What Stands in a Storm (7 page)

The technology now readily available to meteorology students and enthusiasts—from modeling software to online satellite and radar feeds—is remarkably similar to what the pros use. Johnny's hero, Jim Cantore, who taught a college meteorology course, marveled that his students were mastering many of the tools he used every day at the Weather Channel. In the span of his lifetime, how the tools had changed.

In the era before satellites, Doppler radar, and powerful computers,
meteorology was a relatively crude science. Before the end of World War II, researchers had little at their disposal besides intermittent observations and a few limited mathematical models based on idealized versions of real conditions. The idea of forecasting was still a pipe dream and the early prophets of weather prediction sometimes found themselves singing in the wind.

The first scientific inquiry into tornado forecasting met curious resistance. In the 1870s, John Park Finley, a farmer's son from Michigan, began what he called “a systematic study of the storms of the United States, especially those of a violent character, namely, tornadoes.” In his twenties, he was working at the US Army Signal Service (later renamed the Signal Corps) in Philadelphia, where he devoted his spare time to studying tornadoes. He compiled his findings in an elaborate report that was submitted and approved for publication, but then, mysteriously, lost.

The six-foot-three, two-hundred-pound young man with the handlebar mustache was not easily deterred. He got a break in 1879 when the Signal Corps sent him out to survey a disaster zone in the wake of a tornado outbreak in the Central Plains. Afterward, he suggested that a warning unit should be established in Kansas City, Missouri, to obtain weather reports and spread the word locally when conditions in the area were ripe for twisters. Subsequently, he gathered every known tornado report in the last century to look for patterns. Finley's 1882 report, “The Character of 600 Tornadoes,” was the most comprehensive treatise ever written on the matter and became the basis for his later forecasting efforts. He traveled throughout the Central Plains, enlisting more than 957 “tornado reporters”—the precursor to today's storm spotters. And he continued to analyze hundreds of storms, including a famous outbreak of sixty funnels that killed an estimated eight hundred people on February 19, 1884.

Once or twice a day throughout the stormy months of March and April, he specified when conditions were both favorable and unfavorable for tornadoes. “It requires as much, and often more, study to say
that no tornadoes will occur as to make the prediction that conditions are favorable for their development,” he wrote. (He could say that today and still be right.) When conditions were unfavorable, he was 99 percent accurate, but when he specified conditions favorable, tornadoes occurred only 28 percent of the time. Still, not bad for a relatively nascent science. And Finley's efforts to compare his forecasts to what actually happened were the beginning of what is now called forecast verification.

Unfortunately, at the peak of Finley's career, forecasting got political and a hot debate raged about whether the weather service should be under military or civilian control. Ultimately his superiors terminated his tornado studies in the late 1800s and ordered him to halt all predictions, discouraging use of the word “tornado” on the grounds that it would incite public panic—a harm they judged greater than injuries and damage inflicted by the storm itself. The word remained verboten for decades, and tornado research and forecasting fell into a dark ages of sorts until the late 1940s.

In 1945, the Thunderstorm Project began—a collaboration between the Weather Bureau, the Army Air Forces, the Navy, and the National Advisory Committee for Aeronautics (NASA's predecessor). World War II was coming to a close. Radar had been invented recently and, almost by accident, discovered to be useful for meteorology. As radar detected the presence of enemy aircraft and ships, military operators noticed signals irritatingly “cluttered” with weather echoes, but meteorologists saw the silver lining: radar made a mostly invisible phenomenon visible, providing something akin to a sonogram of a thunderstorm being born.

The Thunderstorm Project aimed to dissect a thunderstorm, inside and out. Trained military pilots flew directly into thunderstorms in twin-propeller fighter planes rugged enough to withstand the strong winds. Stacked five high every five thousand feet, the pilots penetrated a thunderhead over and over, and relinquished their controls to the mercy of the winds inside.

