Are the harshs larger than before?

Ten centimeter giant hailstones in the moors or the palm size in the Puy-de-Dôme … Halt marked the deadly thunderstorms this Wednesday. Already on May 3, a violent hail storm had swept over Île-de-France, leaving behind damaged vehicles and significant stories. More than 61,000 vehicles were sent to the garage, with hailstones described as large as “tennis balls”.

In recent years, images of impressive hailstones, sometimes compared to tennis bullets or even melons, have multiplied on social networks and in the media. Following violent storm episodes, like that of Wednesday evening, a question comes back: did the harsh let’s become bigger than before?

Historically, hailstones are impressive. The biggest ever measured, with a diameter of 23.7 cm (the size of a volleyball ball), fell in February 2018 in Villa Carlos Paz, in Argentina, according to a study published in the Bulletin of the American Meteorological Society. “Barely 10 harshs over 15 centimeters have been observed in the past two decades,” said meteorologist Matthew R. Kumjian at CNN. In Europe, a 19 cm hack set a record in Azzano Decimo, Italy, on July 24, 2023. In France, the weight record was held by a 1.1 kg hail, fell to Viviers-lès-Lavaur in the Tarn, July 14, 2018, according to the Weatherpiece.

The effect of the media, but …

“History shows that so intense thunderstorms, called derechos, are not new. The most famous date of 1788. He had destroyed the land that produced cereals for bread … The production of bread having been strongly impacted, this caused the first riots of 1789, “recalls Serge Zaka, agroclimatologist and thunderstorm hunter.

However, the impression of an upsurge in giant hailstones is amplified by media coverage. “We don’t observe more hail. There is above all a media effect. Before, we didn’t necessarily have photos of the hailstones. Today, we publish everything very quickly so there is a recurrence effect, but the falls are not more numerous, ”explains Serge Zaka. However, he nuances: “There is still an element that is distinguished. On the ground, thunderstorms observe more giant hailstones than before. »»

Why do you harsh too big?

The formation of hailstones depends on specific atmospheric conditions. “The hail is formed in the columns of ascending air of thunderstorms,” ​​explains Serge Zaka. “The more the harsh remains in the cloud, the more it grows. In supercellular thunderstorms, like the derecho on Wednesday, hailstones can reach exceptional sizes by accumulating layers of ice.

Météo-France specifies, however, to 20 Minutes, that no database makes it possible to precisely quantify the evolution of this phenomenon, too local to be studied systematically.

Climate change in question?

The debate on the impact of climate change remains open. “Are the harshs bigger than before?” There are two answers. There is the scientific response with the IPCC report for example which explains that there is not necessarily any planned evolution. But when we read between the lines, these are conclusions made with the only current knowledge that we have. We still have a lot of gaps. Some items show an increase, others decrease and others stability. There is a lot of efforts to make in research, ”underlines Serge Zaka. “For the time being, we cannot yet confirm the impact of climate change in thunderstorms. But climatic events can indeed be more violent, ”adds the agroclimatologist. Warming, by increasing energy in the ocean atmosphere and temperature, promotes more intense thunderstorms, creating conditions conducive to larger hailstones.

The “giant hailstones” do not just fascinate, they cause major damage. “Giant hailstones are a danger for birds, wildlife and man. They destroy the wood of trees, vines, ”alerts to conclude Serge Zaka.