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 on 27 April.
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.
SASCOF was launched in 2010 under the auspices of WMO to engage South Asian countries that share a strong and common interest in understanding and forecasting the monsoon. It is one of a worldwide network of Regional Climate Outlook Forums supported by WMO and its partners to promote collaboration and information sharing on seasonal climate prediction and related issues.
The regional climate outlook for the 2021 southwest monsoon season was developed at the virtual 19th SASCOF session from 26 to 28 April through collaborative efforts of the RCC Pune, all nine National Meteorological and Hydrological Services (NMHSs) of South Asia, with the support from international experts, including from the UK Met Office and the Regional Integrated Multi-Hazard Early Warning System for Africa and Asia (RIMES). It was based on an expert assessment of the prevailing global climate conditions and objective seasonal forecast techniques using data from different climate models from around the world.
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. Heavy rain, flooding and landslides also affected surrounding countries. August was the wettest month on record for Pakistan, according to the WMO’s State of the Global Climate 2020 report released on 19 April.