October Extremely Heavy Rainfall Events’ Frequency Surpasses Last Five Years

New Delhi: Northwest India received 67 mm rainfall in the month of October against the normal of 23 mm, a massive 191.2 per cent departure against long period average (LPA), including 160 instances of very heavy rainfall and 36 of extremely heavy rainfall.

Comparing the last five years, the frequency of extremely heavy rainfall has been maximum in 2021 for September and October, India Meteorological Department (IMD) data showed.

It was on October 17 that Kerala saw rainfall in excess of 200 mm; October 18 and 19 saw Uttarakhand receive rainfall in excess of 200, 300 400 and even 500 mm rainfall whereas on October 20, it was sub-Himalayan West Bengal and Sikkim that saw extreme rainfall events.

Country as a whole received 100.7 mm rainfall against 76 mm normal, a departure of 32.5 per cent from LPA from October 1 onwards.

While Kerala, Tamil Nadu, parts of Andhra Pradesh and parts of Karnataka receive rainfall at this time of the year due to Northeast monsoon, for much of the other parts of India, especially northwest India, it was a combination of western disturbances and low-pressure areas.

“There were higher than normal numbers of low-pressure systems during the period — nine low-pressure systems, including two cyclones, one deep depression and six lows affected the country during the period. Even the monsoon withdrawal commenced late and ended late,” IMD Director General, Mrutyunjay Mahapatra said.

Monthly rainfall for November 2021 over the south peninsular India consisting of five meteorological sub-divisions (Tamil Nadu, Puducherry and Karaikal, Coastal Andhra Pradesh and Yanam, Rayalaseema, Kerala and Mahe and south interior Karnataka) is most likely to be above normal (>122 per cent of LPA), he added.

Currently La Nina conditions are prevailing over the Equatorial Pacific Ocean and neutral Indian Ocean Dipole (IOD) conditions are prevailing over the Indian Ocean. The latest global model forecasts indicate that the La Nina conditions are likely to prevail until March 2022 and neutral IOD conditions are likely to continue during the upcoming seasons.

“As the changes in the Sea Surface Temperature (SST) conditions over the Pacific and the Indian Oceans are known to influence the Indian climate, IMD is carefully monitoring the evolution of sea surface conditions over these ocean basins,” the IMD Head said.