9707815 Wicker While progress has been made over the last decade on understanding the dynamics of tornadoes and their parent storms, much is still unknown concerning the factors that cause tornado genesis and that control the intensity and longevity of any given tornado. In this research, the Principal Investigator will investigate how the large scale environment conditions (e.g. wind shear and buoyancy) control the intensity and longevity of tornadoes within supercell thunderstorms. This work builds on and is a logical follow-up to the Principal Investigator's previous research on the development of low-level rotation and tornado genesis within supercell thunderstorms. Two separate lines of research will be pursued. First, the Principal Investigator's current research will be extended down to the tornado scale in an effort to advance understanding of tornadogenesis. The previous work has resulted in refinements to the Rotunno and Klemp paradigm for origins of low-level rotation in supercells. The Principal Investigator s new theory demonstrates the dynamical role the inflow environment's near-surface horizontal vorticity has on mesocyclogenesis and can be used to predict the near-surface vertical wind shear profiles which are optimal for the generation of strong low-level mesocyclones within supercells. Extension of this work includes examining whether tornado-scale circulations are directly related to the mesocyclone circulation, as well as a study to understanding the role of shear and buoyancy in determining the spatial scales and magnitude of the low-level circulation and convergence needed for the generation of tornadoes. Second, an attempt will be made to explicitly model a particular supercell and tornado observed during the Verification of Origins of Rotation in Tornadoes Experiment. This part of the study will provide a much needed evaluation of the current state of cloud simulation realism and hopefully identif y specific aspects of convective scale modeling which need to be improved. Potential benefits from this research are many. Aside from increasing basic understanding of storm and tornado dynamics, the operational community will benefit from this research. Understanding which particular environmental profiles of wind shear, temperature and moisture that are most conducive for tornadoes will enable operational forecasters to pinpoint and focus on small regions where the conditions are favorble for the formation of intense tornadic storms. By more fully understanding the dynamics associated with these supercells and their tornadoes, improved severe weather forecasts and Doppler radar observations can then be used more effectively to forecast and detect tornado formation and warn the public. ***
