Monthly Archives: April 2022

April 29, 2022

Subseasonal Weather Outlook (2 – 15 May 2022)

Issued: 29 April 2022
First forecast week: 2 May – 8 May
Second forecast week: 9 May – 15 May

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over the northwestern part of the ASEAN region in Week 1 (2 May – 8 May), including Myanmar, southern Mainland Southeast Asia, and parts of the western Maritime Continent. These wetter conditions are predicted to ease in Week 2 (9 May – 15 May), apart from over most of Myanmar.

Cooler temperatures than usual are expected over most of Mainland Southeast Asia in Week 1 (2 May – 8 May). The highest likelihood for cooler temperatures is over eastern Mainland Southeast Asia. These cooler temperatures are predicted to ease in Week 2 (9 May – 15 May), except for parts of Myanmar, in line with the wetter conditions predicted.

Warmer than usual temperatures are predicted over the equatorial region in Week 2 (9 May – 15 May).

No discernible Madden-Julian Oscillation (MJO) signal was present at the end of April. Models predict the MJO signal to remain weak or indiscernible for the next fortnight.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Alert20220429 – Downgrade to Alert Level 2 for the Mekong Sub-Region

Downgrade to Alert Level 2 for the Mekong Sub-Region

In recent days, increased shower activities were observed over the Mekong sub-region which have helped to alleviate the overall hotspot and smoke haze situation there. Parts of Myanmar, northern Lao PDR and northern Thailand may still experience continued hotspot and smoke haze activity during dry periods. However the haze situation is expected to continue to improve with more rainy weather over the Mekong sub-region in the coming weeks.

A total of 2640 and 318 hotspots were detected in the Mekong sub-region on 27 and 28 April 2022 respectively from the NOAA-20 satellite.

April 19, 2022

Review of Regional Haze Situation for March 2022

1.1 In March 2022, Northeast Monsoon conditions prevailed over the ASEAN region. While the prevailing winds over the areas north of the Equator blew mostly from the northeast or east, the winds over the Mekong sub-region were light and variable in direction. The prevailing winds over the areas south of the Equator blew mostly from the west or northwest. As the Northeast Monsoon conditions gradually weakened in the second half of the month, the prevailing winds over most of the ASEAN region were light and variable in direction on several days during the review period (Figure 1).

1.2 The dry conditions over the Mekong sub-region continued in March 2022, even though isolated showers were observed over the sub-region on some days. In the rest of the ASEAN region, generally wet conditions were observed but brief periods of drier weather were experienced in Sumatra and West Kalimantan (Figure 1).

Figure 1: Average Daily Rainfall and Mean Winds for March 2022. (Source: JAXA GsMaP and GFS, respectively)

1.3 For March 2022, the total number of hotspots were lower or comparable compared to previous years for the same period (Figure 2 & 3).

Figure 2: Hotspot counts for the northern ASEAN region for the month of March (2018 – 2022). [Note: The hotspot counts from 2019 onwards are based on the NOAA-20 satellite, while those from 2018 are based on the Suomi-NPP satellite.]

Figure 3: Hotspot counts for the southern ASEAN region for the month of March (2018 – 2022). [Note: The hotspot counts from 2019 onwards are based on the NOAA-20 satellite, while those from 2018 are based on the Suomi-NPP satellite.]

1.4 Scattered to widespread hotspots were detected during the continued dry weather conditions over the Mekong sub-region. Clusters of hotspots were more intense and persistent in Myanmar, Lao PDR and northeastern Cambodia, with smoke haze observed to emanate from these hotspots on several days. In particular, smoke haze was observed to be denser over parts of Myanmar and northern Lao PDR.

1.5 Elsewhere in the ASEAN region, isolated to scattered hotspots were observed mostly in the Philippines, central Sumatra, West Kalimantan and Sulawesi. Localised smoke plumes were observed to emanate from the hotspots detected in West Kalimantan and the western coastal areas of central Sumatra on some days in the second half of the month.

Figure 4: Distribution of hotspots detected in March 2022 based on NOAA-20 satellite surveillance.

Figure 5: Maximum fire intensity in March 2022 based on NOAA-20 satellite surveillance.

Figure 6: Number of days with moderate to dense smoke haze observed in March 2022 based on satellite imagery, ground observations, and air quality reports.

Figure 7: Moderate to dense smoke haze observed over western Myanmar, as well as the northern parts of Thailand and Lao PDR on 14 March 2022, based on NOAA-20 satellite imagery.

Figure 8: Localised smoke plumes observed to emanate from hotspots detected in the western coastal areas of central Sumatra (Left) and in West Kalimantan (Right) on 27 March 2022, based on NOAA-20 satellite imagery.

Review of Regional Weather for March 2022

1. Overview

1.1 During March 2022, above-average rainfall was recorded over much of the northern ASEAN region, while a mix of below- to above-average rainfall was recorded over the southern ASEAN region (Figure 1). For the northern ASEAN region, above-average rainfall was recorded apart from over central and northern Myanmar. The largest positive anomalies (wetter conditions) were recorded over northeastern Mainland Southeast Asia and southern half of the Philippines for both satellite-derived rainfall estimates datasets (GSMaP-NRT and CMORPH-Blended), which was associated with tropical depression 01W that formed on the last three days of March 2022. For the southern ASEAN region, negative anomalies (drier conditions) were recorded over western parts of Sumatra as well as western and central Borneo, although the negative anomalies were larger based on CMORPH-Blended data (Figure 1b) compared to GSMaP-NRT (Figure 1a). Elsewhere in the southern ASEAN region, rainfall tended to be near- to above-average during March 2022. There are some discrepancies between the two datasets, as GSMaP-NRT recorded above-average rainfall for much of central Java and northern Sumatra, while CMORPH-Blended recorded near- to below-average rainfall with isolated areas of above-average rainfall over the mentioned regions.

