Monthly Archives: July 2023

July 28, 2023

Alert20230728 – Activation of Alert Level 2 for Kalimantan

Activation of Alert Level 2 for Kalimantan

In recent days, prevailing dry weather conditions over the southern ASEAN region have resulted in an escalation in hotspot and smoke haze activities. Based on satellite surveillance, moderate smoke haze was observed to emanate from clusters of hotspots detected in the western and southern parts of Kalimantan. In particuar, transboundary haze was observed to drift northwards from the hotspot clusters in West Kalimantan into western Sarawak in East Malaysia. 359 and 393 hotspots were detected in Kalimantan on 26 and 27 July 2023 respectively from the NOAA-20 satellite.

The prevailing dry weather conditions are forecast to continue over Kalimantan in the coming days, with the prevailing winds likely to blow from the southeast or southwest. Under these conditions, the hotspot and smoke haze situation could worsen with an increased risk of transboundary smoke haze occurrence.

July 23, 2023

Subseasonal Weather Outlook (24 July – 6 August 2023)

Issued: 21 July 2023
First forecast week: 24 July – 30 July 2023
Second forecast week: 31 July – 6 August 2023

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Drier conditions are predicted over much of the southern ASEAN region in Week 1 (24 – 30 July). These drier conditions are predicted to persist over the central and eastern parts of the mentioned region in Week 2 (31 July – 6 Aug).

Wetter conditions are predicted over the northern half of the Philippines in Week 1 (24 – 30 July). Wetter conditions are also predicted over parts of the western Maritime Continent in Week 2 (31 July – 6 Aug).

Warmer than usual temperature is predicted over much of the Maritime Continent in the next fortnight (24 July – 6 Aug). Warmer than usual temperature is also predicted over northern Mainland Southeast Asia in Week 1 (24 – 30 July).

No clear Madden-Julian Oscillation (MJO) signal was present in the third week of July. Most models predict no significant MJO signal during 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.

Subseasonal Weather Outlook (26 June – 9 July 2023)

Issued: 23 June 2023
First forecast week: 26 June – 2 July 2023
Second forecast week: 3 July – 9 July 2023

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For rainfall, wetter conditions are predicted over parts of the western and central Maritime Continent and much of the Philippines in Week 1 (26 June – 2 July). Drier conditions are predicted over parts of the southeastern Maritime Continent in Week 1 (26 June – 2 July).

For temperature, warmer than usual temperature is expected over much of the ASEAN region in the next fortnight (26 June – 9 July), including most of Mainland Southeast Asia, the Malay Peninsula, the Philippines, and the southern and southeastern Maritime Continent.

No clear Madden-Julian Oscillation (MJO) signal was present in the third week of June based on the RMM Index. Most models predict no significant MJO signal during Week 1.

July 14, 2023

Review of Regional Weather for June 2023

1. Overview

1.1 During June 2023, a mix of below- to above-average
rainfall was recorded over the ASEAN region. Over Mainland Southeast Asia,
above-average rainfall was recorded in the eastern parts of the region, while
a mix of below- to above-average rainfall was recorded over the rest of the
region. Over the Maritime Continent, above-average rainfall was recorded over
the western Maritime Continent, with a mix of below- to above-average rainfall
elsewhere. The largest positive anomalies were over northeastern Borneo for
both the GSMaP-NRT (Figure 1, left) and CMORPH-Blended (Figure 1, right)
satellite-derived rainfall estimates.1.2 The observed rainfall anomaly pattern of below- to
near-average rainfall over the ASEAN region is broadly consistent with the
predictions from the subseasonal weather outlooks for June 2023 (29 May – 11 June 2023</a >,
12 – 25 June 2023</a >
and
26 June – 9 July 2023</a >).

