18 Miles

by Christopher Dewdney

  This would have been tabloid fodder except that one of the passengers was an English physicist and author. His detailed account of the incident in the prestigious journal Nature gave new credibility to a phenomena that had previously inhabited a mythic realm. Ball lightning turns out to be one of the most scientifically contentious of all exotic electrical atmospheric phenomena, even with hundreds of eyewitness accounts. In almost all of these reports, glowing spheres float above the ground and drift along at a walking pace until they disappear or, in some instances, explode.

  The British occultist Aleister Crowley was one such eyewitness. He had a close encounter with ball lightning one summer in 1916 while staying at a cottage on Lake Pasquaney in New Hampshire. Though not a physicist himself, his lucid account of the encounter would do credit to any scientist. He’d been caught outside by a sudden downpour and had rushed indoors to change into dry clothes as the storm raged outside.

  To put on my stockings, I sat down in a chair close to the brickwork of the chimney stack. As I bent down, I noticed, with what I can only describe as calm amazement, that a dazzling globe of electric fire, apparently between six and twelve inches in diameter, was stationary about six inches below and to the right of my right knee. As I looked at it, it exploded with a sharp report quite impossible to confuse with the continuous turmoil of lightning, thunder and hail . . . I felt a very slight shock in the middle of my right hand, which was closer to the globe than any other part of my body.

  A diameter of eight inches seems to be the norm for lightning balls, but that’s about their only regularity. They don’t appear to obey the normal laws of electrical physics. Like ghosts, they can pass through conductors (screens or metal doors) and non-conductors (glass windows, brick walls) without leaving any trace, though in 1944, when ball lightning passed through a window in Uppsala, Sweden, it melted a perfectly circular golf ball–sized hole in the glass. Sometimes, the balls float above the ground, meandering through the air, and at other times they seem to roll along surfaces. Witnesses say they emit a fainting hissing noise, “like a flaring match,” recounted one man. They also come in a range of colors — violet, white and pale blue, though mostly varying from red to orange to yellow. These kinds of inconsistencies are what make lightning balls so maddening for scientists. They defy categorization. How can the electrically charged plasma hold its perfectly spherical shape for so long? What exactly is happening inside them?

  Whistlers

  If you take an AM radio and tune it between stations you’ll hear static — little bursts of crackling noises, some faint, some louder. This is the sound of lightning from distant storms arriving in the form of the radio-frequency pulses, or radio signatures. They’re called sferics, and the faintest are thousands of miles away. But if you have a tuner that can receive VLF (very low frequency) radio signals, and you tune it between stations (there aren’t a lot of them), you’ll likely hear eerie descending whistles like the sound of bombs falling. These are sferics that have leaked out of the lower thermosphere and traveled along the magnetic field lines at the edge of the exosphere, 6,000 miles above Earth’s surface and back again. On their trip through the magnetized plasma in the exosphere, the sferics get dispersed, stretched out and arrive back at Earth in a series of descending tones instead of a single static crackle. Sometimes the same whistler will bounce back and forth, caught in the magnetosphere, the descending tones getting longer and fainter until the whistler dissipates entirely.

  Hail

  Upper atmosphere storm phenomena such as whistlers and pixies are marvelous, but they are irrelevant to us who must endure thunderstorms from beneath, here on the surface of the planet. We bear the brunt of nature’s fury, and as if wind, lightning and flooding weren’t enough, there are other dangers. The powerful updrafts within storm clouds that our pilot William Rankin experienced firsthand are also hailstone factories.

  Supercooled water combines with ice crystals in the cold heights of a storm cloud to form ice pellets. These ride downdrafts until they partially melt, but then updrafts shoot them back up into the cold zone where they freeze again. They then fall once more before hitting another updraft and acquiring another coat of freezing rain. This keeps happening until they reach a size that can no longer be held aloft by an updraft. Repeated cycling up and down through the storm cloud, where the hailstone freezes and melts, builds alternating layers of clear and milky-tinted ice. If you slice a hailstone in half, it has concentric growth rings, like a tree trunk.

