“This year, the statistical model forecast suggests that the monsoon onset over Kerala is likely to be slightly delayed,” the IMD said. “The southwest monsoon onset is likely to set over Kerala on 6th June with a model error of plus or minus 4 days.”
“Conditions are becoming favourable for advance of southwest monsoon over the southern part of Andaman Sea, Nicobar Islands and adjoining southeast Bay of Bengal during May 18-19,” it added.
The normal onset date for monsoon over Kerala is June 1, which also marks the official commencement of the four-month rainfall season.
The IMD and private weather agency Skymet were unanimous on the prediction of the late arrival of monsoon this year. The Skymet had said on Tuesday that the monsoon would hit the Kerala coast on June 4, with an error margin of two days.
If the monsoon arrives late, it will be third such instance since 2014 when it arrived on June 5, followed by June 6 in 2015 and June 8 in 2016.
The delay in the arrival of monsoon may not necessarily have an impact on the overall rainfall. Last year, it had hit Kerala on May 29, three days before the normal onset date. Yet, the country received ‘below-normal’ rainfall.
Similarly, in 2017, the monsoon arrived in Kerala on May 30, but the overall rainfall was 95 per cent of the long period average (LPA), which falls under the below normal category.
In its initial forecast released in April, the IMD had predicted a near-normal rainfall with an LPA of 96 per cent, which falls on the border of ‘below-normal’ and ‘normal’ rainfall category. On the other hand, the Skymet has predicted a ‘below-normal’ rainfall with an LPA of 93 per cent.