The effect of providing probabilistic information about a tornado threat on people’s protective actions

National Weather Service issues deterministic warnings in a tornado event. An alternative system is being researched at National Severe Storms Laboratory to issue Probabilistic Hazard Information (PHI). This study investigated how providing the uncertainty information about the tornado occurrence through PHI changes people’s protective actions. In an experiment, visual displays of the probabilistic information and deterministic warnings were presented to fifty participants to report their expected protective actions in different scenarios. It was found that the percentage of people who expected to immediately take shelter right after receiving the weather information increased exponentially as their proximity to the threat decreased. When there was more chance that the information about occurrence of a particular tornado was false rather than true, in scenarios that the likelihood of the threat occurrence was less than 50%, providing it through PHI lowered the percentage of people who immediately took shelter. The ordinal logistic regression models showed that the probability of taking protective actions significantly changes by providing the uncertainty information when people have less than 20 min lead time before getting impacted by the threat. When the lead time is less than 10 min, the probability of immediately taking shelter increases to 94 from 71%, and when the lead time is more than 10 but less than 20 min, that probability increases from 53 to 70%, if they are provided with the probabilistic information. Presenting the likelihood of any tornado formation in the area did not have significant effect on the people’s protective actions.     

Design and adoption of household tornado shelters for Bangladesh

Death tolls from tornadoes in Bangladesh are the highest in the world due to lack of storm warnings, poor communication, weak housing, and lack of shelters from strong winds in tornadoes and nor’westers. Based on surveys of housing types and designs in the Tangail district, a household tornado shelter is proposed to be placed in the elevated storage platform that is common in houses. The shelter is 2 m tall, 1.2 m wide, and 2–4 m long (4.8–9.6 m³ in volume) with the floor of the shelter placed one meter below the floor of the house. Walls are 7–10 cm thick and made of concrete or an earthen wall stabilized with cement or strengthened with bamboo or bricks. A survey of 200 residents of the region found nearly universal acceptance for the shelter design, and residents were eager for installation of the household shelters. The shelter cost is 2,500–10,000 taka (US50 to50 to 200) depending on local material and labor costs but residents were willing to pay an average of only 1,071 taka (US$21) toward the cost of the shelter. Families with greater income and land holdings and families in villages with recent tornado experience were willing to spend more for a shelter. A pilot project to install household tornado shelters in selected villages and monitor their use, along with continued efforts to issue storm warnings, communicate the warnings, and improve education about storm hazards, will prevent injuries and save lives in Bangladesh and reduce the descent into poverty that results from losses in severe local storms.     

Tornado shelter-seeking behavior and tornado shelter options among mobile home residents in the United States

Residents of 401 mobile homes in Georgia, Mississippi, Illinois, and Oklahoma were surveyed after they heard a tornado warning. Most residents (69%) did not seek shelter during the warning. Half of those who sought shelter went to the frame house of a friend, neighbor, or relative, and 25% of those sought shelter in a basement or underground shelter. Some of the places where residents sought shelter were of dubious quality, such as their own mobile home, another mobile home, or in an out-building. Twenty-one percent of mobile home residents believed that they had a basement or underground shelter available as shelter during a tornado warning, and about half of those said they would drive to the shelter. Residents said they would drive if the shelter was more than 200 m away. Fifteen percent actually had a basement or underground shelter suitable as shelter within 200 m of their mobile home, but only 43% of the residents would use those shelters. The most common reason cited for not using the shelters was that they did not know the people who lived there. Likewise, a frame house or other sturdy building was within 200 m of 58% of the mobile homes, but only 35% of the residents stated they would use those houses for shelter. Thirty-one percent of mobile home residents had a ditch that was at least 0.5 m deep within 200 m of the mobile home. However, 44% of these ditches had utility lines overhead, 23% had water in them, and 20% had trees overhead. The limited tornado shelter options among mobile home residents in the United States needs to be incorporated into safety instructions so that residents without nearby shelter are allowed to drive to safer shelter.     

