1. Severe Weather Seminar Spring 2011 Pat.spoden@noaa.gov

2. One of the 3 base moments available with WSR-88D Measures the variability of movement within a bin With super-high resolution, there is much we can see Not available on the web – GR software only – Color scales important, as always

3. Spectrum Width depicts a measure of velocity dispersion. It provides a measure of the variability of the mean radial velocity estimates due to wind shear, turbulence, and/or the quality of the velocity samples. It is used to estimate turbulence associated with boundaries, thunderstorms, mesocyclones.

4. Low Spectrum Width High Spectrum Width Both situations can be helpful…

5. Depicts a smooth flow Supercell May 2, 2010

6. Low, or smooth values

7. Rear Flank Downdraft

8. Tornado is now “cutoff” and soon dissipates

9. Tornado RFD wind damage

10. Distant Supercell May 2, 2010 EF0 Tornado in northern Butler Image from 10-15 mintues prior to touchdown

12. TBSS – Three Body Scatter Spike

13. August 14, 2010 -Signature seen 5-10 minutes prior to 65-70 mph microburst.

15. It is not always clear nor easy to locate the true “leading edge.” Strong winds can push storms upshear which may complicate the matter Next Question Where is the “leading edge” ? ?

16. Use Spectrum Width or Velocity product Solutions

17. Where is the “leading edge?” Where you thought?

18. Another way to help spot interfaces and mesovortices – use SPECTRUM WIDTH!

19. Depicts turbulence within the range bin. Low values suggest “smooth flow” –RFDs, inflow High values suggest turbulent flow –Boundaries –Potential of tornadic signatures with weak rotation