Photo from NOAA
Summertime in Tornado Alley
Chasing Tornadoes with the International H₂O Project
June 2002
It's summertime in Tornado Alley and the weather weenies are out in force. From all over the world they've converged on the Southern Great Plains for a first-hand look at some severe storms—the ones that produce lightning, hail, enough rainfall to cause flash floods, and, of course, tornados. Many of these people are amateurs, hoping to spot twisters for the sheer thrill of it. But the several dozen researchers associated with the International H₂O Project< (IHOP)—touted as the largest field experiment in atmospheric science ever conducted in North America—are here for a different purpose. They want to understand the nitty gritty of how storms form, the phenomena that occur on a scale too small to be detected by fixed weather stations.
With an armada of cars, trucks, and planes at their command, each vehicle fixed with instruments to measure temperature, pressure, wind speed, and moisture, these researchers hope to take snapshots of the atmosphere while storms are brewing. They'd like to figure out why an atmosphere that looks ripe for a thunderstorm sometimes won't produce one. And why small storms that shouldn't produce tornados sometimes do. Ultimately, the data they collect will help them figure out how to forecast severe storms more accurately.
Join writer Dana Bauer, traveling with Penn State meteorologists
Paul Markowski and Yvette Richardson and the rest of the IHOP team as they follow the trail of storms across Oklahoma, Texas, and Kansas.
Dispatch 1: Hurry Up and Wait
Credit Dana Bauer
Flat land and blue skies in Oklahoma
The wind blows from the south like a steady gust from a blast furnace.
The red terrain, flat and featureless, can't divert it. The few trees that inhabit the landscape lean permanently to the north. The sky, bright blue and stretching endlessly behind a Philips 66 gas station and a crumbling diner called the Outpost, doesn't promise much of anything.
But a dryline—an invisible boundary line between dry air from the southwest and moister air from the east—is setting up very near to us outside of Guymon, in the Oklahoma panhandle. The formation of this dryline, and its slow eastward movement, might be enough to spark a storm.
But a dryline—an invisible boundary line between dry air from the southwest and moister air from the east—is setting up very near to us outside of Guymon, in the Oklahoma panhandle. The
formation of this dryline, and its slow eastward movement, might be enough to spark a storm.
"Geek Mobile" is what we call this car. Officially, it's Probe 8, one of a dozen or so vehicles in this afternoon's deployment. The parking lot is full of similarly tricked-out cars and vans.
We're waiting for instructions from field coordinator Erik Rasmussen, a research associate at the National Severe Storms Laboratory (NSSL), one of the lead institutions—along with Penn State, the University of Oklahoma, the National Center for Atmospheric Research (NCAR), and several others—involved in the International H2O Project (IHOP).
Rasmussen's job is to orchestrate the movements of seven probes, four radar trucks, two research aircraft, a balloon-launching truck, and a camera truck. He does it all from a captain's chair in front of a huge Unix computer inside a big white van called FC, for Field Coordinator. I can see FC on the other side of the parking lot, its antenna raised. Rasmussen is downloading the latest radar images from the computers at the National Weather Service Headquarters, about 280 miles to the southeast in Norman, Oklahoma. Those images will show him the exact location of the dryline. Rasmussen's plan is to set up our radars at the corners of an imaginary box 12 miles on each side, through which the dryline will pass. He hopes. The other vehicles will canvass the area inside the box,collecting data across the boundary as it moves.
Credit Dana Bauer
"Geek Mobiles" ready for action.
Rasmussen's voice—a bit high and tight over the radio—reveals his excitement. He's urging us to stay close to our vehicles so we can hear his messages: "We'll be leaving in the next 10 minutes, as soon as we get the latest information from Norman. Be ready to go." I can see FC lowering its antenna.
Twenty minutes pass. Rasmussen gives another warning not to leave our vehicles. A few stragglers run from the gas station with chips, sodas, and packages of Little Debbie Snack Cakes.
Finally, Rasmussen begins calling out coordinates, and we're off in all directions, each vehicle to its assignment. I'm in Probe 8. Our mission: to traverse the dryline on a country road along the Texas-Oklahoma border.
