Monthly Archives: March 2024

March 30, 2024

Subseasonal Weather Outlook (1 – 14 April 2024)

Issued: 27 March 2024
First forecast week: 1 – 7 April 2024
Second forecast week: 8 – 14 April 2024

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Drier conditions are predicted over much of central and southern Mainland Southeast Asia and northern parts of the Maritime Continent in the next fortnight (1 – 14 April).

Wetter conditions are predicted over much of the southern half of the Maritime continent in the next fortnight (1 – 14 April).

Warmer than usual temperature is predicted over most of Southeast Asia in the next fortnight (1 – 14 April).

A Madden-Julian Oscillation (MJO) signal was observed over the Western Hemisphere (Phase 1) towards the end of March based on the RMM index. Most models predict the signal to decay over the Western Hemisphere, becoming indiscernible by the start of Week 1. Some models predict the signal to emerge over the Indian Ocean (Phase 3) during Week 1 and propagate eastwards through the Maritime Continent (Phases 4 and 5) during Week 2.

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.

March 19, 2024

Alert20240207 – Activation of Alert Level 2 for the Mekong sub-region

Activation of Alert Level 2 for the Mekong sub-region

Persistent dry weather conditions over the Mekong sub-region have contributed to an escalation in hotspot and smoke haze activity in recent weeks. Based on satellite surveillance, moderate smoke haze was observed to emit from clusters of hotspots detected in the northern and eastern parts of Cambodia, as well as the western parts of Thailand. Isolated hotspots with smoke plumes were also detected elsewhere in the Mekong sub-region. A total of 248 and 875 hotspots were detected in the Mekong sub-region on 5 and 6 February 2024 respectively from the NOAA-20 satellite.

The prevailing winds are forecast to strengthen and blow from the northeast or east in the coming weeks, while the current dry weather conditions are expected to intensify. Under these conditions, the hotspot and smoke haze situation could worsen with an increased risk of transboundary smoke haze occurrence.

Review of Regional Weather for January 2024

1. Overview

1.1 During January 2024, a mix of below- to above-average was recorded over the Maritime Continent, with much of the central and western parts receiving above-average rainfall, and the northeastern parts receiving below-average rainfall (Figure 1). Over Mainland Southeast Asia, near-average rainfall was recorded in January. The largest positive (wetter) anomalies were recorded over southern Philippines and southern parts of the Malay Peninsula based on GSMaP-NRT (Figure 1, left) and CMORPH-Blended (Figure 1, right) satellite-derived rainfall estimates. In contrast, the largest negative (drier) anomalies were recorded over central Philippines (in both GSMaP-NRT and CMORPH-Blended).

1.2 The observed rainfall anomaly pattern of above-average rainfall over most of the western half of Maritime Continent, the drier than average conditions over the northeastern parts of the Maritime Continent, and the near-average rainfall over Mainland Southeast Asia are broadly consistent with the predictions from the subseasonal weather outlooks for January 2024(25 December 2023 – 7 January 2024, 8 – 21 January 2024,8 – 21 January 2024) and 22 January – 4 February 2024).

Figure 1: Rainfall anomalies for January 2024 based on GSMaP-NRT data (left) and CMORPH-Blended data (right). The climatological reference period is 2001-2023. Green colour denotes above-average rainfall (wetter), while orange denotes below-average rainfall (drier).

1.3 Above-average temperatures were recorded over the Maritime Continent and much of Mainland Southeast Asia (Figure 2) in January 2024. The exceptions were over parts of Myanmar and Cambodia, where below-to near-average temperature was recorded. The warmest anomalies (more than 1°C above average) were recorded over Thailand, Lao PDR, northern Viet Nam, Sulawesi, and eastern parts of Borneo.

Figure 2: Temperature anomalies for January 2024 based on ERA-5 reanalysis. The climatological reference period is 2001-2023. Red colour denotes above-average temperature (warmer), while blue denotes below-average temperature (colder).

