Cyclone Amphan is expected to cause "phenomenal flooding" when it strikes India's coast later today, an official private weather forecaster Skymet said, tracking the path of the storm as it barreled towards India.
It is the first super cyclone in 20 years, since the one that devastated Odisha in 1999, said GP Sharma of Skymet.
Pointing at the eye of the cyclone, around 100 km from Odisha's Paradip port, Mr Sharma said it would gather strength and speed with winds at 150 km per hour speed as it approached Bengal.
"It will cause phenomenal flooding," he said.
"As it crosses Odisha, there will be more than 200 milimetres rain in Paradip, Chandbali, Balasore and Bhadrak," he said. The wind speed was likely to be more than 100 km per hour.
While Amphan is expected to make landfall at Digha in West Bengal, Mr Sharma predicted a spot further northeast, in the Sundarbans.
According to government updates, Amphan will cross between Digha and Hatiya close to the Sundarbans after 4 pm with a wind speed of 155-165 km per hour, increasing to 185 km per hour.
"The storm surge and tidal waves are going to be very strong. Waves are likely to be four to six metres," said National Disaster Response Force chief SN Pradhan said.
Storm surges can force a wall of water to flow several kilometres inland and are often responsible for massive loss of life during severe cyclones.
Though weakened from super-cyclone to extremely strong cyclonic winds, experts warn the storm could still be strong enough to "cause large-scale and extensive damage".