What is the brouillarta, this wind that causes the temperature to drop by 20°C in one hour?

This Monday, the southwest of France registered the highest temperatures in France, more than 40 ° C. However, it is also there that the thermostat was at its lowest in the early evening. How to explain it? This sudden drop in temperature is due to a well-identified meteorological phenomenon: the galern. Also called “brouillarta” in the Basque Country or “enbata” towards Hendaye. Focus on this gust of wind that suddenly ended the heat wave.

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Residents of the Basque and Landes coasts know it well. The fog, “fading the Artha, named after the breakwater at the entrance to the bay” of Saint-Jean-de-Luz, the newspaper explains South West, is often greeted with joy. Just like last June, this cold and wet wind from the northwest that blew over the region last night caused the temperature to drop 15 to 20 degrees in just an hour.

When the galerne is announced, we pack the umbrellas and sun loungers, leave the beach and return to the port. Because the winds that accompany the brouillarta are not trivial. They can indeed reach speeds of up to 100 km/h. In April 1878, this wind so feared by sailors led to the death of 322 of them, drowning in the Cantabrian Bay in northern Spain. Yesterday, the maritime prefecture of Gironde warned boaters about this phenomenon in the south of the Bay of Biscay, “STRONGLY advise against practicing water sports along the South Atlantic coast, from 5 pm.”

What are the conditions for the occurrence of this meteorological phenomenon?

The gallery needs very specific conditions to form. Indeed, it only occurs when the warm weather (more than 30 degrees) has come for more than two days in a row and there is a temperature difference of at least ten degrees between the air and the ocean, explains Francis Morisset, forecaster at Météo France Biarritz and fog specialist for our colleague South West,

“The warm air mass collapses, creating a downward airflow that attracts the cool air to the ocean. Within a few minutes, the atmospheric pressure can panic. The greater the variation, the more pronounced the brouillarta will be,” the daily specifies.

The sudden change in temperature and the increase in humidity are due to the fact that the air coming from the Atlantic Ocean replaces the hot and dry air of the country. Good long-term news in the fight against the fires currently ravaging the Gironde, the site recalls future. However, the strong winds that swept the coast at the end of the day, this Monday 18 July, fanned the flames, further complicating the work of the firefighters.

In France, the meteorological phenomenon is also present on the coasts of Breton and Vendée. Further down, northern Spain and Portugal are also familiar with these strong winds. It mainly occurs between the months of May and October, usually at the end of the day between 5 and 9 pm.

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