Five powerful supercell storms swept across the Czech Republic on Monday, an unusual phenomenon for September. One particularly remarkable storm traveled over 200 kilometers from the Klatovy region all the way to Brno. These intense weather systems brought hailstones measuring up to four centimeters in diameter and powerful wind gusts.
Monday’s cold front passage was surrounded by uncertainty regarding storm development. Despite ideal atmospheric conditions for the formation of powerful rotating storms—known as supercells—a dry layer in the upper atmosphere threatened to prevent stronger convection from developing. Nevertheless, several exceptionally strong supercells did materialize across the Czech Republic, with the Czech Hydrometeorological Institute (ČHMÚ) issuing warnings for each observed dangerous phenomenon.
What made these storms particularly unusual for this time of year was their longevity. According to ČHMÚ measurements, some long-lasting supercells traveled several dozen kilometers. The record-setter was a storm that journeyed from the Klatovy region to Brno, covering approximately 220 kilometers during its lifespan.
The storms brought multiple hazardous conditions. Around Choceň and Vysoké Mýto, hailstones reaching 4 centimeters in size pelted the area. The same left-turning supercell (rotating counterclockwise) likely produced a downburst—a column of cold air descending rapidly with powerful wind gusts. In Ústí nad Orlicí, wind speeds of 73 km/h were recorded, though localized gusts likely reached even higher velocities.
Weather forecasts indicate calmer conditions in the coming days after an extended period of instability. Cloud cover and precipitation are expected to decrease toward the end of the week, with temperatures gradually rising to summer-like values.