Examining the Efficacy of the Tornado Emergency: A Case Study of the 19 July 2018 Marshalltown, Iowa, Tornado

The National Weather Service (NWS) uses “impact based intensity tags” within warnings to enhance messaging for particularly strong/dangerous storms, including the rarely used “Tornado Emergency”, in order to increase the urgency of the warning. Although social science is a rapidly growing area within the field of meteorology, little has been investigated, at least formally, on the use of the catastrophic tag and subsequent Tornado Emergency wording within tornado warnings. Previous research examines the difficulty in communicating with Emergency Managers (EMs) due to diversity with respect to their jurisdictions and responsibilities (Baumgart and Bass 2008; Weaver et al. 2014). At the same time, research has also indicated that effective communication between the NWS and Integrated Warning Team (IWT) members greatly increases the chances both that the public will receive hazard information and that they will act on it (Cavanaugh et al. 2016). EMs in particular rely on NWS forecasters in analyzing and using hazard information correctly and effectively. To that end, it is imperative that the flow of information from the NWS is clear, informative, and displays the proper sense of urgency so that EMs can make informed decisions in rapidly evolving situations. Because of the rarity of the Tornado Emergency, it is possible that EMs may be unaware of this category before an event, and if they do not read the warning text, may not be aware of it even after issuance.

This study seeks to determine how or if these impact based warning tags were used by partners such as emergency management, first responders, and media partners during the Marshalltown EF-3 tornado on 19 July 2018 - the first tornado emergency ever issued by the Des Moines Weather Forecast Office (WFO). Focus groups consisting of emergency managers, first responders, and local decision makers were conducted, revolving around communication and response during the event, with particular interest in the awareness of and use of the Tornado Emergency as the tornado entered Marshalltown. We will discuss key themes and results from this effort, including a discussion of the implications for communication between the NWS and IWT members during weather emergencies.