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HSLC Radar Climatology Update

HSLC Radar Climatology Update. Jason Davis July 26, 2012. Current Status. Developing a climatology of tornadic and non- tornadic HSLC mesocyclones/ mesovortices .

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HSLC Radar Climatology Update

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  1. HSLC Radar Climatology Update Jason Davis July 26, 2012

  2. Current Status • Developing a climatology of tornadic and non-tornadic HSLC mesocyclones/mesovortices. • Goal: Help forecasters determine if a mesocyclone/mesovortex observed in radar velocity data will be tornadic or non-tornadic.

  3. Current Status • Do this by collecting statistics for a large population of mesocyclones/mesovortices. • Currently in final stages of developing an automated method of tracking and recording information about them. • Will use tornadic circulations as well as circulations associated with false alarm tornado warnings/non-tornadic MDA detections.

  4. Method • Record max azimuthal shear value for each circulation at each time and radar tilt that it exists. • Higher azimuthal shear value = stronger couplet for circulations. • Azimuthal shear is what is used for “rotation track” maps, and is also similar to NROT.

  5. Azimuthal Shear • Calculation is similar to • But it uses velocity data from multiple bins rather than just the max outbound/max inbound through a linear least squares technique.

  6. Tracking circulations • Currently developing a method for tracking circulations. • Uses input from MDA (if triggered) and cell tracking algorithms, with QC measures to account for algorithm limitations.

  7. Potential calculations • Calculations will include comparisons between tornadic and non-tornadic circulations: • Maximum azimuthal shear during a circulation’s lifetime. • Circulation lifetime (length of time that azimuthal shear is above a certain threshold) • Depth of circulation. • Changes in circulation depth/strength over time. • Time series plots of azimuthal shear in a tornado-relative time coordinate system. • PODs/FARs for these statistics. • Will also look at how these statistics vary by convective mode and range from the radar.

  8. Questions to answer • Are tornadic circulations stronger, longer-lived, and deeper than non-tornadic circulations? • What % of HSLC tornadoes are preceded by rotation aloft? • What shear thresholds could be useful for detecting HSLC tornadoes? • What % of HSLC tornadoes are reasonably detectable, and how does this change with range from the radar?

  9. Possible Future Work • What % of broken S signatures produce tornadoes? • Do tornadic HSLC storms tend to have higher echo tops/reflectivity at higher tilts compared to non-tornadic HSLC storms—can looking for stronger cores help focus which areas of a QLCS warrant the most attention? Smith et al. 2012

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