Bulletin

09 DEC 2024

ASEAN Climate Outlook Forum

Twenty Third Session of the ASEAN Climate Outlook Forum (ASEANCOF-23)

26-29 November 2024, Online

Consensus Bulletin for december-January-February (DJF) 2024/2025 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-third session of ASEANCOF (ASEANCOF-23) was organised by the Department of Meteorology and Hydrology of Lao PDR, RIMES, the ASEANCOF Working Group, and WMO. Participants from the NMHSs of ASEAN Member States created a consensus forecast for the boreal winter monsoon 2024/2025 in the ASEAN region. The consensus for the December-January-February (DJF) 2024/2025 outlook was achieved through an online session, which included presentations from ASEAN NMHSs, questionnaires, and discussions regarding the current climate conditions and predictions for Southeast Asia. The theme of ASEANCOF-23 was Agriculture and Climate Services. On the last day of ASEANCOF-23, a sharing session was held which included updates from ASEANCOF-22 around the use of climate services for agriculture.

Conditions and Outlook

Recent analysis of sea surface temperature (SST) anomalies over the equatorial Pacific shows average to slightly below-average SSTs across the equatorial Pacific Ocean, and along with atmospheric indicators such as trade wind strength and cloudiness, indicate La Niña-like conditions. In the Indian Ocean, the positive Indian Ocean Dipole did not develop, and based on the recent analysis, the SST anomalies show signs of a negative Indian Ocean Dipole.

The international climate outlooks predict that a weak La Niña is likely to develop sometime in December 2024 and persist until February 2025. After DJF 2024/2025, most models predict La Niña conditions to transition back to ENSO neutral.

There is a chance that a short-lived negative Indian Ocean Dipole (IOD) may be present during December 2024 based on the model predictions. However, the IOD is predicted to be neutral during January – February 2025.

The onset of the Northeast Monsoon season has been or is expected to be near or later than average for much of the northern ASEAN region. The onset for much of the southern ASEAN region has been or is expected to be near average. The strength of the Northeast Monsoon is predicted to be near average over most of Southeast Asia.

During DJF 2024/2025, tropical cyclone frequency is predicted to be near average around the Philippine Sea, the Bay of Bengal, and South China Sea.​

RAINFALL

For the upcoming boreal (Northern Hemisphere) winter season (DJF 2024/2025):

Over the Maritime Continent, near- to above-normal or above-normal rainfall is predicted for much of the region, including the Philippines, Brunei Darussalam, and Singapore. The exception is over parts of the equatorial region, where a mix of near-normal and normal- to below-normal rainfall is predicted.

Across Mainland Southeast Asia, near- to above-normal or above-normal rainfall is predicted for much of the southern part, including southern Myanmar, southern Thailand, Cambodia, southern Lao PDR, and southern Viet Nam. Below-normal rainfall is predicted for northern Viet Nam and elsewhere, near-normal rainfall is predicted.

For the upcoming boreal (Northern Hemisphere) winter season (DJF 2024/2025):

Near- to above-normal or above-normal temperature is predicted over most of the ASEAN region. The exception is over northern Lao PDR, and northeast and central Viet Nam, where near-normal temperature is predicted. The highest chance of above-normal temperature is over northern and central Myanmar, northern Thailand, southern Lao PDR, Singapore, the southern Philippines, and Brunei Darussalam.

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 2024/2025 Season

The following maps provide the probabilistic outlooks for DJF 2024/2025 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 Global Producing Centres, 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. The Forum would also like to thank DMH Lao PDR for hosting the forum virtually, as well as trainers from RIMES and UK Met Office.