Dispatch 2: Slaves of Data Collection
It's 3:45 on a hot, dusty Wednesday and we've been cruising back and forth along the same 10-mile stretch of road for over two hours. A few puffy cumulus clouds have formed along the dryline, but my novice eyes can't detect signs of a storm brewing.
Credit Dana Bauer
View from Probe 8 on the long road nowhere
Four of us are riding in Probe 8, our geek mobile. Scott Axelson, a recent graduate of the University of Oklahoma, drives with one arm resting on top of the wheel. Andrew Philpott, an undergraduate from
Bates College in Maine, mans the laptop computer that collects and displays the data gathered by the instruments on top of the car. Ben Sipprell, a Penn State undergraduate, sits in the back with me, taking notes and handling radio communications.
Our mission is to collect data such as dew point—a measure of moisture in the air—and temperature on both the moist and the dry sides of the dryline. Part of the trick is to find the boundary. Change in dew point is the key. Philpott tracks the graphs on the laptop and tells
us when the dew point starts to rise, first slowly and then in small jumps. Sipprell explains that the distance over which the dew point changes is called a moisture gradient, and that the dryline is somewhere on that gradient. As that distance gets shorter, meteorologists like to say that the moisture gradient is tightening. More often than not, this tightening will result in a storm. Not always, though. The IHOP team hopes that the data it collects will reveal why the process seems to be hit or miss.
Earlier, Penn State professor Paul Markowski had explained to me why our mobile fleet is so important to finding out what happens along the dryline. "The weather stations operated by the National Weather Service are separated by well over 100 miles," he said. "But moisture gradients can occur over just a couple hundred yards, or less. Vehicles really help in getting ground truth measurements." While the planes collect data in the clouds, and the radars scan the entire field from the four corners of our imaginary box, the cars are in the trenches, gathering information right where the action is. And on days like this, when storms don't form, the teams of students in the cars must be diligent. As the afternoon wears on and the supplies of sugary snacks dwindle, they must keep plugging away.
Credit Dana Bauer
Ben Sipprell studies all things meteorological
Voices crackle over the radio. "The dryline has moved. Should we head east to hit it?" asks the team in Probe 6. A plaintive voice from another probe asks to stop for gas. Eric Rasmussen, our field coordinator and consummate radio cheerleader, calls out encouragement: "Hang in there guys. We're getting good data."
Several of the students involved in IHOP are part of a program sponsored by the National Science Foundation. Called Research Experience for Undergraduates (REU), this program brings undergraduates from all over the country to a host institution to experience first-hand how basic research is carried out. In 1995, while he was an undergraduate at Penn State, Markowski spent ten weeks as an REU student chasing tornadoes in Oklahoma. He worked with Rasmussen on a project called VORTEX, Verification of the Origins of Rotation in Tornadoes Experiment. That summer, Markowski discovered how thrilling research could be. His excitement carried him through graduate school at the University of Oklahoma and into a faculty position back at Penn State. The REU students this summer are on a different, and perhaps less sexy, mission, but Markowski still hopes a few will be sold on the research life.
In Probe 8, we've begun to tick off the familiar landmarks on our leg. The Beer Barn at the intersection of route 83. The Texas welcome sign: "Drive friendly. The Texas way." A cluster of cows behind a twisted wire fence. An abandoned Sante Fe train car. The Beer Barn at the intersection of route 83. I can't help but fall asleep.
At 7 p.m., Rasmussen calls it quits, and the armada heads back to the Super 8 Motel in Woodward about 120 miles to the east, our home base for the next couple of days. Even though we didn't see any storms, Rasmussen seems thrilled at the day's run and praises several of the probe teams for doing an excellent job. Later that night, I discover that a graduate student in one of the probes had a fit of temper during the day's mission and demanded to be dropped off at a gas station. Evidently misinformed about our objective, he couldn't understand why we weren't gunning it across the panhandle in hot pursuit of tornadoes that might have formed several counties away.
Dispatch 3: Using Bugs to Track the Storm
It's a Friday at the deserted municipal airport in Shamrock, Texas. I'm sitting in front of a computer in the cab of the SMART (Shared Mobile Atmospheric Research and Teaching) radar truck. The eight-foot-diameter radar dish, mounted on a pedestal attached to the truck's trailer, is pointed northwest, sampling a 140-degree swath. It sends pulses of energy into our sampling field that bounce back, or reflect, when they hit solid targets—everything from raindrops to airplanes.
