Nova (1974–…): Season 31, Episode 7 - Hunt for the Supertwister - full transcript

Tornado-chasing scientists with an eye to better forecasting risk their lives to plumb the secrets of nature's most terrifying killer.

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---
It's early May,

and an ugly storm is bearing
down on Oklahoma City.

In times like these, people turn

to their TV weather forecasters.

The conditions are...

Especially local
legend Gary England.

Of significant tornado activity.

Whoa!

Okay, talk to me!

The rotation that it had...

From the control room,
Gary watches in horror



as the heavy, roiling atmosphere
cooks up a deadly surprise.

Priority one! Priority one!

Tornado warning!

This isn't just any tornado.

It's one of the most violent
and destructive forces of nature...

A supertwister.

This is a major tornado.

Wind speed, we don't know,
but it's going to level most houses.

Get below ground immediately.

The date was May 3, 1999,

and one of the most
powerful tornadoes on record

had made a direct hit on
the suburbs of Bridge Creek

and Moore, Oklahoma.

Hello!



8,000 homes destroyed,

$1 billion of damage, 40 dead.

This is what happens

when a column of
spinning air blows faster

than 300 miles an hour.

A 250- or 300-mile-an-hour
wind can only be compared

to those that might
be experienced

on the fringes of a
nuclear explosion.

A 300-mile-an-hour wind

is not three times as strong
as a hundred miles an hour;

it is nine times as strong.

Most tornadoes strike
the American heartland.

But no place is safe.

In 2002 a supertwister
struck Maryland

just south of Washington, D.C.,

If you were to have taken
the La Plata, Maryland, tornado

and just moved it north
about 30 or 40 miles,

you would have gone
from Beltway to Beltway,

right across the Potomac and
in through the nation's capital.

For decades, storm chasers
have been stalking the supertwister,

trying to unlock
its deadly secrets.

Now armed with a slew
of high-tech gadgetry,

scientists are probing
deeper than ever before

and creating their own
tornadoes inside a computer.

Will they finally win the battle

against one of nature's
most terrifying killers?

"Hunt for the Supertwister,"
right now on NOVA.

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Moore, Oklahoma, just
outside Oklahoma City,

may look like an
ordinary American town.

But it has a disturbing
and violent history,

because this quiet community
has a habit of attracting tornadoes.

Numerous gas lines
have been busted.

The town was hit by major
twisters two years in a row...

In 1998 and again in 1999.

In May 2003 the
unthinkable happens again...

Another major tornado
heads straight toward Moore.

There you go.

It's down on the ground.

This time the spinning
vortex makes a beeline

for Mama Lou's Diner.

Well, we were sitting
out here having dinner,

and my daughter called

and said that a tornado
was coming our way.

The manager

told us we needed
to either leave or stay

and get in the freezer, walk-in.

There was a young waitress.

She went in.

My husband was
standing right in front of her.

He said she was shaking so bad,

he could feel her
tremble behind him.

I sat in this chair.

Things happen so fast
and people move so fast,

and the man in the wheelchair...

We couldn't get
this door to shut.

When the tree came
through the hallway,

we just fell kind of backwards
and it was over with.

When we walked out,
the walls were gone.

Everything was gone.

The ceiling was in.

There were people
laying everywhere

on the highway and
in the ditches, bleeding.

But we were all alive.

It was amazing... amazing.

Like the diners in Mama Lou's,

many residents of Moore
heard about this tornado

just a few minutes or even
seconds before they were hit.

Yeah, I was watching
the... the tornado

with the, uh, ACDC TV here.

Don Staley headed

for the aboveground
concrete safe room he installed

after twisters damaged his
house two years in a row.

I just felt the
vibration of the ground,

and... and, uh, about ten
minutes later opened the door

and the house was destroyed,

but I knew I could pick up the
pieces and go on with my life.

As Don sat watching it on TV,
the tornado destroying his home

had not even
reached full strength.

Just a few minutes later

the storm tore the
side off the GM plant

and leveled the union hall.

Many fear that scenes like
this are a sign of things to come,

that we haven't seen the
worst that tornadoes can do.

I think we have reached
a critical point here,

whereas we are now expanding
our cities bigger and bigger,

so the targets for tornado hits
are getting bigger and bigger.

