Tornado Warnings

Joplin, a city in the southwest corner of Missouri, United States, suffered an EF-5 tornado in the late afternoon of 22 May 2011. This event, which claimed the lives of 162 people, represents the deadliest single tornado to strike the US since modern record-keeping began in 1950. This study examines the factors associated with responses to tornado warnings. Based on a post- tornado survey of survivors in Joplin, it reveals that tornado warnings were adequate and timely. Multivariate logistic regression identified four statistically significant determinants of compliance with tornado warnings: number of warning sources, whether respondents were at home when the tornado struck, past tornado experience, and gender. The findings suggest several recommendations, the implementation of which will further improve responses to tornado warnings.

On the evening of 22 May 2011, an EF-5 tornado tore a path six miles long across Joplin, Missouri, USA, killing 162 people as it passed through the heart of the city. This tornado stands as the deadliest single tornado to hit the United States since modern recordkeeping began in 1950, surpassing the tornado of 8 June 1953 that claimed 116 lives in Flint, Michigan. The record number of deaths caused by the single tornado in Joplin was far higher than the average annual number of US tornado deaths over the last three decades. This study explores the reasons for the high number of fatalities caused by the 2011 Joplin tornado. Questionnaire surveys administered among tornado survivors and informal discussions with emergency management personnel and others suggest that five reasons are associated with the high number of tornado fatalities experienced in Joplin: (1) the sheer magnitude of this event; (2) its path through commercial and densely populated residential areas; (3) the relatively large size of damage area; (4) the physical character- istics of affected homes in Joplin; and (5) the fact that some residents ignored tornado warnings. Several recommendations are offered, the implementation of which should reduce future tornado fatalities not only in Joplin, but elsewhere in the United States.

Emergency managers (EMs) play a critical role in communicating severe weather and tornado warnings to the public, yet communicating the uncertainty of when, where or if a tornado may hit remains a great challenge for EMs. Focus group and survey data concerning weather product usage, weather observing spotter interaction, and decisions to warn the public were collected from Oklahoma EMs in order to characterize the communication processes EMs employ during severe weather outbreaks. These processes include: (1) acquiring weather information, (2) interpreting the information in order to make weather hazard threat assessments, (3) verifying the information, and (4) making time-sensitive warning decisions. The results indicate that while EMs use a variety of weather and radar products to acquire information, weather observing spotters are key sources of verification data. With respect to warning the public about tornado threats, sirens are the primary method. These findings are related to the development of a new radar system being developed by the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), so that this new technology can be designed to reduce uncertainty in the EM decision-making and warning communication processes.

Despite improvements in tornado Disaster Risk Reduction (DRR), since the 1990s the number, and proportion, of people dying in tornadoes in America has increased. This paper examines how people rely, understand and trust tornado alerts and the Early Warning Systems (EWS) that disseminate them, if socio-demographics cause specific groups to experience greater risk, whether these factors have affected the rise in fatalities and what mitigation measures could reverse this.

Ford County, Kansas, was selected as a case study. Interviews were conducted with officials and an online survey marketed through Facebook was undertaken, receiving 547 responses. Results showed white men were particularly vulnerable to tornadoes as they were more likely to ignore warnings. Hispanics, older people and those with tornado experience were also at higher risk if they heard an alert from an EWS they distrusted or did not understand. Population growth in these groups and technology changes have helped cause the recent fatality rise and, unless changes are made to the EWS, the continued
increase in size of these groups will lead to more people becoming at risk from, or perishing in, tornadoes. Recommendations to prevent this include federal regulation and improved education materials for sirens, alerts translated into Spanish, discontinuing NOAA radio and developing an official forecast and alerting app.

"A massive tornado that tore a 6-mile path across southwestern Missouri killed 162 people as it raged through the heart of Joplin on the evening of 22 May 2011. This EF5 tornado, which at its zenith was three-quarters of a mile wide, levelled much of the city’s south side, and completely flattened some neighbourhoods, with leaves stripped from trees, the landscape took on an apocalyptic aura.

The Joplin event stands as the deadliest single tornado to hit the United States since modern record-keeping began in 1950, surpassing the 8 June 1953 tornado that claimed 116 lives in Flint, MI (Mustain 2011). In contrast to the horrific new record, 45 tornado fatalities were recorded in the United States during all of 2010, and just 21 stemmed from the 2009 calendar year. Average annual tornado deaths in the country were 55 for the period 2000-2010, but if the 554 deaths caused by 2011 tornadoes are added, the figure increases to 63.5. The record number of deaths caused by the single tornado in Joplin, MO, was far higher than the average number of yearly tornado deaths caused in the United States during the both time periods (i.e., 2000-2010 and 2000-2011). This study explores the reasons for the unexpectedly high number of fatalities caused by the 2011 Joplin, MO, tornado. This was accomplished by examining the nature and extent of warnings residents of Joplin, MO, received prior to the tornado touchdown and how they responded to these warnings."

This technical report highlights research carried out recently in OU-CIMMS’ Behavioural Insights Unit (BIU) in an attempt to draw together the wide-ranging literature related to tornado epidemiology. The literature drew from Centers for Disease Control (CDC) reports, grant reports and NOAA Service Assessments alongside academic journal articles for the first time. A key finding is that complexity exhibited by vectors of vulnerability is key to understanding drivers of risk, and how these impact on survivability. There is not one simple solution to reducing risk of fatality because there are multiple vulnerabilities which when coupled with the magnitude of the hazard (provided by the EF scale) all underpin varying degrees of risk that likely impact on survivability of tornadoes.