Depression Arises Over South-West Bay; Potential to Worsen into a ‘Deep Depression’

After moving closer to the shores of Sri Lanka and Tamil Nadu overnight, yesterday's (Wednesday) well-marked low-pressure region has strengthened into a depression this (Thursday) morning over the South-West Bay of Bengal, according to the India Meteorological Department (MD).

The depression was located over South-West Bay and the adjacent Equatorial Indian Ocean around 470 kilometres south-southeast of Trincomalee (Sri Lanka), 760 kilometres south-southeast of Nagapattinam, 870 kilometres south-southeast of Puducherry, and about 950 kilometres south-southeast of Chennai (all Tamil Nadu, India).

Likely to Intensify

It is expected to strengthen into a deep depression (just one step below cyclone category) by tomorrow (Friday) and proceed to the north-west along and off Sri Lanka's east coast, towards the North Tamil Nadu coast on Friday and Saturday.

The Sri Lankan Meteorological Department had picked up a low-pressure region over the South-West and adjoining South-East Bay early this morning (Thursday) and placed it under watch as it moves west-northwest and away from the island nation on Friday and Saturday.

By midnight on Wednesday, the US Joint Typhoon Warning System had placed the system area about 699 kilometres east-southeast of Colombo, Sri Lanka. On the northern periphery, satellite images revealed an unclear but well-defined low-level circulation with deep convection (heavy clouding) (closer to Sri Lanka).

It needs to deal with moderate to severe vertical wind shear (an abrupt change in wind direction with height), which makes it unlikely to intensify beyond a certain point. The system's warm sea-surface temperatures of 29-30° C, on the other hand, compensate for this.

Heavy Rain in Tamil Nadu

Meanwhile, the IMD predicts scattered to widespread rainfall with isolated thunderstorm/lightning activity over Tamil Nadu-Puducherry-Karaikal until Sunday, as well as scattered to widespread rainfall with isolated thunderstorm/lightning activity over south Coastal Andhra Pradesh, Rayalaseema, and Kerala-Mahe from tomorrow (Friday) to Sunday.

From today (Thursday) to Saturday, isolated heavy to very heavy rainfall is expected over Tamil Nadu-Puducherry-Karaikal, with extremely heavy rainfall on Friday and isolated heavy on Sunday. On Friday and Saturday, isolated heavy rainfall is expected in South Coastal Andhra Pradesh and Rayalaseema.