Rain gains seen for barren South as fresh ‘low’ forms over Bay of Bengal

A brewing low-pressure area (marked ‘L’) may approach the north Andhra Pradesh coast by Saturday and gradually bring rain cover (in blue shade) into the dry South Peninsula by weekend. | Photo Credit: www.tropicaltidbits.com

A fresh low-pressure area brewing over the north Bay of Bengal could keep the monsoon firing across eastern and central India even as the season begins edging towards its withdrawal from North-West India.

The normal date for the onset of monsoon withdrawal is around September 17. Yet the latest in a series of lows spawned since August could produce the classic late-season paradox: less rain overall, but sharper and more concentrated spells wherever weather systems find a favourable track, a pattern unfolding against the backdrop of a strengthening El Niño risk from the east and equatorial Paciic.

An unlikely beneficiary could be the South Peninsula, which has borne the brunt of the season’s hostile large-scale circulation. El Niño-linked sinking air and persistent high pressure have suppressed rain across the region, leaving it with a 27 per cent seasonal deficit, highest among India’s four meteorological regions. East and North-East India follows with a 25 per cent deficit, while Central and North-West India remain in single-digit deficit.

India Meteorological Department (IMD) expects the emerging system to provide another injection of moisture into the monsoon circulation. A cyclonic circulation over the north Bay and adjoining Bangladesh on Wednesday is expected to descend to lower levels and consolidate into a low-pressure area by Thursday.

The system could then take an unusual south-westward track along the coast, crossing into land around the Odisha-north Andhra Pradesh coast by Saturday. If it retains strength and spreads inland, its influence could extend across the South Peninsula and into Madhya Pradesh. Further evolution could see it intensify near the Mumbai-Konkan sector before being deflected towards Uttar Pradesh and eventually the Himalayan foothills.

This trajectory could prove crucial for rainfall distribution. A ‘low’ over the Bay can continue to pump moisture into the subcontinent even as the broader monsoon circulation gradually weakens. El Niño may raise the odds of a weaker monsoon, but it does not switch rainfall off. Instead, rainfall tends to become more erratic, with longer dry spells broken by intense bursts when lows and troughs align favourably.

The immediate forecast reflects this uneven pattern. Heavy rain is expected over Tamil Nadu, Puducherry and Karaikal on Saturday; Kerala and Mahe through next three days; and Telangana on Friday and Saturday. Scattered to isolated rain is likely across much of the southern peninsula, including Coastal and North Interior Karnataka; Rayalaseema; South Interior Karnataka; and Coastal Andhra Pradesh.

Eastern India could see heavier action. The IMD has warned of isolated extremely heavy rain over Odisha on Thursday and very heavy rain on Friday, besides heavy spells over West Bengal; Jharkhand; and Bihar. The Andaman and Nicobar Islands; West Bengal hills; and Sikkim are also in line for heavy rain.

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