And the fear that I have

is that now that the cities are
going to continue to get bigger,

the houses still stay the
same in terms of construction,

that now we're going to
start having an upswing

in the number of fatalities.

Let's just picture this.

Let's say it's 2:00
in the afternoon,

a large tornado
comes into a city,

moving toward a school
that has 500 children in it.

What's going to happen
when that warning goes out?

There's going to be hundreds
of parents trying to rush

to that school to
get those kids out.

And it will take the school
out, it will take the parents out,

and... and mark my
words, it will happen.

Tornadoes are freak
events of nature.

They can't be stopped.

But if we want to survive them,

we've got to predict when
and where they'll occur.

But tornadoes continue
to defy forecasters.

Other violent storms,
like hurricanes, are huge,

covering thousands
of square miles,

and show up on
radar and satellites

long before they strike.

Tornadoes are another story.

Compared to hurricanes,
they're tiny, and they form quickly.

But killer tornadoes don't
just appear out of nowhere.

Every spring warm,
moist air surges up

from the Gulf of Mexico,

pushing into cool,
dry air from the north.

The warmer air
fuels thunderstorms

that rise into the
upper atmosphere,

sometimes growing into
immense, rotating giants

known as supercells.

A swirling column of air
develops inside the storm,

narrowing and reaching
down toward the ground,

becoming a tornado.

Over a thousand tornadoes
touch down in the United States

each year.

In some, a narrow funnel
cloud waves and bends

like an elephant trunk,

while others grow wide,
enveloped by rain and clouds.

Most tornadoes are weak
and disappear within minutes.

A quarter of all tornadoes
have the potential

to cause significant damage.

A rare few unleash the enormous
energy stored in the atmosphere,

generating ground-level
winds above 200 miles per hour

and traveling dozens of miles.

He's going to drive
into it if he's not careful!

Rated F4 and F5
on a five-point scale,

these are the deadliest of
storms... the supertwisters.

They do happen, and they
happen nearly every year.

And of course if an F5
comes down your street,

if you're not in a safe room
or a basement or a cellar,

you're... you're probably
going to be history.

The first line of defense
against severe weather

is the National Storm Prediction
Center in Norman, Oklahoma.

But unfortunately
even these scientists

can't predict exactly
where and when a tornado,

or even a
thunderstorm, will strike.

We don't have a
very good picture

of the potential of
thunderstorm activity

and exactly where it
might be able to develop.

We all wish that we could,
uh, pinpoint the exact location

where severe weather will strike

and tell people what
time it's going to strike,

but the science hasn't
reached that point yet.

The storm center
monitors the atmosphere

across the entire continent and
then uses computer programs

to try to predict where the most
dangerous storms will develop.

If general conditions
look strong for tornadoes,

the storm center
issues a tornado watch,

often covering tens of
thousands of square miles.

Only after radar suggests
a tornado is forming

does an official
tornado warning go out.

When we issue the warning,

the warning is supposed to mean

that that tornado
has been detected.

It is there.

We want to be able to take it to
that next step where we can say,

"We've got this
really bad storm.

"Conditions where
that storm is headed

are ripe for a
tornado to develop."

Where we're at right now,

when you've detected
it, it's occurring.

Official tornado warnings
often come too late...

On average only 12 minutes
before a twister strikes.

And frequently
they're false alarms.

One man believes
we can do better.

My dream is to be able

to detect tornadoes
down at very fine scales,

to anticipate tornadoes a
half an hour before they occur.

We're talking about
a storm forming

to produce a tornado
over a county or a city.

It's a whole
different ball game.

Kelvin Droegemeier
is a meteorologist

who wants to overhaul

our current system
of detecting tornadoes.

We need to see closer
down to the ground.

That's where the
weather happens.

The storms up in the atmosphere,

they're the ones that
eventually cause the weather,

but the stuff that's
affecting society

happens down near the ground,

where we don't
observe things well.

Today's system relies in part
on a network of Doppler radar.

Doppler can sense the
movement of air and moisture

in remarkable detail.

Used as long-range radar,

Doppler dishes are spaced
100 miles apart or more.

Gazing out over the
horizon, they can't see

what's happening close to the
ground, where tornadoes form.

There... there's a limit
to tornado prediction,

and I believe we have
reached that limit right now.

With all the available
information that we have,

radars are only put
at certain locations.