  Updrafts can reach speeds of 100 miles per hour in a big storm, and golf ball–sized hailstones are not unheard of, smashing greenhouses and car windshields. A supercell updraft can be even more powerful. Hail can get dangerously large. On June 22, 2003, a two-pound hailstone, seven inches across, fell in Aurora, Nebraska. But the world record for the heaviest documented hailstone goes to a lump of ice that fell in Bangladesh in 1986 during a hailstorm that took the lives of 92 people. It was a shade more than 2.5 pounds. A single hailstone that size would be a hazard, but imagine a few thousand of these melon-sized chunks tumbling out of the sky. An umbrella would be useless, and you wouldn’t be safe even indoors. With a terminal velocity somewhere in the range of 105 miles per hour, they would easily smash through most wooden roofs. It would be like having a thousand major league pitchers hurling bricks at you.

  Even mothball-sized hail is not a good sign. Hail is the trademark of a truly violent storm; in a supercell thunderstorm, the hailstones fall thickest just before the leading edge of the mesocyclone, where a tornado is most likely to be. There’s a lot going on inside a cumulonimbus cloud, and ultimately hail turns out to be the least of it.

  “It’s a twister, it’s a twister.”

  Farmhand Zeke in The Wizard of Oz

  A funnel cloud is a surreal mixture of the apocalyptic, the beautiful and the demonic. Its spooky, serpentine shape panics some and mesmerizes others. Louder than a train or a jet engine, the roar of a tornado drowns out thunder. At night, they are even more ominous, sometimes glowing internally with continuous lightning like pillars of fire. What could be more cataclysmic, more threatening? Tornadoes are menacing, divine, capricious, unpredictable and wrathful.

  Mr. Tornado

  A world apart from Kansas is Fukuoka Prefecture in southern Japan, where, in 1920, the future expert on tornadoes Tetsuya Fujita was born. Fujita was impressive. The college he attended hired him as professor of physics as soon as he graduated in 1943. He was also lucky. Two years after he began his assistant professorship at the Fukuoka Prefecture college, on August 9, 1945, an American bomber carrying the world’s first plutonium bomb had to divert to its secondary target, Nagasaki, because of bad weather over the primary one — the city of Kokura in the center of Fukuoka Prefecture.

  He was one of those exceptional people for whom opportunity seemed to leap out from the heart of disasters. A few weeks after the bombing of Nagasaki and Hiroshima, the Japanese defense authorities enlisted Fujita to study the blast damage at the two cities. No one in Japan had any idea what type of weapon had caused so much destruction, and all sorts of conflicting theories abounded, including magnesium flares (to account for the brightness) and multiple blasts. Fujita made an extensive photographic record of the devastation and studied the images. From the pattern of nuclear flash burns on a bamboo vase, he proved that there had only been one bomb. He also analyzed the “starburst” pattern created by flattened trees and buildings surrounding ground zero and was able to estimate not just the size and power of the blast but also how high above the ground the weapon had been when it was detonated. (According to his estimates, the power of the bomb was stupendous, almost impossible for a single detonation. His calculations reinforced the Japanese decision to surrender.) The research Fujita conducted in Hiroshima and Nagasaki, a sort of reverse engineering of disaster, was vital, if heartbreaking, training for what ultimately became his life’s vocation.

  After the war, Fujita studied meteorology at T
okyo University. He was fascinated by storms, perhaps as a consequence of or metaphor for the apocalypse he had narrowly escaped, and he devised radical theories about the structure and behavior of violent storms. His conjectures were advanced for the time. He read work by the American meteorologist and storm researcher Dr. Horace Byers of the University of Chicago and realized he had a kindred spirit. Fujita sent his research papers to Byers, and the two began a lively correspondence.

  Then Fujita’s fluky good fortune struck again. Tornadoes are as rare as hen’s teeth in Japan, but one hit Kyushu on September 28, 1948, and Fujita was able to visit the debris zone almost immediately. What he discovered there was his destiny. All his training in engineering, physics and meteorology converged. He knew the load factors, the stress points, the mass and resistance of most man-made structures, so that he could deduce from a glance the scale of the forces that had acted to destroy the buildings and, from this, Fujita could reconstruct the tornado’s vortex.

