Evaluating lead time differences on residents' responses to a tornado warning

In the aftermath of the violent tornadoes and tornado warnings in Moore and El Reno, OK in May 2013, a heated debate has emerged about the content of official messages and other risk communications meant to guide resident decision-making.  Although residents in these tornado-prone communities generally know what protective actions to take, traffic jams and fatalities among those who followed recommendations to evacuate the tornado's projected path or go underground suggest that residents were still not adequately prepared.  Besides the debate about availability and use of tornado shelters, commentators have also questioned whether lead time was sufficient for residents to evacuate or get to shelters in time. Yet as Dr. Kelvin Droegemeier suggested in his testimony to a U.S. Congress subcommittee in June 2013, the impact of increased lead time may be significantly limited if researchers do not understand what people currently do during their warning lead time. The purpose of this study is to evaluate how residents would use this time in several hypothetical tornado warning situations.

This study examined 60 participants, 30 aged 18-43 and 30 aged 60-75, who had lived in the Southeastern U.S. for at least four years. Participants were interviewed individually about their tornado experience and knowledge. Participants were asked what they would do if they were home and received a tornado warning with a 15 minute lead time. Then, they were asked what they would do if given an hour lead time and given a two-minute lead time. Participants were then asked to describe why their actions would differ between these scenarios.

To understand generally how participants behaved, we reviewed participants' responses to identify categories of activities and concerns that were considered across all timeframes.  Then, we identified characteristic activities for each category that represented how participants behaved depending on the timeframe as shown in table 1.

Table 1: Representative activities by behavioral category for three hypothetical warning lead times.

Using this framework, responses from individual interviews were evaluated to describe more systematically how participants used different amounts of warning lead time. Responses suggest that some participants had not previously evaluated the amount of time required to complete their proposed protective actions, though comparison across age groups suggests that significantly more older adults had at least implicitly evaluated their responses in prior warnings. A discussion on the influence of lead time on protective action in each category will be presented. We will also discuss recommendations for improving risk communication based on our findings.