South Asian Climate Forum sees normal monsoon this year

The 16th session of the South Asian Climate Outlook Forum (Sascof) that met through video-conferencing has said in its South-West monsoon outlook (June-September) for this year (2020) that rainfall for the season as a whole is most likely to be normal over the region.

Above-normal rainfall is most likely over the South ― mainly the islands of Maldives, Sri Lanka, Lakshadweep, Andaman & Nicobar and parts of southern and coastal parts of Kerala and Tamil Nadu and some areas of the North-West (most of South and Central Pakistan). Across the international border, the rainfall would be normal over Rajasthan and Gujarat in India.

Fewer weak rainfall areas

But the seasonal rainfall over land around the North Bay of Bengal (Coastal Odisha, adjoining Coastal Bengal and Bangladesh) and some areas in the extreme North of the region is most likely to be below normal. The seasonal rainfall is most likely to be normal over the remaining areas.

There is a strong consensus among experts about the weakening of the prevailing warm-neutral conditions in the Equatorial Pacific leading to neutral conditions, which are likely to continue during the monsoon season. Though a few global models are suggesting slight possibility of the development of monsoon-supporting weak La Nina conditions in the latter part of the season or thereafter, there is uncertainty in its development. This is due to the well-known fact that predictions about the Pacific at this time of the year generally have substantial uncertainty due to the so-called spring barrier in seasonal predictability.

Indian Ocean Dipole outlook

In general, Sascof expected that the monsoon may likely see neutral conditions in the Pacific. But this is not the only factor that determines its performance. Other relevant climate drivers such as the state of the Indian Ocean Dipole (IOD), tropical Atlantic sea surface temperatures, and Eurasian land heating are also important. The relative impact of all these parameters needs to be considered to determine the expected state of the monsoon which are implicitly considered by the dynamical climate models that underpin the present outlook.

At present, basin-wide warming is observed in the Indian Ocean, with strongest warming in the South Indian Ocean and neutral IOD conditions. A positive (negative) IOD is associated with a stronger (weaker) than normal monsoon. The recent forecasts from coupled global models suggest that these neutral IOD conditions are likely to continue during the monsoon season. However, a few climate models indicate development of weak negative IOD conditions in the latter part of the monsoon season.

Leading agencies take part

National meteorological and hydrological services of nine South Asian countries as well as those representing several global and regional climate agencies, including World Meteorological Organisation (WMO); the WMO Regional Climate Centre, Pune; Indian Institute of Tropical Meteorology, Pune; the UK Met Office (UKMO); International Research Institute for Climate and Society, Columbia University, US; the Regional Integrated Multi-hazard Early-warning System, Bangkok; and the Japan Meteorological Agency, attended the session.

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