Browning was able to narrow the field of view, surmising that the vast majority of tornadoes, especially violent ones, emerged from supercells. But in his time, the tools didn’t yet exist to limn the difference between a nontornadic supercell, and the type whose rotating winds will reach the surface.
To that end, tornado science’s biggest breakthrough would come with the arrival of Doppler radar in the 1970s. Since 1953, it had been known that tornadic storms create a unique image on radar called a hook echo—so named because the radar picks up the arc of rain or hail that wraps around a strong mesocyclone. But before the arrival of Doppler radar—an advance that allowed radar to track movement in real time—meteorologists were unable to learn much about the supercell’s evolution or internal structure.
The first Doppler scan of a tornado would leave little doubt about just how much the technology had to offer. Like most advances in the field, it came about only with a rare alignment of chance elements. Throughout the sixties and early seventies, a small number of Doppler weather radars had started dotting the states, but it took until May 24, 1973, for a recordable tornado to form and touch down within range of any. That day, researchers at the National Severe Storms Laboratory in Norman, Oklahoma, noticed the first signs of a broad vortex forming several miles off the ground, and just within range of their Doppler. They scrambled to record its every moment—as the circulation focused, touched down, and marched six miles through the open country into nearby Union City. Their scan, of an entire tornado from birth to death, was historic—but the fruits of their labor took several more months to reveal themselves.
In the aftermath, researchers Rodger Brown, Donald Burgess, and Les Lemmon at the NSSL pored over every angle, every azimuth, on the magnetic tapes that recorded the day’s radar feed. When they struck upon a place where wind shear and velocities spiked over a short distance, they assumed they had found an error in the data. At that moment in the storm’s evolution, there had been no tornado on the ground; the increase in wind speed should have been smooth and gradual. Yet even when they checked different elevations, the same steep velocity gradient persisted. The researchers consulted the photographs taken from the field at the same time and identified a small funnel protruding from the cloud base, not yet in contact with the ground. In fact, it would be another forty-one minutes until touchdown.
What they’d stumbled across was no error. Their device had identified the first embryonic stages of a tornadic storm. In the race to warn those in the path, this was monumental. It meant that Doppler could reveal areas of concentrated rotation a few kilometers off the ground, a pattern detectable tens of minutes before touchdown. In the coming years, Doppler and follow-on advances would spread like wildfire across the meteorological community. While not all tornadoes produced visible radar signatures in their infancy—and not all signatures resulted in tornadoes on the ground—forecasters finally had some way of peering into the storm and spying a brewing tornado prior to its arrival. In the long history of tornado science, researchers could finally boast a clear victory over the vortex.
* * *
Through the thunderstorm, to the supercell, to the first spiraling wisps of the nascent twister, scientists had chipped away, steadily earning their insights. Yet as the field tried to isolate and discern the features of the funnel itself—What made the vortex descend? What determined its strength, or how long it would churn?—the tide suddenly turned.
Around 1980, after decades of scientific progress, the tornado seemed to set in its heels. At the lowest elevations—what’s referred to as the boundary layer—the twister refused scientists any further victories.
Tornadoes were such an improbability in the first place, such a miraculous confluence of variables that the trigger might be as inscrutable as chaos theory, and the beating of a butterfly’s wing. Vastly more data would be needed to detect any pattern. Doppler had proven its ability to capture in unprecedented detail the life cycle of a storm—but it had serious shortcomings. It struggled to capture the near-surface parts of the storm that scientists most prized. Unless a radar installation was practically run over, trees, houses, even the curvature of the earth, would conceal the vortex—to the point where scientists weren’t able to discern whether the wind was stronger near the surface or farther up. The boundary layer proved too low for the beam to reach.