They're not everywhere.

Radars that... that we have
can scan out a hundred miles,

but at a hundred miles,

they're only scanning
the top part of the storm,

and so they're not
seeing down low.

Kelvin Droegemeier
dreams of a world

filled with Doppler dishes,
hung on cell phone towers

and all kinds of buildings,
just 20 miles apart.

This Doppler-rich
world could paint

a much more detailed
picture of the weather...

Maybe even catch
tornadoes in the act of forming.

We want to put a few
of these radars out there

to make sure that if a
tornado is beginning to form,

we know absolutely for
certain that it's going to happen,

and we can tell you that
30 minutes ahead of time...

Whether it's a weak
tornado, a strong tornado,

whether it's in December
or... or March or... or May.

Kelvin is now wiring
central Oklahoma

with an experimental
network of small radars,

confident that his plan
will someday revolutionize

the forecasting of tornadoes,
including supertwisters.

But others aren't so sure.

You might be able to predict

that a storm may
or may not form,

you may predict that some
storms may be more likely

to produce strong
tornadoes than others,

but we may never
be able to predict

that a given storm
in a given location

will go on to produce a tornado.

Howie Bluestein's
skepticism comes

from over 25 years
chasing down storms

in the twister-prone
region of the central plains

known as Tornado Alley.

Cloudy with 85 degrees...

When he started out,

Howie's operation
was certainly low-tech.

There were no laptop computers,

no global positioning system...

Small Cbs building
up under the anvil.

No cell phones.

I'm a little bit worried
about something happening

right back just south of Norman.

Over time, the storm
chaser's arsenal has expanded.

Howie was the first
to put a radar dish

on the back of a truck

and capture crucial data
of tornadoes in action.

But even with today's tools,

storm chasers like Howie
consider themselves lucky

if they intercept one or two
good tornadoes each year,

because the thunderstorms
that spawn them

are extremely complex creatures.

Whether a thunderstorm forms
in one county or the next county

could depend upon
differences in wind

that you can barely
detect with instruments

or changes in
temperature or humidity

that are barely detectable.

And Howie knows
just how far we are

from understanding the
true nature of tornadoes.

We still haven't
solved the problem yet.

We still haven't figured out
exactly why tornadoes form.

For all their long
years of study,

storm chasers
are forced to admit

that the exact chain of events

that turns a thunderstorm
into a tornado

is still a mystery.

We know that supercell
thunderstorms make tornadoes,

but we also know
that most of them don't.

Josh Wurman is one
of Howie's colleagues

and a fellow storm chaser.

Only about 20% or 25%

of supercell thunderstorms
produce tornadoes,

and only perhaps one
to five percent of those

produce what we call
"significant tornadoes"...

The large ones, long-track,

the ones that do 90% or 95%
of the damage and fatalities.

Okay, down two.

Stop here near the hill
and start scanning, got it?

I feel like we're
in a twister movie.

Josh has witnessed

some of the most powerful
supertwisters of recent years,

including the May 3, 1999,
storm that hit Moore, Oklahoma,

where he recorded the
fastest winds ever measured...

Just over 300 miles per hour.

When the massive
supertwister first set down,

it was in a field about
40 miles from Moore.

TV forecaster Gary England had
a full hour to warn his audience.

Do not try to ride this
storm out in your home

unless you are trapped.

Get in the center
part of your house...

A closet or bathroom.

Cover it with pillows
and blankets...

Lots of pillows,
lots of blankets.

Get in the bathtub, put
the kids in the bathtub,

get in on top of the kids.

This is absolutely incredible.

I'm trying to get a West
Moore as we speak.

From Channel Nine's
command center,

Gary and his viewers could
see exactly what was coming.

Right now it may turn a
little bit to the north of Norman

If it maintains itself,
you folks in north...

May 3, there was
continuous coverage.

They had helicopters up in
the air filming the tornado,

so people could watch the TV,

see exactly where
the tornado was.

They had radar with
fantastic capability

showing the path that
this thing was going to take.

So people knew what was coming.

We got a funnel on the
ground, right now, right inside.

Tornado on the ground.

Debris cloud, debris cloud.

There it is... multiple...

May 3, you know, we
had nearly 70 tornadoes

in our viewing area
here in Oklahoma

and, you know, a
lot of people killed

and, what, 8,000
structures destroyed.

