Tornado Warning Guidance and Graphics: Implications of the Inclusion of Protective Action Information on Perceptions and Efficacy

Effective warning messages should tell people what they should do, how they should do it, and how to maximize their health and safety. Guidance essentially delivers two types of information: 1) information that instructs people about the actions to take in response to a threat, and 2) information about how and why these recommended protective actions will reduce harm. However, recent research reported that while automated tornado warnings, sent by the National Weather Service Storm Prediction Center via the account @NWStornado on Twitter, included useful information about the location of the threat, the potential impacts, and populations at risk, it failed to provide content that would contribute to successful protective actions. In this experimental study we investigate how the inclusion and presentation of protective action guidance affects participant perceptions of a tornado warning message and their perceived ability to act upon the information (i.e., self- and response-efficacy). We find that the inclusion of protective action guidance results an increase in the participants’ understanding of the message, their ability to decide what to do, and their perceived self- and response-efficacy. Knowing how to take action to protect oneself, and believing the actions will make oneself safe, are key motivators to taking action when faced with a significant threat. Future warning research should draw from other persuasive messaging and health behavior theories, and should include self- and response- efficacy as important causal factors. It should also look across additional hazards to determine if these outcomes differ by the length of forewarning and hazard type.

An Analysis of 2016-2018 Tornadoes and National Weather Service Tornado Warnings across the contiguous United States

Previous work has considered tornado occurrence with respect to radar data, both WSR-88D and mobile research radars, and a few studies have examined techniques to potentially improve tornado warning performance. To date, though, there has been little work focusing on systematic, large-sample evaluation of National Weather Service (NWS) tornado warnings with respect to radar-observable quantities and the near-storm environment. In this work, three full years (2016–2018) of NWS tornado warnings across the contiguous United States were examined, in conjunction with supporting data in the few minutes preceding warning issuance, or tornado formation in the case of missed events. The investigation herein examines WSR-88D and Storm Prediction Center (SPC) mesoanalysis data associated with these tornado warnings with comparisons made to the current Warning Decision Training Division (WDTD) guidance.Combining low-level rotational velocity and the significant tornado parameter (STP), as used in prior work, shows promise as a means to estimate tornado warning performance, as well as relative changes in performance as criteria thresholds vary. For example, low-level rotational velocity peaking in excess of 30 kt (15 m s−1), in a near-storm environment which is not prohibitive for tornadoes (STP > 0), results in an increased probability of detection and reduced false alarms compared to observed NWS tornado warning metrics. Tornado warning false alarms can also be reduced through limiting warnings with weak (<30 kt), broad (>1nm) circulations in a poor (STP=0) environment, careful elimination of velocity data artifacts like sidelobe contamination, and through greater scrutiny of human-based tornado reports in otherwise questionable scenarios.

Evaluating Precursor Signals for QLCS Tornado and Higher Impact Straight-Line Wind Events

Tornadoes produced by quasi-linear convective systems (QLCS) present a significant challenge to National Weather Service warning operations. Given the speed and scale at which they develop, different methods for tornado warning decision making are required than what traditionally are used for supercell storms. This study evaluates the skill of one of those techniques—the so-called three-ingredients method—and produces new approaches. The three-ingredients method is found to be reasonably skillful at short lead times, particularly for systems that are clearly linear. From the concepts and science of the three-ingredients method, several new combinations of environmental and radar parameters emerge that appear slightly more skillful, and may prove easier to execute in real time. Similar skill between the emerging methods provides the forecaster with options for what might work best in any given scenario. A moderate positive correlation with overall wind speed with some radar and environmental variables also is identified. Additionally, mesoscale convective vortices and supercell-like features in QLCS are found to produce tornadoes at a much higher rate than purely linear systems.

Identifying Risk and Resilience Factors Impacting Mental Health among Black and Latinx Adults following Nocturnal Tornadoes in the U.S. Southeast

Prior research has found that Black and Latinx communities in the U.S. face significant disparities that impact both preparedness for severe weather events and the support received after a disaster has occurred. In the current study, we examined key risk and protective factors that impacted mental health among 221 Black and Latinx adult respondents exposed to the 2–3 March 2020 nocturnal tornado outbreak in the U.S. state of Tennessee. Key factors that adversely affected mental health among participants were encountering barriers for receiving tornado warning alerts and tornado-related exposure. Key factors that served a protective mechanism against adverse mental health included having access to physical resources, supportive relationships, and adaptive coping skills. These findings may assist National Weather Service (NWS) personnel, emergency managers, and mental health providers with the development of policies and practices to address barriers and promote protective strategies for future nocturnal tornado events.

Examining sub-daily tornado warning performance and associated environmental characteristics

Increasing tornado warning skill in terms of the probability of detection and false alarm ratio remains an important operational goal. Although many studies have examined tornado warning performance in a broad sense, less focus has been placed on warning performance within sub-daily convective events. In this study, we use the NWS tornado verification database to examine tornado warning performance by order-of-tornado within each convective day. We combine this database with tornado reports to relate warning performance to environmental characteristics. On convective days with multiple tornadoes, the first tornado is warned significantly less often than the middle and last tornadoes. More favorable kinematic environmental characteristics, like increasing 0–1-km shear and storm-relative helicity, are associated with better warning performance related to the first tornado of the convective day. Thermodynamic and composite parameters are less correlated to warning performance. During tornadic events, over half of false alarms occur after the last tornado of the day decays, and false alarms are twice as likely to be issued during this time than before the first tornado forms. These results indicate that forecasters may be better “primed” (or more prepared) to issue warnings on middle and last tornadoes of the day, and must overcome a higher threshold to warn on the first tornado of the day. To overcome this challenge, using kinematic environmental characteristics and intermediate products on the watch-to-warning scale may help.

