Ahead of this week’s official April forecast for the monsoon by the India Meteorology Department (IMD), the US-based International Research Institute for Climate and Society (IRI) has said there is hope for good rains in the first half of the four-month monsoon season beginning June. The rainfall intensity may taper off in the last two months of the season.

The IRI map shows that in the first two months of the monsoon season, there will be good rains in the southern peninsula and parts of central India. In August-September, apart from peninsular India, there will be good rains in Gujarat and parts of Rajasthan and in the plains of the eastern Himalayas.

There is only a distant possibility of the spoilsport El Nino (warming of the Pacific water above normal) emerging in the period in the Nino 3.4 region — the region in the Pacific which influences Indian monsoons. In fact, the IRI sees the presence of the opposite phenomena La Nina (cooling of the Pacific waters below normal). Historically, La Nina causes good rains.

But La Nina is on a weakening trend. According to IRI, the 85% to 75% probability of La Nina in April and May would come down to 60% to 50% in June, the first month of the monsoon season. In July, the probability estimate remains in the range of 50% to 40%. In September, the last month of the monsoon season, the probability of La Nina would come down to 35% to 30%. But the El Nino factor is seen low at 5% to 20% in the monsoon period, while neutral condition could range from 5% to a maximum 50%.

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