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| TORNADO SCIENCE | |
 July 25, 2005  |
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Scientists from the Center
for Severe Weather Research track storms in western Kansas' "Tornado
Alley" in an effort to improve their understanding of the process of
tornado formation so that better predictions may someday be made. The NewsHour Science Unit is funded, in part, by a grant from the National Science Foundation
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TOM BEARDEN: A spring afternoon on the plains of western Kansas, the heart of what some call "Tornado Alley." If you want to see tornadoes this stretch of the Midwest this time of year will give you your best shot.
Using this increasingly sophisticated equipment, Joshua Wurman and his colleagues are carrying out a detailed examination of the internal structure of tornadoes. JOSHUA WURMAN: We're trying to understand the process of tornado formation better so that better predictions can be made. Right now, you might have five-to-15 minutes warning that a tornado is going to occur, and it's a fairly imprecise warning. If we could increase that warning time to, let's say, half-an-hour or an hour, people might be able to take better safety precautions.
JOSHUA WURMAN: It's about 10 or 15 kilometers to our northwest right now. We're expecting -- we're hoping that it will move in our general direction. |
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| Tracking how tornadoes form | |||||||||||||||||||||||||||||
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TOM BEARDEN: Wurman's team has intersected only 120 in the past 10 years. The team finds them by driving toward giant, rotating thunderstorms called "super cells" and using their Doppler radars to peer inside the clouds and rain. A few super cells eventually generate the narrow, rapidly rotating column of air that drops to the ground to form a tornado. But the causes are complex, with no generally agreed upon theory of why that happens or why so many super cells never develop tornadoes at all.
A super cell may last one, two, or three hours, or even more, and only produce a tornado during 15 minutes of its life, and knowing whether it's going to produce a tornado at 7 p.m., 7:30 or 8 p.m., affects which communities you're going to warn. TOM BEARDEN: This particular super cell did produce a tornado a small, short one, hard to see in all the rain, but it showed up clearly on Wurman's radar screen. JOSHUA WURMAN: This is kind of fussing around back there. It's not moving farther or closer.
JOSHUA WURMAN: By scanning back and forth through the storm, we can make two- and three-dimensional maps of the velocities of raindrops or debris or chickens -- anything that's flying around in a tornado. One of the main foci of our project this year is to get up closer to the tornadoes and observe the lowest levels of the tornadoes, the lowest 100 feet of tornadoes, and if one of those tornadoes that we're observing passes over some structures, we will do a detailed, immediate damage survey, and then directly compare winds that we observe to the damage that occurred.
STUDENT: I'd say between, you know, I-70, U.S. 50 and maybe from U.S. 281 over to U.S. 83, so not far from here. TOM BEARDEN: It's a relaxed, collegiate atmosphere, with an occasional practical joke. The students are unpaid volunteers and finding funding is always a challenge. The National Science Foundation carries most of the load, but Wurman is always looking for other sources.
JOSHUA WURMAN: We have two different radars, and we're doing two different types of experiments with them. TOM BEARDEN: But despite the shoestring funding, the project has pushed the studies of tornadoes to new levels of sophistication. JOSHUA WURMAN: We're frequently forced into, sort of, a stamp collecting or "my favorite storm" type mode where we're writing a publication about Storm A, and another scientist will write a storm about Storm B, and there are a lot of differences by collecting data in many tornadoes -- 120 tornadoes now -- we are finally at the point where we can start analyzing more important things about them -- what's the intensity distribution of tornadoes? How rare is it to get a tornado with 250 or 300-mile-per-hour winds? |
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| Measuring the strength of tornadoes | |||||||||||||||||||||||||||||
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JOSHUA WURMAN: We know that this house had 200-mile-per-hour winds for four seconds and then it got kind of calm because it was near the eye of the tornado and it 220-mile-per-hour winds for 20 seconds. We know another house had 150-mile-per-hour winds for 30 seconds. And so we can compare the different time histories of damage to actual damage. That is the one and only case where that can be done. TOM BEARDEN: After following storm predictions in the makeshift base for several hours, at 4 o'clock the science team decided to head south. There was a promising series of storms near the Oklahoma-Kansas border.
TOM BEARDEN: This kind of thing happen a lot? JOSHUA WURMAN: Most of our storm intercepts end in busts, and we do not intercept or collect data in tornadoes. If about a fourth of our intercepts result in tornado data, we're doing pretty well. The previous four intercepts we got data. The last week or so has been great, but statistically, three out of four chases or more wind up as busts and this was just one of those. TOM BEARDEN: That's how it goes in tornado science. Wurman's team and other tornado researchers would like to be able to know in advance which storms are worth going to. But that, of course, is exactly what their research is attempting to discover. |
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The NewsHour Science Unit is funded by a grant from:  The National Science Foundation. Reports are produced solely by the NewsHour and do not necessarily reflect the views of the NSF. |
And
so for every year, for the past decade, a team of scientists for the
Center for Severe Weather Research has set up shop in this part of the
country, bringing several tons of high-tech radar and computer gear
along with them. 
TOM
BEARDEN: Earlier warnings might help prevent some of the approximately
80 deaths and 1,500 injuries that tornadoes cause each year. But despite
more than 40 years of research, tornado science is still a developing
field with a lot of unknowns. That's partly because getting close enough
to really study tornadoes is difficult. 
JOSHUA
WURMAN: We're trying to understand the differences between the super
cells that produce no tornadoes -- which is most of them -- the few
that produce some tornado, and the very, very rare ones that produce
the violent tornadoes. 
TOM
BEARDEN: Unlike fixed weather radars, Wurman's truck-mounted units get
close enough to produce sharply focused images that reveal wind speeds
at different altitudes of the funnel. And because each radar sweeps
the sky quickly, it's possible to watch a tornado's development minute
by minute. 
TOM
BEARDEN: The next morning, meteorology students working on the project
gathered in a low-rent apartment nearly the railroad tracks in Hayes,
Kansas. Early in the day, they analyzed computer weather maps looking
for place where's super cells might form later. 
The
project is getting some additional funding from a team of independent
photographers who work from a home built armored vehicle that looks
like something out of a "Mad Max" movie. They hope to shoot
an IMAX film, getting as close as they can to a tornado, and a storm-chasing
tour operator pays a fee so his clients can watch Wurman's group at
work and later follow their radars into the storm. 
TOM
BEARDEN: Conventional tornado science, the so-called Fujita Scale, tries
to measure the strength of tornadoes by measuring the damage they cause.
Wurman and his colleagues recently took that a step further by precisely
matching the damage in a single tornado in Spencer, South Dakota, to
the moment-by-moment changes in the tornado's wind strength. 
As
the convoy approached through rain and baseball-sized hail, they weren't
seeing much activity. Another storm to the northwest began to look better.
So they switched targets and raced toward that storm, but it, too, went
downhill. An hour later, windshields cracked by hail, they rolled into
Dodge City, Kansas, for a late dinner.