People pay attention now.

The May 3 supertwister was
the most powerful on record.

And yet, after it
finally fizzled out,

Josh Wurman and
his team discovered

yet another supertwister
roaring over open country.

During the May 3 outbreak,

there were at least
50 other tornadoes.

One of those was over four
times as large as the one that went

through the metropolitan
area of Oklahoma City.

Had that tornado gone
through Oklahoma City,

it would have caused a damage
swath four times as wide...

Probably a mile wide or more...

Destroying many
times more structures

than were actually destroyed.

The May 3, '99, event

is a major, major event
to the people in Oklahoma

and especially the
people in Oklahoma City.

But how many people
outside that area

realize what happened there,

realize the carnage
that took place?

It's not just powerful winds

that make
supertwisters so deadly.

Once they form, they
often keep on churning,

staying on the ground
an hour or more.

These so-called
"long-track" supertwisters

aren't confined
to Tornado Alley.

In 2002, one paid a
sudden and unwelcome visit

to a small town
on the East Coast.

It's coming this way, guys.

Come in here.

Here it comes.

Here it comes.

I remember seeing

this huge funnel cloud...

And it was holding
things in the air

that were just whirling so fast,
and as they came to the top,

you could recognize things,
like a tree, a couch, a desk.

You're expected... asked
to take cover immediately.

And we're looking
at each other thinking,

"Is that a tornado?

Where's it going?"

It was a supertwister,

sweeping straight through the
center of La Plata, Maryland.

Then I remember this
tangled mass of metal

was coming right at me,
I mean, directly at my car.

And briefly I thought, "Oh,
I'll probably get decapitated."

And my car lifted
two feet up in the air

and actually moved
under... under the CVS sign.

I still... I say it sounded
like a jet turbine engine.

I... I can't even
duplicate the sound.

And the house started
rumbling, shaking.

The giant vortex
sped through town.

This tornado was moving
at close to 60 miles an hour.

That's a mile a minute.

From... from here
over to the buildings

that are standing there,

the tornado was probably
through here in 15 seconds or less.

One minute, everything is there,

and then, you know, 15 seconds
or less, everything's destroyed.

It's amazing.

You go from almost no wind

up to 200-mile-an-hour
wind and... and back down.

As the tornado was ripping
through downtown La Plata,

just outside of town, Susan
Erikson and her husband, Erik,

were visiting the construction
site of their new dream house.

They had no idea a
tornado was coming.

The only thing we had heard

on the news that day
was "thunderstorms."

And we had thought,
"No big deal."

We had just come
up from the basement.

I remember
silence... at that time...

No birds, no anything.

I just heard silence.

And we were
getting ready to leave,

and then everything went blank.

Susan came to
in a pile of rubble,

hearing the groans
of her husband, Erik.

Both my arms were broke...
they weren't functioning correctly.

So what I did was try
to maneuver my legs

so that I could stand up
and drag my arms up with me.

I remember walking
out of the house.

Luckily, some
neighbors found Susan

before she passed out again.

The next thing she knew,
she was in the hospital.

It was between
the two surgeries,

before I went in for my
orthopedic surgery on my arms,

that they told me he had died,

um... and they said he was
in a morgue in Baltimore.

Erik Erikson was one
of five people killed

by the supertwister
that hit La Plata.

Far from Tornado Alley,

the monster storm carved a
path of destruction 62 miles long,

narrowly averting an
unthinkable disaster.

If you were to have taken
the La Plata, Maryland, tornado

and just moved it north
about 30 or 40 miles,

you would have gone
from Beltway to Beltway,

right across the Potomac and
in through the nation's capital.

Rare as they are, supertwisters
can strike anywhere, anytime.

But no one knows why.

In fact, scientists are stumped

about what causes any
tornado, large or small.

Unless they can solve the puzzle

and figure out how a supercell
thunderstorm creates a tornado,

then predicting supertwisters
will be impossible.

But how do you decipher the
inner workings of a tornado?

Meteorology, in contrast
to chemistry or biology,

is not a good
laboratory science.

We can't produce an
accurate representation...

A controlled representation
of a thunderstorm...

And change the variables
one by one to make tornadoes.

No one can create
a real tornado,

either on the
plains or in a lab.