2. Climate Drivers

2.1 The Madden-Julian Oscillation (MJO) was active throughout the entire month of January, based on the RMM index (Figure 3). In the first and second weeks of January, an active MJO signal was present over the Indian Ocean (Phases 2 and 3). In the third week of the month, the active MJO signal was propagating eastwards through the Maritime Continent (Phases 4 and 5) and remained active during the last week over the Western Pacific (Phases 6 and 7). Typically for January, Phase 3 tends to bring wetter conditions for western Maritime Continent, Phase 4 tends to bring wetter conditions for the much of the Maritime Continent, and Phases 6 and 7 tend to bring drier conditions for the western Maritime Continent. Phases 5 tends to bring a mix of wetter and drier conditions.

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 El Niño conditions persisted over the equatorial Pacific during January 2024. Sea surface temperatures in the Nino3.4 region (used to monitor ENSO) continue to show El Niño conditions, with key atmospheric indicators (cloudiness and trade winds) still supporting these conditions but started to weaken. The positive Indian Ocean Dipole event has likely ended. El Niño events tend to bring drier and warmer-than-average conditions to much of the Maritime Continent during December – February.

Subseasonal Weather Outlook (4 – 17 March 2024)

Issued: 1 March 2024
First forecast week: 4 – 10 March 2024
Second forecast week: 11 – 17 March 2024

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For much of the equatorial region, wetter conditions are predicted in Week 1 (4 – 10 March), followed by drier conditions in Week 2 (11 – 17 March).

Elsewhere, drier conditions are predicted over the northeastern Maritime Continent and southern Mainland Southeast Asia in the next fortnight (4 – 17 March). Wetter conditions are predicted over most of the southern and southeastern Maritime Continent in the next fortnight (4 – 17 March).

Warmer than usual temperature is predicted over the Maritime Continent and most of Mainland Southeast Asia in the next fortnight (4 – 17 March).

No discernable Madden-Julian Oscillation (MJO) signal was present towards the end of February based on the RMM index. Models predict an MJO signal to develop in the Indian Ocean (Phase 3) by the start of the forecast period, propagating through the Maritime Continent (Phases 4 and 5) during Week 1. Most models predict the MJO signal to reach the Western Pacific (Phase 6) during Week 2.

Subseasonal Weather Outlook (19 February – 3 March 2024)

Issued: 16 February 2024
First forecast week: 19 – 25 February 2024
Second forecast week: 26 February – 3 March 2024

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Drier conditions are predicted over the northern half of the Maritime Continent and southeastern Mainland Southeast Asia in the next fortnight (19 February – 3 March).

Wetter conditions are predicted over parts of the central and southeastern Maritime Continent in the next fortnight (19 February – 3 March), with higher likelihood over the southeastern Maritime Continent in Week 1 (19 – 25 February).

Warmer than usual temperature is predicted over most of the Maritime Continent as well as southern Mainland Southeast Asia in Week 1 (19 – 25 February). The warmer than usual temperature is predicted to persist over much of the Maritime Continent in Week 2 (26 February – 3 March).

A Madden-Julian Oscillation (MJO) signal was present over the Western Pacific (Phase 7) in the middle of February based on the RMM index. Most models predict the MJO signal to become indiscernible in Week 1 and then remain inactive for the rest of the forecast period.

Subseasonal Weather Outlook (22 January – 4 February 2024)

Issued: 19 January 2024
First forecast week: 22 January – 4 February 2024
Second forecast week: 29 January – 4 February 2024

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are predicted over parts of the southeastern Maritime Continent during the next fortnight (22 January – 4 February).

Drier conditions are predicted over parts of the northeastern Maritime Continent in Week 1 (22 – 28 January). In Week 2 (29 January – 4 February), drier conditions are predicted over the western Maritime Continent.

Cooler than usual temperature is predicted over much of central and eastern Mainland Southeast Asia in Week 1 (22 – 28 January). Warmer that usual temperature is predicted over most of the Maritime Continent and the southern most parts of Mainland Southeast Asia in the next fortnight (22 January – 4 February).

A Madden-Julian Oscillation (MJO) signal was present over the Maritime Continent (Phase 4) in mid-January based on the RMM index. Most models predict this MJO signal to continue propagating eastwards through the Maritime Continent (Phase 5) and the Western Pacific (Phase 6) in Week 1. In Week 2, some models predict this signal to further propagate over the Western Pacific (Phase 7), whereas other models predict this signal to weaken and become inactive.

