Analyzing Tornadic Debris Signatures by Integrating Aerial Imagery and Polarimetric Radar Data in GIS

The historic April 27th tornado outbreak of 2011 produced 62 tornadoes in the state of Alabama, with one of the strongest being the EF-5 Hackleburg-Tanner tornado. It was captured by two separate polarimetric radars at two different wavelengths: the UAH ARMOR C-band radar and the UAH MAX X-band radar. During the damage survey for this tornado, the UAH Department of Atmospheric Science and Earth System Science Center contracted Atlantic Aerial Imagery to fly the track and capture high-resolution swaths of the damage path. This case study involves detailed analysis of the aerial imagery to outline a damage path for the tornado. This analysis is then merged with georeferenced TIFF files (GeoTIFF) of UAH ARMOR and MAX radar scans of reflectivity, velocity, correlation coefficient, and spectrum width in order to analyze dual-polarization Tornado Debris Signatures (TDSs) associated with the Hackleburg-Tanner tornado and compare the difference in TDS features, including a possible “debris ejection” signature, at different wavelengths. An analysis of TDSs from this tornado allows for the characterization of the effects of debris loading as the tornado passed over different types of terrain. Additionally, a large gap in damage from Harvest, AL to the Tennessee state line is being investigated to determine the possibility that the Hackleburg-Tanner tornado dissipated before reaching Franklin County TN and a 2nd tornado formed along the same path as the original mesocyclone occluded. The combined analysis of aerial imagery and radar data will provide a detailed picture of how the physical damage and radar signatures correlate and the effects of debris loading over different terrain. Multi-radar analysis will also provide observations of unique TDS features at two separate wavelengths.