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A%20Review%20of%20a%20Rare%20Classic%20Supercell%20in%20Northern%20Indiana%20and%20Possible%20Explanations%20for%20Tornadogenesis%20Failure

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Title: A%20Review%20of%20a%20Rare%20Classic%20Supercell%20in%20Northern%20Indiana%20and%20Possible%20Explanations%20for%20Tornadogenesis%20Failure


1
A Review of a Rare Classic Supercell in Northern
Indiana and Possible Explanations for
Tornadogenesis Failure
  • B.J. Simpson
  • NWS Northern Indiana

2
Brief Summary
  • Isolated supercell developed between two separate
    boundaries left behind by earlier convection
  • Supercell became deviant along and just north of
    one of the boundaries staying attached for nearly
    2.5 hours
  • In spite of 4000 J/kg MLCAPE and assumed
    horizontal vorticity augmentation along the
    boundary, supercell did not produce a single
    tornado

3
Reasons for Study
  • Very few classic supercells develop or move
    into the KIWX CWA
  • Most tornadoes in the KIWX CWA form in QLCS or
    low topped convection
  • So why wouldnt a rare textbook supercell riding
    just north of a well defined boundary produce a
    tornado?

4
Storm Lifecycle Loop
5
Pre-Storm Environment
  • Several important synoptic and mesoscale factors
    came together that led to supercell development
    the afternoon of June 19th.

6
Water Vapor/500mb Heights/Winds
7
June 19 Radar Mosaic
8
Visible Satellite
9
20 UTC MLCAPE RUC Mesoanalysis
10
20 UTC 0-6 km Shear RUC Mesoanalysis
11
20 UTC 0-1 km Shear RUC Mesoanalysis
12
21 UTC 0-1 km SRH RUC Mesoanalysis
13
LAPS Proximity Sounding (Adjusted to Reflect
Surface Conditions South of the Boundary)
14
0.5 Degree Reflectivity
1957 UTC
15
0.5 Degree Reflectivity
2001 UTC
16
0.5 Degree Reflectivity
2006 UTC
17
0.5 Degree Reflectivity
2011 UTC
18
LAPS Surface Theta E Observations
2011 UTC
350K Surface Theta E
364K Surface Theta E
19
0.5 Degree Reflectivity
2016 UTC
20
0.5 Degree Reflectivity
2021 UTC
Mainly Crosswise Ingestion of Horizontal
Convective Rolls
21
0.5 Degree Reflectivity
2025 UTC
22
0.5 Degree Reflectivity
2030 UTC
23
0.5 Degree Reflectivity
2034 UTC
24
5.1 Degree Reflectivity
2034 UTC
Donut Hole
25
0.5 Degree Reflectivity
2039 UTC
26
0.5 Degree Reflectivity
2044 UTC
High Theta E Airmass MLCAPES gt 3000 J/kg LCLs gt
1300 m 0-1 SRH lt 50 m²/s²
27
LAPS Surface Theta E Observations
2044 UTC
Directionally Favorable Yet Weak Low Level Inflow
28
2044 UTC Storm Relative Motion
0.5
1.3
20 kts VR-Shear at 4900 ft
2.4
3.1
87 kts Gate to Gate at 9700 ft
29
Why No Tornado Yet?
  • 3 Main Reasons
  • Storm was still organizing, mid level mesocyclone
    had not built down toward surface
  • Ambient low level SRH/0-1 km shear values were
    not impressive
  • LCLs were near 1400 meters on the south side of
    the boundary

