Regional Variations in Vulnerability to Tornado Outbreaks in the Eastern United

States

Charles E. Konrad IIMaggie M. Kovach

Christopher M. FuhrmannJordan McLeod

Southeast Regional Climate CenterDepartment of Geography

University of North Carolina – Chapel Hill

Background

Number of Killer Tornado EventsAnnual Tornado Reports

Ashley 2007

Dixie A

lley

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.

Census data Tract level: 1990 & 2000

Data (continued)

• # of mobile homes

• Population• Pover

PovertySenior Citizens

A. Estimate the population and # of mobile homes in a 500 m buffer around each tornado track in the database.

Tornadoes observedEarly period: 1980-1995 1990 censusLate period: 1996-2010 2000 census

B. Record/calculate the following for each tornado:1. EF-level2. Track length3. Adjusted Fujita miles (Track length * EF-level)4. Number of deaths5. Number of deaths per km of track6. Exposed population, elderly, poverty7. Exposed population/km, elderly/km, poverty/km8. Exposed mobile homes9. Exposed mobile homes/km

Methodology

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

Methodology (con’d)

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)

ALL Deaths/km EF1-3 Deaths/km

FL 0.039 0.031TN 0.035 0.027NC 0.031 0.021OH 0.029 0.008AL 0.026 0.011GA 0.023 0.022PA 0.016 0.014TX 0.015 0.008

NE States 0.015 0.013AR 0.014 0.011IL 0.014 0.006

OK 0.014 0.005MO 0.012 0.010MS 0.011 0.009SC 0.011 0.004LA 0.010 0.007IN 0.009 0.006KN 0.008 0.003

WV/VA/DE/MD 0.008 0.005IA 0.003 0.003SD 0.003 0.001ND 0.002 0.001NE 0.002 0.001

Vulnerability when a tornado is on the ground

State ALL Deaths/km EF1-3 Deaths/km Mobile homes/km Pop/km Elderly/km Poverty/Km

FL 0.039 0.041 14.7 80.1 66.8 59.8TN 0.035 0.027 2.5 80.1 10.2 12.0NC 0.031 0.021 4.3 86.8 11.2 12.9OH 0.029 0.008 2.2 120.9 16.9 13.2AL 0.026 0.011 2.9 53.8 6.5 8.0GA 0.023 0.022 2.7 68.5 7.0 11.9PA 0.016 0.014 2.7 142.7 24.2 16.7TX 0.015 0.008 2 69.7 8.2 15.5

NE States 0.01 0.013 1.66 239.4 42.8 43.4AR 0.014 0.011 1.8 34.0 4.3 4.7IL 0.014 0.006 1.1 53.5 4.3 3.2

OK 0.014 0.005 1.3 41.4 4.3 5.1MO 0.012 0.01 1.4 44.2 5.8 44.2MS 0.011 0.009 1.5 36.6 4.3 7.1SC 0.011 0.004 4.1 69.9 7.9 10.2LA 0.01 0.007 2.3 72.8 9.9 19.2IN 0.009 0.006 1.6 96.4 13.7 13.5KN 0.008 0.003 0.7 23.9 2.9 3.3

WV/VA/DE/MD 0.01 0.005 2.2 216.4 25.2 27.8IA 0.003 0.003 0.4 29.6 4.3 6.1SD 0.003 0.001 0.2 10.6 1.1 0.8ND 0.002 0.001 0.2 9.8 1.5 1.4NE 0.002 0.001 0.3 21.0 2.1 1.3

Deaths per Km in the immediate vicinity of tornadoes

Percentage Change in Quantity 1980-1995 1996-2010

• Changes significant at the .10 and .05 level are in blue and bolded blue, respectively.

STUDY AREA ALL EF4-5 EF1-3 Daytime NightNUMBER OF DEATHS 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

Elderly exposed 3.8 -2.4 4.9 -3.6 19.3

Elderly exposed/km -14.5 24.4 -17.5 -19.1 -4.9

Poverty exposed -2.2 -12.5 -1.1 -21.8 24.1

Poverty exposed/km -16.6 15.8 -19.6 -15.6 -8.2

Regional Breakdown

SoutheastSouthern Plains

Northern PlainsMidwest

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 tornadoes24% in track length52% in mobile homes

6% deaths/ km16% mobile homes/km14% elderly/km17% poverty/km

Summary (continued)

Greatest secular increases observed in nocturnal tornadoes, especially South and Midwest

56% in deaths overall. 57% for EF1-EF3 tornadoes31% in track length72% in mobile homes

19% deaths/ km16% mobile homes/km5% elderly/km8% 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

Study area ALL EF4-5 EF1-3 Daytime NightNUMBER OF DEATHS 1591 671 920 967 624

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

Elderly exposed 3.8 -2.4 4.9 -3.6 19.3

Elderly exposed/km -14.5 24.4 -17.5 -19.1 -4.9

Poverty exposed -2.2 -12.5 -1.1 -21.8 24.1

Poverty exposed/km -16.6 15.8 -19.6 -15.6 -8.2

Percentage Change in Quantity 1980-1995 1996-2010

Pop exposed 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

Poverty exposed/km -11.6 -19.6 -11.9 -11.7 -10.7

100 kmbuffer

1 kmbuffer

Questions?

Chip Konradkonrad@unc.edu