Was there a tornado in Sheffield and what caused it?

The cloud over Crookes, Sheffield, shortly before the first lightning strike. Credit: Noah Lomax
The cloud over Crookes, Sheffield, shortly before the first lightning strike. Credit: Noah Lomax
0
Have your say

Last night many people in Sheffield thought they were witnessing the end of the world.

Lightning strikes, peals of thunder and foreboding black skies descended on South Yorkshire yesterday evening - just in time for Sheffield Wednesday's match against Bristol City.

Lightning over Thorpe Hesley last night. Credit: Amy Johnston

Lightning over Thorpe Hesley last night. Credit: Amy Johnston

Edward Hanna, Professor of Climate Change at the University of Sheffield, said the violent storm that swept across the city could have been a tornado.

Although some people might think tornadoes are confined to the mid-west of the U.S., the UK in fact has 35 to 40 tornadoes a year - more than any other European country.

A tornado develops from a large cumulonimbus cloud containing areas of rotation known as mesocyclones, according to the Royal Meteorological Society.

Strong draughts within the cloud drag the mesocyclones down to the ground, which looks like a dark funnel of air.

Diagram of tornado formation. Credit: U.S. National Oceanic and Atmospheric Administration (public domain)

Diagram of tornado formation. Credit: U.S. National Oceanic and Atmospheric Administration (public domain)

A tornado is formed at the point that this funnel of air is in contact both with the cloud and the ground.

Watch footage of the 'tornado'

When land areas are taken into account, the UK actually has the highest frequency of reported tornadoes per unit area in the world, according to The Tornado and Storm Research Organisation.

Compared with hurricanes, tornadoes are much smaller and last for less time. The most extreme tornadoes reach speeds of 300 miles per hour and a kilometre in width, but these are very rare.

Hurricanes form over sea water when the sea surface temperature is at least 27 degrees Celsius. By definition, a hurricane’s average wind speeds are at least 73 miles per hour and it will be around 100 miles wide.