1. Observations of Near-Surface Thermodynamic and Wind Shear Profiles on Significant Tornado Days Observations of Near-Surface Thermodynamic and Wind Shear Profiles on Significant Tornado Days Photo Credit: Ming Ying Wei NWS Duluth Minnesota Great Lakes Operational Meteorology Workshop – Toronto, Onrario 22 March 2010 Dan Miller Science and Operations Officer NWS/WFO Duluth, Minnesota Dan Miller Science and Operations Officer NWS/WFO Duluth, Minnesota

2. Some Preliminary Thoughts… 1)Compilation of case observations/discussions 2)There are more questions posed than conclusions drawn from this talk 3)Evidence warrants further investigation by researchers of these topics through modeling/field ops/etc. 4)The soundings/hodographs to be presented are in no way to be interpreted in a universal manner for forecasting significant tornado environments! 1)Compilation of case observations/discussions 2)There are more questions posed than conclusions drawn from this talk 3)Evidence warrants further investigation by researchers of these topics through modeling/field ops/etc. 4)The soundings/hodographs to be presented are in no way to be interpreted in a universal manner for forecasting significant tornado environments!

3. Which VWP/Hodo is “Better” for Tornadoes? Lots of 2-3” Hail Limited Wind no Tornadoes Lots of 2-3” Hail Limited Wind no Tornadoes Multiple Cyclic Tornadic Supercells F2-F3 tornadoes Multiple Cyclic Tornadic Supercells F2-F3 tornadoes

4. Which Sounding is “Better” for Tornadoes? Multiple long-tracked F3-F5 tornadoes Classic Supercells Multiple long-tracked F3-F5 tornadoes Classic Supercells Lots of Hail/Wind 2 short-lived weak Tornadoes HP Supercells (strong cold pools) Lots of Hail/Wind 2 short-lived weak Tornadoes HP Supercells (strong cold pools)

5. Oklahoma: 3 May 1999 00 UTC 1999 0504 1000 m agl 350 m agl 350 m agl wind 165 @41kt 1000 m agl Observed Storm Motion SFC Wind 160 @17kt

6. Missouri: 4 May 2003 00 UTC 2004 0503 1000 m agl 350 m agl 1000 m agl Observed Storm Motion SFC Wind 150 @12kt 350 m agl wind 175 @24kt

7. Northeast Kansas: 4 May 2003 18 UTC 2003 0504 1000 m agl 360 m agl 1000 m agl Observed Storm Motion SFC Wind 165 @15kt 360 m agl wind 180 @35kt

8. Oklahoma: 8 May 2003 00 UTC 2003 0509 1000 m agl 350 m agl 1000 m agl Observed Storm Motion SFC Wind 160 @13kt 350 m agl wind 170 @34kt

9. Kansas/Oklahoma: 26 April 1991 00 UTC 1991 0427 1000 m agl 300 m agl 1000 m agl Observed Storm Motion SFC Wind 178 @12kt 350 m agl wind 165 @32kt

10. Ohio/Tennessee: 10 November 2002 00 UTC 2002 1111 1000 m agl 400 m agl 1000 m agl Observed Storm Motion SFC Wind 180 @17kt 400 m agl wind 195 @49kt

11. Pennsylvania/Ontario: 31 May 1985 00 UTC 1985 0601 1000 m agl 400 m agl 1000 m agl Observed Storm Motion SFC Wind 195 @15kt 400 m agl wind 200 @32kt

12. Ohio Valley Region: 3 April 1974 00 UTC 1974 0404 1000 m agl 400 m agl 1000 m agl Observed Storm Motion SFC Wind 185 @15kt 400 m agl wind 200 @38kt

13. Western Tennessee: 2 April 2006 00 UTC 2006 0403 1000 m agl 500 m agl 1000 m agl Observed Storm Motion SFC Wind 207 @16kt 500 m agl wind 225 @35kt

14. Minnesota: 16 June 1992 00 UTC 1992 0617 1000 m agl 350 m agl 1000 m agl Observed Storm Motion SFC Wind 095 @17kt 350 m agl wind 100 @32kt

15. Edmonton Alberta: 31 July 1987 00 UTC 1987 0801 1000 m agl 450 m agl 1000 m agl Observed Storm Motion SFC Wind 070 @09kt 450 m agl wind 081 @18kt

