The monsoon depression that crossed the Gangetic West Bengal and Bangladesh coast last (Thursday) night took the cover of darkness to intensify double-quick into a deep depression, a single gust away from being a full-fledged tropical cyclone.
An India Meteorological department (IMD) warning said that heavy to very heavy rainfall would occur at a few places over north Orissa, coastal West Bengal and Jharkhand over the next two days.
It would be isolated heavy at places over south Orissa, interior West Bengal, Chhattisgarh, Konkan, Goa, coastal Karnataka and the Andaman and Nicobar Islands during this period.
Isolated thunder squalls have been forecast over Punjab, Haryana, Rajasthan and Uttar Pradesh thanks to local weather features.
Convective clouds are seen rising over Orissa, parts of Gangetic West Bengal, Punjab, western Himalayan region, Nagaland, Manipur, north coastal Andhra Pradesh, Kerala, north Bay of Bengal, north Andaman Sea and East Arabian Sea.
Conditions are favourable for the advance of monsoon over some more parts of Maharashtra, remaining parts of Telangana, Bihar, Jharkhand, Orissa and Chhattisgarh, some parts of east Madhya Pradesh and east Uttar Pradesh during next three days.
In this manner, the Bay system beat the depression in the Arabian Sea in terms of strength, prompting the US Navy’s Joint Typhoon Warning Centre (JTWC) to issue a cyclone formation midnight last night (5.30 a.m. IST).
As per the JTWC assessment, it is likely that the storm had intensified after crossing the coast, a rarity in itself.
The high vertical wind shear (sudden change in wind speed and direction that kills a storm) had ruled out any intensification over the seas.
Normally, storms weaken immediately after crossing the land after decoupling from the warm seawater ecosystem that fuel convection.
Exceptions are there when storms, on landfall, run into already flooded land that acts as a proxy for water surface and sustains convection internally to keep the storm structure mostly in tact.
What seems to have aided the Bay depression could be the presence of the extensively marshy Sunderbans area where the vertical wind shear was comparatively lower than the adjoining seas.
The JTWC assessed that the system had been moving in a west-northwestward track while crossing coast. A radar scan from Kolkata showed a defined circulation centre (storm nucleus) just inland of the coast with heavy rainfall right at the coast and over water.
Maximum sustained surface winds were estimated at 28 to 32 knots (52 km/hr to 59 km/hr), a couple of notches away from being a cyclone.
Meanwhile, an IMD said in an update in the morning that the deep depression lay centred over Gangetic West Bengal and adjoining Bangladesh, about 130 km northeast of Sagar Island and 80 km east of Kolkata.
The system is likely to move north-northwestwards initially and then west-northwestwards, likely steering it straight into north peninsular India and later west into the Mumbai-Gujarat area.
It might get weakened into a depression in the next 24 hours as it negotiates more rugged land features but would still pack quite a punch in terms of capacity to generate sustained rainfall along its path.
A likely interaction with a trough and its offshoot cyclonic circulations prevailing in the region could make it even more productive.
Towards the west, the offshore trough from Karnataka coast to Kerala lay in wait to receive the Bay system.
An India Meteorological department (IMD) warning said that heavy to very heavy rainfall would occur at a few places over north Orissa, coastal West Bengal and Jharkhand over the next two days.
It would be isolated heavy at places over south Orissa, interior West Bengal, Chhattisgarh, Konkan, Goa, coastal Karnataka and the Andaman and Nicobar Islands during this period.
Isolated thunder squalls have been forecast over Punjab, Haryana, Rajasthan and Uttar Pradesh thanks to local weather features.
Convective clouds are seen rising over Orissa, parts of Gangetic West Bengal, Punjab, western Himalayan region, Nagaland, Manipur, north coastal Andhra Pradesh, Kerala, north Bay of Bengal, north Andaman Sea and East Arabian Sea.
Conditions are favourable for the advance of monsoon over some more parts of Maharashtra, remaining parts of Telangana, Bihar, Jharkhand, Orissa and Chhattisgarh, some parts of east Madhya Pradesh and east Uttar Pradesh during next three days.
In this manner, the Bay system beat the depression in the Arabian Sea in terms of strength, prompting the US Navy’s Joint Typhoon Warning Centre (JTWC) to issue a cyclone formation midnight last night (5.30 a.m. IST).
As per the JTWC assessment, it is likely that the storm had intensified after crossing the coast, a rarity in itself.
The high vertical wind shear (sudden change in wind speed and direction that kills a storm) had ruled out any intensification over the seas.
Exceptions are there when storms, on landfall, run into already flooded land that acts as a proxy for water surface and sustains convection internally to keep the storm structure mostly in tact.
What seems to have aided the Bay depression could be the presence of the extensively marshy Sunderbans area where the vertical wind shear was comparatively lower than the adjoining seas.
The JTWC assessed that the system had been moving in a west-northwestward track while crossing coast. A radar scan from Kolkata showed a defined circulation centre (storm nucleus) just inland of the coast with heavy rainfall right at the coast and over water.
Maximum sustained surface winds were estimated at 28 to 32 knots (52 km/hr to 59 km/hr), a couple of notches away from being a cyclone.
Meanwhile, an IMD said in an update in the morning that the deep depression lay centred over Gangetic West Bengal and adjoining Bangladesh, about 130 km northeast of Sagar Island and 80 km east of Kolkata.
The system is likely to move north-northwestwards initially and then west-northwestwards, likely steering it straight into north peninsular India and later west into the Mumbai-Gujarat area.
It might get weakened into a depression in the next 24 hours as it negotiates more rugged land features but would still pack quite a punch in terms of capacity to generate sustained rainfall along its path.
A likely interaction with a trough and its offshoot cyclonic circulations prevailing in the region could make it even more productive.
Towards the west, the offshore trough from Karnataka coast to Kerala lay in wait to receive the Bay system.
