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

Observations of Near-Surface Thermodynamic and Wind Shear

Profiles on Significant Tornado Days

Photo Credit: Ming Ying WeiPhoto Credit: Ming Ying Wei

NWS Duluth MinnesotaNWS Duluth MinnesotaGreat Lakes Operational Meteorology Workshop – Toronto, OnrarioGreat Lakes Operational Meteorology Workshop – Toronto, Onrario 22 March 201022 March 2010

Dan MillerScience and Operations OfficerNWS/WFO Duluth, Minnesota

Dan MillerScience and Operations OfficerNWS/WFO Duluth, Minnesota

Some Preliminary Thoughts…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!

Which VWP/Hodo is “Better” for Tornadoes?Which VWP/Hodo is “Better” for Tornadoes?Which VWP/Hodo is “Better” for Tornadoes?Which VWP/Hodo is “Better” for Tornadoes?

Lots of 2-3” HailLimited Windno Tornadoes

Lots of 2-3” HailLimited Windno Tornadoes

Multiple CyclicTornadic Supercells

F2-F3 tornadoes

Multiple CyclicTornadic Supercells

F2-F3 tornadoes

Which Sounding is “Better” for Tornadoes?Which Sounding is “Better” for Tornadoes?Which Sounding is “Better” for Tornadoes?Which Sounding is “Better” for Tornadoes?

Multiple long-trackedF3-F5 tornadoes

Classic Supercells

Multiple long-trackedF3-F5 tornadoes

Classic Supercells

Lots of Hail/Wind2 short-lived weak Tornadoes

HP Supercells (strong cold pools)

Lots of Hail/Wind2 short-lived weak Tornadoes

HP Supercells (strong cold pools)

Oklahoma: 3 May 1999Oklahoma: 3 May 1999Oklahoma: 3 May 1999Oklahoma: 3 May 1999

00 UTC 1999 050400 UTC 1999 0504

1000 m agl

350 m agl

350 m agl wind165 @41kt 1000 m agl

Observed StormMotion

SFC Wind160 @17kt

Missouri: 4 May 2003Missouri: 4 May 2003

00 UTC 2004 050300 UTC 2004 0503

1000 m agl

350 m agl

1000 m agl

Observed StormMotion

SFC Wind150 @12kt

350 m agl wind175 @24kt

Northeast Kansas: 4 May 2003Northeast Kansas: 4 May 2003

18 UTC 2003 0504

1000 m agl

360 m agl

1000 m agl

Observed StormMotion

SFC Wind165 @15kt

360 m agl wind180 @35kt

Oklahoma: 8 May 2003Oklahoma: 8 May 2003

00 UTC 2003 050900 UTC 2003 0509

1000 m agl

350 m agl

1000 m agl

Observed StormMotion

SFC Wind160 @13kt

350 m agl wind170 @34kt

Kansas/Oklahoma: 26 April 1991Kansas/Oklahoma: 26 April 1991Kansas/Oklahoma: 26 April 1991Kansas/Oklahoma: 26 April 1991

00 UTC 1991 042700 UTC 1991 0427

1000 m agl

300 m agl

1000 m agl

Observed StormMotion

SFC Wind178 @12kt

350 m agl wind165 @32kt

Ohio/Tennessee: 10 November 2002Ohio/Tennessee: 10 November 2002Ohio/Tennessee: 10 November 2002Ohio/Tennessee: 10 November 2002

00 UTC 2002 111100 UTC 2002 1111

1000 m agl

400 m agl

1000 m agl

Observed StormMotion

SFC Wind180 @17kt

400 m agl wind195 @49kt

Pennsylvania/Ontario: 31 May 1985Pennsylvania/Ontario: 31 May 1985Pennsylvania/Ontario: 31 May 1985Pennsylvania/Ontario: 31 May 1985

