1. Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters

2. Importance of sounding information doing convective forecasts
Introduction A:
Importance of sounding information doing convective forecasts

3. Introduction B:
Sounding-derived parameters using parcel-theory

4. Introduction B:
Sounding-derived parameters using parcel-theory
CAPE

5. Introduction B:
Sounding-derived parameters using parcel-theory
CAPE
CIN

6. Introduction B:
Sounding-derived parameters using parcel-theory
CAPE
CIN
SBCAPE

7. Introduction B:
Sounding-derived parameters using parcel-theory
CAPE
CIN
SBCAPE

8. Introduction B:
Sounding-derived parameters using parcel-theory
CAPE
CIN
SBCAPE
MUCAPE

9. Introduction B:
Sounding-derived parameters using parcel-theory
CAPE
CIN
SBCAPE
MUCAPE
LCL

10. Introduction B:
Sounding-derived parameters using parcel-theory
CAPE
CIN
SBCAPE
MUCAPE
LCL
LFC

11. Introduction B:
Sounding-derived parameters using parcel-theory

12. Introduction B:
Sounding-derived parameters using parcel-theory
CAPE
CIN ~ 0 J/kg
SBCAPE
MUCAPE
CAPE
CIN
SBCAPE

13. Introduction B:
Sounding-derived parameters using parcel-theory
CAPE
CIN
SBCAPE
MUCAPE
LCL

14. Introduction B:
Sounding-derived parameters using parcel-theory
CAPE
CIN
SBCAPE
MUCAPE
LCL
LFC

15. Is it useful to use them on horizontal maps?
Introduction C:
Sounding-derived parameters in horizontal forecast charts
Is it useful to use them on horizontal maps?

16. Is it useful to use them on horizontal maps?
Introduction C:
Sounding-derived parameters in horizontal forecast charts
Is it useful to use them on horizontal maps?
Horizontal cross sections provide barely enough information for convective forecasts:

17. Is it useful to use them on horizontal maps?
Introduction C:
Sounding-derived parameters in horizontal forecast charts
Is it useful to use them on horizontal maps?
Horizontal cross sections provide barely enough information for convective forecasts: Inversions, moist layers, shear profile not well represented.

18. Is it useful to use them on horizontal maps?
Introduction C:
Sounding-derived parameters in horizontal forecast charts
Is it useful to use them on horizontal maps?
Horizontal cross sections provide barely enough information for convective forecasts: Inversions, moist layers, shear profile not well represented.
Looking at forecast soundings or vertical cross sections yields required information, but it takes time to find regions of interest.

19. Is it useful to use them on horizontal maps?
Introduction C:
Sounding-derived parameters in horizontal forecast charts
Is it useful to use them on horizontal maps?
Horizontal cross sections provide barely enough information for convective forecasts: Inversions, moist layers, shear profile not well represented.
Looking at forecast soundings or vertical cross sections yields required information, but it takes time to find regions of interest.
Parameters highlight interesting regions as well as selective variables and are helpful...
...to get a brief overview.
...to compare different numerical models.

20. Complex parameters using “significant” levels
Introduction C:
Sounding-derived parameters in horizontal forecast charts
Complex parameters using “significant” levels
Total totals index (TOTL) = T850 + Td * T500 [°C]
K index = T850 + Td850 - T500 - (T-Td)700 [°C]
Sweat index = 12*Td850+20*(TOTL-49)+2*U850+5*U *(0.2+sinf)
where f=(wind direction500-wind direction850), U=wind speed[kts], TOTL=0 if TOTL<49

21. Complex parameters using significant levels
Introduction C:
Sounding-derived parameters in horizontal forecast charts
Complex parameters using significant levels
Total totals index (TOTL) = T850 + Td * T500 [°C]
K index = T850 + Td850 - T500 - (T-Td)700 [°C]
Sweat index = 12*Td850+20*(TOTL-49)+2*U850+5*U *(0.2+sinf)
where f=(wind direction500-wind direction850), U=wind speed[kts], TOTL=0 if TOTL<49
We do not use them for tornado forecasting.
Using them requires a guide of “magical” numbers - and not physical understanding of the weather situation.

