Wednesday, 5 November 2014
Capitol Ballroom AB (Madison Concourse Hotel)
Thirty years ago, on June 7 8, 1984, a powerful storm system moved through the upper Mid-West producing numerous reports of hail, wind, and tornadoes. In all there were 42 reported tornadoes in 11 hours, the strongest being an F-5 that struck the town of Barneveld, Wisconsin. This one tornado destroyed a majority of the village of Barneveld causing 9 fatalities in the process. This tornado and 6 other tornadoes that occurred in the southern Wisconsin during this outbreak are the primary focus of this study. With any major tornado outbreak, the synoptic-scale conditions are present for severe local storm development capable of producing tornadoes over a large geographic area. Thus, the occurrence of meso- to micro-scale features (e.g., supercells or tornadoes) are most influenced by meso- to micro-scale conditions. Often overlooked at these scales are preexisting atmospheric boundaries established by land-surface properties. Changes in soil moisture, land cover, soil type, and topography are just a sample of the surface conditions that can affect both latent and sensible heat fluxes as well as low-level wind fields. These changes in the atmosphere due to surface properties can enhance the overlying synoptic-scale conditions leading to the development and/or strengthening of severe local storms leading to possible tornadogenesis. One particular aspect of the landscape in southern Wisconsin is the topographic changes. Across this portion of the state the landscape changes dramatically from the western driftless region, (i.e., unglaciated) to the central region where the extent of the Green Bay Lobes terminal moraine was left. Which also left behind geomorphologic features such as drumlins, eskers, and moraines in the eastern region. This past glacial history gives southern Wisconsin its topographical relief today. The 7 tornadoes that occurred during this outbreak in southern Wisconsin traversed this changing landscape. This study focuses on the role that changing topography, and other land-surface properties, may have played in the development of these tornadoes.
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