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Response to Warnings during the 3 May 1999 Oklahoma City Tornado: Reasons and Relative Injury Rates

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Residents of homes that sustained F4 or F5 damage in the deadliest of the 3 May 1999 tornadoes were surveyed to determine their responses to the tornado warning reasons for their responses, and relative injury rates. There were 190 people in 65 surveyed houses at the time that warnings were issued. Television was the most commonly cited source of the warning (89%), followed by a telephone call (37%), sirens (37%), and AM/FM radio (25%), and 55% received the warning from more than one source. Nearly one-half (47%) of the residents fled their homes before the tornado struck. Of those who fled, 65% went to a tornado shelter, of whom 70% ran to the shelter (median distance 30 m) and 30% drove to the shelter (median distance 4.8 km). About one-half (53%) of those who fled their homes left in a vehicle. None of those who fled their homes, by foot or by vehicle, were injured. Of those who stayed in the home, 39% sought shelter in a bathroom, 38% in a closet, 9% in a hallway and 15% in other rooms. Reasons for not leaving included believing the storm would not strike their house. believing it was too late or too dangerous to leave, having no transportation available, or having no alternative shelter available. Thirty percent of those who remained in their homes were injured and 1% killed. The rate of serious injury was not significantly different for those in a closet (14%), hallway (20%), or bathroom (23%). Tornado preparedness and warning programs should recognize that long tornado warning lead times and street-level television coverage allow residents to make reasoned decisions to minimize risk and that those decisions may include driving out of the path of the tornado.
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2002 577HAMMER AND SCHMIDLIN
q 2002 American Meteorological Society
Response to Warnings during the 3 May 1999 Oklahoma City Tornado: Reasons and
Relative Injury Rates
B
ARBARA
H
AMMER AND
T
HOMAS
W. S
CHMIDLIN
Department of Geography, Kent State University, Kent, Ohio
(Manuscript received 15 February 2001, in final form 14 May 2001)
ABSTRACT
Residents of homes that sustained F4 or F5 damage in the deadliest of the 3 May 1999 tornadoes were surveyed
to determine their responses to the tornado warning, reasons for their responses, and relative injury rates. There
were 190 people in 65 surveyed houses at the time that warnings were issued. Television was the most commonly
cited source of the warning (89%), followed by a telephone call (37%), sirens (37%), and AM/FM radio (25%),
and 55% received the warning from more than one source. Nearly one-half (47%) of the residents fled their
homes before the tornado struck. Of those who fled, 65% went to a tornado shelter, of whom 70% ran to the
shelter (median distance 30 m) and 30% drove to the shelter (median distance 4.8 km). About one-half (53%)
of those who fled their homes left in a vehicle. None of those who fled their homes, by foot or by vehicle, were
injured. Of those who stayed in the home, 39% sought shelter in a bathroom, 38% in a closet, 9% in a hallway,
and 15% in other rooms. Reasons for not leaving included believing the storm would not strike their house,
believing it was too late or too dangerous to leave, having no transportation available, or having no alternative
shelter available. Thirty percent of those who remained in their homes were injured and 1% killed. The rate of
serious injury was not significantly different for those in a closet (14%), hallway (20%), or bathroom (23%).
Tornado preparedness and warning programs should recognize that long tornado warning lead times and street-
level television coverage allow residents to make reasoned decisions to minimize risk and that those decisions
may include driving out of the path of the tornado.
1. Introduction
The 3 May 1999 Oklahoma City, Oklahoma, tornado
provided the opportunity to investigate public response
to tornado warnings and the relative injury rates asso-
ciated with the responses. The tornado outbreak across
Oklahoma and Kansas produced over 70 tornadoes and
killed 48 people (NWS 1999). Over 4400 houses were
destroyed. The deadliest tornado in the outbreak killed
38 people and was on the ground for 87 min, along a
path from near Chickasha, Oklahoma, to suburban
Oklahoma City (NWS 1999). This tornado was unusual
for its long path, strength, and the long warning lead
times. It occurred in a region with high tornado aware-
ness among the public, the media, and the National
Weather Service (NWS). The tornado occurred as a
highly visible funnel during daylight and was broadcast
live by Oklahoma City television stations (NWS 1999).
The unique nature of the tornado inspired a symposium
on the first anniversary of the event and this special
issue devoted to the outbreak.
The public response to tornado warnings has received
Corresponding author address: Thomas W. Schmidlin, Dept. of
Geography, Kent State University, P.O. Box 5190, Kent, OH 44242-
0001.