Opportunities and challenges in rebuilding tornado-impacted Greensburg,Kansas as “stronger,better, and greener”

A May 2007 tornado destroyed 95% of aging, declining Greensburg, Kansas. The city took the opportunity to build back “stronger, better, and greener,” enforcing upgraded codes, requiring city-owned buildings to meet LEED Platinum level standards, and recommending energy-efficiency housing in a new Sustainable Comprehensive Plan. Using information collected from surveys of Greensburg tornado survivors, interviews, and publications, we examined the housing-related recovery, including the emergency provision of temporary shelter and rebuilding permanently. Although temporary shelter kept residents nearby for rebuilding, given the gap between insurance policy limits on the aging housing stock and rebuilding costs, housing affordability is a critical issue in Greensburg’s recovery. Local, state, and federal support have made construction of municipal buildings at LEED Platinum level and some affordable and green housing projects possible. However, far greater public and private sector funding for affordable workforce housing, in conjunction with broader economic and job development, is needed.     

Simulation of tornado over Orissa (India) on March 31, 2009, using WRF–NMM model

A severe thunderstorm produced a tornado (F3 on the Fujita-Pearson scale), which affected Rajkanika block of Kendrapara district of Orissa in the afternoon of March 31, 2009. The devastation caused by the tornado consumed 15 lives and left several injured with huge loss of property. The meteorological conditions that led to this tornado have been analyzed. An attempt is also made to simulate this rare event using Non-hydrostatic Mesoscale Model (NMM) core of the Weather Research and Forecasting (WRF) system with a spatial resolution of 4 km for a period of 24 h, starting at 0000 UTC of March 31, 2009. The atmospheric settings resulted from synoptic, surface, upper air, satellite and radar echo studies were favorable for the occurrence of a severe thunderstorm activity over Rajkanika. The model-simulated meteorological parameters are consistent with each other, and all are in good agreement with the observation in terms of the region of occurrence of the intense convective activity. The model has well captured the vertical motion. The core of the strongest winds is shown to be very close to the site of actual occurrence of the event. The wind speed is not in good agreement with the observation as it has shown the strongest wind of only 20 ms⁻¹, against the estimated wind speed of 70 ms⁻¹. The spatial distributions as well as intensity of rainfall rates are in good agreement with the observation as model simulated 35.4 mm against the observed rainfall of 41 mm over Chandbali. The results of these analyses demonstrated the capability of high-resolution WRF–NMM model in simulation of severe thunderstorm events.     

The good,the bad,and the ugly facts of tornado survival

Anytime that tornadoes interface with people, the results are often grim. The varied characteristics of tornado windfields and the diverse techniques of home construction complicate the expected outcomes of such interactions. Since it is now known that tornadoes do not produce unfathomable winds, engineers have developed techniques for increasing a home’s tornado resistance; thus, increasing the odds of survival of the inhabitants. Even considering these advances, tornadoes still wreak havoc and cause much causality every year. The story of tornado survival is partly chance, partly knowledge, and partly science. This essay utilizes analogies between a popular motion picture and the state of the art of tornado-resistant construction to illustrate the good, the bad, and the ugly facts of tornado survival. First examined are the positive aspects of tornado probability. The odds of experiencing a tornado are so low that massive expenditures are not necessarily cost effective. Next, various techniques of tornado-resistant construction practices are included for new and existing structures. Introduction of equations for predicting debris penetration are compared with various building techniques to describe the viability of tornado protection. The negative aspect of tornado/structure interfaces describes the fact that despite contemporary construction and prevention exercise, the unpredictability of the tornado windfield causes tremendous damage and loss of life. The final section examines the interface between tornadoes and mobile homes. This proves very ugly in every aspect of the word. Statistics and equations confirm the inherent dangers of such an interaction. Also, described is a novel approach to the design of a portable tornado shelter.     

Exploring probable reasons for record fatalities: the case of 2011 Joplin, Missouri, Tornado

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 characteristics 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.     

