The southwest monsoon has ended and the northeast monsoon is likely to set in “in the next 72 hours”, the India Meteorological Department (IMD) said on October 19.
The onset of northeast monsoon, also known as the ‘retreating monsoon’, would likely be “weak”, the agency added.
The southwest monsoon began its withdrawal from Rajasthan on September 25, nearly a week behind its normal date of September 17.
Though monsoon withdrawal begins from Rajasthan, it takes nearly until early to mid-October for it to fully withdraw and be replaced by the northeast monsoon. However, India officially only counts rainfall received from June 1 to September 30 as monsoon rainfall.
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September rain brings relief
As of September 30, India received 94% of the expected rain from the four monsoon months. This is below the forecast of 96%, but still within the error margin of the IMD’s forecast models. Rainfall that reaches 96% to 104% of the long-term average is considered ‘normal’. An ongoing El Nino, a warming of the surface waters of the central and eastern equatorial Pacific, triggered a dry August but this was partially compensated by a more-than-expected rain in September.
Earlier this month, the IMD forecast a ‘normal’ northeast monsoon from October to December, and ‘normal to above-normal rainfall’ over large parts of north-west India and the southern peninsula. Tamil Nadu, Kerala, Karnataka and parts of Andhra Pradesh receive significant rainfall from the northeast monsoon, though overall it contributes only around 11% of India’s annual rainfall.
Previous experience, however, suggests that there is extreme year-on-year variability. In 2015, Chennai was deluged by rain, whereas a weak northeast monsoon inflicted a severe water shortage in 2019.
The IMD has also reported two developing low pressure areas — precursors to cyclones — both in the Arabian Sea as well as in the Bay of Bengal that are likely to become ‘depressions’ by October 21. It is yet unclear if they will morph into something bigger.
