Oklahoma Thunderstorms on 29–30 April 1970. Part I: Morphology of a Tornadic Storm

Abstract Data collected at the National Severe Storms Laboratory reveal the mesogamma-scale (2.5–25 km) features of two severe thunderstorms that struck Oklahoma City within 1 h of each other. This paper discusses the surface, upper air and radar data obtained during the passage of the first tornadic storm (F). Companion papers deal with the second storm (G) which exhibited twin tornado cyclones (Parts II and III), and another discusses the environmental conditions which led to the demise of an earlier hailstorm (Part IV). At the surface, the tornadic supercell storms were characterized by mesocyclonic sinks beneath the main updrafts with convergence values greater than 2 × 10−3 s−1 and vorticity about half as large. Lowest pressures preceded the mesocyclones by several kilometers and are believed to be dissociated from the wind centers because of the storms' rapid translational speeds (25–32 m s−1). Highest pressures were found near the rainy cores but not coincident. Middle-tropospheric air descended on...