Environmental Features Discriminating Between High Shear/Low CAPE Severe Convection and Null...

Environmental Features Discriminating Between High Shear/Low CAPE Severe

Convection and Null Events

Keith SherburnMatthew Parker

North Carolina State University

2012 Collaborative Science, Technology, and Applied Research Workshop

16 November 2012

Acknowledgements• AMS/NOAA NWS Graduate Fellowship• CSTAR Program• NOAA Grant NA10NWS4680007

• WFO Collaborators• Storm Prediction Center• Andy Dean• Rich Thompson

• Convective Storms Group

INTRODUCTIONWhat is high shear/low CAPE, and why do we care?

INTRODUCTION• “High” shear

0-6 km layer ≥ 35 knots (18 m/s)

• “Low” CAPE Surface-based parcel ≤ 500 J/kg

HSLC

INTRODUCTION• Tornadoes

<= 500 J/kg MLCAPE

• Significant Tornadoes <= 500 J/kg MLCAPE

Guyer and Dean (2010)

INTRODUCTION

All HSLC Significant Reports from 2006-2011

INTRODUCTION

Storm Prediction Center (SPC)

INTRODUCTION• Research limited to last couple of decades• Many unanswered questions:

Role of mesovortices? Role of rear-inflow jet? Influence of boundaries? Vertical distribution of instability and moisture? Compensation for overall lack of instability? How can we improve the forecasting of

these events?

DATA AND METHODSWhat we have and how we’re using it

DEVELOPMENT DATA• Events subjectively determined by

WFOs, but include majority of HSLC events in region

• SPC Relational Database (SFCOA; aka Mesoanalysis) “nearest neighbor”

• “HSLC Event” – Over half of reports for a CWA were HSLC

• One report per CWA per hour• 80 significant reports

DEVELOPMENT DATA• Nulls were warnings issued on a day

in which no severe reports were received by the WFO issuing the warning

• SFCOA interpolated to latitude, longitude point

• 114 nulls

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

5

10

15

20

25

30

35

40

45

50

Annual Cycle of Reports and Nulls – Development Dataset

Nulls Significant Severe

Month

Perc

enta

ge

VERIFICATION DATA• All significant severe reports across

US from 2006-2011• All nulls, as defined previously, from

Oct. 2006 through 2011• SFCOA nearest neighbor• 2517 HSLC Significant Reports

(275 CSTAR)• 1316 HSLC Nulls (118 CSTAR)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

5

10

15

20

25

30

35

U.S. Annual Cycle of Reports and Nulls - Verification Dataset

Reports % Nulls % Tornadoes % Wind % Hail %

Month

Perc

enta

ge

METHODS• Statistical analyses• Skill scores– True Skill Statistic:– TSS = (ad-bc)/[(a+c)(b+d)] ~ POD – FA

Rate– a: Hit, b: False Alarm, c: Miss, d: Correct

Null• Box-and-whisker plots

RESULTSWhat we’ve found so far

1

RESULTS

HSLC CONVECTIO

N

SIGNIFICANT EVENTS

NULLS

SIGNIFICANT TORNADOES

SIGNIFICANT WINDS

2

1SEVERE HAZARDS IN

ENVIRONMENTS WITH REDUCED BUOYANCY

PARAMETER:SHERB = (0-3 km shear magnitude / 25 m s-1) * (0-3 km lapse rate / 5.2 K km-1) * (700-500 mb lapse rate / 5.8 K km-1)

EFFECTIVE SHEAR VERSION:SHERBE = (Effective shear magnitude / 26 m s-1) * (0-3 km lapse rate / 5.2 K km-1) * (700-500 mb lapse rate / 5.8 K km-1)

0 0.10.20.30.40.50.60.70.80.9 1 1.11.21.31.41.51.61.71.81.9 2 2.12.22.32.42.50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

True Skill Statistic: Our Domain HSLC Significant Events vs. Nulls

Parameter Threshold Value

True

Ski

ll St

atis

tic

SHERBESHERBSTPSCPCraven-BrooksVGPEHI

0 0.10.20.30.40.50.60.70.80.9 1 1.11.21.31.41.51.61.71.81.9 2 2.12.22.32.42.50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

True Skill Statistic: Our Domain HSLC Signif -icant Tornadoes vs. Nulls


True

Ski

ll St

atis

tic


0 0.10.20.30.40.50.60.70.80.9 1 1.11.21.31.41.51.61.71.81.9 2 2.12.22.32.42.50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

True Skill Statistic: All US HSLC Signif -icant Events vs. Nulls


True

Ski

ll St

atis

tic


0 0.10.20.30.40.50.60.70.80.9 1 1.11.21.31.41.51.61.71.81.9 2 2.12.22.32.42.50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

