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