Extended Abstract (332K)P12.4
Characteristics of RUC vertical wind profiles near supercells
Paul Markowski, Penn State University, University Park, PA; and C. Hannon, J. Frame, E. Lancaster, A. Pietrycha, R. Edwards, and R. L. Thompson
Proximity vertical wind profiles obtained from Rapid Update Cycle (RUC) analyses were analyzed near approximately 450 supercells. Supercells were classified as nontornadic, weakly tornadic (associated with F0-F1 tornadoes), and strongly tornadic (associated with F2-F5 tornadoes). The differences between weakly tornadic and nontornadic supercells were relatively small. Wind profiles associated with strongly tornadic supercells differed significantly from weakly tornadic and nontornadic supercells in only the lowest 1 km, with the vertical wind shear being approximately 70% larger on average in this layer near strongly tornadic supercells compared to other supercells. The vertical profiles of streamwise vorticity and storm-relative helicity density also were significantly different between strongly tornadic supercell environments and weakly tornadic/nontornadic supercell environments. Curiously, storm-relative wind profiles were similar for all supercell classes, whereas ground-relative winds were roughly 5 m/s larger on average throughout the troposphere in strongly tornadic supercell environments compared to those associated with nontornadic supercells. Perhaps the substantially larger low-level shear in strongly tornadic supercells simply is due to the presence of larger gradient flow in the free atmosphere, which leads to larger boundary layer shear due to surface drag. Mean hodographs also were constructed for the three types of supercell classes. The hodographs had virtually indistinguishable appearances above 1 km. Given the wind profile similarities aloft, there is little wonder why operationally discriminating between tornadic and nontornadic environments has been so difficult. It is believed that it may be worthwhile to develop new technologies capable of better sampling the vertical wind profile in the lowest 1000 m, and with much improved horizontal resolution compared to the current wind profiler demonstration network. It also is believed that it would be fruitful for future numerical simulation studies to concentrate on the effects of hodograph differences in the lowest 1000 m on simulated supercells.
Poster Session 12, Tornado and Severe Storm Environments
Thursday, 15 August 2002, 3:00 PM-4:30 PM
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