Chuck Doswell's

Frequently Asked Questions


Storm Chasing and Tornadoes

Last Update: 04 June 2006: moved this over from another site

Disclaimer: The contents of this FAQ list are solely the opinions of Chuck Doswell, and have no official status associated with my workplace. They have been provided here in response to frequently-asked questions, naturally. Mention of commercial products and Websites does not constitute an endorsement.

1. How do I become a storm chaser?

Becoming a storm chaser can be as simple as choosing to do so. However, just going out and chasing storms can become hazardous to you in a variety of ways (see my essay on chasing). If you go out without taking advantage of what has been learned about storm chasing, you are already behaving irresponsibly! My recommendation is to not do storm chasing! If you must try it, go out with an experienced storm chaser for at least one chase season, preferably more, before trying it on your own.

Another option is to obtain training by volunteering to be a storm spotter for your local community. This option involves making a serious commitment to be of service to your community, not simply taking advantage of the training for your own selfish ends. However, you can enhance your value as a storm spotter by chasing and learning about severe weather in doing so. Keith Brewster has provided a useful document about how to become a spotter. Being a spotter is not the same thing as being a chaser, although many folks do both. More on this later.

2. Do I need to be a meteorologist to be a storm chaser?

Not at all. There are many veteran storm chasers who have virtually no meteorological education. However, the good ones have learned a great deal about the atmosphere on their own and have become "meteorologists without a degree" as they have acquired knowledge about severe storms. If you're going to be a successful chaser, you're going to have to learn about how to be in the right place at the right time, and you can't depend on anyone else to get you there. It's in your best interests to learn as much about meteorology as you can!

3. How do I avoid the dangers of storm chasing?

This question is a complex one and I recommend you read my essay on chasing for a detailed answer. The dangers of chasing, in my opinion, are (in order of importance):

1. Driving on the highways
2. Being struck by lightning
3. Getting into the path of dangerous storms

4. How realistic was the movie "Twister"?

The movie was quite an unrealistic presentation of real storm chasing. Even good real storm chasers can spend ten or more days without seeing a tornado for every day of seeing a tornado! They pass many long hours driving, eating bad food, and staying in bad motels for every minute of tornado action. It's very easy for even the best of us to make incorrect chase decisions and miss the action. Most of storm chasing, by far, is frustration and failure, punctuated by occasional dramatic experiences. If you want life-threatening danger to flood your body with adrenaline, try jumping out of airplanes, not storm chasing! The dangers are there, but you won't experience them very often (apart from any hazards of driving).

Real storm chasing is not like the "tornado chasing" the movie shows. It's very difficult even to get within 5 miles of a tornado, much less have 4 tornadoes roll over you within one 24 hour period. And having real tornadoes roll over you isn't going to result in you emerging more or less without a scratch (to say nothing of the likelihood of being brought out in a body bag!). Real chasers don't stop in the middle of a chase for steak & eggs, and a shower, and then go out and find another tornado. A lot of the chaser jargon used in the movie (like suck zone, sidewinder, shifting updraft, or sisters) was made up for the movie; chasers don't currently use such terms. The few examples of real storm shots, like the one at the beginning of the movie, where Bill Harding (Bill Paxton's character) remarks that the " is talking..." are handled unrealistically. I recognized that sequence immediately as being from 05 June 1995 (see my 1995 chase summary) near Jayton, TX. Any chaser seeing that mesocyclone for the first time would be going ballistic, not making an offhand comment and and then going back to whatever s/he was doing.

There also are many, many technical errors in the special effects, even though they certainly are dramatic and better than most previous attempts to include tornadoes in movies. For example,

1. The tornadoes seem to be dominated by outflow at low levels, even though real tornadoes have strong inflow near the surface ... with the "F5" at the end of the movie, note the windmill near the farm implement lot swinging to face the tornado, as if it is experiencing outflow.

2. The tornadoes are shown hanging from clouds that don't look anything like real storm clouds.

3. When vehicles become airborne in tornadoes, they usually are tumbled, first, and flattened before becoming airborne, so that pristine combines and tanker trucks typically don't fall intact out of the sky.

4. The scene with hail was clearly not hail, but crushed ice - even the ordinary citizens in the theater where I saw the movie first were laughing about that one - Okies recognize hail when they don't see it!

I could go on, but it's not really necessary. In summary, no one should ever believe that what they've seen in the movie is, in fact, realistic. The realism in the movie is pretty thin!

5. How many tornadoes has Chuck Doswell seen?

Please don't ask me this question. I'm not interested in indulging in silly games about the number of "notches" in my gun. I've seen many tornadoes simply because I've been chasing since 1972. I'm not the world's best storm chaser, nor do I have any desire to be known as such.

6. What was Chuck Doswell's scariest storm chase?

I don't like this question, either. The only time storm chasing really frightened me was in June of 1973, when we hydroplaned on wet roads while driving between storms. [That experience has made us very cautious and it hasn't happened again.] I do not chase for the danger and the heart-pounding fear. If I feel any real concern about what the storm I'm chasing might do to me, I simply don't stay in a place where I feel I might be in danger. My excitement from chasing comes from having a chance to see a complex and rare demonstration of Nature's power - it's probably more like the "buck fever" that hunters experience when they find their elusive quarry than what bungee-cord jumpers must feel. [I neither hunt nor do bungee-cord jumping, so I can only speculate on the feelings of those who do!]

7. Why chase storms?

Another question I dislike. People have their own reasons for chasing, and it really isn't anyone else's business why I do so. I've had a lifelong fascination with tornadoes. My career as a meteorologist springs directly from that fascination; I didn't believe I could learn about tornadoes without seeing them, and I still hold to that philosophy. There are many places to get some insights about chasing: see the Chasing FAQ by Roger Edwards and Tim Vasquez, an essay on the subject by Dave Hoadley, and some of the articles in the 20th Anniversary Issue of Storm Track magazine.

