Tornado Warning - Communication Processes of a severe Weather Crisis

Transcription

1 METEOROLOGICAL APPLICATIONS Meteorol. Appl. 17: (2010) Published online 17 May 2010 in Wiley InterScience ( DOI: /met.201 Emergency manager decision-making and tornado warning communication Cedar E. League, a * Walter Díaz b, Brenda Philips c,ellenj.bass d,kevinkloesel e, Eve Gruntfest a and Alex Gessner d a Trauma, Health & Hazards Center, University of Colorado-Colorado Springs, Colorado Springs, CO, USA b Center for Applied Social Research, University of Puerto Rico-Mayagüez, Mayagüez, PR, USA c Center for Collaborative Adaptive Sensing of the Atmosphere, University of Massachusetts-Amherst, Amherst, MA, USA d Department of Systems and Information Engineering, University of Virginia, Charlottesville, VA, USA e College of Atmospheric and Geographic Sciences, University of Oklahoma, Norman, OK, USA ABSTRACT: Emergency managers (EMs) play a critical role in communicating severe weather and tornado warnings to the public, yet communicating the uncertainty of when, where or if a tornado may hit remains a great challenge for EMs. Focus group and survey data concerning weather product usage, weather observing spotter interaction, and decisions to warn the public were collected from Oklahoma EMs in order to characterize the communication processes EMs employ during severe weather outbreaks. These processes include: (1) acquiring weather information, (2) interpreting the information in order to make weather hazard threat assessments, (3) verifying the information, and (4) making time-sensitive warning decisions. The results indicate that while EMs use a variety of weather and radar products to acquire information, weather observing spotters are key sources of verification data. With respect to warning the public about tornado threats, sirens are the primary method. These findings are related to the development of a new radar system being developed by the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), so that this new technology can be designed to reduce uncertainty in the EM decision-making and warning communication processes. Copyright 2010 Royal Meteorological Society KEY WORDS emergency management; tornado warnings; weather radar; spotters; user-centred system design Received 1 December 2009; Revised 23 February 2010; Accepted 31 March Introduction Tornadoes are one of the most dangerous severe weather events occurring in the United States, threatening lives and causing extensive damage to property. Based on 2008 National Weather Service (NWS) statistics, there were 1691 confirmed tornadoes, with 124 lives lost, 1711 injuries and over $1.7 billion of property and crop damage in the United States (NWS, 2009a). Annually in the United States, an average of 1200 tornadoes injures 1500 people, resulting in 55 fatalities (National Oceanic and Atmospheric Administration NOAA, 2004). Average annual insured losses from tornadoes in the United States equal $982 million (Changnon, 2009). Tornado forecasts and warnings in the United States have greatly improved since the deployment of a network of 159 Next Generation Radars [NEXRAD: Weather Surveillance Radar-1988 Doppler (WSR-88D)] during the mid-1990s (Bieringer and Ray, 1996; Golden and Adams, 2000). Improvements in radar technology have subsequently reduced the number of tornado deaths, likely from improved warnings (Simmons and Sutter, * Correspondence to: Cedar E. League, Trauma, Health & Hazards Center, University of Colorado-Colorado Springs, P.O. Box 7150, Colorado Springs, CO 80933, USA. cedarleague@gmail.com 2005). Decreased tornado losses have further been attributed to improved communications between both the providers of hazardous weather information and the public ultimately receiving it, improved construction methods, better communication with trained storm spotter networks (Brooks and Doswell, 2001), and an increase in public awareness (Doswell et al., 1999; American Meteorology Society (AMS) Council, 2000). Despite these improvements, tornadoes remain difficult to predict with devastating results to the impacted communities. Along with the media and weather forecasters, emergency managers play a critical role in an integrated warning system that communicates tornado warning information to the public (Doswell et al., 1999). While it is the role of the NWS to assess weather threats on a regional level and to issue official tornado warnings, EMs assess severe weather threats on a town or county basis. In addition, EMs are the critical link in distributing warnings to the public using a variety of methods, such as activating sirens, notifying schools, hospitals and other critical services, activating an emergency alert system, cable television interrupt, or a reverse emergency call-out system. Yet, communicating the uncertainty of if, when and where a tornado may occur remains a great challenge for EMs. Copyright 2010 Royal Meteorological Society

