IMD has predicted the southwest monsoon’s onset over Kerala's coast will be delayed by six days, while private weather forecasting agency Skymet said this would start from June 1, its normal time. IMD’s forecast is with an error of plus or minus four days.
“The rains in north and central India are mostly due to western disturbances but in the south, yes, we can say some pre-monsoon showers have happened,” said D S Pai, deputy director general at IMD.
He said there was no chance of any advancement of the onset date and it had been delayed by at least a week. “There has been no forward flow in the Arabian Sea and it will take another week before the rains formally settle in,” Pai said.
However, Mahesh Palawat, chief meteorologist at Skymet, said the rain in north and central India was due to a combination of cyclonic circulation over neighbouring Pakistan and also pre-monsoon activity.
“The cyclonic circulation over Pakistan formed a rainfall trough which passed through Punjab, Haryana, Uttar Pradesh, Bihar, Jharkhand and right upto Gangetic West Bengal, which caused the rains, including in the foothills of the Himalayas,” he said.
The intensity of these showers would go down in the next few days. On the onset of the southwest monsoon over Kerala, Palawat said 60 per cent of the 14 measuring stations there had recorded 2.5 mm or more rain for consecutive days, one of the main parameters for declaration of the onset.
However, the other two criteria, of westerly winds between 15-20 nautical miles and cloud patterns, have not been fulfilled. “IMD declares a monsoon onset when all the three criteria are met, of which the first one has been," Palawat said.