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A freakish kind
of weather event...

We should not be here.

I know.
I'm shaking right now.

...is now striking
again and again.

People were panicking,

running, taking cover.

Intense...

Batten down the hatches

for the potential
for straight-line wind gusts

in excess of 75 miles an hour.

Highly localized.

That thing just collapsed
right on those mountains

and all that air
is just exploding.

And devastating.

MAN
Get away from the glass!

It sucked windows out.

There was glass everywhere.

They fall from the sky
without warning.

Explosions of wind and water
so violent,

they can flatten homes
in seconds.

They're known as rain bombs.

And they're getting stronger.

The damage each year
just continues

to pile up and up and up.

Now researchers are attempting
to understand

these destructive
weather events.

In some cases, it can look
like a bomb went off.

Trying to predict
where they'll drop and when.

It's not safe to be outside--
you've got about 20 minutes

until this severe storm
passes through.

"Rain Bombs."

Right now, on "NOVA."

August 2011.

The Pukkelpop Music Festival,
Belgium.

Out of nowhere,
the skies darken...

...as powerful winds gust
at over 80 miles per hour.

MAN
Please exit the tent!

Stages collapse.

Very quickly,
within a couple of minutes,

it became probably
the heaviest rain I'd ever seen.

Lauren Beehan was 19
when she and her friends

traveled from Ireland to Belgium
for the festival.

You couldn't see anything, really.

There was wind blowing debris.

It was very much a case
of feeling like we were trapped.

For it to turn
from such a sunny, cloudless day

to something apocalyptic
in the space of 20 minutes

is frightening.

It's like something
from a disaster movie.

140 people are injured

and five festivalgoers
lose their lives.

August 2024.

A super-yacht
called the Bayesian

sinks off the coast of Sicily.

CCTV from the shore that night

catches the vessel's mast,
lights barely visible,

in the 100-mile-per-hour
wind gusts and rain.

It drags anchor, then capsizes.

Divers recover seven bodies
from the wreckage.

July 2018.

In heavy rain at
Durango International Airport,

Aeroméxico Connect Flight 2431
is cleared for takeoff.

Jesus !

No sabemos si fue un rayo

o un problema mecánico.

The aircraft crashes back down
to Earth

before it even
clears the runway.

Miraculously,
there are no fatalities.

Each of these events was caused

by a mysterious
weather phenomenon,

recognized only
in the last 50 years.

Each began with a thunderstorm,

but what followed was much
more violent and unexpected.

Highly localized,
sudden, and extreme rainfall

and low-altitude,
high-speed winds.

They're nicknamed rain bombs,

but scientists
call them downbursts.

So, what are they?

And what causes them?

Mike Olbinski

is one of the world's foremost
thunderstorm photographers.

After 15 years
of chasing storms,

he's mastered the art of being

in exactly the right spot
at the right time

to photograph
an elusive weather phenomenon.

Rain bombs
exploding from the sky.

His images can help scientists
understand

how these weather systems form

and how they detonate.

We have an updraft going up
right to our west,

and then this big storm
is forming right behind it,

and I can see it on the horizon,

so I think we need to get
a little bit more west.

Growing up in Phoenix,

we used to watch
lightning storms, you know,

outside at night.

I loved them,
and I've always loved them,

and I traced it back

to seeing a lightning bolt
strike behind my house.

I still have this insane,
vivid memory of it happening.

Mike is on the hunt
for rain bombs.

These intense weather events
are striking

with greater strength than ever.

To track one down,
he first needs to find

a developing thunderstorm.

But what is the difference

between a rain bomb and
a run-of-the-mill thunderstorm?

In a normal thunderstorm,

you get heavy rainfall,
lightning, and sometimes hail.

And this can happen over hours.

A thunderstorm can drop rain
at about two inches per hour.

A rain bomb can triple
that rate.

And in a rain bomb,

the rain and hail aren't
just falling to the ground.

They're being thrown down by
hurricane-force vertical winds.

What does a rain bomb
look like?

It looks a massive
volume

of rain and cold air

coming from cloud base
to the surface.

Across the planet,

there are 2,000
electrical storms

generating thunder and lightning

at any given moment.

Each one of them releases
more energy over its lifetime

than the 15-kiloton atomic bomb
dropped on Hiroshima.

Every rain bomb forms from
a developing thunderstorm,

but to understand how,

we must first understand
how clouds form.

When sunlight hits the Earth,
the surface heats up,

and water from oceans, lakes,
soils, and plants

starts to evaporate,
turning into water vapor.

That water vapor and the warm
air around it start to rise.