US tornado fatalities in motor vehicles (1991–2015)

Motor vehicles historically have been dangerous locations to shelter in during tornado events. Throughout the twentieth century, motor vehicle design has become safer while tornado forecasting has become better understood. Despite such advances, tornado fatalities in motor vehicles still occur today, and some events periodically result in high numbers of deaths (e.g., ten motor vehicle occupants were killed by a single tornado in Garland, Texas, in 2015). We seek to examine all US tornado-induced motor vehicle fatalities documented between 1991 and 2015. Our findings indicate that motor vehicle fatalities have not significantly changed during this study period. We attribute annual fatality totals to persons lacking awareness of impending dangers coupled with numbers of significant tornado events for a given year. We find most fatalities result when vehicles are lofted or passengers are ejected, and this most typically occurs at the EF3–EF5 intensity thresholds. Fatalities that occur at weaker tornado winds (EF0–EF2) are most often attributed to collapsing debris (mostly trees) on vehicles. Spatially, motor vehicle fatalities are greatest in the Deep South and southern Great Plains regions where overall tornado and nighttime tornado frequencies are greatest. Some of the largest motor vehicle fatality events have resulted from tornadoes not being distinctly visible to motorists; such events have been characterized by tornadoes occurring at night or by tornadoes not appearing as “classic funnels.”     

Thinking outside the polygon: a study of tornado warning perception outside of warning polygon bounds

When the National Weather Service (NWS) issues a tornado warning, the alert is rapidly and widely disseminated to individuals in the general area of the warning. Historically, the assumption has been that a false-negative warning perception (i.e., when someone located within a warning polygon does not believe they have received a tornado warning) carries a higher cost than a false-positive warning perception (i.e., when someone located outside the warning area believes they have received a warning). While many studies investigate tornado warning false alarms (i.e., when the NWS issues a tornado warning, but a tornado does not actually occur), less work focuses on studying individuals outside of the warning polygon bounds who believe they received a warning (i.e., false-positive perceptions). This work attempts to quantify the occurrence of false-positive perceptions and possible factors associated with the rate of occurrence. Following two separate storm events, Oklahomans were asked whether they perceived a tornado warning. Their geolocated responses were then compared to issued warning polygons. Individuals closer to tornado warnings or within a different type of warning (e.g., a severe thunderstorm warning) are more likely to report a false-positive perception than those farther away or outside of other hazard warnings. Further work is needed to understand the rate of false-positive perceptions across different hazards and how this may influence warning response and trust in the National Weather Service.

     

Hindcasting community-level building damage for the 2011 Joplin EF5 tornado

Resiliency of communities prone to natural hazards can be enhanced through the use of risk-informed decision-making tools. These tools can provide community decision makers key information, thereby providing them the ability to consider an array of mitigation and/or recovery strategies. The Center for Risk-Based Community Resilience Planning, headquartered at Colorado State University in Fort Collins, Colorado, developed an Interdependent Networked Community Resilience (IN-CORE) computational environment. The purpose of developing this computational environment is to build a decision-support system, for professional risk planners and emergency responders, but even more focused on allowing researchers to explore community resilience science. The eventual goal was being to integrate a broad range of scientific, engineering and observational data to produce a detailed assessment of the potential impact of natural and man-made hazards for risk mitigation, planning and recovery purposes. The developing computational environment will be capable of simulating the effects from different natural hazards on the physical and socioeconomic sectors of a community, accounting for interdependencies between the sectors. However, in order to validate this computational tool, hindcasting of a real event was deemed necessary. Therefore, in this study, the community of Joplin, Missouri in the USA, which was hit by an EF-5 tornado on May 22, 2011, is modeled in the IN-CORE v1.0 computational environment. An explanation of the algorithm used within IN-CORE is also provided. This tornado was the costliest and deadliest single tornado in the USA in the last half century. Using IN-CORE, by uploading a detailed topological dataset of the community and the estimated tornado path combined with recently developed physics-based tornado fragilities, the damage caused by the tornado to all buildings in the city of Joplin was estimated. The results were compared with the damage reported from field studies following the event. This damage assessment was done using three hypothetical idealized tornado scenarios, and results show very good correlation with observed damage which will provide useful information to decision makers for community resilience planning.     

