The meteorological subdivision of Tamil Nadu, Puducherry and Karaikal is now under a heavy rain spell as a fresh low-pressure area over South-East Bay of Bengal and adjoining Andaman & Nicobar Islands threatens to intensify as a depression by Wednesday. As expected, the system may fling itself into a track farther away, intensify further, and head towards Odisha.

Deep depression 

India Meteorological Department (IMD) said a depression has formed over the West-Central Bay and may move West-North-West and intensify as a deep depression (a whiff away from being a cyclone) off the Andhra Pradesh coast by Thursday and recurve to North-North-East towards the North-West Bay off the Odisha coast Friday. Though going away, the system could open up the Tamil Nadu coast for successive swoops by rain-driving easterly waves or circulations, as per a short-term outlook.

What is seen as also helping the immediate cause of Tamil Nadu on Tuesday is another upper air cyclonic circulation over the South-West Bay and adjoining Sri Lanka. A trough runs from this cyclonic circulation to the prevailing low-pressure area. It may sustain presence over the region despite the intensification of the ‘low’ and away-movement as a depression. 

Heavy rain alert

A rain alert issued by the IMD said light to moderate rainfall is likely at many places over the coastal districts of Tamil Nadu, Puducherry and Karaikal with isolated heavy to very heavy rainfall and isolated extremely heavy rain on Tuesday and Wednesday. Light to moderate rainfall at many places with isolated heavy rainfall is likely also over the coastal districts of Andhra Pradesh on both days even as the interior of both regions may make only moderate gains.

The track of the prospective depression or deep depression would bring light to moderate rainfall at a few places over the coastal districts of Odisha and West Bengal on Wednesday. It would increase to light to moderate rainfall at many places with isolated heavy rainfall on Thursday and Friday and isolated very heavy rain over Odisha coast on Thursday. Light to moderate rainfall at many places with isolated heavy rainfall likely also over the North-Eastern States in the weekend. 

A few global models indicated elevated rain prospects from a second system running away from Tamil Nadu coast for the Andhra Pradesh, Odisha and West Bengal coasts during the last week of November and into early December. This could come about as the system developing off Tamil Nadu on the heels of the depression aping the former in near-identical fashion. 

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