The India Meteorological Department (IMD) formally announced the onset of the Southwest Monsoon over some areas of the South Bay of Bengal, South Andaman Sea, Nicobar Islands, and parts of the North Andaman Sea, which is one of the earliest in the last seven years.
The average date for the onset of the monsoon in this area is May 21, but this year it started on May 13, at least a week early. The premature onset follows two days of extensive moderate to heavy rainfall over the Nicobar Islands, one of the primary parameters for the IMD to announce the onset of the monsoon.
“Conditions remain favourable for further advance of the Southwest Monsoon into the South Arabian Sea, Maldives, and Comorin region; additional parts of the South Bay of Bengal; the entire Andaman and Nicobar Islands; remaining parts of the Andaman Sea; and the central Bay of Bengal over the next three to four days,” the IMD added.
Favourable Conditions Behind Early Onset
Mrutyunjay Mohapatra, Director General of the Indian Meteorological Department, mentioned several factors responsible for this premature onset, such as:
Above-average minimum temperatures over North India,
A strengthening of the westerlies and easterlies at several atmospheric levels,
Frequent pre-monsoon rainfall over southern India for more than 40 days,
High-pressure anomalies over the northwest Pacific Ocean.
“All these indicators point to an early monsoon onset over Kerala as well,” Mohapatra added. Model forecasts indicated that the monsoon will arrive in Kerala on May 27, almost five days ahead of the normal June 1 onset.
Above-Normal Rainfall Expected This Year
In this year, monsoon precipitation is predicted to be higher than normal, as expected precipitation should be 105% of the Long Period Average (LPA) of 880 mm during the season June–September. The Indian Southwest Monsoon is the principal rainy season, which provides over 70% of the rainfall for the whole country annually.