It did not help that the technology was wholly reliant on chance encounters. Any particular spot in the country will meet a tornado, on average, once every 4,000 years. The odds were disconcertingly long that one would land within close range of a set of stationary meteorological sensors. By stringing mesonet instrument stations across the Oklahoma prairie through the sixties and seventies, the National Severe Storms Laboratory was able to improve the long odds. And the right storm in 1973 did yield its groundbreaking Doppler data set. But the run-ins were painfully rare, and storms that hit could be even more agonizing than those that missed: In 1977, when a tornado finally touched down near a site in Fort Cobb, it got too close. The site’s sensors were not designed to withstand tornadic wind speeds, and no useful data could be gathered.
Finally, there were a vast number of questions that Doppler would never be able to answer. The technology could say nothing about the temperature, humidity, or pressure inside the tornado. These are the fundamental data points of meteorology—what scientists consider essential to knowing where the wind will go, where it comes from, and what exactly is driving it. No fine-grain predictions of tornadic behavior would be possible without them.
Yet even as Tim Samaras takes SKYWARN classes and trawls Last Chance, these same basic questions remain unanswered. Upon reaching the unknowns at the tornado’s lowest levels, the science stumbled and sputtered.
A new tool, the next breakthrough, was needed.
In 1979, Dr. Al Bedard, a scientist at NOAA’s Wave Propagation Lab in Boulder, Colorado, knew it was time to risk a more daring approach. A stationary weather instrument wasn’t ever going to glean enough data. So while attending an after-hours party during a NOAA conference, Bedard approached Dr. Howie Bluestein, a member of NSSL’s Tornado Intercept Project, with a long-shot idea he’d been considering. Bedard had been developing hardened instruments for taking atmospheric measurements at airports, instruments that could hold up to a direct hit. But what if, he asked, he were to incorporate some of these same instruments into a mobile package instead? Such an “in situ” probe wouldn’t have to wait for the tornado or fight the 4,000-year odds. Imagine a portable twister laboratory engineered specifically for the chase. If he built such a thing, Bedard wanted to know, would Bluestein be interested in deploying it?
Bedard didn’t need to belabor the importance of such a new tool. It might have been half-raving, but Bluestein signed on to the endeavor. So the next evolutionary leap in tornado research—or perhaps its most frustrating period of all—got its start over cocktails.
By 1980, Bedard had constructed the instrument package: it was an ungainly cylinder roughly the size of an oil drum, made of half-inch-thick aluminum plate. The Totable Tornado Observatory would house sensors for measuring pressure, temperature, humidity, and wind speed, hardened enough to withstand velocities exceeding two hundred miles per hour. Because deploying in the path of a tornado was bound to be a frightful experience—and Bedard did not intend to deploy TOTO himself—he sought to make the process as foolproof as possible. Lying horizontally in the back of a pickup, the sensors would remain inactive. But as soon as TOTO was upright and winched down a ramp into place, the battery would kick in and its sensors would start recording.
In preliminary field trials in the summer of 1980, Bluestein tweaked the hardware and improved on Bedard’s deployment technique, until he could unload TOTO in roughly a minute. Then, in 1981, scientists at NSSL and the University of Oklahoma started chasing storms. They used a government van with TOTO’s bulky frame strapped down in the back. In an era predating cellular networks, Bluestein fed quarters into pay phones for storm
updates from NSSL. When it was showtime, he chased by sight and chose his deployments carefully. They only had one chance, one probe, after all; and TOTO required relatively firm, level surfaces. Mindful of potential sources of debris that could strike the instrument, Bluestein was also conscious to avoid barns and trees.
For three consecutive seasons he chased, with success always just out of reach. In 1982, he was racing to get ahead of a fast-moving storm when he realized he was on a collision course. As he began to turn back, the tornado roared into view, snatching telephone poles out of the ground and flaying a nearby mobile home. He’d gotten close, but too damned close to deploy. During one infuriating chase, he pursued a tornado sitting over Altus Air Force Base in southern Oklahoma. Before the team could get into position, the tornado lifted without warning. This wasn’t that unusual; the storm seemed to be producing twisters cyclically, so Bluestein continued ahead to where the next was likely to drop. We’ll get this one this time, he told himself. But instead of the usual southwest-to-northeast track, the new tornado darted off to the northwest, eluding TOTO. “It was teasing us,” Bluestein laughed. “Catch me if you can!”