This science was not for sissies. No storm was to be avoided, no matter how large or violent it appeared. During the summers of 1946 and 1947, pilots participating in the study logged seventy flight-hours inside seventy-six thunderstorms. Planes were struck by lightning twenty-one times. But the pilots pulled off 1,362 storm penetrations without a single accident.

As the planes sliced through each storm, their instruments measured turbulence, updrafts, and downdrafts. Equipped with radars, the P-61C Black Widows also had transponders so they could be tracked from the ground as they passed through the storm. The cockpit instrument panels were continuously photographed, and evidence of pilots “flying” their planes in ways that might compromise the data meant that data would be thrown out.

While the pilots were getting buffeted around in the thunderheads, a two-mile grid of surface observation stations scanned the skies; weather balloons measured temperature, dew point, and wind speeds at different altitudes; ground radars tracked and monitored the thunderheads and guided the pilots through them; and radar-wind stations measured wind speeds. The result was a sort of meteorological MRI, a constellation of data that painted a vivid picture of the bowels of the thunderstorm.

Scientists at the University of Chicago analyzed the data by hand over the next three years—their findings on the life cycle of a thunderstorm underpin our understanding of severe-weather phenomena today.

A few years after the Thunderstorm Project, the first tornado forecast in the history of meteorology was made. It was also the first accurate one and was issued on Tinker Air Force Base near Oklahoma City on March 25, 1948. Until that day, tornadoes were considered to be an “act of God” (a phrase that still haunts today's homeowners insurance policies) and forecasting them was not regularly done.

Five days earlier, a large tornado—we don't know the rating because the scales used today did not yet exist—had struck the base only
eight minutes after it was spotted by a nearby airport. The funnel was lit up from within by lightning and stormed through the air force base, flinging aircraft, shattering the control tower windows, and
causing $10 million in damage (nearly $100 million in today's dollars).

The day after that storm, the base commander, General F. S. Borum, ordered two officers at the base weather post, Major Ernest J. Fawbush and Captain Robert C. Miller, to investigate thunderstorms to try to predict which are likely to produce tornadoes—and to give people enough advance warning to prepare or escape. The officers spent the next few days feverishly poring over weather maps, looking for patterns in the conditions that precede storms.

On the morning of March 25, Miller and Fawbush noticed conditions disturbingly similar to those leading up to that week's earlier tornado. The same surface lows hovered over the west-central plains. The dryline again lurked west of Tinker, inviting a warm, humid air to flow north from the Gulf and smother the base with a mass of muggy air, the jet fuel of thunderstorms. The atmosphere was unstable, with blobs of warm air rising rapidly through cool air above, like great invisible hot-air balloons. High up, the “balloons” encountered strong winds blowing in different directions, which caused them to spin like tops. The jet stream screaming through the upper atmosphere further enhanced the wind shear. Recognizing this pattern, the officers briefed the general that they thought the likelihood of tornadoes was high enough to justify a warning. The word “tornado” in a public broadcast was still avoided, but the general announced the beginning of a new era with his terse order:

“Do it!”

At 3:00 p.m. that day, Miller and Fawbush issued their warning to the base, sending military personnel into severe-weather mode as they braced for the storm's arrival, predicted between 4:00 and 6:00 p.m. Aircraft were moved to hangars, loose objects were tied down, and people prepared to retreat to safe places. At 6:00 p.m., as if following marching orders, the week's second large tornado struck the base, causing another $6 million in damage—but less than it would have without preparation.

This warning paved the way for a civilian program in the 1950s and beyond. Miller and Fawbush became pioneers in the field, creating the Air Force Military Warning System, a team that eventually forced the United States Weather Bureau to change its policy of forbidding tornado warnings and to create the Severe Local Storms (SELS) unit in 1953. It was the beginning of modern tornado forecasting.