22. “One-slide introduction” of myself…
Pieter Groenemeijer
(almost) M.Sc. in Meteorology
Utrecht University
Oklahoma University (spring semester 2002)
2002 and 2004 European Severe Storms Conferences (Prague, León)
ESWD (European Severe Weather Database)
“Sounding-derived parameters associated with large hail and tornadoes in the Netherlands“
Co-initiator of ESTOFEX (with Johannes Dahl and Christoph Gatzen), Oct, 2002.

23. Sounding-derived parameters associated with large hail and tornadoes in the Netherlands
Pieter Groenemeijer (IMAU; ESTOFEX), Aarnout van Delden (IMAU)
F3 tornado near Deil, (A.C. Frenks)

24. Sounding-derived parameters associated with large hail and tornadoes in the Netherlands
study done at Institute for Marine and Atmospheric Research Utrecht

25. Main questions
What sounding-derived parameters can be used to forecast tornadoes?
………………….. large hail?
sub-question:
How do the results differ from studies from the United States?

26. Basic idea
Find soundings taken in the proximity of severe weather events (here: tornadoes)
Find if they have special characteristics (w.r.t. other soundings)
method: look at parameters
that represent something physical
and that have been studied before

27. Proximity soundings What is a proximity sounding…? Used definition:
within 4 hours of the sounding
(before or after)
within 100 km from a point that
is advected by the 0-3 km mean
wind from the sounding location
at the sounding time

28. Data sets radiosonde observations Dec 1975 – Aug 2003
(thanks to KNMI, DWD, KMI)
severe weather reports from Dutch voluntary observers (VWK)
Sinds 1974
Vereniging voor Weerkunde en Klimatologie (VWK)

29. Data soundings associated with: number hail (2.0 - 2.9 cm)
tornadoes F0
tornadoes F1
tornadoes F2
waterspouts
thunder ( only) 46 47 24 37 6 26
2045
all soundings
67816

30. results…

31. Most-unstable CAPE (MUCAPE)
Number of events 
US studies: MUCAPE highly variable with tornadoes. Strong tornadoes may occur with low CAPE when shear is high
maximum
 75th perc.
median
 25th perc.
MUCAPE not very high with tornadoes…

32. Most-unstable CAPE released below 3 km A.G.L.
US studies: Davies (2004) has found a relation between tornado occurrence and high CAPE below 3km (in his study M.L.CAPE)...
MUCAPE<3km high with F0, not with F1+

33. (most-unstable) LFC height (m)
US studies: Davies (2004) has found a relation between low LFC and tornado occurrence
LFC relatively low with tornadoes (esp. F0)…

34. LCL height (50 hPa mixed layer parcel)
US studies: Low LCL favors significant tornadoes, e.g. Craven et al. (2002)
LCL not sign. diff. between tornadic and thunder

35. Average soundings LARGE HAIL F0 F1+
note the distribution of parcel buoyancy with height

36. 0-6 km A.G.L. bulk shear (m/s)
US studies: strong tornadoes often occur with supercells associated with >20 m/s 0-6 km shear (e.g. Doswell&Evans, 2003)
0-6 km bulk shear high with F2 tornadoes

37. 0-1 km A.G.L. bulk shear (m/s)
US studies: strong 0-1 km shear favours for sign. tornadoes (e.g. Craven et al., 2002).
0-1 km shear high with F1, esp. F2 tornadoes..

38. 0-1 km A.G.L. storm-relative helicity (m2/s2)
US studies: high values favor supercell tornadoes (e.g. Rasmussen, 2003).
0-1 km shear high with F1, esp. F2 tornadoes..

39. Some conclusions
F1 and esp. F2 tornadoes occur with higher-than-average 0-1 km shear (and SRH, but less clearly).
F0 tornadoes (and waterspouts) occur with lower-than-average 0-1 km shear values
(MU)CAPE is not extreme with tornadoes and thereby has limited value for tornado forecasting.

