Monthly Archives: November 2022

November 30, 2022

19th ASEAN COF (Nov 2022, Online)

Nineteenth Session of the ASEAN Climate Outlook Forum (ASEANCOF-19)

21 to 25 Nov 2022, MSS

Consensus Bulletin for December-January-February (DJF) 2022/2023 Season

The ASEAN Climate Outlook Forum (ASEANCOF) is an avenue to collaboratively develop consensus-based seasonal climate outlooks and related information on a regional scale. The forum’s outlook and its activities contribute significantly to one of the key roles of the ASEAN Specialised Meteorological Centre (ASMC), which is to conduct climate and seasonal prediction for the Association of Southeast Asian Nations (ASEAN) region through pooling the expertise of ASEAN National Meteorological and Hydrological Services (NMHSs). In 2021, the ASEANCOF Working Group was established with the goal to guide and support the long-term development of ASEANCOF, in particular with regard to the implementation of objective outlooks.

The Nineteenth session of ASEANCOF (ASEANCOF-19) was organised by Meteorological Service Singapore (MSS) in collaboration with ASMC and the ASEANCOF Working Group. Participants from the NMHSs of ASEAN Member States created a consensus forecast for the boreal winter monsoon 2022-2023 in the ASEAN region. The consensus for the December-January-February (DJF) 2022-2023 outlook was achieved through an online session, which included presentations from different Global Producing Centres (GPCs), NMHSs, questionnaires, and discussions regarding the current climate conditions and predictions for Southeast Asia. In particular, ASEANCOF considered the influence of the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on the climate system over Southeast Asia. The theme of ASEANCOF-19 was climate services for agriculture. On the last day of ASEANCOF-19, a webinar was held involving both producers and users of seasonal outlooks, including presentations on using climate services for agriculture.

Conditions and Outlook

Recent analysis of sea surface temperature (SST) anomalies over the equatorial Pacific shows below-average SSTs across the central and eastern equatorial Pacific Ocean indicative of La Niña.

The international climate outlook predicts that the La Niña is likely to weaken during DJF 2022/2023, although overall still indicates La Niña conditions. After DJF 2022/2023, most models predict the ENSO state to gradually return to neutral.

While a negative Indian Ocean Dipole (IOD) was present for much of the second half of 2022, models predict the IOD to return to neutral by the end of 2022.

The onset of the Northeast monsoon season has been or is expected to be near average in many parts of the region. Over much of Southeast Asia, the strength of the Northeast monsoon is expected to be near average or stronger than average, based on model predictions and supported by the La Niña conditions.

Overall, the tropical cyclone frequency is expected to be near average in the Bay of Bengal and around the South China Sea and the Philippine Sea.

Taking into consideration the national level forecasts, the present state of the climate, and the forecasts available from the GPCs, ASEANCOF-19 agreed on the following consensus-based outlook for DJF 2022/2023 over the ASEAN region:

RAINFALL

Over the Maritime Continent, a mix of below to above normal rainfall is predicted. In particular, near to above normal rainfall is most likely over much of the Philippines and Brunei Darussalam, while near normal rainfall is most likely over much of Malaysia and Singapore.

Over Mainland Southeast Asia, below normal rainfall is most likely over northern parts, including northern Myanmar as well as northern Viet Nam. Above normal rainfall is most likely over southern and southeastern Mainland Southeast Asia, including southern Thailand, parts of Cambodia, and southern Viet Nam. Elsewhere, near normal rainfall is predicted.¹

¹This is based on the climatology period 1991-2020. However, at the national level, Myanmar is using the 1981-2010 climatology as their base period.

TEMPERATURE

Over the ASEAN region, a mix of below- to above-normal temperature is predicted. Above normal temperature is most likely over parts of Myanmar, northwestern Viet Nam and the eastern Maritime Continent, while below to near normal temperature is most likely over southeastern Mainland Southeast Asia. Elsewhere, near or near to above normal temperature is predicted.²

²This is based on the climatology period 1991-2020. However, at the national level, Myanmar is using the 1981-2010 climatology as their base period.

Refer to Annex A for reference on what is meant by “above, near, or below normal” in the outlook. For more information on the boreal (Northern Hemisphere) summer monsoon outlook and further updates on the national scale, the relevant NMHSs should be consulted (see Annex B).

Consensus Maps for DJF 2022/2023 Season

The following maps provide the probabilistic outlooks for DJF 2022/2023 season in terms of tercile categories of “Above Normal” (AN: upper tercile), “Near Normal (NN: middle tercile) and “Below Normal” (BN: lower tercile).

PROBABILISTIC RAINFALL OUTLOOK

PROBABILISTIC TEMPERATURE OUTLOOK

Meeting Documents

ASEANCOF-19 Outlook Bulletin

Acknowledgements

ASEANCOF would like to convey its appreciation to the NMHSs of the ASEAN Member States for sharing their national level forecasts, the GPCs, the Southeast Asia Regional Climate Centre – Network, RIMES, UN ESCAP, and other partners of ASEANCOF for sharing their products and expertise, and the World Meteorological Organization Regional Office in Asia and the Southwest Pacific (WMO-RAP) for their continued support of ASEANCOF.

November 25, 2022

Subseasonal Weather Outlook (28 November – 11 December 2022)

Issued: 25 November 2022
First forecast week: 28 November – 4 December
Second forecast week: 5 December – 11 December

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are predicted over much of eastern and southern Mainland Southeast Asia, and the Philippines in the next fortnight (28 November – 11 December). Wetter conditions are also predicted over the southeastern Maritime Continent in Week 1 (28 November – 4 December).

