The South-West monsoon is waiting for the current wet spell over North-West India to lift before it can start its withdrawal, a process that has been delayed by close to a month.

It is not as if it has been raining hard through September, but the non-seasonal cyclone Daye was enough to literally pour cold water on a surface that was drying up to bid goodbye to the monsoon.

The remnant low-pressure area from Daye is still drenching the hills and adjoining plains of North-West India by interacting with a western disturbance coming in from across the border.

The interactive rain is forecast to continue for another day on Tuesday, according to the India Met Department, following which the rain would start lifting gradually.

Dry weather may set in over Rajasthan from Tuesday. It would combine two tell-tale features associated with beginning of the the withdrawal phase of the monsoon: reduction in the moisture associated with the monsoon flow and a changeover in the low level wind pattern over this region from Thursday.

The low-level winds would turn distinctly anticyclonic (clockwise), preventing a cloud build-up unlike in cyclonic (anti-clockwise) winds, leading to dry and hot air.

This would gradually spread out to East, Central and Peninsular India until the last vestiges of the South-West monsoon are blown away, leaving space for the North-East monsoon (winter monsoon).

N-E monsoon timeline

According to the US National Weather Services, the stage for the North-East monsoon could be set from October 10 when helpful easterly waves are forecast to enter the South-East Bay of Bengal.

The normal timeline for the North-East monsoon to set in is around October 15-20; so early indications as given out by the US agency suggest that its arrival may not be delayed this year.

The easterly waves, which resemble western disturbances in the North but move in the opposite direction, are directed mostly at Sri Lanka and the adjoining Tamil Nadu coast. At times, they have gone on to set up depressions and even cyclones, but no such indications are available around the next 15 days when they are shown entering the Bay.

These waves are in turn being generated by typhoons/storms in the West Pacific, which cross the South China Sea and the Gulf of Thailand to enter the Bay. Currently, there are least four suspect areas of typhoon genesis after super typhoon Mangkhut churned the waters to set up cyclone Daye in the Bay.

Meanwhile, the remnant of cyclone Daye dropped heavy to very heavy rain with isolated extremely heavy rain over Punjab and Himachal Pradesh during the 24 hours ending Monday morning.

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