The Brown Willy Effect

A meterological phenomenon named after the highest point in Cornwall, Brown Willy hill.

Showers form over the area of Bodmin Moor and travel downwind, causing heavy rain and in extreme circumstances, flash floods, as seen in Boscastle in August 2004.

As moist winds that blow in from the Atlantic Ocean and hit land in Cornwall, they are slowed by the effect of friction. Winds from the north and south coast of Cornwall's peninsula meet and create a convergence of winds near the central spine.The moisture in the wind is uplifted by the altitude of the moor and it condenses.

Once the showers have formed, they are driven by the prevailing wind. This causes a thin strip of showers along the length of the south-west peninsula of Cornwall. Places in the path of these showers can experience heavy downpours, whilst nearby locations are dry.