Monthly Archives: October 2022

October 28, 2022

Subseasonal Weather Outlook (31 October – 13 November 2022)

Issued: 28 October 2022
First forecast week: 31 October – 6 November
Second forecast week: 7 November – 13 November

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are expected over parts of the eastern Maritime Continent in the next fortnight (31 October – 13 November). Wetter conditions are also predicted over parts of the southwestern Maritime Continent in Week 2 (7 – 13 November).

Drier conditions are expected over much of central and eastern Mainland Southeast Asia in Week 1 (31 October – 6 November).

Cooler than usual temperature is expected over much of central and southeastern Mainland Southeast Asia in Week 1 (31 October – 6 November).

A Madden-Julian Oscillation (MJO) signal was present over the Western Pacific (Phases 6 and 7) towards the end of October based on the RMM Index. Most models forecast MJO activity to be predominantly over the Western Pacific in 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.

October 14, 2022

Subseasonal Weather Outlook (17 – 30 October 2022)

Issued: 14 October 2022
First forecast week: 17 October – 23 October
Second forecast week: 24 October – 30 October

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

For rainfall, wetter conditions are expected over much of the central Maritime Continent in the next fortnight (17 – 30 October). Wetter conditions are also predicted around the Malay Peninsula in Week 1 (17 – 23 October). Drier conditions are expected over much of western and central Mainland Southeast Asia in Week 1 (17 – 23 October).

For temperature, cooler than usual temperature is expected over much of central and eastern Mainland Southeast Asia in Week 1 (17 – 23 October), while warmer than usual temperature is predicted to develop over much of Myanmar in Week 2 (24 – 30 October). Over parts of the southern Maritime Continent, cooler than usual temperature is predicted over the next fortnight (17 – 30 October).

A Madden-Julian Oscillation (MJO) signal propagated to the Western Pacific (Phase 6) by the middle of October. Models forecast the MJO signal to remain over the Western Pacific (Phases 6 and 7) during most of the forecast period. However, there is significant variation in the strength of the MJO signal among the models.

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 September 2022

1. Overview

1.1 During September 2022, much of the ASEAN region experienced above-average rainfall (Figure 1). The largest positive anomalies (wetter conditions) were recorded over parts Viet Nam and southern Borneo based on both satellite-derived rainfall estimates datasets (GSMaP-NRT and CMORPH-Blended). In contrast to the above-average rainfall, much of Peninsular Malaysia, the Philippines as well as northern Myanmar, northern Laos PDR, northern Sumatra, and northern Papua experienced below- to near-average rainfall. The two datasets agree well over most of the ASEAN region. However, there are some discrepancies over the central Myanmar and northern Laos PDR where GSMaP-NRT recorded mix of below- to above-average rainfall whereas CMORPH-Blended recorded near-average rainfall.

1.2 The observed rainfall anomaly pattern of above-average rainfall for most of the Maritime Continent region are broadly consistent with the predictions from the subseasonal weather outlooks for September 2022 (5 – 18 September and 19 September – 2 October). For Mainland Southeast Asia, the southern parts overall experienced above average rainfall in September, where the subseasonal outlooks also predicted wetter conditions in the first half of the September. While the northern parts of Mainland Southeast Asia experienced a mix of below- to -above average rainfall for September, the subseasonal outlooks predicted drier conditions towards the end of the month.

Figure 1: Rainfall anomalies for September 2022 based on GSMaP-NRT data (left) and CMORPH-Blended data (right). The climatological reference period is 2001-2021. Green colour denotes above-average rainfall (wetter), while orange denotes below-average rainfall (drier).

1.3 The southeastern parts of the Maritime Continent and northwestern Myanmar experienced above-average temperatures during September 2022, with below- to near-average temperatures elsewhere (Figure 2). The warmest anomalies were recorded over Papua, with the coolest anomalies over parts of Thailand, Cambodia, southern Borneo, and southern Sumatra. Most of the cooler anomalies occurred for areas that also experienced above-average rainfall.

