1. ITV Report

Rare 'Split Rainbow' spotted over Hull

Split Rainbow taken from Brough looking towards Hull East Yorkshire Photo: PHILIP JACKSON

Philip Jackson took this photo in July 2015 and asked me if I knew how the split rainbow is formed.

This phenomenon, also known as a 'twinned primary bow' is caused when water droplets of two different sizes fall from a rain cloud.

Small rain drops fall in a spherical shape but larger droplets fall through the air shaped more like almonds,

Sunlight passing through the smaller spherical droplets of rain form the primary rainbow whereas sunlight passes through the almond shaped drops in such a way as to form a split rainbow originating from the same source as the primary bow.

This is not to be confused with a "secondary" rainbow which is formed by rays of light that are reflected inside the individual raindrops twice. This is parallel to the primary rainbow but does not touch it unlike this rare twinned rainbow over Brough.