E-mail: tschmidl@kent.edu
little attention from researchers (Golden and Adams
2000). Sorensen and Mileti (1988) reviewed 24 studies
of public behavior in response to disaster warnings but
did not report any study of tornado warnings. However,
Sorensen and Mileti (1988) and Sorensen (2000) re-
ported that there are many unknowns regarding public
response to disaster warnings, including the time be-
tween hearing a warning siren and receiving a warning
message, how different hazard characteristics affect be-
havior, the distance traveled to a shelter destination, and
the choice of protective action. Golden and Adams
(2000) noted that we have little understanding of the
relationships among behavioral responses to tornado
warnings, location, warning lead time, warning receipt,
and rates of injury and death. Knowing how and why
individuals respond to tornado warnings and the relative
success of those responses in reducing risk has obvious
utility in planning the effective delivery of tornado safe-
ty and preparedness advice and tornado warnings.
The NWS service assessment of the 3 May 1999 tor-
nado outbreak (NWS 1999) acknowledged that casu-
alties during this event were low because the public
responded to early NWS warnings. Although it is not
usually recommended that a resident leave a sturdy
frame home during a tornado, the assessment also re-
ported that one television station urged people to get
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out of the path of the storm and that many people did
flee in automobiles because of ‘ample National Weather
Service warning lead times and live local TV cover-
age. . . .’ There has been much debate surrounding the
risk encountered by an occupant of a vehicle during
tornadoes (Schmidlin and King 1996; Schmidlin 1997;
Lopes 1997). Since the study by Glass et al. (1980) of
the 1979 Wichita Falls, Texas, tornado, which claimed
the lives of 26 vehicle occupants, it has been widely
assumed that occupying a vehicle during a tornadic
storm is implicitly unsafe. Although vehicles are known
to be susceptible to damage during tornadoes (CDC
1979, 1994; Glass et al. 1980; Grazulis 1993), and al-
though deaths do occasionally occur in vehicles, they
typically occur when the vehicle is crushed by falling
objects or when the vehicle is tossed or rolled, often
resulting in the ejection of unrestrained occupants (Cart-
er et al. 1989; Grazulis 1993; Hammer and Schmidlin
2001; Schmidlin and King 1995). In the past, relatively
few vehicle occupants have been killed during tornadoes
(Hammer and Schmidlin 2001).
This study investigated actions taken by those resi-
dents whose homes sustained F4 or F5 damage during
the 3 May 1999 Oklahoma City tornadoes. These res-
idents were assumed to be at greatest risk of injury or
death among those who remained in homes during the
tornado. The purpose of this research was to determine
the percentage of residents who fled their single-family
homes after receiving the tornado warnings, to assess
their reasons for leaving, and to determine their desti-
nations, modes of travel, and distances traveled from
their homes. In addition, we evaluated how residents
received the warning, the length of their response times,
and the relative injury rate for those who fled their
homes. This study also determined the percentage of
residents who remained within F4- or F5-damaged
homes after receiving a warning, how they received that
warning, and the amount of warning lead time. We also
assessed in what sites residents sought shelter within
their homes and the relative injury rates associated with
those sites.
2. Methods
The study area included the last 20 km of the 61-km
tornado damage path that extended from near Chickasha
across suburban Oklahoma City to Midwest City,
Oklahoma. Maps of the damage path (provided by T.
Marshall of Haag Engineering Co.) indicated there were
312 single-family homes that sustained F4 or F5 damage
in this area. These maps included damaged areas of
Moore, Oklahoma City, Del City, and Midwest City in
Oklahoma. Databases containing the names and ad-
dresses of residents, as well as neighborhood plat maps
that coincided with the damage-path maps were ob-
tained from the city manager of Moore and the
Oklahoma City Department of Public Works. There was
also F4 and F5 damage earlier in this path and along
the paths of other tornadoes that day.
Using the databases and maps, names and addresses
of residents were matched for 173 of the F4- or F5-
damaged homes. The other 139 homes could not be
matched to a name and address because the resident had
moved and had not registered a new address with the
city disaster recovery program. We are not aware of any
substantial difference between the homes for which we
could match names and addresses and those for which
we could not and do not expect that this introduced bias
into the results. A short survey (available upon request
from the authors) was sent to those 173 addresses in
February of 2000. Questions were asked pertaining to
how the resident received the warning, whether the res-
ident had multiple warning sources, the amount of warn-
ing lead time, whether residentsremained in theirhomes
or fled, where they sought shelter (in house or other-
wise), the extent of any injuries sustained, the mode of
transport and distance to shelter if they fled, and their
reasons for leaving or staying. Post-paid return enve-
lopes were provided with the surveys.
