Tornadoes
Experts Say
Want to learn more about storms? Check out the transcript of a message board discussion with Tornado expert Gary Conte.
Storm Chasing
My name is Rich Thompson, and I'm a lead forecaster with the Storm Prediction
Center in Norman, Oklahoma. One of the things we do at the Storm Prediction
Center is make forecasts of when and where tornadoes may occur. Tornado
forecasts have gotten better in the past 20 years because of important
new information that comes from tornado research.
Two ways that meteorologists research tornadoes are through field projects
and with computer models. In the field projects, meteorologists get important
weather observations by driving and flying around storms that produce
tornadoes. This information is used by the meteorologists to create computer
models of storms. The advantage of using computer models is that you can
change one of the variables, such as temperature, and see how the changes
affect a thunderstorm. Unfortunately for meteorologists, we can't just
make changes and see what happens with real storms!
The biggest problem we have in studying tornadoes is figuring out how
to get measurements inside tornadoes. Researchers have tried to place
weather instruments in front of tornadoes for many years. In more than
15 years of research, these instrument packs have only been hit by a tornado
two or three times! It is now becoming easier to detect wind motions inside
tornadoes with Doppler radar. In the past few years, Doppler radars have
been placed on trucks that can be driven close to the storms that develop
tornadoes.
The most important part of the field projects for my job is to find new
ways to forecast tornadoes. A recent project, called VORTEX, provided
many more measurements than are normally available around thunderstorms
and tornadoes. Researchers continue to look at all of the special information
gathered during project VORTEX. There is so much information that it will
take many years to examine it all. Future field projects will likely use
mobile radars, cars with weather instruments, many small instrument packs,
and remote controlled planes. We hope to understand tornadoes well enough
so that we can accurately predict when they will occur, and protect the
lives of people unfortunate enough to be in the destructive path of a
tornado.
Q: What is the biggest tornado you have ever seen?
A: Two tornadoes are tied as my largest — one in the Texas Panhandle
in June of 1995, and another in Oklahoma in May of 1999. While a typical
tornado is only 100 yards wide, each of these tornadoes reached a width
of about 1.25 miles!
Q: What's the closest you've ever been to a tornado?
A: Back in 1991, my chase partners and I were about 250 yards from a developing
tornado. The tornado was forming in an open area and moving away from
us, so we weren't in any great danger.
Q: Do you ever get scared when you are chasing tornadoes?
A: There have been many times when I've been concerned for my safety. However,
it's usually because of a close lightning strike, not because of a tornado!
I try to stay away from the path of a tornado.
Q: Has anyone ever died while storm chasing?
A: To the best of my knowledge, there has only been one person killed as
part of a storm chase. I believe a chaser died in a car accident while
returning home from a storm chase at night in the rain. There have
also been people injured by lightning, but automobile accidents are the
biggest threat.
Q: What equipment do you use for chasing tornadoes?
A: I always take a still camera and video camera with me, along with tripods
for them. I have also used a laptop computer and cellular phone to get
weather information while driving around, along with a GPS (Global Positioning System) to track our exact location
at all times. Some chasers even have weather instruments attached to their
vehicles to monitor temperature, wind, and moisture changes while driving.
Q: How quickly do you set up equipment?
A: It depends on what stuff I bring with me. Most of the time it takes me
about 3-5 minutes to set up the camera tripods and get my camcorder
running and mounted.
Q: How many tornadoes do you see a year?
A: I average about 12 storm chases a year, and roughly 4 tornadoes. The numbers
vary a lot from year to year — I've seen as many as 16 tornadoes
in a year, and as few as zero.
Q: How do you know when a tornado is changing directions?
A: Most tornadoes I've seen have moved in a single direction. Sometimes tornadoes
will turn a little to the left or right before they dissipate. Since the
size and strength of tornadoes can change very fast, it's smart to keep
a safe distance between you and a tornado, and watch it closely.
Q: Have you ever been inside a funnel?
A: No! I want to chase again another day, so I don't think it's a good idea
to drive into a tornado, or to let one hit you!
Q: How has today's technology narrowed the gap in predicting severe
weather such as tornadoes?
