Monsoon withdrawal from parts of northwest India has started: IMD

The withdrawal of the southwest monsoon has started from some parts of northwest India (western Rajasthan and Punjab) on September 28, the India Meteorological Department (IMD) has said.

The monsoon is expected to further withdraw from other parts of Rajasthan, Punjab and some parts of Haryana, Delhi, Chandigarh, Uttar Pradesh and Madhya Pradesh in the next two-three days.

This means that the withdrawal has been delayed by 28 days as the normal date for the start of withdrawal is September 1. However, the IMD changed its monsoon calendar this year and the new withdrawal date from northwest India is September 17. This means that the monsoon withdrawal from the region is late by 11 days. 

The monsoon’s withdrawal last year had started 40 days late, on October 10. But then, the rains vanished from the subcontinent in just six days. It remains to be seen if such a scenario will occur again this year.

The monsoon season will withdraw early from central India this year, Elena Surovyatkina, a climate scientist at the Potsdam Institute for Climate Impact Research in Potsdam, Germany and a principal researcher at Space Research Institute of Russian Academy of Sciences in Moscow, Russia, had told Down To Earth in a recent interview.

The southwest monsoon is likely to withdraw from the central part of India (20°N, 80°E) between October 3 and October 13, 2020, according to Surovyatkina. If her prediction is true, the monsoon will withdraw quickly this year as well.

“The conditions for monsoon withdrawal occur when the Indian subcontinent cools down to below 27°C,” Surovyatkina had said. Once the cooling takes place in a critical region such as central India, the rest of the eastern parts cool down quickly.

“The rate at which cooling happens does not change so much from year to year but the initial temperature in the northwest region where cooling starts, is changing considerably, around 4°C. When the initial temperature is higher, the process of withdrawal becomes longer,” she had added.

In 2019, the temperature in the northwest at the end of the August was very high; this is why monsoon withdrawal was delayed. Surovyatkina has observed the trend for delayed withdrawal of the monsoon starting from 2007.

The region from where the withdrawal will start is also the one with the greatest deficit in rainfall. The northwestern region of India has a deficit rainfall of 15 per cent in this monsoon season, according to IMD.

In fact, the northwestern region of the country has not received excess rainfall seven years in a row. The last time there was more than normal rainfall in the region was in 2013 (nine per cent).

This is when the rest of the country has received ample seasonal rainfall, with a country-wide excess of nine per cent as on September 27. While the southern peninsula has the highest excess rainfall of 30 per cent, central India has an excess of 16 per cent. East and north eastern India also has an excess rainfall of seven per cent.

The Union Territory of Ladakh has the highest rainfall deficit of 66 per cent in the northwestern region, followed by Jammu and Kashmir with a deficit of 33 per cent.

Among the states, Himachal Pradesh has received the least rainfall this season, with a deficit of 26 per cent, followed by Uttarakhand, which has received 20 per cent less rainfall than normal.

Other states like Uttar Pradesh, Punjab and Haryana also have deficit rainfall. The only state with more than normal rainfall in the region is Rajasthan, with a seven per cent excess.

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