Monthly Archives: January 2020

January 31, 2020

Subseasonal Weather Outlook (1- 15 February 2020)

Subseasonal Weather Outlook (1 – 15 February 2020)

Issued 31 January 2020
Valid for weeks 1 and 2: 1 – 15 February 2020

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the first fortnight of February 2020, drier conditions are expected over a broad region covering Sumatra, Peninsular Malaysia, northern parts of Borneo, and the Philippines. The drier conditions are expected to ease in the west in Week 2. There is an increased chance of wetter conditions over the southeastern part of the Maritime Continent. However, there is less confidence in the spatial extent and intensity of the wetter conditions.

For temperature, warmer conditions are expected over much of the Maritime Continent in the first fortnight. Colder conditions may occur in Week 1 over northeastern parts of the northern ASEAN region.

The Madden-Julian Oscillation (MJO) was in Phase 7 towards the end of January 2020 and has dissipated. There is no consistent signal in the dynamical models for an MJO to develop in the forecast period.

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 16, 2020

Outlook for Land Fires and Smoke Haze Situation (16 – 31 January 2020)

Issued 16 January 2020

During the fortnight, the northern ASEAN region can expect the current dry conditions to persist. For parts of the Mekong sub-region, with drier and warmer-than-usual conditions forecast, the sub-region can expect an escalation of hotspot activities and a build-up of smoke haze. An increase in the risk of transboundary haze among countries within the Mekong sub-region is expected. In the southern ASEAN region, the hotspot activities are expected to remain subdued.

Subseasonal Weather Outlook (16- 31 January 2020)

Subseasonal Weather Outlook (16 – 31 January 2020)

Issued 16 January 2020
Valid for weeks 3 and 4: 16 – 31 January 2020

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the second fortnight of January 2020, most areas in the ASEAN region, north of the Equator can expect drier-than-usual conditions, except for the western half of the Mekong sub-region where near average rainfall conditions may be expected. The drier conditions could partly be due to the propagation of the Madden-Julian Oscillation (MJO) during the fortnight from phase 6 to phases 7 – 8. These MJO phases typically bring drier conditions over the Southeast Asia region.

During the fortnight, most parts of the ASEAN region along and north of the Equator can expect warmer-than-usual conditions. For areas south of the Equator, warmer conditions may develop in Week 4 over southern Sumatra, Java and Lesser Sunda Islands.

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 7, 2020

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

1.1 Under the prevailing dry weather, hotspots with localised smoke plumes were detected in the Mekong sub-region. In particular, there was an increase in hotspot activities in Thailand and Cambodia, and the smoke haze from some of these hotspots brought hazy conditions to parts of Thailand and Cambodia. In central Thailand, smoke haze was blown by the prevailing winds to the southwest, and there were reports of Unhealthy to Very Unhealthy air quality on many days in Saraburi province.

1.2 In the southern ASEAN region, hotspot activities were mostly subdued due to the rainy weather.

Figure 1: Distribution of hotspots detected in the Mekong sub-region based on NOAA-20 satellite surveillance, and mean winds at 2500ft in the second fortnight of December 2019 (Source of wind data: JMA).

Figure 2: Himawari-8 satellite image shows smoke haze from hotspots in central Thailand and Cambodia, and localised plumes from isolated hotspots in Myanmar.

Review of Regional Weather Conditions for Second Fortnight of December 2019

Print Version

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

1.1 Northeast Monsoon conditions over the ASEAN region persisted into the second fortnight of December 2019. During the preview period, the prevailing winds blew from the northeast or east over the northern ASEAN region and from the northwest or northeast over most parts of equatorial ASEAN region.

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

1.2 Showers fell over many areas in the southern ASEAN region. East Malaysia, southern Sumatra, Kalimantan and Java recorded above-average rainfall while rainfall was below average in Peninsular Malaysia, and northern and central Sumatra. Parts of the Philippines received above-average rainfall due to the passage of Tropical Storm PHANFONE across central Philippines in late December 2019. Over the Mekong sub-region, dry weather persisted in the second fortnight of December 2019.

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

Figure 3: Percent of average rainfall in the second fortnight of December 2019. The rainfall data is 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: Historical Track of Tropical Storm PHANFONE (Source: JAXA)

1.3 Despite the strong Madden–Julian Oscillation (MJO) signal in Phases 6 and 7 in the last week of December 2019, its contribution to the rainfall in the eastern Maritime Continent was not discernible and could have been masked by the presence of Tropical Storm PHANFONE.

Figure 5: The MJO phase diagram for November (green) – December 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) remains neutral (i.e neither El Niño nor La Niña conditions). The Indian Ocean Dipole (IOD) is currently slightly positive but continues to weaken and a return to neutral state by early 2020 is likely.

January 6, 2020

Alert20200106 – Activation of Alert Level 2 for the Mekong sub-region

Activation of Alert Level 2 for the Mekong sub-region

Persistent dry weather in recent weeks over the Mekong sub-region has led to an escalation in the hotspot activities there. Based on surveillance by the NOAA-20 satellite, there has been a significant increase in the number of hotspots over the past two days, with 615 and 1200 hotspots detected on 4 Jan and 5 Jan respectively. In particular, scattered hotspots with smoke haze have been detected in Cambodia and Thailand. A significant build-up of smoke haze was observed over northern and eastern Cambodia, and some of the smoke haze is being blown to eastern Thailand by the prevailing northeasterly winds.

With the prevailing dry conditions over the Mekong sub-region forecast to persist, and the prevailing winds blowing from the northeast or east, a further deterioration in the hotspot and smoke haze situation in the Mekong sub-region and an increased risk of transboundary haze occurrence can be expected.

January 2, 2020

Outlook for Land Fires and Smoke Haze Situation (1 – 15 January 2020)

Issued 2 January 2020

With dry weather persisting over the Mekong sub-region, a gradual increase in hotspot activities can be expected. On the other hand, hotspot activities in the southern ASEAN region are forecast to remain generally subdued.

Subseasonal Weather Outlook (1- 15 January 2020)

Subseasonal Weather Outlook (1 – 15 January 2020)

Issued 2 January 2020
Valid for weeks 1 and 2: 1 – 15 January 2020

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the first fortnight of January 2020, drier than normal conditions are forecast over parts of the central Philippines and southern Viet Nam. Similar drier than normal conditions are forecast over northern Sumatra, western Peninsular Malaysia and southern Thailand but these conditions are expected to return to normal in the second week of the fortnight.

Meanwhile, it is forecast to be wet over eastern Indonesia, including over Sulawesi and Papua where wet conditions are expected to persist throughout the fortnight. Elsewhere in the ASEAN region, normal conditions are expected.

It is forecast to be warmer than normal over most parts of the northern ASEAN region as well as over Sarawak and Sabah.

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.