Mini tornado hits villages of West Bengal before cyclone

KOLKATA : Before cyclone Yaas could hit the Odisha – West Bengal coast on Wednesday morning, videos of a tornado swirling over villages and the river Ganga in south Bengal were widely shared on social media .

The incident took the residents of Bandel and Chinsurah in the Hooghly district and Halisaha in the North 24 Parganas district by surprise, however, the meteorological experts said tornadoes can develop before an approaching cyclone or a major thunderstorm.

“When a cyclone approaches, such vortex develops because of the difference in wind speed in the upper air and the ground level, known as vertical windshear. This is, however, not a full tornado, It is a mini tornado,” said Sanjib Banerjee, deputy director general of India Meteorological Department’s regional office in Kolkata.

“A tornado is basically a column of air rotating violently that extends from a thunderstorm to the ground. It tears and lifts everything in its path,” said a meteorological department official.

The cyclone Yaas landfall began near Dhamra port in Odisha on Wednesday morning, even as strong winds and heavy tides saw seawater enter in many coastal towns and villages in Odisha and West Bengal ahead of the landfall.

The “very severe cyclonic storm” packed sustained winds of 130-140 kilometers (up to 87 miles) per hour and gusts of up to 155 kph (97 mph) when it made landfall, the IMD said.

Chief minister Mamata Banerjee said at least two persons were electrocuted when the mini tornado hit parts of the two districts, and around 40 houses were damaged.

Such mini tornadoes have been seen earlier in the district of Murshidabad in west Bengal and also in Odisha experts said. Even though it is rare, but thunderstorm activity occurs when a cyclone approaches, they added.

“They [tornadoes] can happen when a cyclone or a thunderstorm approaches. Just like a pilot car moves ahead of a VIP convoy, these mini tornadoes act like a pilot of the cyclone, occurring before a cyclone comes,” said KJ Ramesh, former head of the IMD. In the early 70’s, Delhi witnessed a mini tornado ahead of a thunderstorm in which an entire bus was lifted in the air by the vortex, Ramesh said.

If the tornado passes over a water body or a river, it starts lifting the water. There were examples from Odisha where a mini tornado had emptied an entire pond by lifting the water.

“Just like a cyclone and a thunderstorm, a tornado too needs heat and moisture to develop,” said RK Jenamani, senior scientist of IMD.

When a cyclone approaches, such vortex develops because of the difference in wind speed in the upper air and the ground level, known as vertical wind-shear. This is, however, not a full tornado, It is a mini tornado. SANJIB BANERJEE, deputy director general , IMD