The India Meteorological Department (IMD) has said that the onset of the 2020 South-West monsoon may be delayed slightly this year, and may occur on June 5 with a model error of +/-four days. The normal date of onset over Kerala along the South-West coast is June 1.

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Skymet sees monsoon arriving over Kerala by May 28
While The Weather Company predicts that the monsoon will arrive over the mainland by May 31
 

This is at variance with the outlook of private forecasters Skymet Weather and The Weather Company, an IBM Business. Earlier today (Friday), Skymet said it expects the monsoon to reach Kerala coast early by four days on May 28 while, The Weather Company had said as early as in April, that the date could be closer to June 1, May 31 to be precise.

Cyclone watch, Andamans onset

Giving a background, the IMD said that the monsoon arrives first over the South Andaman Sea, and will then advance in a North-West direction across the Bay of Bengal. As per the the new normal dates of monsoon onset/progress, it advances over the Andaman Sea around May 22.

A persisting well-marked low-pressure area over the South-East Bay may concentrate into a depression during next 12 hours and further intensify into a cyclone over the central parts of the South Bay by tomorrow (Saturday) evening.

Associated with this event, conditions are likely to become favourable for advance of the monsoon into the Andaman Sea, the Andaman & Nicobar Islands and some parts of the South-East Bay of Bengal, during next two days.

Past data suggest that there is no association of the onset over the Andaman Sea either with the date of monsoon onset over Kerala or with the seasonal monsoon rainfall over the country.

The IMD uses an indigenously developed state-of-the-art statistical model with a model error of +/- four days for calculating the onset date.

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