Description

The Brown Willy effect is a particular meteorological phenomenon know also as peninsular convergence, which sometimes occurs in the south-west of England. It leads to heavy showers developing over high ground of Bodmin Moor in Cornwall, which then often travel a considerable distance downwind of their place of origin affecting flight operations at airports in their path.

The effect is named after the hill, Brown Willy, the highest point on Bodmin Moor and in Cornwall as a whole.

Causal factors

Cornwall lies in the path of prevailing mild, moist westerly or south-westerlly winds that blow in from the Atlantic Ocean. As these hit land, they are slowed by the effect of friction. Winds near the south coast tend to be diverted to a more northerly direction (backed), this creates a convergence zone near the central/northern spine of the peninsular, leading to uplift and condensation of the moist air.