When I think of tornadoes, I think of…

. Twister, the movie

In "Twister," the movie opening today, stars Helen Hunt and Bill Paxton stand in an cornfield. whips their hair back and debris flies toward them as the husband and wife chasers, eyes keen, look in awe at a monstrous, growling, on coming tornado.

"My God," they say.

In a preview screening Wednesday, two real husband and wife tornado chasers, Richard and Daphne Thompson of City, were saying practically the same thing:

My... What a bunch of hooey.

It's not that the young chasers thought "Twister" was bad. Not at all. The special effects that created the tornadoes were great.

"The effects were better than I thought for the tornadoes," Richard Thompson said.

And in terms of excitement, Daphne Thompson, 23, who's an Internet WebMaster for the National Service, and Richard Thompson, 29, who tracks for the National Prediction Center, thought it was pretty intense, maybe ranking an F3 on the F0 to F5 tornado intensity scale.

But as for capturing tornado chasing -- or even to the physics of real tornadoes -- well, as Fred Ostby, chief forecaster for the , said after the movie, "I thought `E.T.' was more believable."

Consider:

1. In a real twister, air and debris whooshes in toward the tornado, not out, with debris, 18-wheel oil trucks, farm equipment, cows and houses being flung away. At the least, the stars' hair should have been blowing forward, not back.

2. and thunder? Check your physics books, Steven Spielberg (producer of the Warner Brothers film). They don't flash and crash at the same time. Light travels faster than sound, so lightning is seen before thunder is heard unless a storm is directly overhead. 3. Yes, tornadoes wander, alter their path and change in intensity, but they don't skitter back and forth across roads like jittery rabbits, take sudden U-turns or drop out of sunny and virtually windless skies.

Storms just don't move east, then west, then stop. "That's wrong," Richard Thompson said. They have relatively distinct paths.

4. Chasers don't check radar and whoop "Whooeee! We've got ourselves an F3!" as the movie suggests.

Meteorologists do use the Fujita-Pearson Tornado Intensity Scale to rate the power of tornadoes, from F0 (weak with light damage) to F5 (violent with incredible damage). "But we only determine the intensity rating after we look at the damage," Daphne Thompson said. "We can't look at it on Doppler radar and say, `Yes, this is an F3.' "

For instance, only after meteorologists viewed damage from the Hesston, Kan., tornado of 1990 and the Andover tornado of 1991 were they rated at F5 intensity.

Of course, moviegoers might call this nitpicking. But Ostby and the Thompsons say there's much more. For example, one town in the movie is hit without warning, on TV or otherwise.

"That would never happen," Ostby said. "One thing they seemed to have totally ignored is the tornado spotters."

Cloud formations also are wrong. And in the movie, storm predictions are constantly being fed from the National Severe Storms Laboratory in Oklahoma, while it's really the Storm Prediction Center in Kansas City that predicts tornadoes. The lab does basic research.

In addition, the movie's "new" tornado-predicting technology, which is dubbed "Dorothy" and contains hundreds of tiny plastic sensors to ride up the funnel to feed back data, isn't new. It's based on technology the weather service abandoned 10 years ago.

"Anyway, those little tiny plastic sensors would have been shattered by the big boards that were flying through the air," Daphne Thompson said.

Today, she said, chasers use "Turtles," squat sensor packs placed in the middle of roads every few hundred yards. They hope they have predicted the tornado's path well enough that the twister will pass right over the devices.

Which raises the final point:

Chasers don't get in the way of tornadoes, let alone drive a speeding van or stand 50 yards from one, as happens time and again in the movie.

"It's insane. Just absolutely unbelievably insane," said Richard Thompson, who has chased down 40 to 50 tornadoes. Daphne Thompson has chased about 30. "You would never even consider living through what they did," he said. "If it was close to real life, you'd be dead in the first 15 minutes of the movie."

In "Twister," Paxton and Hunt drive at more than 80 mph only feet away and directly parallel to a twister. When the tornado suddenly turns, they ram their car into a bridge abutment and hold on for dear life as the tornado, spitting debris, passes over them.

"I hope people aren't thinking that that's what we do," Richard Thompson said. "No one in their right mind would try to do that."

