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Analysis of TBSSs and Moist Environments Affecting Severe Weather Dynamics

This presentation explores the relationship between Three-Body Scatter Spikes (TBSSs) and moisture-laden environments, focusing on observed radar artifacts often associated with severe weather phenomena such as hail. Through case studies from 2005 and 2004, the findings illuminate the correlation between TBSSs, storm characteristics, and precipitation types, emphasizing the potential for damaging winds and flash flooding. The study proposes enhancements to severe thunderstorm warning criteria to better account for conditions producing smaller hail and significant rainfall.

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Analysis of TBSSs and Moist Environments Affecting Severe Weather Dynamics

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  1. An Update on TBSSs and Relatively Moist Environments Matthew J. Bunkers 2006 Spring Training

  2. Three-Body Scatter Spike (TBSS)

  3. TBSS Review • Radar artifact typically associated with hail ≥ 1”(high POD and low FAR) • Observed down-radial of ~62+ dBZ core(use 4-panel and/or all-tilts displays) • May also indicate potential for damaging winds? • More at P:\Training\8thGreatDivide\TBSS

  4. Recent Trends • At least two events in 2005 with TBSSs but only limited, or no, severe hail • Another case around the same time with TBSSs and very large hail • What’s going on here?

  5. #1 – 10 August 2005, 2130z Max Ref = 68.5 dBZ Hgt50dBZ = 20,345 ft AGL TBSS length = 8 nm POSH = 50 % MEHS = 1 ¼ “ (250%) MLT = 11,180 ft AGL WBZ = 9,849 ft AGL RH700-300mb = 33 % Max Obs. Hail = ½ “ *** Next five sets of images are all the at same scale

  6. #2 – 11 August 2005, 0214z Max Ref = 70 dBZ Hgt50dBZ = 31,590 ft AGL TBSS length = 12 nm POSH = 90 % MEHS = 2 ½ “ (143%) MLT = 11,180 ft AGL WBZ = 9,849 ft AGL RH700-300mb = 33 % Max Obs. Hail = 1 ¾ “

  7. #3 – 25 July 2005, 0438z Max Ref = 65.5 dBZ Hgt50dBZ = 33,689 ft AGL TBSS length = 8 nm POSH = 80 % MEHS = 2 ¼ “ (225%) MLT = 13,322 ft AGL WBZ = 9,885 ft AGL RH700-300mb = 19 % Max Obs. Hail = 1 “

  8. #4 – 25 July 2005, 0453z Max Ref = 65.5 dBZ Hgt50dBZ = 33,931 ft AGL TBSS length = 10 nm POSH = 70 % MEHS = 2 “ (400%) MLT = 13,322 ft AGL WBZ = 9,885 ft AGL RH700-300mb = 19 % Max Obs. Hail = ½ “

  9. #5 – 20 July 2005, 2224z Max Ref = 66.5 dBZ Hgt50dBZ≥ 31,500 ft AGL TBSS length = 9 nm POSH = 70 % MEHS = 2 “ (73%) MLT = 12,133 ft AGL WBZ = 10,911 ft AGL RH700-300mb = 23 % Max Obs. Hail = 2 ¾ “

  10. What does this show? • Not much difference up to this point… • Similar max reflectivity, TBSS lengths, and MLT/WBZ levels • Generally small-to-moderate storm cores • Is there a pattern in the moisture field that can help explain this?

  11. #1 – 10 August 2005, 2131z (wv sat)

  12. #2 – 11 August 2005, 0215z (wv sat)

  13. #3,4 – 25 July 2005, 0445z (wv sat)

  14. #5 – 20 July 2005, 2224z (wv sat)

  15. From AWOC… • Recall that a moist atmosphere can accelerate the hail melting process • Flash presentation…http://www.wdtb.noaa.gov/courses/awoc/ICsvr1/ICSvr1-lesson3/ic1-lesson3_color/ • Let’s look at one final case from 2004

  16. #6 – 3 July 2004, 2128z Max Ref = 74.5 dBZ Hgt50dBZ = 33,348 ft AGL TBSS length = 22 nm POSH = 100 % MEHS > 4 “ (400%) MLT = 9,153 ft AGL WBZ = 8,017 ft AGL *RH700-300mb = 50 % Max Obs. Hail = 1 “ Produced flash flooding and copious small hail *** Note this is at a smaller scale than the previous radar images

  17. 03 July 2004, 2115z (wv sat)

  18. Summary • Phone logs indicate these storms with TBSSs and sub-severe to marginally severe hail produced very heavy rainfall and copious small hail • Some of these storms were supercells, but still struggled to produce very large hail • The best discriminator for these events may be the water vapor imagery

  19. Summary • The length of the TBSSs were below average, based on J. Johnson’s local study(however the last event was 22 nm)

  20. Summary • The SOO proposes an additional CTA for severe thunderstorm warnings to account for these kinds of events/environments… “This storm is capable of producing a lot of small to moderate size hail and very heavy rainfall…possibly causing low lying roads to become covered with ice.” (or something like this)

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