Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xxiv, 163 p. : ill. (some col.). + QuickTime and media files. Includes video files in the mpeg and wmv formats. Vita. Includes abstract. Includes bibliographical references (p. 126-136).

Thesis (M.S.)--Ball State University, 2009. / Title from PDF t.p. (viewed on Dec. 14, 2009). Includes bibliographical references (p. 95-98).

Published: December 2002. Accession No.: 118821; File size: 277.3kb; Report No.: 38072. Offprint: Bulletin of the American Meteorological Society. Vol 83 (12).

Thesis (M.F.A), Design--University of Central Oklahoma, 2009. / Includes bibliographical references (leaves 96-108).

Recent observations and numerical simulations have significantly improved our understanding of tornadic storms. However, our knowledge of tornado-genesis remains rudimentary. Necessary atmospheric conditions favoring the formation of tornadoes in supercell storms are known, but sufficient conditions remain elusive. The underlying reason is that the processes involved in environment-storm and storm-tornado interactions are not fully understood, as numerical models in the past lacked sufficient resolution to resolve these interactions satisfactorily. In this thesis, an attempt is made to fill this gap by performing a multi-grid high resolution simulation of a supercell storm spawning a tornado-like vortex. Four grids, with grid sizes of 600 m, 200 m, 70 m, and 30 m, are used to allow explicit simulation of storm-tornado interactions. Diagnostic analysis of the modeling results allows an investigation of the origin of rotation at both the storm scale and the tornado scale. / The simulation results showed that the origin of vertical rotation at storm scale during the early stage of storm development is due to tilting of the horizontal vorticity in the environment. This so called mesocyclone then further strengthens by the mechanism of stretching and Dynamic Pipe Effect and descends downwards. During the time of mesocyclone intensification, incipient surface vertical vortices form along the outflow boundary created by the rear flank downdraft due to the process of horizontal shear instability. / One of the surface vortices experiences an initial exponential growth in its vorticity by interacting with the descending mesocyclone and merging with multiple smaller satellite vortices. The tornado-like vortex (TLV) which forms has a maximum horizontal wind of 103 m s-1 and a minimum central pressure of 927 hPa. Vorticity budgets of the mesocyclone and the TLV are computed to assess quantitatively the importance of various processes for rotation. / Sensitivity experiments were also performed to determine the effect of varying the environmental conditions on the mesocyclone and surface vorticity. It was found that as the low-level vertical shear of the environmental wind increases, the mesocyclone intensifies and favors the intensification of near surface vorticity. The presence of drier layers in the upper and middle troposphere eventually produces a weaker mesocyclone and weaker outflow boundaries. On the other hand, inclusion of the ice phase processes produces a stronger mesocyclone and more intense outflow boundaries to enhance the intensification of near surface vorticity.

An idea often held in the mainstream society in the United States is a phenomenon of common occurrence between tornadoes and mobile home residences. While such perceptions could be learned from media presentations of tornadic events, a spatial investigation into such events in the Southeastern United States presents other possibilities. A statistical analysis of correlation is used to investigate the nature of relationship of coincidence between the two variables. Counties with relatively high densities of each variable are used for a case study of common geofactors at the micro scale. Results of this research suggest that a regional correlation between the two variables is non-existent. Results of the case study suggest that, while some similarities in geofactors existent between counties with high densities of each variable, no definitive conclusion can be reached with the data used in this study. / Department of Geography

No description available.

Tornado research conducted across the southeastern United States suggests two peak tornado maxima. However, few studies have distinguished between the thermodynamic and shear environments between cool-season and warm-season tornadoes. Incorporating 100 mb mixed layer parcels, mean thermodynamic and shear parameters for non-significant (F0?F1) and significant (F2?F5) tornado environments were calculated. Cool-season tornado environments were characterized by relatively low amounts of instability and high shear. On the other hand, warm-season tornado events were characterized by higher amounts of instability and generally less shear. The Energy Helicity Index (EHI) remained nearly constant suggesting a balance of instability and shear between the tested seasons. During the cool-season, an increase in instability appears to distinguish between tornado strengths. Yet, an increase in shear during the warm-season may be indicative of significant tornado environments.

Many studies have suggested that the tornado database is biased by the concentration of human observers. Some studies have shown a possible 66% decrease in tornado reporting can be directly attributed to population density. This study examines whether or not such biases exist throughout the United States. Population data are compared to the historical tornado database in order to better understand the relationship(s) between each variable. Various statistical and spatial techniques are implemented in order to better identify relationships. As expected, weak (F0-F1) tornadoes show a correlation to both population patterns and travel routes. However, not all regions of the United States share the same relationships during the study period. Therefore, any meaningful adjustment to the tornado climatology cannot be made because of the variation in both spatial and temporal changes.

Thesis (M.S.)--Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.