3.1 Close-Range Radar Observations and High-Resolution Damage Survey of a Large, Intense Tornado in a Forested Area during the VORTEX-SE Meso18-19 Field Campaign

Monday, 13 January 2020: 2:00 PM
203 (Boston Convention and Exhibition Center)
Anthony W. Lyza, Univ. of Alabama in Huntsville, Huntsville, AL; and B. T. Goudeau and K. R. Knupp

A substantial tornado outbreak impacted a wide portion of the southern U.S. on 13-14 April 2019. One supercell moved from east-central MS to northwestern AL, producing a total of six tornadoes. The most significant tornado of this tornado family occurred in an area of low population density near the community of Greenwood Springs, MS, just west of the MS/AL border in Monroe and Itawamba Counties. Given the severity and impact of this event, an initial ground survey of accessible areas was followed by a more comprehensive aerial survey to relate damage patterns to radial velocities associated with the large tornadic circulation along the tornado path, which passed over complex topography with a mixed forested canopy. The path length and maximum width of the tornado were approximated to be 24.6 km (15.3 mi.) and 2100 m (1.3 mi.), respectively. The maximum damage discovered during the ground survey was consistent with an EF3 rating, with an estimated maximum 3-s gust speed of 73.8 m/s (165 MPH), based on the collapse of five 400-MW high-tension transmission truss towers, in the context of nearby exceptional tree fall damage.

The tornado formed approximately 2.4 km SSE of the Columbus, MS, WSR-88D radar (KGWX) and moved NNE, passing within 800 m of the radar site before moving northward and growing substantially in size and intensity. Due to the close passage to the east of KGWX and the sharp northward component of motion, the tornado moved nearly along a uniform azimuth relative to KGWX while it was at maximum intensity, enabling KGWX to sample nearly the maximum wind speed in Doppler velocity, despite a translational speed of 24-26 m/s. The maximum Doppler velocity sampled by KGWX was 81.5 m/s (182 MPH), observed at a range of 3.62 km and height of 56 m (183 ft.) ARL. Damage in this area of maximum radar-estimated intensity consisted of five large high-tension transmission towers collapsed and extreme forest damage, including near-100% tree fall of loblolly pine forests over a width of up to 400 m and >75% tree fall over a maximum width of approximately 700 m within the much larger tornado damage path.

This presentation gives an overview of the datasets collected on this major tornado event. Plans for the use of KGWX radar data to compare to the corresponding tree damage are highlighted. Implications of this case on the refinement of EF-scale damage indicators for tree damage are discussed.

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