warnings

Tornado Risks: Perceptions and Realities

A session spotlight from the 31st Conference on Severe Local Storms

By Katie Pflaumer, AMS Staff

The session “Perception and Risk Associated with Severe Weather” at the 31st Conference on Severe Local Storms highlighted the interactions between severe weather and societal impacts. Here are a few takeaways.

Tornado impacts are increasing across the United States–despite variation in where tornadoes hit. A presentation by Stephen Strader (Villanova University) highlighted the importance of considering all factors to understand tornado impacts, not just climate. Using 40 years of observational data, plus a statistical model depicting changes in societal factors, researchers found that increased housing and population growth in tornado-prone areas is a key driver of increased tornado damage/human risk. 

While the number of days with tornadoes is trending down in the U.S. Southern Plains and trending upward in the mid-South; the likelihood of tornado damage has increased in both regions due to increased human occupation. However, the combination of tornado increases with population growth and spread has tripled tornado impact potential in the mid-South since 1980, surpassing the Southern Plains. Strader noted that stricter enforcement of building codes, investments in tornado shelters and safe rooms, and public education could help mitigate tornado damages–if scientists can get across the message that human factors matter.


“We have to get away from this idea that climate change is a cause of a disaster … climate change is a contributor to a disaster, not a cause. [Disaster] is inherently linked to societal factors. … With environmental changes and exposure changes/housing growth, you see an increasingly disaster-prone society.”

—Stephen Strader

Graphic from: Strader, S.M., Gensini, V.A., Ashley, W.S., and A.N. Wagner (2024) “Changing Tornado Environments Vs. Changing Societal Vulnerability and Exposure.” (Poster presented at 31st Conference on Severe Local Storms, October 21.) Originally from Strader et al. (2024), “Changes in tornado risk and societal vulnerability leading to greater tornado impact potential.” NPJ Natural Hazards, 19 June. https://doi.org/10.1038/s44304-024-00019-6

Wireless Emergency Alerts are critical—and confusing—for Spanish speakers in the U.S. Southeast. A study presented by Joseph Trujillo-Falcón (University of Illinois) found that Spanish-language wireless emergency alerts (WEAs, phone notifications about severe weather) from the National Weather Service are crucial safety tools. For some tornado survivors in Kentucky, for example, the WEA had been their only trigger to get to safety. In-depth conversations with 27 Spanish speakers from across the U.S. found that WEAs were highly respected and useful, yet needed some redesign to avoid confusion. For example, the Spanish translation of the NWS acronym (SNM) called to mind medical conditions or kink. The word “proyectiles” (projectiles), used to warn about airborne debris, evoked war zone imagery rather than weather. Using the word “aviso” for “warning” struck many as less urgent than the term “alerta.” In addition, 360-word warnings (versus those of 90 words or less) helped readers better understand what was going on and what to do in response. This was especially important for people who hadn’t encountered a tornado in their country of origin. Direct links to information and instructions on how and where to shelter were also seen as key, especially in areas with many mobile or manufactured homes.

“The information source that I take most seriously as a recently arrived immigrant are WEAs. Since everyone gets it at the same time, if one ignores it, the other reads it.”

—Gabriela, Venezuelan immigrant who has limited English proficiency (Trujillo-Falcón 2024).

People want different forecast information as a threat evolves. A study presented by Makenzie Krocak (National Severe Storms Laboratory) analyzed data from the Severe Weather and Society survey to determine what information members of the public want and need at different times in relation to weather threats. They found that respondents’ priorities changed over time. In longer time frames (e.g., three days in advance) survey respondents overwhelmingly ranked location information and event probability as the most valuable information; people wanted to know, ‘Should I prepare for severe weather to occur in my area?’ A day to an hour in advance, people wanted to know about the timing of the event, as well as its potential severity. In the warning time frame (60 minutes or less) their desire for information about potential impacts and necessary protective actions increased.

For additional insight, the researchers painstakingly categorized, geo-located, and analyzed 9000+ social media comments from the National Weather Service Facebook and Twitter/X accounts before and after severe weather events. A poster presented by undergraduate student Emily Allen (University of Louisiana Monroe) delved into this side of the equation.