Of the 173 surveys sent, 29 were returned by
Oklahoma post offices as undeliverable. This failure to
deliver to these addresses may have been due to the
subsequent moves of residents or errors in the database
of temporary addresses provided by the cities. Of the
remaining 144 surveys that we assume were delivered,
71 (49%) were completed and returned. Six of those
were not used because the resident was not at home
when the tornado warning was issued. The remaining
65 household surveys were analyzed. The response to
mailed surveys may bias the results if those who return
the surveys differ substantially from the population
sought. Our response rate of 49% is relatively good for
a mailed survey and we know of no reason to expect a
bias in the results.
Although ‘‘behavioral-intent’’ surveys can be used to
assess what people would do if a tornado warning were
issued, those results have been shown to be inaccurate
at predicting actual warning responses (Sorensen 2000).
Therefore, this research reports on the study of actual
behavioral response to a tornado warning to provide
better planning information to meteorologists and emer-
gency managers.
3. Results
When the warning was issued, there were 190 people
in the 65 surveyed homes that sustained F4 or F5 dam-
age. Among the 65 households surveyed, television was
the most commonly cited source of the tornado warning
(89%), followed by a telephone call (37%), sirens
(37%), AM/FM radio (25%), and National Oceanic and
Atmospheric Administration weather radio (3%). Most
of the households (55%) received the warning via more
than one source. Time between receiving the warning
and when the tornado struck was greater than 30 min
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2002 579HAMMER AND SCHMIDLIN
T
ABLE
1. Destination and method of fleeing of respondents who
left homes.
Method of fleeing
the home
By vehicle By foot
Persons with a known destination of
the 90 who fled their home
46 (53%) 41 (47%)
Destinations
Storm shelter/celler
Indefinite location outside of the path
House of a friend or relative
Highway overpass
17 (20%)
16 (18%)
9 (10%)
4 (5%)
39 (45%)
0
2 (2%)
0
for 57% of the households, 15–30 min for 20%, 5–15
min for 17%, and less than 5 min for 5%.
Upon hearing the warning, 90 (47%) people fled their
homes. The destination was known for 88 people and
both the mode of transport (leaving on foot or in a
vehicle) and destination were known for 87 people. Of
the 90 people who fled, only 1% left within 5 min of
receiving the warning, 18% left 5–15 min after receiving
the warning, 32% left after 15–30 min, and 48% left
more than 30 min after receiving the warning. Of those
who left their homes, 45% ran to a storm shelter within
200 m of their home (median distance 30 m; Table 1).
About one-half of those went to their own shelter, and
one-half went to a neighbor’s shelter. Of the individuals
who ran to a shelter within 200 m of their home, 41%
left within 15 min of receiving the warning, 28% left
between 15 and 30 min, and 31% waited more than 30
min before leaving. Another 20% drove to a storm shel-
ter (median distance 4.8 km), 10% drove to a friend’s
or relative’s house (median 12 km), 2% ran to a friend’s
or relative’s house (median 50 m), 18% drove to an
indefinite location out of the storm’s path (median 1.6
km), and 5% drove to an overpass. The indefinite lo-
cations included, for example, those who drove to near-
by towns, to a nearby park, or to nearby open highways
that were out of the path and provided a view of the
storm. In summary, 65% of the residents who fled their
homes went to a storm shelter. Of those, 70% ran to a
shelter (median 30 m) and 30% drove to a shelter (me-
dian 4.8 km).
One-half (53%) of the people who fled their homes
left in a vehicle. Of the 46 people who fled their homes
in a vehicle, 20% left within 15 min of receiving the
warning, 17% left between 15 and 30 min, and 63%
waited more than 30 min before leaving. Residents who
fled in vehicles primarily left in sedans (44%) and vans
or minivans (31%). Other vehicles used to flee the
homes were pickup trucks (16%) and sport utility ve-
hicles (9%). Most of the respondents (93%) reported
using a seat belt as they fled the tornado.
Respondents cited various reasons for leaving, but
two reasons predominated. Of the residents who left,
35% said that TV reports told them to get out of the
path of the storm and 31% said they left for sturdier
shelter. In addition, 11% left to be with family and 22%
gave other reasons (such as they saw the storm ap-
proaching, they had previous experience with tornadoes,
they received a telephone call from a concerned relative,
etc.). None of the 90 people who fled their homes were
injured.
