1. A Multiscale Analysis of the 23-24 November 2004 Southeast United States Tornado Outbreak Alicia C. Wasula

2. Event Summary 23/1700 UTC – 24/1300 UTC (nocturnal) 23/1700 UTC – 24/1300 UTC (nocturnal) 80 Tornadoes (17 F2 or greater) 80 Tornadoes (17 F2 or greater) 3 Fatalities / 38 Injuries 3 Fatalities / 38 Injuries 45% tornadoes close to Gulf coast (south of 32  N) 45% tornadoes close to Gulf coast (south of 32  N)

4. Motivation Examine tornado episode from synoptic/mesoscale perspective to look for similarities/differences to composite Gulf coast tornado episode Examine tornado episode from synoptic/mesoscale perspective to look for similarities/differences to composite Gulf coast tornado episode

5. 0-2 km positive mean shear (x 10 -3 s -1 ) Convective Available Potential Energy (CAPE, J/kg) Johns et al. 1993 CAPE vs. Shear for Cold Season Tornado Cases

6. 0-2 km positive mean shear (x 10 -3 s -1 ) Convective Available Potential Energy (CAPE, J/kg) Johns et al. 1993 CAPE vs. Shear for Warm Season Tornado Cases

7. Tornado Episode Composites NCEP/NCAR 2.5  x 2.5  Reanalysis dataset NCEP/NCAR 2.5  x 2.5  Reanalysis dataset All tornado episodes 1950-2001 All tornado episodes 1950-2001 ‘Episode-relative’ composite ‘Episode-relative’ composite Grouped by start time: 0000-0600, 0600- 1200, 1200-1800, 1800-0000 UTC Grouped by start time: 0000-0600, 0600- 1200, 1200-1800, 1800-0000 UTC Will show 0600-1200 UTC only Will show 0600-1200 UTC only

8. 200 hPa height (m), isotachs (m s -1 ) 500 hPa hgt (m), avor. (x 10 -5 s -1 ), vort. adv. (x 10 -10 s -2 )

9. 850 hPa hgt (m), temp (  C), temp. adv. (x 10 -5  C s -1 ) 1000 hPa height (m), 1000-500 thck. (dam), 700 hPa RH (%)

10. 700 hPa height (m), vertical motion (x 10 -3 hPa s -1 ) 850 hPa winds,  e (K), 850-500 lapse rate (  C)

11. Summary: Composites Strong signal in spite of large sample size: Strong signal in spite of large sample size: ULJ entrance region at 200 hPa ULJ entrance region at 200 hPa Vigorous upstream trough at 500 hPa Vigorous upstream trough at 500 hPa Southwesterly LLJ at 850 hPa Southwesterly LLJ at 850 hPa Low-level  e ridge Low-level  e ridge Surface composites show 1 st tornado occurs: Surface composites show 1 st tornado occurs: At strongest  T At strongest  T On northern edge of moisture surge/southerly flow On northern edge of moisture surge/southerly flow Dew point anomalies > +8  C Dew point anomalies > +8  C

12. Case Study: 24 November 2004

13. http://www.spc.noaa.gov

15. 22 November 2004 0000 UTC SLP, 1000-500 THCK500 hPa HGHT, AVOR 200 hPa HGHT, ISOTACHS 850 hPa HGHT,  e, ISOTACHS

16. 22 November 2004 1200 UTC SLP, 1000-500 THCK500 hPa HGHT, AVOR 200 hPa HGHT, ISOTACHS 850 hPa HGHT,  e, ISOTACHS

17. 23 November 2004 0000 UTC SLP, 1000-500 THCK500 hPa HGHT, AVOR 200 hPa HGHT, ISOTACHS 850 hPa HGHT,  e, ISOTACHS

18. 23 November 2004 1200 UTC SLP, 1000-500 THCK500 hPa HGHT, AVOR 200 hPa HGHT, ISOTACHS 850 hPa HGHT,  e, ISOTACHS

19. 23 November 2004 1800 UTC SLP, 1000-500 THCK500 hPa HGHT, AVOR 200 hPa HGHT, ISOTACHS 850 hPa HGHT,  e, ISOTACHS

20. 24 November 2004 0000 UTC SLP, 1000-500 THCK500 hPa HGHT, AVOR 200 hPa HGHT, ISOTACHS 850 hPa HGHT,  e, ISOTACHS

21. 24 November 2004 0600 UTC SLP, 1000-500 THCK500 hPa HGHT, AVOR 200 hPa HGHT, ISOTACHS 850 hPa HGHT,  e, ISOTACHS

22. 24 November 2004 1200 UTC SLP, 1000-500 THCK500 hPa HGHT, AVOR 200 hPa HGHT, ISOTACHS 850 hPa HGHT,  e, ISOTACHS

23. CAPE 1847 J/kg LI -7 0-6 km shear 38 kt 0-2 km shear 18 kt SWEAT400 JAN 23/2100 UTC

24. CAPE 1648 J/kg LI -6 0-6 km shear 58 kt 0-2 km shear 16 kt SWEAT464 JAN 24/0000 UTC

25. CAPE 81 J/kg LI 3 0-6 km shear 39 kt 0-2 km shear 22 kt SWEAT225 JAN 24/1200 UTC

26. CAPE 1794 J/kg LI -6 0-6 km shear 54 kt 0-2 km shear 4 kt SWEAT279 LIX 24/0000 UTC

27. CAPE 2087 J/kg LI -7 0-6 km shear 40 kt 0-2 km shear 12 kt SWEAT332 LIX 24/0600 UTC

28. CAPE 2986 J/kg LI -10 0-6 km shear 32 kt 0-2 km shear 10 kt SWEAT513 LCH 23/1800 UTC

29. CAPE 2412 J/kg LI -8 0-6 km shear 42 kt 0-2 km shear 9 kt SWEAT353 LCH 24/0000 UTC

30. Surface Analysis 24 November 2004 0000 UTC

31. http://www.spc.noaa.gov

33. Surface Analysis 24 November 2004 0600 UTC

34. http://www.spc.noaa.gov

35. <> IR 24 November 2004 0615 UTC http://locust.mmm.ucar.edu

36. http://www.spc.noaa.gov

37. Surface Analysis 24 November 2004 1200 UTC

38. http://www.spc.noaa.gov

40. Conclusions Tornado episode occurred: Tornado episode occurred: In presence of strong synoptic-scale forcing for ascent (in warm sector) In presence of strong synoptic-scale forcing for ascent (in warm sector) LLJ strength increased overnight LLJ strength increased overnight Surface winds stayed south or southeast as surface low rapidly deepened to the north Surface winds stayed south or southeast as surface low rapidly deepened to the north Ample moisture and instability Ample moisture and instability

41. Conclusions Case study shows similarities to composite tornado episode Case study shows similarities to composite tornado episode Strong shear/ULJ/LLJ Strong shear/ULJ/LLJ Deepening surface cyclone Deepening surface cyclone Ample low-level moisture (esp. close to coast) Ample low-level moisture (esp. close to coast) Surface winds ‘back’ with time ahead of surface low Surface winds ‘back’ with time ahead of surface low Difference: Difference: Mesoscale thermal gradient? Mesoscale thermal gradient?

42. Future Work Question: Question: Did isallobaric effects help to keep flow in warm sector southerly/southeasterly and allow warm moist Gulf air to remain in place close to coast? Did isallobaric effects help to keep flow in warm sector southerly/southeasterly and allow warm moist Gulf air to remain in place close to coast? Why did LLJ increase in strength so rapidly? Why did LLJ increase in strength so rapidly? Dynamically driven? Dynamically driven?