1.4 The Dodge City Tornadoes on 24 May 2016: Damage Survey, Photogrammetric Analysis Combine with Mobile Polarimetric Radar Data

Monday, 22 October 2018: 9:45 AM
Pinnacle room (Stoweflake Mountain Resort )
Roger, M. Wakimoto, Univ. of California, Los Angeles, CA; and Z. B. Weinhoff, H. B. Bluestein, and D. W. Reif

On 24 May 2016, a series of supercells formed over western Kansas and produced a number of tornadoes. One cell west of Dodge City was intercepted by the mobile rapid-scanning X-band polarimetric Doppler radar (RaXPol) as it produced several tornadoes while the visual characteristics of the condensation funnel and debris cloud were recorded by a high-resolution camera. The views of the tornado and the lofted debris were largely unimpeded by precipitation and poor visibility. The tornadoes moved slowly which resulted in continuous volume scans of radar data being collected over an extended period. This is the first time that detailed polarimetric measurements were quantitatively combined with photographs of a tornado and an evolving debris cloud.

The early stages of the tornado were characterized by a column of low cross correlation coefficient (RHOhv) and negative differential reflectivity (ZDR). The latter suggests common debris alignment within the tornado. A consistent observation throughout the data collection period were two pockets of low RHOhv at a radius beyond the funnel at low levels and collocated with an annulus of high radar reflectivity. These pockets are believed to be areas of high debris loading that have been documented in simulations of lofted debris. As the debris cloud grew in width and enveloped the funnel cloud, the polarimetric profiles underwent a dramatic change. The minimum of RHOhv shifted to a location outside of the funnel with relative higher RHOhv along the tornado center axis. In addition, a column of positive ZDR appeared at the center of the tornado surrounded by negative ZDR. It is hypothesized that the tornado entrained hydrometeors resulting in positive ZDR. The negative ZDR within the large debris cloud suggests that common debris alignment was dominating. A band of low RHOhv was associated with small dust and debris being lofted by the strong winds rotating around the hook echo within the weak-echo notch. This band appeared as another distinct column of low RHOhv near the tornado and was ultimately entrained into main circulation.

A comprehensive aerial survey identified the surface damage tracks associated with the tornadoes. The survey was particularly helpful in documenting the ground cover and relating it to changes observed in the debris cloud as the tornado traversed different fields.

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