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## Über dieses Buch

For almost a decade, economists Kevin M. Simmons and Daniel Sutter have been studying the economic effects and social consequences of the approximately 1,200 tornadoes that touch down across the United States annually. During this time, they have compiled information from sources such as NOAA and the U.S. Census Bureau to examine the casualties caused by tornadoes and to evaluate the National Weather Service (NWS)’s efforts to reduce these casualties. Their unique database has enabled this fascinating and game-changing study for meteorologists, social scientists, emergency managers, and everyone studying severe weather, policy, disaster management, or applied economics.

## Inhaltsverzeichnis

### 1. What We Can Learn from Societal Impacts Analysis

Abstract
What does supply and demand teach us about whether rotating wall clouds will spin out a tornado? Nothing, really. Can we use the stock market to understand why tornadoes can be so capricious, flattening one house and leaving the one next door untouched? Well, no. So why would a couple of economists who have never even seen a tornado except on TV, and who know nothing about cloud dynamics, write a book about tornadoes? And why would anyone want to read it?
Kevin M. Simmons, Daniel Sutter

Abstract
Tornado climatology refers to the frequency of tornadoes. Climatology is not social science, so it may seem odd for economists to begin a book on the economic and societal impacts of tornadoes with climatology. But many of the decisions people can make to reduce their vulnerability to tornadoes depend on an understanding of the likelihood of tornadoes, or climatology. Consider the following:
• Manufactured housing exhibits vulnerability to tornadoes, which the data will validate. Yet manufactured housing represents an affordable and increasingly comfortable housing option for many Americans (Beamish et al. 2001). How is a family concerned about tornado risk to decide whether to live in a mobile home? Are residents of tornado-prone states who nonetheless choose to live in a manufactured home simply ignoring or failing to perceive and appreciate weather risk, or balancing other important life goals against safety?
• Wind engineers have developed new shelters capable of protecting against even the most powerful tornadoes. The Federal Emergency Management Agency (FEMA) issued performance standards for new tornado shelters in 1998 and included safe rooms in its (now-abandoned) National Mitigation Strategy. Tornado shelters and safe rooms are not cheap, and their benefits are tied to the risk of tornadoes. Are shelters worth the cost? An informed decision about shelter purchase requires data on tornado risk and how this risk varies across the nation.
• The nation also invests in tornado research and technology, with the ultimate goal of helping the National Weather Service (NWS) forecast and warn for tornadoes. For example, in the 1990s, the United States invested $1.2 billion on a nationwide network of Doppler weather radars (the WSR-88D, or NEXRAD network). One of the expected benefits of Doppler radars was improved tornado warnings. In 2009, NOAA undertook a research study on tornadoes called VORTEX II (Verification of the Origins of Rotation in Tornadoes Experiment; see page 3). At a cost of$10 million, the project equipped 40 vehicles to intercept and observe the entire life cycle of a tornadic thunderstorm. Ultimately, the nation’s return on these investments depends on the rate of tornado activity. The greater the threat, the greater the number of lives that can be saved by investments in research and technology to reduce the lethality of tornadoes.
Kevin M. Simmons, Daniel Sutter

