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1
Coleman, Timothy A., Kevin R. Knupp, James Spann, J. B. Elliott, and Brian E. Peters. "The History (and Future) of Tornado Warning Dissemination in the United States." Bulletin of the American Meteorological Society 92, no. 5 (May 1, 2011): 567–82. http://dx.doi.org/10.1175/2010bams3062.1.
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Since the successful tornado forecast at Tinker AFB in 1948 paved the way for the issuance of tornado warnings, the science of tornado detection and forecasting has advanced greatly. However, tornado warnings must be disseminated to the public to be of any use. The Texas tornado warning conferences in 1953 began to develop the framework for a modern tornado warning system and included radar detection of tornadoes, a spotter network, and improved communications between the U.S. Weather Bureau, spotters, and public officials, allowing more timely warnings and dissemination of those warnings to the public. Commercial radio and television are a main source of warnings for many, and the delivery methods on TV have changed much since 1960. NOAA Weather Radio (NWR) was launched after the 1974 Super Outbreak of tornadoes, with the most important feature being the tone alert that allowed receivers to alert people even when the radio broadcast was turned off. Today, NWR reaches most of the U.S. population, and Specific Area Message Encoding technology has improved its warning precision. Outdoor warning sirens, originally designed for use in enemy attack, were made available for use during tornado warnings around 1970. “Storm based” warnings, adopted by the National Weather Service in 2007, replaced countybased warnings and greatly reduce the warning area. As communications advances continue, tornado warnings will eventually be delivered to precise locations, using GPS and other location technology, through cellular telephones, outdoor sirens, e-mails, and digital television, in addition to NWR.
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Mason, Lisa Reyes, Kelsey N. Ellis, Betsy Winchester, and Susan Schexnayder. "Tornado Warnings at Night: Who Gets the Message?" Weather, Climate, and Society 10, no. 3 (June 29, 2018): 561–68. http://dx.doi.org/10.1175/wcas-d-17-0114.1.
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Abstract Nocturnal tornadoes are a public health threat, over twice as likely to have fatalities as tornadoes during the day. While tornado warning receipt is an important factor in models of individual behavioral response, receipt of warnings at night has not been studied in the literature to date. This study uses survey data from a random sample of Tennessee residents (N = 1804) who were randomly assigned to day or night versions of a near-identical survey instrument. Bivariate and logistic regression analyses compare chance of warning receipt, warning sources, and predictors of warning receipt for day versus night scenarios of a tornadic event. Over 80% of participants asked about a daytime tornado said there was a high/very high chance of receiving the warning, compared to fewer than 50% of participants asked about a nighttime event. Whereas demographic and cognitive factors helped predict tornado warning receipt during the day, cognitive and geographic factors were salient for the night. Perceived county risk and prior experience with a tornado were positively associated with chance of nighttime receipt, while belief that luck is an important factor in surviving a tornado and living in east (compared to west) Tennessee were negatively associated. Future research should consider partnering with the National Weather Service, emergency managers, and local media to increase the likelihood that people will receive tornado warnings at night and to better understand the role that cognitive factors and particular beliefs play in individual efforts to ensure that warnings are received.
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Simmons, Kevin M., and Daniel Sutter. "Tornado Warnings, Lead Times, and Tornado Casualties: An Empirical Investigation." Weather and Forecasting 23, no. 2 (April 1, 2008): 246–58. http://dx.doi.org/10.1175/2007waf2006027.1.
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Abstract Conventional wisdom holds that improved tornado warnings will reduce tornado casualties, because longer lead times on warnings provide extra opportunities to alert residents who can then take precautions. The relationship between warnings and casualties is examined using a dataset of tornadoes in the contiguous United States between 1986 and 2002. Two questions are examined: Does a warning issued on a tornado reduce the resulting number of fatalities and injuries? Do longer lead times reduce casualties? It is found that warnings have had a significant and consistent effect on tornado injuries, with a reduction of over 40% at some lead time intervals. The results for fatalities are mixed. An increase in lead time up to about 15 min reduces fatalities, while lead times longer than 15 min increase fatalities compared with no warning. The fatality results beyond 15 min, however, depend on five killer tornadoes and consequently are not robust.
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Brotzge, J., and S. Erickson. "Tornadoes without NWS Warning." Weather and Forecasting 25, no. 1 (February 1, 2010): 159–72. http://dx.doi.org/10.1175/2009waf2222270.1.
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Abstract During a 5-yr period of study from 2000 to 2004, slightly more than 26% of all reported tornadoes across the United States occurred without an NWS warning being issued. This study examines some of the reasons behind why no warnings were issued with these tornadoes, and what climatological, storm classification, and sociological factors may have played a role in the lack of warnings. This dataset of tornado records was sorted by F scale, geographically by region and weather forecast office (WFO), hour of the day, month of the year, tornado pathlength, tornado-to-radar distance, county population density, and number of tornadoes by day and order of occurrence. Results show that the tornadoes most likely to strike when the public is least likely to be aware were also those tornadoes with the greatest chance of not being warned. Singular tornado events (one tornado report per day within a WFO county warning area) and the first tornado report of the day were the most difficult scenarios on which to warn, with over half of all solitary tornado events not warned. Geographic areas that experienced a significant proportion of weak, solitary, and/or nocturnal tornadoes had a much higher ratio of missed warnings. In general, the stronger the tornado, as estimated from its F-scale rating and/or track length, the greater chance it was warned. However, the tornado distance from radar had a significant impact on tornado warning statistics. In addition, many weak tornadoes were not warned, and the overall ratio of missed tornado warnings to reported tornadoes actually increased over more densely populated regions, likely due to more complete postevent verification.
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Brotzge, J., and S. Erickson. "NWS Tornado Warnings with Zero or Negative Lead Times." Weather and Forecasting 24, no. 1 (February 1, 2009): 140–54. http://dx.doi.org/10.1175/2008waf2007076.1.
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Abstract During a 5-yr period of study from 2000 to 2004, slightly more than 10% of all National Weather Service (NWS) tornado warnings were issued either simultaneously as the tornado formed (i.e., with zero lead time) or minutes after initial tornado formation but prior to tornado dissipation (i.e., with “negative” lead time). This study examines why these tornadoes were not warned in advance, and what climate, storm morphology, and sociological factors may have played a role in delaying the issuance of the warning. This dataset of zero and negative lead time warnings are sorted by their F-scale ratings, geographically by region and weather forecast office (WFO), hour of the day, month of the year, tornado-to-radar distance, county population density, and number of tornadoes by day, hour, and order of occurrence. Two key results from this study are (i) providing advance warning on the first tornado of the day remains a difficult challenge and (ii) the more isolated the tornado event, the less likelihood that an advance warning is provided. WFOs that experience many large-scale outbreaks have a lower proportion of warnings with negative lead time than WFOs that experience many more isolated, one-tornado or two-tornado warning days. Monthly and geographic trends in lead time are directly impacted by the number of multiple tornado events. Except for a few isolated cases, the impacts of tornado-to-radar distance, county population density, and storm morphology did not have a significant impact on negative lead-time warnings.
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Strader, Stephen M., Alex M. Haberlie, and Alexandra G. Loitz. "Assessment of NWS County Warning Area Tornado Risk, Exposure, and Vulnerability." Weather, Climate, and Society 13, no. 2 (April 2021): 189–209. http://dx.doi.org/10.1175/wcas-d-20-0107.1.
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AbstractThis study investigates the interrelationships between National Weather Service (NWS) county warning area (CWA) tornado risk, exposure, and societal vulnerability. CWA climatological tornado risk is determined using historical tornado event data, and exposure and vulnerability are assessed by employing present-day population, housing, socioeconomic, and demographic metrics. In addition, tornado watches, warnings, warning lead times, false alarm warnings, and unwarned tornado reports are examined in relation to CWA risk, exposure, and vulnerability. Results indicate that southeastern U.S. CWAs are more susceptible to tornado impacts because of their greater tornado frequencies and larger damage footprints intersecting more vulnerable populations (e.g., poverty and manufactured homes). Midwest CWAs experience fewer tornadoes relative to Southeast and southern plains CWAs but encompass faster tornado translational speeds and greater population densities where higher concentrations of vulnerable individuals often reside. Northern plains CWAs contain longer-tracked tornadoes on average and larger percentages of vulnerable elderly and rural persons. Southern plains CWAs experience the highest tornado frequencies in general and contain larger percentages of minority Latinx populations. Many of the most socially vulnerable CWAs have shorter warning lead times and greater percentages of false alarm warnings and unwarned tornadoes. Study findings provide NWS forecasters with an improved understanding of the relationships between tornado risk, exposure, vulnerability, and warning outcomes within their respective CWAs. Findings may also assist NWS Weather Forecast Offices and the Warning Decision Training Division with developing training materials aimed at increasing NWS forecaster knowledge of how tornado risk, exposure, and vulnerability factors influence local tornado disaster potential.