Of course, when it comes to scientific or historical accuracy, Hollywood has never pretended to be faithful. What did it matter, for example, that in the movie "Jurassic Park," all the dinosaurs came from the Triassic period?

The truth about chasing tornadoes, Ostby said, is that even with the best predictive equipment and training, it's still a matter of luck, timing and patience. The Thompsons sometimes drive 14 hours and hundreds of miles to be where they think a tornado might develop, but then come up empty.

"You can easily go out for a week and have nothing happen," Ostby said.

The Thompsons hope the public understands that. Because if they have any fears about "Twister," it's that the movie will spawn a migration by would-be tornado chasers who hope to capture some of the movie drama, just as shark hunters took to the seas after the movie "Jaws."

Already these days, real chasers have to contend with news crews and thrill-seekers clogging roads on their way to capture footage of tornadoes. With this movie, they can envision a bad situation getting worse. Richard Thompson recalls a set of 1991 storms in Oklahoma that drew a caravan 100 cars long.

"It was that bad," he said.

And that potentially dangerous: Although the vast majority of tornadoes cause little or no damage, they still can be deadly.

If there is one thing the tornado chasers liked about "Twister," it's that the movie also depicts the fierce force of the , obliterating barns, houses, even causing several deaths.

.

Storm chasing is broadly defined as the pursuit of any condition, regardless of motive, which can be curiosity, adventure, scientific exploration, or for news professions/media coverage.

A person who chases storms is known as a storm chaser, or simply a chaser. While witnessing a tornado is the single biggest objective for most chasers, many chase and delight in seeing cumulonimbus structure, watching a barrage of and lightning, there are also a smaller number of storm chasers who chase hurricanes.

Nature of and motivations for chasing Storm chasing is chiefly a recreational endeavor, with motives usually given toward photographing the storm and for multivariate personal reasons. These can include the artistry and beauty of views afforded by the sky and land, intangible experiences such as feeling one with a much larger and powerful natural world,[3] the challenge of correctly forecasting and intercepting storms with the optimal vantage points, and pure thrill. Pecuniary interests and competition may also be components; in contrast, camaraderie is common.

Although scientific work is sometimes cited as a goal, direct participation in such work is almost always impractical except for those collaborating in an organized university or government project. Many chasers also are storm spotters, reporting their observations of hazardous weather to the authorities. These reports greatly benefit real-time warnings with ground truth reports as well as by increasing the reliability of severe storm databases used in climatology and other research. Additionally, many recreational chasers submit photos and videos to researchers as well as to the for spotter training.

Storm chasers are not generally paid to chase, with the exception of television media crews in certain television markets, video stringers and photographers, and researchers such as a handful of graduate meteorologists and professors. An increasing number do sell storm videos and pictures and manage to make a profit, and a few operate "chase tour" services. Storm chasing tours in particular make storm chasing a recently developed niche tourism. Financial returns usually are relatively meager given the expenses with most chasers spending more than they take in and very few making a living solely from chasing.

No degree or certification is required to be a storm chaser. The National Weather Service does conduct severe weather workshops oriented toward operational meteorologists and, usually early in the spring, storm spotter training. History The first recognized storm chaser is David Hoadley (1938– ), who began chasing storms in 1956; systematically using data from area weather offices. He is widely considered the pioneer storm chaser and was the founder of magazine.

Bringing research chasing to the forefront was Neil B. Ward (1914-1972) who in the 1950s and 1960s enlisted the help of Oklahoma Highway Patrol to study storms. His work pioneered modern and made institutional chasing a reality.

In 1972, the in cooperation with the National Severe Storms Laboratory began the Tornado Intercept Project, with the first outing taking place on April 19 of that year. This was the first large-scale chase activity sponsored by an institution. It culminated in a brilliant success in 1973, with the Union City, Oklahoma tornado providing a foundation for tornado and morphology. The project produced the first legion of veteran storm chasers, with Hoadley's Storm Track magazine bringing the community together in 1977.

