30 NOV 2023
ASEAN Climate Outlook Forum
Twenty First Session of the ASEAN Climate Outlook Forum (ASEANCOF-21)
17, 20, 21, 23 Nov 2023, MSS
Consensus Bulletin for December-January-February (DJF) 2023-2024 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 Twenty-First session of ASEANCOF (ASEANCOF-21) was organised by Meteorological Service Singapore (MSS) in collaboration with ASMC and the ASEANCOF Working Group. ASEANCOF-21 marked 10 years since the first ASEANCOF was held in December 2013. Participants from the NMHSs of ASEAN Member States created a consensus forecast for the boreal winter monsoon 2023/2024 in the ASEAN region. The consensus for the December-January-February (DJF) 2023/2024 outlook was achieved through an online session, which included presentations from different NMHSs, questionnaires, and discussions regarding the current climate conditions and predictions for Southeast Asia. The theme of ASEANCOF-21 was ‘The Future of Climate Services in Southeast Asia’’. On the last day of ASEANCOF-21, a sharing session was held which included presentations on the review of 10 years of ASEANCOF, Pilot Hydrological Outlook Forum, and WISER Asia Pacific project.
Conditions and Outlook
Recent analysis of sea surface temperature (SST) anomalies over the equatorial Pacific shows well above-average SSTs over the Nino3.4 region, along with atmospheric indicators such as trade wind strength and cloudiness, indicating El Niño conditions. In the Indian Ocean, a positive Indian Ocean Dipole is present.
For DJF 2023/2024, the current El Niño conditions are likely to continue. After DJF 2023/2024, global climate models predict the El Niño conditions to gradually weaken, though continue to indicate El Niño conditions for much of the first half of 2024. The peak strength of the ongoing El Niño, based on Nino3.4 index, is predicted to be moderate to strong.
The positive IOD is predicted to weaken and return to IOD-neutral over DJF 2023/2024.
The onset of the Northeast monsoon season has been or is expected to be later than average for much of Mainland Southeast Asia, with near or later than average over some parts of the Maritime Continent. The strength of the Northeast monsoon is expected to be weaker than normal over most of the Southeast Asia, based on model predictions and supported by the ongoing El Niño conditions.
During DJF 2023/2024, tropical cyclone frequency is predicted to be below average around the Philippine Sea and the Bay of Bengal, and below to near average around South China Sea.
Taking into consideration the national level forecasts, the present state of the climate, and the forecasts available from the GPCs, ASEANCOF-21 agreed on the following consensus-based outlook for DJF 2023-24 over the ASEAN region:
RAINFALL
Over much of the Maritime Continent, below- to near-normal rainfall is predicted, apart from over the equatorial region, where a mix of below- to above-normal rainfall is predicted.
For Mainland Southeast Asia, a mix of near- to above-normal rainfall is predicted. Near- to above-normal rainfall is predicted over parts of northern and central Mainland Southeast Asia, while below- to near-normal rainfall is predicted mainly over western parts. Elsewhere over this region, near-normal rainfall is predicted.
TEMPERATURE
Near- to above-normal temperature is predicted over Southeast Asia. While above-normal temperature is predicted for most of the region, near-normal temperature is predicted over parts of northern and western Myanmar, and near- to above-normal temperature is predicted over parts of Lao PDR, Viet Nam, and the Philippines.
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 C).
Consensus Maps for DJF 2023/2024 Season
The following maps provide the probabilistic outlooks for DJF 2023/2024 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
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.
Back