00 UTC 1985 060100 UTC 1985 0601

1000 m agl

400 m agl

1000 m agl

Observed StormMotion

SFC Wind195 @15kt

400 m agl wind200 @32kt

Ohio Valley Region: 3 April 1974Ohio Valley Region: 3 April 1974Ohio Valley Region: 3 April 1974Ohio Valley Region: 3 April 1974

00 UTC 1974 040400 UTC 1974 0404

1000 m agl

400 m agl

1000 m agl

Observed StormMotionSFC Wind

185 @15kt

400 m agl wind200 @38kt

Western Tennessee: 2 April 2006Western Tennessee: 2 April 2006Western Tennessee: 2 April 2006Western Tennessee: 2 April 2006

00 UTC 2006 040300 UTC 2006 040300 UTC 2006 040300 UTC 2006 0403

1000 m agl

500 m agl

1000 m agl

Observed StormMotion

SFC Wind207 @16kt

500 m agl wind225 @35kt

Minnesota: 16 June 1992Minnesota: 16 June 1992Minnesota: 16 June 1992Minnesota: 16 June 1992

00 UTC 1992 061700 UTC 1992 0617

1000 m agl

350 m agl

1000 m agl

Observed StormMotion

SFC Wind095 @17kt

350 m agl wind100 @32kt

Edmonton Alberta: 31 July 1987Edmonton Alberta: 31 July 1987Edmonton Alberta: 31 July 1987Edmonton Alberta: 31 July 1987

00 UTC 1987 080100 UTC 1987 080100 UTC 1987 080100 UTC 1987 0801

1000 m agl

450 m agl

1000 m agl

Observed StormMotion

SFC Wind070 @09kt

450 m agl wind081 @18kt

California (Sacramento) – 21 February 2005California (Sacramento) – 21 February 2005California (Sacramento) – 21 February 2005California (Sacramento) – 21 February 2005

21 UTC 2005 022121 UTC 2005 0221

1000 m agl

500 m agl

1000 m agl

Observed StormMotion

SFC Wind340 @10kt

500 m agl wind070 @18kt

Question: Is the “sickle” shape to the hodograph real, or merely an artifact of data sampling?

Question: Is the “sickle” shape to the hodograph real, or merely an artifact of data sampling?

Wind MeasuredBy Radiosonde

Observed hodographObserved hodograph

Surface wind measuredby Anemometer

Question: Is the “sickle” shape to the hodograph real, or merely an artifact of data sampling?

Question: Is the “sickle” shape to the hodograph real, or merely an artifact of data sampling?

1000 m agl190 @18kt

SFC Wind125 @10kt

400 m agl wind135 @18kt

NAM bufr forecast hodographNAM bufr forecast hodograph

Question: Is the “sickle” shape to the hodograph real, or merely an artifact of data sampling?

Question: Is the “sickle” shape to the hodograph real, or merely an artifact of data sampling?

~350 m agl55-60kt outbound

~350 m agl55-60kt outbound

~350 m agl60-65kt inbound

~350 m agl60-65kt inbound

Greensburg KS Event: 5/4/2007Greensburg KS Event: 5/4/2007

Mean Parameters of the 20 Cases:Mean Parameters of the 20 Cases:

Surface Temperature: 76Surface Dewpoint: 68Surface T/Td spread: 7.7Surface Relative Humidity 69%LCL Height (agl): 2630 ft (802 m)LFC Height (agl): 4425 ft (1349 m)CAPE (surface parcel): 3206 j/kgCIN (surface parcel): 34 j/kg

Surface Temperature: 76Surface Dewpoint: 68Surface T/Td spread: 7.7Surface Relative Humidity 69%LCL Height (agl): 2630 ft (802 m)LFC Height (agl): 4425 ft (1349 m)CAPE (surface parcel): 3206 j/kgCIN (surface parcel): 34 j/kg

(2/21/2005 Sacramento Case Not Included)(2/21/2005 Sacramento Case Not Included)

Operational Implications?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?

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?