Emily Allen with her poster, “Assessing Public Information Needs Leading Up to Severe Weather Events.” (E.A. Allen and M. Krocak, 2024)

Three days out from an event, commenters largely asked about the chance of an event happening, but for nearer time frames, location became the dominant question—i.e., ‘Will this hit my specific area?’ Krocak emphasized the need to include very clear landmarks in warning graphics to help people find their location. She also noted that certain groups still require information about protective actions to take—especially those with the least experience dealing with a particular hazard.

Making severe weather products usable and understandable. Two presentations dealt with public perceptions of evolving probabilistic weather forecast information—that is, communicating changes in severe weather risks across time and geography. 

Christopher Wirz (NSF NCAR) presented preliminary results of a study about public perceptions of evolving probabilistic tornado forecasts and warnings. On average, respondents’ sense of risk was about the same as for a deterministic (e.g., warning vs no-warning) forecast; most were likely to be on high alert during a tornado warning in any case, and not underestimate their risk. However, there were differences in how participants responded based on where they were located relative to a given warning polygon. For example, some felt they were in more danger if they were ‘in front’ of the warning polygon, despite the graphics showing equal tornado risk in other directions. Warn-on forecasts—alerts issued when a significant risk is predicted, often long before a tornado is detected by radar—were seen as less actionable by some, but others appreciated knowing to ‘keep an eye out.’ Overall, the study found that members of the public don’t take probabilistic information at face value—rather, they interpret it based on context, including existing local knowledge and other warning products they encounter. In addition, for half of the respondents, level of trust in a forecast didn’t change when they received more/updated information, because trust was instead based on how much they trusted the source of the forecast.

Kristin Calhoun (NOAA National Severe Storms Laboratory) presented about new products and communications that are in development to help NWS forecasters and emergency managers use storm-based probabilistic hazard information (PHI) in the severe weather watch-warning timeframe. These included PHI tools layered with threats-in-motion (TIM) information, in which warning polygons are moved (and removed) with the motion of the storm, helping downstream areas prepare sooner and allowing those for whom danger has passed to redeploy their resources more strategically; potential new protocols for the NOAA/NWS Storm Prediction Center, rather than local weather forecast offices, to add or remove an area from a watch/warning once the threat has passed; a blended PHI plus warn-on forecast product that can help emergency managers plan better by seeing storms in motion along with trends in likelihood and potential impact; and a new product based on SPC’s ‘Mesoscale Discussions,’ created by local NWS forecasters and called ‘Local Discussions,’ with an increased focus on potential impacts, timing, and location of hazards versus highly technical information.

Photo: National Severe Storms Laboratory, Watch-to-Warning Experiment.

Social pressure may impact campus tornado safety. Alicia Klees (University of Illinois at Urbana-Champaign) presented work conducted largely by undergraduate student Kyla Wolski that has implications for student safety. The University of Illinois’s Illini-Alert system warns students when tornado threats are approaching; most students are aware of the alerts, and most have experienced a tornado warning before. Students were asked in a survey what they would do if they were in a vulnerable location—such as a fourth-floor classroom with glass windows—and received a tornado warning. 75% said they would change their location to seek shelter. However, when a hypothetical professor kept teaching through a tornado warning (as some faculty reportedly did during the last real tornado warning on campus), 22% of students who had planned to seek shelter said they would probably stay in class. These students said they trusted the professor’s judgment—yet professors do not receive extensive formal training on tornado safety. Klees recalled an anecdote from a student in which one faculty member remarked, “I don’t hear the sirens anymore, so it’s fine.”

In addition, most students did not view tornadoes as a major risk, and most were unaware that tornadoes could happen at any time of year. Klees identified future collaborations with Emergency Management to survey faculty and TAs on tornado warning response, with the goal of keeping students safe.

If you are registered for the 31st Conference on Severe Local Storms, you can view the full session recording at this link.

About the 31st Conference on Severe Local Storms

The American Meteorological Society’s 31st Conference on Severe Local Storms takes place 21-25 October, 2024, in Virginia Beach, VA, and online. The conference is the premiere gathering for scientists, forecasters, educators, and communicators engaged in all aspects of work related to hazardous deep convective weather phenomena. Attendees present and discuss cutting-edge research regarding the analysis, prediction, communication, and theoretical understanding of the structure and dynamics of severe thunderstorms, including their associated hazards of tornadoes, damaging winds, large hail, lightning, and flash floods. View the conference program here.

