Living in sunny Southern California, where it's 75, sunny and mild much of the time, kind of makes you forget that other regions experience this thing called "weather." The fact I moved here in the middle of a drought reinforced this notion of perfect year-round weather in my mind. But this year was a bit different: Los Angeles has been gray and drizzly for much of the winter/early spring. So, you know, we're suffering, too. It's just that "Drizzle-pocalypse" doesn't have quite the same ring to it as the "Snowpocalypse" that beset the Northeast earlier this year. Still, back in January, we were slammed by three major rainstorms back to back, severe enough to cause a small tornado in Long Beach, which hung around just long enough to pick up a sailboat in the harbor and drop it onto a nearby catamaran. Tornadoes are a bit like toddlers that way: "Watch me cause eerily targeted mayhem, just because I can…. Hey, wonder what would happen if I picked up this cow and dropped it into your kitchen, just for giggles???"
That was one of the memorable scenes in the blockbuster movie Twister (which I recently watched again while working out at the gym, since it makes regular appearances on cable TV). The storm chasers are hot on the trail of a twister, and a random cow wafts by their front windshield. ("We got cows!" became the hot movie quote of the season.) There's a lot of really cool science associated with tornadoes, and Twister did its part to ignite the public's interest in that science — something that real-life storm chasers have mixed feelings about. For one thing, average folks decided storm chasing looked like a fun hobby, completely misunderstanding how dangerous actual tornadoes can be. For another, the science depicted onscreen was, shall we say, not quite in line with the standard textbook science of tornadoes.
In fine Internet tradition, nerd gassers were quick to point out all the scientific errors in the film almost as soon as it came out. These include the fact that air and debris in a real tornado will be pulled into the twister, not out, so you wouldn't get that awesome scene where the 18-wheeler is tossed back onto the two-lane road, skidding ominously towards our plucky storm chasers. Also, Helen Hunt and Bill Paxton's hair should have been flowing forward, not back from their faces — except then how could we admire her classic bone structure and his ruggedly chiseled features?
Lightning and thunder don't flash/crash at the same time (light travels faster than sound, duh), and while it's true that tornadoes can change their path, but not as quickly and abruptly as depicted in the film. And while storm chasers do use the Fujuita-Pearson Tornado Intensity Scale to rank the power of such storms from F0 to F5, they can't look at their radar readings and immediately tell what a storm's ranking is likely to be — consider that one artistic license to keep the plot moving along. (One person complained that the hail in the movie looked as though it had been taken out of a hotel ice machine. Given the challenges facing filmmakers on location, it probably was.)
For all the nitpicking we can do over the science of Twister, there's no denying it works as fantastic entertainment. And at least one aspect of the science is drawn from reality: the sensor system known as DOROTHY. It's based in part on the TOtable Tornado Observatory (TOTO, after Dorothy's dog in The Wizard of Oz) developed by NOAA scientists a few years before the film was made. TOTO was little more than a metal barrel (painted white, or orange in later incarnations) pimped out with pressure and humidity sensors, as well as other weather instruments like anemometers. Just as depicted in the film, TOTO could be strapped to the back of a pickup truck and transported into the field where tornadoes might be brewing — ideally resting on a level, firm surface well away from wind and buildings or trees (or cows!), which filmgoers now all realize can turn into flying debris in a tornado's wake. Did we mention the increased risk of being struck by lighting, thanks to bringing a large metal container into open areas during a severe storm?
Small wonder TOTO never really saw full deployment. The closest it came was on April 29, 1984, during a field test in Oklahoma, except TOTO was sideswiped by a relatively weak tornado and toppled over because its center of gravity was too high to withstand even the milder forms of extreme winds produced by a twister. It had more success as a portable weather station to monitor regular thunderstorms, but by 1987, TOTO went into early retirement; it was just too large and cumbersome to maneuver quickly (and safely!) into the path of an approaching tornado. No real-world scientist is keen to meet the fate of Cary Elwes' conniving rival scientist, after all. (And yes, real storm chasers in the predicament of Hunt's and Paxton's characters at the film's climax would have been dead within 15 minutes.) You can still see TOTO on display at the National Weather Center in Norman, Oklahoma, though.
One way real storm scientists study tornadoes is by deploying "turtles": small, well-grounded sensor packets placed in roads every few hundred yards, in hopes that a tornado will pass right over them and yield a few more of its secrets. And last spring, scientists launched the largest tornado-chasing project to date: the Verification of the Origins of Rotation in Tornadoes Experiment, or VORTEX 2, for short. It's the second such attempt; the first took place in 1994 and 1995, and the data greatly expanded scientific understanding tornadoes. VORTEX 2 had its first phase last spring, and phase 2 is happening, like, right now. Those results will hopefully shed some light on things like the role temperature, wind speed, structure and shape each play over the course of a tornado's lifecycle. What do you get for the nearly $12 million price tag? You get some nifty unmanned aircraft to monitor storm cells, along with a gaggle of sensor-filled tornado pods designed to be dropped right in a twister's path. And of course, you'll have the old standbys: scientists driving mobile radar machines and "Doppler on wheels" — i.e., rugged trucks and vans lugging a bunch of expensive electronic weather monitoring equipment.
There's quite a lot of basic information readily available on the Interwebz outlining the fundamental science behind tornadoes, so I won't recap any of that here. But how about the unique damage caused by violent twisters, sometimes literally raising the roof off of a house, for example (and not metaphorically, a la P-Funk)? Well, one contributing factor is the Bernoulli effect, usually cited in simplified pop-sci explanations about how airplanes stay in the air due to pressure differences in the air flowing above and under the wings. (In reality — as some readers are no doubt aching to point out — the aerodynamics of flight is far more complicated, but for the average non-scientist, the Bernoulli effect is sufficient to convey the gist of the principle at work.) Basically, the Bernoulli principle connects the elevation, pressure, and speed of any fluid (which technically includes both liquids and gases). The technical definition in physics for pressure is force divided by area (and force in turn is determined by pressure multiplied by the area of the object, whether it be an airplane wing or a roof).
