Operational Use of Polarimetric Tornadic Debris Signatures

The deployment of dual polarization technology in the Next-Generation Radar (NEXRAD) network is providing opportunities to enhance operational forecasting. A number of NEXRADs have been upgraded in the last year, and there are now many examples showing how the dual polarimetric data have provided valuable information during various weather events. One such enhancement is the ability to detect lofted debris from tornadoes. Within the last year, numerous dual polarization tornadic debris signatures have been documented in the Southeast U.S. These examples have provided insight into how the debris signatures can be used during severe weather situations, and have also uncovered limitations of which operational meteorologists should be aware when using the debris signatures in warning situations.

This presentation will include examples of debris signatures from the NWS Atlanta, Birmingham, Huntsville and Nashville county warning areas. These events range from short-lived to long-track tornadoes, and provide a spectrum of information on how the debris signatures were used in operational forecasting. Topics covered are use of the debris signatures for real-time and post-event operations, the importance of separating low signal-to-noise and non-uniform beam filling artifacts from the debris signatures, and a discussion of differences in appearance of the signature in analysis software. A case where debris signature criteria were met, but no damage was observed, will also be shown. Final thoughts and lessons learned will be highlighted for future use of the signature in operations.