Jun 9, 2009 08:00 AM
Editor’s note: Scientific American contributing editor Christie Nicholson is traveling with nearly 80 scientists conducting the largest tornado study ever completed. Check out her progress and learn about twisters on SciAm’s Twitter feed, and have a look at the photos she's taking along the way.
TOPEKA, Kan. (June 8, 2009)—When I arrived in Colby, Kansas last Thursday to join the VORTEX2 team’s nearly 160 scientists, students and media participating in the largest tornado-spawning storm study in history, the teams were despondent. The jet stream had been unusually displaced far to the north, resulting in one of the more calm seasons in decades. Even potential supercells—storms most likely to produce a twister—were conspicuously lacking.
With only one week left in this five-week study, the funding, resources and time spent were at risk of being for naught. Instead of having data to download in the evenings, students played catch in hotel parking lots.
Then it happened on Friday: A relatively large, long-traveling tornado touched down in an open area west of LaGrange, Wyo.
I was riding in a mobile radar truck called a DOW, for Doppler-on-Wheels, invented by Josh Wurman, president of the Center for Severe Weather Research and lead researcher of VORTEX2. At first, the tornado-spawning storm appeared unremarkable. Over the radio, Wurman told us to drive four miles south of Meriden, Wyo.
Then, a significant wall cloud formed under a wide, low-level circular cloud. Wall clouds are a good indication of a mesocyclone, the rotation required for most tornadoes. It looked like the sky had already formed a grey V with two pink skies on either side.
Minutes later the Storm Prediction Center announced a tornado warning for the area—a first for VORTEX2. Twenty minutes later our truck was in position just off highway 85, about 10 kilometers south of the core of the storm. The team lowered metal posts to level the truck, and started a radar scan.
That made it possible for Justin Walker, researcher at Center for Severe Weather Research, to confirm that the storm had strong rotation. Two of the crew jumped out, set up tripods, along with a photogrammetry team, which takes detailed photos and video to illustrate the storm from various distances, in order to complement the radar data.
Five minutes later, the radio brought the voice of field coordinator for NOAA’s National Severe Storms Laboratory: “Tornado genesis is imminent.” We were a significant distance from the storm, but waiting had made us anxious.
The radar showed a tight coil like a fiddlehead. Walker confirmed it: The wind shear was well over tornado strength.
“This is officially our first tornado of the season,” he said.
As we looked north across the unobstructed wide plain, a thin gray thread snaked down from below a mass of very dark cloud. As soon as the thread touched the ground, however, it grew thick, into what researchers call a stove pipe. “Wow, I didn’t think it would get that big,” said Anthony McGee, a student of photogrammetry at Lyndon State College.
We stood in the wind, up on a ridge, captivated. A few cars pulled over. Within about 10 minutes the massive V-shaped cone twisted into the heavy rain and disappeared. At least, it seemed to disappear, from our vantage point. Closer to the ground I heard later that the twister had become “rain wrapped,” making it even more visible, but only to those within one mile of it.
The tornado traveled for 25 minutes. We scanned for the duration, until we saw a long skinny tube appear against the dark sky. This was its end, known as the “roping out.”
“The really nice thing about this tornado is that it doesn’t look like it passed over any urban areas,” said Jacob Carley, a graduate student at Purdue University. “And I just heard [over the radio] that we got some really good data from this, so it’s a really good day for science.”
This was, in many ways, the cliché’d “perfect storm,” at least when it came to scientific study. First, and perhaps most important, was that the teams had enough time to get into position before the storm got exciting. Ten mobile radars, circle the storm describing winds typically about 120 meters above ground. An army of low-level instruments -- including about 40 anemometers, four distrometers (lasers that measure precipitation), and four balloon launchers -- are positioned various distances from the storm core. All instruments had access, meaning good roads from which to deploy. A windy road full of hills and trees is no good for tornado study.
Second, we had great visibility, with no rain or cloud obstructing the view of the funnel cloud, and later the twister.
Finally, the tornado lasted a while, traveling at 20 miles per hour for about 25 miles, when most tornadoes can last a mere five or 10 minutes.
It was an excellent case study, so a few days later, with a week left on the trip, the team is still thrilled. But they can’t lose momentum. “One data set is great, and we’re all very excited and happy about that, but it’s not enough, the number of grad students is such that we need several data sets in order to get enough data for everyone,” says Don Burgess, a long-time expert in the field, retired chief of the Warning Research and Development Division NOAA, and now at the Cooperative Institute for Mesoscale Meteorological Studies at the University of Oklahoma.
So today we’re off for Salina, Kan., on the hunt for more tornadoes.
Top, photo taken north of Kimball, Neb., where a funnel cloud just formed and broke up, by Christie Nicholson/copyright Scientific American. Bottom photo of the June 5 LaGrange, Wyo., tornado, courtesy of Rachel Humphrey of the University of Colorado
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