The Department of Geography Colloquium Series presents Dr. Yvette Richardson on “Our Current Understanding of Tornadic Storms” on Friday, March 13, at noon in Clippinger Labs 119.
Richardson is an Associate Professor of Meteorology at Pennsylvania State University.
Abstract: Decades of observational, numerical, and theoretical studies have revealed many of the essential processes governing tornado formation and eventual demise. Perhaps our clearest understanding regards the development of the parent supercell thunderstorm, characterized by a rotating updraft at midlevels in the atmosphere. This midlevel rotation is found to result from the reorientation of horizontal environmental vortex lines by the storm’s updraft as the storm develops in a region where winds change direction and/or speed dramatically with height. However, the development of rotation very near the surface, as required for tornado formation, relies on the reorientation of vorticity generated within storm-induced gradients of buoyancy, and this reorientation must be accomplished by a downdraft. The final step in tornado formation involves contracting this rotating air to a small radius beneath an updraft, resulting in tornado-strength tangential winds as angular momentum is conserved. The climatological dependency of tornado formation on environmental parameters such as the level of cloud base and the change in environmental winds over the lowest kilometer will be explained in the context of our theoretical understanding. Observations of tornado formation and demise from a recent field project, the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2), will be highlighted.
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