8. Can I go chasing with Chuck Doswell?

Sorry. I don't enjoy "tag-along" chasers, either in our vehicle or following along behind us. Although I've recommended you chase with someone experienced for awhile, I'm not available for this purpose, so don't ask. My chase season is limited to an approximately 3-week "window" each year and constitutes my vacation. During my chase vacation, I'm not chasing in any official capacity; I'm on vacation, and I would prefer not to have someone tagging along on my vacation. Would you like me to accompany you on your holiday? We have limited space in our vehicle and while I can't prevent you from following us in your own vehicle, I'll not like it very much! Besides, I get numerous such requests every year. If I respond positively to one, why not to all? Then, it would take a bus to carry my "chase crew" - the obvious solution is to respond to all such requests the same way. If you want a chase partner, see the next item.

9. How do I get in touch with someone to be my chase partner?

My only suggestion is to visit the Storm Track homepage and "advertise" your interest in finding a chase partner. At the moment, experienced storm chasers are vastly outnumbered by the chaser "wannabe's" so it may be difficult to find a chase tutor. Alternatively, you can buy a "packaged" storm chase vacation, with an experienced storm chasing "guide". Try: Silver Lining Tours, Tempest Tours, or Cloud 9 Tours ... the presence of these links at this site doesn't constitute a commercial endorsement of these tours on my part. I'm simply providing these links as a service - specifically, I'm not responsible for what you may experience resulting from your participation on a purchased storm chasing tour, in general.

10. What gear should I bring along on a storm chase?

Another unfavorite question. It's not my responsibility to be the storm chase equivalent of an "outfitter" and what you choose to bring along on a chase ought to be your own business. I don't know your reasons for chasing and that surely has a big impact on what you choose to bring along. Surely you can make your own choices for personal gear. Experience is a great teacher and if you find you brought along stuff you didn't use and/or needed things you didn't have, then you'll know better the next time. That's the process I've used. For guidelines, however, see here.

11. Where can I get more information about storms (and/or meteorology)?

Try the Storm Track homepage or WeatherNet. You can also use any of the Internet search engines to pursue specific topics. Go to the Storm Track website. However, if you'r seriously interested in learning about meteorology, the Internet is not the place for such a pursuit. I suggest you go to your local libraries and read everything you can find on the subject. If you live near a college or university, check them out, especially if they offer courses in meteorology. Even if they dont have a meteorology department as such, they usually have a geography department that will have access to meteorological information. Visit your local office of the National Weather Service; they have pamphlets and information about storms to distribute to the public. Contact NOAA's Public Affairs office and ask them to send you information.

12. Where can I get tornado and other storm photographs or video?

Try contacting: Storm Track merchandise, Warren Faidley, Prairie Pictures, or The Tornado Project. The NSSL Employees Association also has images for sale, including a few of mine. I own the copyright to most of the images within my Website and I will pursue copyright infringement litigation for unauthorized use.

13. If I chase storms, what are my responsibilities regarding reporting what I see?

I've discussed some of this in my essay on chasing. If someone sees a tornado that might strike a community without warning, I believe anyone's conscience would require them to do their best to report the tornado. If you have knowledge that the situation is in hand (warning sirens are going, or you hear warnings on the radio), then you may choose to go about your own chase business. Let your conscience be your guide.

Arguably, the best way to report a tornado is to become a licensed amateur radio operator and contact the local spotting networks to report what you're seeing. Be aware that some of these networks are tightly controlled and may not want reports from unauthorized persons. Given the complexities of spotting and amateur radio in general, this FAQ list cannot provide a detailed discussion of all the ins and outs of amateur radio tornado spotting. [see the Keith Brewster page mentioned above.] The spotting program often goes under the name SKYWARN.

Lacking an amateur radio operator's license and gear, a Citizen's Band radio might work as an acceptable substitute. Also, a cellular phone might be useful for the purpose of reporting. See the Storm Track website for more information about reporting what you see. Lacking some "instant" communication system (like a cell phone or a 2-way radio of some sort), it's not clear that chasers actually can offer much help in terms of spreading the word of an approaching tornado.

Generally speaking, if you're a storm chaser and you're in or near a community that already has been struck by a tornado, common sense ought to prevail:

1. If you see casualties and there is no one else about, a good conscience would suggest that you stop and render first aid. Most states have "Good Samaritan" laws that will protect you from lawsuits - but if you lack the knowledge to help a seriously injured person, you also need to consider whether or not you would do more harm than good by attempting to help. If the choice is to stand by and simply let someone die, then by all means try to help, of course. Learning CPR and First Aid is probably not a bad thing for all chasers to do.

2. Unless you're asked to help by local emergency officials, you probably should get out and stay out of any tornado-damaged areas. At the very least, you could be getting in the way of responsible help-givers, and you may be taken for a gawker or even a potential looter by the police.

Even if you make a report in real time, but especially if you don't, please report what you saw in terms of severe weather to the nearest office of the National Weather Service at some point, even if it's days after the event. It helps to have precise locations of the events (not your location necessarily, but where the event occurred), and times of occurrence. Doing this ensures that what you saw can become part of the official climatological record of what happened. The official criteria for severe weather are: 1) hail 2 cm [3/4 inch] in diameter, or larger, 2)wind gusts 25 meters per second [58 mph] or higher, 3) certain types of straight-line wind damage [trees uprooted, significant damage to homes and structures, etc.], 4) any tornado.

