Extended Abstract (356K)16.4
Hodograph variability within analytically modeled baroclinic waves
Peter C. Banacos, NOAA/NWS/SPC, Norman, OK; and H. B. Bluestein
Knowledge of the local vertical wind shear is important in determining convective storm type and characteristics of banded precipitation areas within parent mid-latitude cyclones. A simple analytic model of pressure systems developed by Fred Sanders in 1971 is used to examine the modulation of geostrophic and ageostrophic hodographs by parameters controlling the model's baroclinic wave structure. The results are compared with a climatological analysis of hodographs near mid-latitude cyclones and anticyclones developed by the authors (Monthly Weather Review, 2002) based on 38 years of operational rawinsonde data, to investigate how well the model is able to replicate various aspects of these mean wind profiles.
We focus on the northeastern, eastern, and southeastern sectors of cyclones, because that is where convective storms tend to occur most frequently. The quasi-geostrophic contribution to the hodograph in these areas is shown to be strongly modulated by the system wavelength, the meridional temperature gradient, the phase lag between the height and temperature fields, and the magnitude of perturbation temperature and height. We show how the shapes and lengths of the hodographs depend on the synoptic-scale parameters that describe the baroclinic wave. Hodograph shapes observed in nature, but not realized by the model, will be noted. The relative contributions of geostrophic and ageostrophic shear are discussed. The actual local storm environment vertical shear is composed of this background wind structure produced on the synoptic-scale, and modified locally by shorter-term mesoscale and/or convective-scale processes, and frictional effects.
Session 16, Tornado and Severe Storms Environments
Friday, 16 August 2002, 8:00 AM-9:59 AM
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