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Anderson-Frey, Alexandra K., Yvette P. Richardson, Andrew R. Dean, Richard L. Thompson, and Bryan T. Smith. "Characteristics of Tornado Events and Warnings in the Southeastern United States." Weather and Forecasting 34, no. 4 (July 25, 2019): 1017–34. http://dx.doi.org/10.1175/waf-d-18-0211.1.
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Abstract The southeastern United States has become a prime area of focus in tornado-related literature due, in part, to the abundance of tornadoes occurring in high-shear low-CAPE (HSLC) environments. Through this analysis of 4133 tornado events and 16 429 tornado warnings in the southeastern United States, we find that tornadoes in the Southeast do indeed have, on average, higher shear and lower CAPE than tornadoes elsewhere in the contiguous United States (CONUS). We also examine tornado warning skill in the form of probability of detection (POD; percent of tornadoes receiving warning prior to tornado occurrence) and false alarm ratio (FAR; percent of tornado warnings for which no corresponding tornado is detected), and find that, on average, POD is better and FAR is worse for tornadoes in the Southeast than for the CONUS as a whole. These measures of warning skill remain consistent even when we consider only HSLC tornadoes. The Southeast also has nearly double the CONUS percentage of deadly tornadoes, with the highest percentage of these deadly tornadoes occurring during the spring, the winter, and around local sunset. On average, however, the tornadoes with the lowest POD also tend to be those that are weakest and least likely to be deadly; for the most part, the most dangerous storms are indeed being successfully warned.
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Sutter, Daniel, and Somer Erickson. "The Time Cost of Tornado Warnings and the Savings with Storm-Based Warnings." Weather, Climate, and Society 2, no. 2 (April 1, 2010): 103–12. http://dx.doi.org/10.1175/2009wcas1011.1.
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Abstract The authors examine the cost of time spent under tornado warnings issued annually by the National Weather Service (NWS). County-based tornado warnings imposed substantial costs on the nation: an average of 234 million person-hours spent under warnings annually between 1996 and 2004, with a value of $2.7 billion (U.S. dollars) per year. Counties are large relative to tornado damage areas; therefore, county-based warnings overwarned for tornadoes, warning many persons a safe distance from the storm and not in immediate danger. In October 2007 the NWS introduced storm-based warnings (SBW) for tornadoes, which are expected to reduce the area warned by 70%–75%. SBW consequently will reduce the time spent under warnings by over 160 million person-hours per year, with a value of $1.9 billion. The time spent under warnings does not measure the full cost to society because many people do not respond to the warnings. Adjusting for warning response, this study estimates that SBW might save 66 million person-hours actually spent sheltering a year with a value of $750 million. Sensitivity analysis indicates that the value of time spent sheltering saved by SBW exceeds $100 million per year with a probability of 0.95.
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Brotzge, Jerald A., Steven E. Nelson, Richard L. Thompson, and Bryan T. Smith. "Tornado Probability of Detection and Lead Time as a Function of Convective Mode and Environmental Parameters." Weather and Forecasting 28, no. 5 (October 1, 2013): 1261–76. http://dx.doi.org/10.1175/waf-d-12-00119.1.
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Abstract The ability to provide advanced warning on tornadoes can be impacted by variations in storm mode. This research evaluates 2 yr of National Weather Service (NWS) tornado warnings, verification reports, and radar-derived convective modes to appraise the ability of the NWS to warn across a variety of convective modes and environmental conditions. Several specific hypotheses are considered: (i) supercell morphologies are the easiest convective modes to warn for tornadoes and yield the greatest lead times, while tornadoes from more linear, nonsupercell convective modes, such as quasi-linear convective systems, are more difficult to warn for; (ii) parameters such as tornado distance from radar, population density, and tornado intensity (F scale) introduce significant and complex variability into warning statistics as a function of storm mode; and (iii) tornadoes from stronger storms, as measured by their mesocyclone strength (when present), convective available potential energy (CAPE), vertical wind shear, and significant tornado parameter (STP) are easier to warn for than tornadoes from weaker systems. Results confirmed these hypotheses. Supercell morphologies caused 97% of tornado fatalities, 96% of injuries, and 92% of damage during the study period. Tornado warnings for supercells had a statistically higher probability of detection (POD) and lead time than tornado warnings for nonsupercells; among supercell storms, tornadoes from supercells in lines were slightly more difficult to warn for than tornadoes from discrete or clusters of supercells. F-scale intensity and distance from radar had some impact on POD, with less impact on lead times. Higher mesocyclone strength (when applicable), CAPE, wind shear, and STP values were associated with greater tornado POD and lead times.
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Liu, Brooke Fisher, Michael Egnoto, and JungKyu Rhys Lim. "How Mobile Home Residents Understand and Respond to Tornado Warnings." Weather, Climate, and Society 11, no. 3 (May 21, 2019): 521–34. http://dx.doi.org/10.1175/wcas-d-17-0080.1.
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Abstract Mobile home residents experience higher fatality rates from tornadoes than “fixed home” residents. Yet, research on how mobile home residents understand and respond to tornado warnings is lacking. Such research can help meteorologists and their partners better communicate tornado risk. We conducted four surveys with residents of the southeastern United States. This region has the highest concentration of tornado fatalities and killer tornadoes, in part because of the high density of mobile homes. Findings reveal that today’s tornado warning system inadequately prepares mobile home residents to respond safely to tornadoes. The study offers recommendations for how to improve tornado communication for mobile and fixed home residents.
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Simmons, Kevin M., and Daniel Sutter. "WSR-88D Radar, Tornado Warnings, and Tornado Casualties." Weather and Forecasting 20, no. 3 (June 1, 2005): 301–10. http://dx.doi.org/10.1175/waf857.1.
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Abstract 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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Andrei, Simona, Meda Daniela Andrei, Mihăiţă Huştiu, Sorin Cheval, and Bogdan Antonescu. "Tornadoes in Romania—from Forecasting and Warning to Understanding Public’s Response and Expectations." Atmosphere 11, no. 9 (September 10, 2020): 966. http://dx.doi.org/10.3390/atmos11090966.
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Significant progress in tornado research and management can be claimed over the last few decades worldwide. However, tornado forecasting and warning continue to be permanent challenges for most European national meteorological services because they require particular skills and experience. Moreover, tornado warnings may generate panic. Therefore, one can remark that the main difficulties are related to (1) forecasting the tornado genesis, and (2) finding the most efficient way to communicate to the general public the possibility of tornado occurrence. This article presents the main characteristics of two convective events that occurred in Romania in order to emphasize the similarities and disparities between the tornado event (30 April 2019) and the non-tornado event (6 May 2019), from the warning perspective. Further, we investigate, for the first time in Romania, the general public’s comprehension, risk perception and reactions regarding the tornado events. The survey performed in 2020 emphasized that the Romanian public is able to recognize tornadoes (60%), understand the risks (over 80%), can manage the panic (over 70%), and is rather desirous to receive clear (over 90%) and real-time (95%) tornado warnings. The lessons learned may support the further development of tornado forecasting and warning procedures, and foster the public’s awareness related to tornado events.
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Ash, Kevin D., Ronald L. Schumann, and Gregg C. Bowser. "Tornado Warning Trade-Offs: Evaluating Choices for Visually Communicating Risk." Weather, Climate, and Society 6, no. 1 (January 1, 2014): 104–18. http://dx.doi.org/10.1175/wcas-d-13-00021.1.
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Abstract Recent improvements in weather observation and monitoring have increased the precision of tornado warnings. The National Weather Service currently issues storm-based tornado warnings, and even more geographically specific warnings that include probability information are under development. At the same time, the widespread proliferation of smartphone and mobile computing technology supports the rapid dissemination of graphical weather warning information. Some broadcasters and private companies have already begun using probabilistic-style tornado warning graphics. However, the development of these new types of warnings has occurred with limited research on how users interpret probabilistic visualizations. This study begins filling this void by examining responses to color scheme and relative position using probabilistic tornado warning designs. A survey of university students is used to measure the level of perceived fear and likelihood of protective action for a series of hypothetical warning scenarios. Central research questions investigate 1) differences in responses across warning designs, 2) clustering of extreme responses in each design, 3) trends in responses with respect to probability levels, 4) differences in responses inside versus outside the warnings, and 5) differences in responses near the edges of the warning designs. Results suggest a variety of trade-offs in viewer responses to tornado warnings based on visual design choices. These findings underscore the need for more comprehensive research on visualizations in weather hazard communication that can aid meteorologists in effectively warning the public and spur appropriate tornado protection behaviors in a timely manner.