14. How do tornadoes form?

This is far from being completely understood. See my essays on tornadoes: (1) thoughts after VORTEX, (2) defining a tornado, and (3) more thoughts about tornadoes. Basically, we currently believe many tornadoes come from supercell storms but some tornadoes are produced by non-supercell storms. A supercell is a rotating storm, but not all tornadoes come from supercells and not all supercells produce tornadoes. Trying to understand more about tornadoes was a major purpose of the VORTEX project. Tornadoes develop from weaker vortices that "spin up" into tornadoes. Under the right conditions, the initial weak vortex undergoes a process called "stretching" - not unlike the way an ice skater spins up by pulling in his/her arms - in physical terms, this is known as conservation of angular momentum. Once it begins, the development of a tornado can proceed very quickly - in a matter of a few minutes. The weaker vortices that sometimes become tornadoes apparently can form in a number of different ways, so not all tornadoes have the same origins. Where storms seem to differ from each other is in the way the weak vortex that spins up into a tornado is created - some storms don't seem to create them at all, others create the weak vortices but for reasons not understood, they don't go on to become tornadoes, some storms create tornado-like vortices aloft but they never intensify at the surface, and a few seem to create tornadoes from these weaker vortices pretty easily. All of the complexity of the real atmosphere makes this question a lot harder to answer than you might think. Progress has been made, but a simple, comprehensive answer to the question seems unlikely any time soon.

15. Where and when should I go to chase tornadoes?

There are two ways to answer this question. The first is the climatological version: in general, tornadoes are most frequent in what is commonly called "Tornado Alley" (see Figure 1), during the months from April to June. The central plains of the United States have the most frequent and most violent tornadoes of anyplace on the planet, but they can occur at other times and places, including other countries (e.g., France, Russia, Australia, Argentina, India, South Africa, Canada, and others). If you're planning a chase vacation, the most "chase-able" tornadoes (i.e., tornadoes during daylight, not moving too fast to chase and not so wrapped in clouds and rain that they're difficult to see, in country without a lot of hills, trees, and buildings) are most common in Tornado Alley, from early May through mid-June. Obviously, depending on the overall weather pattern, the focus for tornadic activity during your chase vacation may shift to some place other than the climatologically-favored region.

Figure 1. Chuck Doswell's version of Tornado Alley. This doesn't necessarily agree with actual observed distributions of tornadoes - many tornadoes go unreported in the sparsely-populated High Plains.

The second way to answer this question is the day-by-day version: basically, an accurate forecast is difficult because our state of knowledge does not permit precise forecasts of when and where tornadoes are going to occur. Therefore, you shouldn't expect to have someone else answer it for you. Learn how to make your own forecasts! And you'll have to accept the inevitable mistakes (bad forecasts).

16. Does "Dorothy" or something like it (as seen in "Twister") actually exist?

In the movie "Twister," the chasers are trying to deploy something called "Dorothy" that consists of a large number of instrument packages inside plastic "bubbles" that will send data about the tornado back to the chasers. The container holding these sensors looks to be modeled after a real instrument package called "TOTO" (for TOtable Tornado Observatory) that was developed by Dr. Al Bedard of ERL in Boulder. The idea was for a chaser to put TOTO down in the path of a tornado so that data from the passage of the tornado would be recorded on magnetic tape. TOTO was roughly the size of a 55 gallon oil drum and was designed to stay put (hopefully) during the passage of a tornado. For a number of years, it was carried about during storm chases by Prof. Howard Bluestein of the School of Meteorology, University of Oklahoma. Then, TOTO was given to NSSL to attempt deployment. All these efforts were essentially unsuccessful because it's difficult to put objects in the path of a tornado! Only once was TOTO put nearly into the tornado path; that particular chase effort is "immortalized" by the PBS "NOVA" program on tornadoes that aired first in 1986. TOTO has been "retired" for a number of years and now rests quietly in the NOAA museum in Silver Spring, Maryland.

As it now stands, the technology that "Dorothy" uses is probably within our real capabilities (especially with respect to Department of Defense technology), but only if tornado research programs get significant increases in their funding - no one is really developing these in the back of an RV! There are several technical barriers to achieving that sort of a probe of a tornado (although with enough funding anything becomes possible).

Perhaps most important, having such a "swarm" of sensors within the circulation of a tornado would not provide all that much of value for tornado forecasts and warnings. Knowledge of the actual processes going on in a tornado are of considerable scientific interest, but it's quite unlikely that such knowledge would lead to increased warning lead times (as was stated during the movie). To increase the warning lead times, we need to know more about how and why tornadoes form in some storms and not in others. Moreover, we need to sample many storms. Probing one example doesn't really represent all that much of a potential breakthrough - every storm is different. During VORTEX, scientists attempted to deploy an improved version of TOTO, called "turtles." More information about the VORTEX turtles can be found here. At least one successful deployment of turtles was done during VORTEX, and more sophisticated versions, now called "probes" have been placed in tornadoes since then.

17. Why does "Tornado Alley" have so many tornadoes?

The idea of "Tornado Alley" is not a scientific one - it's something that has been created by the media. However, it's certainly true that tornado frequency varies around the United States (and, indeed, around the world). Some places have pretty high tornado frequencies compared to the rest of the world and it's inevitable that someone wants to call such locations by the term "Tornado Alley."