Storm chasing then reached popular culture in three major spurts: in 1978 with the broadcast of a segment on the television program In Search of...; in 1985 with a documentary on the PBS series Nova; and in May 1996 with the theatrical release of Twister which provided an action- packed but distorted glimpse at the hobby. Further early exposure to storm chasing encouraging some in the weather community resulted from several articles beginning in the late 1970s in Weatherwise magazine.

Various television programs and increased coverage of severe weather by the media, especially since the initial video revolution in which VHS ownership became widespread by the early 1990s, substantially elevated awareness of and interest in storm chasing. The advent of the Internet, in particular, contributed to a significant growth in number of storm chasers since the mid-late 1990s. A sharp increase in the general public impulsively wandering in their local area searching for tornadoes similarly is largely attributable to these factors. The 2007-2011 Discovery Channel reality series Storm Chasers produced another surge in activity.

From their advent in the 1970s until the mid-1990s, scientific field projects were occasionally conducted during spring in the . Then, the first of the seminal VORTEX projects occurred in 1994-95 and this was soon followed by field experiments each spring, with another large project, VORTEX2, in 2009-10.

Typical storm chase Chasing often involves driving thousands of miles in order to witness the relatively short window of time of active severe thunderstorms. It is not uncommon for a storm chaser to end up empty handed on any particular day. Storm chasers' degrees of involvement, competencies, philosophies, and techniques vary widely, but many chasers spend a significant amount of time forecasting; both before going on the road as well as during the chase, using a variety of sources for weather data. Most storm chasers are not meteorologists, and many chasers expend significant time and effort in learning and the intricacies of severe convective storm prediction through both study and experience.

Most chasing is accomplished by driving, however, a few individuals occasionally fly planes and television stations in some markets use helicopters. Research projects sometimes employ aircraft, as well.

. Green Skies

If the sky turns green during a , gather up your pets and other loved ones and head for the cellar, a twister is on the way. So goes the common wisdom in much of the central U.S.—and other tornado-prone in the world, like —when faced with a threatening sky (although some swear green means hail). Scientifically speaking, however, little evidence supports either the tornado or hail claims, though there is some evidence for green thunderstorms.

Over the past 15 years, a small group of scientists have weathered the elements working on green thunderstorms as a pet project, publishing a handful of articles in meteorological journals. All point to the existence of green skies with severe thunderstorms but no direct connection to tornadoes or hail can be made.

"Green skies are associated with severe weather," says physicist and occasional green thunderstorm guru Craig Bohren at Pennsylvania State University. "In areas where are common, they are said to be the cause of green storms. Or you will be told, often with considerable vehemence, that hail causes the greenness. Both explanations are easily refuted by observations."

The first question researchers faced: Is a green sky real, or just an optical illusion caused by light reflected off the ground and back up into the sky, as some green sky dissenters suggest? Frank Gallagher, now a for the U.S. Army at Dugway Proving Ground in Utah, tackled this issue for his thesis at the University of Oklahoma. He joined a tornado-chasing research team called VORTEX and recorded the wavelengths of light coming from storms in and Oklahoma using a spectrophotometer, a tool about the size of an old video that can measure the color and intensity of light.

Gallagher found that the dominant wavelength of light was green in several severe thunderstorms and that the color was independent of the terrain underneath the storm. As meteorology professor William Beasley, Gallagher's advisor at Okalahoma, put it, "[He] measured green wavelengths of light over a green wheat field and over freshly plowed fields with red-brown Oklahoma dirt."

Threatening green skies during a thunderstorm also proved entirely independent of the type of severe weather that came with it. Gallagher measured hailstorms where the dominant wavelength of light was green as well as hailstorms where it was the typical gray-blue color of thunderstorms. Tornado-producing storms proved similarly divorced from any particular sky color, other than dark.

Researchers remain undecided about the exact mechanisms that cause the sky to appear green in certain thunderstorms, but most point to the liquid water content in the air. The moisture particles are so small that they can bend the light and alter its appearance to the observer. These water droplets absorb red light, making the scattered light appear blue. If this blue scattered light is set against an environment heavy in red light—during sunset for instance—and a dark gray thunderstorm cloud, the net effect can make the sky appear faintly green. In fact, green thunderstorms are most commonly reported in the late afternoon and evening, according to Beasley.

