IMD forecasts the system is likely to set in over Kerala, its entry into the Indian mainland, on June 3, against the normal date of onset on June 1

The mush-awaited southwest monsoon is on its way. But it could be slightly delayed.

The India Meteorological Department on Wednesday forecast that the system is likely to set in over Kerala, its entry into the Indian mainland, on June 3 with a model error of plus or minus four days. The normal date for onset over Kerala is June 1.

The delay is expected because of the cyclonic storm, Mahasen, which is presently located over the central Bay of Bengal and is likely to cross the coast near Chittagong in Bangladesh on Thursday night.

Speaking to The Hindu, a senior IMD official noted that the monsoon current, which is quite strong now, will weaken once the cyclone crosses the coast. It would have to re-organise again and that could take some time. “We are hopeful that the system would reorganise quickly and bring the first spell of monsoon rains over Kerala around June 3.”

The IMD has been issuing forecasts for the onset over since 2005 and it has been almost on the mark: the predictions have been coming true, at least within the model error range of plus or minus four days.

Last year, IMD had predicted an onset on June 1, and the actual event occurred four days later on June 5. In 2011, its prediction was for May 31 and the onset took place two days earlier on May 29.

The dates forecasted by the department and the actual date of onset for the earlier years are as follows: 2010: forecast May 30 [actual May 31], 2009: May 26 [May 23], 2008: May 29 [May 31], 2007: May 24 [May28], 2006: May 30 [May 26] and 2005: June 10 [June 7].

The IMD, in its long range forecast for the season issued on April 26, has predicted that it would be a normal monsoon this year, with a rainfall of 98 per cent of the long period average of 89 cm with a model error of plus or minus 5 per cent.

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