March 13, 2024

Subseasonal Weather Outlook (18 – 31 March 2024)

Issued: 13 March 2024
First forecast week: 18 – 24 March 2024
Second forecast week: 25 – 31 March 2024

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Drier conditions are predicted over parts of the northeastern Maritime Continent and southern Mainland Southeast Asia in Week 1 (18 – 24 March). Drier conditions are also predicted over much of the southern Maritime Continent in the next fortnight (18 – 31 March).

Wetter conditions are predicted over parts of the equatorial region in Week 2 (25 – 31 March).

Warmer than usual temperature is predicted over the Maritime Continent in the next fortnight (18 – 31 March). Elsewhere, warmer than usual temperature is predicted over southern Mainland Southeast Asia in Week 1 (18 – 24 March) and extending to parts of eastern Mainland Southeast Asia in Week 2 (25 – 31 March).

A Madden-Julian Oscillation (MJO) signal was observed over the Maritime Continent (Phase 4) towards the middle of March based on the RMM index. Models predict the signal to reach the Western Pacific (Phase 6) by the start of the forecast period. Thereafter, most models predict the MJO signal to gradually decay as it propagates eastwards, becoming indiscernible over the Western Hemisphere (Phase 8) by Week 2.

Review of Regional Weather for February 2024

1. Overview

1.1 During February 2024, a mix of below- to above-average was recorded over the Maritime Continent, with parts of the western half of the equatorial region receiving above-average rainfall, and below-average rainfall elsewhere (Figure 1). Over Mainland Southeast Asia, near-average rainfall was recorded in February. The largest positive (wetter) anomalies were recorded over central Sumatra based on GSMaP-NRT (Figure 1, left) and CMORPH-Blended (Figure 1, right) satellite-derived rainfall estimates. In contrast, the largest negative (drier) anomalies were recorded over central parts of the Philippines (in both GSMaP-NRT and CMORPH-Blended).

1.2 The observed rainfall anomaly pattern of above-average rainfall over the western and central parts of the equatorial Maritime Continent coupled with below-average rainfall in particular over northwestern Maritime Continent, and the near-average rainfall over Mainland Southeast Asia, are broadly consistent with the predictions from the subseasonal weather outlooks for February 2024 (5 – 18 February 2024 and 19 February – 3 March 2024).

Figure 1: Rainfall anomalies for February 2024 based on GSMaP-NRT data (left) and CMORPH-Blended data (right). The climatological reference period is 2001-2023. Green colour denotes above-average rainfall (wetter), while orange denotes below-average rainfall (drier).

1.3 Above-average temperatures were recorded over the Maritime Continent and much of Mainland Southeast Asia (Figure 2) in February 2024. The exceptions were over parts of Myanmar and Cambodia, where below-to near-average temperature was recorded. The warmest anomalies (more than 2°C above average) were recorded over some parts of eastern Thailand and southern Lao PDR.

Figure 2: Temperature anomalies for February 2024 based on ERA-5 reanalysis. The climatological reference period is 2001-2023. Red colour denotes above-average temperature (warmer), while blue denotes below-average temperature (colder).

2. Climate Drivers

2.1 The Madden-Julian Oscillation (MJO) was active for much of February 2024, based on the RMM index (Figure 3). In the first and second weeks of February, an active MJO signal was present over the Western Pacific (Phases 6 and 7). In the third week of the month, the active MJO signal weakened in strength in Phase 7 and became e indiscernible in the last week of February. Typically for February, Phases 6 and 7 tend to bring drier conditions for the western Maritime Continent.

2.2 El Niño conditions over the equatorial Pacific continued weakening during February 2024. Sea surface temperatures in the Nino3.4 region (used to monitor ENSO) continue to show El Niño conditions but has likely past its peak, and key atmospheric indicators (cloudiness and trade winds) are consistent with the weakening El Niño conditions. El Niño events tend to bring drier and warmer-than-average conditions to much of the Maritime Continent during December – February.

March 8, 2024

Review of Regional Haze Situation for February 2024

1.1 1.1 The ASEAN region continued to experience Northeast Monsoon conditions in February 2024. Over areas north of the Equator, the prevailing winds blew mainly from the northeast except over the Mekong sub-region where the winds were mostly light and variable in direction. Over areas south of the Equator, the prevailing winds blew mostly from the northwest or north (Figure 1).