But there is one place where
scientists can play puppeteer

with the weather...

In a computer.

The closest approximation we
have are computer simulations.

And we try to build

a digital computational
model of the tornado

and see if we can
change variables

and have storms that produce
tornadoes and ones that don't.

One of the leaders in tornado
computer modeling is Lou Wicker.

If it doesn't have
good rotation,

we're not going to deploy.

Cyclone data.

20 years ago, Lou was a
young and eager storm chaser,

tracking tornadoes
the old-fashioned way...

On the open plains.

Let's move, let's go.

We're moving west.

A little farther,
Steve, a little farther!

Peak the hill, peak the hill!

Back then, researchers thought

the best way to
learn about a tornado

was to leave special
sensors in its path.

That was the idea behind TOTO,

a weather station
the size of an oil drum.

Lou took charge of getting TOTO

as close as
possible to a tornado

without wiping out
the research team.

Let's go, let's go, let's go!

In the '70s and the early '80s,

we were just
trying to understand

what made storms
work sort of visually.

Now we're moving into an area

where we're trying to understand
the dynamics of storms.

Inside storms, "dynamics" means
how the individual blobs of air

are all interacting
with each other

to produce the flow that becomes

either the strong winds
or even the tornado

or even the things
that produce hail.

Based on years of
weather research,

Lou produces an amazingly
detailed computer simulation,

designed with scientists
at the University of Illinois.

It reveals a familiar pattern.

A thunderstorm explodes
into the atmosphere,

growing more
intense every minute.

The clouds begin to spin
and roil high in the sky.

They descend closer to the
ground, still swirling rapidly.

Suddenly the rotation
narrows and intensifies...

and touches down to earth.

The question on
everyone's mind is:

What triggers that final step?

What makes the tornado form?

Somehow supercell thunderstorms

are able to bring
intense rotation

and intensify that
rotation near the surface.

And we don't understand
that process very well.

We know that before
a tornado forms,

there are areas of
rotation in the thunderstorm.

What we don't understand
is how that rotation

is brought down to the
ground and intensified

in a very short period of time
in order to make a tornado.

In the search for a trigger,

one of the primary suspects
has been a burst of air

descending from the
storm, called a downdraft.

The idea is that the downdraft
wraps around the storm,

tightening and
intensifying the rotation.

We think the downdraft

is really important for
producing the tornado

because it helps
sort of squeeze the air

from near the ground
up into the updraft.

The air wraps
around and sort of...

the downdraft kind of comes
around and squeezes the air

in the front and
the back together

to kind of squirt the
air up off the ground.

In the minutes
before a twister forms,

storm chasers often
see a downdraft

blasting a hole in the clouds
toward the rear of the storm.

Well, it's a very
impressive storm.

So far, there's
still no tornado.

But the structure
looks quite good.

We're seeing a very
strong RFD coming down.

On the radar, it's still
looking pretty good.

But just as often, a
tornado fails to materialize.

There must be more to the story.

It's very likely that in order
to solve the tornado problem,

we're going to need a lot more
data than we have right now,

because a lot of things are
going on at very small scales

that we don't actually sample.

And so, until we have that, it
will remain a research problem.

And so, every spring,

storm chasers like
Howie Bluestein

hit the roads of Tornado Alley,

all on the hunt for
the tornado trigger.

What we want to do is capture
the formation of tornadoes

in many, many storms.

We want to see precisely
how the wind field is changing.

We want to see what's
happening to the temperature field

and the humidity
field for a lot of storms.

Mobile Doppler radar is the key

to mapping the swirling wind
patterns that spawn tornadoes.

Today's storm-chasing
teams often include

at least two Doppler trucks,

so they can record the storm
from multiple perspectives.

25 years ago, we
went out by ourselves.

Now when we go out, there's
an armada of cars out there.

There are a number of
different mobile Doppler radars.

And of course the more
vehicles you have out there,

the more vehicles that need gas,

the more people that have to
run to the bathroom at bad times

and so on.

All the high-tech sensors and
computers they haul around

allow Josh and Howie to monitor
tornadoes in fantastic detail.

The only problem
is this equipment

doesn't like to travel.

Radars, at some fundamental
level, aren't really designed

to be put on trucks and
bounced around in severe storms.

So we have a lot of problems

with the complicated
electronics,

where things just
shake and break apart.