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Simmons, Kevin M., and Daniel Sutter. "False Alarms, Tornado Warnings, and Tornado Casualties." Weather, Climate, and Society 1, no. 1 (October 1, 2009): 38–53. http://dx.doi.org/10.1175/2009wcas1005.1.
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Abstract This paper extends prior research on the societal value of tornado warnings to the impact of false alarms. Intuition and theory suggest that false alarms will reduce the response to warnings, yet little evidence of a “false alarm effect” has been unearthed. This paper exploits differences in the false-alarm ratio across the United States to test for a false-alarm effect in a regression model of tornado casualties from 1986 to 2004. A statistically significant and large false-alarm effect is found: tornadoes that occur in an area with a higher false-alarm ratio kill and injure more people, everything else being constant. The effect is consistent across false-alarm ratios defined over different geographies and time intervals. A one-standard-deviation increase in the false-alarm ratio increases expected fatalities by between 12% and 29% and increases expected injuries by between 14% and 32%. The reduction in the national tornado false-alarm ratio over the period reduced fatalities by 4%–11% and injuries by 4%–13%. The casualty effects of false alarms and warning lead times are approximately equal in magnitude, suggesting that the National Weather Service could not reduce casualties by trading off a higher probability of detection for a higher false-alarm ratio, or vice versa.
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Anderson-Frey, Alexandra K., Yvette P. Richardson, Andrew R. Dean, Richard L. Thompson, and Bryan T. Smith. "Investigation of Near-Storm Environments for Tornado Events and Warnings." Weather and Forecasting 31, no. 6 (November 7, 2016): 1771–90. http://dx.doi.org/10.1175/waf-d-16-0046.1.
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Abstract In this study, a 13-yr climatology of tornado event and warning environments, including metrics of tornado intensity and storm morphology, is investigated with particular focus on the environments of tornadoes associated with quasi-linear convective systems and right-moving supercells. The regions of the environmental parameter space having poor warning performance in various geographical locations, as well as during different times of the day and year, are highlighted. Kernel density estimations of the tornado report and warning environments are produced for two parameter spaces: mixed-layer convective available potential energy (MLCAPE) versus 0–6-km vector shear magnitude (SHR6), and mixed-layer lifting condensation level (MLLCL) versus 0–1-km storm-relative helicity (SRH1). The warning performance is best in environments characteristic of severe convection (i.e., environments featuring large values of MLCAPE and SHR6). For tornadoes occurring during the early evening transition period, MLCAPE is maximized, MLLCL heights decrease, SHR6 and SRH1 increase, tornadoes rated as 2 or greater on the enhanced Fujita scale (EF2+) are most common, the probability of detection is relatively high, and false alarm ratios are relatively low. Overall, the parameter-space distributions of warnings and events are similar; at least in a broad sense, there is no systematic problem with forecasting that explains the high overall false alarm ratio, which instead seems to stem from the inability to know which storms in a given environment will be tornadic.
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Walters, Jayme E., Lisa Reyes Mason, Kelsey Ellis, and Betsy Winchester. "Staying Safe in a Tornado: A Qualitative Inquiry into Public Knowledge, Access, and Response to Tornado Warnings." Weather and Forecasting 35, no. 1 (January 13, 2020): 67–81. http://dx.doi.org/10.1175/waf-d-19-0090.1.
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Abstract Tornadoes in the southeastern United States continue to cause substantial injury, death, and destruction. The present study seeks to 1) understand inadequate warning access, less understanding, and/or less likelihood of responding to tornado warnings; 2) examine public attitudes about NWS communications; and 3) explore the perceptions of NWS personnel regarding public response to tornado warnings, factors that might influence response, and how their perceptions impact their communication. Participants include a purposive sample of NWS forecasters in Tennessee (n = 11) and residents (n = 45) who were identified as having low access to, low knowledge of, or an unsafe response to tornado warnings in a previous study. A qualitative approach with semistructured interviews was used. Findings indicated that most participants had at least one warning source. Barriers to warning access included electricity outages, rurality, lack of storm radio, heavy sleeping, and hearing impairments. Most participants had knowledge of NWS guidelines for safe shelter seeking but still engaged in behaviors considered unsafe. Proximity, personal experience, and influence of family and friends emerged as influencers of response to warnings. NWS personnel perceived that proximity played a significant role in shelter-seeking behavior as well as the need for confirmation. Poor access to safe shelter arose as a major concern for NWS personnel, specifically mobile home residents. Messaging and specificity in warnings to evoke safe shelter-seeking behavior surfaced as critical issues for NWS personnel. Implications for education and policy changes to enhance public safety and improve public health are noted.
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Blair, Scott F., and Jared W. Leighton. "Assessing Real-Time Tornado Information Disseminated through NWS Products." Weather and Forecasting 29, no. 3 (June 1, 2014): 591–600. http://dx.doi.org/10.1175/waf-d-13-00126.1.
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Abstract Real-time confirmation of a tornado specified in National Weather Service (NWS) warnings and statements is believed to increase the credibility and urgency of these critical warning messages for the end user, because it represents the greatest degree of certainty that the hazard exists. This timely tornado information disseminated in official NWS products and relayed through multiple sources by private and public partners may help the public believe, personalize, confirm, and respond to the warning message. This is the first study to explicitly assess the frequency of real-time confirmation of ongoing tornadoes within NWS products and explore what unique conditions may facilitate or hinder this process. Tornado reports and their respective NWS warnings and statements during a 5-yr period from 2007 to 2011 across the central contiguous United States were compiled and examined. Overall, 40% of tornadoes were confirmed in NWS products in real time. Increasing tornado pathlength, duration, and intensity subsequently resulted in an increasing likelihood of real-time confirmation prior to the tornado dissipating. The time of day was a factor; nighttime tornadoes were 20% less likely to receive real-time confirmation than daytime events. Additionally, increasing tornado forecast risk in products issued by the Storm Prediction Center corresponded to an increasing likelihood of real-time confirmation. Analysis of these data reveals specific scenarios when tornadoes are more or less likely to be reported in real time, providing some guidance for when timely ground-truth information may or may not be available.
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O’Brien, Marita A., and Clarke Peterson. "Age Differences in Tornado Warning Responses and Emotions." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 61, no. 1 (September 2017): 26–30. http://dx.doi.org/10.1177/1541931213601501.
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Empowering tornado-prone community residents to effectively prepare for and respond to tornado warnings is a significant challenge for public safety. Although several studies have investigated participant knowledge, response intentions and behavior to different warnings, few studies have evaluated actual responses to tornado warnings from a sufficiently large sample to reveal the greatest challenges and opportunities for increasing compliance. This study examined warning knowledge and tornado experiences of 30 college students and 30 older community residents in two tornado-prone states. Findings corroborated prior research but also highlighted the need to understand how information gathering supports individual judgments of warning relevance at specific times and locations. We also found age differences in the type of information utilized to make these judgments, highlighting the need for focused community education and communication. Analysis of tornado aftermath emotional experiences particularly supports the NWS’s proposal to exploit disaster aftermath priming to increase compliance.
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Black, Alan W., and Walker S. Ashley. "The Relationship between Tornadic and Nontornadic Convective Wind Fatalities and Warnings." Weather, Climate, and Society 3, no. 1 (January 1, 2011): 31–47. http://dx.doi.org/10.1175/2010wcas1094.1.
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Abstract A database of tornado fatalities, nontornadic convective wind fatalities, severe thunderstorm warnings, and tornado warnings was compiled for the period 1986–2007 to assess the spatial and temporal distribution of warned and unwarned fatalities. The time of fatality and location as reported in Storm Data was compared to tornado and severe thunderstorm warnings to determine if a warning was in effect when the fatality occurred. Overall, 23.7% of tornado fatalities were unwarned, while 53.2% of nontornadic convective wind fatalities were unwarned. Most unwarned tornado fatalities occurred prior to the mid-1990s—coinciding with modernization of the National Weather Service—while unwarned nontornadic convective wind fatalities remained at a relatively elevated frequency throughout the study period. Geographic locations with high numbers of unwarned tornado and nontornadic convective wind fatalities were associated with one high-magnitude event that was unwarned rather than a series of smaller unwarned events over the period. There are many factors that contribute to warning response by the public, and the issuance of a severe thunderstorm or tornado warning is an important initial step in the warning process. A better understanding of the characteristics of warned and unwarned fatalities is important to future reduction of unwarned fatalities.