However, at face value, this question is pretty difficult to answer. If we don't understand tornado formation completely (and we don't) then we couldn't possibly explain why some regions have a higher frequency of tornadoes than others. Nevertheless, I can say this much: the unique physical geography of the plains east of the Rockies make it a region with high tornado frequency during early and middle spring. In late winter and early spring, tornadoes also occur with relatively high frequency in the states bordering the Gulf of Mexico. Although it's simplistic to use the notion of the "clash of air masses" that's so popular in the media (see item #B.21 here), the juxtaposition of

(1) dry, unstable air from the west, on top of
(2) low-level moisture from the Gulf of Mexico, and in the presence of
(3) strong temperature contrasts to develop vertical wind shear

produces conditions favorable for the development of supercells, and it seems that most strong and violent tornadoes come from supercells. Anything that promotes supercells also makes tornadoes more likely. The Great Plains and the Southeast show the highest risks of tornadoes, and so could collectively make up a region someone might want to call "Tornado Alley," but even within the local peaks of tornado frequency, tornadoes (especially the violent kind) are still pretty rare events, whereas outside of the peak frequency regions, tornadoes are even less frequent but still possible. If a tornado is possible, I know of no reason why a violent tornado is not possible, as well. Ask the citizens of Worcester, Massachusetts, or Edmonton, Alberta (in Canada).

Many tornadoes happen outside of anyone's version of "Tornado Alley" so living outside of the regions of peak frequency in the U.S. does not make anyone safe from tornadoes - they've happened in every state, and they'll happen again in those locations, if you wait long enough. If you live in a place where tornadoes can happen, but you've convinced yourself somehow that tornadoes don't happen where you live, then you may not take appropriate actions to prepare yourself for the rare, but real risk of a tornado.

18. How do chasers know when a tornado is changing its direction of movement?

This question was triggered by the abilities shown by the Bill Harding character in "Twister." There are some occasions in the movie where Bill's profound "understanding" of storms allows him to anticipate changes in a tornado's movement. Most of Bill's apparent ability is pure fiction. Tornado movement is dominated by movement of the storm that produces the tornado, and for the most part, tornadoes do not exhibit the erratic movement so popular in movies (including those in "Twister" and the swaying back and forth of the tornado in "The Wizard of Oz"). When tornadoes make sudden changes in direction, it's typically whenever they are affected by an outflow - as in the beautiful Cordell, Oklahoma tornado movie shot on 22 May 1981 by Howie Bluestein. In such cases, the tornadoes are usually on a rapid road to dissipation. In some cases, it might be possible to anticipate the impact of an outflow boundary on a tornado, but it's certainly going to be difficult to do so until the change is already underway. I know that I'm not that good!

19. In "Twister" at the end, they show the inside of a tornado that has a clear "eye" extending from the ground up into the clouds. Is this true?

It is important to keep in mind that "Twister" is just a movie and any resemblance between what is shown in the movie and reality is purely coincidental! Within the core of any vortex, there must be a point where the rotating part of the wind goes to zero - if the tornado's moving, the air at that point must be moving with the same speed as the vortex - otherwise, it'd be flowing out of the tornado. Is there really a clear "eye" in tornadoes, as there is in tropical cyclones but on a smaller scale? Again, not all tornadoes are the same, but at least some tornadoes have an eye-like structure - as shown in special radar data collected by mobile Doppler radars. However, we've no scientific observations that would confirm or deny that it is clear within such an "eye." It appears quite possible, but no one really knows for sure. From a scientific viewpoint, this isn't the most compelling issue - in other words, it's not a top scientific priority to know whether or not tornadoes have clear "eyes."

20. How do I become a professional storm chaser?

Chasing as a career is basically not an option - storm chasing is not a profession. To date, the only ways I know of to make money from chasing are:

a. Sell storm photographs and video. In effect, this is NOT being paid to chase - it's being paid to be a photographer or videographer of storms. In order to be successful at this to any real extent, you need to be a photographer and/or videographer of some considerable skill to compete in the image markets, and have some knowledge of business. Plus, you'll need to be a good storm chaser!

b. Chase storms for a TV station. In some parts of the country (including those of us here in central Oklahoma), TV stations have hired chasers to get them live and recorded storm footage. I have no clue what they pay their chasers, but I doubt if they'll be paying them outside of the local "storm season" unless they're doing something else for the station during the rest of the year. Thus, this hardly qualifies as a "career" either.

c. Give guided "chase tours" There are enough new people wanting to chase storms that some folks are attempting to fill this niche by giving "chase tours." Naturally, this requires some considerable investment in vehicles, etc.; riding herd on a number of people doesn't strike me as much fun (personality clashes, trying to find motel rooms at the end of a chase day, keeping track of everyone, listening to complaints about not seeing a tornado, etc.). Anyone earning income this way is earning every dime, in my opinion. It's a very seasonal business, so they have to make enough from their clients to continue to eat during the time of year when storms are rare, unless they have some other income source.

There may be some very limited opportunities for a few folks to make enough income to survive from one or more of these three options, or some option about which I don't know, but storm chasing is hardly a mass market. You'll need to have some important skills apart from chasing in order to survive, either in marketing or business, as well as such skills as photography/videography. Please accept the fact that chasing is basically a hobby (and an expensive one!) that you might at best be able to earn enough from to make it pay for itself. There are not likely ever to be true professional storm chasers! There are scientists who may chase storms for scientific purposes, but they're not professional storm chasers, either - they're scientists who use storm chasing to learn about storms.

21. What's the relationship between storm chasing and storm spotting ?

Storm spotters are mostly unpaid volunteers who serve their local communities in mitigating the impacts of hazardous events like tornadoes. They're generally not allowed to roam freely about, chasing whatever storms they wish. Rather, they have an important job to do and they've generously volunteered their time on behalf of the citizens in their community. Chasing is basically irresponsible activity (or, perhaps somewhat less pejoratively, self-centered activity), done by individuals who, for reasons of their own (some good, some not-so-good), want to see storms.

22. I want to build a "toy" tornado vortex model. Can I get plans or ideas about how to do this?

Please see here for information about how to acquire a tape that, among other things, teaches you how to build low-cost tornado models.