As it starts to rise,

it takes all of the water vapor
near the surface of the Earth

up into the atmosphere.

As it lifts that up in the air,
that parcel of air cools.

The colder the parcel,

the less able it is

to carry around
that water vapor,

and so it forces it out into
the formation of cloud droplets.

Clouds form
where the water vapor condenses

into tiny water droplets,
so small and light

that they stay aloft,
instead of falling as rain.

The altitude where this happens
is called the cloud base.

You see lots of little clouds
developing,

and they all have
the same cloud base.

So the cloud bases
are actually occurring

at the same temperature,
and hence the same height.

In Arizona, the summer
monsoon season has arrived.

It carries moist, warm air
from the Gulf of California,

the perfect fuel for
thunderstorms and rain bombs.

We can feel it in the air,

that it's really humid out,
there's moisture,

it's warm, so we've got
the environment

for, for storms to form.

We're seeing these strong

cauliflower kind of
shape to the top.

When you're seeing that,

you've got to imagine
how intense that is

to go from nothing
to this sharply defined cloud.

And then a couple of them
get a little bigger,

and then you get something like
this, where, boom, it erupts.

If the conditions are right,

these simple clouds can turn
into thunderstorms.

When you have

these puffy, fluffy clouds
that you see in the sky,

there are some interesting
things going on inside.

Condensation is happening,

and heat is actually
being released

as water vapor is changing
to water.

As the water vapor cools,

it condenses into droplets

that form a cloud,
warming the surrounding air.

The now-warmer air rises,
creating more updraft,

lifting more air higher
into the cooler atmosphere,

where even more water
can condense,

which further warms the air.

If the conditions are right,

with enough moisture
rising into cold air above,

this fuels
a positive feedback loop

that intensifies
the cloud's growth.

I see, like, a whole line
of updrafts going up,

so I like that.

A lot of these tops today,
they just look

really strong.

Sometimes you got
the towers going up,

but they don't have
the same kind of powerful look.

They're bubbly
like a cauliflower,

but they're
just a little less intense.

Well, a couple of these,
if you look at them,

they just look like
there's so many areas

where it's just knuckle-y

and explosive-looking.

Oh! I just saw two big bolts
strike

way out there on the horizon--
whew!

But I think something big's
going to happen here.

It's a nice, large, dark area.

This is probably going to turn
into a really strong storm.

I would expect, I would hope.

I'm trying to catch
some lightning right now.

I'm doing two timelapses.

Lightning is an indicator

that the updraft is tall enough
to have ice and hail.

Ice and hail
are key ingredients

that drive
the most powerful rain bombs.

But how does something
as solid as ice or hail form

and stay aloft
in the atmosphere?

When water vapor condenses
in clouds,

it releases an extraordinary
amount of energy.

That makes our clouds
very turbulent

and that lifts the air
higher up in the cloud.

At some point in time,

that air will cross over
what we call the freezing level

to form things
like snowflakes and hailstones,

and that change in phase,
of course,

releases more energy.

This energy,
in the form of heat,

drives the further growth
of the cloud, expanding upward

to the very top
of the troposphere,

up to 12 miles
above ground level.

Above the troposphere
sits a warmer band of air

called the stratosphere.

This warm air acts as a lid
preventing the cloud

from climbing any higher,
so it spreads out flat,

forming
a distinctive anvil shape.

So we've gone
from the development

of a tiny little fluffy cloud

to these very tall,
extensive storms

that are now carrying around

large amounts of hailstones
and snowflakes.

This storm is now seriously
ready to do business.

Lightning bolts
are a telltale sign

that a cloud has developed
into a thunderstorm.

Raindrops get so big,

they're too heavy to be held
by the cloud's updraft,

and so it begins to rain.

Or, if conditions are right,
it can go on to develop

into a violent rain bomb.

To understand
why some thunderstorms

collapse into rain bombs,

it helps to know what's going on
inside that rain cloud.

One way to uncover that

is to analyze
the stuff that falls out.

Particularly hailstones,
icy chunks of frozen cloud.

Over the summer of 2025,

storm researchers teamed up
on a project called ICECHIP

to collect hailstones

from thunderstorms striking
the Great Plains.

BECKY ADAMS-SELIN:
The ground teams,

the teams looking at what kind
of hail fell at the surface,

is really what made
this campaign unique,

because other campaigns,
you know,

would go and, and look at,
at storms with mobile radars,

and that's a lot
of great information,

but only ours also tried
to really fully characterize

what kind of hail
was down at the surface.

The ICECHIP team
brings the hailstones

to a cold lab
in Boulder, Colorado.