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Steinkruger, Dylan, Paul Markowski, and George Young. "An Artificially Intelligent System for the Automated Issuance of Tornado Warnings in Simulated Convective Storms." Weather and Forecasting 35, no. 5 (October 1, 2020): 1939–65. http://dx.doi.org/10.1175/waf-d-19-0249.1.
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AbstractThe utility of employing artificial intelligence (AI) to issue tornado warnings is explored using an ensemble of 128 idealized simulations. Over 700 tornadoes develop within the ensemble of simulations, varying in duration, length, and associated storm mode. Machine-learning models are trained to forecast the temporal and spatial probabilities of tornado formation for a specific lead time. The machine-learning probabilities are used to produce tornado warning decisions for each grid point and lead time. An optimization function is defined, such that warning thresholds are modified to optimize the performance of the AI system on a specified metric (e.g., increased lead time, minimized false alarms, etc.). Using genetic algorithms, multiple AI systems are developed with different optimization functions. The different AI systems yield unique warning output depending on the desired attributes of the optimization function. The effects of the different optimization functions on warning performance are explored. Overall, performance is encouraging and suggests that automated tornado warning guidance is worth exploring with real-time data.
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Sanders, Shadya, Terri Adams, and Everette Joseph. "Severe Weather Forecasts and Public Perceptions: An Analysis of the 2011 Super Outbreak in Tuscaloosa, Alabama." Weather, Climate, and Society 12, no. 3 (July 1, 2020): 473–85. http://dx.doi.org/10.1175/wcas-d-18-0090.1.
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AbstractThis paper uses the “Super Outbreak” of 2011 as a case study to examine the potential gaps between the dissemination of severe weather warnings and the public’s behavioral response to this information. This study focuses on a single tornado track that passed through Tuscaloosa, Alabama. The tornado caused massive damage and destruction and led to a total of 62 fatalities. The threat of severe storms was known days in advance, and forecasts were disseminated to the public. Questions were raised about the forecasts, warning lead times, and the perception of the warnings among residents. This paper examines the potential gaps that exist between the dissemination of tornadic warning information and citizen response. The analysis of data collected through a mixed-method approach suggests that, regardless of weather forecast accuracy, a significant chasm exists between the dissemination of warnings and the personalizing of risks, which results in limited use of protective measures in the face of severe weather threats.
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Schumacher, Russ S., Daniel T. Lindsey, Andrea B. Schumacher, Jeff Braun, Steven D. Miller, and Julie L. Demuth. "Multidisciplinary Analysis of an Unusual Tornado: Meteorology, Climatology, and the Communication and Interpretation of Warnings*." Weather and Forecasting 25, no. 5 (October 1, 2010): 1412–29. http://dx.doi.org/10.1175/2010waf2222396.1.
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Abstract On 22 May 2008, a strong tornado—rated EF3 on the enhanced Fujita scale, with winds estimated between 136 and 165 mi h−1 (61 and 74 m s−1)—caused extensive damage along a 55-km track through northern Colorado. The worst devastation occurred in and around the town of Windsor, and in total there was one fatality, numerous injuries, and hundreds of homes significantly damaged or destroyed. Several characteristics of this tornado were unusual for the region from a climatological perspective, including its intensity, its long track, its direction of motion, and the time of day when it formed. These unusual aspects and the high impact of this tornado also raised a number of questions about the communication and interpretation of information from National Weather Service watches and warnings by decision makers and the public. First, the study examines the meteorological circumstances responsible for producing such an outlier to the regional severe weather climatology. An analysis of the synoptic and mesoscale environmental conditions that were favorable for significant tornadoes on 22 May 2008 is presented. Then, a climatology of significant tornadoes (defined as those rated F2 or higher on the Fujita scale, or EF2 or higher on the Enhanced Fujita scale) near the Front Range is shown to put the 22 May 2008 event into climatological context. This study also examines the communication and interpretation of severe weather information in an area that experiences tornadoes regularly but is relatively unaccustomed to significant tornadoes. By conducting interviews with local decision makers, the authors have compiled and chronicled the flow of information as the event unfolded. The results of these interviews demonstrate that the initial sources of warning information varied widely. Decision makers’ interpretations of the warnings also varied, which led to different perceptions on the timeliness and clarity of the warning information. The decision makers’ previous knowledge of the typical local characteristics of tornadoes also affected their interpretations of the tornado threat. The interview results highlight the complex series of processes by which severe weather information is communicated after a warning is issued by the National Weather Service. The results of this study support the growing recognition that societal factors are just as important to the effectiveness of weather warnings as the timeliness of and information provided in those warnings, and that these factors should be considered in future research in addition to the investments and attention given to improving detection and warning capabilities.
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Brotzge, J., S. Erickson, and H. Brooks. "A 5-yr Climatology of Tornado False Alarms." Weather and Forecasting 26, no. 4 (August 1, 2011): 534–44. http://dx.doi.org/10.1175/waf-d-10-05004.1.
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Abstract During 2008 approximately 75% of tornado warnings issued by the National Weather Service (NWS) were false alarms. This study investigates some of the climatological trends in the issuance of false alarms and highlights several factors that impact false-alarm ratio (FAR) statistics. All tornadoes and tornado warnings issued across the continental United States between 2000 and 2004 were analyzed, and the data were sorted by hour of the day, month of the year, geographical region and weather forecast office (WFO), the number of tornadoes observed on a day in which a false alarm was issued, distance of the warned area from the nearest NWS radar, county population density, and county area. Analysis of the tornado false-alarm data identified six specific trends. First, the FAR was highest during nonpeak storm periods, such as during the night and during the winter and late summer. Second, the FAR was strongly tied to the number of tornadoes warned per day. Nearly one-third of all false alarms were issued on days when no tornadoes were confirmed within the WFO’s county warning area. Third, the FAR varied with distance from radar, with significantly lower estimates found beyond 150 km from radar. Fourth, the FAR varied with population density. For warnings within 50 km of an NWS radar, FAR increased with population density; however, for warnings beyond 150 km from radar, FAR decreased regardless of population density. Fifth, the FAR also varied as a function of county size. The FAR was generally highest for the smallest counties; the FAR was ~80% for all counties less than 1000 km2 regardless of distance from radar. Finally, the combined effects of distance from radar, population density, and county size led to significant variability across geographic regions.
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Schultz, David M., Eve C. Gruntfest, Mary H. Hayden, Charles C. Benight, Sheldon Drobot, and Lindsey R. Barnes. "Decision Making by Austin, Texas, Residents in Hypothetical Tornado Scenarios*." Weather, Climate, and Society 2, no. 3 (July 1, 2010): 249–54. http://dx.doi.org/10.1175/2010wcas1067.1.
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Abstract One of the goals of the Warning Project is to understand how people receive warnings of hazardous weather and subsequently use this information to make decisions. As part of the project, 519 surveys from Austin, Texas, floodplain residents were collected and analyzed. About 90% of respondents understood that a tornado warning represented a more serious and more likely threat than a tornado watch. Most respondents (86%) were not concerned about a limited number of false alarms or close calls reducing their confidence in future warnings, suggesting no cry-wolf effect. Most respondents reported safe decisions in two hypothetical scenarios: a tornado warning issued while the respondent was home and a tornado visible by the respondent while driving. However, nearly half the respondents indicated that they would seek shelter from a tornado under a highway overpass if they were driving. Despite the limitations of this study, these results suggest that more education is needed on the dangers of highway overpasses as shelter from severe weather.
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Drost, Robert, Mark Casteel, Julie Libarkin, Stephen Thomas, and Matt Meister. "Severe Weather Warning Communication: Factors Impacting Audience Attention and Retention of Information during Tornado Warnings." Weather, Climate, and Society 8, no. 4 (September 2, 2016): 361–72. http://dx.doi.org/10.1175/wcas-d-15-0035.1.
