The building Bay of Bengal cyclone (in purple and red circle to right) and the Arabian Sea ‘low’ (orange shade to left) feeding each other by Monday, as projected by the ECMWF. | Photo Credit: www.meteologix.com/in

The Bay of Bengal is brewing a potentially powerful cyclone, with the India Meteorological Department (IMD) hinting at its formation by Monday as a parent low-pressure area lay in wait over east-central and adjoining south-east Bay of Bengal on Friday.

The ‘low’ was located farthest from Chennai on Friday noon at 950 km to north-east; 703 km south of Kolkata; 631 km east-south-east of Visakhapatnam; and closest to Brahmapur (Odisha) at 557 km to south-east. Global models tracking the development have given the storm an initial moniker, 98B. It will be declared a numbered cyclone before being called by a name (Arnab, as per naming protocol, and contributed by Bangladesh).

Friday’s ‘low’ is expected to move west-north-westwards, intensify into a deep depression by Sunday, and become a cyclonic storm over the west-central Bay by Monday morning. It is then forecast to strengthen further and head towards the north Andhra Pradesh and adjoining south Odisha coasts over the next two days. Global models suggest it could reach at least severe cyclonic storm intensity.

The IMD has declared a fishermen warning along and off Karnataka and Kerala coasts; Lakshadweep, Comorin and adjoining Maldives for next four days. To the Bay side also, the warning applies to Gulf of Mannar and Sri Lanka coast as well as the Andaman Sea as many days. It extends variously to other parts of the outer Bay.

The prevailing Madden-Julian Oscillation (MJO) wave may become strong from Saturday, and favour better convective activity and cyclogenesis over both the Bay and the Arabian Sea during next two weeks. In this context, the IMD signalled possibility of the next ‘low’ popping up over the south-east Bay in another week’s time. It could further boost rain prospects for Tamil Nadu, Puducherry and Karaikal which has already recovered impressively from a distressing south-west monsoon season (June-September).

Meanwhile, an existing ‘low’ over the south-east Arabian Sea and adjoining Lakshadweep, is setting the stage for an intriguing interaction with the building Bay cyclone. The European Centre for Medium-Range Weather Forecasts had suggested that the two systems could feed off each other, helping both strengthen. Under that scenario, the Arabian Sea counterpart would move up along the Kerala-Karnataka coast towards Goa.

The IMD, however, suggests south-westerly flows could steer the Arabian Sea low back across the South Peninsula towards the south-west Bay, close to south Tamil Nadu and north Sri Lanka, from where it had originated. It could merge with the developing cyclone to the north-east over the larger Bay. Such a convergence could give the north-east monsoon another powerful burst next week, keeping the Southern Peninsula firmly in the rain belt even as the Bay system gathers strength.

Meanwhile, the meteorological subdivision of Tamil Nadu, Puducherry and Karaikal has turned in a stellar rainfall performance in October, particularly since the north-east monsoon set in on October 15, according to IMD statistics. It moved into surplus territory from October 1, recording 23 per cent more rainfall than normal during the first 21 days of the month. The north-east monsoon only fuelled the surplus to swell to 109.3 per cent during October 15-21, a dramatic reversal after months of rainfall stress.

The outlook remains encouraging. The IMD has forecast normal to above-normal rainfall over the subdivision during the two weeks from October 22 to November 4, with the successor ‘low’ to the cyclone kicking in.

Elsewhere in the region, the north-east monsoon has brought sharply contrasting fortunes, with some subdivisions staging a spirited recovery while others remain mired in rainfall deficits. Coastal Karnataka and South Interior Karnataka have made particularly striking comebacks. Coastal Karnataka’s rainfall tally swung from a 33 per cent deficit during October 1-21 to an 83 per cent surplus during October 15-21.

South Interior Karnataka, meanwhile, turned a 39 per cent deficit into a 58 per cent surplus over the comparable periods. Other subdivisions have seen deficits narrow but remain in negative territory. Coastal Andhra Pradesh and Yanam improved from a 71 per cent deficit during October 1-21 to 33 per cent during October 15-21. North Interior Karnataka trimmed its deficit from 88 per cent to 66 per cent.

Published on October 23, 2026