Here,
at below-freezing temperatures,

atmospheric scientists
Anthony Bernal Ayala

and Becky Adams-Selin

process and analyze each
of the thousands of samples.

Large hailstones
are extremely valuable

in understanding more about
the thunderstorm they came from.

Once you get the hailstone,
you can actually just go ahead

and cut a thin slice out of it.

And you polish it up
so it's an even thickness.

You can get a lot of information
just by looking at the slice.

You can see different rings
in the hail,

and much like tree rings,

those represent
different conditions

under which the hail was growing
in the storm.

When we look at hailstones

and we look
at the cross-section,

one of the things
that we look at

is whether the layer is opaque

or whether layer is clear.

When you look
at that clear layer,

you're looking at where there
is warmer sub-zero temperatures,

so it's a little bit warmer
in the cloud,

where liquid water
freezes slowly,

and because this freezes slowly,

that allowed the air bubbles
to escape.

So it's gonna be clear--
there's not gonna be a lot

of air bubbles
trapped in this layer.

When you look
at the opaque layer,

because it's in temperatures
in the cloud that are very cold,

it's gonna freeze very rapidly.

So, because it freezes
very rapidly,

it actually traps a lot
of air bubbles in that layer,

so that it actually looks
opaque.

But why would a single hailstone

have both
clear and opaque layers?

And what does that reveal
about how the hailstone formed?

The hailstone had to have been
moving around in the storm

to experience
these different conditions

and to create
the different layers.

We think that it's actually
rotating somehow

around the updraft

to accumulate all those layers

that we see
in the cross-section.

These layers are evidence

that the hailstones are
continually rising and falling

inside
a developing thundercloud.

This hailstone
spent most of its time

in very cold temperatures
in the cloud,

but for a very short period,

it actually went through
a warmer side of the cloud.

Then it went back,
a very cold temperature,

then it went back,
a warmer section of the cloud,

where it probably fell and then
it was collected at the surface.

To grow to two inches wide,

this hailstone most likely spent
over half an hour

being lifted and dropped
inside the storm.

There's updrafts,
there's downdrafts.

There could be hail.

There could be circulations
or rotations

inside that cloud.

These intense storms
are very turbulent.

They have regions where air
is rising very rapidly,

sometimes at speeds
of 150 miles per hour.

This mixing of hail and ice
provides the energy necessary

for the storm to produce
thunder and lightning.

In mature thunderstorms,

like the one
that made Anthony's hailstone,

immensely powerful updrafts

can suspend
over a million tons of hail

miles above the ground.

It's actually quite incredible

that storms are able to suspend

this large mass
of liquid raindrops

and other ice,
like hail and snowflakes,

so high up in the atmosphere.

What happens to this core
of rain, hail, and ice

determines
whether the storm remains

a regular thunderstorm

or unleashes a rain bomb.

Dude, that looks
freaking awesome.

That's just plummeting-- that's,
like, a downburst happening.

When you see
that middle rain shaft area,

where it looks like a blob,

that's usually
a good telltale sign

of a downburst happening.

Oh, man.

This is stunning.

In a fully developed
thunderstorm cloud,

what goes up
must eventually come down.

The cloud's updraft begins
to peter out

as rising air cools
and sinks back toward the ground

as a downdraft.

This is what happens
in a standard thunderstorm.

But in a rain bomb,
things are different.

Because in a rain bomb,

a sudden, extremely strong
downdraft

overwhelms the updraft,

causing the cloud's core
of ice and hail to collapse

all at once.

Two processes drive this sudden
downdraft intensification.

The first is that, as the rain
and hail start to fall downward,

they drag on the air.

So they pull the air down
toward the Earth.

When massive amounts
of rain and hail begin to fall,

they help generate
a downward rush of air,

which can act
as the rain bomb's trigger.

But that's not all
that's required

to get a rain bomb started.

The second,
more important process

that accelerates this developing
downburst toward the ground

is evaporation.

Evaporation
is a cooling process.

You experience it
when you step out

of a swimming pool
or your shower.

When you've got drops of water
on your skin,

as these drops evaporate,
your skin feels very cold.

If winds blowing into the cloud
are dry,

they can rapidly evaporate
raindrops,

as well as melt ice and hail.

This cools the surrounding air,
making it denser and heavier.

This very cold air,
very dense air, has to sink.

So it's going to rush
toward the surface,

taking all of that large mass
of rain and hail.

As rain and hail descend
from the cloud,

if they hit more dry air,

the evaporation
can accelerate further.

As the raindrops fall
below cloud base

into this drier air,

they will evaporate
in that location, too.

This, of course, is going
to really intensifies

that cooling process.