2 164 C. E. LEAGUE ET AL. Figure 1. NEXRAD WSR-88D coverage at 1 km above ground level in the United States. Radars are spaced approximately 230 km apart in the eastern half of the United States, and approximately 345 km apart in the western half of the United States. Each disk is approximately 75 km in radius, which is the distance from the radar where the boresight of the NEXRAD beam crosses up through 1000 m when the antenna is tilted at its lowest allowable tilt angle of 0.5. (Maddox et al., 2002 American Meteorological Society. Reprinted with permission). In the decision making and communication process, EMs acquire multiple types of information to increase awareness and to guide their efforts in seeking corroborating evidence (Morss and Ralph, 2007; Baumgart et al., 2008). These sources of information include weather forecasts, assessments of the current situation, environmental cues, and local knowledge about the vulnerability of an area. In Oklahoma, OK-FIRST (Morris et al., 2001) is an outreach and decision-support project of the Oklahoma Climatological Survey that provides training and weather data to about 250 public safety officials in the state, out of 434 jurisdictions (K Kloesel, personal communication, 24 November 2009). Due to the success of OK-FIRST, Oklahoma EMs are generally knowledgeable users of weather information as about 58% are trained in the use of weather and radar data. During the weather hazard threat assessment phase, emergency managers communicate with weather observing storm spotters, first-responders and the NWS for weather assessment validation during a severe weather event (Baumgart et al., 2008). As weather observing storm spotter reports can provide the impetus in issuing official NWS tornado warnings, spotters play a key role in the detection of tornadoes, providing groundtruth information to emergency managers, local officials and the NWS (Doswell et al., 1999; McCarthy, 2002). Spotter networks are generally comprised of volunteers or public works employees and may be trained by the NWS through its SKYWARN programme. While some spotters respond on their own, others are deployed by EMs or the NWS when severe weather conditions threaten. The need for weather observing spotters stems from a key limitation of the current NEXRAD WSR-88D radar network. These radars cover long ranges and can observe upper and mid levels, but are not able to observe low to the ground where tornadoes occur (Figure 1) (Maddox et al., 2002). For example, the current NEXRAD system cannot sense more than 70% of the troposphere below 1 km altitude above ground level (AGL) (Maddox et al., 2002). This coverage gap presents a problem for EMs who are concerned with tornado touchdowns within their jurisdictions. To address this coverage issue and related sensing and prediction concerns, the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), a National Science Foundation funded Engineering Research Center, is developing inexpensive, low-power, high-resolution networks of x-band Doppler radars designed to improve scanning of the lowest levels (<3 km) of the atmosphere. These short range radars result in increased spatial resolution (median 0.5 km vs 2.5 km), temporal resolution (update rates of 60 s vs 4 5 min), and more complete coverage at lower elevations (100% coverage below 1 km AGL vs about 30%) (McLaughlin et al., 2009) when compared to the WSR-88Ds. CASA radars are designed and deployed to operate as a dense network, providing overlapping coverage. CASA s system architecture, referred to as Distributive Collaborative Adaptive Sensing (DCAS), is end-user driven, focusing on allocating scanning strategies where and when EM and forecaster needs are greatest (Philips et al., 2007). Emergency managers have noted that the type of hazard, its severity and its potential impact should play a primary role in the allocation of adaptive radar resources (Rodríguez et al., in press). Four experimental CASA radars operate during storm season (March to May) in southwest Oklahoma. This endto-end testbed is located in the heart of tornado alley. The state of Oklahoma averages 53 tornados per year (NWS, 2009b). Through the operation of the testbed, CASA has demonstrated the ability to detect low level circulations, horizontal winds and downdrafts that are

