Seminar coordinator: Asst. Prof. Ryan Sriver (rsriver at illinois.edu)
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Kevin Van Leer, Graduate Student, DAS, University of Illinois
Room 112 of the Transportation Building
Department of Atmospheric Sciences
The relationship between storm mergers and tornado formation can result in local conditions more favorable for rapid intensification of vertical vorticity at the surface than found in the surrounding environment. Following the work of Lemon 1976 and Lee et al 2006, this study uses high-resolution WRF simulations to simulate and understand the significance of storm mergers in subsequent intensification of the parent rotating updraft (mesocyclone) and tornadic vortex in the 22 May 2011 Joplin, MO case. This case was noted for the rapid evolution of the storm from tornado formation (tornadogenesis) to peak intensity in relation to the merging of cells in the rear-flank region of the parent storm.
In an effort to identify the importance of the mergers in the tornadogenesis process, case-study WRF simulations are used to reproduce behavior observed in the event. An in-depth qualitative and quantitative analysis of the relationships between internal storm dynamical processes, such as precipitation loading and increased surface convergence, is performed. Three-dimensional visualization is utilized to identify spatial and temporal relationships between storm-scale processes. Sensitivity tests, including the artificial removal or alteration of the merging cells in the model, modify the evolution of the storm, allowing the quantification of the mergers’ effects. This study pursued a goal of identifying storm scale processes resulting from storm mergers that enhance, weaken or otherwise modulate tornado development in supercell storms.
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