NEW DELHI: It is now official. The India Meteorology Department on Monday gave its stamp of approval for the assessment of the National Centre for Medium Range Weather Forecasting that the South-West monsoon was on track and was likely to set over Kerala around the normal date of June 1.

In a press release, the IMD announced that as per its analysis the system could set over Kerala on May 30, with a margin of error of plus or minus three days. The analysis was based on a statistical model that took into account six parameters.

This is the second consecutive year, when the IMD has come out with a long range forecast for the onset of the monsoon.

Last year, it had forecast that the monsoon could arrive over Kerala around June 7 and the monsoon broke over the state on June 5.

The six parameters that are considered are: pre-monsoon rainfall peak over the south peninsula, sea surface temperature over the south Indian Ocean, the wind pattern in the lower troposphere over the south Indian Ocean, north-west India's minimum temperature and out-going long wave radiation anomalies over Indo-China and south-west Pacific regions.

The model has a forecast error of plus or minus three per cent.

"There is no one to one correspondence between monsoon onset date over Kerala and subsequent monsoon rainfall during the season (June to September) over the country as a whole," it said.

On the El Nino phenomenon, the release said there did not seem to be much of a possibility for the problem to arise.

"A majority of statistical and coupled model forecasts (from across the world) indicated that there was a higher probability of around 65 per cent for near neutral conditions to continue over the equatorial Pacific during the season."

The El Nino problem can arise when the sea surface temperature in the equatorial Pacific region rose beyond the normal by 0.5 degrees Celsius and above.

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