severe weather seminar spring 2011 [email protected]
TRANSCRIPT
Operational Use of Spectrum Width
Severe Weather Seminar
Spring 2011
What is Spectrum Width?
• 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
Spectrum Width
• 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.
Spectrum Width
Low Spectrum Width High Spectrum Width
Both situations can be helpful…
Low Spectrum Width
• Depicts a smooth flow• Supercell• May 2, 2010
Low Spectrum Width
Low, or smoothvalues
Low Spectrum Width
Rear FlankDowndraft
Low Spectrum Width
Tornado is now“cutoff” and soon dissipates
Damage Map
Tornado RFD wind damage
High Spectrum Width
Distant Supercell
May 2, 2010
EF0 Tornado in northern Butler
Image from 10-15mintues prior to touchdown
High Spectrum Width
Other Uses
• TBSS – Three Body Scatter Spike
1949 @ 9.9 (19,500 ft)
August 14, 2010
-Signature seen5-10 minutesprior to 65-70mph microburst.
1954 Cross Section
• 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”
??
• Use Spectrum Width or Velocity productSolutions
Where is the “leading edge?”
Where you thought?
Another way to help spot interfaces and mesovortices – use SPECTRUM WIDTH!
Spectrum Width
• 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