1.2 The observed rainfall anomaly pattern of above-average rainfall for much of the northern ASEAN region and a mix of below- to above-average rainfall for the southern ASEAN region is broadly consistent with the predictions from the subseasonal weather outlooks for March 2022 (21 February – 6 March, 7 – 20 March, and 21 March – 3 April).

Figure 1: Rainfall anomalies for the month of March 2022 based on GSMaP-NRT data (left) and CMORPH-Blended data (right). The climatological reference period is 2001-2021. Green colour denotes above-average rainfall (wetter), while orange denotes below-average rainfall (drier).

1.3 Most parts of Southeast Asia north of 15°N experienced above-average temperatures during March 2022 (Figure 2). The largest positive anomalies (more than 1°C warmer) were over northern and eastern parts of Myanmar, northwest Thailand, northern Lao PDR and northern Viet Nam. Elsewhere, near-average temperatures were experienced in most of the region, with above-average temperatures for Papua and southern and central parts of Sumatra, and below-average temperatures for parts of the southern Mainland Southeast Asia.

Figure 2: Temperature anomalies for the month of March 2022 based on ERA-5 reanalysis. The climatological reference period is 2001-2021. Red colour denotes above-average temperature (warmer), while blue denotes below-average temperature (colder).

2. Climate Drivers

2.1 The Madden-Julian Oscillation (MJO) signal was indiscernible at the start of March 2022, based on the MJO phase diagram below (Figure 3). In the second week of March, an MJO signal developed over the Western Hemisphere (Phase 1). The MJO signal then propagate eastward over the Indian Ocean (Phase 2 to Phase 3), before weakening and becoming indiscernible in the last week of March. Phase 2 tends to bring drier conditions to the southeastern Maritime Continent while Phase 3 tends to bring wetter conditions to the western Maritime Continent.

Figure 3: The MJO phase diagram. The diagram illustrates the movement of the MJO through different phases, which correspond to different locations along the equator (denoted in the text with the first day of the month in blue and the last day of the month in red). The distance of the index from the centre of the diagram is related to the strength of the MJO. Values within the grey circle are considered weak or indiscernible (data from the Bureau of Meteorology, Australia).

2.2 Over the tropical Pacific Ocean, La Niña conditions were present but there are signs of weakening. Sea surface temperatures in the Nino3.4 region (used to monitor ENSO) and the atmospheric indicators over the tropical Pacific Ocean were consistent with La Niña conditions. La Niña events tend to bring wetter-than-average conditions to much of the Maritime Continent during the December to March period.

April 14, 2022

Subseasonal Weather Outlook (18 April – 1 May 2022)

Issued: 14 April 2022
First forecast week: 18 April – 24 April
Second forecast week: 25 April – 1 May

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over the southern Maritime Continent in the next fortnight (18 April – 1 May). Wetter conditions are also predicted over parts of central Mainland Southeast Asia in Week 1 (18 – 24 April), covering the eastern half of Myanmar and western half of Thailand.

Cooler temperatures than usual are expected over much of Mainland Southeast Asia and the northern half of the Malay Peninsula in Week 1 (18 – 24 April).

No discernible Madden-Julian Oscillation (MJO) signal was present in the first two weeks of April. While some models predict no significant MJO activity during the forecast period, others predict MJO activity in the Western Pacific (Phase 7) and the Western Hemisphere and Africa (Phases 8 and 1) during Week 1.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

April 11, 2022

Alert20220411 – Activation of Alert Level 3 for the Mekong Sub-Region

Activation of Alert Level 3 for the Mekong Sub-Region

In the past few days, persistent dry conditions over the Mekong sub-region have led to an escalation of the hotspot and smoke haze situation, with widespread moderate to dense smoke haze observed over many parts of the sub-region. Based on the surveillance by NOAA-20 satellite, a total of 3,457 and 2,031 hotspots were detected in the Mekong sub-region on 9 and 10 Apr 2022 respectively.

The current dry conditions are expected to persist, with the prevailing winds forecast to be generally light and variable in direction in the coming days. Under these conditions, the overall hotspot activity and hazy conditions in the Mekong sub-region are likely to remain elevated, and there remains a high risk of transboundary haze in the sub-region.

ASMC Media Release – Deteriorating haze situation in the Mekong sub-region

April 1, 2022

Subseasonal Weather Outlook (4 – 17 April 2022)

Issued: 1 April 2022
First forecast week: 4 April – 10 April
Second forecast week: 11 April – 17 April

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over the band covering the Malay Peninsula, southeastern Mainland Southeast Asia, and the Philippines in Week 1 (4 – 10 April). These wetter conditions are expected to persist for much of the region in Week 2 (11 – 17 April), apart from over parts of the Malay Peninsula and southern Philippines.

Drier conditions are predicted for much of the southern half of the Maritime Continent over the next fortnight (4 – 17 April). Drier conditions are also predicted over central and northeastern Mainland Southeast Asia in Week 1 (4 – 10 April) only.

Warmer conditions than usual are predicted over much of the southern half of the Maritime Continent in the next fortnight (4 – 17 April), in line with the drier conditions predicted. Cooler temperatures than usual are expected over much of Mainland Southeast Asia and the northern half of the Malay Peninsula in Week 1 (4 – 10 April).

No discernible Madden-Julian Oscillation (MJO) signal was present at the end of March. Most models predict no significant MJO activity during the forecast period.

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.