The ‘boiling’ waters (at 30-31 degrees Celsius) of the northern parts of the Bay of Bengal are waiting to host not one -- but at least two -- low-pressure areas/depressions over the next seven to 10 days and set off another wave of heavy to very heavy rains across East, Central and West India across West Bengal, Odisha, Chhattisgarh, Madhya Pradesh, Gujarat and parts of Rajasthan, apart from North-East India.

While the first system could present itself in the next four days off the Andhra Pradesh-Odisha coasts, the second one may get tossed up as many days later just to the North and North-East over Odisha, West Bengal and adjoining Bangladesh, according to the early projections by the numerical model run by India Meteorological Department (IMD), pending confirmation at ground level.

Delayed monsoon withdrawal?

Weather watchers are waiting to see if this September would have abnormal to excess rain, just like the last three years. In 2019, September saw 52 per cent excess rainfall, while in 2021, the month recorded 35 per cent excess rainfall. In 2020, there was above-normal rain of five per cent.

A wet to wetter September dragged the monsoon withdrawal date. In 2019, it was delayed to October 9, from the normal date of September 1. The withdrawal was delayed the most in that year. In 2020, the date was September 28, and in 2021, it was October 6.

As for this year, the wind pattern on Sunday morning over Rajasthan and Gujarat, from where the monsoon withdraws first, showed signs of disruption. This trend would get entrenched once resurgent south-easterlies get triggered in the run-up to formation as well as during the tenure of strong monsoon systems taking shape one after the other from the Bay. It remains to be seen if this would reprise 2021 when a string of low-pressure areas/depressions, including cyclone Gulab, marched across the Bay.

Draws support from La Nina

As was the case then, a helpful La Nina is buzzing over the tropical Pacific this time too.

The Bay of Bengal normally tones down its activity during September, which is better identified with the withdrawal of the monsoon progressively from North-West, East and Central India. But the IMD has said in its bulletin this (Sunday) morning that the eastern end of the backbone monsoon trough will shift back southward to its normal position from Monday, as if on cue, to receive the incoming low-pressure areas and signal the start to unusual September rain activity for a fourth consecutive year.