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Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings
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Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings

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Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings

Risk Perception and the Credibility of Hazard Warnings: Evidence from Tornado Warnings

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  • 1. Credibility of Hazard Warnings: Evidence from Tornadoes Kevin M. Simmons Austin College Fulbright Research Scholar International Centre for GeoHazards Oslo, Norway
  • 2. Economic and Societal Impacts of Tornadoes By Kevin M. Simmons and Daniel Sutter © 2010, 296 pages in paperback ISBN: 978-1-878220-99-8 AVAILABLE NOVEMBER 2010 from the American Meteorological Society and the University of Chicago Press
  • 3.  
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  • 9. Warnings Save Lives <ul><li>Fatality Rate in the 1920’s was 1.8 per million </li></ul><ul><li>Today it is estimated at .11 per million </li></ul>
  • 10. Warning Errors <ul><li>The value of a weather forecast or warning in an expected value framework depends on the reliability of the information signal. </li></ul><ul><li>Two error probabilities are relevant, the probability a tornado occurs unwarned, and the probability a warning is issued when no tornado occurs. </li></ul><ul><li>The second probability corresponds to the False Alarm Ratio (FAR) that the NWS reports for tornadoes and other types of warnings. </li></ul>
  • 11. NWS Metrics for Performance <ul><li>The National Weather Service has 3 metrics to evaluate the performance of tornado warnings. </li></ul><ul><ul><li>Lead Time </li></ul></ul><ul><ul><li>Probability of Detection </li></ul></ul><ul><ul><li>False Alarm Rate </li></ul></ul>
  • 12. NWS Metrics for Performance <ul><li>Leadtime </li></ul><ul><ul><li>Time from warning to first touchdown </li></ul></ul><ul><li>Probability of Detection </li></ul><ul><ul><li>Warned Tornadoes / Verified Tornadoes </li></ul></ul><ul><li>False Alarm Rate </li></ul><ul><ul><li>1 – (Verified Tornadoes / Warnings) </li></ul></ul>
  • 13. The False Alarm Effect <ul><li>A higher FAR should reduce the value of a tornado warning and might induce people to ignore the warning. </li></ul><ul><li>Yet evidence of a false alarm effect in the field has been elusive. </li></ul><ul><li>A recent study notes “Evidence for the cry-wolf effect in natural hazards research, however, has not been forthcoming.” (Barnes et al. 2007) </li></ul>
  • 14. Is there a False Alarm Problem? <ul><li>A false alarm problem exists if a resident in the path of a tornado chooses not to respond to the warning. </li></ul>
  • 15. In Econo Lingo: <ul><li>Utility of taking cover given an approaching tornado is less than the Utility of not taking cover, given an approaching tornado. </li></ul>
  • 16. How Can This Happen?
  • 17. Empirical Test <ul><li>Can we find a way to test whether or not increases in false alarms have an impact on casualties from tornadoes? </li></ul>
  • 18. False Alarms and Casualties <ul><li>We calculate a recent, local FAR, use this as a control variable in our casualty regressions. If false alarms reduce warning response, this should translate into more casualties, everything else equal. </li></ul><ul><li>We have tried six different definitions of the FAR in our research. </li></ul>
  • 19. Econometric Models <ul><li>The number of persons killed or injured in a tornado takes on nonnegative integer values with a large portion of zeros, and thus is count data. </li></ul><ul><li>We estimate Poisson models of casualties and test for overdispersion. Injuries are generally overdispersed, but not fatalities, so we estimate Negative Binomial models for injuries. </li></ul>
  • 20. Data Set for Tornadoes <ul><li>Storm Prediction Center national tornado archive </li></ul><ul><li>NWS Tornado Warning Verification records </li></ul><ul><li>County warning areas of NWS forecast offices, Doppler radar installation dates </li></ul><ul><li>Census data at county level </li></ul>
  • 21. Study Parameters <ul><li>Database includes all tornadoes in the U.S. between 1986 and 2004. </li></ul><ul><li>Approximately 21,000 tornadoes. </li></ul><ul><li>County level census data from the 1980, 1990 and 2000 census. </li></ul>
  • 22. Control Variables in Tornado Casualty Analysis <ul><li>Tornado characteristics: Rating on the Fujita(F) scale, path length, time of day, month of year, day of week </li></ul><ul><li>Path characteristics: Economic and demographic variables for the counties struck by each tornado </li></ul><ul><li>Warning variables: Warning in effect, lead time, false alarm ratio </li></ul>
  • 23. Results Injury Model <ul><li>Injuries </li></ul><ul><ul><li>A 1 standard deviation increase in the one year FAR increases injuries from 12.4 to 14.7% </li></ul></ul>
  • 24. Results Fatality Model <ul><li>Fatalities </li></ul><ul><ul><li>A 1 standard deviation increase in the one year FAR increases fatalities from 12.7 to 18.4% </li></ul></ul>
  • 25. THANK YOU FOR YOU ATTENTION

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