The research meteorologist who would establish the field, Tetsuya “Ted” Fujita, a diminutive Japanese, came to the United States in 1953 specifically to study tornadoes. A professor at the University of Chicago, Fujita had meticulously surveyed the damage of the atomic bombs detonated over Hiroshima and Nagasaki. The starburst pattern in which trees fell in bomb-struck areas showed remarkable similarities to the trees downed by certain thunderstorms, inspiring his theory of microbursts, the sudden powerful downdrafts that could knock airplanes out of the sky.

Nicknamed “Mr. Tornado” among colleagues and friends, Fujita spent years walking the damage paths left by tornadoes, looking for patterns that might yield insight into their power and formation. He studied tens of thousands of photographs of tornadoes forming, frame by frame, a technique called photogrammetric analysis. His approach was unique, fresh, and often outside the established norms of meteorological research, and some members of the scientific community frowned on his unorthodox methods. Yet even his critics had to admit that he arrived at groundbreaking conclusions that evaded other researchers.

In 1971 Fujita developed the Fujita Scale, or F-Scale, which enabled scientists to categorize the magnitude of tornadoes through assessment of the damage they left behind. Using indicators of damage to vegetation and man-made structures, the F-Scale ranked tornadoes on a scale of F0 (little damage) to F5 (foundations of well-built houses swept clean of debris). In 1974 he spent hours flying over Alabama
and other states to study the tornado tracks of the Super Outbreak. This was “the pinnacle of his analysis of a tornado outbreak,” wrote one colleague. “For many of the 148 tornadoes, he was able to map the entire path in Fujita Scale-Intensity contours.” He also mentored a fresh crop of meteorology students who are among today's leaders, including Dr. Greg Forbes, the tornado expert at The Weather Channel, and Dr. Roger Wakimoto, who became the director of the National Center for Atmospheric Research.

Years after Fujita's death, the F-Scale was revised to better account for new variables such as the quality of construction of the buildings damaged by the storms. The Enhanced Fujita Scale, or EF-Scale, was adopted in 2007 by the United States (in 2013 by Canada) with the same basic six categories, EF0 to EF5. It is still in use today.

And April 27, 2011, the biggest of all—an EF5—was forming near Smithville, Mississippi—the second of four to strike the South that day.

As Johnny and Chloe sat in class at Smithville High, the atmosphere began recharging. The morning storms had wrung moisture from the air, depleting the storms of their fuel. The rain had cooled the air as it fell. These slight and subtle changes threw off the recipe for supercells, and the atmosphere relaxed, cleared, and brightened into a deceptive, menacing calm.

Now, as the midday sun heated the Mississippi River Valley, the ingredients were once again shifting into dangerously perfect proportions. The morning storms had left behind a wake of rain-cooled air, but that air began to warm in the afternoon sun. A slight high along the Gulf Coast had cleared the skies, sending sunshine in buckets and heating the land, which radiated heat into the low-lying air, which was thickening with moisture rising from the Gulf in hot vapors.

The winds were shifting favorably. The seventy-mile-per-hour winds at three thousand feet began to mix with surface winds. A gust front, the windy leading edge of a thunderstorm, rippled east through
northern Mississippi and Alabama. A low-level jet stream swooshed up from the south, nudging the blanket of muggy coastal air north, directly in the path of the gust front. As that warm air undercut the cold, dry air aloft, the atmosphere once again began to simmer with instability. Vast bubbles of warm air began to form, break free, and ascend. The pot began to boil.

West of Mississippi, the upper winds screamed northeast, sliding over slower-moving surface winds coursing northwest. This wind shear encountered a rising bubble of air, causing it to rotate. At the surface, surrounding air rushed to fill the areas of low pressure left by the rising blob, converging like water around a drain, but spiraling up, not down. The effect was like a spinning ice skater pulling in her arms until she became a blur. This rotating column of air—a mesocyclone—transformed into the most dangerous and powerful kind of thunderstorm on earth, spitting lightning within itself and onto the ground.