We have shorts and things
like that happening all the time.

Not much I can do about that.

We've broken our windshields
now for the last two days.

Our last one only
lasted seven hours...

That's pretty frustrating.

When you're storm-chasing,

you have to be
prepared for anything,

whether it's treacherous
road conditions...

dust storms...

or hail the size of baseballs.

Reply to scout.

And there's a
horse in front of us.

Oh, look at that.

Yeah.

Oh, a horse... well, of course.

Hey, hey, hey,
hey, hey, hey, hey!

You guys were in the truck.

The messy and unpredictable
reality of storm chasing

shifts into high gear
on May 15, 2003.

Josh and Howie lead separate
teams on the hunt for tornadoes.

May 15 was
incredibly complicated.

We and everyone else
in the world recognized

that over the Texas panhandle,

the conditions were
ripe for tornadic storms.

The conditions
looked very, very good.

For a storm chaser, "very, very
good" means lots of wind shear.

Today, a zone of low pressure
is drawing warm, moist air

from the south into
the Texas panhandle.

Just above it, the jet
stream is blowing even faster.

The two air masses crossing
at different speeds and altitudes

produce wind shear.

When there's wind shear, air
near the ground begins to spin.

If there's a
thunderstorm in the area,

it could take on this spin

and perhaps go on
to spawn a tornado.

As the chase begins, the
team leaders must choose

what part of the Texas
panhandle looks most promising.

A lot is riding on the decision.

Well, we have a lot of anxiety

because it's a very
high stakes game.

It's very expensive
and time-consuming

to go out after these
storms, and they're fairly rare.

So we really need to
make these calls efficiently

if we're going to capture
these rare events,

and we only have a few
chances every year to do that.

Josh decides to head
north toward Dalhart, Texas.

Howie is unsure.

Now... now I can do my Lou Reed.

♪ I don't know just
where I'm going ♪

♪ But I'm gonna try... ♪

His team needs to find
an Internet connection

to get a update on the weather.

They find one in a restaurant
in Shamrock, Texas.

Gusting to 38 at Guadalupe Pass.

Oh, man.

Oh!

Oh, my God, will
you look at that!

That is ridiculous!

Look at the back
winds, and they're strong.

Oh, wow.

It's going to be
west of Amarillo.

It's going to be...

Oh, man, that looks juicy.

Howie thinks the southern
panhandle holds more promise.

He also fears that up
north, where Josh is headed,

the road system is too sparse.

They're going to
go off into an area

where the road
network isn't too great.

So Howie chooses to hang
back near Amarillo, Texas,

and wait for the
storms to come to him.

We're north of
Stratford now already.

I guess the other
possibility is just going.

Having chosen the northern
route, Josh lucks out.

When the show begins,
he's in perfect position.

There's the tornado.

There's the tornado.

Looks nice.

Oh, yeah! Oh, yeah!

As soon as you
look at the radar,

you should be able to see
that rotation pretty clearly.

We intercepted six
tornadoes on that day.

Look at this!

Look at this!

And one thing that was
fascinating about that storm

was there were at
least two occasions

where there were two vigorous
tornadoes on the ground

at the same time.

This is the first time

that twin tornadoes
have ever been captured

with ground-based mobile radar.

Back to the southwest.

I cannot miss you, ma'am.

Having two tornadoes
in close proximity like that

maintaining their
vigor is very unusual.

We've never seen that before

in all our years
of radar intercepts.

Josh and his team
take home the prize.

They've captured high-quality
evidence on multiple tornadoes,

including rare twin twisters.

In the meantime, about a
hundred miles to the south,

the weather is
depressingly fine,

and Howie has captured nothing.

Aw.

Oh, he doesn't like me.

Or she doesn't like me.

It's the storm
chaser's nightmare

to know that you made a
good forecast in general,

but there's a tornadic
storm going on

that you could have gotten

that's just a
hundred miles away.

You've driven all this...
this great distance,

made what you thought
was a really good forecast,

and... and you've
missed a... a tornado

by... by an hour or two hours.

You feel terrible!

After hours of waiting
around the southern panhandle

watching the clouds on radar,

things are looking bleak

when finally, Howie gets
an encouraging phone call.

Hello.

Yes, Don.

We are sitting in Hedley right
now watching it on our radar.