Of the 190 people in the 65 surveyed homes, 100
were still in their homes when the tornado struck. Of
those 100, 39% sought shelter in a bathroom, 37% in
a closet, 10% in a hallway, and 14% in some other room
such as the living room, family room, laundry room, or
utility room. None of the homes had a basement, but
3% were split-level homes with a room partially un-
derground. Among residents who remained in their
homes during the tornado, two reasons were predomi-
nately cited for remaining in the home: 44% stated that
they either did not believe the storm would hit them or
they realized too late that the storm might hit their
homes; another 31% stated that they thought it was too
dangerous to leave. In addition, 16% of respondents
cited the reason for remaining in their homes as either
a lack of transportation or a lack of an alternate shelter
location, and 8% stated that they thought the storm re-
ports were exaggerated, that they thought the storm was
not severe, or that they were not paying much attention
to the storm reports. One respondent (1%) stated that
he felt safe in his home shelter area, which was in a
bathtub in a partially underground bathroom.
Of the 100 residents who remained in homes that were
subsequently struck and damaged (F4 or F5) by the
tornado, 70% were uninjured; 14% were injured, treat-
ed, and released from a medical facility; 15% were ad-
mitted to a hospital; and one resident (1%) was killed.
In an attempt to determine the safest location within the
homes, a 95% confidence interval was calculated for
the proportion of residents seriously injured (admitted
to hospital or killed) by room type (closet, hallway,
bathroom) using the method of Conover (1980, 99
100). There were no serous injuries to persons in other
rooms such as living rooms, family rooms, or utility
rooms. The assumption that the risk of injury was mu-
tually independent among residents may not hold be-
cause there was commonly more than one person taking
shelter in the room. However, different injury severity
among people in the same room was not uncommon. In
fact, residents had different levels of injury (none, mi-
nor, serious, or killed) in 22% of the 36 households in
which all residents were in the same room when the
tornado struck. There was no significant difference in
the proportion of people with serious injuries among
those who sought shelter in a closet [0.14, 95% confi-
dence interval (c.i.) 5 0.05–0.29], hallway (0.20, 95%
c.i. 5 0.03–0.56), or a bathroom (0.23, 95% c.i. 5 0.12–
0.38). The person in this sample who was killed was in
a bathroom with four others when the tornado struck.
Among the other people in that bathroom, two were
seriously injured and two had minor injuries.
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17WEATHER AND FORECASTING
4. Conclusions
We surveyed residents of suburban Oklahoma City
who were at home when tornado warnings were issued
on 3 May 1999 and whose homes were subsequently
leveled (F4 or F5 damage) by the tornado. People in
our sample who left their home after receiving the warn-
ing had long warning lead times and used television as
their primary source of information. Several cited
KWTV-9 meteorologist Gary England’s advice to get
underground or get out of the path of the storm as in-
fluential in their decision to flee. Live television cov-
erage on several channels provided a view of the tornado
and street-level path information. Residents considered
information from television, the appearance outdoors,
and, in some cases, telephone calls from a friend or
relative farther up the path for several minutes before
making the decision to leave the home or to seek shelter
inside the home. Leaving the home appears to have been
a contemplated action rather than a decision induced by
panic.
Almost one-half (47%) of the surveyed residents left
their home, and 53% of those who left the home fled
in a vehicle. Most (65%) who fled their home went to
a storm shelter; others simply drove away out of the
path and waited for the tornado to pass. None of those
in the sample who fled their home were injured, whereas
30% of those who remained inside the home were in-
jured. Despite the early evening occurrence of this vi-
olent tornado in a major metropolitan area and the fact
that many families fled the path in vehicles (NWS 1999),
there were no fatalities among people inside vehicles.
Surveyed residents in the path reported long warning
lead times and intense use of the television for warning
information; they consulted multiple sources of infor-
mation, especially confirmation of the risk by telephone;
and made reasoned and deliberate decisions about seek-
ing shelter, often waiting until the risk appeared very
high. Of those who remained in the home, most people
in our sample sought shelter in recommended locations
of bathrooms, hallways, and closets, and the overall
injury rate in these homes without basements (0.30,95%
c.i. 5 0.22–0.40) was surprisingly low for F4 and F5
damage.
These conclusions generally support the observations
of Sorensen and Mileti (1988) and Sorensen (2000) who
reported that disaster warnings are often received
through a mix of sources, especially informal sources
such as friends and neighbors; that people seek addi-
tional information following receipt of the warning and
adjust the rapidity of their evacuation behavior to the
severity and timing of the threat; that the public response
is spread out over time; and that the public may be fairly
good appraisers of the microconditions of risk in their
environment.
