gusts up to 140 km/h and hailstones close to 10 cm

The storm episode started with a first salvo on the night of June 24 to 25, with thunderstorms sometimes strong along the Aquitaine coast. Therefore, The electrical activity was very dense under these thunderstorms. Meanwhile, with more than 20,000 lightning detected, including 3000 lightning impacts (with maximum intensities close to 200 KA).

In addition, Sometimes violent gusts of wind swept away the west of the Pyrénées-Atlantiques, Landes and Gironde, with peaks until 135 km/h in Cazaux (33).

gusts up 140 km/h hailstones new

The radar animation below shows the evolution of this nocturnal stormy salve porremière. Furthermore, organized gusts up 140 km/h hailstones in a windy multicellular system.

In the second part of the afternoon of Wednesday, June 25, the first thunderstorms are initiated on the Pyrénées-Atlantiques, going up from Spain, to the plumb of altitude forcing. However, In nature supercellulairethese thunderstorms cause violent hailreaching 8 cm in diameter. Similarly, This supercell persisted until Gironde and in Lot-et-Garonne With destructive hail drops.

Further north. Meanwhile. at the edge of Berryother thunderstorms, there too of nature supercellulairehave managed to gusts up 140 km/h hailstones new hatch in an overheated environment (locally 40 ° C reports). Again, from Strong hailstorms fell in several municipalities.

Finally. a third sector quickly saw the stormy activity gusts up 140 km/h hailstones growing. on Pays de la Loirewhere very rainy thunderstorms et hacks have swept the region more anarchic.

Then, at the end of the afternoon, theconvective activity was generalized very quickly. A multitude de supercellules cohabited. generating violent hail (5 to 10 cm in diameter) and Intense wind gusts (up to more than 120 km/h recorded by anemometers).
Over the evening, stormy activity has organized Multisallular systemson which mesocyl were grafted. Wind gusts from 90 to 120 km/h and hail from 2 to 5 cm then dominated.

The 24-hour radar animation of the episode illustrates the chronology of the detailed events above. the water vapor animation highlights altitude forcing arriving from the west at the end of the gusts up 140 km/h hailstones new day:

The criteria of a derecho are indeed met (Learn more about derechos): Between the Gers/Tarn-et-Garonne limit. the German border, we note 58 Convective gusts> 90 km/h with a time distribution, Between 5.30 p.m. and 00:30 UTC. Several of these gusts. spaced gusts up 140 km/h hailstones new at least 64 km. have exceeded the bar of 120 km/h (surveys under anemometers or estimated depending on the damage), up to 135 km/h in Montbeugny. Consequently, the windy axis of Occitania in Lorraine gusts up 140 km/h hailstones meets the criteria of a right.

Note that other violent gusts have triggered in the passage of Supercellules. especially in Eure (126 km / h à Berna) or a multicellular windy system in the Oise (140 km/h in Bailleul-le-Soc).

The electrical activity observed during the day of June 25 is outstanding by its extent. In terms of lightning impacts (cloud-ground lightning), these are nearly 17,000 impacts which were noted, including more than 3,500 positive polarity. After a first phase made up of an abnormally high proportion of positive impacts. the negative impacts gradually took over over the evening.

The gusts up 140 km/h hailstones new most powerful lightning of the episode struck Deux-Sèvres, in the town of the Peyrattewith an intensity of 517 The. An intensity of this order is remarkable. 20 times higher than the average of lightning impacts observed also during gusts up 140 km/h hailstones this day.

We distinguish on the impact map The imprint of Derecho from Occitania to the German borders.

And cut-off Located on Portugal went back on June 25 in the direction of northern France. in the form of a very dynamic thalweg. In his transit. he piloted a Jet -Streak evolving according to an Aquitaine – Benelux axis. generating a right input configuration of well -diffluent jet from the Pyrenees to the Belgian borders (see image at the top left).

At the same time. on the ground, the barometric marsh has taken on a depressional character gusts up 140 km/h hailstones new with the digging of a surface thalweg between Occitanie, Center and Normandy (see image at the top right). The convergence of associated low layers has contributed to forcing convection in an environment marked by an intense daytise. (35 to 40 ° gusts up 140 km/h hailstones C noted). moderately rich in humidity (neighboring dew 16 ° C. more in isolation) and therefore strongly unstable (mucape from 1500 to 2500 d/kg, mui up to -8 k – Cf image below).

Conditions have therefore become favorable from the afternoon to the development of violent supercellules (Cf. Image at the bottom right) with high supercellular indices.

Subsequently. the air mass profiles and the shears in place favored the organization of windy multicellular thunderstorms, allowing the implementation of a city -national event (Derecho).

Find below some photos taken during this stormy episode: