The trough linking the cyclonic circulation over Tamil Nadu has shifted orientation from the South-East Arabian Sea towards North Interior Karnataka on Wednesday evening, sustaining the north-easterly monsoon winds along and off the North Tamil Nadu and adjoining coastal areas of South Andhra Pradesh.

It will cause fairly widespread to widespread light to moderate rainfall with isolated heavy falls, thunderstorms and lightning over Tamil Nadu, Puducherry, Karaikal, Kerala and Mahe until Sunday. Isolated very heavy rainfall is forecast over Tamil Nadu, Puducherry and Karaikal on Friday and Saturday, an update from India Meteorological Department (IMD) warned. 

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Heavy to very heavy rain

The 24 hours ending on Wednesday morning some of the highest rainfall amounts falling so far this season over Tamil Nadu, Puducherry and Karaikal. Chief among them (above 10 cm) were: Perambur, Chennai Collectorate and Avadi-17 each; Kattukuppam and Ponneri-16 each; Red Hills and Gummidipoondi-14 each; Sholinganallur, Cheyyur, MGR Nagar, Ambathur, Nungambakkam, Ayanavaram and Villivakkam-13 each; Anna University-12; Thirupporur, DGP Office and Srivilliputhur-11 each and Chennai Airport-10. In neighbouring Coastal Andhra Pradesh, Sullurpeta and Tada recorded 11 cm each. 

May shift again to South

According to the US National Centres for Environmental Prediction, the ongoing week (November 2-10) could likely see the heaviest of rainfall targeting the southern coast of Tamil Nadu, Kerala and Sri Lanka to the South. Numerical model projections from the IMD seemed to agree indicating the possibility of the southern coast being bombarded by seemingly unending easterly wave activity front-ended by cyclonic circulations off the Sri Lanka and adjoining Tamil Nadu coast. A peer circulation likely being thrown up over the South-East Arabian Sea to the West may accentuate the flows.  

Robust South China Sea flows

Tropical storm ‘Nalgae’ in the upstream South China Sea had a principal role in pushing in the flows from beyond the territorial waters. On Wednesday evening, Nalgae was closing in on Hong Kong and the adjoining South-East coast of mainland China for a landfall. But incoming flows into the Bay are projected to stay robust for the next 10 days, according to global models. 

This should keep the North-East monsoon in good stead over the Bay of Bengal and the South Peninsula. An extended outlook from the IMD said that the three days from Monday to Wednesday next (November 7 tom9) will likely see fairly widespread to widespread light to moderate rainfall over parts of the South Peninsula, the Lakshadweep and the Andaman and Nicobar Islands, with isolated heavy falls likely over Tamil Nadu and Kerala.

Weather blogger’s take

https://twitter.com/RainStorm_TN/status/1587657651936460806

https://twitter.com/RainStorm_TN/status/1587635815034671107 

https://twitter.com/rsiva229/status/1587651765024935941 

https://twitter.com/JW_Chennai/status/1587632842447912960 

https://twitter.com/ChennaiRains/status/1587633517185232896 

https://twitter.com/ChennaiRains/status/1587633517185232896 

https://twitter.com/ChennaiRains/status/1587633521123676160 

https://twitter.com/jhrishi2/status/1587564062535204864 

https://twitter.com/jhrishi2/status/1587548452535296001 

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