The South-West Monsoon seems to be finally on its way, after some initial hiccups.

The India Meteorological Department on Wednesday forecast that the system could reach the South Andaman Sea by May 28, a delay of about a week. (The system normally covers the region around May 20).

Senior IMD officials, however, stressed that this delay may not affect the onset over Kerala. “The system would be quite strong and it should advance fast and set in over Kerala around May 31. We stand by our forecast made about 10 days ago.”

[In a press release issued on May 13, the Department had forecast that the system was likely to set in over Kerala on May 31, with a model error of plus or minus four days].

The Department has also forecast that rainfall during the four-month season was “most likely” to be normal this year, at about 98 percent of the long period average, with a model error of plus or minus five per cent.

The IMD will update its assessment in June after taking into account parameters for which data would be available only by then.

The majority of international models monitoring El Nino-La Nina have indicated that sea surface temperatures over equatorial Pacific are warming up. Consequently La Nina conditions, which could, otherwise, have been beneficial for monsoon, have weakened.

As per recent forecasts by international models, for the period from June-August season, there was a very good chance for the neutral condition to continue: a probability of 57 per cent for the continuance of neutral condition, against a 22 per cent probability for the re-emergence of La Niña conditions and a 22% probability for the development of El Niño conditions.

But, long-term forecasts for El Nino-La Nina are fraught with large uncertainties. The El Nino-La Nina phenomena may unfold in a different way from the present forecast.

IMD officials emphasised that the Department would keep a close watch on the phenomena to ensure that the country was well prepared in case of any major changes. The IMD, they said, would also closely monitor the developments relating to Indian Ocean Dipole, which relates to anomalies in the sea surface temperatures between eastern and western parts of the Indian Ocean. At present, international models are forecasting that a negative IOD could develop and that it could happen in the last part of the monsoon. Consequently, as of now, there does not seem to be any possibility of a major impact.

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