3 EMERGENCY MANAGER ROLE IN COMMUNICATING TORNADO WARNINGS 165 not easily detected by the current system (Brotzge et al., 2010). This new technology has the potential to increase lead-time for tornado warnings through earlier detection, reduce false alarms and reduce uncertainty in end-user decision-making (Rude et al., 2009). In order to make advances in new technology most effective, a better understanding of the weather hazard assessment and warning communication processes as well as the behavioural response to severe weather events is needed (e.g. Golden and Adams, 2000; Sorenson, 2000; Montz and Gruntfest, 2002; Parker et al., 2009). Understanding individuals use of information across spatial and temporal scales and their use of different components of forecasts can help providers develop better information products to meet the public s needs (Lazo et al., 2009). To this end, CASA s End User Integration (EUI) thrust has been using a mixed methods approach including in-depth interviews (Donner, 2008), surveys, analysis of product usage logs and simulated scenarios (Baumgart et al., 2008) to solicit EM input (for a summary, see Bass et al., 2009). This prior research indicates that social, environmental, and technological forces shape the organizational decision-making processes of emergency managers, as well as the need for products for both high and low bandwidth end-users, visualizations for velocity products that are more easily interpreted and the need for enhanced training. Using Oklahoma as a case study, the work described herein outlines the decision-making and communication process that EMs in the United States employ during severe weather outbreaks. Communicating risk is an interactive process, involving the sending and receiving of messages, threat sensing and assessment leading to the production of public messages regarding environmental hazards (Reynolds and Seeger, 2005). Three focus groups and a self-administered survey were conducted with Oklahoma EMs in order to understand how EMs: (1) acquire weather information, (2) interpret that information in order to make weather hazard threat assessments, (3) verify the information through interaction with spotters, and (4) communicate time-sensitive warning decisions to the public. This paper summarizes these efforts and discusses how the EM communication process may inform the development of CASA technology which could ultimately reduce uncertainty in communicating tornado warnings to the public. Thus, within the overall project s end-toend approach, it falls within the critical junction between the generation of weather observation and forecasts, the dissemination of warning information when hazardous weather is detected or predicted, and the public s reaction to such warnings. Section 2 presents the quantitative and qualitative data collection and analysis methodology. Section 3 presents and discusses the results. Before a risk can be communicated to the public, a decision-maker must first become aware of the risk. Emergency managers use multiple sources to acquire weather information (Morss and Ralph, 2007; Baumgart et al., 2008), and EMs collect weather information at varying frequencies during the threat-assessment process. Thus, Section 3.1 examines how EMs acquire weather information with respect to sources and usage frequency. While weather information sources provide perceptual cues, emergency manager decisions are also influenced by other factors such as time of day, training, experience, approach to risk, location of the storm and knowledge of any NWS actions already taken (Baumgart et al., 2008). In order to interpret weather information correctly, training and experience using weather and radar data is important. Thus Section 3.2 examines how EMs interpret weather information based on training and experience. Section 3.3 examines how EMs verify weather information using storm spotters. After a threat is identified, emergency managers are responsible for making time-sensitive decisions to warn the public of that threat. Section 3.4 examines how EMs make and distribute time-sensitive warning decisions with a focus on ideal warning lead times. The conclusion section illustrates how EMs communicate warnings to the public, and how this process may inform the development of new radar technology to suit the needs of its users. It discusses ideas for further investigation. 2. Methods A mixed method approach was used, collecting both quantitative and qualitative data through a self-administered survey and three focus groups with Oklahoma emergency managers Quantitative methods Quantitative data were collected from a self-administered survey with 62 emergency managers at the Oklahoma Emergency Management Association (OEMA) annual meeting in September, The Emergency Manager Tornado Warning and Technology Survey consisted of 50 questions regarding EM experience, jurisdiction type, radar usage and training, communications, sources available to receive and distribute tornado warning information, and spotter deployment procedures. The survey was pre-tested with several Oklahoma EMs and revised before final deployment. The survey also probed the daily usage frequency of 11 different sources of weather information when no severe weather is expected, and during the period 1 h before the predicted occurrence of a severe weather event. Product usage frequency was classified using a four point scale: (1) every few minutes, (2) every few hours or more, (3) once or twice a day, or (4) rarely or never Qualitative methods Three focus groups were held with a total of 55 Oklahoma EMs who attended the 2009 OEMA annual meeting. According to Morgan (2006), qualitative methods complement quantitative research in that qualitative methods

