Cool Season Tornadoes in the Southeast U.S. Steven Nelson Stephen Konarik WFO Peachtree City 11 November December January November December December January December January February February 2008

2 Outline Brief Review of Severe ConvectionBrief Review of Severe Convection Climatology of Cold Season TornadoesClimatology of Cold Season Tornadoes Case StudiesCase Studies Summary / Forecasting GuidelinesSummary / Forecasting Guidelines

3 Review Ingredients for Deep Moist Convection: (note, most of the time, DMC = thunderstorms)Ingredients for Deep Moist Convection: (note, most of the time, DMC = thunderstorms) –Instability + Moisture + Lift (to the LFC) Ingredients for Severe DMC:Ingredients for Severe DMC: –All the above plus… –Greater instability and/or vertical wind shear Warm Season: High Cape / Low ShearWarm Season: High Cape / Low Shear Cool Season: Low Cape / High ShearCool Season: Low Cape / High Shear

4 Instability and Shear not Low instability does not mean little or no chance of tornadoes ! Note the absence of F2+ tornadoes when minimum shear criteria is not met. (1993)

5 Cool Season Tornado Climatology Not studied much until recentlyNot studied much until recently Used SvrPlot to study Georgia area significant cool season tornadoesUsed SvrPlot to study Georgia area significant cool season tornadoes More thorough studies by Wasula et al. (2004) and Guyer et al. (2006)More thorough studies by Wasula et al. (2004) and Guyer et al. (2006) Tornadoes produce majority of severe weather damage and loss of life in cool season.Tornadoes produce majority of severe weather damage and loss of life in cool season. –Flooding and lightning much lower threat.

6 Cool Season Tornado Climatology  Wasula et al. found approximately 50% of all southeast U.S. F2+ tornadoes occur in the cool season (Nov 1 – Feb 28)

7 Cool Season Tornado Climatology  Guyer et al. found tornadoes much more likely to persist overnight in the cool season Southeast U.S. Tornadoes by Hour (All year) Southeast U.S. Tornadoes by Hour (Oct 15 – Feb 15, )

8 Cool Season Tornado Climatology  Instability important but much lower values needed for F2+ tornadoes in the cool season MLCAPE for all F2+ tornadoes MLCAPE for SE cool season F2+ tornadoes

9 Cool Season Tornado Climatology 0-3km SRH for all F2+ tornadoes SRH for SE cool season F2+ tornadoes 0-1km SRH for all F2+ tornadoes  Somewhat more shear needed for F2+ tornadoes in the cool season

10 Date Location (where casualties occurred) IntFatInj 19 Feb pm Jasper, Pickens counties ? Feb pm Washington county ? Dec pm Fulton, Stewart counties F Dec pm,12am Jones county F Jan am Fulton county F Feb pm Peach county F Nov pm Wilcox county F Nov pm Huntsville, Alabama and several Georgia counties F (463) 22 Nov pm Cobb, Putnam, Greene counties (large 3-day outbreak killed 26 and injured 641, mostly across the southeast) F Feb pm-12am Polk, Pike counties F Oct am Lee county (Albany) F Feb am Cullman, Marshall counties (Joppa/Arab, Alabama) F Nov pm Lumpkin, Dodge counties F Feb pm-1am Mitchell, Tift, Colquitt, Grady counties (Camilla hit twice that night and yet again in March 2003 causing 4 fatalities and 200 injuries) F (175) 11 Nov am Veterans Day Outbreak (Southeast had much higher casualties than Van Wert, OH F4) F Historical Cool Season Tornadoes in the Southeast

11 Case Studies 13 February 2000 – Camilla, GA F3 Early morning (12am)Early morning (12am) 19 deaths, 202 inj19 deaths, 202 inj CAPE ~ 800 J/kgCAPE ~ 800 J/kg 0-3km SRH ~ 400 m 2 /s 20-3km SRH ~ 400 m 2 /s 2

12 Case Studies 11 November 2002 – Veterans Day Outbreak (F2) Early morning (2am)Early morning (2am) SPC High RiskSPC High Risk 25 deaths, 188 inj25 deaths, 188 inj Van Wert, OH F4Van Wert, OH F4 CAPE ~ 2500 J/kgCAPE ~ 2500 J/kg 0-3km SRH ~ 350 m 2 /s 20-3km SRH ~ 350 m 2 /s 2