This was a long-lived, violent tornado that was highly
visible and was broadcast live by television stations.
The results presented here may not be typical of other
situations, such as tornadoes occurring during darkness
or wrapped in rain. However, if real-time, street-level
mapping of tornado paths becomes more common on
television, meteorologists and emergency managers
should expect the public to use that information to assess
their risks. The common notion, born in the aftermath
of the 1979 Wichita Falls tornado, that being in a vehicle
during a tornado warning is synonymous with injury
and death can no longer be assumed or promoted. Al-
though high numbers of deaths have occurred in vehi-
cles during tornadoes, the occurrences are rare (Hammer
and Schmidlin 2001). The use of vehicles to flee the
path of the Oklahoma City tornado has shown that peo-
ple can successfully make reasoned decisions that re-
duce the risk of injury and death. Many people recog-
nized that it was safer to be in any location outside of
the tornado path, including a vehicle, than to be in a
house within the path.
Acknowledgments. Sixty-five residents whose homes
were leveled by the Oklahoma City tornado took time
to complete our survey, telling us what they did before
and during the tornado, with many providing useful
comments in addition to answering thesurveyquestions.
We are thankful that they were willing to relive this
tragedy to help us study the human response to a deadly
hazard. We appreciate the assistance and data provided
by Tim Marshall, Haag Engineering; Stephen Eddy, city
of Moore; Jim Lewellyn, Jan Hinton, J. C. Reiss, and
Mark Tullius, Oklahoma City Department of Public
Works; Scott Tezak, Greenhorne and O’Mara; and Mat-
thew Biddle, University of Oklahoma. Partial funding
for this project was provided by the Office of Research
and Graduate Studies and the Department of Geography
at Kent State University.
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... Each year, over 1000 tornadoes affect the United States on average, leaving many thousands of people to recover and reassess their risk of subsequent events (NOAA 2019a). For a small portion of these tornadoes, research has been conducted to understand aspects of the disaster, including the demographic and situational factors that drive casualties in tornadoes King 1995, 1997;Schmidlin et al. 1998;Daley et al. 2005;Biddle 2010;CDC 2012), how false alarms may influence warning response and casualties (Simmons and Sutter 2008;Ripberger et al. 2015;Trainor et al. 2015), the ways tornado casualties may change with risk exposure (Ashley and Strader 2016), the preferences people have for lead time in tornadoes (Hoekstra et al. 2011), and the ways that National Weather Service (NWS) warnings were received, understood, and acted upon during particular events (Hammer and Schmidlin 2002;Schmidlin et al. 2009;Schultz et al. 2010;NWS 2008NWS , 2011aSenkbeil et al. 2012;NWS 2014). This variety of works has revealed that there are numerous factors that ultimately shape behaviors and outcomes, including objective risk factors like exposure and vulnerability and subjective factors like individual perceptions of risk. ...
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Chapter
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Research Proposal
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Occupants of vehicles encounter an uncertain degree of risk during tornadic storms. The current National Weather Service guidelines suggest we abandon vehicles to lie in a ditch if no sturdy shelter is available. However, these guidelines were developed without the benefit of supporting research. As we are an increasingly vehicle-dependent society, it is important to explore the historical record of vehicle-occupant deaths to see if the National Weather Service guidance is appropriate. The objective of this paper is to investigate the number, distribution, and broad spatial and temporal trends associated with vehicle-occupant deaths that have occurred as a result of tornadoes, and to define the proportion of tornado-induced deaths that have occurred in vehicles.There were 15,047 deaths caused by tornadoes from 1900 through 1998. Of those, 5685 occurred at a defined site, and 270 were known to have occurred in vehicles. The number of vehicle-occupant deaths, as a proportion of all site-known, tornado-induced deaths, was constant from 1959–1979, but decreased significantly between 1980–1998. The number of deaths was related to several influencing factors. Linear regressions and correlations were employed to determine the degree of relationship between the number of deaths and several explanatory factors. While population, number of vehicle registrations, and number of tornadoes all seemed to influence the number of deaths to some degree, the most significant factor to influence the number of deaths appeared to be vehicle safety features. Most vehicle-occupant deaths occurred during rare F4 tornadoes, when vehicles where thrown from roadways. Regionally, the Great Plains had the highest number of vehicle-occupant deaths from tornadoes.
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