Charles E. Konrad II
Maggie M. Kovach
Christopher M. Fuhrmann
Jordan McLeod
Southeast Regional Climate Center
Department of Geography
University of North Carolina – Chapel Hill
Background
Ashley 2007
Annual Tornado Reports
Number of Killer Tornado Events
Mobile Homes
Tornado fatalities by location (1985–2005)
• The likelihood of fatality is 20 times greater in mobile homes than in other
structures (Brooks and Doswell 2002)
Sutter and
Simons 2012
Research Question
• What are the regional variations in tornado outbreak
vulnerability?
• How vulnerable are people in the immediate vicinity of a
tornado? Once a tornado has touched down, how
vulnerable are individuals?
• How does population, mobile home density, poverty, and
numbers of senior citizens affect vulnerability in the path
of a tornado?
• What are the secular trends in tornado vulnerability?
Data
• Tornado data from 1980 to 2010 obtained from Storm
Prediction Center (SPC) using the online SeverePlot tool.
– Beginning & ending lat/lon, F/EF level of tornado, # deaths & injuries
of every reported tornado.
– Underreporting of tornadoes not an issue during the study period.
Data (continued)
Census data
Tract level: 1990 & 2000
• Population
•
Pover
Poverty
Senior Citizens
• # of mobile homes
Methodology
A. Estimate the population and # of mobile homes in a 500 m
buffer around each tornado track in the database.
Tornadoes observed
Early period: 1980-1995  1990 census
Late period: 1996-2010  2000 census
B. Record/calculate the following for each tornado:
1. EF-level
2. Track length
3. Adjusted Fujita miles (Track length * EF-level)
4. Number of deaths
5. Number of deaths per km of track
6. Exposed population, elderly, poverty
7. Exposed population/km, elderly/km, poverty/km
8. Exposed mobile homes
9. Exposed mobile homes/km
Methodology (con’d)
C. Compare differences between the early and late period.
- Stratify by EF level (EF1-3 vs. EF4-5) and night/day
occurrence
- Compare differences at the regional scale
Results
1. Deaths per km along track of tornadoes
2. Secular trends in:
a. Deaths
b. Population, # elderly, #poverty, number of
mobile homes in the immediate vicinity of
tornadoes
The Paths of Killer Tornadoes (1980-2010)
Vulnerability when a tornado is on the ground
ALL Deaths/km EF1-3 Deaths/km
FL
TN
NC
OH
AL
GA
PA
TX
NE States
AR
IL
OK
MO
MS
SC
LA
IN
KN
WV/VA/DE/MD
IA
SD
ND
NE
0.039
0.035
0.031
0.029
0.026
0.023
0.016
0.015
0.015
0.014
0.014
0.014
0.012
0.011
0.011
0.010
0.009
0.008
0.008
0.003
0.003
0.002
0.002
0.031
0.027
0.021
0.008
0.011
0.022
0.014
0.008
0.013
0.011
0.006
0.005
0.010
0.009
0.004
0.007
0.006
0.003
0.005
0.003
0.001
0.001
0.001
Deaths per Km in the immediate vicinity of tornadoes
State
ALL Deaths/km
EF1-3 Deaths/km
FL
TN
NC
OH
AL
GA
PA
TX
NE States
AR
IL
OK
MO
MS
SC
LA
IN
KN
WV/VA/DE/MD
IA
SD
ND
NE
0.039
0.035
0.031
0.029
0.026
0.023
0.016
0.015
0.01
0.014
0.014
0.014
0.012
0.011
0.011
0.01
0.009
0.008
0.01
0.003
0.003
0.002
0.002
0.041
0.027
0.021
0.008
0.011
0.022
0.014
0.008
0.013
0.011
0.006
0.005
0.01
0.009
0.004
0.007
0.006
0.003
0.005
0.003
0.001
0.001
0.001
Mobile
homes/km
14.7
2.5
4.3
2.2
2.9
2.7
2.7
2
1.66
1.8
1.1
1.3
1.4
1.5
4.1
2.3
1.6
0.7