4 166 C. E. LEAGUE ET AL. Figure 2. Percentage of EMs self-reported frequency of use of weather sources during a typical day when severe weather is not expected (n = 62). Every few minutes. Every few hours or more. Once or twice a day. Rarely or never. Figure 3. Percentage of EMs self-reported frequency of use of weather sources during the time period 1 h before and through the occurrence of a severe weather event (n = 62). Every few minutes. Every few hours or more. Once or twice a day. Rarely or never. typically provide interpretive resources for understanding the results from the quantitative research. Therefore, focus group discussions are used to understand results from the survey further. The focus group instrument included open-ended questions addressing the information acquisition and communication process of EMs including: (1) use of weather and radar data, (2) use of spotter networks, and (3) resources available to disseminate public warnings and procedures used to warn the public of tornadoes. Each focus group session was audio recorded and moderated by CASA researchers. Each session lasted approximately 100 min Results and discussion Acquiring weather information Emergency managers were surveyed to find out which weather products they use and how often they access Copyright 2010 Royal Meteorological Society each product both when no severe weather is expected (Figure 2) as well as in the hours and minutes leading up to a severe weather event (Figure 3). EMs self-report that multiple weather information products are used every few minutes or more in the period 1 h before and through the occurrence of a severe weather event. WSR-88D radar data and OK-FIRST data (such as surface observations), NWS text products, and spotter reports are the most frequently used sources the day of an event. However, when severe weather is not expected, EMs report using these same products only once or twice a day. The majority of EMs report rarely or never using data from a private weather provider. Survey results indicate that most EMs (86%) report routinely using radar in their daily operations. EMs use an average of four different sources to receive radar data. The primary sources include OK-FIRST (87%) and NWS sites (84%), but many EMs also view local TV radar (80%). Referring to the importance of radar, an EM said Meteorol. Appl. 17: (2010)

5 EMERGENCY MANAGER ROLE IN COMMUNICATING TORNADO WARNINGS 167 Figure 4. Percentage of emergency managers who received training in the interpretation of radar (dark grey) or did not receive training (light grey) and their self-reported ability to interpret radar information ranging from very good to not good at all (n = 60). Received Training. Did not receive training. during a focus group session that If you have a picture of what you think is going to happen... then you re a little bit better prepared. Emergency managers compare OK-FIRST to a one stop shop for receiving weather data. While radar is important, one EM said, I think if we are going to do our job right here, we have to understand everything that lies before that radar, surface maps... CAPE maps... everything else, so that you understand all those things... I can look at the OK-FIRST site and I can pick the tabs I want to review. When a severe weather threat is first predicted, focus group participants indicate that they make initial preparations by informing their administration that severe weather conditions may be present that day, and they make a decision whether or not to alert storm spotters, and to identify which spotters are available that day Interpreting information Though weather information is of great importance, its interpretation is influenced by many other factors including the EMs training and experience (Baumgart et al., 2008). Through the survey, EMs reported their experience as an EM, described what training they have received in the interpretation of radar information, and rated their ability to interpret radar data. Their experience as EMs ranged from 2 months to 42 years of service, with an average of 11 years, median 8 years and a standard deviation of Of the 62 EMs surveyed, 68% received training in the interpretation of radar either from the NWS and/or OK-FIRST. The majority of those surveyed (64%) specifically received OK-FIRST training (above the statewide OK-FIRST participation rate which is 58%). Those EMs who routinely use radar rated their ability to interpret radar data on a five-point scale ranging from very good to not good at all (Figure 4). Twenty-three of the 41 trained EMs reported their skills as good. A Mann Whitney U test indicated that those who have radar training self-report statistically significant better radar interpretation skill