Recent Trends in Tropical Cyclone Fatalities in the United States

Satellite photo of Hurricane Gonzalo (a ball of swirling clouds) over the Atlantic near Puerto Rico; other larger cloud systems are seen in the upper part of the photo, eclipsed by the curvature of the Earth in the top right. Photo taken by GOES East satellite at 1445Z on October 14, 2014. Photo credit: NOAA.

New data from the past ten years reveal increased prominence of freshwater floods and indirect fatalities in hurricane deaths

Guest post by Dr. Michael Brennan, Director, National Hurricane Center; Daniel Brown, Warning Coordination Meteorologist, National Hurricane Center; and Leah Pope, Hydrologist, Northwest River Forecast Center

The National Hurricane Center’s mission to “save lives and mitigate property loss” is not just achieved by issuing effective watches, warnings, and forecasts of tropical cyclones. We also spend a large portion of the “offseason” educating the public, emergency managers, and our media partners about the risks that tropical cyclones (TCs), including hurricanes, pose to life and property in the United States. Those include natural hazards such as storm surge, wind, and rip currents, and also includes dangerous conditions in the aftermath of a landfalling tropical cyclone, which may lead to “indirect” fatalities. These are deaths which are not directly due to the forces of the storm, but which would not otherwise have occurred. NHC routinely compiles and assesses TC-related information through vehicles such as our Tropical Cyclone Reports (TCRs). Data from the most recent decade reveal that fatality trends may be changing.  

Note:  The fatality data presented here do not include any fatalities from Hurricane Maria in Puerto Rico, since there was no specific, definitive cause provided for those deaths.

Direct Fatalities

Aerial photo of a peninsula/barrier island that has been breached by a storm surge. Sand, buildings, and other structures have been washed away or damaged, including visible broken lines of sandbags, a damaged bridge, damaged trees, and obliterated buildings; only one house appears to still be standing.
Storm surge damage from Hurricane Ike, Bolivar Peninsula, Texas, 2008. Photo credit: NOAA.

Previous studies by Rappaport (2014) and Rappaport and Blanchard (2016) summarized direct and indirect fatality data from Atlantic basin tropical cyclones in the United States for the 50-year period 1963–2012. During that period, nearly 9 out of 10 tropical cyclone-related direct deaths in the United States were due to water. Storm surge was responsible for nearly half (49%) of the direct deaths, and over one-quarter (27%) were due to rainfall-induced freshwater flooding.  

In response, the National Weather Service (NWS) and NHC worked to improve outreach, education, and communication of storm surge and rainfall hazards. We introduced new real-time storm surge maps in 2014, and in 2017 introduced a storm surge watch/warning that highlights the risk of life-threatening storm surge inundation. 

New Data Suggest Changing Trends

Since 2012, the United States has experienced 21 hurricane landfalls, including 8 major hurricanes, and more than 20 tropical storm landfalls. Eighteen of these hurricane landfalls, including all of the major hurricanes, occurred during 2017–22 after a relatively quiet period. Given the significant number of tropical cyclone landfalls in recent years, and increased deployment of warnings around the storm surge hazard, NHC examined and compared fatality data from the most recent 10-year period (2013–22) to the earlier studies.

Hazard % of direct fatalities from this cause
(1963–2012)		% of direct fatalities from this cause
(2013–2022)
Storm Surge49%11%
Freshwater Flooding27%57%
Wind8%12%
Surf/Rip Currents6%15%
Offshore Marine Incidents6%3%
Tornadoes3%2%
Other1%1%
Note: Due to rounding, numbers may not add up to 100%.

During the most recent 10-year period in the United States, about 57% of direct tropical cyclone deaths were due to drowning from freshwater (rainfall) flooding. Surf and rip current fatalities have become an increasing threat, making up about 15% of direct fatalities in the past decade. These fatalities often occur one or two at a time from distant storms hundreds of miles offshore. Florida, North Carolina, and New Jersey experienced the highest number of TC-related surf and rip current fatalities. Storm surge and wind-related deaths account for 11% and 12% of the direct fatalities, respectively.  