This very cold, dense air
then rushes toward the surface,

creating
these phenomenal scenarios

called downbursts or rain bombs.

The downdrafts can intensify

into hurricane-force
vertical winds,

driving the cloud's core
of hail, rain, and cold air

downward,
slamming it into the ground.

Sometimes, the downburst's rain

can completely evaporate
before reaching the ground,

creating what scientists call
a dry downburst.

And all of these downbursts,
both wet and dry,

can strike
in just a few minutes,

in a remarkably narrow column,

as small as just a couple
of hundred yards across.

And as our atmosphere warms,

they're becoming
more and more powerful.

It actually can be quite
a frightening moment.

There's a lot going on.

There's lightning, there's hail,
there's very heavy rain,

and then, of course,
the strong wind.

Storm chaser Hank Schyma
has been caught

under a powerful rain bomb.

There was a day

where I get slammed
by a downburst.

The rain really picks up
and gets really strong,

everything turns white,
and then, all of a sudden,

I can see that I'm about
to drive off the road.

You can feel the winds
rocking your car,

and, and the winds
are picking up

sand and things in the road,

and they're slamming them
into your car.

It's really terrifying
and scary.

Strong winds are a key element
of downbursts.

They slam cold air
into the ground at high speed.

And this air has to go
somewhere.

They can't go into the ground,
so they spread out

horizontally in all directions.

So, you see
extreme surface winds.

Cold air hits the ground

and pushes out radially
from the heart of the downburst.

This outflowing air--

remember, it's very cold,
dense air--

we refer to as a cold pool,

because it is
a cold pool of dense air.

These advancing banks
of cold air can kick up dust,

creating
the distinctive dust storms

often seen
in the American Southwest.

Dusty cold pools
are called haboobs.

And they create all sorts
of severe weather,

including visibility issues,

road accidents,
and breathing issues.

The dust makes
the turbulent gust front

of an advancing cold pool

easy to see.

But even
when no dust is present,

this billowing front of cold air
is still there.

And it's these
fierce straight-line winds

that inflict the most damage.

These winds are

strongest near the surface.

If you compare that
to something like a hurricane,

a lot of the strength
in a hurricane

exists higher up
in the atmosphere.

But for downbursts, they occur
very close to the surface.

Trees will just flap down
to the ground,

and these wind gusts
are so strong

that you cannot stand
on your own feet anymore.

In some cases, it can look

like a bomb went off.

Literally, that air hits
the ground at low levels

and spreads out
in all directions.

Those winds are what we call
straight-line winds.

They are not turning
like a tornado turns.

They are following
straight lines

away from where
the downburst hits.

This might explain
what happened

to Aeroméxico Connect
Flight 2431

when it took off from
Durango International Airport,

en route to Mexico City.

The rain, while heavy,
was not extreme.

There were storms in the area,

but the tower had cleared them
for takeoff

and had told them that they
actually have headwinds,

which would provide them lift
for takeoff.

Without realizing it, Flight
2431 flew through a downburst.

In just seconds,
the plane experienced

a near 180-degree shift
in wind direction.

The plane was about 30 feet off
the ground,

a very susceptible time
on any takeoff,

and this tailwind,
it swung from being an uplift

to a sinking motion.

Without the lift generated
by a headwind,

the plane plummeted and crashed
into the runway.

Luckily,
everyone managed to escape

before the plane
was fully engulfed in flames.

This wasn't
the first passenger jet

to crash in similar conditions.

June 1975.

Eastern Airlines Flight 66
crashed on approach to JFK.

August 1985.

Delta Flight 191 crashed on
approach to Dallas Fort Worth.

July 1994.

U.S. Air Flight 1016 crashed
on approach

to Charlotte Douglas
International Airport.

Those tragic accidents
in the '70s and '80s

led to a lot of very significant
research in downbursts,

how they operate,
and then subsequently,

the technology that we need
to warn pilots.

A lot of the airports
in the U.S.

are fitted
with these weather radars,

but there are many of the
airports around the world

do not have this technology.

Aeroméxico flight
would not have taken off

had they been aware of the fact

that they were just about
to hit a downburst.

When investigators study
the loss

of the supposedly
unsinkable Bayesian yacht,

which went down
on August 19, 2024,

they discover that
before it capsized and sank,

it had dragged its anchor
around 400 yards

in a dead straight line.

The Bayesian was anchored

off the north coast of Sicily.

It was in a bay,
it was next to another yacht.

This CCTV footage
from a camera onshore

about 600 feet away

reveals the boat
in the distance.