  As soon as he was awarded his doctorate by Tokyo University in 1953 (his thesis was on typhoons), Byers invited him to work as a visiting research associate at the University of Chicago. He ended up staying and by 1955 had tenure in the meteorology department. The university sweetened the deal by purchasing a substantial brick house for Fujita and his wife, Sumiko, right beside the campus. Now Fujita could roll up his sleeves and work on mesometeorology: the study of middle-sized atmospheric phenomena such as storm cells and cyclones. But all this was prelude to his ultimate obsession: tornadoes. He became an armchair storm chaser, an academic sleuth of the tornado and of all the transient, yet indelible, traces of this capricious and terrible whirlwind.

  He poured over aerial photographs of tornado tracks, photographs of wreckage, impact pits on the earth (where solid objects had hit and then bounced back up into the air), broken buildings and tree branches, and he eventually produced detailed, hand-drawn tornado paths annotated with copious notes and numbers. He realized, after analyzing their paths, that single tornadoes almost never follow a storm for hours, but instead “families” of tornadoes form, dissipate and reform along the storm’s path.

  Fujita’s meteorological triumph came during the massive tornado outbreak of Palm Sunday, April 11–12, 1965. Forty-seven tornadoes raged across the U.S. Midwest, killing hundreds and injuring thousands. Fujita spent months examining the aerial and ground photographs to compile his usual, meticulous damage paths. But now he saw something deeper, something more complex about these paths. There were swirls within swirls. He realized that a large, single tornado is made up of multiple vortices, smaller tornadoes that are bundled together inside the larger one. Years later, he used films of this outbreak and others to estimate the wind speeds of individual tornadoes. With these figures, and with help from Sumiko, he devised his most famous contribution to meteorology, the Fujita scale, which finally calibrated the strength of a tornado.

  The original six-point Fujita scale runs from 0 to 5, where an F0 is a tornado with winds of 40 to 70 miles per hour and an F5 with winds of 261 to 319 miles per hour. An F0 might blow a few leaves off a tree and rattle a window or two, whereas an F5 leaves only stumps and empty basements. Armed with this scale and a completely fine-tuned system of debris assessment, he was ready for the Super Outbreak of April 3–4, 1974, when 148 tornadoes ravaged 13 midwestern states as well as striking southwestern Ontario.

  Here, alongside the complex patterns caused by tornadoes, he discovered something new — starburst patterns of fallen trees that could only have been caused by 150-mile-per-hour downdrafts. Fujita wrote later, “If something comes down from the sky and hits the ground it will spread out . . . it will produce the same kind of outburst effect that was in the back of my mind from 1945 to 1974.” He called these “downbursts” and “microbursts” and declared that there had actually been 144 tornadoes and four microbursts. (More recently, “plough winds” have been added to the arsenal of tree-snapping storm winds.)

  The pilot William Rankin directly experienced the cloud machinery that produces these downbursts during his 1959 freefall into a storm. It’s unlikely that he would have lived to tell his tale if he’d had the misfortune of being caught in a downdraft that ended as a downburst. He would have been dashed to earth, chute and all, at more than 100 miles per hour.

  Most meteorologists received Fujita’s downburst theory with skepticism, but he pressed on. It wasn’t until he analyzed an aeronautical cold case that his theory gained national attention. The case in question was a famous air disaster, the 1975 crash of Eastern Airlines Flight 66 at Kennedy Airport in New York. Going back over the records of weather conditions during the disaster, Fujita realized that a downburst had hit the airplane during its approach. He then went over dozens of previous airport accident reports and combined them with weather conditions at the time. The data confirmed his theory — more than 500 air-related deaths in the previous three decades had been caused by microbursts.

  Still, it took 14 more years before Fujita’s data was so overwhelmingly conclusive that commercial airports installed Doppler radars to detect downbursts and reroute flights. Countless lives have been saved since. In 1991, the Japanese government recognized his work, awarding him the Gold and Silver Star, one of the highest honors of the nation.

  Birth of a Tornado

  Tornadoes can strike almost anywhere, from downtown London, England to mainland Greece. The earliest recorded tornado struck Rosdalla, Ireland, on April 30, 1054, and the deadliest struck two adjacent towns in Bangladesh, Saturia and Manikgank Sadar, on April 4, 1989, killing 1,300, injuring 12,000 and leaving a further 80,000 homeless. The swath of destruction leveled every structure in an area of two square miles.