Every hurricane is different, however. Hurricane Harvey in 2017 had the largest number of direct deaths—68, 65 of which were due to freshwater flooding in Texas—in the past decade. Hurricane Ian (2022) was the second deadliest with 66 direct fatalities, 41 of which were due to storm surge in Florida. More than 65% of those who died from direct causes were men, with about 60% of the victims over the age of 60.

Indirect Causes

Image of a boat stranded on land, leaning against a wind-destroyed structure and a power line, amid other debris, including destroyed buildings and cars. Three people stand next to the boat observing the damage.
Aftermath of Hurricane Ike in Galveston, Texas, 2008. Photo credit: NOAA.

The recent study revealed that over the past 10 years there has been nearly an equal number of indirect deaths as direct fatalities. Indirect fatalities are due to a wide range of causes, including traffic accidents (16%), preparation/cleanup accidents (15%), carbon monoxide poisoning (12%), lack of medical care (11%), power problem/electrocution (11%), post-storm heat deaths (9%), unknown causes (9%), cardiac-related deaths (7%), and evacuation-related deaths (5%). 

The largest number of indirect deaths in the past decade occurred in association with Hurricanes Ian (90), Irma (82), Michael (43), Harvey (35), and Laura (34). Most (75%) of the indirect deaths are associated with major hurricane landfalls, which leave communities very vulnerable and often with long-duration, widespread power outages. More than half (57%) of the victims were over the age of 60. Younger victims tended to die in vehicle accidents; for older victims, medical-related issues, heat, evacuation, and other accidents were more likely causes of death.

Improving Warnings and Public Understanding

The results of these most recent studies have led the NWS and NHC to increase messaging on the hazards and causes of both direct and indirect fatalities. We continue to highlight rainfall flooding and storm surge risk through the Weather Prediction Center’s Excessive Rainfall Outlook, Flood Warnings from local NWS offices, and increased emphasis on the Storm Surge Warning. These warnings are the loudest “bells” that the NWS can ring during life-threatening flooding. We encourage our media and emergency management partners to work with us to encourage timely public response and personal preparedness ahead of these threats. 

Additionally, with the increased percentage of rip current fatalities associated with high surf and swells from distant hurricanes, the NWS has created new infographics to explain this deadly beach hazard, and is working on graphics to better highlight the threat in real time.

During the highly impactful 2020 hurricane season in the United States, there were more fatalities associated with carbon monoxide poisoning from the improper use of generators than there were from storm surge. After that season, NHC and the NWS developed infographics and worked with media and emergency management partners to highlight that threat. While it is difficult to determine the effectiveness of that messaging, it is encouraging to know that there were no carbon monoxide related-fatalities in the aftermath of Hurricane Ian in 2022 in Florida, despite its devastating impacts and widespread power outages in that state.   

NHC relies on relationships with media, emergency management partners, and the entire weather enterprise to help reach the public before, during, and after tropical cyclone threats. These efforts undoubtedly increase awareness, encourage preparation, and save lives. We hope to continue to improve our messaging and understanding of the threats and causes of injuries and fatalities to better meet our collective mission.  

Visit the National Hurricane Center online.

Header photo: Hurricane Gonzalo in the Atlantic. Photo taken by GOES East satellite at 1445Z on October 14, 2014. Photo credit: NOAA.

This post was invited based on a presentation given by Dr. Brennan at the 50th Conference on Broadcast Meteorology, which took place in Phoenix, Arizona, June 21–23, 2023. The conference was organized by the American Meteorological Society Board on Broadcast Meteorology and chaired by Danielle Breezy and Vanessa Alonso.

Eulerian Weather, Lagrangian Lives

by Alan E. Stewart, University of Georgia

It is clear that Covid-19 will be with us for a while. So will the weather, however. We’ve been through flooding in Michigan in mid-May; an outbreak of 140 tornadoes from Texas to Maryland in April; a deadly and destructive derecho in Iowa; hurricane landfalls in Louisiana, Alabama, and Florida; and massive wildfires in the West. In other words, the weather, as always, just is—it exists and occurs as a series of events that intertwine with the activities and challenges of our daily lives. Here, I would like to borrow from dynamic meteorology and apply the concepts of the Eulerian and Lagrangian perspectives to discuss our experiential journeys through the weather and Covid-19. I also will query what this means for how we cope when severe weather threatens us during this pandemic.