40. Some conclusions
MUCAPE released below 3 km / low LFC heights seem to be important for the formation of weaker (and likely non-supercellular) tornadoes….
(but of course we rather want to forecast the stronger tornadoes)
LCL heights are probably not as much a limiting factor for tornado development in the NL (and in Germany?) than in much of the U.S.A.
i.e. LCL heights are practically always low enough here for tornadoes

41. (ask me if you want to see this slide again)
References
(ask me if you want to see this slide again)
Craven, J. P., H. E. Brooks, and J. A. Hart, 2002: Baseline climatology of sounding derived parameters associated with deep, moist convection. Preprints, 21st Conference on Severe Local Storms, San Antonio, Texas, American Meteorological Society, 643–646.
Davies, J. M., 2002: On low-level thermodynamic parameters associated with tornadic and nontornadic supercells. Preprints, 21st Conf. on severe local storms, Kananaskis Park, Alberta, Canada, Amer. Meteor. Soc., 558–592.
Davies, J. M., 2004: Estimations of CIN and LFC Associated with Tornadic and Nontornadic Supercells. Wea. Forecasting, 19, 714–726.
Doswell, C. A. III, and J. S. Evans, 2003: Proximity sounding analysis for derechos and supercells: An assessment of similarities and differences. Atmos. Res., 67-68, 117–133.
Rasmussen, E. N., 2003: Refined supercell and tornado forecast parameters. Wea. Forecasting, 18, 530–535.
back to Christoph….

42. Using parameters:
A scenario for a weather pattern associated with “critical” values
In collaboration with Lars Lowinski (Meteos Munich) a scenario was designed that is characterized by “critical” values of mentioned parameters.
This scenario is based upon the synoptic situation of four tornado outbreaks over Central Europe:
Aug. 1st, 1925 (NL, five tornadoes, one F4)
June 1st, 1927 (northwestern GER, four F3/F4 tornadoes)
June 24th, 1967 (northern F, F4/F5 tornadoes)
June 25th, 1967 (NL, four F3/F4 tornadoes)

43. Using parameters:
A scenario for a weather pattern associated with “critical” values T H
592
584
576
568
560
552
500 hPa level
High geopotential over southern Europe due to well-mixed airmass originating from Atlas mountains
Strong upper SW-erly jet streak coupled with negatively tilted short-wave trough

44. Using parameters:
A scenario for a weather pattern associated with “critical” values
1015
1020
1010 L H
1005
Surface chart
Frontal boundary with embedded frontal waves from Iberian Peninsula to northern Germany
Easterly surface winds over Germany south of Scandinavian surface high pressure system

45. A scenario for a weather pattern associated with “critical” values
Using parameters:
A scenario for a weather pattern associated with “critical” values 31 14 27 22 19 16
moist maritime airmass north of the warm front
rich low-level moisture underneath an inversion north of convergence line
well-mixed airmass south of convergence line

46. A scenario for a weather pattern associated with “critical” values
Using parameters:
A scenario for a weather pattern associated with “critical” values 31 14 27 22 19 16
Warm sector north of the convergence zone:
CAPE
winds veer strongly with height
strong low-level wind shear
maybe low LFC heights
quasigeostrophic forcing due to WAA and DCVA

47. Using parameters:
A scenario for a weather pattern associated with “critical” values
1020
1015
1010 L H
1005
Would this scenario be associated with a tornado outbreak?

48. Using parameters:
A scenario for a weather pattern associated with “critical” values
1020
1015
1010 L H
1005
Would this scenario be associated with a tornado outbreak?
We don’t know.
Tornadogenesis is not well understood.
Probably, this scenario is associated with an enhanced chance for tornadoes.

49. Using parameters:
23th June, 2004
Estofex
Christian Schöps

50. 23 June, 2004: 500 hPa height, wind speed

51. 23 June, 2004: 850 hPa height, theta-e

52. 23 June, 2004: MUCAPE, deep layer wind shear

53. 23 June, 2004: MUCAPE, low level wind shear

54. 23 June, 2004: LCL height

55. 23 June, 2004: LFC height

56. Soundings from north-central Germany
Soundings from north-central Germany. Proximity soundings were not available. Soundings indicate...
rather weak CAPE
winds veer strongly with height
strong low level wind shear
rather low LFC heights
Note: Models did indicate
SW-erly surface winds

57. Conclusions
Sounding information is essential for convective forecasts.

58. Conclusions
Sounding information is essential for convective forecasts.
Parameters derived from model soundings give a good overview when plotted on maps.

59. Conclusions
Sounding information is essential for convective forecasts.
Parameters derived from model soundings give a good overview when plotted on maps.
They make it easy to compare different models or model runs.

60. Conclusions
Sounding information is essential for convective forecasts.
Parameters derived from model soundings give a good overview when plotted on maps.
They make it easy to compare different models or model runs.
Parameters without physical meaning are not used by Estofex. Learning “magical numbers” associated with complex variables won’t increase our knowledge about tornado forecasting.