Brown Willy effect

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.

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 peninsula, leading to uplift and condensation of the moisture borne by them.

Converging sea breeze fronts from the north and south coasts of Cornwall can lead to very rapid convection developing over the moor, which may result in very heavy showers or thunderstorms.

This causes a thin line of showers to occur along the length of the south-west peninsula, all originating from the Bodmin Moor area, which are often intensified further by the downwind high ground of Dartmoor and the Blackdown Hills.

Places directly in the path of these showers suffer a series of heavy downpours, whilst nearby locations remain dry.