Agri Business

Monsoon vigorous over TN, East and North-East India

Vinson Kurian Thiruvananthapuram | Updated on July 10, 2020

Indifferent over South Peninsula, Central India

East and North-East India are getting a severe pounding from a monsoon which is behaving indifferently over the rest of the country in signs that it has entered a weak phase. But this is also the phase when the East Coast as well as Odisha, Coastal Andhra Pradesh and Tamil Nadu make gains as part of the season.

When the Westerly/South-Westerly monsoon winds from the Arabian Sea weaken, the Easterlies/South-Easterlies push in from the Bay of Bengal to set up convergence as demonstrated in the manner in which torrential rain of 11 cm that lashed Chennai during the 24 hours ending Friday morning.

Vigorous monsoon over TN

An update from the Regional Meteorological Centre, Chennai, said that the monsoon was vigorous over Tamil Nadu and active over Interior Karnataka and Telangana during the period. Rainfall occurred at most places over Kerala, Lakshadweep, Karnataka and Telangana; and at many places over Tamil Nadu and Puducherry and at a few places over Coastal Andhra Pradesh and Rayalaseema.

Major stations in Tamil Nadu recording 10 cm and above included (20 cm); Keeranur, Arakonam and Danishpet- 13 cm each; Virinjipuram, Cheyyur, and Sriperumbudur at 12 cm each; Chennai Airport, Alandur, Pudukottai and Perungalur- 11 cm each; and Anna University, Katpadi, and RK Pet-10 cm each.

In Coastal Andhra Pradesh, Kaikalur recorded 12 cm of rain; Gudivada, Narsapuram and Amalapuram at 11 cm each; Palakoderu and Salur at 10 cm each; Rayalaseema, Venkatagiri Kota, Puttur, and Palasamudram recorded 10 cm each; in Telangana, Venkatapuram at 13 cm each; in Karnataka, Kolluru recored 17 cm and Kadra at 11 cm.

Troughs off normal perch

In contrast, Palakkad (6 cm) recorded the highest in Kerala during the comparable field since the offshore trough, the main rain-generating feature in the South and along the West Coast, lay truncated mostly out into the Arabian Sea – off the Karnataka coast to the Lakshadweep Islands.

The offshore trough in the South and the monsoon trough over North India (nestling along the foothills of the Himalayas) need to revert to the normal positions for the monsoon to revive over Central and adjoining North-West India as well as South Peninsular India. This will require either formation of a low-pressure area in the Bay of Bengal or arrival of Madden-Julian Oscillation (MJO) wave.

The Australian Bureau of Meteorology said that a moderately strong pulse of the wave, which criss-crosses the Indian Ocean in intervals, is on the move but may start weakening into the next week. The MJO carries clouds and precipitation on its tracks and can also trigger formation of low-pressure areas.

Weak monsoon phase

But none such is being forecast in either the Arabian Sea or the Bay of Bengal, but it has set up some clouding along parts of Coastal Karnataka and North Kerala. A stronger pulse of the MJO wave could have helped the disoriented offshore trough to nudge itself back to proper position.

The upshot of all these is that the monsoon would continue to be oriented towards the foothills of the Himalayas, East and North-East India, and along the East Coast in the short term though some buzz taking place off the Andhra Pradesh (East Coast) would bear close watching.

Published on July 10, 2020

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