Diagnosis of the Comma Cloud of 10 April 1979.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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On 10 April 1979 a comma cloud developed in association with a severe storm outbreak in Texas and Oklahoma during the AVE-SESAME 1 regional-scale experiment. With high time- and space-resolution rawinsonde data, plue GOES, radar, and surface data, a diagnosis was made of the structure and evolution of the disturbance which spawned the clouds. Vertical motion was computed by the kinematic method and from the quasi-geostrophic omega equation. An alternate partition of the quasi-geostrophic forcing function was tested. Patterns of Richardson number R sub i were compared to the circulation and weather. Five mesoscale waves in the mid- to high-troposphere strongly affected the weather patterns on 10 April 1979. These disturbances had wavelengths from 500 to 800 km, phase speeds of 20 to 33 ms, and 500mb height amplitudes around 30m. They showed excellent time continuity in the 500mb relative vorticity analyses. Both omega analyses showed 500mb rising motion in eastern New Mexico six hours before a subsynoptic surface low and tornadic storms developed just to the east in Texas. Kinematic omegas indicated subsidence over the Texas Coastal plain for six hours in the afternoon, evidently associated with maintenance of a surface pressure ridge and an intense low-level inversion which inhibited convection in that area.