Thoughts about tornadoes and camping safety after the Iowa tragedy on 11 June 2008


Chuck Doswell

Posted: 18 June 2008 Updated: 06 October 2008: added a personal account by one of the Scout leaders at the Little Sioux Scout Ranch (LSSR)

As is typical, the following represent my opinions after the loss of four Boy Scouts at the Little Sioux Scout Ranch campground in western Iowa on 11 June 2008. If you wish to comment on or dispute my views, feel free to email me at (use the hyperlink or change the # to @). If you're not willing to have your opinions added to this webpage, however, don't waste my time and yours.

1. Introduction

In the wake of a tragedy like the events of 11 June 2008 at the Little Sioux Scout Ranch, there are some natural human reactions. One is to seek to establish why this happened. Another is to try to pin the blame on someone, often taking the form of lawsuits for negligence. I make no claim to have conducted any sort of investigation of the event. I know that the four boys were killed when a bunkhouse chimney fell on them, after taking shelter in the bunkhouse. It's evident that the camp was aware of the tornado approaching them and steps were taken to get the campers to shelter, but there was no adequate shelter anywhere in the campground and by the time it was evident that the tornado would come into the camp, there was no time to evacuate. Thus, it might seem logical to some people that someone was at fault for these fatalities. With the benefit of 20/20 hindsight, it's clear that when the tornado watch was issued that included the campground, if evacuation had begun then, the campers would not have been there when the tornado hit. But how many times have tornado watches been issued that included the campground but no tornadoes hit? Evacuation on issuance of a watch is simply not a realistic option. So is it the adult campground leadership who is to blame? Or is it the Boy Scouts of America and the campground operators, for having no adequate shelter in place? I want to explore this incident, in part because I have a history of being associated with preparedness for severe weather events in association with hiking and camping, and in part because this incident is a microcosm of the larger issue that people in this nation (and around the world) have regarding tornado preparedness.


2. Tornado occurrences in the USA and elsewhere

One thing that becomes abundantly clear to anyone who studies tornadoes in depth is that they are rare events, even here at the peak threat area anywhere in the world.

Map of violent tornado frequencies, showing south-central Oklahoma as the peak frequency, with a value exceeding 50 days on which one or more violent tornadoes occurred per thousand years. Provided by the National Severe Storms Laboratory.

As I explained in a discussion of tornado probabilities, the odds of experiencing the violent winds of a violent tornado (F4 or F5 on the Fujita Scale) in any given year are so small as to be virtually negligible. Even if we consider the strongest winds in a "strong" tornado (F2 or F3 on the Fujita Scale), the odds remain quite low. Of course, the chances of being somewhere in the path of a tornado are larger than the odds of experiencing the worst that a given tornado can produce, but again, these are low probabilities. You could live for 1000 years in central Oklahoma and never even see a tornado, much less find yourself in the path.

On the other hand, a few residents of Moore, Oklahoma, were hit by tornadoes on 04 October 1998, 03 May 1999, and 08 May 2003. Consider the tornado tracks for the Oklahoma City metroplex provided by the Norman office of the National Weather Service:

Map of tornado tracks crossing the OKC metroplex, provided by the Norman office of the NWS

There are places on this map that seem to have been in tornado paths many times, whereas there are different places that seem to have been missed completely during the period of record. What this does not imply is that some places are cursed and others are blessed. From a purely statistical viewpoint, the tracks of tornadoes across the OKC area are essentially random! It's a poorly understood aspect of spatial randomness that clusters and voids are associated with a randomly-occurring process. Random does not mean a uniform distribution. Over a very long period of record, it's possible that these clusters and voids would become less apparent, but given the tornado frequency even here in central Oklahoma, it would take many hundreds, perhaps even thousands of years for that to happen. Even the seemingly long record for the OKC area is in fact a small sample.

There's no known reason that a particular place is hit while nearby locations are spared. There's no known explanation for the clusters and voids in the distribution and an explanation isn't actually needed for such if the process is spatially random. Myths abound that tornadoes avoid certain locations because of a river, or a hill (often including a citation for some Native American legend to that effect). The science of meteorology says that these "anomalies" are nothing more than the manifestation of what amounts to an essentially random process. There might be nonrandom aspects embedded within the data, but we don't have a large enough sample to have confidence in proposing physical explanations for the existing spatial distribution of tornado occurrences.

