Depression alert in Arabian Sea as second low-pressure area forms

Vinson Kurian Thiruvananthapuram | Updated on December 01, 2019 Published on December 01, 2019

Chennai's Valmiki Nagar beach at 5 pm on Sunday Photo: Bijoy Ghosh

Heavy to very heavy rain forecast for TN two more days; schools to remain closed in Puducherry, Kanchipuram, Chengalpattu and Cuddalore


An anticipated second low pressure area has formed over the South-East Arabian Sea and adjoining Lakshadweep area, promising to send the North-East Monsoon to another peak over the next few days.

Schools will remain closed in Puducherry, Kanchipuram, Chengalpattu and Cuddalaore. Schools as well as colleges will remain closed in Thoothukudi and Thiruvallur districts

The India Meteorological Department (IMD), New Delhi, has said the low could move to the West-North-West into East-Central Arabian Sea and gradually intensify into a depression over the next 3-4 days.

Squally weather, high winds, heavy rain

The IMD has warned of strong winds and squally weather over the Arabian Sea, the Lakshadweep-Comorin area and along and off the Kerala-Karnataka coasts during the next two days.

The convergence of strong north-easterly winds will sustain the ongoing heavy-to-very-heavy rainfall activity over Tamil Nadu for as many days. Heavy-to-very-heavy rainfall may break out at isolated places over Kerala, Lakshadweep and Coastal and South Interior Karnataka during the same period.

Tamil Nadu: Light-to-moderate rainfall at most places and heavy-to-very-heavy falls with extremely heavy falls at isolated places till tomorrow (Monday) and heavy falls at a few places with very heavy falls at isolated places into Tuesday.

Kerala and Lakshadweep: Light-to-moderate rainfall at most places and heavy-to-very-heavy rainfall at isolated places into Monday and isolated heavy falls on Tuesday.

Coastal & South Interior Karnataka: Light-to-moderate rainfall at many places and heavy falls at isolated places on Monday and Tuesday.

Warning for fishermen

The IMD has issued a wind warning for fishermen (advised not to venture into the sea areas as specified):

Monday: Squally weather (wind speed 40-50 km/hr) may prevail over the South-West Arabian Sea and Lakshadweep area; squally weather (wind speed 45-55 km/hr gusting to 65 km/hr) may prevail over the South-East and adjoining East-Central Arabian Sea; squally weather (wind speeds of 40-50 km/hr) may prevail along and off the Kerala and Karnataka coasts.

The IMD also has hinted at a reduction of rainfall over the South Peninsula, apparently after the depression/cyclone pulls away to farther North into the open East-Central Arabian Sea.

Global predictions

The US National Centres for Environmental Prediction-Global Ensemble Forecast System (NCEP-GFS) has retained the outlook for a minimal cyclone forming over the East-Central Arabian Sea, steaming away to farther North some distance away from India's West Coast and weakening off the coastal waters off Gujarat.

The Climate Prediction Centre of the US National Weather Service hinted at a constructive interaction between a Madden-Julian Oscillation (MJO) wave and a strong positive phase of the Indian Ocean Dipole (IOD).

This is helping to anchor enhanced convection (cloud-building and rainfall) over Africa and the Western Indian Ocean (and adjoining South Arabian Sea).

Ineteraction between MJO, positive IOD

The MJO wave moves periodically from West Africa to the Indian Ocean and boosts ongoing weather activity. Its interaction only briefly weakens the positive IOD, another prop for the North-East monsoon.

This explains the concentrated action over the Arabian Sea where two low-pressure areas are operational concurrently. Opinion is divided as to whether the MJO wave would re-emerge over the Bay of Bengal. Here is where a forward-looking assessment by the NCEP-GEFS about fresh easterly wave activity, topped off by a likely low-pressure area being triggered over the Bay around December 13, becomes relevant.

There is also an outlook for continued buzz over the West Pacific-South China Sea where Typhoon Kammuri is already making big waves on its approach to the Philippines and further into the South China Sea.

Meanwhile, many parts of Tami Nadu have been battered by heavy-to-very-heavy rain during the last 24 hours, ending on Sunday morning. Major stations recording it included Satankulam (19 cm), Cuddalore, Thhothukudi and Kurinchpadi (17 cm each), Manimutharu (15 cm), Vedaranyam (14 cm), Chheyur, Ulundurpet, Maduranghagam, Chidambaram, Trangambadi, Kuppanatham and Bhuvanagiri (13 cm each).

A number of other centres received very heavy rainfall of 12 cm, 11 cm and 10 cm during the period under reference, an update by the Chennai Met Office under the IMD said.

Published on December 01, 2019
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