Monthly Archives: February 2020

February 28, 2020

Subseasonal Weather Outlook (1- 15 March 2020)

Subseasonal Weather Outlook (1 – 15 March 2020)

Issued 28 February 2020
Valid for weeks 1 and 2: 1 – 15 March 2020

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For the first fortnight of March 2020, there is an increased chance of wetter conditions over northern Viet Nam and most parts of the southern Maritime Continent. These conditions are expected to ease gradually in Week 2. Drier conditions are expected over northern Sumatra, Peninsular Malaysia, southern parts of Thailand and the Philippines throughout the fortnight.

For temperature, warmer conditions are expected over most parts of Southeast Asia.

Some models predict a weak Madden-Julian Oscillation (MJO) emerging over the Maritime Continent in the first week of March. This development may contribute to the wetter conditions in the southern Maritime Continent predicted by the models.

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.

February 25, 2020

Review of Regional Weather for January 2020

Print Version

1. Overview

1.1 During January 2020, the region between 0° and 10°N predominately experienced below-average rainfall (Figure 1). For south of the equator, there was a mixture of below- and above-average rainfall, with the largest positive anomalies (wetter conditions) over southern Borneo. The rainfall anomalies over mainland Southeast Asia were small, which is expected given that January is the drier time of the year for that region.

Figure 1: Rainfall anomalies for January 2020 based on ERA-5 reanalysis data (left) and CMORPH-Blended data (right). The climatological reference periods are 1981-2010 and 2001-2019 for ERA-5 and CMORPH-Blended data respectively. Green colour denotes above-average rainfall (wetter), while orange denotes below-average rainfall (drier).

1.2 Overall, most of Southeast Asia experienced above-average temperature during January 2020 (Figure 2). The largest anomalies occurred over northern Thailand, Laos and Viet Nam. Only western and northern Myanmar, and some parts of Cambodia, experienced near-average temperatures.

Figure 2: Temperature anomalies for the month of January 2020 based on ERA-5 reanalysis. The climatological reference period is 1981-2010. 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 developed over the Maritime Continent (Phase 4) during the first week of January 2020 (Figure 3). The signal strengthened rapidly, and then propagated eastwards with the main precipitation envelope reaching the Western Pacific (Phase 7). By the end of January, however, this MJO signal had weakened and became indiscernible. Phase 4 normally brings wetter conditions for much of Southeast Asia, while Phase 7 is associated with drier conditions. Phases 5 and 6 bring a mixture 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). 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 The strong positive Indian Ocean Dipole (IOD) event from 2019, which had been weakening since November 2019, continued to weaken and returned to the neutral state in January 2020. The IOD typically remains in the neutral phase during the season from January to April.

February 14, 2020

Subseasonal Weather Outlook (16 – 29 February 2020)

Subseasonal Weather Outlook (16- 29 February 2020)

Issued 14 February 2020
Valid for weeks 3 and 4: 16 – 29 February 2020

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For the second fortnight of February 2020, there is an increased chance of wetter conditions over most of the southern Maritime Continent. These conditions are expected to ease gradually in Week 4.

Drier conditions are expected over northern Sumatra and western coastal Peninsular Malaysia. Drier conditions are also expected over northern parts of Borneo and southern parts of the Philippines.

For temperature, warmer conditions are expected over much of the Maritime Continent and parts of Mainland Southeast Asia in Week 4. Colder conditions may occur in Week 3 over northeastern parts of Mainland Southeast Asia.

There are signs of an Madden-Julian Oscillation (MJO) emerging in Maritime Continent in the second week of February. However most models predict this MJO to weaken during the start of 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.

Review of Regional Haze Situation for January 2020

1.1 In Jan 2020, Northeast Monsoon conditions prevailed over the ASEAN region. During this period, which is the traditional dry season of the Mekong sub-region, persistent dry weather prevailed. In the southern ASEAN region, there were scattered rain showers on most days but there were also occasional dry periods in some areas, including Peninsular Malaysia, northern and central Sumatra (Fig. 1).

Figure 1: Average Daily Rainfall for Jan 2020. (Source: JAXA GsMaP)

1.2 In Jan 2020, the number of hotspots detected in the Mekong sub-region was higher than the same period in 2019 (Fig. 2).

