1. WFO Huntsville, Alabama A Review of the North Alabama Violent Tornado Outbreak February 6, 2008 Brian Carcione & David Nadler NWS Huntsville, Alabama

2. WFO Huntsville, Alabama Overview Modified version of presentation given to 7 th Annual Southeast Severe Storms Symposium Focus on warning decision-making (warning forecaster’s perspective) – NWS NEXRAD Data – ARMOR Data – LMA in AWIPS and LMA trends Food for thought/points for discussion

3. WFO Huntsville, Alabama Local Event Overview “Storm Track Map” – MESH Data from NSSL EF-0 4:00 AM EF-1 4:43 AM EF-4 5:17 to 5:34 AM EF-4 3:00 to 3:20 AM EF-1 EF-2 No additional tornado damage in Tennessee EF-0 EF-1

4. WFO Huntsville, Alabama LAPS Surface Analysis Unseasonably warm air mass Temps at midnight were around 70°F with dewpoints in the low-mid 60’s Huntsville AL (HSV) Normals on Feb. 6th: 52°F (Max) / 32°F (Min) 06Z Temperatures

5. WFO Huntsville, Alabama 09 & 11Z UTC SPC Mesoanalysis 0-1km SRH & Storm MotionMLCAPE (contour) & MLCIN (shaded)

6. WFO Huntsville, Alabama Storm-scale / Radar Analysis 0600-1100UTC 06 Feb 2008 Radar Mosaic

7. WFO Huntsville, Alabama KGWX 0.5_1.3 ° BR/SRM - 0859Z 06 Feb Lawrence County Tornado EF-4 tornado touching down around this time KGWX 0.5° base velocity 100+ kt KGWX: 62nm away, 0.5° angle elevation ~5700ft AGL

8. WFO Huntsville, Alabama KHTX 0.5_1.3 ° BR/SRM - 0906Z 06 Feb Lawrence County Tornado Rotational Velocity 109kt (81kt outbound, 28kt inbound) VR Shear =.0267 s -1 KHTX: 65nm away, 0.5° angle elevation ~7400ft AGL

9. WFO Huntsville, Alabama UAH ARMOR Data – 0848-0907Z 06 Feb Data interrogated & visualized with GR2Analyst 0.7° Base Reflectivity and Velocity ARMOR: 25-40nm away, 0.7° angle elevation ~2220-2970’ AGL 81kt rotational velocity

10. WFO Huntsville, Alabama UAH ARMOR Data – 0912-0915Z 06 Feb 0.7° Base Reflectivity and Velocity 99kt Base Velocity at 1700’ AGL ARMOR: 20-30nm away, 0.7° angle elevation ~1600-2000ft AGL

11. WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Lawrence County Storm - 0840Z Feb06 2008 Max source density ~ 36 as storm enters SW Lawrence County No tornado reported at this time

12. WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Lawrence County Storm - 0856Z Feb06 2008 Source density jumps to ~ 61

13. WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Lawrence County Storm - 0902Z Feb06 2008 Slight decrease in source density Tornado reported on the ground

14. WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Lawrence County Storm - 0906Z Feb06 2008 4 minutes later, source density diminishes significantly Tornado still on the ground

15. WFO Huntsville, Alabama Supercell-squall line merger EF-4 Tornado

16. WFO Huntsville, Alabama Lawrence County Storm Track *All estimated EF-4 Rating Peak Wind 170 mph Path Length 16.7 miles Path Width ½ mile EF-4 Rating Peak Wind 170 mph Path Length 16.7 miles Path Width ½ mile

17. WFO Huntsville, Alabama KHTX 0.5_1.3 ° BR/SRM - 1043Z 06 Feb Jackson County Tornado Brief EF-1 touchdown just north of Guntersville, AL

18. WFO Huntsville, Alabama KHTX 0.5_1.3 ° BR/SRM - 1115Z 06 Feb Jackson County Tornado

19. WFO Huntsville, Alabama KHTX 0.5_1.3 ° BR/SRM - 1125Z 06 Feb Jackson County Tornado Rotational Velocity 132kts at ~ 1500ft AGL (70kt inbound, 62kt outbound) Enhanced reflectivity indicates possible debris detection

20. WFO Huntsville, Alabama UAH ARMOR Data – 1118-1119Z 06 Feb 0.7° Base Reflectivity and Velocity ARMOR: ~45nm away, 0.7° angle elevation ~3700-4600ft AGL 87kt rotational velocity at 3680’ AGL 84kt velocity

21. WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Jackson County Storm - 1032Z Feb06 2008 Max source density ~ 105 No tornado reports yet

22. WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Jackson County Storm - 1038Z Feb06 2008 Significant decrease within 6 minutes EF-1 Tornado on the ground Reflectivity suggests a more ‘classic’ supercell structure with more impressive updrafts

23. WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Jackson County Storm - 1100Z Feb06 2008 Big jump as storm ascends Sand Mountain No tornado on the ground at this time Reflectivity diminishing, perhaps becoming a lower-topped supercell

24. WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Jackson County Storm - 1125Z Feb06 2008 Storm begins to weaken, supported by significant flash decrease EF-4 Tornado on the ground Enhanced “white” area possible debris being detected by 88D base reflectivity

25. WFO Huntsville, Alabama Ascending Sand Mountain EF-1 near Guntersville EF-4 Tornado

26. WFO Huntsville, Alabama Jackson County Storm Track *All estimated EF-4 Rating Peak Wind 180 mph Path Length 10.9 miles Path Width 3/8 mile EF-4 Rating Peak Wind 180 mph Path Length 10.9 miles Path Width 3/8 mile

27. WFO Huntsville, Alabama Food for Thought: ARMOR ARMOR samples most of the ‘central’ HUN CWFA better than any NWS NEXRAD – Would have been more useful to ascertain reflectivity structure – Has some unique limitations Many forecasters are eager to use and learn about the ARMOR data GR2Analyst makes it more readily available – Dual-pol upgrade will make that data more accessable as well COMET partnership to make data available in AWIPS will be a key

28. WFO Huntsville, Alabama Food for Thought: LMA Tertiary data source during this event—radars, reports, upstream conditions, etc. were of greater importance HUN forecasters traditionally look for jumps/drops in LMA data based on earlier research (~2001-2004) This case does not disprove that, but does show weaknesses in an overly-simplistic methodology – Cool season vs. warm season environments—not all storms are created equal – Distance/sampling concerns similar to those with radar data – Difficulty in visualizing & analyzing LMA data (trends, color tables, etc.) More research, better visualization techniques, training refreshers will help

29. WFO Huntsville, Alabama Questions or Comments? Brian.Carcione@noaa.gov David.Nadler@noaa.gov http://weather.gov/huntsville Thanks to Chris Darden and our NASA and UAH partners