Fantastic!

That's what we've been watching.

Okay, thanks a lot.

Okay, I'm going to
come out and look at it.

We have some good news.

Oh, my God!

Wow!

That looks... that looks good.

All right, let's
get it together.

If the sun could go behind
there, I could get a picture.

That looks...
that's really nice.

What Howie sees is the
vertical edge of a thunderstorm

pushing up through
the atmosphere

and beginning to
rotate... A supercell.

All of a sudden, one of
the storms suddenly went up

and became a supercell.

It's as if someone had
turned the switch on.

Looks like a good supercell.

We're going to
have to move here.

We're having trouble
with the computer.

Even as the sun is setting,

Howie's team tracks
a series of storms

back to the outskirts
of Shamrock.

Finally, a familiar pattern
appears on the radar screen...

A hook shape often associated

with a strong, swirling
downdraft... and a tornado.

We have the hook echo.

It's just to our west-northwest,

probably right now
less than ten miles.

And it's... it may
be strengthening,

and there may be
another tornado possibly,

and we're collecting
data right now.

The Doppler radar reveals

that just a few miles
away, a tornado is churning.

I hate to not be able to see it.

If we didn't have the
radar, we wouldn't be here.

Better get back in.

There's very, very strong
inflow into the storm right now.

It's extremely dangerous
to be so close to a tornado,

especially after dark.

We have a local sheriff.

If the storm had been
moving at 35 miles an hour

coming right towards you,

and you were near the storm

but you didn't know
precisely where the storm was

with respect to where you were,

you could have
been in great danger.

Howie's eyes couldn't pierce
the darkness to see the tornado,

but his Doppler
radar dish could.

The radar kept Howie
and his team safe,

but did it capture any important
clues to the tornado mystery?

To find out, Howie and
Josh will both spend months,

even years, back at their labs,

dissecting the evidence
they collected on this,

the most productive
day of the season.

The storm chasers will pack
up their equipment in early June.

But miles away, in the northern
reaches of Tornado Alley,

the show is far from
over, and the stage is set

for a rare appearance by
the elusive supertwister.

The time is late June 2003,
and the place is South Dakota.

There's no Doppler,
no data and no theories.

Instead, there are
tornado tourists.

I think it's one of
those things that...

it's just a force of nature
that's so overwhelming,

you've got to experience
it personally if you can.

We're actually here hoping
to see our first tornado.

You know, we're not going
right underneath these things.

We're just hoping
to see something,

you know, from a distance.

Well, it's quite a volatile
setup today for severe weather.

We could even have a couple
of very strong tornadoes today.

Roger Hill directs a
storm-chasing tour company.

He's not a scientist,

but he does have a
knack for finding tornadoes.

His clients come for
the adrenaline rush...

To encounter nature
in all its violent glory.

They're seldom disappointed.

Folks, hang on, hang on
here, we're not slowing down.

We're going to stick
right up here with it.

Oh, look at this, look at this.

Be careful, power
lines are down here!

Power lines are down... careful!

We can't go through here.

There's going to be a
large tornado anytime now.

Are we safe here?

Yeah, we're safe right here.

Whoa! Power lines are popping.

Oh, no... not now.

Large tornado,
Bill... large tornado!

It's humongous!

It's right west of us.

We've got a great view of it.

Wow!

Look out, look out!

Hang on, hang on!

Just hang on!

We have a funnel.

We have our next
tornado developing.

On June 24, Roger's
group has a front-row seat

as a tornado sweeps by the
town of Woonsocket, South Dakota.

Whoa, what a debris
cloud it's got now.

The tornado dies out,

but Roger knows there's
more where that came from.

It's... it's going
to go up and die.

That one up there, though...

We may need to head up that way,

because that could be tornadic
with the next 30, 45 minutes.

They pile back in the
vans to follow the storm

as it regains its strength.

Stop right here at
these streets up here.

Stop before these streets.

Right here, right here.

Here it comes, here it comes.

A funnel cloud begins to
take shape and then grows.

Condensation funnel
is on its way down.

Just keep it there, baby.

Suddenly the tourists
find themselves spectators

to a terrifying display
of nature's power...

An F4 supertwister with
winds over 200 miles per hour.

The tornado easily levels
the town of Manchester.

Fortunately, all six
residents survived.

