Monsoon may have drawn to a close, but not the wind pattern or rainfall regime

The South-West monsoon season may have officially drawn to a close on September 30 but not entirely the associated large-scale wind flow pattern, and therefore, the chances of moderate to heavy rain over disparate parts of the country for the rest of this week.

Circulations merge over Bay

This is best evidenced in the merger of a persisting cyclonic circulation over the Bay of Bengal with an incoming one, a remnant of erstwhile typhoon ‘Noru’ from the South China Sea that had hit Vietnam last week. BusinessLine had mentioned last week the possibility of the merger of the two weather systems and rain for the hinterland. In line with the typical track of movement for monsoonal systems, the merged cyclonic circulation is projected to move West-North-West after it crosses the Andhra Pradesh coast, past Central India towards North-West India where the monsoon withdrawal process has already been stalled.

Rains for North, East India

India Meteorological Department (IMD) has forecast a heavy rainfall spell may commence over Himachal Pradesh, Uttarakhand and Uttar Pradesh from Thursday for subsequent 2-3 days and hold the monsoon withdrawal line still along Jammu, Una, Chandigarh, Karnal, Baghpat, Delhi, Alwar, Jodhpur and Nalia. It has predicted heavy rains for over most parts of East and North-East India for next 3-4 days.

An extended weather outlook valid for three days until October 10 said scattered to fairly widespread light to moderate rainfall with isolated heavy to very falls is likely over Himachal Pradesh, Uttarakhand and Uttar Pradesh on Friday. Scattered to fairly widespread light to moderate rainfall is likely over Central, East, and North-East India, the Lakshadweep, and the Andaman and Nicobar Islands, and along the West Coast. Isolated to scattered light rainfall is likely over most of the country, except parts of North-West India and Gujarat, where dry weather is likely.

Wet weather for Peninsular India

The US Climate Prediction Centre concurs with the IMD and hints at moderate to heavy rain for eastern parts of North-West India and adjoining Central India until October 11. Later, a spell of less intense but occasional rain cover will establish over Maharashtra, Goa, Karnataka, Andhra Pradesh, Telangana, Tamil Nadu, and Kerala (except the extreme southern parts of the last two states) during October 12 to 18.

The latter period also coincides with the onset window for the North-East monsoon over the South Peninsula. The IMD’s numerical model projections hint at a couple of cyclonic circulations doing the rounds over the Bay of Bengal and across the South Peninsula into the Arabian Sea during a 10-day-interregnum until October 13, spreading scattered rain over the region, largely due to the south-westerly monsoon flows turning around the peninsular tip and heading into the Tamil Nadu coast. The wind pattern has to reverse for the North-East monsoon to establish here.

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