Article

Unusually Devastating Tornadoes in the United States: 1995–2016

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Abstract

Previous research has identified a number of physical, socioeconomic, and demographic factors related to tornado casualty rates. There remain gaps in our understanding of community-level vulnerabilities to tornadoes. Here a framework is provided for systematically identifying the most unusually devastating tornadoes, defined as those where the observed number of casualties far exceeds the predicted number. Results show that unusually devastating tornadoes occur anywhere tornadoes occur in the United States, but rural areas across the Southeast appear to be most frequented. Seven examples of unusually devastating tornadoes affecting six communities are examined in more detail. In addition, results highlight that cities and towns affected by unusually devastating tornadoes have their own socioeconomic and demographic profiles. Identifying geographic clusters of unusually devastating tornadoes builds a foundation to address community-level causes of destruction that supports ethnographic and qualitative—in addition to quantitative—studies of place-based vulnerability. Key Words: statistics, tornado, vulnerability.

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... Mapping the location of tornado casualties (Ashley 2007;Fricker et al. 2017b) has provided insight into the spatial patterns of high casualty counts, which, historically, have occurred at the highest rates in the Mid-South and Southeast United States, while creation of vulnerability indexes like the Social Vulnerability Index (SoVI; ) and the Socioeconomic and Demographic Vulnerability Index (SEDVI; (Strader and Ashley 2018)) have provided broad-level understanding of factors that influence casualty rates. Both of these methods, however, can break down at finer scales (i.e., city-or town-level), leading Fricker and Elsner (2019) to suggest place-based or bespoken approaches to the tornado casualty problem. They argue that if the goal is to intervene-reduce the number of tornado casualties-in the tornado casualty problem, more care has to be taken to investigate individual community factors (e.g., labor displacements, history of mobile homes, redlining, etc.) that might explain why tornadoes are producing more casualties than we would otherwise expect (Fricker and Elsner 2019). ...
... Both of these methods, however, can break down at finer scales (i.e., city-or town-level), leading Fricker and Elsner (2019) to suggest place-based or bespoken approaches to the tornado casualty problem. They argue that if the goal is to intervene-reduce the number of tornado casualties-in the tornado casualty problem, more care has to be taken to investigate individual community factors (e.g., labor displacements, history of mobile homes, redlining, etc.) that might explain why tornadoes are producing more casualties than we would otherwise expect (Fricker and Elsner 2019). ...
... Mobile homes are an established vulnerability metric in tornado casualty events Ashley 2007;Strader and Ashley 2018;Fricker and Elsner 2019;Ash et al. 2020). Owing to the quality of building materials and low wind load requirements, mobile homes are the site of many tornado casualties throughout the Mid-South and Southeast U.S. With this in mind, we investigate whether the presence of mobile homes in and around Shreveport is a main driver of tornado casualty events using data from the 1990, 2000, and 2010 decennial Census at the tract-level (Fig. 4). ...
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... Tornadoes with higher damage ratings (e.g., strong and violent (E)F2-(E)F5) yield more casualties than do tornadoes with lower ratings (e.g., weak (E)F0-(E)F1) (Merrell et al. 2005;Ashley 2007;Simmons and Sutter 2011). Tornadoes that dissipate more energy (i.e., those with greater power) also tend to yield greater casualty counts (Fricker et al. 2017;Elsner et al. 2018;Fricker and Elsner 2019). ...
... Daily and per event casualty counts are sensitive to the geophysical attributes of tornadoes (e.g., tornado numbers, path length, path width, intensity, time of day), the socioeconomics and demographics of the affected population (e.g., income, age, disability, non-English speaking, pre-existing health conditions), and the built environment (e.g., age of structures, density of structures, number of manufactures and mobile homes) Merrell et al. 2005;Ashley et al. 2008;Sutter and Simmons 2010;Simmons and Sutter 2011;Dixon and Moore 2012;Ashley and Strader 2016;Strader et al. 2016Strader et al. , 2017Fricker et al. 2017;Elsner et al. 2018;Fricker and Elsner 2019). Changes to any of these vulnerability factors will affect casualty counts. ...
... The spatial dispersion of tornadoes has decreased over time, most notably in spring, summer, and fall (Moore and McGuire 2019). The shift toward the southeastern USA and decreased spatial dispersion, in turn, have implications for casualties because tornadoes in this region tend to produce more casualties than those in other regions, owing largely to high social vulnerability, abundance of manufactured and mobile homes, and reduced visibility Cutter et al. 2003;Ashley 2007;Schmidlin et al. 2009;Sutter and Simmons 2010;Elsner et al. 2018;Strader et al. 2019;Fricker and Elsner 2019). ...
