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An Update on TBSSs and Relatively Moist Environments

An Update on TBSSs and Relatively Moist Environments. Matthew J. Bunkers 2006 Spring Training. Three-Body Scatter Spike (TBSS). TBSS Review. Radar artifact typically associated with hail ≥ 1” (high POD and low FAR)

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An Update on TBSSs and Relatively Moist Environments

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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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