Conditions ripe for onset of North-East monsoon

Weather models do not indicate the possibility of any major development in the Bay of Bengal during the next fortnight, which normally witnesses the arrival of the North-East monsoon.

The month of October, which marks the shift from the South-West to North-East monsoon, has, in the recent past, witnessed major cyclones such as 'Titli' (2018), 'Phailin' (2013) and 'Hudhud' (2014).

Supportive environment

Elevated sea-surface temperatures and low 'wind shear' in the Bay of Bengal have helped incoming remnants of land-falling storms from the South China Sea/ North-West Pacific to develop as depressions/ cyclones here.

'Wind shear' refers to the sudden change in wind speed and direction with height. These values are high during a monsoon, and do not allow the cyclone tower structure to build.

With the monsoons weakening on either side of the peninsula - the Arabian Sea and the Bay of Bengal - conditions are ripe for rearing of major developments in the seas.

The Climate Prediction Centre of the US National Weather Service, however, has pointed to a buzz over the Arabian Sea next week, which would hasten the arrival of the North-East monsoon.

Otherwise, the country is quickly moving into monsoon transitional weather, with a string of assorted cyclonic circulations and troughs taking charge over many areas.

Western disturbance

These systems are enjoying a free run since the monsoon south-westerlies and easterlies, respectively, from the Arabian Sea and the Bay of Bengal, have become conspicuous by their near absence.

Prominent among these are a western disturbance from across the Rajasthan and Gujarat border, which is causing scattered to fairly widespread rainfall and thunderstorms along the hills of North-West India.

The weather activity here would last for a couple of days, even as similar weather conditions are forecast over the South Peninsula, East and North-East India.

A cyclonic circulation each hovers over interior Odisha and North-West Uttar Pradesh, while a trough runs down from South Chhattisgarh, extending all the way to coastal Karnataka.

The trough makes for an atmospheric conduit for the moisture to fill from South Chhattisgarh to coastal Karnataka, cutting across Telangana and interior Tamil Nadu.

Heavy rain at Haveri

Another trough runs down from the Comorin to the East-Central Arabian Sea, across south Tamil Nadu and north Kerala, which is expected to give rise to thunderstorms accompanied by lightning and thunder-showers.

The 24 hours ending this (Sunday) morning saw heavy rainfall at isolated places over interior Karnataka and coastal Andhra Pradesh, an India Met Department (IMD) update said.

The main centres receiving significant rainfall (in cm) included Haveri 11, Machilipatnam and Chickmagalur, seven each; Belgaum and Matheran five each; Kochi, Athiramapattinam, Dharwad, Kothagudem, Malda and Kolkata (Dum Dum) four each; and Nashik City and Balasore three each.

An extended outlook for the three days from October 11 to 13 forecasts fairly widespread to widespread rainfall, with isolated heavy falls, over parts of East and North-East India.

Scattered to fairly widespread rainfall is likely to occur over the rest of the country, except over Punjab, Haryana, Rajasthan, Gujarat and Madhya Pradesh, where dry weather marked by the withdrawal of the monsoon, is likely.

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