The Indian rainy season officially began when the southwest (summer) monsoon reached the coast of Kerala. Similar to the years 2016 and 2019 in the previous decade when the monsoon arrived as late as June 8, the beginning is seven days later than the typical date of June 1.
However, the quantity, distribution, and speed of the delayed monsoon's advance over the remaining regions of the country are unrelated to rainfall during the June to September season.
Announcing the onset of southwest monsoon over Kerala, the India Meteorological Department (IMD) said conditions were favourable for further advance of the rain-bearing system into the remaining parts of Kerala, some more parts of Tamil Nadu, some parts of Karnataka and parts of the northeastern states during the next 48 hours.
“The formation of a low pressure system in the Arabian Sea, which subsequently intensified into the very severe cyclone ‘Biparjoy’, delayed the onset of the monsoon over Kerala as it took moisture away from the region,” IMD chief Mrutyunjay Mohapatra said.
Following the fulfilment of all requirements, including the depth of westerly winds across the southeast Arabian Sea, the Met department declared the beginning of the monsoon. The IMD had on May 16 predicted the onset of monsoon over Kerala on June 4 with a model error of ± 4 days. So, the arrival this year is within the forecast range. Summer monsoon normally sets in over Kerala on June 1 with a standard deviation of about seven days even as it arrives over Andaman & Nicobar Islands around two weeks early.