The large-scale distribution of tornadoes does show broad patterns, as shown above. Those broad patterns are a reflection of the frequency with which the ingredients for tornadic storms are brought together. But for any relatively small area within these broad patterns, the distribution of actual tornadoes is simply random. Trying to make sense out of the distribution shown above for the OKC metroplex is basically hopeless. Every year, the odds of being struck by a tornado are reset - the atmosphere has little memory on time scales as long as a year, so every year starts out with roughly the same odds, but what actually happens in a given year depends on a large, complex set of circumstances controlled (via complex, poorly understood linkages) by the circulation of the atmosphere in that year. Some years have many more (or many fewer) tornadoes than average, so while the average gives a rough sense of what to expect in any given location, the real weather you experience will be determined by the details of how the atmosphere behaves.


2. A basis for predicting tornadoes?

Since the chances for a tornado depend on the atmospheric structure, it's possible to distinguish days with high potential from days with little or no potential for tornadoes, and everywhere in between, but not with absolute certainty, of course. This is what the Storm Prediction Center (SPC) tries to accomplish with its severe weather outlooks. The idea is create an awareness of the daily severe storm and tornado possibilities out for several days. Obviously, the longer the time range of the forecast, the greater the uncertainty. Outlook areas can vary quite a bit, but are typically 100,000 square miles or more. Tornado probabilities somewhere within the outlook area at sometime during the 24-h day have to average at least 2% (= 0.02, or two chances in one hundred) within any circle with a radius of 40 km (~25 miles) surrounding any randomly-chosen point inside the outlook even to mention the possibility of a tornado. For a circle with a radius of 25 miles, the area within such a circle is nearly 2000 square miles, so if there's a 2% chance of one or more tornadoes within the outlook, any particular square mile within the outlook has a probability of having one or more tornadoes within it of about 0.02/2000 = 0.000010 (or about 10 chances in a million!). On most days of the year, of course, the probability of a tornado in any given square mile is much less than this small value! The highest tornado probability ever considered for use in an outlook is about 60%, which translates to 0.6/2000 = 0.00030, or about 300 chances in a million for any particular square mile, still a small number but again much higher than on any randomly-selected day of the year.

When conditions for a potentially tornadic weather event are apparently coming together, the SPC issues a tornado watch (or a severe thunderstorm watch, if the tornado potential is deemed low enough). This implies an increasing probability of a tornado as the time of the event approaches and the conditions seem to warrant an increased potential within an area that is typically around 20-40,000 square miles or so. Within such a watch, the probability of a tornado during the valid time of the watch must be at least 20% or so. Hence, the probability for any given square mile is at least 0.2/30,000 = 0.000007, or about 7 chances in a million. On big days, the probabilities could be up to 90% within the watch, corresponding to about 30 chances in a million for any particular square mile. The primary issue with watches is that they typically cover much smaller areas than outlooks, for shorter time periods (of order 6-h or so), so they amount to a refinement of the outlook. However, if every time a watch was issued, everyone immediately took tornado precautions, the huge majority of the time, those precautions would have been unnecessary. A tornado watch is not intended to trigger specific tornado precaution actions like seeking shelter or evacuating - it's designed to put people into a higher state of preparation for implementing tornado precautions, should weather conditions develop that would justify those actions.

Finally, when either someone sees a tornado developing, or radar indicates a tornado is likely, a tornado warning is issued by the local offices of the National Weather Service (NWS). If you're in a tornado warning, then the probability of experiencing a tornado is at its highest. Probability values for warnings have not officially been developed, but presumably when (or if) they are, the values would be much higher than in an outlook or a watch. Not all tornadoes are warned for, and many warnings are false alarms. This has to be accounted for by the users of this information. The way in which users react to tornado warnings is a personal decision.