A: Advances in technology, such as Doppler radar, have made it easier for meteorologists
to identify the types of storms that may produce tornadoes a few minutes
before the tornado occurs. Also, improved computer models have led to
a better understanding of tornadic thunderstorms. Unfortunately, improvements
in forecasts of tornadoes have been slow to occur because we are still
unable to observe and forecast some of the details that appear to be important
to tornado formation. Some of these atmospheric details include how the
low-level winds change with height around a storm, and exactly how warm
or moist the air is that sinks near the back of a storm. Observations
from project VORTEX, along with other scientific studies, suggest that
these factors are important to the creation of a tornado.
Q: What is the difference between a storm chaser and a storm spotter?
A: Storm spotters are part of an organized group whose purpose is to watch
the skies around different towns and tell the National Weather Service
about dangerous storm conditions. Spotters often stay in one location,
and use amateur radio to send their storm reports to the National Weather
Service. On the other hand, storm chasers follow the storms as they move,
and are normally not part of an organized group.
Q: Why do you think storm predicting is important?
A: I believe that accurate forecasts of storms make it easier for people
to protect themselves and their property from the damage storms can cause.
If people expect severe storms to occur, there is a better chance they
will be ready to respond when severe weather threatens.
Q: Why is it there are so many more tornadoes these days than when
our parents were kids? (At least it seems like there are more!)
A: I think you figured it out yourself — it just seems
like there are more tornadoes now than when your parents were kids! Nowadays,
the TV news programs spend a lot of time reporting on weather disasters,
so it seems like there are more bad things happening. But the truth is
that the number of reported tornadoes has indeed increased by several
hundred in the past 10 to 20 years. Most of the increase is due to additions
in the number of storm spotters and chasers. We are just getting better
at keeping records and finding tornadoes that were not reported by anyone
in the past.
Q: Are tornadoes in the Northern Hemisphere different from tornadoes
in the Southern Hemisphere?
A: The only difference is the way the storms that produce the tornadoes tend
to rotate. Most tornadic storms rotate "cyclonically," which
is counter clockwise in the Northern Hemisphere and clockwise in the southern
hemisphere. Northern and Southern Hemisphere storms are just mirror images
of each other. Still, a few tornadoes have been documented that rotated
in the opposite direction for their locations, but those "anticyclonic"
tornadoes are rare.
Q: Why do more storms happen in April than in other months?
A: Actually, thunderstorms are most common in the United States from May
through August. The reason more storms occur in the spring and summer
is that the air near the ground is heated by the sun faster than the air
in the middle parts of the atmosphere. This makes the atmosphere more
"unstable" in the spring and summer as compared to the fall
and winter, and an unstable atmosphere is a key element in the creation
of a storm.
Q: How far up in the sky do tornadoes go?
A: Big, strong tornadoes are usually as tall as the storms that produce them,
which can be as high as 50,000 feet.
Q: What color are tornadoes?
A: It depends on how far you can see, and which way you are looking. When
you see a tornado with the sun behind it (usually from the east), the
tornado will look dark. When the sun is shining on a tornado (usually
from the west), the tornado may look white or gray, or even orange and
red if it stirs up a bunch of dirt.
Q: What makes a tornado start? What makes it end?
A: These are very difficult questions to answer. We think that a tornado
forms when the part of a storm where the air is moving upward (the "updraft")
draws in air near the ground that has lots of spin (the fancy name is "vertical
vorticity"). The storm updraft then stretches the air that has lots
of spin, and the spin gets tighter and stronger until it's strong enough
to be called a tornado. When the air with spin becomes too cold to feed
the storm updraft, then the tornado weakens.
Q: What year had the most tornadoes?
A: In 1998, 1,424 tornadoes were reported in the United States.
Q: How can a tornado damage the natural landscape?
A: Winds in most tornadoes are only strong enough to break tree branches
or blow over a few trees. Very intense tornadoes, with wind speeds that
may approach 250–300 mph, can remove almost all vegetation and leave nothing but bare ground!
Q: How often do F5 tornadoes occur?
A: F5 tornadoes are very rare. An F5 tornado occurs about once every couple
of years in the United States. It's possible that other tornadoes that
remained in open
country were capable of producing
F5 damage, but we
can't really tell unless a tornado damages man-made
structures.
Q: Is there any way to stop a tornado once you know it's coming?
A: There is no practical way to stop a tornado at this time, so the best
thing you can do is seek shelter or just get out of the way! Many different
people have suggested different ideas to stop a tornado. One idea is to
use a large bomb to disrupt the storm when a tornado forms. However, the
damage caused by the bomb itself would probably be much worse than the
tornado, which is why nobody has tried this so far!
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