At 12.00pm, the depression was centred over northwest Bay and adjoining Bangladesh and India's West Bengal. It is likely to intensify further and move more northwestward.

"Sea will remain rough near the centre of the deep depression. Under its influence, deep convection is taking place over the north Bay and adjoining coastal areas" the weather department said.

Deep convection refers to the thermally driven turbulent mixing that moves air parcels from the lower to the upper atmosphere.

All fishing boats and trawlers in the northern Bay of Bengal and deep sea have been advised to take shelter immediately.

The low-lying areas of Satkhira, Khulna Bagerhat, Jhalokathi, Pirojpur, Barguna, Patuakhali, Bhola, Barishal, Laxmipur, Chandpur, Noakhali, Feni Chattogram, Cox's Bazar and their offshore islands and chars are likely to be inundated by rising tides, BMD said.