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... Other studies highlight the potential causality and economic impacts of tornadoes [46,47]. For example, Fricker and Elsner (2020) draw attention to how community socioeconomic and demographic characteristics increase vulnerability to unusually devasting tornadoes [48]. Mere geographic location is not the only contributing factor to vulnerability. ...
... The physiographic features certainly play a role in the development of severe weather, but the precise impact of these environments is beyond the scope of this study and is an area of continued research [60,61]. Future research may consider the intersection of tornado tracks with social factors such as building material or socio-economic status [48,62,63]. While the relative number and severity of tornadoes may not rival that of the U.S. Midwest and Great Plains, the observational data explored are suggestive of a statistically significant concentration (clusters) of tornado activity as well as indications of temporal increases. ...
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Using a new data set on annual deaths from disasters in 73 nations from 1980 to 2002, this paper tests several hypotheses concerning natural-disaster mitigation. Though richer nations do not experience fewer natural disasters than poorer nations, richer nations do suffer less death from disaster. Economic development provides implicit insurance against nature's shocks. Democracies and nations with higher-quality institutions suffer less death from natural disaster. Because climate change is expected to increase the frequency of natural disasters such as floods, these results have implications for the incidence of global warming.
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In this paper, we collect, categorize, and discuss the existence of numerous ways of knowing about tornado threat that largely differ from the perspective taken by the meteorological community. These alternate ways of knowing became apparent during interviews with survivors of the 27 April 2011 tornado outbreak in the US southeast, particularly in Alabama and Mississippi. Phenomena discussed herein include perceptions of safety near waterways, vulnerability near a specific highway with a recently modified landscape, the protective nature of hills, relative optimism about home sites, and local observational weather knowledge. Theoretical explanations offered for these observed phenomena include ideas from risk perception and place attachment literatures.
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Data from some recent tornado damage assessments are used to compute the percentage of damage path by enhanced Fujita (EF) rating and to estimate kinetic energy. Only a small fraction of the total area gets the highest damage rating and this fraction is lower than a model used by the U.S. Nuclear Regulatory Commission. However, estimates of kinetic energy derived from a characteristic wind speed for each EF rating and the fraction of area with that rating match kinetic energy estimates using the model percentages. On average the higher the EF rating the larger the kinetic energy, but there is large variability in the relationship. The average total kinetic energy over the EF1 tornadoes examined in the study is .61 TJ, which compares with an average of 2.37 TJ, 40.1 TJ, 36.5 TJ, and 50.4 TJ for the EF2, EF3, EF4, and EF5 tornadoes, respectively. The most energetic tornado had a maximum damage rating of EF3.
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The impact of the installation of Weather Surveillance Radar-1988 Doppler (WSR-88D) radars in the 1990s on the quality of tornado warnings and occurrence of tornado casualties is examined. This analysis employs a dataset of tornadoes in the contiguous United States between 1986 and 1999. The date of WSR-88D radar installation in each National Weather Service Weather Forecast Office is used to divide the sample. Tornado warnings improved after the installation of Doppler radar; the percentage of tornadoes warned for increased from 35% before WSR-88D installation to 60% after installation while the mean lead time on warnings increased from 5.3 to 9.5 min and the false alarm ratio fell slightly. A regression analysis of tornado casualties, which controls for the characteristics of a tornado and its path, reveals that expected fatalities and expected injuries were 45% and 40% lower for tornadoes occurring after WSR-88D radar was installed in the NWS Weather Forecast Office. This analysis also finds that expected casualties are significantly lower for tornadoes occurring during the day or evening than late at night throughout the sample, which provides indirect evidence of the life-saving effects of tornado warnings.
