W H AT IS THE HELM WIND?
Britain’s only named wind is what meteorologists call a ‘foehn’. This localised phenomenon occurs when a prevailing northeasterly roars over the down-slope of the North Pennines. Cooling air forms a cap of cloud along the crest known as the ‘Helm’ – so called because it resembles a helmet. As the cold air rushes down and rattles through the villages in the valley, it meets warmer air and rises again to form a tubular, rolling cloud called the ‘Helm Bar.’ The two parallel clouds are separated by clear skies.
William Marriott’s 1886 diagram of the Helm Wind.