Abstract
The National Weather Service (NWS) is charged with protecting lives and property from dangerous weather. Tornadoes are nature’s most violent local storms, capable of flattening entire towns, so we will focus first on casualties. An examination of the determinants of fatalities and injuries provides value for two reasons. First, assessment of NWS efforts to reduce the lethality of tornadoes—issuing tornado warnings, improving the quality of warnings, and providing public education—requires analysis of the determinants of casualties. Consider the 1990s installation by the NWS of the NEXRAD network of Doppler weather radars (WSR-88D), at a cost of over $1 billion. The radars were expected to yield a significant societal benefit: improved tornado warnings, and a consequent reduction in casualties. Has the NEXRAD network delivered on this promise, and if so, how many fatalities have been prevented? A detailed analysis is required, because Doppler radar is just one of many factors affecting tornado casualties. Failure to control for other factors may leave us unable to identify the impact of the NWS efforts on casualties. Kevin M. Simmons, Daniel Sutter ### 4. Tornado Warnings: How Doppler Radar, False Alarms, and Tornado Watches Affect Casualties Abstract The National Weather Service (NWS) began issuing tornado warnings in 1953. Tornado warnings represent the core element of the nation’s efforts to reduce tornado casualties. In addition to warnings, the Storm Prediction Center (SPC) issues tornado watches, and more recently began issuing convective outlooks. Watches alert residents that conditions are favorable for the development of tornadoes, while a warning means that a tornado either has been spotted or has been indicated on radar. The accuracy of tornado warnings has increased over the decades, and with the advent of Doppler weather radar, warnings can now generally be issued before a tornado actually touches down. In 2004, the probability of detection (or the proportion of tornadoes warned for) was .69, while the average lead time on tornado warnings was almost 13 minutes. Kevin M. Simmons, Daniel Sutter ### 5. Sheltering from the Storm: Evaluating Tornado Shelters as a Mitigation Investment Abstract On May 27, 1997, an F5 tornado struck the town of Jarrell, Texas, near Austin. The slow-moving tornado devastated an entire subdivision, wiping homes clean off their foundations. The casualty figures, 27 dead and 12 injured, indicate this tornado’s deadly power: More than two out of every three casualties were deaths. Tornadoes generally injure more persons than they kill: Since 1950, tornadoes have injured 81,000 and killed 4,900, or about 16 injuries per fatality. A tornado with more fatalities than injures is rare, and the difference of 15 more fatalities than injuries in the Jarrell tornado is the largest difference in any tornado since 1900. There was almost no escape for the unfortunate residents caught in the path of this tornado. Kevin M. Simmons, Daniel Sutter ### 6. Property Damage and Community Impacts of Tornadoes Abstract Research has not examined property damage from tornadoes as extensively as casualties. Several factors are likely in play here. First, the destructive power of tornadoes poses such a threat to life and limb that it is only natural for the main focus to be on casualties. In addition, with winds that can exceed 200 miles per hour and the added force of tornado suction vortices, property damage is seemingly impossible to avoid when a tornado hits. Although a part of a home could be hardened into a safe room capable of surviving an F5 tornado, the construction of homes that are impervious to tornado damage is cost-prohibitive, and building codes do not include wind-load designs for tornadoes. The NWS has instead directed its efforts toward watches and warnings that can potentially save lives. Furthermore, tornadoes simply do not pose the potential for catastrophic losses that affect the functioning of insurance markets and raise homeowners’ insurance rates. Tornado events resulting in insured losses in excess of$1 billion (which can include several tornadoes in a large outbreak) are becoming more frequent, but the potential for a $50 billion or$100 billion loss seemingly does not exist. And finally, the available data on property losses suffer from some limitations, which limits the ability of researchers to discern patterns in the losses.
Kevin M. Simmons, Daniel Sutter

### 7. Going Forward: Using Societal Impacts Research to Reduce Tornado Risk

Abstract
In this book we have examined how tornadoes produce fatalities and injuries, how tornado warnings provided by the NWS affect casualties, how impregnable shelters can be built to prevent casualties, and examined patterns in property damage. We conclude in this chapter by bringing together the pieces of our analysis to estimate the overall societal impact of tornadoes and to examine how NWS warnings have affected and continue to affect this impact. We then offer some suggestions based on the vulnerabilities we have identified to reduce tornado-related casualties in the future. Normally, science proceeds by its own internal logic, with discoveries producing new puzzles but also pointing the way forward. Societal impacts research enters as an addendum, to try to determine the value to society of the next question that the scientific process will answer. Here we offer suggestions based on societal impacts for future directions in research. We conclude by considering whether the United States is approaching the optimal number of tornado fatalities that can be expected, and offering some lessons from our study for research on the societal impacts of weather generally.
Kevin M. Simmons, Daniel Sutter

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