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

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

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

Page 2: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

http://physics.uwstout.edu/wx/Notes/

Introduction A: Importance of sounding information doing convective forecasts

Page 3: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

Page 4: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

CAPE

Page 5: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

CAPECIN

Page 6: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

CAPECINSBCAPE

Page 7: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

CAPECINSBCAPE

Page 8: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

CAPECINSBCAPEMUCAPE

Page 9: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

CAPECINSBCAPEMUCAPELCL

Page 10: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

CAPECINSBCAPEMUCAPELCLLFC

Page 11: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

Page 12: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

CAPECINSBCAPE

CAPECIN ~ 0 J/kgSBCAPEMUCAPE

Page 13: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

CAPECINSBCAPEMUCAPELCL

Page 14: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction B: Sounding-derived parameters using parcel-theory

CAPECINSBCAPEMUCAPELCLLFC

Page 15: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction C: Sounding-derived parameters in horizontal forecast charts

Is it useful to use them on horizontal maps?

Page 16: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

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:

Page 17: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

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.

Page 18: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

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.

Page 19: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

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.

Page 20: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction C: Sounding-derived parameters in horizontal forecast charts

Complex parameters using “significant” levels

• Total totals index (TOTL) = T850 + Td850 - 2 * T500 [°C]

• K index = T850 + Td850 - T500 - (T-Td)700 [°C]

• Sweat index = 12*Td850+20*(TOTL-49)+2*U850+5*U500+125*(0.2+sinf) where f=(wind direction500-wind direction850), U=wind speed[kts], TOTL=0 if TOTL<49

Page 21: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Introduction C: Sounding-derived parameters in horizontal forecast charts

Complex parameters using significant levels• Total totals index (TOTL) = T850 + Td850 - 2 * T500 [°C]

• K index = T850 + Td850 - T500 - (T-Td)700 [°C]

• Sweat index = 12*Td850+20*(TOTL-49)+2*U850+5*U500+125*(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.

Page 22: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

“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.

Page 23: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Sounding-derived parameters associated with large hail and tornadoes in the NetherlandsPieter Groenemeijer (IMAU; ESTOFEX), Aarnout van Delden (IMAU)

F3 tornado near Deil, 25-06-1967. (A.C. Frenks)

Page 24: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

study done at Institute for Marine and Atmospheric Research Utrecht

Sounding-derived parameters associated with large hail and tornadoes in the Netherlands

Page 25: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

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?

Page 26: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Basic idea

1. Find soundings taken in the proximity of severe weather events (here: tornadoes)

2. 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

Page 27: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Proximity soundings

What is a proximity sounding…?

Used definition:• within 4 hours of the sounding

(before or after)

• within 100 km from a point thatis advected by the 0-3 km meanwind from the sounding locationat the sounding time

Page 28: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

• radiosonde observations

Dec 1975 – Aug 2003

(thanks to KNMI, DWD, KMI)

• severe weather reports from Dutch voluntary observers (VWK)

Data sets

Sinds 1974

Vereniging voor Weerkunde en Klimatologie (VWK)

http:/www.vwkweb.nl

Page 29: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Data

soundings associated with: number

hail (2.0 - 2.9 cm)

hail (>= 3.0 cm)

tornadoes F0

tornadoes F1

tornadoes F2

waterspouts

thunder (1990-2000 only)

46

47

24

37

6

26

2045

all soundings 67816

Page 30: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

results…

Page 31: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Most-unstable CAPE (MUCAPE)Number of events

maximum

median

75th perc.

25th perc.

MUCAPE not very high with tornadoes…

US studies: MUCAPE highly variable with tornadoes. Strong tornadoes may occur with low CAPE when shear is high

Page 32: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Most-unstable CAPE released below 3 km A.G.L.

MUCAPE<3km high with F0, not with F1+

US studies: Davies (2004) has found a relation between tornado occurrence and high CAPE below 3km (in his study M.L.CAPE)...

Page 33: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

(most-unstable) LFC height (m)

LFC relatively low with tornadoes (esp. F0)…

US studies: Davies (2004) has found a relation between low LFC and tornado occurrence

Page 34: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

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

Page 35: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

LARGE HAIL F0 F1+

Average soundings

note the distribution of parcel buoyancy with height

Page 36: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

0-6 km A.G.L. bulk shear (m/s)

0-6 km bulk shear high with F2 tornadoes

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

Page 37: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

0-1 km A.G.L. bulk shear (m/s)

0-1 km shear high with F1, esp. F2 tornadoes..

US studies: strong 0-1 km shear favours for sign. tornadoes (e.g. Craven et al., 2002).

Page 38: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

0-1 km A.G.L. storm-relative helicity (m2/s2)

0-1 km shear high with F1, esp. F2 tornadoes..

US studies: high values favor supercell tornadoes (e.g. Rasmussen, 2003).

Page 39: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

• 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..

Some conclusions

Page 40: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

• 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

Some conclusions

Page 41: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

back to Christoph….

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.

Page 42: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

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)

Page 43: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Using parameters:A scenario for a weather pattern associated with “critical” values

T

H592

584

576

568560

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

Page 44: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Using parameters:A scenario for a weather pattern associated with “critical” values

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

1015

1020

1015

1010

1010

L

L

H

H

1005

Page 45: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Using parameters:A scenario for a weather pattern associated with “critical” values

3114

2722

1916

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

Page 46: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Using parameters:A scenario for a weather pattern associated with “critical” values

3114

2722

1916

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

Page 47: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Using parameters:A scenario for a weather pattern associated with “critical” values

Would this scenario be associated with a tornado outbreak?

1020

1015

1010

1010

L

L

H

H

1005

Page 48: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Using parameters:A scenario for a weather pattern associated with “critical” values

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.

1020

1015

1010

1010

L

L

H

H

1005

Page 49: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Using parameters:23th June, 2004

Christian Schöps

Estofex

Page 50: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

23 June, 2004: 500 hPa height, wind speed

Page 51: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

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

Page 52: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

23 June, 2004: MUCAPE, deep layer wind shear

Page 53: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

23 June, 2004: MUCAPE, low level wind shear

Page 54: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

23 June, 2004: LCL height

Page 55: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

23 June, 2004: LFC height

Page 56: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

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

Page 57: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Conclusions

• Sounding information is essential for convective forecasts.

Page 58: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

Conclusions

• Sounding information is essential for convective forecasts.

• Parameters derived from model soundings give a good overview when plotted on maps.

Page 59: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

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.

Page 60: Gatzen, Groenemeijer: Forecasting tornadoes using model- and sounding derived parameters.

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.


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