An Empirical Investigation of the National Weather Service's Impact Based Warnings

Last year, following a central region pilot assessment, the National Weather Service (NWS) implemented nation-wide enhanced severe weather warnings known as Impact Based Warnings (IBWs). The overarching goal of these Impact Based Warnings (IBWs) is to improve the threat warning process and motivate appropriate responses by using event tags and additional textual material that provide more specificity about the magnitude of the storm and its potential consequences. These IBWs are designed to be used by individuals in the field, such as Emergency Mangers, to make more effective decisions. To date, little research into the effectiveness of IBWs exists, although some promising research has been presented. Losego, at the 2013 AMS conference, reported that forecaster's like the tiered system of tags that provide additional information about a tornado's intensity. Hudson et al. (2013) also reported some initial validation results comparing the use of the Tornado Threat tags to the actual occurrence of a tornado in terms of hits and misses.

Given the paucity of the research on Impact Based Warnings, I have been involved in a program of investigation designed to empirically evaluate the effectiveness of such warnings. At last year's AMS conference, I presented preliminary research showing that IBWs do indeed appear to be more effective than non-IBWs. In that research, undergraduates adopted the role of a plant manager and read both IBW and non-IBW warnings line-by-line. At three different decision locations, participants made decisions about having the plant shut down and employees shelter in place. My results showed that the IBW warnings produced higher likelihoods of closing the plant and sheltering in place, but only after the additional IBW information was presented, supporting the effectiveness of the IBW approach.

The current research presented here expanded upon that initial research and includes a sample more representative of the intended audience – graduate students in an Emergency Management program. The experiment's methodology, however, was the same as before - participants adopted the role of a plant manager and read both IBW and non-IBW warnings line-by-line. At three different decision locations, using a 0-100 likelihood scale, participants made decisions about having the plant shut down and employees shelter in place. As I found before, the IBWs produced higher likelihoods of closing the plant and sheltering in place. Implications of the results will be discussed, and future plans to extend the research to include professional Emergency Managers will be highlighted.