ratings than those who have not been trained (z = 2.239; p = 0.025) where those trained had an average rank of and those not trained had an average rank of Thus, in general, those surveyed are experienced in the field of emergency management, have received training in radar interpretation, and routinely use radar in their daily operations. Therefore, once EMs receive weather information, most EMs report having the ability to accurately interpret that information. One EM pointed during a focus group session that while OK-FIRST is useful for basic training, it s up to you to improve and refine your skills. Therefore, continued training is an important component in the interpretation of weather information. Implementing new radar technology such as CASA must take into consideration the diversity of EMs in terms of their experience, training levels and duties. Emergency managers are diverse, coming from a variety of backgrounds, jurisdictions and training levels. With limited time and resources available when a tornado threat is imminent, products must be flexible, easy to interpret and tailored to training level. Therefore, to support EM decision-making, initial and continued training in the interpretation of new radar technologies is essential Verifying information Once the potential for a severe weather threat is identified, an EM may gather additional perceptual cues from various sources such as storm spotters or NWS forecasters (Baumgart et al., 2008) before warning the public. These additional resources aid in the verification of severe weather threats. In regard to storm movement, an EM noted during a focus group session that, Radar will show a pattern of where it s going, but once it s in our area, then it s the eyes and ears of our spotters.

6 168 C. E. LEAGUE ET AL. Figure 5. CASA wind vector products enable easier interpretation of wind threats. Figure courtesy of V. Chandrasekar, Colorado State University, and J. Gao, K. Brewster, J. Brotzge, K. Thomas, Y. Wang, and M. Xue, University of Oklahoma. To understand how storm spotters are used in verifying severe weather threats, spotter profiles, deployment practices and communication resources were identified. Survey results show the majority of EMs (82%) regularly use spotters when a tornado threat is present. Spotters were identified as public employees (police, fire), local volunteers, SKYWARN trained spotters, amateur radio operators or a combination of those. Spotters are both mobile and stationary, and EMs primarily communicate with spotters by cell phone, radio, and/or amateur radio. About half of the EMs reported that spotters always or sometimes self-deploy. Reasons cited on the survey as to why spotters sometimes self-deploy included: Depends on the situation ; or Most are very weather aware and know their spot ; and When the EM is not available to deploy. If spotters do not self deploy, radar can also be an important tool in spotter deployment. Of those EMs who deploy their spotters, 76% report using radar to determine where to place spotters. During a focus group session, an EM in Oklahoma noted, We tell our spotters where we want them to go to. We have a number of predetermined locations where we know we have good visibility and communications from high points in the county... They re moved to safety according to the radar. Most spotters do not have access to radar data while in the field (64%); therefore communications with EMs and the NWS who are accessing radar data are critical to help keep spotters safe in the field. This is especially true after sunset when it is difficult to see cloud formations, and during rain-wrapped events. During a focus group session an EM noted, I think spotters are very valuable... I think they give you a realistic point of view on land-marking, where they re at, which direction it s travelling... One of the problems you find with spotters is nightfall. Once it becomes nightfall or it s rain-wrapped, they can t see it. This highlights the level of uncertainty EMs face when deciding to warn or not warn the public of tornadoes. Several EMs mentioned during a focus group that they are in a NEXRAD hole meaning their jurisdiction Copyright 2010 Royal Meteorological Society experiences a gap in radar coverage because of their distance from the radar. One EM mentioned several tornadoes came through his jurisdiction undetected and never showed up on radar. EMs also expressed concern with the resolution of NEXRAD noting it is difficult to direct spotters using a rough blob of radar data. An EM said better radar resolution could help EMs develop better instincts about which storms to be concerned and which ones to ignore. Emergency managers were very interested in CASA s experimental low level velocity products that make perceptually apparent information such as severe wind speed and direction (see Figures 5 and 6 as examples). With the uncertainty surrounding the verification of