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Abstract Weather hazards in the United States inflict both personal and economic tolls on the public. Communicating warnings about weather hazards is an important duty of TV weathercasters. Televised weather warnings are typically conveyed through live radar, live coverage, and warning scrolls. However, these traditional approaches may not be entirely effective given the limited attention some members of the public pay to these warnings. A study comparing individual responses to a traditional warning, an animated warning, and an audio warning was undertaken to evaluate the impact of delivery methods on viewer attention, retention, and preferences during viewing of severe weather warnings. A Tobii T60 eye tracker was used to document visual interactions with on-screen warnings and surveys were used to collect evidence of warning retention and preference. Demographic variables were also collected to describe the study population. Results indicate that viewers of the animated warning retained more pertinent information about the tornado warning than viewers of the traditional warning, and retention during the traditional warning was equivalent to that of the audio warning. In addition, gaze patterns for the traditional warning were much more diffuse than for the animated warning, suggesting that attention was more focused on the animation than the live video. In addition, modifications to reduce visual complexity of traditional warnings may positively impact viewer attention to individual warning elements. Future studies will consider the effectiveness of a hybrid warning containing both traditional and animated components. The current research study can be used to advance current severe weather warning communication techniques and increase public awareness during severe weather events.
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Antonescu, Bogdan, David M. Schultz, Alois Holzer, and Pieter Groenemeijer. "Tornadoes in Europe: An Underestimated Threat." Bulletin of the American Meteorological Society 98, no. 4 (April 1, 2017): 713–28. http://dx.doi.org/10.1175/bams-d-16-0171.1.
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Abstract The social and economic impact of tornadoes in Europe is analyzed using tornado reports from the European Severe Weather Database between 1950 and 2015. Despite what is often assumed by the general public and even by meteorologists and researchers, tornadoes do occur in Europe and they are associated with injuries, fatalities, and damages, although their reported frequencies and intensities are lower compared with the United States. Currently, the threat of tornadoes to Europe is underestimated. Few European meteorological services have developed and maintained tornado databases and even fewer have issued tornado warnings. This article summarizes our current understanding of the tornado threat to Europe by showing the changes in tornado injuries and fatalities since the 1950s and by estimating for the first time the damages associated with European tornadoes. To increase awareness of tornadoes and their threat to Europe, we propose a strategy that includes 1) collaboration between meteorological services, researchers, and the general public toward a pan-European database; 2) development of national forecasting and warning systems and of pan-European convective outlooks; and 3) development by decision-makers and emergency managers of policies and strategies that include tornadoes.
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Brooks, Harold E., and James Correia. "Long-Term Performance Metrics for National Weather Service Tornado Warnings." Weather and Forecasting 33, no. 6 (October 31, 2018): 1501–11. http://dx.doi.org/10.1175/waf-d-18-0120.1.
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Abstract Tornado warnings are one of the flagship products of the National Weather Service. We update the time series of various metrics of performance in order to provide baselines over the 1986–2016 period for lead time, probability of detection, false alarm ratio, and warning duration. We have used metrics (mean lead time for tornadoes warned in advance, fraction of tornadoes warned in advance) that work in a consistent way across the official changes in policy for warning issuance, as well as across points in time when unofficial changes took place. The mean lead time for tornadoes warned in advance was relatively constant from 1986 to 2011, while the fraction of tornadoes warned in advance increased through about 2006, and the false alarm ratio slowly decreased. The largest changes in performance take place in 2012 when the default warning duration decreased, and there is an apparent increased emphasis on reducing false alarms. As a result, the lead time, probability of detection, and false alarm ratio all decrease in 2012. Our analysis is based, in large part, on signal detection theory, which separates the quality of the warning system from the threshold for issuing warnings. Threshold changes lead to trade-offs between false alarms and missed detections. Such changes provide further evidence for changes in what the warning system as a whole considers important, as well as highlighting the limitations of measuring performance by looking at metrics independently.
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Nixon, Cameron J., and John T. Allen. "Anticipating Deviant Tornado Motion Using a Simple Hodograph Technique." Weather and Forecasting 36, no. 1 (February 2021): 219–35. http://dx.doi.org/10.1175/waf-d-20-0056.1.
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AbstractThe paths of tornadoes have long been a subject of fascination since the meticulously drawn damage tracks by Dr. Tetsuya Theodore “Ted” Fujita. Though uncommon, some tornadoes have been noted to take sudden left turns from their previous path. This has the potential to present an extreme challenge to warning lead time, and the spread of timely, accurate information to broadcasters and emergency managers. While a few hypotheses exist as to why tornadoes deviate, none have been tested for their potential use in operational forecasting and nowcasting. As a result, such deviations go largely unanticipated by forecasters. A sample of 102 leftward deviant tornadic low-level mesocyclones was tracked via WSR-88D and assessed for their potential predictability. A simple hodograph technique is presented that shows promising skill in predicting the motion of deviant tornadoes, which, upon “occlusion,” detach from the parent storm’s updraft centroid and advect leftward or rearward by the low-level wind. This metric, a vector average of the parent storm motion and the mean wind in the lowest half-kilometer, proves effective at anticipating deviant tornado motion with a median error of less than 6 kt (1 kt ≈ 0.51 m s−1). With over 25% of analyzed low-level mesocyclones deviating completely out of the tornado warning polygon issued by their respective National Weather Service Weather Forecast Office, the adoption of this new technique could improve warning performance. Furthermore, with over 35% of tornadoes becoming “deviant” almost immediately upon formation, the ability to anticipate such events may inspire a new paradigm for tornado warnings that, when covering unpredictable behavior, are proactive instead of reactive.
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Jauernic, Sabrina T., and Matthew S. Van Den Broeke. "Tornado Warning Response and Perceptions among Undergraduates in Nebraska." Weather, Climate, and Society 9, no. 2 (February 13, 2017): 125–39. http://dx.doi.org/10.1175/wcas-d-16-0031.1.
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Abstract Few studies show how university students perceive and respond to tornado warnings. Lacking in the literature are investigations of what influences perceptions of tornado risk among this population and how these perceptions may influence actions. Through an online survey of 640 undergraduates enrolled at a large university in Nebraska, significant relationships were found between student demographics, perceptions, and response actions. Tornado mythology relevant to the local city influenced perceptions so that students felt the city was less at risk than surrounding rural land. Confirming risk before sheltering remained popular, with some students choosing to never seek shelter during a warning. International students were more likely to initially seek shelter during a warning but had difficulty interpreting warning polygons or accurately choosing the best safety actions. Tornado-related education resulted in international students being more likely to have safety plans and shelter in more appropriate locations. Most domestic students correctly identified safe areas in which to shelter, but fewer knew the precise meaning of a tornado warning polygon. Parents/guardians and the school were the most popular tornado knowledge sources for domestic students, while friends and self-education were popular with international students. Respondents seemed willing to learn more about tornadoes and perceived a lack of tornado-related resources available on campus. This implies that more thorough tornado education and information dissemination on university campuses is warranted. Faster personalization of risk, dispelling local myths, and educating those new to tornado-prone locations should be emphasized.
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Hoekstra, S., K. Klockow, R. Riley, J. Brotzge, H. Brooks, and S. Erickson. "A Preliminary Look at the Social Perspective of Warn-on-Forecast: Preferred Tornado Warning Lead Time and the General Public’s Perceptions of Weather Risks." Weather, Climate, and Society 3, no. 2 (April 1, 2011): 128–40. http://dx.doi.org/10.1175/2011wcas1076.1.
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Abstract Tornado warnings are currently issued an average of 13 min in advance of a tornado and are based on a warn-on-detection paradigm. However, computer model improvements may allow for a new warning paradigm, warn-on-forecast, to be established in the future. This would mean that tornado warnings could be issued one to two hours in advance, prior to storm initiation. In anticipation of the technological innovation, this study inquires whether the warn-on-forecast paradigm for tornado warnings may be preferred by the public (i.e., individuals and households). The authors sample is drawn from visitors to the National Weather Center in Norman, Oklahoma. During the summer and fall of 2009, surveys were distributed to 320 participants to assess their understanding and perception of weather risks and preferred tornado warning lead time. Responses were analyzed according to several different parameters including age, region of residency, educational level, number of children, and prior tornado experience. A majority of the respondents answered many of the weather risk questions correctly. They seemed to be familiar with tornado seasons; however, they were unaware of the relative number of fatalities caused by tornadoes and several additional weather phenomena each year in the United States. The preferred lead time was 34.3 min according to average survey responses. This suggests that while the general public may currently prefer a longer average lead time than the present system offers, the preference does not extend to the 1–2-h time frame theoretically offered by the warn-on-forecast system. When asked what they would do if given a 1-h lead time, respondents reported that taking shelter was a lesser priority than when given a 15-min lead time, and fleeing the area became a slightly more popular alternative. A majority of respondents also reported the situation would feel less life threatening if given a 1-h lead time. These results suggest that how the public responds to longer lead times may be complex and situationally dependent, and further study must be conducted to ascertain the users for whom the longer lead times would carry the most value. These results form the basis of an informative stated-preference approach to predicting public response to long (>1 h) warning lead times, using public understanding of the risks posed by severe weather events to contextualize lead-time demand.
