Tornado Debris Signature

  1. Base Reflectivity - Reflectivity will indicate a severe thunderstorm, but a hook echo may not always be present.  Typical returned values will be 45 dBZ and greater. Super resolution return averages may have a higher dBZ value.

  2. Storm Relative Velocity - An azimuthal couplet should be present with strong gate-to-gate sheer indicated on SRV.

  3. Differential Reflectivity - The region co-located with the rotational couplet should have very low or near zero ZDR present, indicating lofted objects might be tumbling.

  4. Correlation Coefficient - The region co-located with Relectivity values over 45 dBZ and the rotational couplet should have considerably lowered CC values, typically below 0.80.  This TDS area may have higher surrounding CC values indicating differing sized debris.

WSR-88D Tornado Debris Signature (TDS) Quick Reference

Tornado Intensity Guidance

Example Radar Image