Probability of tornado (1973-1999)

55 .81 .78 .79 .76 .7150 .78 .77 .76 .75 .72 .70 .64 .6545 .78 .73 .73 .70 .71 .71 .66 .65 .61 .58 .6140 .74 .67 .68 .69 .69 .66 .64 .61 .59 .59 .51 .41 .38

0-1 km 35 .63 .67 .69 .65 .62 .60 .57 .54 .51 .48 .39 .37 .29 .24 .23 .21Shear 30 .62 .61 .60 .58 .56 .53 .48 .44 .43 .38 .34 .29 .26 .21 .18 .18 .17 .16 .14 .09(kts) 25 .56 .58 .57 .56 .51 .48 .45 .41 .38 .33 .30 .29 .25 .21 .17 .16 .14 .12 .12 .11 .10 .11 .16

20 .56 .50 .53 .50 .44 .43 .39 .34 .30 .26 .24 .22 .19 .16 .14 .15 .13 .12 .11 .09 .10 .09 .10 .1015 .43 .42 .45 .39 .36 .32 .28 .25 .21 .19 .18 .16 .14 .14 .13 .12 .11 .11 .11 .09 .09 .09 .0710 .33 .35 .37 .33 .30 .27 .23 .22 .18 .17 .16 .14 .13 .13 .12 .11 .11 .10 .10 .09 .08 .08 .085 .33 .25 .29 .27 .24 .21 .19 .18 .16 .15 .14 .13 .12 .11 .11 .10 .10 .10 .10 .08 .08 .08 .09

125 250 375 500 625 750 875 1000 1125 1250 1375 1500 1625 1750 1875 2000 2125 2250 2375 2500 2625 2750 2875 3000LCL height (m)

From Nordin and Brooks, 2002

Some Important (and Perhaps Troublesome) Questions:Some Important (and Perhaps Troublesome) Questions:

1) What do we mean when we say “elevated” vs. “surface-based” convection?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?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?

Now The Dirty Details:Now The Dirty Details:

All of this critical “stuff” is going on in a VERY shallow near-

surface layer

All of this critical “stuff” is going on in a VERY shallow near-

surface layer

Red = SFC – 400m aglCyan = 400m – 1000m aglLavender = 1000m – 7000 m agl

Red = SFC – 400m aglCyan = 400m – 1000m aglLavender = 1000m – 7000 m agl

Just Exactly How Shallow is this Layer?Just Exactly How Shallow is this Layer?

457 m1500 ft457 m1500 ft

553 m1815 ft553 m1815 ft

Question: Is there a more effective way to examine low-level wind shear? Are We Looking Low Enough?

Question: Is there a more effective way to examine low-level wind shear? Are We Looking Low Enough?

Surface-400mshear vector

Surface-1 kmshear vector

Mean Parameters of the 20 Cases:Mean Parameters of the 20 Cases:Mean Parameters of the 20 Cases:Mean Parameters of the 20 Cases:

Height of hodograph kink agl: 399 mBulk Shear Vector Magnitude (sfc-kink): 18 ktBulk Shear Vector Magnitude (sfc-1 km): 25 ktBulk Shear Vector Ratio: 0.72

Height of hodograph kink agl: 399 mBulk Shear Vector Magnitude (sfc-kink): 18 ktBulk Shear Vector Magnitude (sfc-1 km): 25 ktBulk Shear Vector Ratio: 0.72

(2/21/2005 Sacramento Case Not Included)(2/21/2005 Sacramento Case Not Included)

Central Florida – 25 December 2006Central Florida – 25 December 2006Central Florida – 25 December 2006Central Florida – 25 December 2006

12 UTC 2006 122512 UTC 2006 1225

1000 m agl

300 m agl

1000 m agl

Observed StormMotion

SFC Wind175 @12kt

300 m agl wind175 @39kt

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?

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?

What about the mixed boundary layer?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?

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?

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

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

What are the “correct” parcels with this thermodynamic profile?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?

