Dual-Doppler radar and cloud photogrammetry analysis of the 5 June 2009 Goshen County, Wyoming tornado during VORTEX2

On 5 June, 2009, a supercell over Goshen County, Wyoming gave rise to an EF 2 tornado that tracked for about 15km. This tornado was well observed with a number of in-situ and remote sensing instruments with the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2). Teams collected data well before tornado genesis all the way through the dissipation stage of the tornado. Relevant for this study, the Doppler on Wheels (DOW) 6 and 7 collected high-resolution dual-Doppler radar data at close range (4-20 km) well before tornado genesis up until just a few minutes before the tornado dissipated. Two photogrammetry teams documented the visual characteristics of the hook region from 20 minutes before tornadogenesis through the time that the funnel cloud dissipated.

This study presents results of the synthesis of the dual-Doppler and cloud photogrammetry data sets for the 5 June 2009 Goshen County, Wyoming tornado so as to better understand the relationship between the visual characteristics of the supercell hook region and funnel with the dual-Doppler radar data. For example, results will be shown where the temporal evolution of the funnel diameter is compared to the maximum vertical vorticity and circulation derived from the dual-Doppler radar data. It will also be shown that the radius of maximum wind (RMW) is relatively constant with height and is much larger than the funnel diameter near the ground. Near cloud base, however, the RMW is located near the tornado funnel. Analysis of angular momentum suggests that a tornado cyclone scale circulation was not present within this storm. Finally, during the time of tornadogenesis, cyclonic and anticyclonic lowered cloud bases were observed. Vortex line analysis suggests that these counter rotating circulations were, in part, created by the baroclinic generation of vorticity.