Monthly Archives: February 2023

February 28, 2023

Hotspot and Haze Assessment (H2A) Workshop 2023 for the ASEAN Region, Singapore 21 – 23 February 2023

The ASEAN Specialised Meteorological Centre (ASMC) conducted the Hotspot and Haze Assessment Workshop for ASEAN Member States over three days from 21-23 February 2023 at the Furama City Centre in Singapore. This workshop is part of a series of workshops and fora held under the ASMC Regional Capability-building Programme (ACaP) which has been extended till 2027. This marked the first time since 2020 that this workshop was held physically, with virtual workshops conducted in recent years during the pandemic.

The workshop served to bring together stakeholders from the environment and meteorological sectors to learn and share on their home country experiences in preparation for the dry season. Topics covered during the workshop included remote sensing, fire and haze detection using satellites, sub-seasonal and seasonal prediction, meteorological instrumentation and dispersion modelling. Lecturers were from the ASMC as well as from Met Malaysia, who presented on the Fire Rating Danger System (FDRS) for Southeast Asia. Representatives from the ASEAN Environment Division were also present at the workshop.

Figure 1: The participants posed for a group photograph with staff from ASMC

Figure 2: ASMC Director of Operations, Mr Lesley Choo officiates the opening of the workshop.

The Workshop included a mix of lectures, discussions and quizzes to introduce participants to key concepts required to utilise meteorological products for fires and haze monitoring, assessment and prediction. Participants also had the opportunity to visit the ASMC operations and satellite centre, as well as a local air quality monitoring station during the workshop. Participants shared at the end of the workshop that that the lectures covered were beneficial and very informative and appreciated the activities, preparations, as well as sharing sessions conducted during the workshop.

Figure 3: Activities conducted during the workshop were well-received by the participants.

Figure 4: Participants listening intently during the tour of the ASMC Operations Centre.

February 17, 2023

Subseasonal Weather Outlook (20 February – 5 March 2023)

Issued: 17 February 2023
First forecast week: 20 February 2023 – 26 February 2023
Second forecast week: 27 February 2023 – 5 March 2023

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over the western Maritime Continent in the next fortnight (20 February – 5 March). Wetter conditions are also expected over the northeast Maritime Continent in Week 1 (20 – 26 February).

Cooler than usual temperature is expected over most of central and eastern Mainland Southeast Asia and also over parts of the western Maritime Continent in the next fortnight (20 February – 5 March).

A Madden-Julian Oscillation (MJO) signal was present over the Western Pacific (Phases 6 and 7) in the middle of February. Models predict this MJO signal to continue propagating eastwards and then decay in Week 1 over the Western Hemisphere (Phases 8 and 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.

February 16, 2023

Review of Regional Weather for January 2023

1. Overview

1.1 During January 2023, a mix of below- to above-average rainfall was recorded over the Maritime Continent, with much of the northern half of the region receiving above-average rainfall, and the much of the southern half receiving below-average rainfall (Figure 1). Near-average rainfall was recorded over most of Mainland Southeast Asia, except for parts of eastern Mainland Southeast Asia where above-average rainfall was recorded. The largest positive anomalies (wetter conditions) were recorded over the northeastern Maritime Continent for both the GSMaP-NRT (Figure 1, left) and CMORPH-Blended (Figure 1, right) satellite-derived rainfall estimates, along with parts of the western Maritime Continent for GSMaP-NRT. The largest negative anomalies (drier conditions) were recorded over parts of southern Borneo, southern Sulawesi, and Java, with CMORPH-Blended data showing relatively drier anomalies as compared to GSMaP-NRT data.

1.2 The observed rainfall anomaly pattern of a mix of below- to above-average rainfall for the Maritime Continent and the above-average rainfall for eastern Mainland Southeast Asia are broadly consistent with the predictions from the subseasonal weather outlooks for January 2023 (26 December 2022 – 8 January 2023, 9 – 22 January 2023 and 23 January – 5 February 2023).

Figure 1: Rainfall anomalies for January 2023 based on GSMaP-NRT data (left) and CMORPH-Blended data (right). The climatological reference period is 2001-2022. Green colour denotes above-average rainfall (wetter), while orange denotes below-average rainfall (drier).

1.3 Warmer-than-average temperatures were recorded over northwestern Mainland Southeast Asia and parts of southeastern Maritime Continent, whereas cooler-than-average temperatures were observed over much of central and eastern Mainland Southeast Asia. Elsewhere in the ASEAN region, near-average temperatures were observed. The warmest anomalies were recorded over Myanmar and the coolest over the eastern Mainland Southeast Asia.

Figure 2: Temperature anomalies for January 2023 based on ERA-5 reanalysis. The climatological reference period is 2001-2022. Red colour denotes above-average temperature (warmer), while blue denotes below-average temperature (colder).