So what's the point of all this discussion of probabilities? I want to establish that even here in the most tornado-prone part of the world - the Great Plains - tornadoes are rare events in terms of the area they affect on any given day. Hence, most people will never even see a tornado, much less be in the path of one. But if you consider the entire USA in any given year, the probability of having one or more tornadoes somewhere, sometime, is virtually identical to 100%! When tornadoes occur and have relatively long tracks - say, 20 miles or longer - there's a good chance that some humans will be in their path, although the majority occur in open, rural areas where the impact on humans is minimal. It is also very nearly 100% certain that one or more people will be killed by a tornado in any given year. What I interpret this to mean is that a relatively few people are going to be unlucky enough to be killed by tornadoes every year. Given that most people survive being hit by tornadoes every year, the few to be killed are especially unlucky (or made a poor decision in the situation). In many parts of the USA, tornadoes are sufficiently infrequent that most people believe they don't happen in the area at all! This can be a fatal mistake, as low probability doesn't mean zero probability. But, for the most part, such beliefs are seemingly justified by the absence of tornadoes in their area - most of the time. The infrequency of tornadoes in some parts of the USA leads to what my friend Matt Biddle refers to as the "normalcy bias" - this means that what people have experienced during their lives to date is expected to be valid indefinitely. If they've never experienced a tornado, they never will. But for a few people every year, this misinformed notion is shattered by actual events. The reality is that tornadoes are "normal" virtually everywhere - just less frequent in some places than in others. Sometimes, the atmosphere behaves "abnormally" with respect to people's experience. It's foolish and naive to believe that one's personal experience is representative of what is possible, however improbable, but that's how many people think about such things.

In other parts of the world, the climatological tornado probabilities are generally much lower than in the USA, so in most countries, no one is responsible even for keeping track of tornado occurrences. They have other geophysical hazards that are much more important to them - notably flooding, hail, and windstorms. Again, the bias toward perceived normality is potentially lethal.

The natural world is not perpetually benign - in particular, geophysical hazards occur according to their own rules and timetables. The fact that humans sometimes are tragically affected by such things is irrelevant to the natural processes. Security from geophysical hazards is a dangerous illusion, but for the most part, people can ignore the risks and it will be O.K.


3. The Iowa event in perspective

The tornado that hit the Iowa campground was a strong tornado, not a violent one. But the campground, like most such across the USA, had no tornado shelter offering resistance to a strong or violent tornado. The fact is that most people all over the USA do not have such a shelter. Why not? Primarily because tornadoes occur with such low frequency, that most people have never gone through one. This results in the "normalcy bias" - if something has never happened in your experience, the presumption is that it never will. This is clearly a false sense of security, but it's pervasive around the USA and the world. People tend to believe their experience is representative of everything that possibly could ever happen, but anyone knowing anything about the climatology of tornadoes surely must understand that this is simply untrue. If you've never experienced a tornado, why have a shelter? In fact, why make any preparations at all for a tornado?

From a purely statistical basis, the "normalcy bias" with regard to tornadoes is a relatively good bet. The odds are if you've not yet experienced a tornado, you never will. But you must ask yourself the "Dirty Harry" question: "Do you feel lucky? Well, do you, punk?" Because the fact is that someone is going to be in the path of a tornado every year. Why you? Well, the question really is, why not you? If you live in the USA somewhere east of the Continental Divide and west of the Appalachians (what I would call the "tornado-prone" part of the USA, if we include eastern Georgia and Florida), the chances of experiencing a tornado in a given year are the highest anywhere in the world. What sort of cost is involved with being prepared for tornadoes? If the goal is absolute protection at all times, then you need to be in or close to a tornado-proof construction wherever you are. A "tornado-proof" construction would be a formidable structure, indeed, capable of protecting its occupants in the face of an impact from a flying railroad car or semi-truck. Even the approved Texas Tech "safe room" is not so formidable. And staying within easy reach of such a structure at all times surely would restrict your activities! Absolute protection at all times is basically impossible, unless you want to live permanently in a bunker.

However, having a tornado-resistant shelter in your home would be a good start, but this is essentially a big investment for retrofitting into your home and most people never think to have one built into their dream home from the start (when it's least expensive). For that matter, there are many things you could do when building your home that would make your house more tornado-resistant than the typical, poorly-constructed frame house here in the USA. However, this sort of investment requires thousands of dollars and the knowledge to make the proper construction decisions. Moreover, it does nothing for you and your family when you're not at home. What about at work? At school? At the movies? In the mall?