From the Eulerian perspective, we depict the current weather or make a forecast for a given space (county warning area, city, state, region) for a time (6 hours, 12 hours, and so on). We concern ourselves with what will occur inside the grid boxes of a model—what is the flux of weather into and out of the area? Similarly, when we look out of the windows of our life-spaces we see and experience the weather. And what is so striking about what we see is that most of the time the weather seems within its usual seasonal limits—climatologically speaking. The weather is often pleasant. It seems not to have gotten the message about Covid-19.

How could it? The weather just is. Some people have told me that during the pandemic, the closures, and the quarantines, the weather is about the only thing that has remained normal in their lives—and this has provided some degree of comfort. But with a wildfire or a hurricane, this can change quickly. Some of the same states that are threatened by hurricane landfall already have been ravaged by Covid-19.

We can think of peoples’ paths through the meteorological and nonmeteorological events in their lives with the Lagrangian perspective—metaphorically speaking. Life is a journey, a narrative, a path or a force that moves forward in time; sometimes the trajectory changes unexpectedly. The Lagrangian perspective involves the accumulated experiences of the weather through the eyes of the perceivers— individual people. Such Lagrangian living with or “under” the weather builds a corpus of weather experiences that subtly or sometimes significantly changes peoples’ subsequent responses to the weather . All of us are, to varying extents, products of what we have experienced, including the Covid-19 pandemic. So many people—in Michigan, Iowa, California, Louisiana, and elsewhere—have experienced life with both Covid-19 and disaster and displacement.

In dynamic meteorology we learn to use both the Eulerian and Lagrangian perspectives; we segue between the two to build a fuller understanding of the atmosphere. What might we learn and what questions arise when we juxtapose my uses of these perspectives? These are timely questions to consider as we deal with hurricanes, winter storms, and other weather threats during the Covid-19 pandemic.

Trust of Message Sources: During the Covid-19 pandemic, different state and federal agencies often have issued confusing, sometimes contradictory reports and recommendations about the virus. How have peoples’ experiences of this messaging affected the ways that they may receive and act upon forecasts, watches, and warnings for severe/extreme weather? How might weather-related messages from local emergency managers or health departments be received? To what extent has the trust in the weather enterprise been affected by pandemic-related messaging?

Risk Perception and Tolerance: People have dealt with multiple risks thus far during the pandemic: health, economic/financial, social, and psychological, among others. Have the experiences of these risks affected how people perceive additional risks from thunderstorms, tornadoes, floods, and hurricanes? Because people may have successfully survived an infection with Covid-19, does this affect how they perceive their risks to natural hazards? Do some people feel lucky? Because people may be more desperate for work or to keep a job, might they take additional risks to do their jobs during bad weather? Might some businesses take extra risks in bad weather to build a competitive advantage—to make up for past losses?

Preparation: As word of the pandemic spread, people in many places stocked up on consumables for daily living, leading to shortages of some items. Given how the pandemic has unfolded in different parts of the country, are people still prepared? Have they exhausted those supplies and are people fatigued from stocking up? Are suppliers ready for further waves of Covid-19 and/or a major hurricane landfall? Has stocking up and preparing made people more ready for severe weather? Is there a new appreciation for being prepared for the unexpected?

Sheltering in Place: Some severe weather events involve sheltering in place. Given the extensive sheltering in many places in the spring because of Covid-19, would some prefer to shelter in place rather than risk Covid-19 exposure elsewhere? Alternatively, would some be less likely to shelter in place because they are fatigued from it?

Evacuation Planning: Important questions involve what happens when evacuations are necessary: For example, how can the spread of Covid-19 infection be limited? Are separate shelters needed for those who are infected? How does social distancing work in the close quarters of a shelter? Are more shelters needed? Do the existing shelters have a supply of face masks and other personal protective equipment?

Interdisciplinary social and atmospheric science points to an ever-motivating realization: Often it is not simply a matter of providing a timely and accurate forecast, but it is what people do with the information they have that affects the outcomes. This is unsettling because it is often out of the direct control of the weather enterprise—much as epidemiologists and physicians cannot control how people deal with the risks of Covid-19. Efforts to communicate effectively, educate, and persuade stakeholders about the weather take on great importance. Forecasts and warnings are absorbed by people who have experienced the varying and cumulative effects of Covid-19. Being mindful of this reality may help us to better prepare people and communities.