In the case of a tornado blowing the roof off a house, the high winds whooshing over the roof at high speed (say, around 260 MPH) creates a pressure difference between the inside and outside of the roof. Whether or not it's strong enough to raise the roof depends on whether that difference becomes great enough to cause "lift". Other factors that come into play include the overall weight of the roof and how securely it is fastened. This guy has actually crunched the numbers, and found that it's perfectly plausible for a tornado to raise the roof if it's not firmly anchored. And of course, once the roof lifts, the wind also blows in the space under the roof, equalizing the pressure, so it would come crashing down fairly quickly.
Incidentally, no, opening a window will not stave off such a disaster; that's a myth. Other myths that are best dispelled: (1) The safest spot during a tornado is the southwest corner of a basement. This is not necessarily true; it's usually the northeast corner, since the safest spot is whichever side or corner of an underground room is opposite the direction from which the tornado is approaching. (2) Taking shelter under a highway overpass is safe. Nope! It's actually a terrible idea, since the small area under the overpass creates a strong wind tunnel effect. In 1999, during a tornado outbreak in Oklahoma, the twisters hit three different overpasses and killed people each time. (3) Tornadoes can't cross major rivers or mountains. Alas, those wily storms can do both these things. Mocking an approaching twister from across a river is just asking for trouble.
Here's something you might not know about the science of twisters, though: they have a distinctive "voice." I'm not talking about the obvious rumblings of thunder, whooshing roars, the whistling of funnels, and screeching high winds. They also emit signals in the infrasound, just below the range of human hearing, and unlike the audible sounds — which you can really only hear if you're fairly close the storm — infrasound can travel great distances. Many acousticians specialize in designing sensors and other specialized equipment to isolate the infrasonic signals from tornadoes (as well as volcanoes, crashing waves, explosions and similar phenomena, all of which also produce infrasonic signatures). The aim is to develop better prediction and detection devices to give people more warning before a tornado hits. (Twister the film had that aspect right: people only have 13 minutes or less to respond and take cover when a tornado strikes.)
One of the scientists doing just that is University of Mississippi physicist Henry Bass, who told Discover magazine in 2007 that picking out infrasonic signals in tornadoes and hurricanes could provide "a way of supplementing the information available from satellites and airplanes," although he admits, "We don't know if it will work, but… [we'll] try almost anything." The Earth itself has a discernible "hum" as waves of energy flow through the crust, a phenomenon first detected in 1998 by seismic monitoring networks. In fact, infrasound might offer a plausible explanation for the belief that animals have some sort of "sixth sense" about approaching storms or natural disasters. Certain animals appear to be sensitive to infrasonic rumblings, such as elephants. Bioacoustics research Katy Payne (Cornell University) has studied elephants in the zoo, and way back as far as 20 years ago, she noted a kind of shuddering in the air around the animals, similar to the deep bass sounds emitted by a large pipe organ. She figured the elephants were making sounds just beyond the lower range of human hearing, in the infrasound.
Jen-Luc Piquant, in her Internet wanderings, has discovered something even cooler than the real-world science of Twister: quantum tornadoes! Tiny twisters measuring the width of a single helium atom that are usually invisible to the naked eye! Oh yes, the subatomic realm has its own version of a twister, in the form of quantized vortices, which can only exist in superfluids — or things that behave like superfluids, such as liquid helium, liquid crystals, Bose-Einstein condensates, and certain classes of superconductors. Researchers at the University of Maryland, College Park, chose to use liquid helium in their experiments with quantum vortices, which undergoes a phase transition to a "superfluid" state when it's cooled to below 2.17 Kelvin (i.e., colder than deepest space). These are prime conditions for quantum tornadoes to form, and if you spin the container that holds them, they assemble into a kind of lattice formation in response.
There's a catch though: those quantum tornadoes are generally invisible, since they're so tiny that most wavelengths of light don't reveal them. So the UMD scientists injected a bit of hydrogen gas into the rotating liquid helium, which froze to form tiny solid particles roughly the size of a red blood.
You know how laser light tends to be invisible unless there are dust particles in the air to reflect that light? It's the same concept here. Those solid helium particles got pulled into the vortex, and when laser light was shone onto them, it bounced off and reflected back to the video camera, revealing the vortices, which apparently look for all the world like strings of spaghetti that twist and tangle together when stirred. Left on their own, however, in a uniformly rotating superfluid, and they behave the way Richard Feynman predicted they would in 1955: they arrange themselves in a triangular lattice pattern.
Very little is actually known about the inner workings of these subatomic twisters, which is why the UMD scientists took real-time videos of solid hydrogen particles swirling around in superfluid helium, trapped in quantum vortices, and made what may be the first observations of so-called "Tkachenko waves" within the vortex. The name derives from Russian scientist V.K. Tkachenko, who first predicted in 1966 that when quantum vortices arranged themselves into that telltale lattice, the lattice would not be perfect. There would be tiny ripples (perturbations) that, when viewed from the side, would make the quantum tornadoes look as though they were swaying back and forth like seaweed — or a twister's funnel snaking gracefully across the sky. And that's just what the UMD scientists observed. The hope is that further analysis will shed some much-needed light on why bizarre states of matter like superfluids, BECs, and superconductors behave in such mysterious ways.