Damage Survey Analysis of the 20 May 2013 Moore Tornado

On 20 May 2013, an EF5 tornado struck highly populated areas of Oklahoma, including three schools in Cleveland County. High-resolution aerial photography and ArcGIS allowed for a structure-by-structure damage survey analysis. The reconstructed tornado track length was 28 km and the total affected area was 25 sq km. There was approximately 300 million dollars worth of damage to residential homes. For this study we looked at the relationship between visual structure of the tornado and the damage it created.

A photogrammetric analysis of the tornado structure was superimposed on the damage track. It showed the visual funnel diameter scaling with EF1-2 damage. The funnel diameters and analysis of fallen trees illustrated convergent flow into the visual funnel before turning tangential. This implies strong vertical velocities. In addition, dual-polarization radar showed a well defined tornado debris signature; although there were times where the correlation coefficient (ρ_hv) minimum did not collocate with the reflectivity maximum (dz). It is hypothesized that the result is due to the entrainment of raindrops into the tornado.