Climate Outlook - Rainfall

Statement from the Southeastern Asia Regional Climate Outlook Forum
2 February, 1998, Bangkok, Thailand

SUMMARY

Below normal rainfall conditions will continue to prevail in most parts of the region during the period February through April 1998. Indications for below average rainfall are strongest in the Philipines, northeastern Kalimantan, the northern Sulawesi and the region around the Bay of Bengal, including Sri Lanka and around the South China Sea. Above average precipitation is expected only in western Sumatra and southeastern China. These conditions are consistent with precipitation patterns usually associated with the mature phase of a major El Niņo, such as occurred in previous events (e.g. 1982-83) and the current event (e.g. 1997-98).

THE CLIMATE OUTLOOK FORUM

A Regional Climate Outlook Forum convened in Bangkok on Feb. 2, 1998 to formulate consensus guidance for the February-April 1998 season in Southeastern Asia. The Bangkok Forum reviewed the state of the global climate system and its implications for Southeastern Asia. One of the principal factors taken into account is the major El Niņo event on-going in the tropical Pacific Ocean; anomalously warm sea surface temperatures over the Indian Ocean were also considered. Recent El Niņo occurrences such as in 1982-83, 1986-87 (although with somewhat different patterns), 1991-92 and 1994-95 resulted in below-average rainfall across much of Southeastern Asia and disrupted climate patterns around the globe.

METHODOLOGY

The regional climate assessment began with consensus agreement that the current El Niņo will remain over the forecast period (February-April 1998). This and other factors affecting Southeastern Asia's climate were assessed using coupled ocean-atmosphere models, physically-based statistical models and expert interpretation. The current status of seasonal to inter-annual forecasting allows prediction of spatial and temporal averages, and does not fully account for all factors that influence regional and national climate variability. This Outlook is relevant only to seasonal time scales and relatively large areas, and local variations will occur. Users are strongly advised to contact their National Meteorological Service for interpretation of this Outlook and for additional guidance.

OUTLOOK

February through April covers much of the dry season in most parts of the Asian tropical monsoon region, with April being the transitional month of the commencement of the summer monsoon. The region from the Philippines, northeastern Kalimantan, northern Sulawesi, most parts of Indochina, Thailand, Myanmar, Bangladesh and Sri Lanka are expected to continue to have below-average precipitation, except for southeastern China and the western part of Sumatra where there is an expectation of above average rainfall.

The precipitation outlook described above is consistent with conditions in Southeastern Asia and the Indonesian maritime continent usually associated with the mature phase of a major El Niņo episode.

PARTICIPANTS

Participants at the Forum included representatives of fifteen Meteorological Services (Australia, Bangladesh, Kingdom of Cambodia, China, Fiji, Indonesia, Republic of Korea, Lao PDR, Macau, Malaysia, Union Myanmar, Philippines, Sri Lanka, Thailand and Socialist Republic of Vietnam) and climate scientists and other experts from national, regional and international institutes (Asian Disaster Preparedness Center, International Research Institute for Climate Prediction, the University of Colorado, the US National Oceanic and Atmospheric Administration, and the US Agency for International Development.

MAP CAPTION

The numbers for each region indicate the probabilities of rainfall in each of the three categories, below-, near- and above-average. The top number indicates the probability of rainfall occurring in the above-average category, the middle number is for near-average and the bottom for below-average. In the case of the Philippines, for example, there is a 10% probability of rainfall occurring in the above-average category (i.e., within the range of the wettest third of recorded precipitation); a 20% chance in the near-average category; and a 70% chance in the below-average category. Boundaries between sub-regions should be considered as transition zones.