2. Climate Drivers

2.1 A Madden-Julian Oscillation (MJO) signal was present over the Western Pacific (Phases 6 & 7) at the start of January. This signal weakened in the first week of January, with no clear MJO signal present in based on the RMM diagram until the second half of the month. By the end of the third week of January, the MJO signal strengthened over the Indian Ocean (Phase 3). Typically, during this time of the year, Phase 7 tends to bring drier conditions to the western Maritime Continent, whereas 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 La Niña conditions were present over the tropical Pacific. 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, though there are signs of weakening. La Niña events tend to bring wetter-than-average conditions to much of the Maritime Continent during the December to February period.

February 6, 2023

Review of Regional Haze Situation for January 2023

1.1 Northeast Monsoon conditions continued to be observed over the ASEAN region in January 2023, with the prevailing low-level winds blowing predominantly from the northeast or east over areas north of the Equator and mainly from the west or northwest for areas south of the Equator (Figure 1). The strengthening of high-pressure systems over the northern Asian continent also brought a surge of strong northeasterly winds or monsoon surge over the South China Sea during the last week of January 2023.

1.2 In January 2023, dry weather prevailed over much of the Mekong sub-region under the influence of the Northeast Monsoon. As a result of the persistent dry conditions, an escalation in hotspot activity and development of smoke haze was observed in many parts of the sub-region from the second half of the month. On 27 January 2023, Alert Level 2 was activated for the Mekong sub-region as hotspot counts were persistently high and there was an increasing risk of transboundary haze. Elsewhere, rainy weather prevailed over the southern ASEAN region and the Philippines on most days of the month. In particular, monsoon surges contributed to increased rainfall over southern Peninsular Malaysia, Singapore, western Borneo, central Sumatra, and southern Philippines (Figure 1).

Figure 1: Average Daily Rainfall and Mean Winds for January 2023. (Source: JAXA GsMaP and GFS, respectively)

1.3 For January 2023, hotspot counts in the Mekong sub-region were slightly elevated compared to the same review period in 2022 (Figure 2). In particular, the highest hotspot activity was detected in Cambodia, and the hotspot count for Lao PDR and Viet Nam was slightly higher than the past 5 years. For the southern ASEAN region, hotspot activity remained generally subdued and the hotspot counts were lower or comparable to those in previous years (Figure 3).

Figure 2: Hotspot counts for the northern ASEAN region for the month of January (2019 – 2023) based on NOAA-20 satellite surveillance.

Figure 3: Hotspot counts for the southern ASEAN region for the month of January (2019 – 2023) based on NOAA-20 satellite surveillance.

1.4 During the review period, hotspot activity was widespread over the Mekong sub-region. On many days, clusters of hotspots were detected in northern and eastern Cambodia, as well as central Myanmar. Persistent hotspots were also detected in northern Viet Nam, as well as the northern and northeastern regions of Thailand. Over the southern ASEAN region, few hotspots were detected but most of them were short-lived (Figure 4).

Figure 4: Distribution of hotspots detected in January 2023 based on NOAA-20 satellite surveillance.

1.5 The overall fire intensity in the Mekong sub-region had increased in January 2023, particularly over the fire-prone areas in central Myanmar, and northern and eastern Cambodia (Figure 5). As a result, persistent and moderate smoke haze was observed in the vicinity of the hotspot clusters in Myanmar and Cambodia (Figure 6, 7, and 8). Localised smoke plumes and occasional hazy conditions were also observed in northern Thailand, northern Viet Nam, and parts of Lao PDR.

Figure 5: Maximum fire intensity in January 2023 based on NOAA-20 satellite surveillance.

Figure 6: Number of days with moderate to dense smoke haze observed in January 2023 based on satellite imagery, ground observations, and air quality reports.

Figure 7: Moderate smoke haze observed over central Myanmar on 22 January 2023, based on NOAA-20 satellite surveillance.

Figure 8: Moderate smoke haze emanated from the hotspot clusters detected in northern and eastern Cambodia on 31 January 2023, based on NOAA-20 satellite surveillance.

February 3, 2023

Subseasonal Weather Outlook (6 – 19 February 2023)

Issued: 3 February 2023
First forecast week: 6 February 2023 – 12 February 2023
Second forecast week: 13 February 2023 – 19 February 2023

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Drier conditions are expected over parts of the western and central Maritime Continent in Week 1 (6 – 12 February). These drier conditions are predicted to persist over the central Maritime Continent in Week 2 (13 – 19 February) and likely easing over the western Maritime Continent.

Wetter conditions are predicted over the northeastern Maritime Continent and southeastern coast of Mainland Southeast Asia in Week 2 (13 – 19 February).

Warmer than usual temperature is expected over much of the eastern half of Mainland Southeast Asia and much of the Philippines in Week 1 (6 – 12 February). Warmer than usual temperature is also expected over parts of the western and central Maritime Continent in Week 1, in line with the predicted drier conditions.

A Madden-Julian Oscillation (MJO) signal was present over the Indian Ocean (Phase 3) at the start of February. Models predict the MJO signal to propagate eastwards and reach the Maritime Continent (Phases 4 and 5) during the first week of the forecast period. Some models then predict this signal to continue propagating through the Maritime Continent to the Western Pacific (Phases 6 and 7), while others predict the signal to decay over the Maritime Continent.