Bulletin

05 JUN 2024

ASEAN Climate Outlook Forum

Twenty Second Session of the ASEAN Climate Outlook Forum (ASEANCOF-22)

27-30 May 2024, DMH Lao PDR

Consensus Bulletin for June-July-August (JJA) 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-Second session of ASEANCOF (ASEANCOF-22) 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 summer monsoon 2024 in the ASEAN region. The consensus for the June-July-August (JJA) 2024 outlook was achieved through a hybrid session, which included presentations from different NMHSs, questionnaires, and discussions regarding the current climate conditions and predictions for Southeast Asia. There was also two-day pre-COF training, conducted by the UK Met Office under the WISER Asia Pacific project and RIMES. The theme of ASEANCOF-22 was Agriculture and Climate Services, with a focus on drought. On the last day of ASEANCOF-22, a sharing session was held which included presentations from UN ESCAP, FAO, and WFP, as well as discussion on ways to improve ASEANCOF.

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 ENSO-neutral conditions. In the Indian Ocean, the Indian Ocean Dipole is also neutral.

The international climate outlook predicts that a La Niña is likely to develop sometime during JJA 2024. After JJA 2024, most models predict La Niña conditions to continue until the end of the year.

There is a chance that a weak positive Indian Ocean Dipole (IOD) may become established during JJA 2024 based on the model predictions. However, it is predicted to most likely be short-lived.

The onset of the Southwest monsoon season has been or is expected to be near average for much of Mainland Southeast Asia, apart from Thailand where the onset is later than average. The onset of the Southwest monsoon for much of the Maritime Continent has been or is expected to be near average. The strength of the Southwest monsoon is predicted to be near average over most of the Southeast Asia, based on model predictions.

Taking into consideration the national level forecasts, the present state of the climate, and the forecasts available from the GPCs, ASEANCOF-22 agreed on the following consensus-based outlook for JJA 2024 over the ASEAN region:  

RAINFALL

Above-normal rainfall is predicted over northern Myanmar, parts of Cambodia and parts of the equatorial region, including Brunei Darussalam and middle part of East Malaysia. Near- to above-normal rainfall is predicted over southern Thailand, western part of East Malaysia, and the southern Philippines, as well as parts of Mainland Southeast Asia including western Myanmar, northwestern Lao PDR, parts of Cambodia, and southern Viet Nam.

Below-normal rainfall is predicted over the western part of Northern Philippines. Below- to near- normal rainfall is predicted over southern Lao PDR, the rest of Northern Philippines, and southernmost parts of Southeast Asia.

TEMPERATURE

Above normal temperature is predicted over most of Southeast Asia, apart from over much of Myanmar, Lao PDR, Cambodia, Brunei Darussalam, and the Philippines where near- to above-normal temperature is predicted.

^{1 This 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 JJA 2024 Season

The following maps provide the probabilistic outlooks for JJA 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 Global Producing Centres, the Southeast Asia Regional Climate Centre – Network, RIMES, UN ESCAP, FAO, WFP, 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, with support from RIMES, and CREWS Cambodia and Lao PDR and WISER Asia Pacific for the funding support provided for the meeting.