 

 

 

A Question for the Experts

There have been many thoughtful questions raised throughout this weekend’s AMS Student Conference, but one question posed at the communications breakout session on Saturday proved particularly challenging for the panelists. A student asked, “How do you educate the public that doesn’t have access to television or social media? How do we educate the homeless about severe weather events?”
Here were the responses from the panelists:
Marshall Shepherd, Univ. of Georgia: I think you’re hitting on a key question. The homeless question…that’s tough. These are the people who aren’t watching, necessarily. That really involves grassroots efforts. TV stations can be involved in galvanizing and organizing. So, for example, I teach a class at the University of Georgia on urban climate, and one of the projects I ask students to do is look at tornado sirens in the Athens/Clark County region. One of the things we found was that the way the tornado sirens were distributed, there were significant parts of the population—particularly those who were underserved or lower income—who didn’t even have sirens where they lived.
So I think there’s a whole notion of increased social sciences and environmental justice and all types of issues that we all have to be aware of and address.  I don’t know the answer to that question you asked, and I think there’s an opportunity.
Ginger Zee, ABC News: I’ve done four stories on that same thing of the sirens, because there’s no federal law, state law, no county law in any state that says there has to be one. I grew up in Michigan and we had them in every single town. It’s amazing to me that there are places that don’t have them, especially in places that really need them but don’t. Requiring outdoor warning systems—I don’t know if that’s going to happen; it’s not going to be funded.
I think the community outreach part is probably your best bet. You guys remember in Virginia this year, there was a camp with a bunch of kids outdoors and a long line of storms on the ground for three hours. It’s amazing to me that they still didn’t have warning. That can’t go on.  There was one kid who died. That shouldn’t have happened, because once they got indoors they were safe inside. If that was a fire and they didn’t have a smoke alarms, we would not be having the same discussion. They would have been sued like crazy.
Weather has grown…our ability to forecast has grown and now the whole policy part of it has to catch up. I think that will take time.
Keli Pirtle, NOAA: The National Weather Service works with local emergency managers to help prepare communities through the Storm Ready program.  I would hope that a shelter, like a homeless shelter, would have a NOAA Weather Radio. That’s a hope more than a reality, I’m afraid.  We can encourage people—churches, nursing homes, schools—to have multiple ways to receive information, to have a plan. A homeless person on the street, they’re in touch with others. I would hope the network on the street would get them the information, but it’s certainly an area where we desperately need to improve.
Jorge Torres, KOB-TV: And I agree with that. At our station, we’re partners with the Red Cross, and with the Roadrunner Food Bank of New Mexico, which helps feed the hungry because New Mexico is, I believe, the number one state in the country for childhood hunger. So we do have outreach programs with the lower-income communities. But that’s not in the form of weather [information] mostly, it’s in the form of talking to them. I do think you bring up a good point that those who don’t watch us, can’t watch us. They’re the ones who deal with the elements much more—the homeless especially—than the rest of us because we have a roof over our head and they don’t.

