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A Study on Convective Modes Associated with...
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A Study on Convective Modes Associated with Tornadoes in Central New York and Northeast Pennsylvania Timothy W. Humphrey 1 Michael Evans 2 1 Department of Atmospheric and Environmental Sciences, University at Albany State University of New York, Albany, New York 2 NOAA/NWS, Weather Forecast Office, Binghamton, New York
Transcript of A Study on Convective Modes Associated with...
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
• Climatology • Storm Environments • Null Events • Radar Study • Conclusions
Climatology
52 Tornadoes 2000 – May 2011
2 0 1
13
44
36 34
20
13
3 6
3 0
5
10
15
20
25
30
35
40
45
50
Month of Tornado Occurrence 1950 - 2011
0 0 0
10
15
6
11
4
1 0
2 3
0
2
4
6
8
10
12
14
16
Month of Tornado Occurrence 2000 - 2011
Number ofTornadoes
2 1 1 1
0 1 1
2 2
0 1
0 0 0 0 0 1
2 2 3
11
8
6 7
0
2
4
6
8
10
12
00:00UTC
01:00UTC
02:00UTC
03:00UTC
04:00UTC
05:00UTC
06:00UTC
07:00UTC
08:00UTC
09:00UTC
10:00UTC
11:00UTC
12:00UTC
13:00UTC
14:00UTC
15:00UTC
16:00UTC
17:00UTC
18:00UTC
19:00UTC
20:00UTC
21:00UTC
22:00UTC
23:00UTC
Time of Tornado Occurrence 2000 - 2011
23
8 8 6
0 1 1 4 3
1 1 0 0 1 1 4
2 6
11 11
24 27
22
15
0
5
10
15
20
25
30
00:00UTC
01:00UTC
02:00UTC
03:00UTC
04:00UTC
05:00UTC
06:00UTC
07:00UTC
08:00UTC
09:00UTC
10:00UTC
11:00UTC
12:00UTC
13:00UTC
14:00UTC
15:00UTC
16:00UTC
17:00UTC
18:00UTC
19:00UTC
20:00UTC
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22:00UTC
23:00UTC
1950 - 2011
7
Supercell QLCS
Multicell Cellular
Tornadoes by Convective Mode 2000 - 2011
28, 54%
16, 31%
5, 9% 3, 6%
Supercell
QLCS
Multicell
Cellular
Storm Environment
• Synoptic Environment (2000 – 2011)
– NOAA Earth System Research Laboratory
• Mesoscale Environment (2005 – 2011) – Storm Prediction Center (SPC) Mesoanalysis
Archive
10
Supercell 300 hPa Height and Anomaly
11
QLCS 300hPa Height and Anomaly
Mesoscale Environment
• SPC Mesoanalysis Archive (2005-2011)
• 36 Tornado Events
• 19 Thermodynamic, Shear, & Composite Parameters
0
500
1000
1500
2000
2500
Supercell QLCS Multicell
Joul
es/k
ilogr
am (J
/kg)
Surface Based CAPE By Convective Mode
Median
Min
Max
0
10
20
30
40
50
60
70
80
90
100
Supercell QLCS Multicell
Knot
s (kt
) 0 – 6 km Bulk Shear
Median
Min
Max
0
1
2
3
4
5
6
7
8
Supercell QLCS Multicell
EHI
0 – 3km Energy-Helicity Index (EHI)
Median
Min
Max
Storm Environment
16
CAPE LCL Height Shear Helicity
Supercell
Moderate
Low
Moderate
Moderate
Multicell
Moderate
Low
Low
Moderate
QLCS
Low
Low
High
High
Null Events
Iowa Environmental Mesonet (IEM) Cow Application
21 Null Events
0
100
200
300
400
500
600
Verified Null
Met
ers ^
2/
Seco
nds ^
2 (m
^2/s
^2)
Supercell 0 – 1 km SRH
Median
Min
Max
Radar Study
Rotational Velocity (Vr)
Shear
Spectrum Width
Normalized Rotation (NROT)
Supercells
5
10
15
20
25
30
35
T-9 T-8 T-7 T-6 T-5 T-4 T-3 T-2 T-1 T-0
Vr (k
ts)
Verified Median Rotational Velocity (Vr)
.5 Delta V
.9 Delta V1.4 Delta V1.9 Delta
5
10
15
20
25
30
35
T-10 T-9 T-8 T-7 T-6 T-5 T-4 T-3 T-2 T-1 T-0
Vr (k
ts)
Null Median Vr
.5 Delta V
.9 Delta V1.4 Delta V1.9 Delta
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
T-9 T-8 T-7 T-6 T-5 T-4 T-3 T-2 T-1 T-0
Shea
r (s^
-1)
Verified Median Shear
.5 Shear
.9 Shear1.4 Shear1.9 Shear
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
T-10 T-9 T-8 T-7 T-6 T-5 T-4 T-3 T-2 T-1 T-0
Shea
r (s^
-1)
Null Median Shear
.5 Shear
.9 Shear1.4 Shear1.9 Shear
QLCSs
0
5
10
15
20
25
30
35
40
T-5 T-4 T-3 T-2 T-1 T-0
Vr (k
ts)
Verified Median Vr
.5 Vr
.9 Vr
1.4 Vr
1.9 Vr
0
5
10
15
20
25
30
35
40
T-8 T-7 T-6 T-5 T-4 T-3 T-2 T-1 T-0
Vr (k
ts)
Null Median Vr
.5 Vr
.9 Vr1.4 Vr1.9 Vr
0
0.005
0.01
0.015
0.02
0.025
T-5 T-4 T-3 T-2 T-1 T-0
Shea
r (s^
-1)
Verified Median Shear
.5 Shear
.9 Shear1.4 Shear1.9 Shear
0
0.005
0.01
0.015
0.02
0.025
T-8 T-7 T-6 T-5 T-4 T-3 T-2 T-1 T-0
Shea
r (s^
-1)
Null Median Shear
.5 Shear
.9 Shear1.4 Shear1.9 Shear
Supercells QLCSs
Rotation “spins down” to the surface
Uniform shear in
lowest elevation angles
Low level rotation: ~20 min
Rotation “spins up” from surface
Spikes in shear in
lowest elevation angles
Low level rotation: ~12 min
Supercell Rotational Velocity (Vr)
0
10
20
30
40
50
60
0 100 200 300 400 500
0.5
nm V
r (kt
s)
0 - 1 km SRH (m^2 / s^2)
VerifiedNull
QLCS Rotational Velocity (Vr)
0
10
20
30
40
50
60
0 100 200 300 400 500 600 700 800
0.5
nm V
r (kt
s)
0 - 1 km SRH (m^2 / s^2)
VerifiedNull
0
10
20
30
40
50
60
0 100 200 300 400 500 600 700
0.5
nm V
r (kt
s)
0 - 1 km SRH (m^2 / s^2)
VerifiedNull
Supercell/QLCS Vr
Conclusions
• Majority of tornadoes associated with supercells • Supercell tornadoes appeared dependent on
mesoscale conditions • QLCS had little difference in mesoscale conditions
• Low level helicity a good discriminator between
verified and null events
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.
