A week to say the least… hectic. After an exceptional heat peak for the season, the sky will darken on Tuesday evening, and thunderstorms, more or less violent, are expected in the four corners of France.
As such, Météo France warns of potentially violent episodes, “over a large part of the country, in particular from the Massif Central to Burgundy”, on Tuesday evening, and in the north of Languedoc and in the Rhône valley for the Wednesday day.
However, nuance Paul Marquis, forecaster at E-Météo Service, it is not a Mediterranean episode strictly speaking.
“We tend to generalize everything that is stormy, but a Mediterranean episode will last several days, between 24 and 72 hours, and there, that is not the case”, explains the expert to Planet.
But it is indeed, according to him, a “stormy episode of Mediterranean origin”. The phenomenon is due in particular to the passage of the former hurricane Danielle, which has become a banal depression, off our coasts, causing an unstable air influx.
“From Tuesday evening, we expect stormy showers, especially in Hérault and Gard.
The night from Tuesday to Wednesday, the stormy system is likely to rise in the Bouches-du-Rhône and the PACA region”, specifies Paul Marquis.
Forecasts confirmed by Patrick Marlière, for Agate Météo:
But it is probably Wednesday that the storms are likely to be the most violent.
“Wednesday, during the day, there is a risk of very rainy thunderstorms, in the Ardèche, the Drôme, the Vaucluse, and more widely around the Rhône valley, with also a main risk in the Hérault and the Gard. The PACA region should remain on the sidelines of these disturbances”, explains Paul Marquis.
Heavy downpours are also to be expected locally.
“This Wednesday, September 14, more violent storms will be able to give 70 to 90 mm of precipitation in a few hours, notes for his part Patrick Marlière. Gard and Hérault, like a large part of our country, are currently on yellow level weather vigilance due to the risk of storms. A change to orange level is not excluded for these two departments, and is even very likely”.
But that’s not all. The stormy episode that is about to hit France could affect other regions, to a lesser extent.
Where they will be the most violent, thunderstorms could also be accompanied by extreme phenomena, specifies the forecaster. “There is a risk of hail, with hailstones that can exceed two to three centimeters, around the Rhône, Wednesday afternoon. And we are also expecting heavy urban runoff, with a rise in water levels for a few hours”.
But the expert relativizes: there is, for the moment, no question of a risk of flooding, and the phenomenon should only last a few hours. “The expected levels are not catastrophic”, summarizes Paul Marquis.
Tuesday afternoon, Météo France placed 84 departments of France on yellow vigilance in the face of the risk of violent storms. But the situation could well change by Wednesday afternoon. Especially because of the sand of the Sahara.
“There is indeed some sandy dust in the atmosphere, and this dust tends to make the electrical activity higher than normal. There should therefore be, in the regions concerned, more lightning than normal”, specifies Paul Marquis.
However, the return to calm (and cold) is expected soon enough. “The disturbances will fade from Wednesday evening, from 9 p.m., with a much calmer Thursday, before the cold weather arrives for this weekend”, describes the expert from E-Météo Service.
We have to face the facts: autumn is fast approaching…