Figure 2: Temperature anomalies for September 2022 based on ERA-5 reanalysis. The climatological reference period is 2001-2021. Red colour denotes above-average temperature (warmer), while blue denotes below-average temperature (colder).

2. Climate Drivers

2.1 The Madden-Julian Oscillation (MJO) signal was weak or indiscernible for most of September 2022, based on the RMM Index below (Figure 3). As there was no significant MJO activity in the entire September, it would have little contribution to rainfall conditions over the ASEAN region.

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 tropical Pacific Ocean, La Niña conditions were present. Sea surface temperatures in the Nino3.4 region (used to monitor ENSO) and the atmospheric indicators over the tropical Pacific Ocean remain consistent with La Niña conditions. La Niña events tend to bring wetter-than-average conditions to much of the Maritime Continent during the September to November period. Over the Indian Ocean, a negative Indian Ocean Dipole (IOD) was present. Negative IOD tends to bring wetter-than-average conditions for much of Southeast Asia.

October 12, 2022

Alert20221012 – End of Dry Season for the Southern ASEAN Region

End of Dry Season for the Southern ASEAN Region

In the past week, there have been widespread showers over most parts of the southern ASEAN region which has helped to subdue the overall hotspot activity in the region and no significant smoke haze was observed from satellite imagery. Based on NOAA-20 satellite surveillance, no hotspots were detected in the southern ASEAN region on 10 and 11 October 2022

As the prevailing wet weather is forecast to persist over the southern ASEAN region in the coming days, the hotspot activity is expected to remain subdued

October 10, 2022

Review of Regional Haze Situation for September 2022

1.1 Southwest Monsoon conditions continued to be observed over the ASEAN region in September 2022, with the prevailing low-level winds blowing from the southeast for areas south of the Equator and mainly from the south to southwest for areas north of the Equator (Figure 1).

1.2 The weather over the ASEAN region in September 2022 was mostly rainy, except for parts of Java, Sulawesi, and the Lesser Sunda Islands where there were periods of drier conditions. During the last two weeks of the month, Typhoon Noru brought increased rainfall and strong winds to the northern part of the Philippines and the eastern and central parts of the Mekong sub-region, as it made landfall over Viet Nam on 28 September 2022 (Figure 1).

Figure 1: Average Daily Rainfall and Mean Winds for September 2022. (Source: JAXA GsMaP and GFS, respectively)

1.3 Hotspot activity in the ASEAN region was mostly subdued in September 2022 due to widespread shower activities. For the Mekong sub-region, hotspot counts were generally lower or comparable to previous years, with a majority of the hotspots detected in Viet Nam (Figure 3). Over the southern ASEAN region, despite this period of the year being its traditional dry season, hotspot counts were significantly lower compared to the same period in previous years (Figure 2).

Figure 2: Hotspot counts for the southern ASEAN region for the month of September (2018 – 2022). [Note: The hotspot counts from 2019 onwards are based on the NOAA-20 satellite, while those from 2018 are based on the Suomi-NPP satellite.]

Figure 3: Hotspot counts for the northern ASEAN region for the month of September (2018 – 2022). [Note: The hotspot counts from 2019 onwards are based on the NOAA-20 satellite, while those from 2018 are based on the Suomi-NPP satellite.]

1.4 During the review period, few to isolated hotspots were detected mainly in parts of Viet Nam, Kalimantan, Sulawesi, and the Lesser Sunda Islands on several days. In term of persistency, these hotspots were mostly short-lived and did not contribute to any significant smoke haze in September 2022 (Figure 4).

Figure 4: Distribution of hotspots detected in September 2022 based on NOAA-20 satellite surveillance.

Figure 5: Maximum fire intensity in September 2022 based on NOAA-20 satellite surveillance.

1.5 The overall fire intensity of hotspots detected over the ASEAN region was low in September 2022. No significant smoke haze was observed from satellite imageries and ground reports (Figure 5).