In line with recent predictions by private weather forecasters, India’s official weather forecasting agency too has said the monsoon is likely to be “above normal” and likely to be 106 per cent of the average of 89 cm.
Monsoon rains within 96 per cent and 104 per cent of this average are considered “normal” in the terminology of the India Meteorological Department (IMD).
“The monsoon will be fairly well distributed but southeast India will get slightly less rain,” IMD Director General, Laxman Rathore told a press conference in New Delhi on Tuesday.
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He also said some regions would see floods and that the chances of drought — defined as a deficit of 10 per cent or more — were only one per cent this year.
In any given year, the chances of such a drought are 16 per cent.
Several reasons underlie the IMD’s optimism. Most importantly, it hinges on a waning El Nino — a global, meteorological phenomenon that’s associated with a warming of the waters of Central Pacific and correlated with droughts in India — and the historical observation that 7 out of 10 years, in the last century, that followed an El Nino saw normal or above normal monsoon rains in India.
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The years 2014 and 2015 were among the strongest El Nino years in meteorological history and were blamed for the climatically rare event of successive drought years. Though Pacific temperatures haven’t cooled enough, “El Nino neutral conditions” are expected to set in between June and July.
Another meteorological phenomenon known as a positive Indian Ocean Dipole — where the western portions of the Indian Ocean are warmer than the east and thereby push rain-bearing clouds over India — is also likely to form during the middle of the monsoon season, according to the IMD.
Finally, a La Nina — or an anti-El Nino — and associated with heavy rains in India was expected to set in around September, too late for the Indian monsoon, but its onset is generally considered enabling for the rains.
The IMD relies on a statistical dataset of temperature and monsoon trends, down to districts and blocks, that goes back over a century to forecast the performance of the summer monsoon.
However, it is also developing a dynamical model — the preferred contemporary approach by meteorological agencies internationally — that relies on supercomputers. They work by simulating the weather at any given day and extrapolating the weather into the future. This model, a work in progress, also indicates that monsoon rainfall is likely to be a munificent 111%, give or take 5%, of the historical average of 89 cm.
Mr. Rathore was also optimistic that the last decade, which has seen several years of drought or near-drought conditions for instance in 2002, 2004, 2009, 2014 and 2015, and termed as a “low epoch” may be drawing to a close.
“There are good days ahead as we are at the end of the curve of depressed rain,” he told the press conference convened to announce the forecast.
Generally, India’s science minister announces the April monsoon forecast every year but didn’t do so this year as per a “change in convention effective this year,” according to a senior official in the Ministry of Earth Sciences, the IMD’s umbrella organisation.