May 22 - July 31
Tornado Warnings, Lead Time, and Death
Rumer Chatwin, Harold Brooks, and Kim Klockow-McClain
What is already known:
- The Sutter and Simmons (2008) paper suggests tornado warnings with lead times up to 15 minutes reduces the number of fatalities, but not much can be said for longer lead times.
- Numerous studies assume that by extending the lead time of tornadoes the number of casualties caused by the disaster will reduce significantly; however, there is no qualitative research that backs this claim up.
What this study adds:
- When a tornado warning is issued in advance, the distribution of lead time is relatively the same across several decades.
- In the most recent decade, there has been a fluctuation in shorter lead times for tornadoes scaled as EF-0, EF-1, and EF-Unknown.
- No evidence points to statistical significance in the relationship between lead time and death, resulting in the conclusion that a longer lead time does not decrease the number of fatalities in a tornado event.
Abstract:
Intuitively people believe that when a tornado has longer lead time, there will be a higher probability of reducing fatalities in an event. Sutter and Simmons (2009) created a model to qualitatively prove the effects of lead time on death; however, the results were inconclusive due to finding no obvious trend. We examine the lead time for tornadoes warned in advance using data provided by the National Weather Service Performance Management Branch’s verification system starting in January 1986 to December 2023 by creating probabilistic graphs. We come to three conclusions about the relationship between tornado warnings, lead time, and death: the distribution of lead time across the data set has changed little over time, forecasters are issuing more shorter lead times for weak tornadoes than ever before, and there is no statistically significant relationship between death and lead time.