  Contrary to popular belief, tornadoes can strike near rivers, lakes and even mountains. In Yellowstone National Park, a tornado cleared a swath up and down the slopes of a 10,000-foot mountain.

  Tornado Alley — a corridor that stretches from central Texas north into Oklahoma, Kansas and Nebraska, then eastward into central Illinois and Indiana — is the world capital of tornadoes. Here is where the majority of the 800 tornadoes that strike the U.S. annually touch down. As elsewhere in the Midwest, tornadoes occur when cold, dry air from Canada collides with warm, humid air from the Gulf of Mexico. That’s a prerequisite for a lot of summer storms, but the essential element, the one that gives the twister its twist, begins hours before, under a sunny sky.

  The instigator of the tornado is wind shear — winds at different altitudes moving in different directions. On a clear, humid day, these opposing layers of wind are invisible. Long before the first storm clouds begin to take shape, wind shear creates a cylinder of air, hundreds of feet high and miles long that rolls along the ground like an invisible steamroller. This is a mild presentiment of what is to come, a ghost tornado, momentarily riffling your hair on a summer afternoon.

  This cylindrical, phantom tornado barrels along over fields and highways until it encounters a strong updraft that lifts one section of the spinning tube upward into the sky above the dew point. As the rotating tube rises into cooler air, a cumulus cloud begins to form around it — first as a wisp (a cumulus fractus), then as a puffy cumulus humilis that quickly inflates into a cumulus mediocris and then into an even larger cumulus congestus. In less than an hour, the cloud has become a giant cumulonimbus. Meanwhile, the rolling cylinder has been drawn up into the cloud’s core in a vertical, bent loop. As the cloud continues to rise, one side of the rotating loop disappears and the remaining piece dominates. The entire central portion of the storm cloud begins to rotate in the same direction as the dominant loop fragment. Half an hour later, the storm is a giant, supercell cumulonimbus incus with a mesocyclone at its heart.

  If you are watching a supercell approach from the ground, the most striking feature is the wall cloud: a two- to three-mile-wide disc-shaped cloud that projects beneath the rest of the storm. This is the visible part of the mesocyclone. It sits at the core o
f the storm and extends up for thousands of feet. The funnel cloud, if it forms, will drop down from the edge of this wall cloud.

  Tornadoes almost always travel from the southwest to the northeast, moving at just above the average urban speed limit — 35 miles per hour — but they have been known to move at twice that speed and as slowly as five miles per hour. They have been seen traveling in zigzag, circular or looping patterns. And then there are some that remain stationary. In South Dakota, a tornado once hung over a single field for 45 minutes. In a car, you can generally avoid them, although even the most seasoned storm chasers have been trapped while driving and then paid with their lives. And yet you can see why people chase storms or don’t bother to take shelter. What could be more thrilling than feeling the earth rumble beneath your feet as an F5 passes within less than a mile?

  On the afternoon of June 22, 1928, Will Keller, a Kansas farmer, saw a tornado bearing down on his home. He hustled his family into their storm cellar, but, as the tornado approached, he paused at the top of the stairs with the door still open. I can imagine him, transfixed by the immensity of the oncoming spectacle while his family begged him to shut the door and come down. But curiosity got the better of him.

  As I paused to look I saw that the lower end which had been sweeping the ground was beginning to rise. I knew what that meant, so I kept my position. I knew that I was comparatively safe and I knew that if the tornado dipped again I could drop down and close the door before any harm could be done.

  Steadily the tornado came on, the end gradually rising above the ground. I could have stood there only a few seconds but so impressed was I with what was going on that it seemed like a long time. At last the great shaggy end of the funnel hung directly overhead. Everything was as still as death. There was a strong gassy odour and it seemed that I could not breathe. A screaming, hissing sound came directly from the end of the funnel, which was about 50 or 100 feet in diameter, and extending straight upward for a distance of at least one half mile, as best I could judge under the circumstances. The walls of this opening were of rotating clouds and the whole was made brilliantly visible by constant flashes of lightning which zigzagged from side to side. Had it not been for the lightning I could not have seen the opening, not any distance up into it anyway.