By 1983, Bluestein had begun to despair. Short on hope and long on frustration, his group had TOTO tested in a wind tunnel at Texas A&M to calibrate its sensors and to determine its tip-over threshold. The results weren’t terribly encouraging. Unless anchored or widened, a hundred-mile-per-hour gale would upend the top-heavy cylinder—the kind of wind you’d see in even a moderate tornado. By the end of the season, Bluestein turned TOTO over to other scientists at NSSL. After years of close calls and frustrating misses he was finished with this dangerous game.
For all the long miles logged, the device got tantalizingly close only once. Near Ardmore, Oklahoma, the following year, the NSSL team deployed TOTO on the outer edge of a weak tornado. The instrument promptly pitched over onto its side, damaging the sensors.
In every sense, Bluestein felt as though they had been tilting at windmills. The Totable Tornado Observatory was retired for good in 1987. “I said, ‘I give up. Forget it,’ ” Bluestein recalls. “There are easier ways to do this.’ ”
The way he chose was mobile radar, which had become increasingly viable and cost-effective in recent years. The upside was obvious: One could still get around the 4,000-year odds, but the intercept was no longer an all-or-nothing proposition. Bluestein could keep his distance and position a mobile dish anywhere near the tornado, rather than only in its path. It wasn’t a replacement for TOTO so much as another path altogether. “It would be fascinating to actually get inside the tornado and take a look around,” he said. “Since we can’t, we try to get close enough to aim our portable radar unit and measure the wind field in and around the tornado.” Later, after Dr. Josh Wurman proved that the larger, more powerful Doppler radar could be adapted to the road, Bluestein mounted a heftier dish to the back of a passenger van. Where stationary Doppler would scan from dozens of miles away, Bluestein could haul his antenna to within a mile of the storm. With it, he achieved one of the first major breakthroughs in years. F5 velocities had previously been inferred indirectly through photographic analysis and damage assessments. His mobile radar, hauled into range of the funnel, proved that tornadic winds were far stronger than scientists had previously thought.
As mobile radar proliferated, a string of new findings followed, from Bluestein, Wurman, and others. The new technology triggered a badly needed fertile period for the battered and bruised researchers. But the radar’s beam still couldn’t reach the place TOTO was designed to go, where the tornado and our world meet.
Even as the twenty-first century neared, there were no accepted theories for how tornadoes formed, for how fast the winds inside could blow, or for how far the pressure could fall inside the core. To demystify these questions, one further outfit, a multimillion-dollar expedition in the midnineties, made a final attempt to revive the dream of in situ measurement. Called project VORTEX, the mission had a grandness in scale and ambition not seen since the Thunderstorm Project, half a century before: it featured mobile atmospheric sensors and weather-ballooning laboratories, photography teams, armored aircraft taking in situ observations within thunderstorms, and a mobile probe unit on the ground. Bill Winn, a physicist at New Mexico’s Langmuir Laboratory, developed the probe, known as the E-Turtle. But this, too, in all its many miles combing the plains, failed to pierce the core. Throughout the mission, just one next-generation probe managed to get close to a violent tornado. It just missed—sitting 660 yards shy of the core.
Temperature, pressure, humidity—these measurements were all off-limits to mobile radar. They were essential to lingering questions about how tornadoes form and behave, and there was only one viable way to get at them. Even so, Bluestein was done with in situ probes; and few scientists seriously considered them anymore. They’d watched Bluestein’s and Winn’s efforts fail and wanted no part of this work. After decades of battle, the storm had won: it would keep its secrets—for now.
CHAPTER SIX
* * *
THE COWBOY SCIENCE
TIM SAMARAS MAKES himself a student of the TOTO project’s ill-fated history. He studies the strengths and flaws of its probe and the VORTEX mission’s successor. As he conceptualizes his own device, he becomes familiar with the names, many of them the world’s foremost experts, who have tried and failed to pierce the violent tornado core. He learns to look at the gargantuan odds calmly, resolutely. He is well aware that, apart from the little notice in Commerce Business Daily, the scientific community has largely given up on in situ probes.