16. California (Sacramento) – 21 February 2005 21 UTC 2005 0221 1000 m agl 500 m agl 1000 m agl Observed Storm Motion SFC Wind 340 @10kt 500 m agl wind 070 @18kt

17. Question: Is the “sickle” shape to the hodograph real, or merely an artifact of data sampling? Wind Measured By Radiosonde Observed hodograph Surface wind measured by Anemometer

18. Question: Is the “sickle” shape to the hodograph real, or merely an artifact of data sampling? 1000 m agl 190 @18kt SFC Wind 125 @10kt 400 m agl wind 135 @18kt NAM bufr forecast hodograph

19. Question: Is the “sickle” shape to the hodograph real, or merely an artifact of data sampling? ~350 m agl 55-60kt outbound ~350 m agl 55-60kt outbound ~350 m agl 60-65kt inbound ~350 m agl 60-65kt inbound Greensburg KS Event: 5/4/2007

20. Mean Parameters of the 20 Cases: Surface Temperature: 76 Surface Dewpoint: 68 Surface T/Td spread: 7.7 Surface Relative Humidity 69% LCL Height (agl): 2630 ft (802 m) LFC Height (agl): 4425 ft (1349 m) CAPE (surface parcel): 3206 j/kg CIN (surface parcel): 34 j/kg Surface Temperature: 76 Surface Dewpoint: 68 Surface T/Td spread: 7.7 Surface Relative Humidity 69% LCL Height (agl): 2630 ft (802 m) LFC Height (agl): 4425 ft (1349 m) CAPE (surface parcel): 3206 j/kg CIN (surface parcel): 34 j/kg (2/21/2005 Sacramento Case Not Included)

21. Operational Implications? How often do you get a warm and very humid airmass, that possesses strong instability and sufficient deep-layer shear for supercells that is also co-located with strong near-surface shear – and is nearly un-capped? From Nordin and Brooks, 2002

22. Some Important (and Perhaps Troublesome) Questions: 1) What do we mean when we say “elevated” vs. “surface-based” convection? 2) Do we need to consider “elevated” vs. “boundary-layer” vs. “surface- based” convection? 2) Do we need to consider “elevated” vs. “boundary-layer” vs. “surface- based” convection? 3) How do we *know* what parcels are ascending into the updraft? 4) What implications does this have for many of our near-storm environment forecast parameters? 4) What implications does this have for many of our near-storm environment forecast parameters?

23. Now The Dirty Details: All of this critical “stuff” is going on in a VERY shallow near-surface layer Red = SFC – 400m agl Cyan = 400m – 1000m agl Lavender = 1000m – 7000 m agl Red = SFC – 400m agl Cyan = 400m – 1000m agl Lavender = 1000m – 7000 m agl

24. Just Exactly How Shallow is this Layer? 457 m 1500 ft 457 m 1500 ft 553 m 1815 ft 553 m 1815 ft

25. Question: Is there a more effective way to examine low-level wind shear? Are We Looking Low Enough? Surface-400m shear vector Surface-1 km shear vector

26. Mean Parameters of the 20 Cases: Height of hodograph kink agl: 399 m Bulk Shear Vector Magnitude (sfc-kink): 18 kt Bulk Shear Vector Magnitude (sfc-1 km): 25 kt Bulk Shear Vector Ratio: 0.72 Height of hodograph kink agl: 399 m Bulk Shear Vector Magnitude (sfc-kink): 18 kt Bulk Shear Vector Magnitude (sfc-1 km): 25 kt Bulk Shear Vector Ratio: 0.72 (2/21/2005 Sacramento Case Not Included)

27. Central Florida – 25 December 2006 12 UTC 2006 1225 1000 m agl 300 m agl 1000 m agl Observed Storm Motion SFC Wind 175 @12kt 300 m agl wind 175 @39kt

28. Question: What is our true skill in choosing the “correct” parcel to lift in the calculation of numerous popular near-storm environment parameters and indices?

29. What about the mixed boundary layer? Question: What is our true skill in choosing the “correct” parcel to lift in the calculation of numerous popular near-storm environment parameters and indices?

