The traditional criteria that distinguish a derecho from a severe thunderstorm are sustained winds of 58 mi/h (50 kt or 93 km/h) during the storm (as opposed to gusts), high or rapidly increasing forward speed, and geographic extent (typically 250 nautical miles [280 mi or 460 km] long).[1] In addition, they have a distinctive appearance on radar (bow echo); several unique features, such as the rear inflow notch and bookend vortex, and usually manifest two or more downbursts.
Quote selectie