New Delhi: The India Meteorological Department (IMD) on Tuesday officially announced the onset of the Southwest Monsoon over parts of the Bay of Bengal and the Andaman Sea, marking the earliest onset over the region in the past seven years.
According to the IMD, the monsoon has advanced into some areas of the South Bay of Bengal, South Andaman Sea, the Nicobar Islands, and parts of the North Andaman Sea as of May 13. The department noted that conditions remain favourable for further advancement over the next three to four days.
The IMD stated that the Southwest Monsoon is likely to advance into additional regions, including parts of the South Arabian Sea, the Maldives and Comorin areas, more parts of the South Bay of Bengal, the entire Andaman and Nicobar Islands, the remaining areas of the Andaman Sea, and sections of the Central Bay of Bengal in the coming days.
Director General of IMD, Mrutyunjay Mohapatra, told The Indian Express that multiple meteorological factors support this early monsoon arrival. These include persistently higher-than-normal minimum temperatures in North India, the strengthening of both westerly winds in the lower atmospheric levels and easterly winds in the upper levels, and the unusually early and prolonged pre-monsoon rainfall and thunderstorms over the southern peninsula for about 40 days. He also highlighted prevailing higher-than-average pressure over the northwest Pacific Ocean as a contributing factor.
“These conditions indicate a clear strengthening of monsoon winds,” Mohapatra explained. “Our Indian weather models, along with several global models, all suggest a heightened rainfall activity over Kerala before June 1, which is the normal onset date. All indicators point to an early onset of the monsoon over Kerala, likely around May 27—about five days ahead of the usual schedule.”
The normal onset date for the monsoon over the South Andaman Sea is May 19, while for Port Blair in the Andaman and Nicobar Islands, it is May 21. The announcement on Tuesday marks a significant deviation from this timeline, highlighting the earliest onset in the region since 2017.
Over the past two days, the Nicobar Islands have experienced widespread moderate to heavy rainfall, fulfilling one of the key meteorological criteria for declaring the arrival of the monsoon. The rainfall patterns observed since Monday have further confirmed the sustained presence of the monsoon system.
The Southwest Monsoon is the principal rainy season for India, accounting for more than 70 per cent of the country’s annual rainfall. Typically, the monsoon makes landfall over the Andaman Sea and Bay of Bengal by the third week of May before gradually advancing across the subcontinent. IMD formally declares the monsoon's onset over India when it reaches Kerala, with the usual date being June 1. The monsoon generally covers the entire country by around July 15.
This year, the monsoon rainfall is expected to be ‘above normal’, with quantitative forecasts estimating 105 per cent of the Long Period Average of 880 mm, according to the IMD.