30. Question: Do we need to re-evaluate our use of the terms “elevated” and “surface-based” convection?

31. What are the “correct” parcels with this thermodynamic profile? Question: Do we need to re-evaluate our use of the terms “elevated” and “surface-based” convection? How do we define “surface-based” DMC? Theta-e decreases rapidly with height

32. Question: What is the importance of surface heating in the contribution to instability on significant tornado days? How does the atmosphere produce/maintain this thermodynamic profile in the near-surface layer near max heating time?

33. Calculation of both of these indices for some useful purpose requires an accurate input value of total CAPE and shear over the appropriate layer (0-1 km/0-3 km/etc.)… …but how do we know what is the appropriate parcel to choose for an accurate value of CAPE? – and therefore… …how do we know what effective shear the storm is tapping? Calculation of both of these indices for some useful purpose requires an accurate input value of total CAPE and shear over the appropriate layer (0-1 km/0-3 km/etc.)… …but how do we know what is the appropriate parcel to choose for an accurate value of CAPE? – and therefore… …how do we know what effective shear the storm is tapping? Question: Can we improve on the utility of the two near- storm environment significant tornado parameters that have shown the most promise: namely surface-1km EHI and surface- 3km VGP?

34. Implications for NSE Parameters: 100 mb Mean-Layer CAPE (MLCAPE) 100 mb Mean-Layer CIN (MLCIN) Lowest 100 mb Averaging is “safer” - well-mixed BL should have uniform thetae Averaging is dangerous!! - thetae decreases rapidly with height in BL Difference in computed CAPE is small Difference in computed CAPE can be large - ~1000-2000 j/kg! **(VGP/EHI)**

35. Implications for NSE Parameters: 0-1 km and 0-3 km Energy-Helicity Index (EHI) 0-3 km Vorticity Generation Potential (VGP) Lowest 100 mb If the storm isn’t tapping *surface* parcels (i.e. below ~400-500m) – it isn’t realizing the full effect of the calculated EHI or VGP! Might this explain in part why VGP in particular is plagued by high false alarm ratios (>80%)?

36. Question: If a systematic search of the historical upper air database was performed, would a superposition of low-level shear and thermodynamic profiles presented here be present in a majority of significant tornado events? Question: Would a systematic search of the historical upper air database also identify null cases?

37. Climatological Frequency - Hodographs ONLY:

38. Final Thought... Superposition of these profiles appears to be critical – NOT only the “sickle” hodograph Red = SFC – 400m agl Cyan = 400m – 1000m agl Lavender = 1000m – 7000 m agl Red = SFC – 400m agl Cyan = 400m – 1000m agl Lavender = 1000m – 7000 m agl

39. Acknowledgements David Andra: NWS/WFO Norman OK Michael Foster: NWS/WFO Norman OK Rich Thompson: NWS/SPC Norman OK Dr. Bob Conzemius: WindLogics Grand Rapids MN Dr. Bruce Lee: WindLogics Grand Rapids MN Doug Speheger: NWS/WFO Norman OK Kevin Scharfenberg: NSSL Norman OK Bob Johns: former SOO SPC Norman OK Jon Davies: Private Meteorologist Kansas City MO Todd Lindley: NWS/WFO Lubbock TX Dr. Chris Weiss: Texas Tech University Lubbock TX Dr. Matt Bunkers: NWS/WFO Rapid City SD Dr. David Blanchard: NWS/WFO Flagstaff AZ David Andra: NWS/WFO Norman OK Michael Foster: NWS/WFO Norman OK Rich Thompson: NWS/SPC Norman OK Dr. Bob Conzemius: WindLogics Grand Rapids MN Dr. Bruce Lee: WindLogics Grand Rapids MN Doug Speheger: NWS/WFO Norman OK Kevin Scharfenberg: NSSL Norman OK Bob Johns: former SOO SPC Norman OK Jon Davies: Private Meteorologist Kansas City MO Todd Lindley: NWS/WFO Lubbock TX Dr. Chris Weiss: Texas Tech University Lubbock TX Dr. Matt Bunkers: NWS/WFO Rapid City SD Dr. David Blanchard: NWS/WFO Flagstaff AZ

40. Questions? Thanks for your attention! Photo Credit: Todd Lindley