In a paper published in the Journal of Applied Meteorology, Gallagher also suggested that green thunderstorms might occur more frequently than thought. Because it gets quite dark during thunderstorms, the purity of light may be too poor for observers to see the color on most occasions.

Other research on green thunderstorms is limited and not well funded. As Penn State's Bohren says, this is "not exactly a hot topic of research. Indeed, being curious about them can be hazardous to one's career." For example, his small grant from the National Science Foundation for the portable spectrophotometer Gallagher used was derided by then Speaker of the House Newt Gingrich's office and Richard Pombo, then a Republican congressman from California, who denounced Bohren in theCongressional Record. (Of course, neither politician hailed from ".")

. Tornado Alley

Tornado Alley is a colloquial term for the area of the where tornadoes are most frequent. Although an official location is not defined, the areas in between the and are the areas usually associated with it.

Tornado geography Though no state is entirely free of tornadoes, they occur more frequently in the plains between the Rocky and Appalachian Mountains. According to the storm events database of the National Climatic Data Center, Texas reports more tornadoes than any other state, though the very large land area should be taken into account. Kansas and Oklahoma are second and third respectively for sheer numbers of tornadoes reported but report more per land area than Texas. However, the density of tornado occurrences in northern Texas is comparable to that in Kansas and Oklahoma. Florida also reports a high number and density of tornado occurrences, though tornadoes there rarely approach the strength of those that sometimes occur in the southern plains.

Definition Though Tornado Alley is considered to be in areas of the , no official definition of the term has ever been designated by the National Weather Service. According to the National Severe Storms Laboratory FAQ, "Tornado Alley" is a term created by the media as a reference to areas that have higher numbers of tornadoes. Over the years, the boundaries of Tornado Alley have not been clearly defined, but the differences are the result of the different criteria used to define the . 90% of tornadoes hit this region of the U.S because cold, dry air from and the Rocky Mountains meets warm, moist air from the Gulf of Mexico and hot, dry air from the Sonoran Desert, which causes atmospheric instability, heavy , and many intense thunderstorms.

The most common definition of Tornado Alley is the location where the strongest tornadoes occur more frequently. The core of Tornado Alley consists of northern Texas (including the Panhandle), Oklahoma and Kansas. However, Tornado Alley can be also be defined as an area reaching from central Texas to the and from eastern to western Pennsylvania. It can also be disputed that there are numerous Tornado Alleys. In addition to the Texas/Oklahoma/Kansas core, such areas also include the Upper Midwest, the Valley, the Tennessee Valley and the lower Mississippi valley. The term "tornado alley" was first used in 1952 by U.S. Air Force meteorologists Major Ernest J. Fawbush (1915–1982) and Captain Robert C. Miller (1920–1998) as the title of a research project to study severe weather in parts of Texas and Oklahoma.

Variations The nickname "" is sometimes used for the areas in the southeastern U.S. – notably the lower Mississippi Valley and the upper Tennessee Valley. This region is particularly vulnerable to violent, long tracked tornadoes. Much of the housing in this region is less robust than in other parts of the USA and many people live in mobile homes. As a result, tornado related casualties in the southern USA are particularly high. One prime example was the April 25–28, 2011 tornado outbreak. The term was coined in 1971 by Allen Pearson, former director of the National Severe Storms Forecasting Center.

Impact In the heart of tornado alley, building codes are often stricter than those for other parts of the U.S., requiring strengthened roofs and more secure connections between the building and its foundation.[citation needed] Other common precautionary measures include the construction of storm cellars, and the installation of tornado sirens. Tornado awareness and media weather coverage are also high.

Some studies suggest that there are also smaller tornado alleys located across the United States.

Number of U.S. tornadoes per state These figures, reported by the National Climatic Data Center for the period between January 1, 1950 and July 31, 2009, show the ten most affected states. As reports are taken from individual counties within States, sometimes the same tornado can be reported more than once as it crosses county lines.

Texas: 8049 Kansas: 3809 Oklahoma: 3442 Florida: 3032 : 2595 : 2368 : 2207 : 2119 Mississippi: 1972 : 1844