30
LCL Importance
19 June 2009 Supercell
Thompson and Edwards 2000
31
0-1 km Shear vs. LCL heights
19 June 2009 Supercell
Brooks and Craven 2002
32
Any Hail in this Storm??
Three Body Scatter Spike
71 dBZ _at_ 34,391 ft!
33
How Bout this Core?
-20 C Level
Freezing Level
Pink 60 dBZ
This Storm had 53 dBZ _at_ 52,400 feet!
34
BAM!
Measured 4.5 (SOFTBALL) Size Hail
Photo Courtesy Thomas Hayden
35
0.5 Degree Reflectivity
2048 UTC
36
0.5 Degree Reflectivity
2053 UTC
37
2053 UTC Storm Relative Motion
0.5
1.3
17 kts VR-Shear at 4800 ft
2.4
3.1
38
0.5 Degree Reflectivity
2057 UTC
39
0.5 Degree Reflectivity
2102 UTC
40
2102 UTC Storm Relative Motion
0.5
1.3
30 kts VR-Shear at 4600 ft
2.4
3.1
41
0.5 Degree Reflectivity
2106 UTC
Outflow Boundary Continues to Move Southwest
42
2106 UTC Storm Relative Motion
0.5
1.3
30 kts VR-Shear at 4600 ft
20 kts VR-Shear at 2600 ft
2.4
3.1
43
0.5 Degree Reflectivity
2111 UTC
44
Storm Crosses Boundary
  • Now this supercell will exist in an entirely
    different environment
  • An environment characterized by
  • Enhanced horizontal vorticity generated by
    outflow boundary
  • Much lower LCLs
  • HoweverMuch lower CAPE values

45
LAPS Proximity Sounding (Adjusted to Reflect
Surface Conditions North of the Boundary)
46
Conceptual Model Storm Crossing Boundary
Markowski, et al. (1998)
47
Boundary Related Research
70 of VORTEX-95 Tornadoes Occurred Along
Pre-Existing Boundaries
Markowski, et al. (1998)
48
Storm Crosses Boundary
  • Sohere we gothe big show This supercell has to
    produce a tornado once it moves to the immediate
    north side of the boundary, right??
  • Dont You Think?
  • Wrong!!
  • Why not?

49
0.5 Degree Reflectivity
2111 UTC
50
0.5 Degree Reflectivity
2116 UTC
51
0.5 Degree Reflectivity
2120 UTC
52
0.5 Degree Reflectivity
2125 UTC
53
0.5 Degree Reflectivity
2129 UTC
54
0.5 Degree Reflectivity
2134 UTC
55
0.5 Degree Reflectivity
2138 UTC
56
0.5 Degree Reflectivity
2143 UTC
57
LAPS Surface Theta E Observations
2143 UTC
15 knot storm motion
Lack of low level flow to be ingested by the
supercell
58
2143 UTC Storm Relative Motion
0.5
1.3
15 kts VR-Shear at 4800 ft
2.4
3.1
59
2143 UTC Visual Appearance (Looking North)
2143 UTC
60
0.5 Degree Reflectivity
2148 UTC
61
0.5 Degree Reflectivity
2152 UTC
62
0.5 Degree Reflectivity
2157 UTC
63
2157 UTC Storm Relative Motion
0.5
1.3
20 kts VR-Shear at 5100 ft
2.4
3.1
64
2157 UTC Visual Appearance (Looking East
Northeast)
2157 UTC
65
0.5 Degree Reflectivity
2201 UTC
66
2201 UTC Storm Relative Motion
0.5
1.3
2.4
3.1
67
2201 UTC Visual Appearance (Looking East
Northeast)
2201 UTC
68
2201 UTC Visual Appearance (Looking East
Northeast)
2201 UTC
69
0.5 Degree Reflectivity
2206 UTC
Last Severe Hail Report at this Time
70
0.5 Degree Reflectivity
2211 UTC
71
0.5 Degree Reflectivity
2215 UTC
72
0.5 Degree Reflectivity
2220 UTC
73
2220 UTC Visual Appearance
2220 UTC
74
0.5 Degree Reflectivity
2224 UTC
75
2224 UTC Visual Appearance
2224 UTC
76
0.5 Degree Reflectivity
2229 UTC
77
0.5 Degree Reflectivity
2234 UTC
78
0.5 Degree Reflectivity
2238 UTC
79
0.5 Degree Reflectivity
2243 UTC
80
0.5 Degree Reflectivity
2247 UTC
81
0.5 Degree Reflectivity
2252 UTC
82
0.5 Degree Reflectivity
2256 UTC
83
0.5 Degree Reflectivity
2301 UTC
84
So Why No Tornado?
Gilmore 2002 from Grant 2008
85
Conceptual Model of Favorable Tornado Boundary
One that is rich in high Theta-E 10-30 mi. north
of boundary
Markowski 2002 from Grant 2008
86
LAPS Proximity Sounding (Adjusted to Reflect
Surface Conditions North of the Boundary)
87
18 KILN UTC Observed Sounding
88
LAPS Surface Theta E Observations
2143 UTC
15 knot storm motion
Lack of low level flow to be ingested by the
supercell
89
So Why No Tornado?
  • A few reasons are surmised
  • A relatively unmodified boundary that had
    recently emanated from convection still retained
    a shallow low theta e airmass
  • Dry air in mid levels results in colder more
    stable RFD
  • Low level storm relative flow was weak
  • The mid to low level circulation never recovered
    after convection fired on top of the meso at 2111
    UTC