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

How do we define “surface-based” DMC?How do we define “surface-based” DMC?

Theta-e decreases rapidly with height

Theta-e decreases rapidly with height

Question: What is the importance of surface heating in the contribution to instability on significant tornado days?

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?

How does the atmosphere produce/maintain this thermodynamic profile in the near-surface layer near max heating time?

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?

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?

Implications for NSE Parameters:Implications for NSE Parameters:Implications for NSE Parameters:Implications for NSE Parameters:100 mb Mean-Layer CAPE (MLCAPE)100 mb Mean-Layer CAPE (MLCAPE)

100 mb Mean-Layer CIN (MLCIN)100 mb Mean-Layer CIN (MLCIN)

Lowest 100 mb Lowest 100 mb

Averaging is “safer” - well-mixed BL should have uniform thetae

Averaging is “safer” - well-mixed BL should have uniform thetae

Averaging is dangerous!! - thetae decreases rapidly with height in BL

Averaging is dangerous!! - thetae decreases rapidly with height in BL

Difference in computed CAPE is smallDifference in computed CAPE is small

Difference in computed CAPE can be large - ~1000-2000 j/kg! **(VGP/EHI)**

Difference in computed CAPE can be large - ~1000-2000 j/kg! **(VGP/EHI)**

Implications for NSE Parameters:Implications for NSE Parameters:Implications for NSE Parameters:Implications for NSE Parameters:0-1 km and 0-3 km Energy-Helicity Index (EHI)0-1 km and 0-3 km Energy-Helicity Index (EHI)

0-3 km Vorticity Generation Potential (VGP)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!

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%)?

Might this explain in part why VGP in particular is plagued by high false alarm ratios (>80%)?

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: 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?

Question: Would a systematic search of the historical upper air database also identify null cases?

Climatological Frequency - Hodographs ONLY:Climatological Frequency - Hodographs ONLY:

Final Thought...Final Thought...

Superposition of these profiles appears to be critical – NOT only the

“sickle” hodograph

Superposition of these profiles appears to be critical – NOT only the

“sickle” hodograph

Red = SFC – 400m aglCyan = 400m – 1000m aglLavender = 1000m – 7000 m agl

Red = SFC – 400m aglCyan = 400m – 1000m aglLavender = 1000m – 7000 m agl

AcknowledgementsAcknowledgements

David Andra: NWS/WFO Norman OKMichael Foster: NWS/WFO Norman OKRich Thompson: NWS/SPC Norman OKDr. Bob Conzemius: WindLogics Grand

Rapids MNDr. Bruce Lee: WindLogics Grand Rapids MNDoug Speheger: NWS/WFO Norman OKKevin Scharfenberg: NSSL Norman OKBob Johns: former SOO SPC Norman OKJon Davies: Private Meteorologist Kansas

City MOTodd Lindley: NWS/WFO Lubbock TXDr. Chris Weiss: Texas Tech University

Lubbock TXDr. Matt Bunkers: NWS/WFO Rapid City SDDr. David Blanchard: NWS/WFO Flagstaff AZ

David Andra: NWS/WFO Norman OKMichael Foster: NWS/WFO Norman OKRich Thompson: NWS/SPC Norman OKDr. Bob Conzemius: WindLogics Grand

Rapids MNDr. Bruce Lee: WindLogics Grand Rapids MNDoug Speheger: NWS/WFO Norman OKKevin Scharfenberg: NSSL Norman OKBob Johns: former SOO SPC Norman OKJon Davies: Private Meteorologist Kansas

City MOTodd Lindley: NWS/WFO Lubbock TXDr. Chris Weiss: Texas Tech University

Lubbock TXDr. Matt Bunkers: NWS/WFO Rapid City SDDr. David Blanchard: NWS/WFO Flagstaff AZ

Questions?Questions?

Thanks for your attention!Thanks for your attention!

Photo Credit: Todd LindleyPhoto Credit: Todd Lindley