Rain spells havoc in hill states, west coast

Meteorologists said development of several weather systems one after the other with hardly any gap, and their interaction with each other has led to severe rainfall in certain parts of the country

New Delhi: Mudslides, landslides, damage to highways and bridges in Himachal Pradesh and Uttarakhand; floating cars and cattle being washed away in Gujarat’s Junagadh; a massive landslide that washed away an entire village in Maharashtra’s Raigad — across India, the monsoon has been unusually active in July, with no sign of letting up.

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Meteorologists said that the development of several weather systems one after the other with hardly any gap, and their interaction with each other has led to severe rainfall in certain parts of the country, particularly India’s north including Himachal Pradesh and Uttarakhand and the west coast, from Konkan to Gujarat.

The numbers speak for themselves.

There is 5% excess rain over the country to date (from June 1) with 40% excess over northwest India; 23% deficiency over east and northeast India; 10% deficiency over peninsular India and 15% excess over central India according to the India Meteorological Department (IMD).

Compare that with the situation up to June 30, when the deficiency was 10%.

Two low-pressure areas that developed last week have already brought widespread rain to central India and parts of west India.

Now, another low-pressure area is expected to develop over west central and adjoining northwest Bay of Bengal which will intensify further and travel northwestwards. Three to four western disturbances have also impacted the Western Himalayan region bringing unusually high rainfall to northern states.

”Normally once a low-pressure area forms over Bay of Bengal, there is a gap of a week or more before another low-pressure area develops but we can this July it’s quite unusual that low- pressure areas are forming without gap one after the other. There is also a cyclonic circulation over northeast Arabian Sea and adjoining Gujarat. The two systems are interacting and bringing usually heavy rain over the west coast. Feeble western disturbances are also impacting the Western Himalayas bringing rainfall through the month to Uttarakhand and Himachal Pradesh,” said Mahesh Palawat, vice president, climate change and meteorology at Skymet Weather.

But the rain has not been uniform.

The eastern paddy growing states in the Indo-Gangetic Plains are in deficient rain category while those in northwest and west India have excess to large excess rainfall so far. Gangetic West Bengal has a 38% rain deficiency; Jharkhand 44%; Bihar, 43% and east Uttar Pradesh has 29% rain deficiency since June 1. But Himachal Pradesh has 78% excess rain, West Rajasthan 144% excess; Saurashtra and Kutch, 165% .

“July is the main monsoon month. Normally around 13 low pressure areas can form during the four monsoon months. So, the formation of at least three low pressure areas in July is normal,” said M Mohapatra, director general, IMD.

The new low-pressure area could become a depression and cross the Odisha coast , thereafter moving to east central India, bringing rains to a region that is still deficient, he added.

“The monsoon trough is south of its normal position. It is passing from South Odisha to Gujarat and it is also embedded with cyclonic circulations. Active monsoon conditions along with supportive weather systems is bringing a lot of rainfall, very high in quantum, to the west coast now particularly Gujarat, Konkan and Maharashtra. An interaction between a western disturbance and the monsoon trough caused extensive flooding over north India between July 8 and 13. In the past three days another western disturbance was affecting the western Himalayan region which was causing continuous rainfall in parts of Uttarakhand and Himachal Pradesh. Another western disturbance is approaching so we expect rainfall to continue,” Mohapatra added.

The LPA of rainfall over the country during July is 28cm based on the data of 1971 to 2020 and the LPA for the entire monsoon season is 88cm.

At the national level, July rain so far to date is 23.8cm.

A lot of the rain is coming from heavy and very heavy rain, though.

“Heavy rains are contributing more to the seasonal total. Due to global warming that contribution percentage is increasing. This could be a new normal. We need to improve our warning systems, ... and (create) infrastructure which is resilient to climate change,” said M Rajeevan, former secretary, ministry of earth sciences.

According to Indian authorities, heavy rain ranges from 6.45cm to 11.5cm; very heavy rain ranges from 11.5cm to 20.4cm; extreme heavy rain is more than 20.4cm rainfall in a day.

That is only to be expected. Widespread extreme rain events across central India have tripled since 1950, according to a paper led by climate scientist Roxy Mathew Koll and his team at the Indian Institute of Tropical Meteorology (IITM), and published in Nature Communications in 2017.

And northwest India, which has already received a lot of rainfall in July (20.38cm compared to LPA of 14.95cm), could receive more. “Around July 26 and 27 we can expect widespread rainfall over northwest India. The Bay of Bengal is warm leading to formation of low-pressure systems,” Skymet’s Palawat added. Therefore, the government must invest in early warning systems and more sensitive forecasting apparatus, as well as tweak policies to adjust to the new normal of the climate crisis.

This year, an El Nino effect — warmer waters around the equatorial pacific that adversely affect the monsoon — was expected to emerge, but its impact is “not pronounced yet,” said Palawat.