Reflecting on a Decade of Formalized Tornado Emergencies

Beginning in 1999, the National Weather Service (NWS) began using the term “tornado emergency” to highlight tornado warnings for storms which posed considerable threats to life and property. After years of this phrasing being used informally, tornado emergencies were officially introduced to 46 forecasting offices in 2014 as part of the impact-based warning (IBW) program. This framework contains 3 potential tags for tornado warnings: base, considerable, and catastrophic, where the catastrophic tag uses the tornado emergency phrasing. Though significant research has studied both tornado forecasting and tornado warning dissemination in the decade since, relatively little work has been done to examine the effectiveness of the catastrophic tag specifically. An analysis of all 107 tornado emergencies from 2014-2023 shows that suggested guidelines published by the Warning Decision Training Division (WDTD) for rotational velocity (VROT) and significant tornado parameter (STP) thresholds may not always be prioritized by forecasters when issuing warnings. For example, 80% of tornado emergencies were issued for environments characterized by STP less than 6, the recommended lower bound. Regardless, tornado emergencies are shown to be fairly effective at separating weak tornadoes from violent tornadoes with 16.9% of violent (EF-3 or greater) tornadoes covered by tornado emergencies versus 0.2% of weak tornadoes. 68% of all tornado emergencies were for violent tornadoes. Additional analysis explores the potential impact of population density on tornado emergency issuance. Future avenues of research, particularly focused on interviewing forecasters and determining the public’s perception of tornado emergencies, will also be discussed.