tornado information, the potential benefits of CASA s lower troposphere, higher temporal and spatial resolution data becomes apparent. CASA data can aid in the spotter deployment process and provide better capability for EMs and spotters to diagnose the storm situation during an outbreak, as well as keep spotters safe and out of the direct path of a tornado Communicating warnings to the public After a potential threat is identified, emergency managers are responsible for making time-sensitive decisions to either warn or not warn the public of that threat. These decisions are largely based on uncertain information, such as when and where a tornado will hit, or how severe the event will be. Thus, how EMs learn a tornado warning is in effect and the resources and procedures available to communicate tornado warnings to the public is examined. EMs use a variety of sources to learn that a NWSissued tornado warning is in effect. Survey results reveal the most common sources are: NOAA All Hazards Weather Radio (81%), television (76%), OK-FIRST (60%), and the NWS website (58%). Each jurisdiction has its own unique policy regarding who makes the decision to warn the public, as well as the triggers used to prompt emitting a warning. For example, EMs decisions Meteorol. Appl. 17: (2010)

7 EMERGENCY MANAGER ROLE IN COMMUNICATING TORNADO WARNINGS 169 Figure 6. CASA could aid in spotter deployment and risk assessment by providing high resolution, low level wind data. (a) Composite reflectivity data showing supercells observed by two of the radars in the CASA network with overlapping coverage. (b) A zoomed in view of CASA multi-doppler data showing rotation at the tip of an appendage feature indicating risk of tornadic development. Image courtesy of V. Chandrasekar, Colorado State University. to warn the public are not necessarily dictated by actions taken by the NWS. Only 60% of respondents indicated they always warn the public after the NWS first issues a tornado warning. During a focus group one EM was specifically asked to detail his warning decision after the NWS first issues a warning. He replied: No, I do not send out warnings automatically just because I m included in the warning area. Some jurisdictions have that as a policy, we do not. I consider warning areas, but I also want to make sure there s an imminent threat because we found that if you put out too many warnings, people become complacent, and also if you put out a warning too early, then they don t react in the way that we want them to. Emergency managers were also asked if they will warn their jurisdiction if the NWS has not yet issued a tornado warning. Sixty-seven percent of survey respondents said they would warn their jurisdiction before the NWS issues an official warning. During a focus group session, an EM said he would because, If I can see something, if I ve got eyes on something... we will always err on the side of caution. Therefore, issuing warnings is not an automatic decision. Many EMs will exercise their own judgment in the warning process and will not just wait for an official warning issued from the NWS. In the survey, EMs were asked what the ideal time is to warn the public about an impending tornado threat. Free text responses ranged from 10 to 120 min. Some of the responses included ranges. When these responses were re-coded to the mid-range value (e.g min was recoded to 22.5 min), the median ideal warning time was 23 min. Currently, the national average for tornado warning lead time is about 14 min (NWS, 2009c). The Copyright 2010 Royal Meteorological Society same question was posed to focus group participants who generally agreed 20 min is the ideal lead time for issuing a tornado warning. An EM in Oklahoma noted, 20 minutes would be really nice... We can do what we need to do. If you re not going to do what you need to do in 20 min, forget it. Other EMs agreed saying too much lead time may result in the message to the public losing its emergency status. This, in turn, could lead some people to delay taking protective action or to even increase their exposure by, for example, trying to return to their homes instead of sheltering in place. Once the decision is made to warn the public of a tornado threat, EMs reported that outdoor warning sirens are the primary method used to warn the public, followed by NOAA weather radios (Figure 7). Focus groups were comprised of rural jurisdictions with a single siren, as well as urban jurisdictions with over 100 sirens and every size of community in between. A primary concern with sirens is that they are outdoor warning devices and are not meant to be heard indoors. So while the public expects to have sirens in their communities, EMs also promote the use of NOAA weather radios as a source to receive official warnings. While the NWS is the agency responsible for disseminating a warning via NOAA weather radio, EMs rely on this technology to deliver the NWS warning message. During a focus group session, an EM said he actively encourages the community to buy weather radios: We really promote those because that gets to people regardless of whether they are within earshot of the outdoor warning siren or not. Emergency managers were surveyed to see if they could warn by sub-region (meaning the ability to warn one region of a jurisdiction and not another). Results Meteorol. Appl. 17: (2010)

