10th ASEAN COF (May 2018, Online Correspondence)
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 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 ASEAN region through pooling the expertise of ASEAN National Meteorological Services.
The Tenth ASEANCOF (ASEANCOF-10) was organised by the Malaysian Meteorological Department in collaboration with the Meteorological Services Singapore as host of the ASEAN Specialised Meteorological Centre. Representatives from National Meteorological and Hydrological Services (NMHSs) of 10 ASEAN Member States created a consensus forecast for the summer monsoon 2018 in the ASEAN region. The consensus for June-July-August (JJA) 2018 outlooks was achieved through online correspondence. The consensus is made based on the completed questionnaires on current conditions and predictions for the Southeast Asia region. In particular, the forum took into account the significant influence of the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on the climate over Southeast Asia.
Conditions and Outlook for JJA 2018
Recent analysis of sea surface temperature (SST) anomalies over the tropical Pacific indicate an ENSO neutral state. The warmer than average SSTs during first quarter of 2018 over eastern Pacific weakened in May.
The international climate outlooks show ENSO-neutral conditions are now present and likely to continue during JJA 2018. The present neutral Indian Ocean Dipole (IOD) is expected to continue towards the later part of the year.
The Southwest Monsoon is predicted to be generally normal throughout Southeast Asia. As such, the occurrence of five to seven tropical cyclones is expected in the Philippines. Likewise, near normal occurrence of tropical cyclones is also expected over the Bay of Bengal. Elsewhere, the occurrence of Squalls is favoured during this period.
Taking into consideration the national level forecasts, the present state of the climate, and the forecasts available from GPCs and other global centres, the forum agreed on the following consensus-based outlook for JJA 2018 for the Southeast Asia region.
For the upcoming Northern Hemisphere summer monsoon season (June-July-August), normal conditions are expected over most parts of the Southeast Asia. However, there is a slightly enhanced probability of wetter than normal conditions over coastal Myanmar and central Philippines. Below to near normal rainfall is expected over western and central Borneo, Singapore, and central Indonesia.
Above normal temperatures are expected over much of central and eastern Southeast Asia, including parts of Peninsular Malaysia, Singapore, northern Borneo, central and southern Philippines, and eastern Indonesia. Near normal temperature are expected elsewhere, including over Mainland Southeast Asia.
Refer to Annex A for reference on what is meant by “above, near, or below normal” in the outlook. For more information on the Northern Hemisphere summer monsoon outlook and further updates on the national scale, the relevant NMSs should be consulted (see Annex B).
Consensus Maps for JJA 2018
The following maps provide the probabilistic outlooks for JJA 2018 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
The Forum would like to convey its appreciation to the National Meteorological Services of the ASEAN Member States for sharing their national-level forecasts, the Global Producing Centres and other participating international climate modelling centres for their products and expertise made available for this Climate Outlook Forum.