As the tornado continues
across the plains,

Roger and his excited
entourage speed off to chase it...

and the people of Manchester
are left to pick up the pieces.

For those in its path,

a supertwister like
this is a nightmare.

But for some scientists,
this storm is a dream.

Back in Norman, Oklahoma,

Lou Wicker decides
to try to bring

the Manchester supertwister
back to life in digital form.

Into a supercomputer
go basic weather data...

Wind speeds, atmospheric
pressure, humidity,

all present before the
tornado took shape.

Then the virtual
storm grows on its own,

and Lou sits back to see
if a tornado actually forms.

The dynamics of
the digital storm

are rendered in
incredible detail.

Warm air... shown in
orange... Rises into the storm

until it slams into
the jet stream above.

A column of air
begins to spin rapidly.

Sure enough, a tornado is born.

A computer has succeeded
in creating a tornado

under the same basic conditions
responsible for the real thing.

But what set the
whole thing in motion?

One of Lou's images
shows a clear hook

and with it a strong downdraft.

There's a very
warm, moist air mass

in this back-side region here,

and that's very interesting,
because that means

that while there is a sort
of a downdraft in there,

it's not a cold,
rainy downdraft;

it's sort of a warm,
juicy downdraft,

which will really
help feed the storm.

But in addition
to the downdraft,

Lou begins to discern a more
subtle trigger for the tornado.

To his surprise,
the model reveals

that just as the
storm intensifies,

a series of whirlwinds
forms at ground level.

These tiny corkscrews
of wind merge together

into a much larger
vortex... The tornado itself.

It's very chaotic and
it's very complicated.

It's not just a simple
little downdraft here

and just spins itself up.

There are lots of things
going on at the same time.

I think it captures

a lot of the complexity
that we see in the real world.

The whirlwinds that show up
in the computer are so subtle,

in real life they'd be
invisible to the naked eye.

But is there any evidence
they exist in nature?

Howie Bluestein
believes there is.

We've been able to
actually catch tornadoes

in the act of forming with
very, very high resolution,

and what you see
is... well, it's not chaos,

but you see a lot
of small vortices.

You don't see one vortex
becoming a tornado;

you see a number
of small vortices.

And the data proves it.

Mini-twisters have shown up
on both Howie's and Josh's radar

before the tornado forms.

This adds a whole new layer of
complexity in the tornado story.

All the evidence is pointing
to an amazingly intricate dance

of wind and moisture
interacting with the environment

including the terrain itself.

The smallest changes can have
a ripple effect in the atmosphere

and can make the recipe
just right for a tornado

or even a supertwister.

The precise details are
still being worked out.

But Howie thinks we're
closer than ever before.

I think that the
solution may be in sight.

We will, I think, within
the next ten years,

with the mobile Doppler radars
actually see why tornadoes form.

Everyone is painfully aware

that lives are hanging
in the balance.

We have been with tornadoes

that have gone through
towns and have killed people,

and it makes you... it
makes you feel sick.

It's a horrible,
horrible feeling.

But at the end of
the day, we feel that...

that perhaps on the
basis of what we've learned

over a number of years
that we'll be able to eventually

give people better warnings

and hopefully save
lives in the future.

If we can increase warning
times by five or ten minutes,

that's really significant.

If we can push back
the forecast of a tornado

to 15 minutes before
the tornado forms,

people have 15 minutes
to get to their shelters.

So small increases of just ten
minutes, 15 minutes, 20 minutes

can have a great impact
on the value of that forecast.

With each season,
the quest continues

with a renewed sense of urgency.

And every spring,

when the supertwisters descend
on the American heartland,

sending residents
fleeing for their lives,

Howie and Josh will be
driving toward the storm

along familiar roads,

hoping for a glimpse
into the unknown.

It's the same kind of feeling
that explorers probably had

300 years ago when they
first saw a new mountain

or a new river or
a new continent.

The modern-day explorers
are mostly scientific explorers.

There are places in nature which
have never been seen before.

Or never understood before.

So seeing inside a
tornado for the first time,

getting some understanding
about how that tornado works

drives the explorer inside me

to try to understand even more,
to see even more tornadoes.

Until they've unraveled
the mystery of the tornado,

storm chasers will
continue to follow the clouds,

probing ever deeper into
the heart of the supertwister.