13 DateLocationIntCAPE 0-1km SRH 28 December pm Laurens county (also had softball size hail in Sumter) F January pm Fulton, Fayette, Pike (baseballs in Pike and Jones) F November pm Chattahoochee (Ft Benning) F December am Ben Hill, Telfair F December pm Dooly county (Unadilla) F January am CowetaF January pm CowetaF December pm Wilcox, Dodge, Treutlen EF February pm Carroll, Crawford, Bibb, Jones EF February am CarrollEF March pm DouglasEF March pm AtlantaEF Recent Cool Season Tornadoes in Georgia

14 Recent Examples 25 December 2006 – The “Santa Claus” Tornado CAPE ~300 J/kgCAPE ~300 J/kg 0-3km SRH ~ 600 m 2 /s 20-3km SRH ~ 600 m 2 /s 2 No watch or outlookNo watch or outlook No CG lightning with storm!No CG lightning with storm! Ben Hill F1 at 630 am EST, F0 tornado near Kibbee ~ 700 am.Ben Hill F1 at 630 am EST, F0 tornado near Kibbee ~ 700 am.

15 Recent Examples 15 December 2007 – Wilcox, Dodge, Treutlen EF2 CAPE ~ 300 J/kgCAPE ~ 300 J/kg 0-1 km SRH ~ 300 m 2 /s 20-1 km SRH ~ 300 m 2 /s 2 Surface Td > 70 FSurface Td > 70 F Supercell moved NE along strong warm frontSupercell moved NE along strong warm front

16 Recent Examples 26 February 2008 – Carroll EF3 Very low CAPE ~ 150 J/kg?Very low CAPE ~ 150 J/kg? 0-1km SRH ~ 350 m 2 /s 20-1km SRH ~ 350 m 2 /s 2 Early morning event (6am)Early morning event (6am) 2 injuries, no fatalities2 injuries, no fatalities QLCS tornadoQLCS tornado 11Z MLCAPE 11Z MUCAPE 11Z 0-1km SRH

17 “Ingredients” for cool season tornadoes the same as with all tornadoes: lift, moisture, instability and vertical wind shear.“Ingredients” for cool season tornadoes the same as with all tornadoes: lift, moisture, instability and vertical wind shear. 50% of F2+ tornadoes in the southeast occur between November and February.50% of F2+ tornadoes in the southeast occur between November and February. Cool season tornadoes more likely to occur overnight.Cool season tornadoes more likely to occur overnight. Tornado-producing storms in low CAPE environments will produce very little or no lightning.Tornado-producing storms in low CAPE environments will produce very little or no lightning. –25 Dec 2006 “Santa Claus” Tornado Strong large-scale “dynamics” observed in several cases, but not necessary for significant cool season tornadoes.Strong large-scale “dynamics” observed in several cases, but not necessary for significant cool season tornadoes. Summary

18 For F2+ tornadoes in the cool season,For F2+ tornadoes in the cool season, –Some instability is necessary (usually CAPE > 500 J/kg), but large values not needed if sufficient shear is present –Likewise, shear is necessary (0-1km SRH > 125 m 2 /s 2 ), but large values not needed if relatively strong instability is present Example guidelines for cool-season F2+ tornadoes based on research and case studies:Example guidelines for cool-season F2+ tornadoes based on research and case studies: –CAPE > 1500 J/kg and 0-1km SRH > 125 m 2 /s 2 –CAPE > 500 J/kg and 0-1km SRH > 200 m 2 /s 2 –CAPE > 150 J/kg and 0-1km SRH > 300 m 2 /s 2 ?? Guidelines

19 BONUS!! What kind of warning would you issue? Slight risk to your westSlight risk to your west No watchNo watch 00Z sounding not yet in00Z sounding not yet in ASOS observation just to the east of storm:ASOS observation just to the east of storm: KXXX Z 04004KT 1 3/4SM BR FEW090 14/13 (57/55 F) A2971 KXXX Z 04004KT 1 3/4SM BR FEW090 14/13 (57/55 F) A minutes after this time, tornado touches down ½ mile west of downtown!10 minutes after this time, tornado touches down ½ mile west of downtown! Anemometer on roof of CNN center records 126 mph gust before it was destroyed.Anemometer on roof of CNN center records 126 mph gust before it was destroyed.

20 Questions?