By Mélissa Gautier
Posted on 6/18/2021 at 5:52 p.m.
Updated 06/18/2021 at 8:34 p.m.
Violent thunderstorms, heavy rainfall … Forecasters report an “exceptional phenomenon” after the bad weather on Thursday
A real water suppressant. This is what fell on Thursday evening in the New Aquitaine region and more particularly in the Gironde. At the end of the afternoon, then around 10 p.m., very violent thunderstorms hit the department following a South / North axis. The sector between Sauternes, Langon, the east of the Bordeaux metropolis, the Blayais, then going up towards Charente-Maritime, Saintes and Royan was severely watered for several hours. After a first stormy episode the day before, the soggy soils could not absorb the heavy rainfall, causing significant flooding, especially on the right bank of Bordeaux.
More than 100 mm of rain
This Friday, Météo France reported “record rains, an exceptional phenomenon in terms of quantity for the month of June”. In Saint-Émilion, 31 mm of rain were recorded during the stormy episode, 38 mm on the Bordeaux side and 82 mm in Mortagne-sur-Gironde, in Charente-Maritime. In some municipalities, more than 100 mm of rain sometimes fell in six hours. But difficult to be more precise because of the lack of rainfall records in the most affected areas. Some data, reconstructed using radar, reported 127 mm of rain in Saint-Germain-du-Puch, near Libourne, for example.
One thing is certain, “we have just experienced a ten-year event, even one hundred years in places”, that is to say which occurs once every ten or a hundred years, specifies Thomas Beauquesne, forecaster at Météo France in Mérignac ( 33). By comparison, it rains on average 43 mm of rain in June in Saint-Émilion. In the municipalities where the accumulations were the most important, it rained in six hours almost double the average precipitation usually recorded in two months in the summer.
Electricity activity was also particularly strong in New Aquitaine. In Gironde, nearly 650 lightning bolts were recorded by Keraunos, a far cry from the 1,335 lightning bolts in the Tarn, in Occitanie, the region most affected by bad weather. The Landes, the Dordogne and the Lot-et-Garonne were also affected, but to a lesser extent, “because there was no accumulation of thunderstorms,” notes Thomas Beauquesne.
Heavy rain this weekend
According to Météo France, a new stormy episode should affect the region this Friday evening, especially in the north of the Gironde and in the Médoc. Significant precipitation is still expected with accumulations of up to 40 mm of rain sometimes accompanied by hail.
And the weekend does not look much better with again violent storms announced this time Saturday afternoon over the Basque Country and the Landes. They will then go north before taking the same axis as this Thursday. “Very heavy rains are still announced on Saturday evening. And that will add a lot of water while many roads are still flooded ”, fears the forecaster from Météo France. Orange vigilance could also be triggered during the day.