1.2 1.2 The Mekong sub-region remained dry throughout the review period of February 2024, with moderate to dense haze observed over many parts of the sub-region (Figure 6) on several days. On 7 February 2024, the Alert Level 2 for the Mekong sub-region was activated in view of the increasing hotspots and risk of transboundary haze in the Mekong sub-region. Showers were observed elsewhere in the ASEAN region, except for parts of Peninsular Malaysia and the Philippines where there were brief periods of drier weather. The overall hotspot and haze situation in the southern ASEAN region and the Philippines stayed subdued (Figure 1).

Figure 1: Average Daily Rainfall and Mean Winds for February 2024. (Source: JAXA GsMaP and GFS, respectively)

1.3 1.3 Over the Mekong sub-region, the hotspot counts in February 2024 were comparable to previous years (Figure 2). Over the southern ASEAN region, the hotspot counts were higher or comparable, with a rise in Kalimantan, Peninsular Malaysia as well as Sabah and Sarawak compared to the past few years. Sabah and Sarawak recorded the highest hotspot count over 5 years (Figure 3), although the hotspot count for the southern ASEAN region during the review period remained relatively low.

Figure 2: Hotspot counts for the northern ASEAN region for February (2020-2024) based on NOAA-20 satellite surveillance.

Figure 3: Hotspot counts for the southern ASEAN region for February (2020-2024) based on NOAA-20 satellite surveillance.

1.4 1.4 Hotspot activities were persistent over many areas of the Mekong sub-region in February, with fires of higher intensity observed mainly over parts of Lao PDR and northeastern Cambodia (Figure 4 and 5). Moderate to dense smoke haze was observed mostly in the northern, western, and central parts of the sub-region (Figures 6, 7 and 8).

Figure 4: Distribution of hotspots detected in February 2024 based on NOAA-20 satellite surveillance.

Figure 5: Maximum fire intensity in February 2024 based on NOAA-20 satellite surveillance.

Figure 6: Number of days with moderate to dense smoke haze observed in February 2024 based on satellite imagery, ground observations, and air quality reports.

Figure 7: Moderate to dense transboundary smoke plumes were observed drifting from northeastern Cambodia into the southern parts of Lao PDF and eastern Thailand on 17 February 2024. (Source: Himawari-9 satellite surveillance)

Figure 8: Moderate to dense smoke haze was observed over the eastern, central and southern parts of Myanmar on 24 February 2024. (Source: Himawari-9 satellite surveillance)

Hotspot and Haze Assessment (H2A) Workshop 2024 for the ASEAN Region, Singapore 27 – 29 February 2024

On 27-29 February 2024, the ASEAN Specialised Meteorological Centre (ASMC) conducted the ninth run of the Hotspot and Haze Assessment (H2A) workshop for the ASEAN region in Singapore. This workshop is part of the ongoing ASMC Regional Capability-building Programme (ACaP), which seeks to build regional capabilities in weather forecasting, haze monitoring, subseasonal-to-seasonal predictions, as well as climate change projections.

During this workshop, experts from the environment and meteorological sectors of the ASEAN region shared their local experiences, knowledge and preparations for the upcoming dry seasons. Topics covered during the workshop included fire and haze detection methodologies, subseasonal-to-seasonal prediction, dispersion modelling and a walkthrough of key ASMC information platforms for the region. There were also hands-on activities where participants were guided on extraction of satellite data and regional haze analysis. The lecturers were from ASMC as well as the US National Oceanic and Atmospheric Administration (NOAA) National Environmental Satellite Data and Information Service (NESDIS), the key developer of the hotspot detection algorithms used in the region.

Figure 1: Group photograph of ASMC staff and trainers, NOAA lecturers and participants of the 2024 H2A workshop.

Figure 2: Participants’ sharing of local experience on fire and haze in their countries.

Beyond the lectures and activities, participants also visited the Singapore Marina Barrage, one of the largest water catchment areas located in the heart of the city, as well as the sustainable gallery. Many participants appreciated the relevance and usefulness of the topics covered and shared positive feedback on their experiences at the event.

Figure 3: Lecturer from NOAA sharing on fire detection algorithms and haze detection tools.

Figure 4: Participants had the opportunity to learn about climate change mitigation efforts at the sustainable gallery.