False color image reveals the path of a tornado through Joplin, Mo.

Through a tumultuous spring in which more than 1200 tornadoes ripped through the U.S., high-resolution satellite images illustrated the story of the destruction in painful detail. In Tuscaloosa, Ala., black-roofed houses stand next to the earth-colored remains of flattened homes, and in Joplin, Mo., a six-mile jagged line cuts across the southwest corner of town, a reminder of the most deadliest tornado to touch down in the U.S. in the past 60 years.

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These scars show the meandering course of a fickle destructor, and they raise interesting and still unanswered questions about how the brutal force of a tornado is unleashed—and we could be better prepared for them in the future.

What Can the Path of a Tornado Tell Us?

The satellite images after 2011's tornadoes all bear a brown trail of devastation that typically sweeps from southwest to northeast, following the winds of the upper atmosphere that push tornado-spawning thunderstorms in that direction. And just after a major storm, analysis of the images can help determine the best location for the center of assistance and recovery efforts.

But further analysis also provides insight into the specific behavior of the storm system, says David Stensrud of the NOAA National Severe Storm Laboratory. "[They show] the life span of the tornado, where it started, the time it started, how wide it got, whether there was one or more vortices."

We often think of meteorologists looking to the sky, but by comparing a tornado's ground trail with storm radar data, they can understand its atmospheric characteristics too. "The path can tell you how the tornado is related to the thunderstorm itself—how connected it is," Stensrud says. The twisters that are most connected to the main circulation of a thunderstorm are typically taller (some extending three or more miles into the atmosphere) and have a longer life span than shorter, less-connected ones. Though the latter can be just as dangerous if they hit the right spot, recognizing the connections between a storm's connectedness and destructiveness could help forecasters to better predict the trajectory and duration of future storms, and thus improve tornado alerts.

What Does the Heart of a Twister Look Like?

This May 24, as a violent tornado ripped through El Reno, Okla., a weather station on the ground there got an up-close look. As the storm's outer edge passed over the Oklahoma Mesonet site, it recorded a maximum gust of 151 miles per hour—the highest ever directly recorded by one of these on-the-ground stations—as well as the quick drop in atmospheric pressure that is the trademark of tornadoes.

Still, this isolated report—in which the Oklahoma station recorded weather conditions every five minutes—shows how far we are from having a complete picture of how wind speeds vary inside the vortex. "Getting data on tornadoes themselves is very, very difficult," Stensrud says. "We have mobile radars and other sensory equipment, but getting those instruments in the right places—in close—is dangerous business. We have limited information."

The scarcity of data on wind speed and direction on the ground, where homes and buildings and the tornado interact, presents a huge challenge to understanding precisely how tornadoes deliver their destructive force. Estimated wind speeds, for example, that researchers use to model tornadoes are typically based on the measurements taken 100 meters off the ground—far above the buildings the engineers are trying to protect. "Most of the research is on the meteorological side, on where and when tornado conditions can occur," engineering professor Panneer Selvam of the University of Arkansas says. "The more we can understand [on the ground], the more we can reduce the devastation and loss of life."

So while some scientists and storm chasers try to get more sensors closer to the heart of tornadoes, Selvam is trying to simulate the destruction. In his 3D computer models of a tornado's path, Selvam has simulated the effects of cyclonic winds on buildings at ground level. Curiously, the buildings in his models appear to slightly alter the tornado's translational speed, raising the question of whether a building could be designed to somehow turn away the approaching vortex. However, he says, these are tiny diversions only noticeable in a computer model, and—at least for now—the notion of a tornado-diverting building remains unimaginable. "The tornado is going to go where the tornado wants to go," Selvam says. "The shape of the building appears to have some influence, but it is very small."

However, his lab tests using curved cyclonic winds have also shown that the lift tornadoes exert on rooftops could be nearly twice what previous tests found when using straight-line winds. That means engineering rooftops against high winds is critical.

Can We Make More Buildings Tornado-Resistant?

Ultimately, when engineers look at the path of the tornado, the most telling factors are still the obvious ones: which kinds of buildings withstood the punishment without completely collapsing. The remains of this year's storms make clear that the technology to save lives is already within our grasp. Connecting the roof to the walls and the walls to the foundation with bolts and heavy steel—rather than relying on flimsy nailing plates and gravity—can make a big difference.

"The St. Johns hospital in Joplin that stayed intact," Selvam says, "That's an engineered building." Designed to handle extreme load conditions, engineered buildings are intended to overcome the most common structural failure points to prevent collapse. Though the windows on St. John's blew out and five people died—patients who lost power to their respirators—183 patients survived the storm in the hospital's interior hallways which remained structurally sound.

But three school buildings collapsed in Joplin, Selvam says, because they were not engineered with the same defenses. And to Selvam, that should be the lesson of the wild 2011 tornado season: American needs more engineered buildings. "What they need to come up with is an engineered building in each neighborhood, so that people can go and stay there. Maybe just the churches and schools. But some place where people in the community can go to seek shelter."

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