The withdrawal of the South-West monsoon is gathering pace with more parts of Central India and North Peninsular India expected to be covered during the weekend.

Dry north-westerly winds from the deserts of Rajasthan are now seen pushing into Central India and curving towards the south-west to blow away the last vestiges of the incumbent monsoon.

Dry air fills North

The US National Centre for Environmental Prediction shows that the dry air has filled most of the northern half of the country and is about to engulf the southern half as well.

But the north-westerlies are curving back into land to form a weak cyclonic circulation over Kerala and Coastal Karnataka, triggering some rain in the process over adjoining Tamil Nadu as well.

The Chennai centre of the India Met Department said that the remnant South-West monsoon was active over South Interior Karnataka during the 24 hours ending on Thursday morning.

Rainfall occurred at most places over South interior Karnataka, at a few places over Kerala, Lakshadweep, Coastal Karnataka and Tamil Nadu and at one or two places over Andhra Pradesh, Telangana and North Interior Karnataka.

Pattern to hold

Thirukoilur in Villupuram district in Tamil Nadu recorded very heavy rain of 10 cm during this period.

Sankarapuram and Villupuram town, also in the same district, recorded 9 cm.

This pattern will more or less hold for another week or so, before a stronger circulation forms over the Bay of Bengal to decidedly shift the wind flow from being north-westerly to easterly to north-easterly.

This is expected to ultimately lead to the onset of the North-East monsoon, but indications are that the typically thundery showers associated with the season may not materialise before October 20.

The US agency has put under watch a cyclonic circulation crossing Indochina and set to slide into the Bay of Bengal off Myanmar by Monday (October 17).

Cyclonic circulation

Indications are that this could grow into the threshold size and acquire critical mass to force a shift in the wind flow from north-westerly to north-easterly.

Meanwhile, the US Climate Prediction Centre suggests that a helpful Madden-Julian Oscillation wave may start transiting the Indian Ocean to the south of Sri Lanka around May 19.

The arrival of the Madden-Julian Oscillation wave is usually taken as a signal for the onset of the monsoons (South-West or North-East) and even the genesis of rain-setting low-pressure areas or even cyclones.

However, a storm tracker of the US Climate Prediction Centre has suddenly gone silent over the prospect of rain-driving circulations marching across the Bay of Bengal during the rest of October.

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