Galerna
A sudden, violent northwesterly squall occurring over the Bay of Biscay, with abrupt temperature drops and hurricane-force winds.
The galerna is an abrupt and potentially dangerous weather phenomenon characteristic of the Spanish Cantabrian coast (Basque Country, Cantabria, Asturias). It consists of a sudden change in atmospheric conditions: within minutes, a sunny, calm day transforms into a storm with northwesterly winds of 70–120 km/h, a temperature drop of 10–15 °C, heavy seas, and intense showers.
The formation mechanism involves the interaction between a warm continental air mass (which generates calm and heat along the coast) and a cold front advancing from the Atlantic. The thermal contrast between warm surface air and incoming cold air generates a violent convergence line. The Cantabrian Mountain range amplifies the effect by channelling and accelerating the maritime air penetrating inland. The "classic" galerna occurs in summer (June–September), when the land-sea thermal contrast is greatest.
Historically, galernas have caused numerous maritime tragedies in the Bay of Biscay. The "Galerna del Sábado de Gloria" on 12 April 1878 sank hundreds of vessels and killed over 300 Basque and Cantabrian fishermen. Today, AEMET issues specific galerna warnings, but prediction remains difficult due to the phenomenon's speed and localised nature. For sailors and swimmers along the Cantabrian coast, the galerna is a risk requiring constant monitoring of weather forecasts during summer.