23. I've heard about a method for detecting tornadoes by the sounds they make. How does this work?

Sorry, this isn't something I know anything about. Please check out the Website created by Dr. Al Bedard of NOAA's Environmental Technology Laboratory.

24. What about the famous, extremely damaging tornadoes, like Jarrell, Texas this year (27 May 1997), or the Tri-State tornado of 18 March 1925? How should these events be handled?

I've written extensively about what is normal, elsewhere. It's typical of weather that the extreme events are rare events. Because extreme damage is rare, we really don't know very much about such events. A related sort of rare event is a violent tornado in a region not known for frequent tornadoes, like the Worcester, Massachusetts tornado of 09 June 1953. Of course, if violent tornadoes are rare in general (say one event out of 100), and tornadoes of any intensity are rare in some location, it's still possible for a violent event to occur in a place where tornadoes are rare - but they will not happen very often, right? Tornadoes are rare events to begin with, and the occasional violent examples are on the margins of an already rare event. When such events do happen somewhere (and somewhen ), as they inevitably must, they're memorable and tend to stand out as a result. Perhaps they stand out too much - they're always in some sense unrepresentative of the "average tornado" (whatever that might mean!).

Our records really contain too few such extreme events to be confident we know such things as how often they occur, or where they're most common. The Tri-State tornado is particularly disturbing, as we've not seen anything even remotely like it since then, and there are perhaps some reasons to question whether or not it was a single tornado - the available data are subject to different interpretations because the hard facts about such storms in 1925 are pretty sparse. What we do know about tornado climatology says that there will be something on the order of 5-20 violent tornadoes (F4-F5) in any given year - we certainly don't have a clear idea of where or when they will occur. If we ever see something like the Tri-State tornado again, we might be able to put it into proper perspective. Otherwise, it remains a singular event! There've probably been an average of at least 1000 tornadoes per year since 1925 (although the climatological record shows far fewer, of course), so the Tri-State event is something like 1 in 100,000!! Until we have something like it again, we don't know how large that number is going to go. I have an essay on some realities about tornadoes that's relevant to the occasional violent tornadoes like Jarrell, or whatever. If we're willing to wait long enough (say, millions of years), there's no telling what we might see in terms of extremes - but we have a fair ways to go before we enter our thousandth year of observing tornadoes with something like scientific care. Most of us aren't going to live that long.

Ultimately, it's very difficult to anticipate the occurrence of an extreme event, to recognize that the situation has become extreme, and to convey that recognition to anyone such that it would help. That is, it's unlikely that anyone would forecast another Tri-State or Jarrell tornado (we're very uncertain about many aspects of the meteorology of these extreme events), so it's not obvious that such an extreme tornado could be recognized for what it is in time for that recognition to do anyone any good and, since tornadoes are rapidly-changing processes, by the time word got out, the situation might well have changed. It seems to me that what we need to do is to get the public to prepare for the worst, because we meteorologists aren't likely ever to be able to guarantee that the worst will not happen! It probably won't happen - that's the nature of rare events (and an extreme tornado is a rare example of an already rare event) - but it would be foolish to assume that an particular tornado is not going to do extreme damage.

25. How effective are NWS tornado forecast products and are they improving in accuracy?

Please consult the latest Policy Statement by the American Meteorological Society. You might also want to consult my essay about the realities about tornadoes, mentioned just above. The effectiveness of NWS tornado forecast products depends on more than just the accuracy of the forecasts! As noted above, public education is an important factor in the reduction of casualties (and damage!) from tornadoes.

26. I've got an idea: why not use bombs (or flames, or liquid nitrogen, or whatever) to disrupt tornadoes?

This is an idea that seems to occur to many folks and superficially it seems plausible. If we set off a big enough explosion (or whatever) to disrupt the tornado, it would save all those lives and all that property. I have a number of points to make about this rather old idea:

  1. The tornado is a process embedded within a larger process. Disrupting a tornado with explosions or whatever could probably be made to work if the explosion is big enough (see my next point), but the processes that produced the tornado (the supercell thunderstorm) are still going on and almost surely will create another tornado in short order. To disrupt the supercell would require titanic energies (see Item #2) - at least 10 times greater than those of the tornado itself.
  2. The cure (in the case of explosions or exothermic reactions) could be worse than the problem you are trying to alleviate. Citizens might justifiably resent having bombs exploding over their property, or having liquid nitrogen-cooled air descend on their crops.
  3. Adding cold into a downdraft would certainly enhance it. Is this really going to have a detrimental effect on a tornado? No one knows.
  4. Have you considered the volumes of air that flow through supercell thunderstorm up- and downdrafts? We're talking about many cubic kilometers of air passing through the circulations. The amount of energy it would take to change the temperature (either heating or cooling) of the air passing through either the updraft or the downdraft would be huge. Sit down and calculate what amount of energy is needed to change the temperature of one cubic kilometer of air by one degree Celsius, and then figure that a reasonably strong storm processes something on the order of 70-100 cubic kilometers of air every 20 minutes or so. Big chunks of energy are involved here and the price of energy is an important factor.

I'm not convinced we are talking about something practical (economically viable), even if it managed to be successful in suppressing the tornado. Consider the following cost discussion:

If you want to do explosions instead of heating or cooling the air, assume that in order to disrupt the tornado, you need the equivalent of about 1 kiloton of TNT. [I'm assuming that nuclear or thermonuclear detonations are out of the question for obvious reasons!] What's the cost of that much explosive? What method are you going to use to deliver it to the right place, quickly? It isn't going to be via any vehicle driven on the roads, but must necessarily be some sort of aircraft delivery system. Assume an effective delivery system (like an air-to-air missile from a jet aircraft) costs roughly $1 million, for each missile. I have no clue what it would cost to operate an aircraft capable of delivering such a device, but it certainly is not like renting a car! Don't forget to include the cost of the pilot and any other aircraft crew, plus the maintenance costs for the aircraft, plus hangar fees, plus the maintenance crew and lodging for everyone, plus training for this specialized mission, plus practice runs. Figure on the training and overhead for a crew of 10 people to coordinate all of this activity. In order to deliver the "cure" to any location in the tornado-prone part of the U.S., even using jet aircraft, you will need about 100 crews - remember, the typical tornado only lasts a few minutes. Including all the overhead associated with the delivery system, a conservative estimate would be that each shot would cost several million dollars. We are talking Department of Defense-type systems, here.