NWS Experiment Chooses Words To Improve Warnings

The National Weather Service recently announced plans to expand the use of its experimental impact-based storm warnings to include all 38 branches of the NWS Central Region. The warnings go beyond a simple explanation of a storm’s strength by communicating specific effects that the storm could cause, using descriptions like “major house and building damage likely and complete destruction possible,” “major power outages in path of tornado highly likely,” and “complete destruction of vehicles likely.” The warnings were implemented last year in Kansas and Missouri, and officials believe they helped prevent fatalities during a tornado outbreak in Kansas last April 14. The effectiveness of the warnings last year will be examined in more depth in a presentation at the Second AMS Conference on Weather Warnings and Communication, which will be held this June in Nashville (in concert with the 41st Conference on Broadcast Meteorology) .
These new warnings are just one example of the advances made in communicating dangerous weather events to the public, and the Nashville conference will examine a number of methods, including the use of social media and mobile apps. The meeting will also look at how the general public responds to various types of warnings, and explore both old and new technologies in warning systems. The full program for the conference can be found here.
Clarity of communication is a key to the impact-based warnings. According to this story in the Wichita Eagle, emergency officials are praising the vernacular of the new warnings. Michael Hudson, chief operations officer for the NWS Central Region headquarters in Kansas City, Missouri, noted that “emergency managers liked the extra information that was in the warnings–the information that got to the magnitude of the weather.” In specific reference to the intense tornado in Sedgwick County, Kansas, last April, that county’s emergency management director, Randy Duncan, felt the language in the impact-based warnings “helped to convey how serious the situation was, and the fact that we didn’t have any fatalities means–at least in my mind–that people in Wichita paid attention.”
The expanded use of the warnings this year will include some minor revisions resulting from some lessons learned in last year’s experiment. One change is the new use of the word “considerable” instead of “significant,” because “significant” was considered by many users to be too vague. Hudson explained that forecasters are instructed to consider “what you’d tell your wife or husband or children” about the potential threat of a storm.

Read more here: http://www.kansas.com/2013/04/07/2750867/use-of-impact-based-severe-weather.html#storylink=cpy
Read more here: http://www.kansas.com/2013/04/07/2750867/use-of-impact-based-severe-weather.html#storylink=cpy
Read more here: http://www.kansas.com/2013/04/07/2750867/use-of-impact-based-severe-weather.html#storylink=cpy
Read more here: http://www.kansas.com/2013/04/07/2750867/use-of-impact-based-severe-weather.html#storylink=cpy
Read more here: http://www.kansas.com/2013/04/07/2750867/use-of-impact-based-severe-weather.html#storylink=cpy

 

Read more here: http://www.kansas.com/2013/04/07/2750867/use-of-impact-based-severe-weather.html#storylink=cpy
Read more here: http://www.kansas.com/2013/04/07/2750867/use-of-impact-based-severe-weather.html#storylink=cpy

New Warnings, New Words

National Weather Service offices in Missouri and Kansas recently initiated an experiment testing new tornado warnings that combine more specific information with more descriptive language than have been used in the past to describe the potential effects of storms. The experiment is called “Impact Based Warning,” and is meant to bluntly tell residents in the path of tornadoes what could result if they don’t seek shelter. By using phrases such as “complete destruction” and “unsurvivable if shelter not sought below ground,” the NWS is hoping to “better convey the threat and elevate the warning over a more typical warning,” according to Dan Hawblitzel of the Pleasant Hill, Missouri NWS office.
The new alerts got their first big test last weekend when more than 100 twisters were reported in Kansas, Oklahoma, Nebraska, and Iowa. While the NWS’s Storm Prediction Center issued a warning of possible life-threatening storms in several midwestern states days before they touched down, in Kansas the words used in the new alerts were particularly trenchant: “You could be killed if not underground or in a tornado shelter. Many well-built homes and businesses will be completely swept from their foundations.” And the warnings seem to have worked. Despite the large number of storms, only six people were killed—all in an overnight tornado that hit Woodward, Oklahoma. In Wichita, Kansas, a twister tore through a mobile-home park during nighttime hours, but there were no fatalities.
The Impact Based Warning experiment was developed by the NWS in consultation with social scientists. Along with the new vernacular, it includes some key additions to regular tornado warnings, including information that identifies the hazard (hail, winds, tornado, etc.), indicates whether the hazard has been spotted by radar or by people on the ground, and describes potential effects of the hazard (loss of life, damage to trees or buildings, etc.). The warnings can be used not only for tornadoes, but also to signify life- or property-threatening thunderstorms. The experiment is scheduled to run through the end of November, at which point it will be evaluated and considered for more widespread use.
The initiative comes  just one year after tornadoes killed more than 500 people in the United States—the deadliest season in almost 60 years. The 2011 year in tornadoes is examined in the new AMS book, Deadly Season: Analysis of the 2011 Tornado Outbreaks, by Kevin M. Simmons and Daniel Sutter. The book is a follow-up to the authors’ Economic and Societal Impacts of Tornadoes, published by AMS in 2011. The new title looks at possible factors contributing to the outcomes of 2011 tornado outbreaks, including assessments of Doppler radar, storm warning systems. and early recovery efforts. Both books can be purchased here.