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A Review of the North Alabama Violent Tornado Outbreak. February 6, 2008. Brian Carcione & David Nadler NWS Huntsville, Alabama. Overview. Modified version of presentation given to 7 th Annual Southeast Severe Storms Symposium

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a review of the north alabama violent tornado outbreak

A Review of the North Alabama Violent Tornado Outbreak

February 6, 2008

Brian Carcione & David Nadler

NWS Huntsville, Alabama

overview
Overview
  • Modified version of presentation given to 7th 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
local event overview
Local Event Overview

No additional tornado damagein Tennessee

EF-4

3:00 to 3:20 AM

EF-1

EF-45:17 to 5:34 AM

EF-14:43 AM

EF-1

EF-04:00 AM

EF-2

EF-0

“Storm Track Map” – MESH Data from NSSL

09 11z utc spc mesoanalysis
09 & 11Z UTC SPC Mesoanalysis

0-1km SRH & Storm Motion

MLCAPE (contour) & MLCIN (shaded)

storm scale radar analysis
Storm-scale / Radar Analysis

0600-1100UTC 06 Feb 2008 Radar Mosaic

kgwx 0 5 1 3 br srm 0859z 06 feb
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

khtx 0 5 1 3 br srm 0906z 06 feb
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

uah armor data 0848 0907z 06 feb data interrogated visualized with gr2analyst
UAH ARMOR Data – 0848-0907Z 06 FebData interrogated & visualized with GR2Analyst

81kt rotational velocity

0.7° Base Reflectivity and Velocity

ARMOR: 25-40nm away, 0.7° angle elevation ~2220-2970’ AGL

uah armor data 0912 0915z 06 feb
UAH ARMOR Data – 0912-0915Z 06 Feb

99kt Base Velocity at 1700’ AGL

0.7° Base Reflectivity and Velocity

ARMOR: 20-30nm away, 0.7° angle elevation ~1600-2000ft AGL

lma data w khtx refl srm lrm
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

lma data w khtx refl srm lrm1
LMA Data w/ KHTX Refl/SRM & LRM

Lawrence County Storm - 0856Z Feb06 2008

Source density jumps to ~ 61

lma data w khtx refl srm lrm2
LMA Data w/ KHTX Refl/SRM & LRM

Lawrence County Storm - 0902Z Feb06 2008

Slight decrease in source density

Tornado reported on the ground

lma data w khtx refl srm lrm3
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

khtx 0 5 1 3 br srm 1043z 06 feb
KHTX 0.5_1.3° BR/SRM - 1043Z 06 Feb

Jackson County Tornado

Brief EF-1 touchdown just north of Guntersville, AL

khtx 0 5 1 3 br srm 1125z 06 feb
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

uah armor data 1118 1119z 06 feb
UAH ARMOR Data – 1118-1119Z 06 Feb

84kt velocity

87kt rotational velocity at 3680’ AGL

0.7° Base Reflectivity and Velocity

ARMOR: ~45nm away, 0.7° angle elevation ~3700-4600ft AGL

lma data w khtx refl srm lrm4
LMA Data w/ KHTX Refl/SRM & LRM

Jackson County Storm - 1032Z Feb06 2008

Max source density ~ 105

No tornado reports yet

lma data w khtx refl srm lrm5
LMA Data w/ KHTX Refl/SRM & LRM

Jackson County Storm - 1038Z Feb06 2008

Significant decrease within 6 minutes

Reflectivity suggests a more ‘classic’ supercell structure with more impressive updrafts

EF-1 Tornado on the ground

lma data w khtx refl srm lrm6
LMA Data w/ KHTX Refl/SRM & LRM

Jackson County Storm - 1100Z Feb06 2008

Big jump as storm ascends Sand Mountain

Reflectivity diminishing, perhaps becoming a lower-topped supercell

No tornado on the ground at this time

lma data w khtx refl srm lrm7
LMA Data w/ KHTX Refl/SRM & LRM

Jackson County Storm - 1125Z Feb06 2008

Enhanced “white” area possible debris being detected by 88D base reflectivity

Storm begins to weaken, supported by significant flash decrease

EF-4 Tornado on the ground

slide23

Ascending Sand Mountain

EF-1 near Guntersville

EF-4 Tornado

food for thought armor
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
food for thought lma
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
questions or comments

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