THE sky over Renfrewshire took a turn today (Thursday) as a rare weather phenomenon was spotted by people all over the area.

Locals have been posting pictures of the 'mini-tornado' as it swooped through Johnstone. 

But what is it? Here's a handy guide thanks to the experts at the Met Office and some of our readers' pictures.

The Gazette: Louise Rankin captured the cloud in Spateston Louise Rankin captured the cloud in Spateston  

What are funnel clouds?

A funnel cloud is a cone-shaped cloud which extends from the base of a cloud towards the ground without actually reaching the surface. In the UK they often look like thin dangling bits of rope, hanging from the cloud above. But in hotspots such as tornado alley in the USA, funnel clouds can sometimes be thicker and much more intense.

How do funnel clouds form?

A rotating column of wind draws in cloud droplets, making a region of intense low pressure visible. They are formed in the same way as a tornado building around this localised area of intensely low pressure and are typically associated with the formation of cumulonimbus thunderclouds.

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What weather is associated with funnel clouds?

Cumulonimbus clouds are almost always the host cloud from which tuba form, meaning that heavy rain, hail, thunder and lightning can all be expected. If a funnel cloud does make contact with the ground and produce a tornado, very strong winds can be expected in the immediate vicinity of the vortex potentially causing severe damage.

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What is the difference between a funnel cloud and a tornado?

Crucially, a funnel cloud does not reach the earth's surface, at the point it reaches land it becomes a tornado, or if it reaches a body of water it becomes a waterspout. In a typical year, the UK sees around 30-35 tornadoes each year, though it is very rare that are they strong enough to cause any significant damage.

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To see more of our readers' pictures, check out our Facebook page

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