New Delhi: The El Nino weather phenomenon is gaining strength, latest global forecasts indicate, potentially affecting the South-west (June to September) monsoon in India. El Nino, characterised by a warming of surface temperatures in the Pacific Ocean, is associated with lower than normal monsoon rainfall in India.

According to the US National Oceanic and Atmospheric Administration, there is an 80% chance that El Nino will prevail in March-May, decreasing to 60% during the June-August period, when the South-West monsoon normally arrives.

El Nino affects the flow of moisture-bearing winds from the cooler oceans towards India, negatively impact the summer monsoon, which accounts for over 70% of annual rainfall. It remains to be seen how it would actually evolve over the next few months, but if it does retain its strength after the summer, it could mar the prospects of a good monsoon in India.

“We have to wait till April or May to ascertain El Nino’s impact on the monsoon," said D.S. Pai, senior scientist at the India Meteorological Department , Pune.

IMD forecast models suggest that weak El Nino conditions are likely to persist in the early part of the summer and weaken thereafter. “Once El Nino sets in, it continues for around 12-15 months and subsides in next pre-monsoon season. On some rare occasions, it may start late, gains strength and then decay before the monsoon onset. So, it could happen too," said Pai.

Contrary to last year’s global forecasts indicating that El Nino would form around October 2018, its formation was confirmed in February this year.

“During the next several months, El Nino can keep evolving and gain strength. Generally, it achieves its peak in winter. But how and when it will intensify, we cannot say. We will have to keep close eye on the forecast for next two months," said R Krishnan, senior scientist at Indian Institute of Tropical Meteorology (IITM), Pune.

Even though it is weak at present, forecasters said El Nino has become more marked than last month. An El Niño of any strength can reduce the amount of monsoon rainfall and thus have significant local impact.

There is increase in both the sea surface temperatures and subsurface ocean temperatures, allowing weak El Nino to persist for at least next several months. Nevertheless, India is set to witness warmer than normal temperatures due to El Nino, which would be evident during the next three months.

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