Brown Willy effect is a particular example of a meteorological phenomenon known as peninsular convergence , which sometimes occurs in the south-west of Great Britain . It leads to heavy showers developing over the high ground of Bodmin Moor in Cornwall , which then often travel a considerable distance downwind of their place of origin . The effect is named after the hill , Brown Willy , the highest point on the moor and in Cornwall as a whole . It is thought that the Boscastle flood of 2004 was caused by a particularly extreme example
Boscastle flood of 2004
Boscastle flood of 2004
Brown Willy effect