Implications of the 2011 Tuscaloosa EF4 tornado for shelter and refuge decisions

This research provides an overview and discussion of language used in tornado safety recommendations along with development of a rubric for scaled tornado safety recommendations. Residents living in affected areas and those temporarily housed at relief stations were surveyed to collect information on their experiences during a 2-week period following the April 27, 2011 Tuscaloosa, Alabama EF4 tornado. Respondents were asked about their refuge plans during the storm and about any future changes to those plans. A specific focus of this research evaluated the adequacy of each respondent’s plan. Each refuge plan was compared using a tornado refuge rubric developed through the use of enhanced Fujita (EF) scale degree of damage ratings for available damage indicators. There was a significant difference in the counts of refuge adequacy for Tuscaloosa residents when holding the locations during the April 27 tornado constant and comparing adequacy ratings for weak (EF0–EF1), strong (EF2–EF3), and violent (EF4–EF5) tornadoes. There was also a significant difference when comparing the future tornado refuge plans of those same participants to the adequacy ratings for weak, strong, and violent tornadoes. This research introduces renewed discussion on proper refuge and shelter alternatives for days when violent tornadoes are forecasted.     

Tornado hazards on June 23 in Jiangsu Province,China: preliminary investigation and analysis

This paper reported a tornado hazard happened on June 23, 2016, in Yancheng city, Jiangsu Province. The moving footprint of this huge tornado was from west to east. Shuoji, Chenliang, Goudun, Banhu, Xingou, Wutan towns in Funing district and Sheyang town in Sheyang district were severely hit by this tornado. This tornado along with rainstorm and hailstorm had claimed 99 lives and caused more than 3800 flats to collapse as well as damaged 48 high-voltage circuits. As the cold air from northwest met the subtropical high pressure system that forms over relatively cool water bodies (i.e., Indian and Pacific Oceans), such a powerful meteorological phenomenon was initiated. The strong connective airflow intensified the development of this tornado. Based on the preliminary investigation and analysis of this tornado, cost-effective timber structures with adequate anchorage of the framing to foundations and adequate connection between walls and roofs may be recommended to ensure occupants safety and reduce potential damage in these extreme wind events. Additionally, it is suggested to utilize early warning system along with geographical information system (GIS), Global Positioning System (GPS), and remote sensing (RS) (3S) to monitor and precast the occurrence of rainfall, hailstorm, and tornado hazards in future.

     

An Australian pyro-tornadogenesis event

On 18 January 2003, fires had a devastating impact on Australia’s capital, Canberra. A series of reviews and scientific studies have examined the events of that day and indicate that the worst impacts were due to a series of violent pyro-convective events and resultant pyro-cumulonmibi. These coupled fire–atmosphere events are much more energetic than normal fires. In one instance, an intense pyro-convective cell developed a tornado. We demonstrate that this was indeed a tornado, the first confirmed pyro-tornadogenesis in Australia, and not a fire whirl. Here, we discuss aspects of the formation, evolution and decay of the tornado, which was estimated to have been of at least F2 intensity, highlighting a process that can significantly increase the damage of a wildfire event.     

A qualitative study of mobile home resident perspectives on tornadoes and tornado protective actions in South Carolina,USA