90
References
  • Brooks, H.E., and J.P. Craven, 2002 A database
    of proximity soundings for significant severe
    thunderstorms, 19571993. Preprints, 21st Conf. on
    Severe Local Storms, San Antonio, TX, Amer.
    Meteor. Soc., 639-642.
  • Grant, B.N., 2008 Basics of tornadic storms.
    PowerPoint presentation, http//wdtb.noaa.gov/cou
    rses/dloc/workshop/presentations/tor- fcstg_basics
    .ppt.
  • Klemp, J.B., and R. Rotunno, 1983 A study of the
    tornadic region within a supercell
    thunderstorm. J. Atmos. Sci., 40, 359377.
  • Markowski, P. M., E. N. Rasmussen, J. M. Straka,
    1998 The occurrence of tornadoes in supercells
    interacting with boundaries during VORTEX- 95.
    Wea. Forecasting, 13, 852-859.
  • ____, J. M. Straka, E. N. Rasmussen, 2002 Direct
    surface thermodynamic observations within the
    rear-flank downdrafts of non-tornadic and
    tornadic supercells. Mon. Wea. Rev., 130,
    1692-1721.

91
References
  • Redmond, C. and Swiger, T., 2009 Storm chase
    6-19-09. Website, http//www.scalialab.com/news/c
    hase_6-19-09.html
  • Thompson, R. L., and R. Edwards, 2000c RUC-2
    supercell proximity soundings, Part II An
    examination of storm-relative winds normalized
    to supercell depth. Preprints, 20th Conf. Severe
    Local Storms, Orlando, Amer. Meteor. Soc.
  • Thompson, R. L., C. M. Mead, and R. Edwards,
    2007 Effective storm- relative helicity and bulk
    shear in supercell thunderstorm environments.
    Wea. Forecasting, 22, 102115.
  • Weisman, M. L. and J. B. Klemp, 1982 The
    dependence of numerically simulated convective
    storms on vertical wind shear and buoyancy. Mon.
    Wea. Rev., 110, 504520.

92
Special Thank You
  • Jeff Logsdon
  • Justin Arnott
  • Todd Holsten
  • Jon Chamberlain
  • Lonnie Fisher
  • Patrick Murphy
  • Sam Lashley

93
Other storm cant latch on
  • Polygons for first storm
  • Angle the storm can intercept bndry
  • Right mover (bunkers ID expected)

94
How Did We Handle the Event
95
Make note of lack of hail reports
96
Conceptual Model of Tornadogenesis
Wakimoto et al. (1997)
97
Area tornado history
  • Most sig tors qlcs or low topped mini

98
Detailed explanation why no tor
  • Conceptual models of boundaries vs this boundary
  • Warm vs cold rfd
  • Mid level flow
  • New updraft develops right on top of meso
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