While the lightning illuminated Hampshire sky, this was another meteorological phenomenon that attracted people’s attention.

How thunderstorms when they moved they brought with them an ominous cloud formation that saw people knocking them out smartphones and recording an amazing celestial sight.

What has been witnessed is what is known as a ‘shelf cloud’ – a type of ‘arc cloud’, but what are they and why do they occur?

Lightning over the Bitter Triangle.

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What is a cloud shelf?

In accordance with Metaburoarcus clouds are “spectacular low, long, thin clouds associated with severe thunderstorms”.

There are two types of arcus clouds – shelf and roll clouds.

Usually, the shelf clouds that appear at the leading edge of a storm are not rain clouds themselves, but heavy downpours usually follow cumulus clouds.

They form when cold air descending from cumulus clouds spreads rapidly over the ground and pushes warm, moist air upward, which then condenses in these long cloud “shelves.”

Are shelf clouds dangerous?

Because shelf clouds are usually attached to the base of a cumulonimbus cloud (although they can form from any type of convective cloud), they are usually associated with strong gusty winds, heavy rain or hail, and thunder and lightning.

In certain conditions, a very low shelf cloud can indicate the approach of potentially strong and sudden but prolonged wind gusts known as squalls.


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