Published on July 28, 2025 at 8:40 p.m.
A powerful line of thunderstorms was to sweep a large portion of the American midwest on Monday, with strong winds, hail the size of a baseball bullet and a risk of tornadoes. This stormy system could evolve in derecho, a rare and formidable phenomenon.
A worrying system in training
The United States’s violent (Storm pre-pre-prediction or SPC) prediction prediction center (Storm prepressing the United States issued a clear warning this Monday: violent thunderstorms are expected this afternoon and this evening in a sector from southern Dakota to the south of Minnesota and north of Iowa.
These thunderstorms could generate destructive gusts reaching 120 to 145 km/h, equivalent to hurricane winds. Halm that can reach the size of a baseball ball could also fall in places. The warning also mentions the risk of seeing tornadoes appear.
A right?
According to meteorologist Patrick Duplessis, the system expected Monday presents the characteristics of a derecho potential.
What is a derecho? It is a type of convective meso-scale system, a vast grouping of stormy cells that are organized to form an imposing structure extending over a distance ranging from 5 to 500 kilometers. This phenomenon is distinguished by a very organized line of thunderstorms, often moving at high speed and causing damage by the wind over more than 400 km.
“To be described as a derecho, the winds must breathe generally above 90 km/h with several observations which exceed 120 km/h,” explains the meteorologist.
This system should be able to maintain its intensity along a stationary front separating two masses of air in opposition.
