Introduction / Synoptic Environment
Derecho Criteria (Johns and Hirt 1987)
Major axis length of at least 400 km
Reports must show a pattern of chronological progression
Must be at least 3 reports of F1 damage or convective gusts of 65 kt or greater
No more than 3 hours can elapse between successive events
Progressive Derecho
A short curved squall line oriented nearly perpendicular to the mean wind direction with a bulge in the general direction of the mean flow
From Johns and Hirt (1987)