Occupants of mobile or manufactured homes in the United States of America (USA) are highly exposed and susceptible to injury or death from tornado hazards. This problem is most pronounced in the southern and eastern USA, where tornadoes are frequent and mobile homes comprise upwards of 15 % of the housing stock. Recognizing this vulnerability, emergency management entities and the USA National Weather Service often recommend that mobile home residents evacuate to a nearby sturdy building or a specially-built tornado shelter when tornadoes threaten their communities. Previous research suggests, however, that only 30 % of residents follow this recommendation. In this research I aim to provide insight as to why many mobile home residents seldom undertake the suggested course of action for tornadoes. Using excerpts from twenty semi-structured interviews conducted during 2013 in South Carolina, I show that some individuals understand physical characteristics of tornadoes very differently than experts do. In addition, mobile home residents may also hold views that differ from experts about the ability of their homes to withstand tornadic winds and debris. Even if mobile home occupants pay close attention to thunderstorm hazards and might be willing to evacuate, they may prioritize protective actions for lightning or flash flooding over those recommended for tornadoes. Finally, the interviews reveal that there is much confusion over where to go, when to leave, and which route to take to arrive safely at a sheltering place for tornado hazards. I discuss some of the potential ramifications of the findings for theory and practice and suggest how future research might build on this work.     

Meteorological analysis of the tornado in Ciudad Acuña,Coahuila State,Mexico, on May 25, 2015

Extreme meteorological conditions favor the development of severe storms and tornadoes that may have largely impacts on the population despite its relatively short life. Tornadic severe storms have been documented around the World. In Mexico (MEX), the study of the occurrence of tornadoes and severe storms is relatively new. In this research, we have selected an event of severe tornadic storm in Ciudad Acuña, Mexico. The storm was driven by a frontal system moving southward from USA converging with a warmer moist air flux from the Gulf of Mexico. The tornado strikes on the Northeast of Mexico, in Coahuila State, on May 25, 2015. Imagery of infrared channel from GOES 13 satellite and the presence of a hook echo in radar data of May 25, 2015, indicate a supercell structure. The maximum values of radial velocity were about ?20 and 15 m s^?1. In this study, the WRF model was used in order to simulate the mesoscale meteorological conditions of the tornado. Model simulations capture atmospheric features observed in Doppler radar. The simulated storm-relative helicity values were between 400 and 500 m² s^?2. The simulated convective available potential energy values were of 3000 J kg^?1. These values were higher than values for convective storms, located over the region of Ciudad Acuña in Mexico and Del Rio in USA. The supercell was a result of high humidity and temperature gradients, conditioned by frontal activity and moisture flux intensifications from the Gulf of Mexico.

     

Building damage assessment after the <Emphasis Type="Italic">Riviera del Brenta</Emphasis> tornado,northeast Italy

A tornado with severe intensity hit the municipalities of Pianiga, Dolo and Mira close to Venice, northeast Italy, causing damages on a wide number of residential and industrial buildings and destroying some historical villas. In this study, the authors show the results of the damage assessment survey performed in the first days after the occurrence of the extreme event. Limited literature deals with damage assessment of European building types due to wind actions, and the available one does not consider building vulnerability as key factor in the structural response of existing structures subject to tornado hazard. In this paper, structural damages surveyed in reinforced concrete frame structures and masonry buildings, representative of common Italian building types, are critically discussed. Additionally, this work provides a database of past tornado events in northeast Italy, evidencing how the analyzed area has been found to be quite prone to tornado hazard.     

Evacuation behaviour of households and drivers during a tornado

With increasing concerns over the possibility of tornadoes in highly populated areas in Canada, emergency managers are looking into ways to mitigate the impacts of tornadoes. Given that tornadoes can cause enormous destruction, early warnings and proper evacuation actions are critically important in helping save lives. In this paper, a survey was conducted to analyse the evacuation behaviour of households and drivers during a hypothetical tornado warning situation in the city of Calgary, Alberta. Nearly 500 Calgarians took part in the online survey and provided information on how they would respond to tornado warnings after receiving them. This paper presents the results of the survey. Using probit models, the factors influencing these evacuation decisions are identified and discussed in detail. The results of the household evacuation model show the importance of improving awareness about the safest locations during a tornado. It further highlights the need for targeting the population under the age of 30, who are more likely to take unsafe evacuation actions. The model for evacuation of drivers shows that several factors, such as knowing the difference between a watch and a warning, awareness of safe cover, receipt of warnings through natural environmental cues and the level of education, trigger evacuation actions in avoiding a tornado threat.     