8 170 C. E. LEAGUE ET AL. Figure 7. Percentage of EMs self-reported sources used to disseminate warnings to the public (n = 43). found that 55% have the ability to warn by sub-region. However, those who have the capability to warn by sub-region do not always use it. The decision not to warn by sub-region may be influenced by an emergency manager s approach to risk. One focus group participant was risk averse, and indicated he will warn according to the hazard, and not according to vulnerability to the hazard. So if one school is going to be warned, all schools are going to be warned. Another EM said, If we sound the sirens, it s for everybody. Some EMs perceive there is a public expectation to be warned. At the same time, some EMs are also concerned about over-warning the public which they believe will disincentivise the public from taking protective actions. Some county EMs said during a focus group that they prefer to use television, radio and cable override because they can tailor their message to exactly what areas are an issue and not over-warn. Unfortunately this method only works if people have their televisions on. One EM had an issue with her city limits being in one county but the actual city spanning across two counties. The two counties are under jurisdiction of two separate weather forecasting offices. There are three sirens for the town with no sub-regional capabilities. The result is that her city receives warnings for both counties, even though her city may not be in the immediate threat area, and the public is over-warned in her opinion. Another concern with sirens is that in some areas sirens can mean multiple things, so people may think an alarm may mean a hazardous materials, flood, hail, or tornado warning. A focus group participant noted: Our sirens have the capability where they can alert for tornadoes... high winds, chemical spills... they have different tones. But in our area, we do not do that because of the confusion that it can emit from the sirens... We sound them for tornadoes, not high winds. Only 16% of the respondents reported using a reverse emergency call-out system, such as Reverse 911, Code Red or NIXLE. This system sends out text or voice alerts to subscribers within a specified warning area which could reduce over-warning the public. Emergency managers in smaller jurisdictions are using this type of warning system. However, an EM from a larger jurisdiction noted during a focus group that he does not use this type of service because of the quick-onset nature of tornadoes. Distributing a message could take hours for larger cities, but the average lead-time for a tornado warningis14min. Communicating a tornado warning to the public is filled with the uncertainty of when, where or if a tornado will hit. CASA s high resolution data may help with public warnings by pinpointing the threat and providing a more geographically specific warning area than currently exists. Sirens are the primary method emergency managers use to warn the public of tornadoes. Of the EMs who have the capability to warn by subregion, many do not use this function, primarily because they are risk averse or because their jurisdiction expects to hear sirens. Smaller jurisdictions are also using reverse emergency call-out systems which are conducive to warning by sub-region. With the ability to provide better detection of low-level rotation at greater spatial specificity and resolution, CASA radars may have the potential to increase the confidence level of EMs in their decision-making process to warn by subregion, which could reduce over-warning the public. 4. Conclusion and Future Research Opportunities Tornadoes are one of the most dangerous severe weather events occurring in the United States, threatening lives and causing extensive damage to property. Communicating risk is not a linear process, or as simple as just pushing a button. Rather, it is a complex, interactive process involving the sending and receiving of messages, threat sensing and assessment leading to the production of

