Kevin M. Simmons

WSR-88D Radar, Tornado Warnings, and Tornado Casualties

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.

False Alarms, Tornado Warnings, and Tornado Casualties

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 inju...

Tornado Warnings, Lead Times, and Tornado Casualties: An Empirical Investigation

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.

Normalized tornado damage in the United States: 1950-2011

In 2011, thunderstorms in the United States resulted in 550 deaths from tornadoes and more than

The 2011 Tornadoes and the Future of Tornado Research

28 billion in property damage, according to data from the US National Oceanic and Atmospheric Administration, with the vast majority of economic losses resulting from tornadoes. This article normalizes U.S. tornado damage from 1950 to 2011, using several methods. A normalization provides an estimate of the damage that would occur if past events occurred under a common base years societal conditions. We normalize for changes in inflation and wealth at the national level and changes in population, income and housing units at the county level. Under several methods, there has been a sharp decline in tornado damage. This decline corresponds with a decline in the reported frequency of the most intense (and thus most damaging) tornadoes since 1950. However, quantification of trends in tornado incidence is made difficult due to discontinuities in the reporting of events over time. The normalized damage results are suggestive that some part of this decline may reflect actual changes in tornado incidence, beyond changes in reporting practices. In historical context, 2011 stands out as one of the most damaging years of the past 61 years and provides an indication that maximum damage levels have the potential to increase should societal change lead to increasing exposure of wealth and property.

Direct Estimation of the Cost Effectiveness of Tornado Shelters

The 2011 tornadoes are highlighted and the future of tornado research is discussed. The tornadoes of 2011 highlight a unique and the toughest problem in protecting the public from severe weather, the long-track, violent tornado. The 27 April 2011 tornado outbreak across the southern United States set a record for the most tornadoes in a 24-h period and was the second deadliest in U.S. history. To address this threat, engineers have developed safe rooms and underground shelters capable of protecting residents from even the strongest tornadoes. Permanent homes provide substantial protection for residents against most tornadic winds. Emerging technologies like mobile Doppler radars, short-wavelength radars, and phased-array radars may allow the observation of the lower levels of thunderstorms to identify the winds in a tornado. Relocation to low-probability areas would substantially reduce mobile-home fatalities and could be accomplished at relatively low cost due to the nature of mobile-home facilities.

Tornado shelters and the housing market

This article estimates the cost effectiveness of tornado shelters using the annual probability of a tornado and new data on fatalities per building struck by a tornado. This approach differs from recent estimates of the cost effectiveness of tornado shelters in Reference 1 that use historical casualties. Historical casualties combine both tornado risk and resident action. If residents of tornado-prone states take greater precautions, observed fatalities might not be much higher than in states with lower risk. Estimation using the tornado probability avoids this potential bias. Despite the very different method used, the estimates are 68 million US dollars in permanent homes and 6.0 million US dollars in mobile homes in Oklahoma using a 3% real discount rate, within about 10% of estimates based on historical fatalities. The findings suggest that shelters provide cost-effective protection for mobile homes in the most tornado-prone states but not for permanent homes.

The Determinants of Tornado Casualties and the Benefits of Tornado Shelters

Mitigation against natural hazards often involves long‐lived, immobile investments. Home owners must be able to capture the present value of future benefits to equate the private and societal return on mitigation. The capitalization of mitigation into home prices thus is crucial for home owners to have a proper incentive for mitigation. We investigate the existence of a premium for tornado shelters using home sales in Oklahoma City, where the deadly tornado outbreak of 3 May 1999 and the Oklahoma Saferoom Initiative increased public awareness of tornado shelters. We find that a shelter increases the sale price of a home by 3.5% to 4% or approximately

Taking Shelter: Estimating the Safety Benefits of Tornado Safe Rooms

4200 given the mean price of homes sold in 2005. The magnitude of the premium is plausible given that shelters retail for

Convective Storm Vulnerability: Quantifying the Role of Effective and Well-Enforced Building Codes in Minimizing Missouri Hail Property Damage

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