The Influence of Weather Watch Type on the Quality of Tornado Warnings and its Implications for Future Forecasting Systems

While many studies have looked at the quality of forecast products, few have attempted to understand the relationship between them. We begin to consider whether or not such an influence exists by analyzing storm-based tornado warning product metrics with respect to whether they occurred within a severe weather watch and, if so, what type of watch they occurred within.The probability of detection, false alarm ratio, and lead time all show a general improvement with increasing watch severity. In fact, the probability of detection increased more as a function of watch-type severity than the change in probability of detection during the time period of analysis. False alarm ratio decreased as watch type increased in severity, but with a much smaller magnitude than the difference in probability of detection. Lead time also improved with an increase in watch-type severity. Warnings outside of any watch had a mean lead time of 5.5 minutes, while those inside of a particularly dangerous situation tornado watch had a mean lead time of 15.1 minutes. These results indicate that the existence and type of severe weather watch may have an influence on the quality of tornado warnings. However, it is impossible to separate the influence of weather watches from possible differences in warning strategy or differences in environmental characteristics that make it more or less challenging to warn for tornadoes. Future studies should attempt to disentangle these numerous influences to assess how much influence intermediate products have on downstream products.

An analysis of tornado warning reception and response across time: leveraging respondent's confidence and a nocturnal tornado climatology

Nocturnal tornadoes are challenging to forecast and even more challenging to communicate. Numerous studies have evaluated the forecasting challenges, but fewer have investigated when and where these events pose the greatest communication challenges. This study seeks to evaluate variation in confidence among US residents in receiving and responding to tornado warnings by hour-of-day. Survey experiment data comes from the Severe Weather and Society Survey, an annual survey of US adults. Results indicate that respondents are less confident about receiving warnings overnight, specifically in the early morning hours (12 AM to 4 AM local time). We then use the survey results to inform an analysis of hourly tornado climatology data. We evaluate where nocturnal tornadoes are most likely to occur during the time frame when residents are least confident in their ability to receive tornado warnings. Results show that the Southeast experiences the highest number of nocturnal tornadoes during the time period of lowest confidence, as well as the largest proportion of tornadoes in that time frame. Finally, we estimate and assess two multiple linear regression models to identify individual characteristics that may influence a respondent’s confidence in receiving a tornado between 12 AM and 4 AM. These results indicate that age, race, weather awareness, weather sources, and the proportion of nocturnal tornadoes in the local area relate to warning reception confidence. The results of this study should help inform policymakers and practitioners about the populations at greatest risk for challenges associated with nocturnal tornadoes. Discussion focuses on developing more effective communication strategies, particularly for diverse and vulnerable populations.

Improving Tornado Warning Communication for Deaf and Hard of Hearing Audiences

Although specialized personal and residential Deaf warning technologies exist, receipt and comprehension of tornado warning information from local television is often delayed or misunderstood because of closed-captioning deficiencies. In order to suggest improvements for the communication of tornado warnings to Deaf and Hard of Hearing (D/HoH) audiences, interviews and a focus group were conducted within the active tornado counties of Alabama. D/HoH individuals generally use more information sources than the hearing population to better understand their risk. Protective action decision-making by our sample was characterized by more hesitation, uncertainty, and indecision than in the hearing population. The most common suggestion for improving tornado-warning communication was to have an American Sign Language (ASL) interpreter shown on screen with a local television meteorologist during a tornado warning. A split-screen television product with an ASL interpreter in a remote studio was prototyped showing that this type of live broadcast is possible for local tornado-warning coverage. Several screen formats were evaluated by a focus group with the conclusion that the ASL interpreter should be on the left side of the screen without obscuring any part of the weather broadcast. The split-screen product with an ASL interpreter resulted in full access to all broadcast information, the ability to make immediate safety decisions, and was welcomed with excitement by the focus-group participants. This modification, along with the education and preparedness efforts of the National Weather Service, help remedy the information gaps and comprehension delays of this underserved population.

Anticipating Deviant Tornado Motion Using a Simple Hodograph Technique

The paths of tornadoes have long been a subject of fascination since the meticulously drawn damage tracks by Dr. Tetsuya Theodore “Ted” Fujita. Though uncommon, some tornadoes have been noted to take sudden left turns from their previous path. This has the potential to present an extreme challenge to warning lead time, and the spread of timely, accurate information to broadcasters and emergency managers. While a few hypotheses exist as to why tornadoes deviate, none have been tested for their potential use in operational forecasting and nowcasting. As a result, such deviations go largely unanticipated by forecasters. A sample of 102 leftward deviant tornadic low-level mesocyclones was tracked via WSR-88D and assessed for their potential predictability. A simple hodograph technique is presented that shows promising skill in predicting the motion of deviant tornadoes, which, upon “occlusion,” detach from the parent storm’s updraft centroid and advect leftward or rearward by the low-level wind. This metric, a vector average of the parent storm motion and the mean wind in the lowest half-kilometer, proves effective at anticipating deviant tornado motion with a median error of less than 6 kt (1 kt ≈ 0.51 m s−1). With over 25% of analyzed low-level mesocyclones deviating completely out of the tornado warning polygon issued by their respective National Weather Service Weather Forecast Office, the adoption of this new technique could improve warning performance. Furthermore, with over 35% of tornadoes becoming “deviant” almost immediately upon formation, the ability to anticipate such events may inspire a new paradigm for tornado warnings that, when covering unpredictable behavior, are proactive instead of reactive.

Compared to What? Establishing Environmental Baselines for Tornado Warning Skill

Capsule summaryApplying information from tornadic near-storm environments allows for the development of explicit, meaningful, and mutable baselines of expected skill when evaluating tornado forecasts.