Summary of Outlook

The prevailing Southwest Monsoon conditions are expected continue into September 2020 and gradually transition to inter-monsoon conditions typically in the latter part of October. The Southwest Monsoon is normally associated with rainy weather over the northern ASEAN region and drier conditions over the southern ASEAN region. During the inter-monsoon period, the equatorial ASEAN region typically experiences an increase in shower activities. The prevailing winds over the ASEAN region during the Southwest Monsoon season usually blow from the southeast or southwest and gradually weaken as the inter-monsoon period sets in.

Above-normal rainfall is predicted over most parts of the southern ASEAN region as well as over the coastal regions of Cambodia, Myanmar, Thailand and Viet Nam. La Niña-like conditions are present over the tropical Pacific Ocean. Most climate models predict La Niña conditions from September 2020, which are typically associated with wetter-than-normal conditions over the Southeast Asia region.

During the September to November period, warmer than normal conditions are expected over the ASEAN region, except for some parts of Borneo where near-normal temperatures are expected.

While above-normal rainfall is predicted in the southern ASEAN region, occasional periods of dry weather could lead to an escalation of hotspot activities particularly in the fire-prone areas in Sumatra and Kalimantan. This could increase the risk of land and forest fires in the region and the of occurrence of transboundary haze in the southern ASEAN region cannot be ruled out. In the northern ASEAN region, the hotspot activities are expected to be largely subdued under the prevailing rainy conditions.

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