A big part of being prepared for a tornado is tied to recognizing the reality that tornadoes can happen to you at any time, despite your prior experience. If you accept this basic proposition, what can you do to be prepared? There are some simple, relatively inexpensive things to do that can increase your survivability in the unlikely event that you're in a tornado.

  1. Situation awareness: be aware of the threat of severe weather every day. You can do this by checking with the SPC's severe weather outlooks, or simply paying attention to the local weather broadcasts.
  2. When a severe weather watch is issued, be prepared to do something if weather conditions warrant it. If a warning is issued or you become aware of an approaching tornado, take whatever precautions you've planned - which means you need a plan for what you'll do wherever you might be during the day or night. Make sure everyone in your family knows what to do, wherever they might be during the day or night. This entails, among other things, designating a location providing the best available shelter.
  3. Rehearse your plan at least once a year. Do your best to determine what plans exist at your family's schools and workplaces. If they have no plans, organize a campaign to force them to develop such a plan for everyone.
  4. Have a home "disaster kit" made up for your family's designated place of shelter - this might consist of, for example:

I'm not going to expand on tornado precautions here. There are many places to go to get detailed information about seeking the best shelter possible. Doing these simple and relatively inexpensive things can greatly increase your survivability in the unlikely event you're in a tornado's path. Will this provide you with absolute protection from injury in a tornado? No. But the odds will tilt greatly in your favor if you do become a tornado victim. The chances are you'll never experience a tornado, so these simple and inexpensive precautions may never be needed; but if they are, you'll be ready.

What about the Iowa campground? Most campgrounds have no tornado-resistant shelters and I'm sure this was no exception to that general rule. Does it make sense to build tornado shelters in every campground? Outside the tornado-prone parts of the USA, probably not. The cost of building adequate shelters is not trivial and most campground operators are on very tight budgets. Given that tornadoes are rare events, and this occurrence does nothing to change that fact, it's a huge economic burden to impose on campground operators.

If those who use the campground contribute voluntarily to a fund-raiser for the purpose of building a tornado-resistant shelter at any given campground, this is one way to provide some measure of safety. [Organizing such a fund-raiser might be an excellent Eagle Scout Service Project!] Having the campground equipped with weather radios is another good idea. Someone at the campground amongst the permanent staff should be designated to pay attention to the weather on a routine basis, and especially when the campground is with the SPC's Severe Weather Outlook. If a watch is issued, the campground staff should be prepared to move the campers to the designated place of shelter quickly, which probably entails restricting some of the camping activities, in the event a watch comes out - the campers need to be able to reach the designated shelter in a few minutes if a tornado warning is issued (or severe weather develops, whether a warning is issued or not).

All campers have to bear some measure of responsibility for their own safety. There's no way that organizations like the Boy Scouts should bear the full responsibility for the safety of participants. Being outdoors carries with it some enhanced risk, and people should understand that it's in their best interests to understand all the risks associated with that outdoor activity and take whatever precautions they can to minimize that risk. But your being unlucky is not necessarily someone's fault - if your campground is hit and you're injured or killed, you were unlucky. Blaming someone for a geophysical hazard that happens to cause casualties doesn't fix the problem.

Personally, I'm opposed to having a governmental mandate that all campgrounds have tornado shelters. This would be a classic example of an unfunded mandate, to which I'm philosophically opposed. For a commercial or government-sponsored campground, however, it might be acceptable to require them to provide shelters, as they can pass the costs on to their campers.

There are some issues with public shelters. These issues have been used (as well as others) for decades by the mobile home industry to lobby successfully against mandates for public shelters in mobile home parks. Public shelters can become havens for crime if they're open all the time. If the doors are locked except during use, then this can be a problem in an emergency: can the shelters be opened in time when they're needed? Some public shelters have rules about pets, preventing pet owners from bringing them into the shelter - I know of one instance where a man was killed by a tornado because his dog was refused admittance to the public shelter and he refused to abandon his pet to the storm. Some communities may require the owner to carry liability insurance for the shelter, which adds to the expense. At least some of these issues are relevant to campground shelters and could be used by those opposing any mandate requiring shelters be built in all campgrounds. Shelters require maintenance, which also increases costs. The easiest way to implement public shelters at campgrounds would be to construct a new, tornado-resistant building that would serve some other purpose as well as being the designated shelter - comparable to the "safe room" concept in an individual home.

