The onset of monsoon over Kerala is likely to be delayed by six days beyond its scheduled date of June 1, the India Meteorological Department (IMD) said in its latest forecast on Sunday. While this is expected to delay monsoon in other parts of the country, overall monsoon will be above normal.
“The south-west monsoon is likely to set over Kerala on June 7 with a model error of plus or minus four days,” the IMD said.
The forecast of monsoon onset issued during the past 11 years (from 2005-2015) by the IMD (except 2015) has proved to be correct with an error margin of plus or minus four days. The country’s private forecaster Skymet Weather Services has, however, forecast that the south-west monsoon is likely to arrive a little earlier than usual over Kerala, between May 28 and May 30.
According to IMD Director General, laxman Singh Rathore, the delay in the onset of monsoon is not an “unusual” phenomenon.
He, however, predicted some imminent rainfall in the southern States, bringing relief from the sweltering heat.
“The low pressure area building up in the Bay of Bengal will become a depression and hit Tamil Nadu coast by tonight. This will bring good amount of rainfall to the State, parts of South Interior Karnataka and parts of Kerala,” said Rathore.
After two consecutive years of below normal monsoon, the IMD in April predicted above average normal of 106 per cent of the long-period average. There is a 94 per cent probability that monsoon will be normal to excess.
Rathore said that despite delay in onset the monsoon will be above normal.
According to the weather scientists, monsoon is deemed to have set in only if the IMD finds that 60 per cent of the 14 enlisted weather stations in Kerala and Karnataka report rainfall of 2.5 mm or more for two consecutive days after May 10. Other criteria for declaring monsoon onset includes minimum temperature over northwest India and pre-monsoon rainfall peak over the southern peninsula.
There is, however, no established link between the date of the onset of the monsoon and the intensity of rainfall in the country.
The met department has further stated that the conditions are becoming favourable for the onset of southwest monsoon over Nicobar Islands, south Andaman Sea and parts of south Bay of Bengal around May 17 and advancement over the entire Andaman Sea close to its normal date.
It is also set to advance over the Andaman Sea around May 20 with a standard deviation of about one week. The weather experts pointed to the strong convective activity over the equatorial Indian Ocean for the last several days. A well marked low pressure area has formed over the Indian Ocean which will concentrate into a depression and move north-westwards, said the sources.