This Tuesday afternoon, 68 French departments are placed on yellow alert for storms by Météo France. This is the case for Vienne, Deux-Sèvres, Indre-et-Loire and Maine-et-Loire. Anjou is also on alert for rain and flooding this Tuesday. The day promises to be electric indeed with “unstable weather with showers and sometimes thunderstorms. Thunderstorms are frequent over a large northwest quarter up to the north of Aquitaine. indicates Météo France. The storms passed gradually until the evening.
What is a thunderstorm?
A thunderstorm is an atmospheric phenomenon characterized by lightning and thunder. It is always linked to the presence of a cumulonimbus type cloud, also called a thunderstorm cloud, and is often accompanied by a set of violent phenomena: gusts of wind, intense rain, sometimes hail, waterspout and tornado. The cumulonimbus is a cloud with a diameter of 5 to 10 km, very developed vertically, which can rise up to 16 km in altitude. At its summit, the cumulonimbus spreads out widely, which gives it its general anvil shape. A storm can always be dangerous at a given point, due to the power of the phenomena it produces. The storm is generally a short-lived phenomenon, lasting a few tens of minutes to a few hours. It can be isolated (storm near reliefs or caused by warming of the ground in summer) or organized in a line (called “squall line” by meteorologists). Under certain conditions, storms can regenerate, always in the same place, causing heavy precipitation for several hours, leading to catastrophic flooding.
Dangers
Lightning is the name given to a flash of lightning when it hits the ground. This intense electrical discharge can kill a man or an animal, burn a tree or cause fires. The intense rains that accompany thunderstorms can cause devastating flash floods. A cumulonimbus 1 km wide by 10 km high contains 1 million liters of water. Hail, precipitation made up of small pieces of ice, can devastate a vineyard or orchard in just a few minutes. The wind under a cumulonimbus blows in violent gusts up to around 140 km/h and changes direction frequently. More rarely, a very devastating whirlwind, the tornado, is created under the base of the cloud.
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