Monthly Archives: February 2024

February 16, 2024

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.

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.

February 13, 2024

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 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.

Review of Regional Haze Situation for January 2024

1.1 Northeast monsoon conditions continued in January 2024, as suggested by the prevailing low-level winds. Winds over areas north of the Equator in the ASEAN region blew predominantly from the northeast or east while the winds over areas south of the Equator blew mostly from the northwest to west (Figure 1). On occasion, the northeasterly winds strengthened over the South China Sea, and brought periods of cloudiness and widespread rainfall associated with the monsoon surge to parts of eastern Peninsular Malaysia and Singapore.

1.2 Dry conditions persisted over the Mekong sub-region (Figure 1) under Alert Level 1. For the rest of the ASEAN region, increased rainfall was recorded except for the northern parts of the Philippines where conditions were relatively drier. Rainfall was much higher over the Mindanao region of the Philippines due to the presence of the Northeast Monsoon (Figure 1). The presence of monsoon surges continued in January which affected eastern areas in Peninsular Malaysia, causing fatalities and displacement of people, including damages to infrastructure and agriculture. (Figure 1)

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

1.3 The overall hotspot counts for the northern ASEAN region was generally lower in January 2024 compared to hotspots recorded for the same period in previous years, although hotspot counts in Cambodia were higher compared to the last three years. In the southern ASEAN region, the hotspot counts were generally lower or comparable to previous years (Figure 2 and 3).

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

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

1.4 Isolated to scattered hotspots were detected in the Mekong sub-region (Figure 4) and also the Philippines. Persistent clusters of moderate intensity hotspots, some with smoke plumes were observed consistently in the northeastern and eastern parts of Cambodia (Figure 4, 5 and 7).

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

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

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

Figure 7: Moderate haze was observed in the northeastern and eastern parts of Cambodia from January 2024 (Source: NOAA-20 satellite surveillance.)

February 7, 2024

Alert20240207 – Activation of Alert Level 2 for 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.

February 2, 2024

Subseasonal Weather Outlook (5 – 18 February 2024)

Issued: 2 February 2024
First forecast week: 5 – 11 February 2024
Second forecast week: 12 – 18 February 2024

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Drier conditions are predicted over parts of the northeastern Maritime Continent in Week 1 (5 – 11 February). In Week 2 (12– 18 February), drier conditions are predicted over parts of central and southern Mainland Southeast Asia.

Wetter conditions are predicted over parts of the western and central Maritime Continent in Week 2 (12 – 18 February).

Warmer than usual temperature is predicted over the Maritime Continent and the coastal parts of southern Mainland Southeast Asia in the next fortnight (5 – 18 February).

Cooler than usual temperature is predicted over parts of central and eastern Mainland Southeast Asia in Week 2 (12 – 18 February).

A Madden-Julian Oscillation (MJO) signal was present over the Western Pacific (Phase 7) at the start of February based on the RMM index. Most models predict this MJO signal to remain over the Western Pacific in the first week of the forecast period. While most models agree on the decay of the signal in the second week, the location is uncertain.