A Study on Convective Modes Associated with Tornadoes in Central New York and Northeast

Pennsylvania

Timothy W. Humphrey1

Michael Evans2

1Department of Atmospheric and Environmental Sciences, University at Albany

State University of New York, Albany, New York 2NOAA/NWS, Weather Forecast Office, Binghamton, New York

Outline

• Motivation• Climatology• Storm Environments• Null Events• Radar Study• Conclusions

Motivation

• Enhance knowledge of tornado environments

• Improve forecasting and warning of tornadoes

• Communicate tornado risk

Climatology

52 TornadoesJanuary 2000 – May 2011

January

Febru

ary

March April

May

JuneJuly

August

September

October

November

December

0

5

10

15

20

25

30

35

40

45

50

2 0 1

13

44

36 34

20

13

36

3

Month of Tornado Occurrence1950 - 2011

January

Febru

ary

March April

May

JuneJuly

August

September

October

November

December

0

2

4

6

8

10

12

14

16

0 0 0

10

15

6

11

4

10

23

Month of Tornado Occurrence2000 - 2011

Number of Tornadoes

Polynomial (Number of Tornadoes)

00:00 UTC

01:00 UTC

02:00 UTC

03:00 UTC

04:00 UTC

05:00 UTC

06:00 UTC

07:00 UTC

08:00 UTC

09:00 UTC

10:00 UTC

11:00 UTC

12:00 UTC

13:00 UTC

14:00 UTC

15:00 UTC

16:00 UTC

17:00 UTC

18:00 UTC

19:00 UTC

20:00 UTC

21:00 UTC

22:00 UTC

23:00 UTC

0

2

4

6

8

10

12

21 1 1

01 1

2 2

01

0 0 0 0 01

2 23

11

8

67

Time of Tornado Occurrence2000 - 2011

00:00 UTC

01:00 UTC

02:00 UTC

03:00 UTC

04:00 UTC

05:00 UTC

06:00 UTC

07:00 UTC

08:00 UTC

09:00 UTC

10:00 UTC

11:00 UTC

12:00 UTC

13:00 UTC

14:00 UTC

15:00 UTC

16:00 UTC

17:00 UTC

18:00 UTC

19:00 UTC

20:00 UTC

21:00 UTC

22:00 UTC

23:00 UTC

0

5

10

15

20

25

30

23

8 86

0 1 14 3

1 1 0 0 1 14

26

11 11

2427

22

15

1950 - 2011

7

Supercell QLCS

Multicell Cellular

24 Jun 2004 28 Apr 2011

29 Jul 2006 17 May 2008

Tornadoes by Convective Mode2000 - 2011

54%

31%

10% 6%

Supercell

QLCS

Multicell

Cellular

(28)

(16)

(5)

(3)

N = 52

Storm Environment

• Synoptic environment (2000 – 2011)– NOAA Earth System Research Laboratory

(ESRL)

• Mesoscale environment (2005 – 2011)– Storm Prediction Center (SPC) Mesoanalysis

Archive

10

Supercell 300 hPa Height (m) and Anomaly (m)

N =

11

QLCS 300hPa Height (m) and Anomaly (m)

Mesoscale Environment

• SPC Mesoanalysis Archive (2005-2011)

• 36 Tornado Events

• 19 Thermodynamic, Shear, & Composite Parameters

Supercell QLCS Multicell0

500

1000

1500

2000

2500Surface Based CAPE By Convective Mode

Median

Min

Max

Joul

es/k

ilogr

am (J

/kg)

Supercell QLCS Multicell0

10

20

30

40

50

60

70

80

90

100

0 – 6 km Bulk Shear

Median

Min

MaxKnot

s (k

t)

Supercell QLCS Multicell0

1

2

3

4

5

6

7

80 – 3km Energy-Helicity Index (EHI)

Median

Min

Max

EHI

Null Events

Iowa Environmental Mesonet(IEM) Cow Application

Identified unverified Tornado warnings (2005-2011)

21 Null Events

Verified Null0

100

200

300

400

500

600

Supercell 0 – 1 km SRH

Median

Min

Max

Met

ers

^ 2/

Sec

onds

^ 2

(m^2

/s^2

)

Radar Study

Rotational Velocity (Vr)

Shear

Spectrum Width

Normalized Rotation(NROT)

Supercells QLCSs

Rotation “spins down” to the surface

Uniform horizontal shear in lowest elevation angles

Low level rotation:~20 min

Rotation “spins up” from surface

Spikes in horizontal shear in lowest elevation angles

Low level rotation:~12 min

Supercell Rotational Velocity (Vr)

0 50 100 150 200 250 300 350 400 450 5000

10

20

30

40

50

60

VerifiedNull

0 - 1 km SRH (m^2 / s^2)

0.5

nm V

r (kt

s)

QLCS Rotational Velocity (Vr)

100 150 200 250 300 350 400 450 500 550 6000

2

4

6

8

10

12

VerifiedNull

0 - 1 km SRH (m^2 / s^2)

0.5

nm V

r (kt

s)

0 100 200 300 400 500 600 7000

5

10

15

20

25

30

35

40

VerifiedNull

0 - 1 km SRH (m^2 / s^2)

0.5

nm V

r (kt

s)Supercell/QLCS Vr

Conclusions

• Majority of tornadoes associated with supercells

• Supercell tornadoes appeared dependent on low level helicity and bulk shear

• QLCSs had little difference in mesoscale conditions

• Low level helicity a potential discriminator between verified and null events

Acknowledgments:

Hollings Scholarship Program

Michael Evans

NWS Binghamton Staff

Brook Taber, NWS Burlington

References:Thompson, R.L., R Edwards, J.A. Hart, K.L. Elmore, and

P. Markowski, 2003: Close proximity soundings within supercell environments obtained from the Rapid Update Cycle. Wea. Forecasting, 18, 1243-1261.

Trapp, R.J., S. A. Tessendorf, E. S. Godfrey, and H. E. Brooks, 2005: Tornadoes from squall lines and bow echoes. Part I: Climatological distribution. Wea. Forecasting, 20, 23–34.

http://www.erh.noaa.gov/bgm/research.shtml

Questions?

thumphrey@albany.edu