True Skill Statistic: All US HSLC Signif -icant Tornadoes vs. Nulls


True

Ski

ll St

atis

tic


123456

7891011

30 S63 N

95 S72 N

374 S134 N

300 S96 N

76 S68 N

18 S23 N

4 S39 N

19 S38 N

414 S201 N

876 S417 N

306 S168 N

123456

7891011

2 T28 W5 H

16 T64 W15 H

13 T229 W132 H

7 T164 W129 H

1 T62 W13 H

2 T16 W0 H

0 T4 W0 H 2 T

15 W2 H

7 T253 W154 H

188 T555 W133 H

64 T189 W53 H

123456

7891011

SCP

SHERBE

SCPEHISHERBSHERB

Craven-Brooks/EHI/SCP

SHERB/EHI

SHERBESHERB

SHERB

FUTURE WORKWhere do we go from here?

FUTURE WORKIDEALIZED

SIMULATIONS• Hypothesis testing• Bryan’s Cloud Model 1

(CM1)• Using composite soundings

COMPOSITE PARAMETERS• Test real-time• Evaluate differences

by region• Other formulations

storms.meas.ncsu.edu/users/mdparker/nam/

CONCLUSIONS

CONCLUSIONS• HSLC a forecast problem in SE/Mid-

Atlantic• Significant tornadoes need high

shear, but what about CAPE?• Our composite parameters show an

improvement in skill over existing parameters for our CSTAR region

EXTRA SLIDES

1 2 3 4 5 6 7 8 9 10 11 US0

0.1

0.2

0.3

0.4

0.5

0.6

All HSLC: Optimal Composite Parameter Skill by Region

Region

True

Ski

ll St

atis

tic


123456

7810 911

1 2 3 4 5 6 7 8 9 10 11 US0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

HSLC Tor: Optimal Composite Parameter Skill by Region

Region

True

Ski

ll St

atis

tic


123456

7810 911

1• 35 HSLC Significant Events• 60 HSLC Nulls

• SHERB optimal:• TSS = 0.257 @ 0.59

• SHERBE optimal:• TSS = 0.286 @ 0.77

• Best composite parameter:• SCP = 0.469 @ 1.25

1• SHERB/E Component Optimal TSS:• ESHR = 0.317 @ 37 kts• S3MG = 0.360 @ 23.5 kts• LLLR = 0.200 @ 3.3 K km-1

• LR75 = 0.050 @ 4.8 K km-1

• Max Individual TSS:• M5CP = 0.489 @ 350 J kg-1

• 50 mb mixed-layer CAPE

2• 95 Significant Events• 72 Nulls



• Best composite parameter:• SHERBE


• LR75 = 0.046 @ 7.3 K km-1

• Max Individual TSS:• ESHR




• Best composite parameter:• SCP = 0.360 @ 2.42


• LR75 = 0.253 @ 6.8 K km-1





• Best composite parameter:• EHI3M1* = 0.443 @ 0.95

*0-3 km SRH and 100 mb mixed CAPE


• LR75 = 0.147 @ 7.2 K km-1

• Max Individual TSS:• M1MX = 0.406 @ 11 g kg-1

• 100 mb mean mixing ratio




• Best composite parameter:• SHERB

5• SHERB/E Component Optimal TSS:• ESHR = 0.168 @ 38 kts• S3MG = 0.195 @ 27 kts• LLLR = 0.064 @ 6.7 K km-1

• LR75 = 0.060 @ 6.3 K km-1

• Max Individual TSS:• S1MG = 0.310 @ 15 kts• 0-1 km shear magnitude• NLFH = 0.441 @ 3800 m• Non-virtual LFC height (higher

for events)






• LR75 = 0.000 @ 5.3 K km-1

• Max Individual TSS:• MUCN = 0.639 @ -40 J kg-1

• Most Unstable CIN• S8MG = 0.693 @ 67 kts• 0-8 km shear magnitude






• LR75 = 0.282 @ 5.8 K km-1







• LR75 = 0.111 @ 6.1 K km-1





• Best composite parameter:• SHERBE


• LR75 = 0.119 @ 6.1 K km-1





• Best composite parameter:• SHERB/EHI


• LR75 = 0.053 @ 8.5 K km-1

• Max Individual TSS:• SRH3 = 0.605 @ 200 m2s-2



• SHERBE optimal:• TSS = 0.000

• Best composite parameter:• SCP = 0.250 @ 0.41• EHI = 0.250 @ 0.52/0.45• CBSS = 0.250 @ 10000


• LR75 = 0.154 @ 5.8 K km-1

• Max Individual TSS:• INPW = 0.769 @ 0.9”• Precipitable water

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Environmental Features Discriminating Between High Shear/Low CAPE Severe Convection and Null...

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