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Losses from environmental hazards have escalated in the past decade, prompting a reorientation of emergency management systems away from simple postevent response. There is a noticeable change in policy, with more emphasis on loss reduction through mitigation, preparedness, and recovery programs. Effective mitigation of losses from hazards requires hazard identification, an assessment of all the hazards likely to affect a given place, and risk-reduction measures that are compatible across a multitude of hazards. The degree to which populations are vulnerable to hazards, however, is not solely dependent upon proximity to the source of the threat or the physical nature of the hazard –social factors also play a significant role in determining vulnerability. This paper presents a method for assessing vulnerability in spatial terms using both biophysical and social indicators. A geographic information system was utilized to establish areas of vulnerability based upon twelve environmental threats and eight social characteristics for our study area, Georgetown County, South Carolina. Our results suggest that the most biophysically vulnerable places do not always spatially intersect with the most vulnerable populations. This is an important finding because it reflects the likely ‘social costs’ of hazards on the region. While economic losses might be large in areas of high biophysical risk, the resident population also may have greater safety nets (insurance, additional financial resources) to absorb and recover from the loss quickly. Conversely, it would take only a moderate hazard event to disrupt the well-being of the majority of county residents (who are more socially vulnerable, but perhaps do not reside in the highest areas of biophysical risks) and retard their longer-term recovery from disasters. This paper advances our theoretical and conceptual understanding of the spatial dimensions of vulnerability. It further highlights the merger of conceptualizations of human environment relationships with geographical techniques in understanding contemporary public policy issues.
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The enhanced Fujita scale category 4 (EF4) Tuscaloosa, Alabama, tornado on 27 April 2011 produced 64 fatalities along its 130-km track. Hybrid survey/interviews were conducted with a sample of 211 Tuscaloosaarea residents to determine how the 27 April tornado might change future shelter-seeking plans. Despite a history of tornadoes in the area, only 47% of Tuscaloosa residents had shelter plans in place prior to 27 April, but 62% intend to change their shelter plans or have shelters plans for the future. Changes in shelterseeking plans were divided into four groups and discussed according to commonalities. Logistic regression with demographic variables was then used to predict those likely to have shelter plans before 27 April and those likely to change their shelter plans in the future. Among these variables, residents over age 55 [odds ratio (OR) 8.9,95%; confidence interval (CI): 2.167-36.352] and those having a bachelor's degree (OR 5.1, CI: 1.342-19.316) were more likely to have had shelter plans before 27 April. The most significant variable indicating a change in future shelter-seeking plans is being Hispanic/Latino (OR 5.2, CI: 1.753-15.465). These results may assist National Weather Service (NWS) personnel, broadcast meteorologists, emergency managers, and city planners with the development of targeted warning communication tactics and safety strategies for a future tornado event.
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Casualties from natural disasters may depend on the day of the week they strike. With data from the Spatial Hazard Events and Losses Database for the United States (SHELDUS), daily variation in hurricane and tornado casualties from 5,043 tornado and 2,455 hurricane time/place events is analyzed. Hurricane forecasts provide at-risk populations with considerable lead time. Such lead time allows strategic behavior in choosing protective measures under hurricane threat; opportunity costs in terms of lost income are higher during weekdays than during weekends. On the other hand, the lead time provided by tornadoes is near zero; hence tornados generate no opportunity costs. Tornado casualties are related to risk information flows, which are higher during workdays than during leisure periods, and are related to sheltering-in-place opportunities, which are better in permanent buildings like businesses and schools. Consistent with theoretical expectations, random effects negative binomial regression results indicate that tornado events occurring on the workdays of Monday through Thursday are significantly less lethal than tornados that occur on weekends. In direct contrast, and also consistent with theory, the expected count of hurricane casualties increases significantly with weekday occurrences. The policy implications of observed daily variation in tornado and hurricane events are considered.
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An online survey was completed by 2,921 students and employees at a large university following a tornado near-miss that required taking shelter. During this event, the university’s emergency alert messaging system was tested. The first alert message was received by over 66% of the sample within 15min, and cell phones were the most common means of receiving this message—especially for students. Employees relied more on computer instant messaging than did students. Interpersonal communication was also important. The majority could correctly define tornado watch, tornado warning and shelter in place. Age and frequency of use of weather information were of mixed significance as predictors. Finally, over three quarters of respondents reported taking shelter during the event. Being female and being an employee made a respondent more likely to take shelter.
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To say that the level of fatalities resulting from an earthquake is inversely related to a country's per capita level of income is hardly novel. What makes our approach novel is that we relate fatalities to both per capita income and the level of inequality that exists within a country through their joint impact on the likelihood of collective action being taken to mitigate the destructive potential of quakes. We first develop a theoretical model which offers an explanation as to why, in some environments, different segments of society prove incapable of arriving at what all parties perceive to be an agreeable distribution of the burden of the necessary collective action, causing the relatively wealthy simply to self-insure against the disaster while leaving the relatively poor to its mercy. Following this, we test our theoretical model by evaluating 269 large earthquakes occurring worldwide, between 1960 and 2002, taking into account other factors that influence a quake's destructiveness such as its magnitude, depth and proximity to population centers. Using a Negative Binomial estimation strategy with both random and fixed estimators, we find strong evidence of the theoretical model's predictions. That is, while earthquakes themselves are natural phenomena beyond the reach of humankind, our collective inaction with respect to items like the creation and enforcement of building codes, failure to retrofit structures and to enact quake-sensitive zoning clearly plays a part in determining the actual toll that a given quake takes. And, it is through these and other examples of collective inaction that limited per capita income and inequality couple together with a given quake's natural destructive power in determining the actual fatalities resulting from a quake.