For temperature, warmer than usual temperature is expected over much of Myanmar in the next fortnight (28 November – 11 December).

During the third week of November, a Madden-Julian Oscillation (MJO) signal propagated to the Western Pacific (Phase 6). Most models forecast the MJO signal to continue propagating eastwards over the Western Pacific (Phase 7) and to dissipate during Week 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.

November 11, 2022

Review of Regional Weather for October 2022

1. Overview

1.1 During October 2022, much of the ASEAN region experienced above-average rainfall (Figure 1). The largest positive anomalies (wetter conditions) were recorded over northern Philippines (due to Tropical Storm Nalgae which made landfall in end-October), based on both satellite-derived rainfall estimates datasets (GSMaP-NRT and CMORPH-Blended). In contrast to the above-average rainfall, northwest Mainland Southeast Asia experienced near- to above-average rainfall, while parts of northern Viet Nam and Papua experienced below- to near-average rainfall. The two datasets agree well over most of the ASEAN region. However, there are some discrepancies over parts of the western Maritime Continent, Borneo and southern Viet Nam, where GSMaP-NRT recorded near- to above-average rainfall whereas CMORPH-Blended recorded a mix of below- to above-average rainfall.

1.2 The observed rainfall anomaly pattern of above-average rainfall for much of the Maritime Continent region is broadly consistent with the predictions from the subseasonal weather outlooks for October 2022 (3 – 16 October and 17 – 30 October). Overall, much of Mainland Southeast Asia experienced near- to above-average rainfall for October. The subseasonal outlooks predicted drier conditions over western and central Mainland Southeast Asia for middle of the October. The observed anomalies also supported this with lower rainfall anomalies compared to the rest of the region.

Figure 1: Rainfall anomalies for October 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 northwestern and eastern parts of the ASEAN region experienced above-average temperatures during October 2022, with below- to near-average temperatures elsewhere (Figure 2). The warmest anomalies were recorded around Papua, with the coolest anomalies over parts of southern Sumatra, southern Borneo and eastern Java. Most of the cooler anomalies occurred for areas that also experienced above-average rainfall.

Figure 2: Temperature anomalies for October 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 There was no discernible Madden-Julian Oscillation (MJO) signal in the first week of October, based on the RMM Index (Figure 3). An MJO signal emerged over the Western Pacific (Phase 6) and propagated eastward to Phase 7 in the second week of October. This signal then maintained its strength and remained in Phase 7 for the rest of the October. Typically, during this time of the year, Phase 6 tends to bring wetter conditions for eastern Maritime Continent while Phase 7 tends to bring drier conditions for 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 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.

Subseasonal Weather Outlook (14 – 27 November 2022)

Issued: 11 November 2022
First forecast week: 14 November – 20 November
Second forecast week: 21 November – 27 November

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Wetter conditions are predicted over much of the southern and eastern Maritime Continent in the next fortnight (14 – 27 November). Wetter conditions are also predicted over the southern half of Mainland Southeast Asia in Week 1 (14 – 20 November), easing in Week 2 (21 – 27 November).

Drier conditions are predicted in Week 2 (21 – 27 November) over the western Maritime Continent and some parts of the central Maritime Continent.

Warmer than usual temperatures are expected over northeastern Mainland Southeast Asia in the next fortnight (14 – 27 November).

In mid-November, no discernible Madden-Julian Oscillation (MJO) signal was present based on the RMM index. While some models predict an MJO activity over the eastern Maritime Continent and the Western Pacific (Phases 5 and 6) during the forecast period, others predict no significant MJO activity.

November 8, 2022

Review of Regional Haze Situation for October 2022

1.1 Southwest Monsoon conditions transitioned to the inter-monsoon in late October 2022 as the monsoon rainband moved over the Equator and the prevailing winds gradually weakened and turned light and variable over the equatorial ASEAN region (Figure 1).

1.2 Rainy conditions prevailed over most parts of the ASEAN region in October 2022, except for parts of northeastern Mekong sub-region. In the 3rd week of October, Typhoon Nesat made landfall in the Philippines and contributed to the heavy rainfall over northern parts of the country. It also brought increased rainfall over central Viet Nam as it weakened into a tropical depression before making landfall (Figure 1). The southern ASEAN region experienced continued shower activities during the review period and Alert Level 0 was issued for the region on 12 October 2022, signaling the end of its traditional dry season.

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

1.3 In October 2022, overall hotspot activity in the ASEAN region was subdued under wet weather conditions. While majority of the hotspots in the Mekong sub-region were detected in Viet Nam, the hotspot counts for northern ASEAN region were generally lower or comparable to the counts in previous years (Figure 2). For the southern ASEAN region, hotspot counts were significantly lower compared to the same period in previous years (Figure 3).

Figure 2: Hotspot counts for the northern ASEAN region for the month of October (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 southern ASEAN region for the month of October (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 For the October 2022 review period, few to isolated hotspots were detected in the ASEAN region on most days. In term of persistency, these hotspots were mostly short-lived and did not contribute to any significant smoke haze in October 2022 (Figure 4).

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

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

1.5 The overall fire intensity of hotspots detected over the ASEAN region was low in October 2022. On most days, no smoke plumes were discernable from satellite imagery (Figure 5).