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Lim, JungKyu Rhys, Brooke Fisher Liu, and Michael Egnoto. "Cry Wolf Effect? Evaluating the Impact of False Alarms on Public Responses to Tornado Alerts in the Southeastern United States." Weather, Climate, and Society 11, no. 3 (June 11, 2019): 549–63. http://dx.doi.org/10.1175/wcas-d-18-0080.1.
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Abstract On average, 75% of tornado warnings in the United States are false alarms. Although forecasters have been concerned that false alarms may generate a complacent public, only a few research studies have examined how the public responds to tornado false alarms. Through four surveys (N = 4162), this study examines how residents in the southeastern United States understand, process, and respond to tornado false alarms. The study then compares social science research findings on perceptions of false alarms to actual county false alarm ratios and the number of tornado warnings issued by counties. Contrary to prior research, findings indicate that concerns about false alarm ratios generating a complacent public may be overblown. Results show that southeastern U.S. residents estimate tornado warnings to be more accurate than they are. Participants’ perceived false alarm ratios are not correlated with actual county false alarm ratios. Counterintuitively, the higher individuals perceive false alarm ratios and tornado alert accuracy to be, the more likely they are to take protective behavior such as sheltering in place in response to tornado warnings. Actual country false alarm ratios and the number of tornado warnings issued did not predict taking protective action.
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Anderson-Frey, Alexandra K., Yvette P. Richardson, Andrew R. Dean, Richard L. Thompson, and Bryan T. Smith. "Self-Organizing Maps for the Investigation of Tornadic Near-Storm Environments." Weather and Forecasting 32, no. 4 (July 13, 2017): 1467–75. http://dx.doi.org/10.1175/waf-d-17-0034.1.
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Abstract In this work, self-organizing maps (SOMs) are used to investigate patterns of favorable near-storm environmental parameters in a 13-yr climatology of 14 814 tornado events and 44 961 tornado warnings across the continental United States. Establishing nine statistically distinct clusters of spatial distributions of the significant tornado parameter (STP) in the 480 km × 480 km region surrounding each tornado event or warning allows for the examination of each cluster in isolation. For tornado events, distinct patterns are associated more with particular times of day, geographical locations, and times of year. For example, the archetypal springtime dryline setup in the Great Plains emerges readily from the data. While high values of STP tend to correspond to relatively high probabilities of detection (PODs) and relatively low false alarm ratios (FARs), the majority of tornado events occur within a pattern of uniformly lower STP, with relatively high FAR and low POD. Overall, the two-dimensional plots produced by the SOM approach provide an intuitive way of creating nuanced climatologies of tornadic near-storm environments.
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Chaney, Philip L., and Greg S. Weaver. "The Vulnerability of Mobile Home Residents in Tornado Disasters: The 2008 Super Tuesday Tornado in Macon County, Tennessee." Weather, Climate, and Society 2, no. 3 (July 1, 2010): 190–99. http://dx.doi.org/10.1175/2010wcas1042.1.
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Abstract Mobile home residents are known to be highly vulnerable to tornadoes and account for a considerable portion of tornado-related fatalities. The problem is partially related to the limited protection provided by the structure; however, shortcomings in preparedness and response to warnings may also play a role. This study investigated mobile home resident preparedness and responses to warnings for identifying areas where they might be more vulnerable than permanent home residents (brick and wood-frame houses). The study site was Macon County, Tennessee, which reported the highest number of fatalities during the 2008 Super Tuesday tornado outbreak. A post-disaster survey was conducted within days of the disaster, and the study group included 127 local residents: 35% mobile home (MH) residents, 61% permanent home (PH) residents, and 4% other. An unconditional exact test was used to test for statistical significance (0.05 level) because the sample was nonrandom. The MH residents were less prepared than the PH residents in all six categories evaluated. The difference was significant in having participated in a tornado drill, having a tornado-resistant shelter on the premises, and having an emergency response plan for seeking shelter. The MH residents were also less likely to follow the plan, and the difference was significant. Furthermore, the MH residents were much less likely to take shelter in a safe location. Preparedness factors that promoted higher evacuation rates among MH residents included having participated in a tornado drill, understanding the definition of a tornado warning, and having a plan for seeking shelter.
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Stumpf, Gregory J., and Alan E. Gerard. "National Weather Service Severe Weather Warnings as Threats-in-Motion." Weather and Forecasting 36, no. 2 (April 2021): 627–43. http://dx.doi.org/10.1175/waf-d-20-0159.1.
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AbstractThreats-in-Motion (TIM) is a warning generation approach that would enable the NWS to advance severe thunderstorm and tornado warnings from the current static polygon system to continuously updating polygons that move forward with a storm. This concept is proposed as a first stage for implementation of the Forecasting a Continuum of Environmental Threats (FACETs) paradigm, which eventually aims to deliver rapidly updating probabilistic hazard information alongside NWS warnings, watches, and other products. With TIM, a warning polygon is attached to the threat and moves forward along with it. This provides more uniform, or equitable, lead time for all locations downstream of the event. When forecaster workload is high, storms remain continually tracked and warned. TIM mitigates gaps in warning coverage and improves the handling of storm motion changes. In addition, warnings are automatically cleared from locations where the threat has passed. This all results in greater average lead times and lower average departure times than current NWS warnings, with little to no impact to average false alarm time. This is particularly noteworthy for storms expected to live longer than the average warning duration (30 or 45 min) such as long-tracked supercells that are more prevalent during significant tornado outbreaks.
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Howard, Seth P., Kim E. Klockow-McClain, Alison P. Boehmer, and Kevin M. Simmons. "Firm Behavior in the Face of Severe Weather: Economic Analysis between Probabilistic and Deterministic Warnings." Weather and Forecasting 36, no. 3 (June 2021): 757–67. http://dx.doi.org/10.1175/waf-d-20-0107.1.
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AbstractTornadoes cause billions of dollars in damage and over 100 fatalities on average annually. Yet, an indirect cost to these storms is found in lost sales and/or lost productivity from responding to over 2000 warnings per year. This project responds to the Weather Research and Forecasting Innovation Act of 2017, H.R. 353, which calls for the use of social and behavioral science to study and improve storm warning systems. Our goal is to provide an analysis of cost avoidance that could accrue from a change to the warning paradigm, particularly to include probabilistic hazard information at storm scales. A survey of nearly 500 firms was conducted in and near the Dallas–Fort Worth metropolitan area asking questions about experience with tornadoes, sources of information for severe weather, expected cost of responding to tornado warnings, and how the firm would respond to either deterministic or probabilistic warnings. We find a dramatic change from deterministic warnings compared to the proposed probabilistic and that a probabilistic information system produces annual cost avoidance in a range of $2.3–$7.6 billion (U.S. dollars) compared to the current deterministic warning paradigm.
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Heinselman, Pamela, Daphne LaDue, Darrel M. Kingfield, and Robert Hoffman. "Tornado Warning Decisions Using Phased-Array Radar Data." Weather and Forecasting 30, no. 1 (February 1, 2015): 57–78. http://dx.doi.org/10.1175/waf-d-14-00042.1.
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Abstract The 2012 Phased Array Radar Innovative Sensing Experiment identified how rapidly scanned full-volumetric data captured known mesoscale processes and impacted tornado-warning lead time. Twelve forecasters from nine National Weather Service forecast offices used this rapid-scan phased-array radar (PAR) data to issue tornado warnings on two low-end tornadic and two nontornadic supercell cases. Verification of the tornadic cases revealed that forecasters’ use of PAR data provided a median tornado-warning lead time (TLT) of 20 min. This 20-min TLT exceeded by 6.5 and 9 min, respectively, participants’ forecast office and regions’ median spring season, low-end TLTs (2008–13). Furthermore, polygon-based probability of detection ranged from 0.75 to 1.0 and probability of false alarm for all four cases ranged from 0.0 to 0.5. Similar performance was observed regardless of prior warning experience. Use of a cognitive task analysis method called the recent case walk-through showed that this performance was due to forecasters’ use of rapid volumetric updates. Warning decisions were based upon the intensity, persistence, and important changes in features aloft that are precursors to tornadogenesis. Precursors that triggered forecasters’ decisions to warn occurred within one or two typical Weather Surveillance Radar-1988 Doppler (WSR-88D) scans, indicating PAR’s temporal sampling better matches the time scale at which these precursors evolve.
