Agri Business

Strong N-E monsoon may spill into early November, says US agency

Vinson Kurian Thiruvananthapuram | Updated on October 20, 2019 Published on October 20, 2019

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A weather tracker featured by the Climate Prediction Centre (CPC) of the US National Weather Services says the ongoing strong North-East monsoon activity would spill into early November.

An October 1-based outlook by the Application Laboratory of Japanese national forecaster Jamstec had said that November and December may not prove as productive October.

Counterpart ‘Low’

The US agency's outlook for the next eight-day-period takes the persisting low-pressure area over East-Central Arabian Sea (North of Lakshadweep) as an intensified system towards the Konkan-Mumbai coast.

During the same period, the Bay of Bengal (off the Tamil Nadu coast) would have erupted, throwing up a 'low' of its own, taking it towards the South Coastal Andhra Pradesh and then into the hinterland.

The stage would then be left back once again to the South-West Bay of Bengal coast off the Sri Lanka coast and adjoining South Tamil Nadu coast, presaging some spectacular weather activity.

The US agency sees the system crossing over to the Arabian Sea on the other side partly across the extreme South Peninsula and the adjoining Gulf of Mannar to turn around the peninsular tip to Kerala coast.

If this forecast verifies, this would more or less represent the track taken by very severe cyclone Ockhi a couple of years ago, inflicting severe damage to the Lakshadweep and Kerala coasts.

According to the US agency, the forecast system here undergo calibrated intensification into a depression, even a cyclone, and going by the its forecast, head for the Yemen coast.

All this is expected to happen over a period of the next 10 to 12 days, driving up the North-East monsoon many times over, even as fresh activity gets triggered downstream to the East over the Andaman Sea.

MJO Wave arrives

This is being attributed to the enhanced activity all the way from the Arabian Sea into the Bay of Bengal and further East into the South China Sea, from where the last-mentioned wave of rainfall would originate.

This in turn is tied with the movement from West to East of a weather-enhancing Madden-Julian Oscillation (MJO) wave from its first port of call over the South-West Arabian Sea and adjoining Indian Ocean.

The MJO wave travels periodically across the higher levels of atmosphere with its entourage of moisture, clouds and precipitation bringing associated weather to areas under its footprint.

The increase in MJO amplitude would result in continued enhancement of lower-level easterly anomalies (of the North-East monsoon) persisting over the equatorial Indian Ocean through the rest of October.

Meanwhile, two storms in the West Pacific - ‘Neoguri’ and ‘Bualoi’ - may just have helped to ramp up the easterlies into the South China Sea and further into the Bay of Bengal.

And these are feeding into the ‘low’ over the East-Central Arabian Sea and likely contributing to its staying power, backed up the warm waters and low wind shear values.

The warmth of the water aids the process of convection (cloud-building) and shape up the storm tower while low vertical shear (sudden change in speed and direction of wind) further consolidates this process.

More heavy rain

Meanwhile, India Met Department (IMD) on Sunday afternoon said that the low-pressure area over the East-Central Arabian Sea has persisted, though without intensification.

All India weather summary and monsoon forecast

 

A trough runs from this 'low' area to Vidarbha across North Interior Karnataka and Telangana, and is principally responsible for drawing monsoon moisture in and precipitating over the hinterland.

Additionally, another cyclonic circulation lies over the Comorin area, from where another trough runs across to North Coastal Andhra Pradesh.

The two troughs, which store and distribute the moisture drawn from the seas across the peninsula, cause it to fall as heavy to very heavy rain, and thundershowers accompanied by lightning.

The IMD has forecast fairly widespread to widespread rainfall with isolated heavy falls over the South Peninsula during the next four to five days.

Heavy to very heavy rainfall is also likely over the region on October 23 and 24 (Wednesday and Thursday) while Kerala, Tamil Nadu, and Puducherry may witness heavy to very heavy rainfall for four days.

Thunderstorms accompanied with lightning may roam around the South Peninsula during next three days. Fairly widespread rainfall with isolated thunderstorm and lightning is forecast for Maharashtra during this period.

Link: http://www.imd.gov.in/pages/allindiawxfcbulletin.php

Published on October 20, 2019
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