Figure 2: Hotspot count for the northern ASEAN region for Jan 2013 – 2020. [Note: Hotspot count from year 2019 onward is based on the NOAA-20 satellite, and for the period from year 2013-2018 is based on the Suomi-NPP satellite.]

1.3 In the southern ASEAN region, hotspot activities remained generally subdued (Fig. 3).

Figure 3: Hotspot count for the southern ASEAN region for Jan 2013 – 2020. [Note: Hotspot count from year 2019 onward is based on the NOAA-20 satellite, and for the period from year 2013-2018 is based on the Suomi-NPP satellite.]

1.4 There were persistent hotspots detected in Cambodia, particularly in the northern and western provinces. Clusters of hotspots were also detected in northern, northeastern and central Thailand, eastern Myanmar, and southern parts of Lao PDR and Viet Nam (Fig. 4). In the southern ASEAN region, there were occasional isolated hotspots detected mainly in Peninsular Malaysia, Sumatra and Kalimantan.

Figure 4: Distribution of hotspots detected based on NOAA-20 satellite surveillance for Jan 2020.

1.5 Based on NOAA-20 satellite surveillance, hotspots with moderate to high fire intensity were detected mostly in northern Cambodia, central Thailand, eastern Myanmar, Lao PDR and southern Viet Nam. Some of these hotspots in northern and central Thailand and Cambodia emitted significant smoke haze on a number of days in Jan 2020.

Figure 5: Maximum fire intensity based on NOAA-20 satellite surveillance in Jan 2020.

1.6 Persistent hazy conditions were observed mainly in northern and central Thailand, and Cambodia. In eastern Myanmar, northern Lao PDR and southern Viet Nam, smoke haze was observed on some days. Blown by the prevailing winds, transboundary transport of smoke haze was observed on a few days from northern Thailand to northern Lao PDR, and from Cambodia to eastern Thailand.

Figure 6: Number of days with moderate to dense smoke haze observed over an area based on satellite imageries, ground observations and air quality reports in Jan 2020.

February 3, 2020

Use and Interpretation of Data for Fire and Haze Monitoring for the Mekong sub-region and Attachment Programme (13-16 January 2020)

As part of the ASMC 5-year Regional Capability Building Programme for ASEAN Member States, ASMC conducts regular training workshops in the area of land/forest fires and smoke haze monitoring and assessment using data from satellites. This year, the training workshop was held on 13 – 16 January 2020 together with a short attachment stint at ASMC for the Mekong sub-region comprising Cambodia, Lao PDR, Myanmar, Thailand and Vietnam. Five participants from the environment, forestry and pollution control sectors joined this year’s programme.

Workshop participants with meteorologists from the ASMC Forecast Office (left). Participants were briefed on the process of assessing the weather and haze situation in the Mekong sub-region (right).

The workshop included lectures for participants to gain foundational understanding of topics such as weather systems in Southeast Asia, sub-seasonal and seasonal predictions, interpretation of satellite imageries, data analysis methodologies, and dispersion modelling as a predictive tool. The lectures were supplemented with hands-on exercises in interpretation of satellite data. The participants also had a short attachment at the ASMC Forecast Office, where they worked with ASMC meteorologists to carry out near real-time assessment of the fire and haze situation in the Mekong sub-region.

Hands-on exercises for participants to practise their skills in analysing weather and satellite data to produce an outlook of the haze situation in the Mekong sub-region (left). Participants visited Meteorological Service Singapore’s Centre for Climate Research where they learnt how subseasonal and seasonal forecasts can augment haze monitoring and assessment efforts (right).

Ms Phayvone Sengphone, Research Officer from the Ministry of Natural Resources and Environment (MONRE), Lao PDR, felt that the lectures and activities conducted during the workshop were interesting and applicable to her work. She found the attachment stint useful in providing insights into ASMC’s operations.

Besides such training workshops focusing on monitoring and assessment of regional fires and smoke haze, three other workshops on the themes of Numerical Weather Prediction, Seasonal to Sub-seasonal Prediction, and ASEAN Climate Data, Analysis and Projections (ARCDAP) are also in the pipeline for this year.