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Pre- and post-event data on the long-term effects of the 1966 Topeka tornado revealed a complex pattern of responses by the elderly. In comparison to younger victims, older victims: regarded the loss of exterior items and house-related damage as being more important; received aid from community resources far less frequently; were less likely to use insurance and other economic sources in recovery; less frequently increased insurance coverage, savings, bank credit, or the use of credit cards; and did not perceive any significant long-term negative consequences regarding their physical or mental health.
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This article analyzes the effects of chronological age of disaster victims on their responses to stress effects of natural disasters. Previous research is reviewed and major findings of that research are noted. Findings regarding disaster losses, physical impacts, aid utilization patterns, kinship relations, relative deprivation, social-psychological impacts, neglect of elderly disaster victims, and differential recovery rates by age are retested on new data. Data described herein were gathered using survey techniques in two disaster stricken communities in Texas. Elderly victims' responses to the tornadoes are compared to a nonelderly (under sixty years of age) group to assess differences. Findings of previous research were, in many instances, supported although certain divergences between the current findings and preceding findings are noted, particularly in rates of recovery.
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North America suffers some of the most severe tornado disasters of any location on the planet. Significant injury and economic impact may result from these storms, particularly in rural areas. Tornadic storms present unique problems for prehospital and Emergency Department personnel. Soft tissue injuries seen after tornadoes are contaminated with polymicrobial flora and may require delayed primary closure. Fractures are a frequent cause of hospital admission and head injury is a frequent cause of death. Advanced warning and proper sheltering actions by a population are the most significant factors in reducing morbidity and mortality. This article reviews the pertinent literature on the medical impact of tornadoes and details the mechanisms of injury, nature of injuries, pre-hospital and ED planning points associated with tornadic storms.
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This study examines casualties from tornadoes in the United States between the years 1998 and 2000. A political model of human ecology (POET) was used to explore how the environment, technology, and social inequality influence rates of fatalities and injuries in two models. Data were drawn from four sources: John Hart's Severe Plot v2.0, National Weather Service (NWS) Warning Verification data, Storm Prediction Center (SPC) watch data, and tract-level census data. Negative binomial regression was used to analyze the causes of tornado fatalities and injuries. Independent variables (following POET) are classified in the following manner: population, organization, environment, and technology. Rural population, population density, and household size correspond to population; racial minorities and deprivation represent social organization; tornado area represents environment; and tornado watches and warnings, as well as mobile homes, correspond to technology. Findings suggest a strong relationship between the size of a tornado path and both fatalities and injuries, whereas other measures related to technology, population, and organization produce significant yet mixed results. Census tracts having larger populations of rural residents was, of the nonenvironmental factors, the most conclusive regarding its effects across the two models. The outcomes of analysis, although not entirely supportive of the model presented in this study, suggest to some degree that demographic and social factors play a role in vulnerability to tornadoes.
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Objective. County-level socioeconomic and demographic data were used to construct an index of social vulnerability to environmental hazards, called the Social Vulnerability Index (SoVI) for the United States based on 1990 data. Methods. Using a factor analytic approach, 42 variables were reduced to 11 independent factors that accounted for about 76 percent of the variance. These factors were placed in an additive model to compute a summary score-the Social Vulnerability Index. Results. There are some distinct spatial patterns in the SoVI, with the most vulnerable counties clustered in metropolitan counties in the east, south Texas, and the Mississippi Delta region. Conclusion. Those factors that contribute to the overall score often are different for each county, underscoring the interactive nature of social vulnerability-some components increase vulnerability; others moderate the effects.
Shared histories: Witsuwit’en-Settler relations in Smithers, British Columbia 1913-1973
  • T Mccreary
Ethnic and racial differences in tornado hazard perception, preparedness, and shelter lead time in Tuscaloosa
  • J C Senkbeil
  • D A Scott
  • P Guinazu-Walker
  • M S Rockman