Normal to above normal rainfall forecast for southwest monsoon season

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Normal to above normal rainfall is most likely during the 2021 southwest monsoon season (June – September) over most parts of South Asia, according to an authoritative seasonal forecast from the South Asian Climate Outlook Forum (SASCOF) released this week.

Geographically, above-normal rainfall is most likely over some areas of the North West, along the foothills of Himalayas and North East parts of the region, and many areas of central part of the region. It is most likely to be below normal over many areas over extreme northwest, north East and some areas over north-eastern parts of the region. Elsewhere it is most likely to be normal.

From June through September, the Southwest Monsoon dominates life in much of South Asia. Accounting for 75-90 per cent of the annual rainfall in most parts of the region (excepting Sri Lanka and southeastern India), the monsoon has an all-pervading influence on the socio-economic fabric of the region and thus of the national economies of South Asian countries.

During the season, maximum temperatures are likely to be below normal over most of the central parts of South Asia, and above normal over northwest and northern areas of northeast of the region. Minimum overnight temperatures are likely to be above normal over most areas of west, northwest, north and north eastern parts of the South Asia, and below normal over east-central and south western areas of the region. Elsewhere, they are likely to be normal.

Advance information about the likely performance of the monsoon underpins planning and decision-making in climate-sensitive sectors such as agriculture and informs public health and risk-management strategies.  

According to the World Meteorological Organization (WMO), the moderate La Niña has weakened in April to borderline La Niña, and ENSO neutral conditions are likely to prevail during the southwest monsoon season. ENSO neutral conditions are generally associated with normal southwest monsoon over the region, although other factors such as Indian Ocean conditions may also play a big role.

The snow-cover over Northern Hemisphere as well as Eurasia was below normal in the past few months. Winter and spring snow cover extent has a general inverse relationship with the subsequent Asian summer monsoon rainfall.

The 2021 seasonal forecast follows a year in which heavy monsoon rains brought not only socio-economic benefits but also death and upheaval. In 2020, India had one of its two wettest monsoon seasons since 1994, with nationally-averaged rainfall for June to September 9% above the long-term average.

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