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

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

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

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

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

WFO Huntsville, Alabama Storm-scale / Radar Analysis UTC 06 Feb 2008 Radar Mosaic

WFO Huntsville, Alabama KGWX 0.5_1.3 ° BR/SRM Z 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

WFO Huntsville, Alabama KHTX 0.5_1.3 ° BR/SRM Z 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

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

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

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

WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Lawrence County Storm Z Feb Source density jumps to ~ 61

WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Lawrence County Storm Z Feb Slight decrease in source density Tornado reported on the ground

WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Lawrence County Storm Z Feb minutes later, source density diminishes significantly Tornado still on the ground

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

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

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

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

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

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

WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Jackson County Storm Z Feb Max source density ~ 105 No tornado reports yet

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

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

WFO Huntsville, Alabama LMA Data w/ KHTX Refl/SRM & LRM Jackson County Storm Z Feb 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

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

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

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

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 (~ ) 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

WFO Huntsville, Alabama Questions or Comments? Thanks to Chris Darden and our NASA and UAH partners