Severe thunderstorms developed in Montana during the evening of July 4th then moved into northwestern South Dakota during the early morning hours of July 5th. The storms intensified around daybreak on July 5th, as they encountered a more favorable environment for severe storms. The storms started out as supercells and then evolved into a derecho, with embedded supercells at times, as they moved through Hand and Hyde counties. The significant severe storms tracked southeast across central South Dakota, into southeastern South Dakota, and eventually into northern Iowa, while producing winds up to 91 mph and hail to the size of softballs in central South Dakota. This led to widespread damage to trees, grain bins, crops, and vehicles in the path of the storms.
A derecho is a widespread, long-lived wind storm that produces wind damage for at least 400 miles and is at least 60 miles wide. The wind gusts produced by a derecho must be at least 58 mph for most of its length, along with several 75 mph or great gusts.
An upper-level wave that moved through Montana caused the development of a few supercells that moved southeastward through South Dakota. As they moved into a more unstable and weakly sheared environment, they evolved into a derecho. The highest reported gusts were 99 mph at the SD DOT station near Howard, SD and 96 mph at Huron, SD airport. Multiple gusts well into the 70s and 80s were reported across the majority of southeastern SD, and into northwestern IA. There were dozens of reports of downed large trees, several overturned semi trucks, damages to houses and fences, and widespread crop damage.
Sources:
NWS Aberdeen Event Page: www.weather.gov/abr/July5th20...
NWS Sioux Falls Event Page: www.weather.gov/fsd/20220705-...
KELO-TV (Sky Camera in Sioux Falls) www.keloland.com/
21 июл 2022
