts of the Mekong sub-region, and over areas around the Java Sea, including southern Sumatra and Kalimantan, and Java.

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.

November 13, 2019

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

1.1 During the second fortnight of October 2019, hotspot activities in the northern ASEAN region remained subdued.

1.2 In the southern ASEAN region, there were persistent hotspot clusters with moderate to dense smoke haze in southern Sumatra, particularly in the provinces of South Sumatra and Lampung. There were also isolated hotspots with smoke plumes detected in southern Kalimantan, Java, Sulawesi and Nusa Tenggara.

Figure 1 Distribution of hotspots detected based on NOAA-20 satellite surveillance and mean winds at 2500ft in the second half of October 2019 (Source of wind data: JMA)

Figure 1 Smoke haze emanating from hotspot clusters in the southern parts of Sumatra (marked by blue dotted lines)

Review of Regional Weather Conditions for Second Fortnight of October 2019

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

1.1 In the second fortnight of October 2019, the prevailing winds over the northern ASEAN region blew from the northeast or east, while the winds over the southern ASEAN region were from the southeast or east. Over the equatorial areas, weaker winds prevailed. There were anomalously strong easterly winds over southern Thailand and Peninsular Malaysia, and stronger-than-usual southeast winds over southern Sumatra.

Figure 1 5000 ft average winds (left) and anomalies (right) for 16 – 31 Oct 2019 (Source: JMA)

1.2 The presence of the monsoon rain band over the equatorial ASEAN region brought near- to above-average rainfall over Peninsula Malaysia, northern Sumatra, and the western part of Borneo Island. Over the areas surrounding the Java Sea (including southern Sumatra, southern Kalimantan and Java), rainfall was below average. The northern ASEAN region received well below-average rainfall in general, except for Viet Nam and parts of Myanmar. Figures 2 and 3 shows the daily average rainfall and the percentage of average rainfall for the second fortnight of October 2019 respectively.

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

Figure 3 Percentage of average rainfall for 16 – 31 October 2019. The rainfall data may be less representative for areas with a less dense rainfall network. (Source: IRI NOAA/NCEP CPC Unified Precipitation Analyses)

1.3 Over the tropical Pacific Ocean, El Niño – Southern Oscillation (ENSO) remained neutral. In the Indian Ocean, the Indian Ocean Dipole (IOD) remained strongly positive during the fortnight.

1.4 The Madden-Julian Oscillation (MJO) propagated through Phase 2 during the third week of October 2019, before weakening towards the last week of the month. During this period, the MJO had some influence on the ASEAN region. It brought easterly anomalies and above-average rainfall over the western Maritime Continent.

Figure 4 The MJO phase diagram (green for October 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)