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Heinselman, Pamela L., Daphne S. LaDue, and Heather Lazrus. "Exploring Impacts of Rapid-Scan Radar Data on NWS Warning Decisions." Weather and Forecasting 27, no. 4 (August 1, 2012): 1031–44. http://dx.doi.org/10.1175/waf-d-11-00145.1.
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Abstract Rapid-scan weather radars, such as the S-band phased array radar at the National Weather Radar Testbed in Norman, Oklahoma, improve precision in the depiction of severe storm processes. To explore potential impacts of such data on forecaster warning decision making, 12 National Weather Service forecasters participated in a preliminary study with two control conditions: 1) when radar scan time was similar to volume coverage pattern 12 (4.5 min) and 2) when radar scan time was faster (43 s). Under these control conditions, forecasters were paired and worked a tropical tornadic supercell case. Their decision processes were observed and audio was recorded, interactions with data displays were video recorded, and the products were archived. A debriefing was conducted with each of the six teams independently and jointly, to ascertain the forecaster decision-making process. Analysis of these data revealed that teams examining the same data sometimes came to different conclusions about whether and when to warn. Six factors contributing toward these differences were identified: 1) experience, 2) conceptual models, 3) confidence, 4) tolerance of possibly missing a tornado occurrence, 5) perceived threats, and 6) software issues. The three 43-s teams issued six warnings: three verified, two did not verify, and one event was missed. Warning lead times were the following: tornado, 18.6 and 11.5 min, and severe, 6 min. The three tornado warnings issued by the three 4.5-min teams verified, though warning lead times were shorter: 4.6 and 0 min (two teams). In this case, use of rapid-scan data showed the potential to extend warning lead time and improve forecasters’ confidence, compared to standard operations.
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Rauhala, Jenni, and David M. Schultz. "Severe thunderstorm and tornado warnings in Europe." Atmospheric Research 93, no. 1-3 (July 2009): 369–80. http://dx.doi.org/10.1016/j.atmosres.2008.09.026.
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Cong, Zhen, Jianjun Luo, Daan Liang, and Ali Nejat. "Predictors for the Number of Warning Information Sources During Tornadoes." Disaster Medicine and Public Health Preparedness 11, no. 2 (June 23, 2016): 168–72. http://dx.doi.org/10.1017/dmp.2016.97.
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AbstractPeople may receive tornado warnings from multiple information sources, but little is known about factors that affect the number of warning information sources (WISs). This study examined predictors for the number of WISs with a telephone survey on randomly sampled residents in Tuscaloosa, Alabama, and Joplin, Missouri, approximately 1 year after both cities were struck by violent tornadoes (EF4 and EF5) in 2011. The survey included 1006 finished interviews and the working sample included 903 respondents. Poisson regression and Zero-Inflated Poisson regression showed that older age and having an emergency plan predicted more WISs in both cities. Education, marital status, and gender affected the possibilities of receiving warnings and the number of WISs either in Joplin or in Tuscaloosa. The findings suggest that social disparity affects the access to warnings not only with respect to the likelihood of receiving any warnings but also with respect to the number of WISs. In addition, historical and social contexts are important for examining predictors for the number of WISs. We recommend that the number of WISs should be regarded as an important measure to evaluate access to warnings in addition to the likelihood of receiving warnings. (Disaster Med Public Health Preparedness. 2017;11:168–172)
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Coffer, Brice E., Matthew D. Parker, Johannes M. L. Dahl, Louis J. Wicker, and Adam J. Clark. "Volatility of Tornadogenesis: An Ensemble of Simulated Nontornadic and Tornadic Supercells in VORTEX2 Environments." Monthly Weather Review 145, no. 11 (November 2017): 4605–25. http://dx.doi.org/10.1175/mwr-d-17-0152.1.
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Despite an increased understanding of the environments that favor tornado formation, a high false-alarm rate for tornado warnings still exists, suggesting that tornado formation could be a volatile process that is largely internal to each storm. To assess this, an ensemble of 30 supercell simulations was constructed based on small variations to the nontornadic and tornadic environmental profiles composited from the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2). All simulations produce distinct supercells despite occurring in similar environments. Both the tornadic and nontornadic ensemble members possess ample subtornadic surface vertical vorticity; the determinative factor is whether this vorticity can be converged and stretched by the low-level updraft. Each of the 15 members in the tornadic VORTEX2 ensemble produces a long-track, intense tornado. Although there are notable differences in the precipitation and near-surface buoyancy fields, each storm features strong dynamic lifting of surface air with vertical vorticity. This lifting is due to a steady low-level mesocyclone, which is linked to the ingestion of predominately streamwise environmental vorticity. In contrast, each nontornadic VORTEX2 simulation features a supercell with a disorganized low-level mesocyclone, due to crosswise vorticity in the lowest few hundred meters in the nontornadic environment. This generally leads to insufficient dynamic lifting and stretching to accomplish tornadogenesis. Even so, 40% of the nontornadic VORTEX2 ensemble members become weakly tornadic. This implies that chaotic within-storm details can still play a role and, occasionally, lead to marginally tornadic vortices in suboptimal storms.
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Nagele, Danielle E., and Joseph E. Trainor. "Geographic Specificity, Tornadoes, and Protective Action." Weather, Climate, and Society 4, no. 2 (April 1, 2012): 145–55. http://dx.doi.org/10.1175/wcas-d-11-00047.1.
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Abstract In 2007, the National Weather Service (NWS) began using storm-based warnings (SBWs) rather than countywide warnings. Some analysts have examined the effects of this change, but little empirical research has yet to focus on the public response. Using a random digit dialing sample and a computer-assisted telephone interviewing (CATI) system, data were collected that focused on protective action decision making in counties that were affected by a severe storm or tornado warning. Based on those data, the following paper examines the influence of these new storm-based warnings on protective action decision making by the public. While a significant relationship between being inside the warning polygon and taking protective action was not found, the authors were able to conclude that polygon size is an important factor. Given these mixed results, it is suggested that future work on storm-based warnings focus on the warnings’ dissemination and reception, as well as the optimization of the polygons themselves. It is suggested that the complexities associated with communicating with these risk areas complicate the dissemination process and create difficulties in the public understanding of the warning. The possible need for optimization is reinforced by the significance of the track proximity and polygon-sized variables. In addition, a smaller polygon resulted in protective action, in particular, sheltering. With regard to the preparedness and sociodemographic variables, the study’s results agreed with previous findings on the importance of a family emergency plan. Unlike earlier research this study did not find past experience or education level significant within the regression model and showed mixed results of gender.
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Bradford, Marlene. "Historical Roots of Modern Tornado Forecasts and Warnings." Weather and Forecasting 14, no. 4 (August 1999): 484–91. http://dx.doi.org/10.1175/1520-0434(1999)014<0484:hromtf>2.0.co;2.
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Martinaitis, Steven M. "Radar Observations of Tornado-Warned Convection Associated with Tropical Cyclones over Florida." Weather and Forecasting 32, no. 1 (January 5, 2017): 165–86. http://dx.doi.org/10.1175/waf-d-16-0105.1.
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Abstract Statistical evaluations of tornado warnings issued during recent tropical cyclone events yielded an above-average false alarm ratio. This study analyzed tornado-warned convection associated with Tropical Storms Debby (2012) and Andrea (2013) using superresolution and dual-polarization data from Weather Surveillance Radar-1988 Doppler radars located throughout the Florida peninsula to identify precursor characteristics and signatures that would distinguish tornadic events prior to tornadogenesis. A series of radar-based interrogation guidance at varying ranges from radar is presented to help facilitate the reduction of the tornado-warning false alarm ratio without compromising the probability of detection. For convection within 74.1 km from the nearest radar, low-level velocity characteristics include a rotational velocity ≥ 10.3 m s−1 (20 kt), shear across the rotation ≥ 0.010 s−1, and a contracting rotation diameter. The convection should also exhibit supercell reflectivity signatures and at least a mesocyclone velocity enhancement signature or horizontal separation of greater ZDR and KDP values. Guidance at a range from 74.1 to 129.6 km is similar except for not requiring the presence of a supercell reflectivity signature and the change of the rotational velocity guidance to ≥7.7 m s−1 (15 kt) at the 0.5°-elevation angle. Convection at a range beyond 129.6 km only requires a rotational velocity ≥ 7.7 m s−1 (15 kt) at the 0.5°-elevation angle. Evaluation of the radar interrogation guidance for tornadic events and tornado-warned convection for six tropical cyclones reduced the number of false alarm events by 28.9% and reduced the false alarm ratio from 0.740 to 0.669.
