Shock as 'tornado' whirls around Scottish town in bizarre moment

Excited weather-watchers took to social media after a 'twister' was sighted over a Scottish town today.

The funnel cloud over Johnston, Renfrewshire. Picture: Dave Morrison, Twitter

Residents of Johnstone, Renfrewshire shared images of a 'tornado'. It is understood there was no structural damage to buildings in the area.

BBC meteorologists took to the web to explain that the phenomenon is known as a funnel cloud and can only be classed as a tornado if it is in contact with both the ground and a cumulonimbus cloud.

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The funnel clouds form during thunderstorms or heavy rain. They are made up of condensed water droplets which are rotated and drawn into a cloud. If they reach the ground, they are described as tornadoes. If, however, they are in contact with the sea they are known as waterspouts.

BBC Scotland Weather's Christopher Blanchett explained: "Within the funnel, the pressure is low enough to cause condensation, and so we are able to see the rotating cloud stretching downwards in a funnel-like shape.

"A funnel cloud can only be classified as a tornado when the circulation stretches all the way from the cloud base to the ground. As a result, funnel clouds are more common than tornadoes, but a spectacular sight nonetheless.

"Whilst we don't see them that often, they're certainly not unheard of in Scotland and can occur anywhere with the right conditions."

Freak weather has struck across the UK. In Derbyshire, residents of Whaley Bridge have been ordered to evacuate as a nearby damn is on the brink of bursting.

The funnel cloud over Johnston, Renfrewshire. Picture: Dave Morrison, Twitter

Emergency crews have warned of a threat to life should the reservoir flood the town of 6,500 people.