9 EMERGENCY MANAGER ROLE IN COMMUNICATING TORNADO WARNINGS 171 public messages regarding environmental hazards (Reynolds and Seeger, 2005). This process is based on uncertain information, and even getting a timely warning out to the public is not a guarantee of adequate and timely public response. Reducing impacts caused by tornadoes requires a combination of better detection and a better understanding of the warning process and of public response to tornado events. Advances in new radar technology may not automatically translate into better emergency manager warning decisions if this is not taken into account. It is for this reason that CASA is incorporating social science research into the DCAS end-to-end system design. While results presented may not be representative of all emergency managers, our findings are still important in presenting a general illustration of the EM communication and warning process. Results help to understand how emergency managers receive weather information, interpret the information, verify the information and ultimately make the decision to warn the public of a tornado threat. These decisions are largely made under conditions of uncertainty. Results show EMs rely on various sources of weather information at different times during the day. EMs are generally trained in interpreting radar data and they use additional assets such as storm spotters in the verification of weather events before communicating a warning to the public. EMs discussed several problems that could increase the uncertainty in their decision-making. These factors include location of the storm based on distance from the closest radar (NEXRAD hole), and safely deploying spotters during night time and rain-wrapped events when they have trouble discerning storm features. CASA data may help reduce these sources of uncertainty in threat assessment by providing radar data at smaller spatial and temporal scales. Furthermore, CASAs high resolution data with 1 min updates could aid in the deployment of spotters and keep them safe in the field, as well as aid in decision-making during night time or rain-wrapped events. The sample generally represents end-users who are fairly sophisticated users of weather information. There are also emergency managers who lack the technological, economical and/or social resources to support their decision-making needs (Donner, 2008). When deploying new radar technology, considerations must be made of the needs of both sophisticated and non-sophisticated users of weather information in terms of access, resources, support and training. Furthermore, some jurisdictions lack the resources to install siren systems with sub-regional warning capabilities. While CASA s high temporal and resolution data has the potential to reduce warning areas and provide longer lead time for warnings, technological and socioeconomic constraints of the end-user must be taken into consideration in order to incorporate this new technology into current warning processes. Further research should address what impact narrowing warning areas as well as providing longer lead times has on the public response to tornado warnings. Emergency managers in Oklahoma tend to have more training and tailored weather resources for tornadic activity than in the rest of the United States. To understand the diversity of threat assessment and warning processes of EMs outside of Oklahoma, continued post-event research is needed with EMs from other locations in order to obtain a better understanding of different emergency management structures and needs. Successful implementation of new technology must also be measured by the degree to which a positive societal response to hazardous weather is achieved. An integrated warning system (Doswell et al., 1999) involves the media and forecasters in the warning process, leading to a public response. While it is important to understand the role of EMs in the integrated warning system, future research should also consider the role of the media, private and NWS forecasters has on communicating warnings, and how people respond to short-fused warnings. Emergency managers addressed their concern for both over and under warning the public. Future research should address this issue to determine whether false alarms are really a problem in the public eye. There is a need to understand how people interpret uncertainty in their everyday experience with weather and how uncertainty affects the decisions they need to make. Acknowledgements This work was supported in part by the Engineering Research Centers Program of the National Science Foundation under NSF Cooperative Agreement EEC Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of the National Science Foundation. The authors thank the emergency managers who participated in the study. The authors would also like to recognize the valuable assistance of David Westbrook and Dr Sanghun Lim with this study. References AMS Council Tornado preparedness and safety. Bulletin of the American Meteorological Society 81: Bass EJ, Baumgart LA, Philips B, Kloesel K, Dougherty K, Rodríguez H, Díaz W, Donner W, Santos J, Zink M Incorporating emergency management needs in the development of weather radar networks. Journal of Emergency Management 7(1): Baumgart LA, Bass EJ, Philips B, Kloesel K Emergency management decision-making during severe weather. 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