Greensburg, Kansas, May 2007
Image courtesy of Greg Henshall/FEMA
On that May evening when Umscheid was standing guard, two of the world’s most renowned tornado experts were separately traversing Kansas, hoping to get just such an intimate look. Lugging heavy radar and sensor equipment along the roadways, meteorologists Joshua Wurman and Howard Bluestein had been tracking the same volatile weather patterns all day. Former colleagues at the University of Oklahoma and both MIT graduates, the two men regularly crossed paths on the Great Plains and at conferences around the world. Acutely aware of each other’s advances, they built up storm-chasing fleets of ever-increasing capabilities.
Bluestein, the older of the two, is an avid photographer who has always been mesmerized by the uncanny beauty of tornadoes. These days the eclectic intellectual favors whatever works, be it collaborative numerical modeling or a hearty chase. Wurman is driven more by the taunt of the unknown and relishes extreme challenges. Spending most of the season as a nomad, doggedly pursuing storms with his team and sleeping wherever the weather takes him, he sees himself as the modern equivalent of the 15th-century explorers. “They were trying to find new continents. We are too, in our way,” he says.
A founder of the original group based in Norman, Bluestein prefers to restrict himself to brief sorties from this college town on days that show maximum potential. May 4, 2007, was such a day—on-screen at least. In reality, the macroscale data from the National Weather Service were not translating into dangerous circulations. Instead Bluestein and Wurman confronted a persistently blue sky until just before dusk. It looked as if neither scientist would get any closer to answering what they both regarded as the ultimate question, how is a tornado born?
The success of their mission depends, beyond the weather, on a technological brainchild of Wurman’s—the mobile radar truck. More than a decade ago he figured out how to chase and intercept nascent tornadoes with powerful, fast-scanning, full-size radar, a breakthrough that finally boosted the odds of catching these erratic phantoms. With the assistance of their Doppler on Wheels, or DOW, Wurman and his crew have amassed an unparalleled database: profiles of 141 tornadoes as of this season’s start. A DOW is a flatbed truck equipped with hydraulic feet to increase stability, a large radar dish that swivels when in operating mode, and an eight-foot antenna that sends out three-centimeter microwaves. When reflected back by rain, hail, airborne debris, or even insects, the waves create an image of storm activity and indicate wind velocity.
Every storm chase begins with an assessment of where supercells will burgeon, based on factors from the location of the so-called dry line—separating moist from arid air—to the speeds of upper-level winds. Supercells often appear in close proximity to one another and travel in groups. Because the cold air they emit interferes with the tornado genesis process, Wurman focuses on storms that are somewhat isolated from the advancing phalanx. When a supercell splits in two, as it often does, Wurman and Bluestein home in on the “right movers”—those that rotate counterclockwise, which tend to be more powerful. Yet there is still no guarantee that a tornado will form.
As the light faded that early day in May, Wurman’s forecasters were wondering if any clouds in driving range would even gather enough energy to achieve supercell status. Gradually his team edged northward, away from Greensburg toward a volatile on-screen patch that was turning up near the Nebraska state line. “I’m kind of worried that it’s a sucker play,” Wurman said, resigned to the idea that he was now playing a game of chance.
Bluestein, who earlier had been waylaid in southern Kansas for hours by a flat tire, characteristically decided to rely on visual cues. Peering to the southwest, he spotted a storm moving in. “It had a wall cloud, a flanking line, a back-sheared anvil, and an area of precip to the north,” he says. “It looked like a real supercell developing.” Bluestein and two graduate students had set up about six miles from Route 183, a north-south road bordered by grain fields and farmhouses. Drawing power from a portable battery, the X-band polarimetric Doppler radar mounted on the back of their truck scanned steadily. Now, to the amazement of this veteran storm chaser, the supercell began spawning tornadoes in sequence, a phenomenon known as cyclical tornadogenesis.
“It was beautiful,” Bluestein said months later, “just you and the storm. You could see the funnels coming down; they were illuminated by lightning.” Despite his battery’s being almost dead, he recorded “one of the most monstrous tornadoes I’ve ever seen on radar. It just kept getting bigger and bigger.”
At 9:36 p.m., as the mass of swirling air progressed northward at about 25 miles per hour, Bluestein and his team clambered into their truck to head home. Fifteen minutes later, one of the tornadoes they had intercepted rushed along Greensburg’s Main Street, swooping up the town and dropping it in mangled, splintered pieces. In its dying phase, the funnel most likely looped around and briefly retraced its path. Eleven people were killed, another 60 injured. It was the first-ever measured EF-5 tornado, the highest category on the Enhanced Fujita scale, and the most powerful since 1999, with an estimated peak wind speed of 205 miles per hour. The town of Greensburg was almost totally destroyed.
Carmen Renfrow was fortunate. She survived with her sister and pets and found her house almost intact. Not so John Haney. Down in the basement with his wife, he recalls, “You could hear every glass in that house break, and then you could hear the house leave. Then it got deathly quiet, and then we heard it again.” While Haney and his wife emerged uninjured, they later salvaged only enough belongings to fill the back of a pickup truck.
Within minutes, the radio announced news of the devastation. Driving back to Norman, Bluestein felt “kind of sick. You don’t like to hear that you’re out there doing something that’s fun and exciting and interesting—and that people are killed, that a town got wiped away.” Meanwhile Wurman, traveling near the Nebraska border, learned that Bluestein had intercepted the tornado of the decade. Intensely competitive and exhausted from his long day, he termed his miscalculation an “utter defeat.”
