Alert sounded as weather system in Bay may turn into a deep depression

The low-pressure area over the East-Central Bay of Bengal has become ‘well-marked,’ and the latest outlook indicates that it could go on to become not just a depression but a deep depression.

A deep depression is second only to a tropical cyclone in intensity, and, in this manner, the ‘low’ would have strengthened three times rapidly to attain this status by Thursday.

Landfall by Thursday night

The system is expected to head west-north-west towards the North Andhra Pradesh South Odisha coasts and cross the coast between Kalingapatnam and Puri late on Thursday night or early Friday morning.

The India Met Department (IMD) has forecast heavy rain over the North-Eastern States, Coastal Odisha, Coastal Andhra Pradesh, Telangana, Rayalaseema and Tamil Nadu and Puducherry on Wednesday.

Thunderstorms accompanied by lightning may line up over Coastal Andhra Pradesh, Telangana, Interior Karnataka, Konkan, Goa and Madhya Maharashtra.

Warnings of ‘rough’ to ‘very rough’ (wave heights between eight ft and 20 ft) conditions have been issued for the South and Central Bay, the Andaman Sea and along and off the Andhra Pradesh, Bengal and Odisha coasts.

Fishermen are advised not to venture into the sea in these areas.

As for tomorrow (Thursday), the rains may grow in intensity with heavy to very heavy rain accompanied by extremely heavy falls lashing Odisha and North Coastal Andhra Pradesh.

Rainfall will be heavy to very heavy over Chhattisgarh and Telangana while being heavy over the plains of Bengal, Jharkhand, Rayalaseema and Karnataka.

Thunderstorms accompanied by lightning are likely at isolated places over Coastal Andhra Pradesh, Telangana and Interior Karnataka.

Forecast

The forecasts for the next three days are as follows.

Friday: Heavy to very heavy rain over Odisha, Vidarbha and Chhattisgarh; heavy rain over Assam, Meghalaya, plains of Bengal, Jharkhand, Madhya Pradesh, Konkan, Goa, Madhya Maharashtra, Marathwada, Telangana and Karnataka.

‘Rough’ to ‘very rough’ sea conditions possible over West-Central and the North Bay and along and off the Andhra Pradesh, West Bengal and Odisha coasts.

Saturday: Heavy to very heavy rain over East Rajasthan; heavy rain over Assam, Meghalaya, West Uttar Pradesh, Uttarakhand, Haryana, Chandigarh, Delhi, Himachal Pradesh, Madhya Pradesh, Konkan, Goa, Madhya Maharashtra, Marathwada and Vidarbha.

Saturday: Heavy to very heavy rain for Uttarakhand, Haryana, Chandigarh, Delhi, Punjab and Himachal Pradesh and heavy rain over West Uttar Pradesh and Rajasthan.

In this manner, the rains, penetrating right into West Rajasthan, would have forced the withdrawal scheme for the South-West monsoon from Rajasthan back to the drawing board.

Earlier in the morning, the US Joint Typhoon Warning Centre had located the causative ‘low’ over the East-Central Bay of Bengal to 714 km South of Chittagong in Bangladesh.

The IMD had not referred to the scope of the depression strengthening until Wednesday noon, apparently because the sea-surface had not warmed much beyond the threshold 27-29 deg Celsius.

Wind-shear factor

But vertical wind-shear values, which refer to sudden change in wind direction that unsettles a building system, are low to moderate at 37 km/hr. They tend to be high during an active monsoon, which is why tropical cyclones are rare during that phase of the monsoon. Cyclones tend to develop during the monsoon transition phase.

For this reason, the behaviour of the sea is closely monitored during the months of May (just ahead of the onset of the South-West Monsoon) and September-October (ahead of the onset of the North-East monsoon).

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