Author : Daniel Ridge
Publisher : Unknown
Page : 68 pages
File Size : 44,5 Mb
Release : 1982
Category : Atmospheric pressure
ISBN : UOM:39015095143288
Diagnosis of the Comma Cloud of 10 April 1979 by Daniel Ridge Pdf
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 rather high time- and space-resolution rawinsonde data, plus 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 (QG) omega equation. An alternate partition of the GQ forcing function was tested. 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 m/s, and 500 mb height amplitudes around 30 m. They showed excellent time continuity in the 500 mb relative vorticity analyses. Both omega analyses showed 500 mb 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. Because of its ageostrophic sensitivity and computational ease, kinematic omega is more useful than QG omega for operational purposes. However, the two methods make an independent and complementary pair for research purposes.