Once you know the approximate cost of doing this exercise once for a single tornado, then multiply that by roughly 1000, for each reported tornado. That amounts to something like several billion dollars per year. Balance all this against the annual tornado damage figures (on the average, about $500 million). If the cost of carrying out this exercise is not less than that damage figure, which it isn't, it's not worth doing even if it could be made to work.

And please don't mention the "priceless" value of human life as a reason to invest in tornado suppression technology. We're much better off putting resources into improving forecasts and warnings for tornadoes than we would be trying to prevent them by silly "brute force" methods along these lines. Moreover, we've no idea what atmospheric consequences might arise if all tornadoes were successfully suppressed. In my opinion, unless we can be reasonably sure of the consequences, it'd be dangerous to interfere with the atmosphere's workings. As it stands, however, we're unlikely to see any feasible effort to suppress tornadoes anytime soon. [See also Item #37, below]

27. What's the story with seismic detection of tornadoes?

This is also something I don't know much about. The concept of seismic detection of tornadoes is based on the hypothesis that tornadoes create some sort of distinctive seismic signature -that is, waves that propagate in the solid earth. A Website describing it briefly can be found here. Seismic tornado detectors are being marketed by a private company. I can't comment about the efficacy of seismic tornado detection - it's not yet been the subject of a thorough scientific test by an independent researcher, and no substantive evaluation of the system has appeared in the refereed scientific literature. My advice is: caveat emptor!

28. A while back I heard about a way to detect tornadoes using a television. How does this work?

A number of years back, it was thought that tornadoes had some detectable signature in the radio frequency part of the electromagnetic spectrum, presumably owing to some sort of special lightning caused by tornadic versus non-tornadic storms. Decades ago, someone named Weller even came up with a method using a television (which is transmitted on radio frequencies) to detect tornadoes (please don't ask me for details ... I don't know them and I don't want to know them). For the moment, these ideas have not gained many supporters within that part of meteorological science associated with tornado research -in my opinion, there's no credible evidence suggesting that tornadic storms have some unique signature in the radio frequency part of the electromagnetic spectrum, compared to non-tornadic storms. I know of no systematic study that demonstrates the method does work! If it did, then there might be some interest in understanding how it worked.

29. What effect is El Niño having on tornadoes?

I've discussed the supposed effects of El Niño on the weather, in general, on my Pet Peeves page (item # B.12). Although El Niño (and its counterpart, La Niña) certainly can influence the general circulation pattern around the world, and that pattern (in turn) alters the probabilities of certain events, it's absurd to say that a particular tornado was "caused" or "spawned" or "driven" by El Niño. In spite of the fact that it appears that El Niño can make some events more (or less) likely, this does not imply that a particular event (e.g., a tornado) is directly attributable to El Niño.

30. Is it true that tornadoes avoid ( or follow) rivers (or other topographic features)?

In many locations around the US, it's widely believed that tornadoes are deflected by such things as rivers, hills, or other topographic features. Although there are good reasons to believe that tornadoes are indeed influenced by topographic features, it's also true that there have been notable exceptions to the local mythology about tornadoes being deflected by such things. For example, it was believed for a long time that Topeka, Kansas was protected by a hill called Burnett's Mound to the southwest of town - this idea may have had its origins in Native American legends. However, on 08 June 1966, a violent tornado went directly over Burnett's Mound on its way into Topeka! So much for that legend! During the 03-04 April 1974 tornado outbreak, a violent tornado apparently went right up the side of a 3,000 foot mountain and then right down the other side, all without any break or diminution in damage along its path. It seems that for violent tornadoes, at least, "obstacles" like hills and rivers mean virtually nothing.

Most significant tornadoes are thousands of feet tall, so that it seems unlikely to me that minor bumps in the terrain, or a river valley is going to have all that much of an effect on such a tornado. However, this is not to say that topographic effects are completely negligible. There is evidence that alterations in the low-level winds by topographic features may make tornadoes more or less likely in a given weather situation, or might nudge the tornado path one way or another. Based on available evidence, such effects seem most likely in cases where the tornado is not a violent one. This hasn't been studied to the point where it's possible to offer a strong conclusion - but it seems very unwise to count on the efficacy of some topographic feature to protect you and your property from a tornado.

31. Does a tornado really suck a water out of a well, or a swimming pool?

For many decades, it was believed that the pressure drop within a tornado vortex was capable of all sorts of things: sucking wells, rivers, or swimming pools dry - making buildings explode, pulling the feathers off chickens, and other bizarre tornado "oddities" reported from time to time. Although we scientists still don't know the details of the pressure and wind distribution at the surface associated with tornadoes, it's now pretty much accepted that the pressure drop in tornadoes is probably on the order of a tenth of an atmosphere (~100 mb) or less in most cases. This sort of pressure drop simply is incapable of doing most of the things that are attributed to tornadoes on occasion. Water is relatively heavy, and a pressure drop of 100 mb can only lift a water column about 3 feet. Reports of swimming pools or wells sucked dry have always turned out to be false (they were empty before the tornado came through). Most buildings can leak enough air that they won't "explode" from the pressure effects - the appearance of having exploded can be explained from the high-speed winds alone, according to engineers. Frightened chickens are known to shed feathers as a defensive strategy. The strong winds in a tornado can whip up considerable spray when the tornado passes over a body of water, of course, but a tornado is unlikely to be able to spray enough water from the surface to cause a river to be swept dry momentarily, or to drain a swimming pool (except perhaps a very shallow pool!). Most tornado "oddities" attributed to very low pressures are certain to be either fabrications or misunderstandings of the observations.