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Broomell, Stephen B., Gabrielle Wong-Parodi, Rebecca E. Morss, and Julie L. Demuth. "Do We Know Our Own Tornado Season? A Psychological Investigation of Perceived Tornado Likelihood in the Southeast United States." Weather, Climate, and Society 12, no. 4 (October 2020): 771–88. http://dx.doi.org/10.1175/wcas-d-20-0030.1.
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AbstractReducing fatalities from tornadoes in the southeastern United States requires considering multiple societal factors, including the risk perceptions that influence how people interpret tornado forecasts and warnings and make protective decisions. This study investigates perceptions of tornado risk in the southeastern United States, operationalized as judgments of tornado likelihood. While it is possible that residents of the Southeast could learn about tornado likelihood in their region from observing the local environment, cognitive-ecological theory from psychology suggests that such judgments of likelihood can be inaccurate, even if other aspects of local knowledge are accurate. This study analyzes data from a survey that elicited different groups’ judgments of tornado likelihood associated with different seasons, times of day, and storm system types. Results are presented from a representative sample of Southeastern residents and are compared with a sample of tornado experts (who have extensive knowledge about the likelihood of Southeastern tornadoes) and a representative sample of Great Plains residents. Overall, the analysis finds that many members of the Southeastern public deviate from the expert sample on tornado likelihood, especially for winter and overnight tornadoes. These deviations from expert opinion mimic the judgments of the Great Plains public. This study demonstrates how psychological theory and a decision science approach can be used to identify potential gaps in public knowledge about hazardous weather risks, and it reveals several such potential gaps. Further research is needed to understand the reasons for deviations between public and expert judgments, evaluate their effects on protective decision-making, and develop strategies to address them.
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Hoium, Debra K., Allen J. Riordan, John Monahan, and Kermit K. Keeter. "Severe Thunderstorm and Tornado Warnings at Raleigh, North Carolina." Bulletin of the American Meteorological Society 78, no. 11 (November 1997): 2559–75. http://dx.doi.org/10.1175/1520-0477(1997)078<2559:statwa>2.0.co;2.
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Kuster, Charles M., Pamela L. Heinselman, and Marcus Austin. "31 May 2013 El Reno Tornadoes: Advantages of Rapid-Scan Phased-Array Radar Data from a Warning Forecaster’s Perspective*." Weather and Forecasting 30, no. 4 (August 1, 2015): 933–56. http://dx.doi.org/10.1175/waf-d-14-00142.1.
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Abstract On 31 May 2013, a supercell produced a tornado rated as 3 on the enhanced Fujita scale (EF3) near El Reno, Oklahoma, which was sampled by the S-band phased-array radar (PAR) at the National Weather Radar Testbed in Norman, Oklahoma. Collaboration with the forecaster who issued tornado warnings for the El Reno supercell during real-time operations focused the analysis on critical radar signatures frequently assessed during warning operations. The wealth of real-world experience provided by the forecaster, along with the quantitative analysis, highlighted differences between rapid-scan PAR data and the Weather Surveillance Radar-1988 Doppler located near Oklahoma City, Oklahoma (KTLX), within the context of forecast challenges faced on 31 May 2013. The comparison revealed that the 70-s PAR data proved most advantageous to the forecaster’s situational awareness in instances of rapid storm organization, sudden mesocyclone intensification, and abrupt, short-term changes in tornado motion. Situations where PAR data were most advantageous in the depiction of storm-scale processes included 1) rapid variations in mesocyclone intensity and associated changes in inflow magnitude; 2) imminent radar-indicated development of the short-lived (EF0) Calumet, Oklahoma, and long-lived (EF3) El Reno tornadoes; and 3) precise location and motion of the tornado circulation. As a result, it is surmised that rapid-scan volumetric radar data in cases like this would augment a forecaster’s ability to observe rapidly evolving storm features and deliver timely, life-saving information to the general public.
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Shmerlin, B. Ya, M. A. Novitskii, and O. V. Kalmikova. "ON A NEW APPROACH TO FORECASTING TORNADO-DANGEROUS SITUATIONS AND OTHER DANGEROUS CONVECTIVE PHENOMENA." XXII workshop of the Council of nonlinear dynamics of the Russian Academy of Sciences 47, no. 1 (April 30, 2019): 135–37. http://dx.doi.org/10.29006/1564-2291.jor-2019.47(1).42.
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In many studies indices of convective instability (hereinafter simply indices) are used to analyze and predict tornado-dangerous situations. For calculating the meteorological fields from which indices were subsequently calculated, the WRF-ARW version 3.4 was used – the non-hydrostatic, regional weather forecasting system. In the works (Novitskii et al, 2016; 2018) as an example of the calculation of 10 tornadoes that occurred at different times in the European territory of the Russian Federation, we show that the most informative from the point of view of forecasting tornado-dangerous situations and providing a minimum number of false warnings is the STP (significant tornado parameter) index. The characteristic time, during which STP index exceeds threshold value, is within the order of an hour, the size of the regions of localization of the values of the indices above the threshold is within the order of several tens kilometers. We proposed along with the STP index to involve the vertical velocity field, calculated in the WRF model, in the analysis and forecast of tornado-dangerous situations. We show that the value of the STP index above the threshold leads within the WRF model to the formation of a localized intense convective cell in the vertical velocity field in the vicinity of the maximum value of the index and at the moment of reaching this value. The possibility of using the STP index to predict tornado-dangerous situations with a lead time of up to three days with an accuracy of 150 km in space and several hours in time is demonstrated. A new approach to short-term forecasting of tornadoes is proposed. It is based on calculating the fields that are visible on the radar screen, using the WRF model forecast. Such fields are the fields of maximum radar reflectivity, upper cloud boundary and integral vertical water content. The comparison of the prognostic fields with the real fields that the radar sees allows us to specify a real convective system at the time of its formation in which the STP index will subsequently reach a threshold value and a tornado will appear. This can enlarge a lead time of tornado warnings to several hours, which currently averages 13 minutes. The approach can also be used for forecasting other dangerous convective phenomena, as well as in any other forecast models for current forecast correction by using incoming radar (satellite) information.
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Hatzis, Joshua J., Jennifer Koch, and Harold E. Brooks. "Spatiotemporal Analysis of Near-Miss Violent Tornadoes in the United States." Weather, Climate, and Society 11, no. 1 (December 11, 2018): 159–82. http://dx.doi.org/10.1175/wcas-d-18-0046.1.
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Abstract In the hazards literature, a near-miss is defined as an event that had a nontrivial probability of causing loss of life or property but did not due to chance. Frequent near-misses can desensitize the public to tornado risk and reduce responses to warnings. Violent tornadoes rarely hit densely populated areas, but when they do they can cause substantial loss of life. It is unknown how frequently violent tornadoes narrowly miss a populated area. To address this question, this study looks at the spatial distribution of possible exposures of people to violent tornadoes in the United States. We collected and replicated tornado footprints for all reported U.S. violent tornadoes between 1995 and 2016, across a uniform circular grid, with a radius of 40 km and a resolution of 0.5 km, surrounding the centroid of the original footprint. We then estimated the number of people exposed to each tornado footprint using proportional allocation. We found that violent tornadoes tended to touch down in less populated areas with only 33.1% potentially impacting 5000 persons or more. Hits and near-misses were most common in the Southern Plains and Southeast United States with the highest risk in central Oklahoma and northern Alabama. Knowledge about the location of frequent near-misses can help emergency managers and risk communicators target communities that might be more vulnerable, due to an underestimation of tornado risk, for educational campaigns. By increasing educational efforts in these high-risk areas, it might be possible to improve local knowledge and reduce casualties when violent tornadoes do hit.
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MATSUI, Kyoko, and Makoto SHIMAMURA. "OPTIMAL OPERATION OF TORNADO WARNINGS BASED ON COST-LOSS MODEL." Journal of Japan Society of Civil Engineers, Ser. D3 (Infrastructure Planning and Management) 71, no. 5 (2015): I_111—I_119. http://dx.doi.org/10.2208/jscejipm.71.i_111.
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Dunn, Lawrence B. "Two Examples of Operational Tornado Warnings Using Doppler Radar Data." Bulletin of the American Meteorological Society 71, no. 2 (February 1990): 145–53. http://dx.doi.org/10.1175/1520-0477(1990)071<0145:teootw>2.0.co;2.
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