Credit Dana Bauer
SMART radar scans the field in eastern Texas
On the monitor, I can see neat green lines where air streams form a triple point: hot dry air from the west joins warm, moister air from the south, and cooler air from the north. These lines are actually formed by great hosts of insects, buoyed by converging air streams and recorded by the radar as areas of high reflectivity. The bugs reveal the location and movement of the fronts.
The SMART radar sits at the southeast corner of an imaginary box formed with three other radar trucks. Field Coordinator Erik Rasmussen is guessing that the converging fronts will pass right through the approximately 150 square miles of territory we've staked out. By late afternoon, as the ground temperature rises and our anticipation grows,
we're hoping to see some "CI," as the researchers call it. Convective initiation. Clouds billowing upward, lightning, precipitation. The works. "So far, we've racked up the no initiation cases," says Paul Markowski, assistant professor of meteorology at Penn State, who is traveling with the SMART radar team today. "It's time for a storm."
Collecting meaningful data will be a big challenge. We're trying to trap a moving target. Will the clouds burst in our box or two miles away? The whole armada may have to redeploy several times throughout the day, and while it's easy enough for the geek mobiles to change position, it's a little more difficult for the radars. It takes about half an hour for the SMART truck to set up and start scanning. Steel plates must be placed on the ground so that the trailer's extendable feet don't sink into mud. The dish must be raised. Scanning coordinates must be entered into the computer.
The SMART Radar was designed and built by Jerry Guynes, an electrical engineer from Texas A&M University. He bought the pedestal, once used to mount World-War-I guns, from a military surplus store. The mobile unit is incredibly sturdy; it survived Tropical Storm Gabrielle near Venice, Florida last September. However, Guynes has yet to construct a protective cover for the steel dish, making it vulnerable to the quarter-sized (and larger) hail that storms on the Great Plains can produce. So Guynes, who is here to operate SMART radar for the IHOP team, warns Markowski that he wants to be on the road heading to safety before the weather gets serious.
Dispatch 4: Finally! The Clouds Burst
Jerry Guynes and I are sitting in lawn chairs in a field near the SMART (Shared Mobile Atmospheric Research and Teaching) radar truck waiting for the clouds to unroll. Paul Markowski, assistant professor of meteorology at Penn State, is watching the sky and pacing. It's late afternoon and we're sweating in the hot sun. The clouds are gathering in front of us.
Field coordinator Erik Rasmussen sends a message over the radio to change position. The cold front is moving rapidly to the east and we need to move our sampling box. It takes us 20 minutes to pack up and drive about a mile down the road. As soon as we start setting up in our new position we get another call to redeploy. As we pack up for the second time I can see huge clouds billowing upward in the distance.
As we drive east, we hit a wall of rain, then hail. Rasmussen suggests that we drive west to get away from it and instead the worst of the storm slams us. Dime-sized hail bounces off the windshield. Guynes, concerned about damage to his radar dish, takes refuge under a bridge. Later, some of the students in the geek mobiles tell me that they saw the clearly defined hail column from miles away. The hail continues for several minutes. After it subsides, Rasmussen must coax Guynes out from under the bridge. The radar dish survives unscathed.
As the armada retreats to Norman we encounter torrents of rain and blinding cloud-to-ground lightning. The visibility is poor and I understand now that driving home in a severe thunderstorm is definitely the most dangerous part of this kind of fieldwork.
Funding for IHOP 2002 is provided by the following agencies: National Science Foundation (NSF), National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), Department of Energy (DOE), Department of Defense (DOD), University of Hohenheim (Germany), National Weather Service (NWS), Bundesministerium für Bildung und Forschung (BMB+F, Germany) and the Deutsche Forshungsgemeinshaft (DFG, Germany), CNRS Service d'Aéronomie (France) and Canadian Foundation for Climate and atmospheric Sciences (CRCAS, Canada), For additional information, please contact Dave Parsons (parsons@ucar.edu; 303-497-8749) or Tammy Weckwerth (tammy@ucar.edu; 303-497-8790) or go to the IHOP 2002 Web site.