The India Met Department has withdrawn a warning with respect to intensification of the existing well-marked low-pressure area off north Tamil Nadu coast into a depression.

This came on a day after the ‘low’ dropped so much rain over north Tamil Nadu and neighbouring coastal Andhra Pradesh that the intensification would have made hardly any difference.

Slow mover A slow-moving ‘low’ generates more intense and long-lasting rain across a much wider geography than what a fleet-footed depression or a cyclone can bring to bear during a much shorter time.

This is what has come to play with the case of the prevailing well-marked ‘low,’ which is one step below the rank of a depression and two below that of a conventional cyclone.

The system has dropped such torrential downpour that at least three districts have recorded excess rainfall till date (as of October 16) of well over 100 per cent.

The three districts are Kancheepuram (133 per cent), Thiruvallur (123 per cent, hosts the Red Hills reservoir that supplies water to Chennai) and Vellore (116 per cent).

Strong winds Chennai district has recorded 82 per cent of excess rainfall till date. Puducherry, which had totted up -13 per cent (considered normal within the range prescribed by Met Department) rainfall until Monday, has entered into positive territory with a surplus of nine per cent.

Meanwhile, removal of the watch for a depression may not diminish the rain-generating capacity of the remnant ‘low.’ The Met has warned of strong winds along and off the coast of Tamil Nadu, Puducherry and South Andhra Pradesh on Tuesday.

Heavy to very heavy rainfall warning for the next two days is valid for Coastal Andhra Pradesh, Rayalaseema. There is no alert valid for Tamil Nadu.

Fresh rains But global models are of the view that fresh rains are due for coastal Tamil Nadu likely from Thursday as the well-entrenched ‘trough’ in the Bay of Bengal becomes active on its own.

Strong, moisture-carrying Easterly winds are predicted to blow in from the Bay into the Tamil Nadu coast during this phase.

The US Climate Prediction Centre points to a fresh rain wave of rain from South-East Bay of Bengal originating from around the Andaman and Nicobar islands.

North Coastal Tamil Nadu, including Chennai, should be prepared for another round of wet spell, though not as heavy as the ongoing one, from Thursday.

The moderate to at times heavy rain may last until November 28, the forecasts said.

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