Although I agree that the way to prevent tragedies like this one in the future would be to require shelters in every campground, I don't believe the risks are high enough in general to justify the costs unless the campground users volunteer to bear the costs of a campground shelter. A much less expensive, but effective way to reduce the risks would be to ensure that campground operators and all campers:

There's evidence that at the Little Sioux Scout Ranch, they had a severe weather plan and implemented it during this event. Lost in the outpouring of concern for the Scouts who were killed is the fact that 90+ people in the camp were not killed. In many ways, this event can be viewed primarily as a success story, not a total failure of the system. What was lacking in the camp was a shelter facility that would have afforded adequate protection for all. If every campground could have a tornado-resistant shelter somehow, it surely would be a good thing, but in this case, the system worked as well as could be expected without such a shelter. The Scouts who died simply were unlucky - most of the campers were not so unlucky. That's not much consolation to their families, but I believe it's an overreaction to campaign for mandatory tornado shelters at every campground, or to seek to blame someone for negligence in this tragedy. If the campers want to support (with resources!) the construction of tornado-resistant shelters in their chosen campgrounds, that would be a good thing - I hope they also develop a plan for its use in emergency situations. Just having a shelter, without a proper plan, is not enough.

It's been my experience that many emergency managers (although certainly not all) are not very knowledgeable about what constitutes a good plan when it comes to tornadoes. Taking shelter in a bunkhouse with a chimney (unreinforced masonry is a known vulnerability) might have been the best option available, but it's not a very good option. Many schools, hospitals, nursing homes, etc., have tornado plans but the plans are flawed in ways that compromise the safety of the occupants. Having a plan is essential, but it's also essential that the plan be reviewed by someone who's qualified to do so and approve that plan. Every Scout troop should have an approved severe weather safety plan and everyone in the troop, from the Scoutmaster to the newest Scout, should understand that plan. I have my doubts that such an ideal situation exists in many Scout troops, to say nothing of the public in general. My webpage devoted to camping and hiking safety was designed to provide information to help Scout troops develop such a plan for their outdoor activities - but I can't force anyone to do so. Neither can I provide details about what is or is not appropriate for any specific plan. Each plan is necessarily unique.

Ultimately, your personal safety is your personal responsibility. Governments and organizations can help, but the final responsibility is yours. A large part of helping young men become adults is teaching them to accept their personal responsibilities. Everyone (including Scout leaders) also has to accept that responsibility.

Update: 06 October 2008

Thanks to Brian Smith of the Omaha, NE office of the NWS, I've obtained a copy of the personal account of Dennis W. Crabb, M.D. - one of the Scout leaders associated with the Little Sioux Scout Ranch (LSSR). I'm including his account of the event here more or less as I received it, with Dr. Crabb's permission, because I feel it confirms what I suspected all along with this event: while the death of these four young men is unquestionably a terrible tragedy, the Scout leaders at this camp event actually averted a vastly greater tragedy by being extremely well-prepared for the possibility of a tornado affecting their campsite and by following their plan when the time came. In fact, not only does this account confirm my suspicions, but I'm astonished at how well-prepared the camp was for this unfortunate incident. Far from seeking to establish blame, the community has every reason to be very proud of the actions of their Scout leaders, before, during, and after the tornado. After reading Dr. Crabb's account, I'm confident that with the single exception of not having a tornado-resistant shelter at the camp, they did virtually everything right to be ready. They had a plan for just such an event, they maintained an extraordinary level of situation awareness, and responded accordingly when it became evident that the tornado would strike the camp. If leaders nationwide will just follow this example of storm preparedness, I will feel far more confident about the safety of youth hiking and camping experiences than I do now. After the tornado, of course, the Scouts and their adult leaders behaved in the exemplary way that Scouts typically do - they pitched in and used the skills they had been trained in on behalf of the victims. In Scouting, I've learned to expect this from Scouters of all ages. Our nation is considerably enriched by the Scouting program.