But Tim is not of the scientific community. He’s simply a chaser—one who has seen monster storms and their consequences firsthand. Chasers such as Tim are often all-too-well acquainted with the human toll their quarry exacts; they’ll usually beat first responders to the scenes of horrific tornado disasters. Tim has witnessed the cost this past decade. He has also felt the spark of hope and purpose offered by working with Tatom’s snail. Now, Tim believes he can help in his own way. He sets out to design a probe that could make history.
In his world, wind is nothing more than air rushing from high pressure to low. It’s not so different from the pressure front of a blast wave. Tim’s career is largely a decades-long succession of discrete blasts—Patriot missiles, bunker busters, tons of ANFO, simulated jet-fuel-vapor explosions—each with its own distinctive waveform. Since the day he walked into Larry Brown’s office, Tim has been preparing, learning to capture each gusting shock. The sensors he uses are generally the same, and they should be perfectly adaptable to a tornadic flow field.
But the real puzzle, he finds as he sets to work, won’t be measuring the wind; it’ll be keeping the damn probe on the ground. Despite TOTO’s inelegant bulk, wind in the core can imbue even a 400-pound barrel with aerodynamic properties. If the tornado tosses Tim’s hardware like a Frisbee, it won’t matter whether his data-acquisition software is a work of art.
If the wing of an aircraft is the perfect form with which to harness aerodynamic force, Tim needs a shape that is its antithesis, an object that responds to an intense flow with something like the opposite of lift. The DRI team has recently been absorbed by the defense contractor Applied Research Associates, and someone at the larger shop must have experience with lift- and drag-resistant shapes.
Tim throws himself into probe research for much of 1998, mulling the conundrum and digging through the firm’s past contracts for inspiration. The work is nothing less than the full synthesis of his skills—the exact point where the test range meets the high plains. No one with Tim’s unusual background has ever shouldered the challenge of in situ probe design, much less its deployment. So the answer he finally strikes upon is one that is unlikely to have occurred to anyone but Tim.
Seven years earlier, Roy Heyman, an old-timer who consults for ARA, developed plans for an intercontinental ballistic missile launch vehicle whose shape could shed the shock wave of a nuclear device. Apart
from searing-hot radiation and fallout, the immediate dangers were the blast wave’s extreme drag and lift forces, which could cause the launcher to tumble and take flight. When air flows around an object, it bends and accelerates, reducing the pressure above the obstruction. If the mass of the launcher can’t overcome the intensity of the flow—which in an atom bomb’s shock front would be incredibly intense—you’ve got lift, just as with an airplane’s wing. Meanwhile, on the leeward side of the launcher, a wake forms due to the interrupted flow, creating suction, or drag. With higher pressures at the front and lower pressures behind, the blast wave would loft, push, and flip the launcher. This is the last thing soldiers manning an ICBM need.
The trick in Heyman’s design was to get the air to bend as little as possible—nothing more than a gentle deviation—which would minimize the wake and counteract the lifting force. Of all the cubes, polygonal blocks, and cylinders he tested, the humble cone proved the most obdurate. Or at least it did in theory; the project never made it past the first phase of development. For Tim, however, it presents a perfect blueprint.
If Heyman’s shape can survive nuclear war, surely, with a few tweaks, it can stand up to a plains twister. Tim adopts it as the basis for a design and moves on to the next problem.
The wind’s debris cloud, choked with all manner of terrestrial objects turned missile, will be equally life threatening to his probe. So, to play it safe, Tim decides on quarter-inch-thick mild steel for the shell. It has the benefit of being strong and easily machined, but it’s heavy as hell. This means that, unlike TOTO, his device needs to be fairly small. The instrument must be light enough for him to carry and deploy in a hurry without herniating a disc, yet weatherproof and tough enough to survive in one of the nastiest environments on earth. This combination creates a whole new set of engineering hurdles—aggravated by the fact that Tim can’t resist packing the thing to the gills with extra features.
The Man Who Caught the Storm Page 6