32. Storm chasers seem to want tornadoes to happen! This seems inappropriate, given the destruction and death that tornadoes can cause. How can you chasers live with yourselves, wanting to see tornadoes?

This is a really troubling question, and one that was brought home to me the day of the infamous Union City, Oklahoma tornado of 24 May 1973. We drove into the north side of town as the tornado was leaving the town, towards the southeast. We arrived even before people began to emerge from whatever shelters they had managed to find. It occurred to me suddenly that the event that I wanted to happen - a tornado - was responsible for all the devastation that I saw. Indeed, how could I live with this? This "revelation" caused me quite a bit of anxiety and forced me to think long and hard about what I was doing.

Since I'm still chasing, I obviously came to some sort of accommodation, and it goes like this: the atmosphere doesn't care one bit what I want! My wanting to see a tornado doesn't make one happen, so I can't possibly accept any responsibility for the occurrence of a tornado that I happen to see. Like most responsible chasers, I have absolutely no desire to see a tornado hit anything more substantial than open grasslands, but nature doesn't necessarily accommodate us on that score, either. Tornadoes happen or they don't happen according to nature's whims, not ours.

Since tornadoes and tornadic storms are well outside of our control at the moment, the best anyone can do is learn how to predict when and where they're going to happen, in hopes that such knowledge can lead to saving lives and reducing injuries. For myself and a number of other responsible chasers, I can point to several contributions from storm chasing that I believe have contributed toward these goals: scientific papers that have increased our understanding of tornadoes and tornadic storms, slides and videos contributed at no charge for the purpose of developing spotter training programs, etc. I take considerable satisfaction from knowing that chasing has allowed me to give something back to all the citizens who live under the threat of tornadoes. Although we can't yet do much to prevent the damage and disruption that tornadoes can cause, I'm confident that storm chasing and the fruits of having meteorologists see real tornadoes for themselves have improved our society's capability to deal with these events. Responsible storm chasers have no reason to feel guilty about being excited by the spectacle of severe storms. I can't say the same for irresponsible chasers, of course.

33. Are tornadoes becoming more (or less) frequent? Is this related to global climate change?

The historical record of tornadoes is pretty short. Although records of tornadoes in the United States go back to pre-Revolutionary times, it's obvious that the settlement of the tornado-prone areas in this country wasn't very extensive until the 1920s or so. The record of the number of tornadoes observed has been changing, but it's not at all obvious that these changes reflect anything more than a large collection of biases in our records.

Obviously, the number of tornadoes is not the same from year to year - a certain amount of interannual variability is to be expected. The relative brevity of reliable tornado occurrence data (as discussed here or here) means that we don't know the interannual variability very accurately. We still are seeing new "records" set - October of 1998 saw the largest one-day outbreak of tornadoes ever in the month of October, for example. The number of tornadoes during January 1999 (with several outbreaks on different days) set an all-time record for January, by a wide margin. These suggest that we have not yet seen the extremes possible during some given year - I noted in Item #24 that we've not seen the like of the Tri-State tornado since it occurred. However, given that it happened in 1925, it's possible that it was not a single tornado. But if it was, we have no idea how long we might have to wait to see a similar example. Similarly, we haven't had a reoccurrence comparable to the 3-4 April 1974 tornado outbreak in 25 years. Who knows how long we would have to wait to match or exceed that "Superoutbreak?" Logically, if we've seen only one event of a particular sort, then we have no clue about the frequency of such events!

Furthermore, the way we now keep records about tornadoes is different than the way we did it in the past. This makes difficult the task of comparing records from early in the 20th century to those we keep today. Therefore, it's pretty much impossible to know just what our records from more than about 40 years ago might show if they'd been keeping track of tornadoes back then in the same way we do now. And it's likely that things will be different 40 years into the future, as well - we probably are not doing our record-keeping today in a way that will look acceptable to scientists in the future.

Therefore, an honest answer to the first question here is "We don't know, and have no credible basis for saying that any long-term change in tornado frequency is happening."

As for the second question, the connection between global circulation patterns and tornadoes is pretty tenuous, and our current state of understanding simply doesn't permit us the luxury of affirming or denying the relationship between putative global climate changes and the occurrence frequencies of tornadoes. There are many, complex physical linkages between the global climate and a tornado - it would be very difficult to be confident of that whole large set of mostly nonlinear connections along that path (see item #29, above). I don't believe that our scientific knowledge permits any answer to this question, much like the first. Those who say that they know what will happen to tornado frequency if the climate changes in a certain way are, in my opinion, either misguided in their beliefs or may even be engaged in deception.

34. Why do tornadoes rotate counterclockwise?

Of course, it's true that most tornadoes counterclockwise in the Northern Hemisphere; in the Southern Hemisphere, most tornadoes rotate clockwise. About 99 out of 100 tornadoes rotate cyclonically (counterclockwise in the N. Hem., clockwise in the S. Hem.) because the initial weak circulations that go on to become tornadoes rotate cyclonically (recall Item #14, above). These vortices that eventually give rise to tornadoes rotate cyclonically because of the way the thunderstorm updraft interacts with vertical wind shear (see my Primer on Vorticity - WARNING: this "primer" is pretty technical) - this process typically makes cyclonic rotation the preferred sense of rotation for vortices that go on to become tornadoes.

