BBC South weather presenter Alexis Green said: “It’s shelf cloud — a type of arcus cloud. They form on the leading edge of thunderstorms. Cool, sinking air from a storm cloud’s downdraught spreads out across the land surface, with the leading edge called a gust front. This outflow cuts under warm air being drawn into the storm’s updraft. As the lower and cooler air lifts the warm moist air, its water condenses, creating the shelf cloud.”
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