In what is seen as the first official outlook for year 2018 monsoon, private forecaster Weather Risk Management Services (WRMS) has said that the June-September rainfall would be largely on the ‘positive side of normal’ (normal to above normal).
The forecast comes in the backdrop of a season that flattered to deceive in the just past year, recording only 95 per cent of the normal in contrast to early projections by the India Met Department of a likely surplus.
Weak La Nina
The monthly precipitation forecasts for this year are based on NOAA/CPC CFSV2 ensemble model products dated February 27, according to Sonu Agrawal, Managing Director, WRMS.
The WRMS processes the NOAA (National Oceanic and Atmospheric Administration of the US) CFSV2 model and adds statistical and synoptic interpretations to provide long-range weather forecasts.
Providing some background, Kanti Prasad, Senior Consultant, WRMS, said that outlook by US agencies (IRI/CPC) as on mid-February 2018 indicates that the tropical Pacific reflected a moderate to weak La Nina conditions.
The official CPC/IRI outlook calls for La Nina continuing through at least early spring, followed by a likely return to neutral conditions (neither La Nina nor alter ego El Nino) around mid-spring.
Pacific impact
A La Nina (cooling in the East Equatorial Pacific) has been mostly associated with a good monsoon, while an El Nino (warming event in the same waters) is known to generate dry conditions/drought here, without known cause-effect relationship.
The outlook also indicates that there is about 50 per cent chance of these conditions being ‘neutral’ during the South-West monsoon from June to September. This should, in normal case, leave the monsoon to itself.
Earlier, Busan, South Korea-based APEC Climate Centre had indicated enhanced probability for above normal precipitation during June to August for India.
‘Well-distributed’
The WRMS forecasts, put together by Kanti Prasad, indicate the year 2018 monsoon (June-September) to be on ‘the positive side of normal’ for the country as a whole ‘with well-distributed rainfall.’
June is expected to deliver excess rainfall over most parts of the country. July and September should end up within normal limits, while August may see subdued activity with West Coast, parts of Peninsular India and Rajasthan, likely falling under the negative side of normal, Agrawal said.
A detailed analysis shows that Rajasthan and parts of South-East Peninsula (mainly Tamil Nadu) might return deficit rain figures.