It might be tempting to look for the preferred sense of tornadic rotation in the rotation of the earth. However, the Earth's rotation is only indirectly related to the process that gives rise to tornadic rotation, through the way it influences vertical wind shear. It can be shown that the rotation of the earth can't be directly related to a tornado's rotation because on the space and time scales of a tornado, the direct influence from the Earth's rotation is completely negligible. Perhaps the most compelling evidence is that numerical simulation models that begin with observed vertical wind shear characteristics can reproduce most of the behavior of tornadic thunderstorms, even when the earth's rotation is ignored in those simulation models.

Rarely, the initial vortex that goes on to become a tornado rotates anticyclonically; that is, in the opposite direction to most tornadoes. In such instances, the resulting tornado rotates anticyclonically. The same thunderstorm that produces a cyclonic tornado can sometimes also produce an anticyclonic tornado, but not in the same part of the thunderstorm where cyclonic tornadoes form.

35. By what mechanism can a tornado produce "oddities" -- such as when they pick up fragile objects, carry them through the air, and set them safely down -- undamaged -- hundreds of feet away?

There are no general satisfactory answers to questions of this sort. Tornadoes create very complex wind patterns that interact with complex structures (like homes with fragile objects inside them) to produce even more complexity. If you've ever seen tornado videos, perhaps you can appreciate how complicated they are, especially near the surface, where the damage is done. "Freak" events are actually rather commonplace amidst the devastation of tornadoes - being in a tornado involves being in a very odd place, where strange things are the rule, not the exception - sort of a terrible, nightmarish version of Alice's Wonderland.

So-called "freak" occurrences cannot be "explained" in specific cases because we have no way of knowing just what was happening with enough detail. That is, we would need to know the detailed wind patterns right near the surface from one second to the next, as the tornado interacted with the structures ... wind information of this sort is simply not available, even with the best technology we have at the moment. Any "explanation" that didn't have enough data to validate it would be unscientific - it might be the correct version of how that event happened, but there would be no way to verify it, so it would be mere speculation and, hence, unscientific.

When objects are carried into the air, it seems that at least some of them come down gently for reasons we can only speculate about. I personally have seen some examples of odd things that occurred in tornadoes and asked the same sorts of questions, but we just don't have the information with which we could even try to develop some idea of how a specific event actually was created.

36. Was the tornado that hit the Oklahoma City area on 3 May 1999 actually an F-6 tornado? Was it the worst tornado ever?

A lot of hype has been perpetuated about this - so much so, in fact, that I've written an essay about it, that can be found here. As for this particular tornado being a record-breaking event - there's no way to know, but I doubt that it was the worst ever. My colleague, Harold Brooks, and I have developed evidence that the worst tornado event in U.S. history, in terms of damage, might have been the tornado that hit St. Louis, MO in 1896! The worst tornado ever, in terms of fatalities, is the Tri-State tornado of 1925, of course (see item #24, above). See my essay for an in-depth discussion of tornado "records" however.

37. Is it possible that we could prevent tornadoes by cloud seeding (or other means of intervention)?

This idea has received a fair amount of media attention of late, to the extent that I also wrote an essay about it, which can be found here. The short answer is that I don't believe there is any credible scientific evidence to suggest that this is possible. I'm opposed to putting taxpayer dollars into research projects that have no plausible evidence to support them. It seems to me that we should have some reasonable expectation of the proposed method being (a) effective, (b) practical, and (c) safe (in terms of negative side effects) before we even consider exploring the possibility of altering the natural weather.

38. What about electrical and/or magnetic influences on tornadoes?

The history of tornado research is replete with hypotheses about the influences of electricity and/or magnetism on tornadoes. There are many eyewitness stories of strange electrical phenomena (virtually never seen during observations by qualified scientists!) in association with tornadoes. In bygone times, when it was widely believed that tornadic winds reached 500 mph or even higher, it was believed that purely meteorological processes could not explain such high windspeeds. Hence, all sorts of electrical and/or magnetic effects were postulated to be important, most of which were impossible to substantiate.

With time, many of these exotic explanations have been abandoned because there is no need to explain windspeeds beyond about 300 mph. Such windspeeds can, in fact, be produced by "ordinary" meteorological processes and don't require additional explanation via electrical or magnetic effects. Scientific analysis shows that electrical effects in thunderstorms are only a trivial part of the storm's energy (see here for some discussion), so it appears to be unlikely that electrical and/or magnetic effects (notably, lightning) play any meaningful role in creating or controlling tornadoes.

The idea of a relationship between tornadoes and electricity/magnetism persists, however. Many non-meteorologists continue to believe that tornadoes are uniquely associated with storms characterized by unusual lightning activity. The reality is, however, that (a) most storms with unusually high cloud-to-ground (CG) flash rates are not tornadic, and (b) many tornadoes occur in association with storms having little or no CG flash activity. Granted, we do not presently have a way to monitor all conceivable electrical and magnetic activity in association with convective storms. Hence, the door remains open to speculation. In the absence of the capability to observe all possible electrical and magnetic activity, an influence presently unobserved could be operating. Since there is no capability to refute many such hypotheses, postulates of that sort remain outside the domain of science.

We should soon have the capability to monitor intra-cloud (IC) flash rates more or less continuously on a global scale (from satellites), as well as CG flash rates (from ground-based sensors) over most of the United States. It is certainly possible that this will reveal something special associated with tornadic storms, but I consider this unlikely. Virtually every attempt to relate lightning activity to tornadic storms has, to date, proven to be futile. As the capability to observe has improved, one after another of the early hypotheses has been discredited, only to be replaced by new speculation. There is no credible scientific evidence (as of this writing) that any unambiguous relationship exists between lightning activity and tornadoes.

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