Spatiotemporal analysis of tornado exposure in five US metropolitan areas

Weather-related disasters and affiliated losses in the USA have amplified over time. However, prior research using normalization schemes on damage tallies suggests that weather hazard losses are not necessarily rising when inflation, changes in wealth, and growth in population are accounted. This study evaluates the latter factor, assessing if population changes and a sprawling development mode have led to increasing potential for tornado disasters in the USA. Specifically, this research shows where and how quickly tornado exposure is growing by appraising spatiotemporal trends in gridded population and housing unit data for five metropolitan statistical areas (MSAs). The macroscale risk to tornadoes is represented by tornado day climatology and is related to the exposure of the five MSAs, which include Atlanta, GA; Chicago, IL; Dallas/Fort Worth, TX; Oklahoma City, OK; and St. Louis, MO. Supplementing the macroscale investigation, an observationally derived, hypothetical violent tornado track is transposed on various development types in each MSA to determine the microscale changes in human and built-environment exposure. Results demonstrate increased exposure in all MSAs at both the macro- and microscale. Of the five MSAs studied, Dallas, TX, had the greatest potential for a tornado disaster due to the higher risk for tornado occurrence comingling with the amount of MSA exposure. These results reveal further that amplifying exposure is a major impetus behind intensifying severe weather impacts and losses.     

http://www.sciencedirect.com/science/article/pii/S1674987115000869

The predictability of dangerous atmospheric phenomena such as tornado outbreaks has generally been limited to a week or less. However, recent work has demonstrated the importance of the Rossby wavetrain phasing over the United States in establishing outbreak-favorable environments. The predictability of Rossby wavetrain phasing is strongly related to numerous climate-scale interannual variability indices, which are predictable many months in advance. To formalize the relationship between interannual variability indices and seasonal tornado outbreak frequency, indices derived from monthly mean Northern Hemisphere 500-hPa and 1000-hPa geopotential height fields and Ni?o 3.4 indices for ENSO phase were compared to annual tornado outbreak seasonal frequencies. Statistical models predicting seasonal outbreak frequency were established using linear(stepwise multivariate linear regressione SMLR) and nonlinear(support vector regressione SVR) statistical modeling techniques.The stepwise methodology revealed predictors that are important in establishing outbreak-favorable environments at long lead times. Additionally, the results of the statistical modeling revealed that the nonlinear SVR technique reduced root mean square errors produced by the control SMLR technique by 28% and provided more consistent forecasts. A preliminary physical analysis revealed that years with high outbreak frequencies were associated with the presence of 500-mb troughs over the central and western US during the peak of outbreak season, while lower frequencies were consistent with ridging over the US or northwest flow over the Plains. These patterns support the results of the statistical modeling, which demonstrate the utility of geopotential height variability as a predictability measure of outbreak frequency.     

Characteristics of high impact weather and meteorological disaster in Shanghai,China

This paper discusses the characteristics of high-impact weather events based on available data during 1960–2009, including the frequency and extreme value of rainstorm, typhoon, thunderstorm, strong wind, tornado, fog, haze and hot days in Shanghai, China. The frequency and spatial distribution of meteorological disasters and their impacts on both human and property during 1984–2009 are also discussed. Examination of the frequency indicates a decreasing trend in the occurrence of typhoon, thunderstorm, strong wind, tornado and fog, and an increasing trend in the occurrence of rainstorm, haze and hot days. The number of casualties caused by meteorological disasters appears to show a slight decreasing trend while the value of direct economic loss is increasing slightly during 1984–2009, and the number of collapsed or damaged buildings and the area of affected crops have no significant trend in Shanghai. These results can be attributed to the great efforts for prevention and mitigation of meteorological disasters made by Shanghai government in recent 60 years. With global climate change, urbanization and rapid economic development, Shanghai has become more vulnerable to high-impact weather and meteorological disaster, especially precipitation extreme, summer high temperature, haze and typhoon, so more strategies of mitigation and/or adaptation of natural disasters are quite useful and necessary for local government and the public in the future.