2.2
0.4
0.2
0.2
0.3
Pop/km
Elderly/km
Poverty/Km
80.1
80.1
86.8
120.9
53.8
68.5
142.7
69.7
239.4
34.0
53.5
41.4
44.2
36.6
69.9
72.8
96.4
23.9
216.4
29.6
10.6
9.8
21.0
66.8
10.2
11.2
16.9
6.5
7.0
24.2
8.2
42.8
4.3
4.3
4.3
5.8
4.3
7.9
9.9
13.7
2.9
25.2
4.3
1.1
1.5
2.1
59.8
12.0
12.9
13.2
8.0
11.9
16.7
15.5
43.4
4.7
3.2
5.1
44.2
7.1
10.2
19.2
13.5
3.3
27.8
6.1
0.8
1.4
1.3
Percentage Change in Quantity 1980-1995  1996-2010
STUDY AREA
NUMBER OF DEATHS
ALL
EF4-5
EF1-3
Daytime Night
1591
671
920
967
624
EF-level
-3.3
0.3
2.9
-4.4
-1.3
Track length
23.6
-15.6
28.9
20
31
AEF_MILES
10.9
-15.2
19.7
6.6
20.1
Deaths
31.0
20.8
56.6
13.7
55.9
Death/km
6.0
43.1
20.8
-5.2
19.0
Pop exposed
5.2
30.1
4.7
0.3
15.8
Pop exposed/km
-12.4
10.8
-14.4
-14.7
-7.5
Exposed Mobile Homes
52.4
3.8
57.9
41.3
72.1
Exposed Mobile Homes/km
15.8
24.4
14.3
9.9
24.7
3.8
-2.4
4.9
-3.6
19.3
-14.5
24.4
-17.5
-19.1
-4.9
-2.2
-12.5
-1.1
-21.8
24.1
-16.6
15.8
-19.6
-15.6
-8.2
Elderly exposed
Elderly exposed/km
Poverty exposed
Poverty exposed/km
•
Changes significant at the .10 and .05 level are in blue and bolded blue, respectively.
Regional Breakdown
Northern Plains
Midwest
Southern Plains
Southeast
NE
Summary
Focus on vulnerability in the immediate vicinity of a tornado
• Greatest in South, especially FL (.039/km), lowest in Northern
Plains (.0025) Association with pop density, # mobile homes.
Secular changes: 1996-2010 vs. 1980-1995 for entire region
31%  in deaths overall. 57%  for EF1-EF3 tornadoes
24%  in track length
52%  in mobile homes
6%  deaths/ km
16%  mobile homes/km
14%  elderly/km
17%  poverty/km
Summary (continued)
Greatest secular increases observed in nocturnal tornadoes,
especially South and Midwest
56%  in deaths overall. 57%  for EF1-EF3 tornadoes
31%  in track length
72%  in mobile homes
19%  deaths/ km
16%  mobile homes/km
5%  elderly/km
8%  poverty/km
Current work
Apply a much larger buffer (100 km around each tornado
track) and compare with 1km buffer.
Rationale: Large buffer identifies the region within
which each tornado may have tracked given slightly
different initial conditions (e.g. location of supercell
development).
This addresses the vagaries of where tornadoes just
happen to develop.
Example of 100 km buffer for tornado that tracks from downtown
Tampa through downtown Orlando
Percentage Change in Quantity 1980-1995  1996-2010
Study area
NUMBER OF DEATHS
1 km
buffer
EF4-5
EF1-3
Daytime Night
1591
671
920
967
624
5.2
30.1
4.7
0.3
15.8
Pop exposed/km
-12.4
10.8
-14.4
-14.7
-7.5
Exposed Mobile Homes
52.4
3.8
57.9
41.3
72.1
Exposed Mobile Homes/km
15.8
24.4
14.3
9.9
24.7
3.8
-2.4
4.9
-3.6
19.3
-14.5
24.4
-17.5
-19.1
-4.9
-2.2
-12.5
-1.1
-21.8
24.1
-16.6
15.8
-19.6
-15.6
-8.2
6.8
-11.9
7.1
5.0
13.8
Pop exposed/km
-0.9
0.6
-1.8
1.2
2.5
Exposed Mobile Homes
26.3
6.4
26.7
22.5
34.9
Exposed Mobile Homes/km
18.7
11.9
18.5
16.5
22.3
Elderly exposed
11.5
26.9
11.3
12.8
10.9
Elderly exposed/km
5.2
39.7
2.6
4.7
10.4
Poverty exposed
-3.1
-28.4
-2.7
-4.8
2.5
-11.6
-19.6
-11.9
-11.7
-10.7
Pop exposed
Elderly exposed
Elderly exposed/km
Poverty exposed
Poverty exposed/km
100 km
buffer
ALL
Pop exposed
Poverty exposed/km
Questions?
Chip Konrad
konrad@unc.edu