Monthly Archives: July 2024

July 18, 2024

Events – Start of Dry Season for the Southern ASEAN region – 2024

MEDIA RELEASE

START OF DRY SEASON FOR THE SOUTHERN ASEAN REGION

Risk of hotspot and smoke haze development, despite possible La Niña conditions

Singapore, 17 July 2024 – Many parts of the southern ASEAN region^[1] have started to experience persistent drier weather conditions in recent days. This is due to a strengthening of the prevailing Southwest Monsoon, which causes the monsoon rainband to move further north of the Equator, away from the region. The ASEAN Specialised Meteorological Centre (ASMC) has hence issued Alert Level 1 for the southern ASEAN region on 17 July 2024, indicating the start of the dry season that is expected to last till September 2024.

2 With the drier conditions, there has been an increase in hotspot activity in the southern ASEAN region in the past few days. A total of 33 and 44 hotspots were detected on 15 July 2024 and 16 July 2024 respectively. Localised smoke plumes were observed to emanate from a few hotspots in Sumatra on some days.

3 The conditions in the tropical Pacific Ocean are currently neutral (neither El Niño nor La Niña²), with a possibility of La Niña conditions developing in the second half of the year. Based on the latest climate outlook, ASMC expects above-normal rainfall over most parts of the southern ASEAN region in the coming months. However, there is still a risk of hotspot and smoke haze development in the fire-prone areas, particularly during drier periods. Early precautionary and mitigation measures are advised to prevent the occurrence of fires and transboundary haze in the region.

4 For regular and ad-hoc updates of the regional weather and smoke haze situation and early warnings, please visit the ASMC website at https://asmc.asean.org.

[1] The southern ASEAN region comprises Brunei Darussalam, Indonesia, Malaysia, Singapore and southern Thailand.

[2] La Niña conditions tend to bring wetter conditions to many parts of the southern ASEAN region.

– End –

Review of Regional Haze Situation for June 2024

1.1 Southwest Monsoon conditions were fully established over the ASEAN region in June 2024. Over the Philippines and much of the southern ASEAN region, the prevailing winds blew mainly from the southeast. The prevailing winds over the Mekong sub-region were mostly southwesterly or westerly while the regions close to the Equator experienced winds that were mostly light and variable in direction (Figure 1).

1.2 During the review period, rainy weather prevailed over most parts of the ASEAN region. In particular, moderate to heavy showers fell on several days over the Philippines, southern Myanmar and northern Viet Nam. Drier conditions were observed over Java and the Lesser Sunda Islands (Figure 1).

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

1.3 Hotspot activity in the ASEAN region was mostly subdued in June 2024 due to the prevailing wet weather conditions. The total number of hotspots were lower or comparable to previous years of the same period (Figure 2 and 3).

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

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

1.4 In June 2024, a few to isolated hotspots were detected in the ASEAN region, particularly in the southern and central parts of Viet Nam where the fires were more persistent and intense(Figure 4 and 5). There was no significant smoke haze observed via satellite imagery and ground reports.

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

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

Subseasonal Weather Outlook (22 July – 4 August 2024)

Issued: 18 July 2024
First forecast week: 22 – 28 July 2024
Second forecast week: 29 July – 4 August 2024

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In Week 1 (22 – 28 July), wetter conditions are predicted over most of northern Mainland Southeast Asia. In Week 2 (29 July – 4 August), drier conditions are predicted over most of the southern half of Mainland Southeast Asia and parts of northern and central Philippines.

Elsewhere, drier conditions are predicted over much of the equatorial region in Week 1 (22 – 28 July), while wetter conditions are predicted over this region in Week 2 (29 July – 4 August).

Warmer than usual temperature is predicted over the Maritime Continent and parts of southern and eastern Mainland Southeast Asia in the next fortnight (22 July – 4 August).

A Madden-Julian Oscillation (MJO) signal was present over the Maritime Continent (Phases 4 and 5) during mid-July based on the RMM index. While most models predict this signal to decay and become indiscernible during the forecast period, some models predict the signal to propagate to Phase 6 (Western Pacific) during Week 1 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.

Review of Regional Weather for June 2024

1. Overview

1.1 During June 2024, much of northern half of Mainland Southeast Asia and the equatorial region experienced near- to above-average rainfall, while much of the southern half of Mainland Southeast Asia, southern parts of the Maritime Continent and most of the Philippines experienced near- to below-average rainfall (Figure 1). The largest negative (drier) anomalies were recorded over the central Philippines in GSMap-NRT (Figure 1, left) and over Cambodia in CMORPH-Blended (Figure 1, right). The larger positive (wetter) anomalies were recorded over northern Myanmar and northeastern Borneo (in both GSMap-NRT and CMORPH-Blended).

1.2 The observed rainfall anomaly pattern of a mix of below- and above-average rainfall over the northern ASEAN region is consistent with the predictions from the subseasonal weather outlooks for June 2024 (27 May – 9 June 2024 , 10 – 23 June 2024 and 24 June – 7 July 2024).

Figure 1: Rainfall anomalies for June 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 much of the ASEAN region in June 2024 (Figure 2), with pockets of near-average temperature over parts of the region. The warmest anomalies (between 1 to 2°C above average) were recorded over western Myanmar as well as in smaller areas scattered over the northern Philippines and southeastern parts of Mainland Southeast Asia.

Figure 2: Temperature anomalies for June 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 inactive for much of June 2024, based on the RMM index (Figure 3). There was no active MJO signal for the first three weeks of June. An MJO signal developed in the Western Hemisphere and Africa (Phase 1) in the last week of June. The MJO signal remained weak as it propagated eastwards over the Indian Ocean (Phases 2 and 3), before becoming inactive again (at Phase 3) at the end of the month. For June, Phases 2 and 3 tend to bring wetter conditions to parts of the Maritime Continent (the western Maritime Continent in Phase 2, much of the region for Phase 3).

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 The El Niño event has ended, although the lingering effect of the El Niño still likely contributed to the warmer temperatures observed in Figure 2.

July 17, 2024

Alert20240717 – Start of Dry Season for the Southern ASEAN Region

Start of Dry Season for the Southern ASEAN Region

Southwest Monsoon conditions have been established over the southern ASEAN region with the prevailing winds blowing predominantly from the southeast or southwest. Persistent dry weather conditions have developed over most parts of the southern ASEAN region in recent days. There were a total of 33 and 44 hotspots detected in the southern ASEAN region, mainly in parts of Sumatra and Kalimantan on 15 July 2024 and 16 July 2024 respectively.

Many parts of the southern ASEAN region may experience periods of drier weather in the coming months. An increase in hotspot and smoke haze activity can be expected, particularly over fire-prone areas of the region.

ASMC Media Release – Start of Dry Season for the Southern ASEAN Region

July 3, 2024

Subseasonal Weather Outlook (8 – 21 July 2024)

Issued: 3 July 2024
First forecast week: 8 – 14 July 2024
Second forecast week: 15 – 21 July 2024

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In Week 1 (8 – 14 July), drier conditions are predicted over most of northern Mainland Southeast Asia.

In Week 2 (15 – 21 July), wetter conditions are predicted over the southern half of Mainland Southeast Asia, while drier conditions are predicted over most of the southern half of the Maritime Continent.

Warmer than usual temperature is predicted over most of the Maritime Continent and northern Mainland Southeast Asia in the next fortnight (8 – 21 July).

No clear Madden-Julian Oscillation (MJO) signal was present at the start of July based on the RMM index. Most models predict no significant MJO activity during the forecast period.