Saturday evening, a gale of rare violence caused a sandstorm in Normandy, killing a surfer and injuring several other people. An event that no weather organization had foreseen. Explanations.
After a day marked by a heat torrid, a phenomenon of wind violent and sudden created panic on the Normandy beaches this Saturday evening around 8:30 p.m. While the coasts were crowded, a Gale unexpected generated a sandstorm on the seaside between Ouistreham and Deauville. The winds would have suddenly reached 75 to 100 km/h although no station weather report could not make a reliable measurement nearby. A kitesurfer lost his life in Villers-sur-Mer after being swept away by these stormy gusts and thrown against the facade of a restaurant. Five other people were seriously injured and 75 others suffered minor injuries.
Huge temperature contrast
If some first spoke of a tornado, it is in fact a different phenomenon. At the time of the rotation of the winds towards the north, responsible for the cooling, a strong instability was created at the meeting of the two masses of air: the superheated air on the ground linked to the heat wave (over 32°C in Normandy) and fresh air from the British Isles. Thunderstorms began to develop, and strong gusts of wind, called downbursts or gust fronts, were triggered ahead of the stormy downgrade. A tornado is a small whirlwind phenomenon (with winds in all directions therefore) under a thunderstorm, while a gust front is a fairly wide area of winds (sometimes several kilometres) that blow in the same direction before the arrival of the storm. ‘thunderstorm. A common phenomenon, but one whose power has no doubt been exacerbated by the huge contrast air masses present on Saturday. It is indeed common for this type of downburst to generate winds of 100 km/h in the space of a few seconds, but when the phenomenon occurs on a beach, it results in a real sandstorm. This phenomenon is almost reminiscent of haboobsthese sandstorms generated by thunderstorms in the desert regions of the United States and the Middle East.
An unpredictable event
Could the phenomenon have been anticipated? Predicting the arrival of storms and their exact consequences at a specific time is a very difficult exercise. It is possible to predict a risk of thunderstorms at the level of a department, which was the case on Saturday, with classic consequences such as wind, showers, hailbut forecasters cannot accurately define the intensity of this wind or predict its location within a few kilometers. Weather is not an exact science and still holds surprises.
However, we must always keep in mind that with a situation as exceptional as the heat of Saturday, the day of the peak in intensity of the heat wave in France, ultra-violent phenomena linked to thunderstorms can always be possible, in a very localized way.
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