Figure 1: Rainfall anomalies for June 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 Above-average temperatures were recorded over most of
Mainland Southeast Asia, with near- to above-average temperature over most of
the Maritime Continent. Near- to below-average temperatures were recorded over
the southern Maritime Continent. The warmest anomalies (more than 2 °C
above-average) were recorded over southern parts of the Malay Peninsula, Lao
PDR and northeast Thailand.

Figure 2: Temperature anomalies for June 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) was active at the start
of June 2023. An MJO signal propagated eastwards from the Western Hemisphere
and Africa (Phase 1) and to the Indian Ocean (Phases 2 and 3) in the first
half of June. In Week 3, the MJO signal weakened and became insignificant. An
MJO signal re-emerged in Week 4 over the Western Hemisphere and Africa (Phase
1) and propagated eastwards to the Indian Ocean (Phase 2). Typically for June,
Phases 1 and 2 tends to bring drier conditions in northern Southeast Asia
while Phases 2 and 3 tend 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 Over the past month, there have been signs of El
Niño-like conditions. El Niño sea surfaces temperatures indices are near or
exceeding El Niño thresholds, whereas key atmospheric indicators (cloudiness
and wind anomalies) displayed neutral conditions for most of June.

July 7, 2023

Subseasonal Weather Outlook (10 – 23 July 2023)

Issued: 7 July 2023
First forecast week: 10 July – 16 July 2023
Second forecast week: 17 July – 23 July 2023

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are predicted over parts of the southeastern Maritime Continent in Week 1 (10 – 16 July) and much of Mainland Southeast Asia in Week 2 (17 – 23 July). Wetter conditions are also predicted over much of the Philippines in the next fortnight (10 – 23 July).

Drier conditions are predicted over parts of the western and central equatorial region in Week 2 (17 – 23 July).

Warmer than usual temperature is expected over much of the northern ASEAN region in Week 1 (10 – 16 July). Warmer temperatures are then predicted over much of the southern ASEAN region in Week 2 (17 – 23 July).

No clear Madden-Julian Oscillation (MJO) signal was present in the first week of July based on the RMM Index. Most models predict no significant MJO signal during the next fortnight.

July 6, 2023

Review of Regional Haze Situation for June 2023

1.1 Southwest Monsoon conditions were fully established in June 2023, with the passage of the monsoon rainband north of the Equator. The prevailing winds over areas north of the equator blew mainly from the southeast or southwest, while the prevailing winds blew mostly from the east or southeast (Figure 1).

1.2 Brief periods of dry weather conditions were observed over parts of southern Sumatra, southern Kalimantan, Java, and the Lesser Sunda Islands. Elsewhere in the ASEAN region, shower activities were observed on most days during the month (Figure 1).

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

1.3 There was an increase in overall hotspot activity in June 2023 over the southern ASEAN region due to brief periods of dry conditions, with the hotspot counts in the region higher or comparable to previous years (Figure 2). In particular, the highest hotspot activity was detected in Sumatra, and the hotspot counts for both Sumatra and Kalimantan were the highest in 5 years. Over the Mekong sub-region, the overall hotspot count was mostly lower than in previous years (Figure 3).

Figure 2: Hotspot counts for the southern ASEAN region for June (2019-2023) based on NOAA-20 satellite surveillance.

Figure 3: Hotspot counts for the northern ASEAN region for June (2019-2023) based on NOAA-20 satellite surveillance.

1.4 Hotspot activities were more persistent in parts of western and central Sumatra, as well as West Kalimantan during the review period of June 2023. Localised smoke plumes were also observed to emanate from a few hotspots in Sumatra and Kalimantan on some days (Figures 6 and 7). However, the overall fire intensity has generally remained low.

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

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

Figure 6: Localised smoke plumes moving in the north-northwest direction were observed in central Sumatra on 20 June 2023. (Source: Himawari-9 satellite surveillance)

Figure 7: A localised smoke plume moving in the northeast direction was observed to emanate from a hotspot in western Kalimantan on 26 June 2023. (Source: NOAA-20 satellite surveillance)