The Utility of InSAR Coherence for Tornado Damage Track Identification from the 2-3 March 2020 Tennessee Tornado Outbreak

Damage surveys after suspected tornadoes can be time-consuming for NWS forecasters to conduct. Suspected damage tracks can cover a large area with limited road networks and rugged terrain, making traditional surveying methods challenging. Satellite remote sensing imagery and derived products have frequently been leveraged to assist forecasters with damage surveys. Optical imagery is sometimes obstructed by clouds and shadows, limiting when collections can be used for analysis. Synthetic aperture radar (SAR) instruments collect in all weather and are not currently incorporated into the damage survey process. This study uses interferometric SAR (InSAR) coherence to identify tornado damage tracks from the 2-3 March 2020 Tennessee tornado outbreak. Coherence damage paths (CDPs) were qualitatively identified from a single coherence pair. Physical characteristics of the identified CDPs were compared with survey data from the NOAA/NWS Damage Assessment Toolkit (DAT). Portions of five of the nine tornadoes analyzed with varying EF-scale ratings were identified. Over 70% of the total surveyed length was captured in CDPs for tornadoes rated ≥ EF-1. The coherence-derived lengths from each CDP showed a strong agreement compared to the survey, while the maximum width showed little to no agreement. Lower-rated damage (≤ EF-2) was associated with higher coherence values from 0.4-0.6, while higher-rated damage (≥ EF-3) had lower coherence values closer to 0.3. The results from this study demonstrate the ability of coherence to provide supplemental information to NWS forecasters during the storm survey process, especially after large outbreaks in hard-to-access or inaccessible locations.