Cold-season severe QLCS events over North AL : climatology, cloud, and boundary layer characteristics
Date of Award
Master of Science (MS)
Timothy A. Coleman
Lawrence D. Carey
Severe storms--Forecasting., Tornadoes., Boundary layer (Meteorology), Clouds.
Stratocumulus clouds, hypothesized to control boundary layer processes during cold season tornado events, are investigated. Associated observed boundary layer profiles of wind, low clouds (e.g., cloud base height, cloud fraction), water vapor, and boundary layer cloud depth near tornadogenesis events over northern Alabama and nearby areas of the Southeastern United States are presented. Observed stratocumulus cloud fraction for QLCS’s is 97%, and 83% for supercells. Furthermore, stratocumulus clouds first occurred an average of 200 and 90 minutes prior to tornadogenesis for QLCS’s and supercells respectively. Mean LCL heights for all QLCS cases were found to be 659 meters for QLCS, and 649 meters for supercell cases. Both the subcloud boundary layer and surface layer are often statically stable, unlike the dry adiabatic profile in classical cloud topped mixed layers. Thus, large bulk shear magnitudes of 14 and 18 m/s occur within the respective 0-500 m and 0-1 km layers.
Lisauckis, Christopher A., "Cold-season severe QLCS events over North AL : climatology, cloud, and boundary layer characteristics" (2018). Theses. 236.