CJAMY. Camille Gaubert’s column is broadcast daily on “C Jamy”, hosted by Jamy Gourmaud from Monday to Friday at 5 pm, in France 5.
The mistral, how much they love it, how much they fear it, is sometimes a violent wind. At the origins of these sometimes devastating blows, the narrow passage of the Rhone Valley that gives birth to it.
Hit the mistral
The mistral is associated with dry and sunny weather, but is often afraid of its blows. We must say that it is a strong wind: it orbits at an average speed of 50 km / h, with gusts greater than 100 km / h. It is well above winds reaching 30 km / h or moderate winds not exceeding 40 km / h.
Like all winds, the mistral is born from differences in temperature and pressure. Warm air, which is lighter than cold, creates an area of low pressure called depression. On the other hand, cold air creates an area of high pressure, called an anticyclone. However, the air always goes to a place where there is less pressure (like when a tire punctures, air comes out). It is a schematic wind: the air that leaves the anticyclone and joins the depression.
Acceleration created by the mistral
In the case of the mistral, it all starts with the Bay of Biscay anticyclone and the Gulf of Genoa depression. There is a third actor between the two: the mass of cold air coming from the polar regions is directed by an anticyclone. It then rushes into the Rhône valley, between the central massif and the Alps, towards the depression. This passage is so narrow that all the air molecules collide with each other and the air accelerates. This phenomenon is called the “Venturi effect”, named after the 18th century Italian physicist who discovered it. That’s why the mistral can blow so hard! At the end of 2019, Orange raged for 14 days in a row at more than 80 km / h, even with gusts of 120 km / h! It is equivalent to hurricane winds.
The mistral was created in the Rhone Valley, between the anticyclone (A) of the Bay of Biscay and the depression (D) of the Gulf of Genoa. Credit: TV France 5
So much so that some say the mistral can drive you crazy, even if it proves nothing. In contrast, wind can generally cause pain to people who are already prone to migraines and who are naturally sensitive to pressure changes. AND “climate changes“as heat, cold or “strong wind “ can indeed trigger an attack, according to Inserm. In the case of Mistral, “the action of the wind stimulates foci on the neck and changes the temperature of the skin, causing pain“, explained for Figaro Ship Dr. Marc Schwob, neuropsychiatrist and president of the France Migraine Association.
Decisively, the mistral may be invisible, but he does not allow himself to be forgotten.