Agri Business

Deep depression weakens, but heavy rain to continue

Vinson Kurian Thiruvananthapuram | Updated on September 14, 2021

Australian Met Bureau puts up a ‘La Nina watch’

The rain-driving deep depression over North Interior Odisha has weakened into a depression that lay centred over North Chhattisgarh and adjoining North Interior Odisha about 80 km West-North-West of Jharsiguda and about 120 km South-South-East of Ambikapur this (Tuesday) morning.

Heavy to very heavy rainfall was reported from Saurashtra and Kutch while it was heavy over Odisha, East Gujarat, Madhya Maharashtra and Uttarakhand. The exceptionally heavy rain amounts reported overnight from Odisha, Saurashtra and Kutch and flooding for a second day tell a story.

Odisha, Saurashtra battered

Some of the highest rainfall amounts (20 cm and above) received during the 24 hours ending on Tuesday morning are as follows: In Saurashtra and Kutch: Lodhika 52; Visavadar-47; Kalavad-41; Dhoraji-25; Targhadia-24; Junagadh-21; Kotdasangani-21; Rajkot-20; Junagarh-20 and Keshod-20. These also go to prove the sustained rain-generating capacity of a conventional monsoon ‘low’.

Odisha: Talcher-39; Birmaharajpur-37; Tikarpara-35; Sonepur-28; Boudhgarh-26; Patnagarh and Banarpal-25; Bolangir, Hindol and Paikmal-24; Kantamal and Parjang-23; Barmul, Belpada, Bari, Jenapur, Phiringia, Gaisilet, and Mahanga-21; Angul, Nawapara, Kamakhyanagar, Tarva and Athmalik-20.

Even more rain to come

The depression will continue to move across North Chhattisgarh and Madhya Pradesh and weaken into a well-marked low-pressure area during the next two days even as it pours down. Contrary to forecasts, the other ‘low’ over East Gujarat has not weakened, and could sustain the flooding rain.

Meanwhile, India Meteorological Department (IMD) has predicted that a cyclonic circulation may develop over the North Bay of Bengal by Friday and move towards the Odisha-West Bengal coast during the subsequent two days, bringing a fresh spell of rain over the eastern parts of the country.

La Nina watch, back again

This came about on a day when the Australian Bureau of Meteorology has switched back its ENSO (El Nino-Southern Oscillation) status to ‘La Nina Watch.’ Though tropical Pacific is currently neutral (neither El Nino or La Nina), model predictions indicate a return of La Nina, the Bureau said.

Strengthening model outlooks and recent cooling in the tropical Pacific has raised these odds, it added. Consequently, the Bureau has lifted its ENSO Outlook status to ‘La Nina watch,’ meaning around a 50 per cent chance of La Nina forming. This is approximately double the normal likelihood.

Negative IOD weakening

The rain-repulsing negative Indian Ocean Dipole (IOD) too has weakened, with IOD values at marginal negative IOD levels. Models suggest this weak negative IOD pattern could persist at borderline levels through October before easing further. Recent stalling of the Madden–Julian Oscillation (MJO) over the East Indian Ocean may have compromised the negative IOD pattern, weakening it.

This is what is now translating into formation of helpful rain-driving circulations in the Bay of Bengal and an unusual revival of the monsoon in the last month of September when it normally prepares to exit the country, starting from the North-West outpost over West Rajasthan.

Cold, harsh winter likely

La Nina has come to be associated with very cold and harsh winters for India and above normal monsoon rain, though late in the season this year. La Nina conditions had prevailed from August-September 2020 to April 2021, which saw an above normal monsoon and an early and harsh winter.

While La Nina enhances the South-West monsoon, it has a negative impact on rainfall associated with the North-East monsoon because low-pressure areas or cyclones tend to form significantly to the North in the Bay during this phase and, contrary to their usually inward track, they re-curve and move away.

Published on September 14, 2021

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