What ended up happening was,

as these really strong
straight-lined winds

hit these yachts,

they dragged anchor
in straight lines.

That indicates
it was a straight-lined wind,

as opposed to the kind
of rotational wind

you would get from a tornado.

And it was a very large yacht
with a very tall mast

and it would appear

that the downburst
and associated cold pool

was actually able
to roll it over

beyond its point of stability.

The yacht succumbed
to the same type

of extreme low-altitude,
straight-line winds

that led to the crash
of Flight 2431.

At the Pukkelpop Festival
in 2011,

the hail and howling winds
struck an area

less than a hundred yards
across.

This was a very narrow
downburst.

This is what made it so unusual.

You would normally expect
such power

from systems that are larger,

where they can transport

more rain and more hail
and more wind to the surface

than in a 100-meter-wide
downburst.

So, a really remarkable event.

These real-life tragedies reveal

the destructive potential
of powerful rain bombs:

intense, highly localized,
and short-lived.

But a storm that hits Houston
in May 2024

has all the hallmarks
of a downburst,

except that it is much bigger.

It travels
around a thousand miles

and it lasts much longer
than a single downburst--

more than 12 hours.

A line of severe thunderstorms

is racing
into our Greater Houston area.

You should batten down
the hatches

for the potential
for straight-line wind gusts

at about 70, 80,
to 90 miles an hour.

National Weather Service
forecaster Amaryllis Cotto

is on call
at the Houston/Galveston office

27 miles southeast
of Downtown Houston

when the storm hits.

The storm developed very fast

in areas of West-Northwest
Texas at around 9:00 a.m.,

and so we could see
how fast it was moving.

It was already affecting
the Houston metro area

by around 5:00 to 6:00 p.m.

It's not safe to be outside.

You've got about 20 minutes
to get hunkered down

on the first-floor interior room
of your home, away from windows.

That's the safest place to be

until this severe storm
passes through.

It was devastating Houston.

We had a lot of tree damage.

We had millions of people
without power.

Hank and Natchaya Schyma

are five miles north of downtown
when the storm hits.

He starts recording the storm
from his car.

Suddenly, it goes from daylight
to darkness, and chaos hits.

Here it comes.

Holy (bleep)! Holy (bleep)!

Yup, hang on, I've got it.

Um, we should not be
here.

I'm shaking right now!

HANK SCHYMA
You can't see a block in front
of you

just because of the whitewash
of wind and rain,

and trees are swaying,

and downtown Houston
is raining glass,

as windows are, are failing
all up in the skyscrapers.

MAN
Move away from the glass!

The winds associated
with this system

were hurricane-force winds
in the lower levels.

It sucked windows out--
there was glass everywhere.

And in addition
to the sucking motion,

inside the buildings,

the pressure is now higher
than outside.

So you get this explosive force

that forces windows and glass
out of the buildings.

It's the signature
of a rain bomb.

Super-strong ground-level winds
shattering

any weak windows
along their path.

Telltale signs
of straight-line wind damage

are seen all over the city.

They pull down power lines
across Houston

and plunge one million people
into darkness.

But the Houston storm
isn't the size of the storms

that hit Pukkelpop
or sank the Bayesian.

It's over 50 miles across

and leaves a path of devastation

across the 10,000-square-mile
Houston metro area.

Rain bombs just don't
grow this big on their own.

They need to gang together
to become this large.

But how?

22 miles northeast
of Fort Collins, Colorado.

Atmospheric scientist Sue van
den Heever's 20-strong team

is out in the field.

I think the forecasters
are keen

to have some
surface measurements,

Okay.
They are trying to assess
the moisture.

Her team deploys drones
engineered to withstand

extreme weather.

They measure the outflow winds

when the cold air in a downburst
crashes to Earth

and races across the landscape,
forming the cold pool.

We've launched what we call
the flying curtain.

And we're flying a wall
of six drones.

We have a lower level of drones

and an upper level of drones.

We have a lot of instruments

that can measure
the temperature,

the moisture of the atmosphere.

We've got anemometers on there
that can measure the winds.

And this allows us to make
measurements of the variability

of the atmosphere,

and as the cold pool
advances on us

and blows through us,

we are able to make

that measurement in time,
as well.

So there's a lot

that we are characterizing
about these cold pools.

Sue and her team

are tracking a storm
a safe distance away,

beyond the horizon.

Radar shows that it has produced
a downburst of intense rainfall.

The air that slammed
into the ground

is now spreading out across
the plains in a cold pool,

coming toward them.

Their radar tracks the dust
kicked up

by the advancing bank
of fast-moving cold air.

So we're expecting

that cold pool to
come through

within the next few
minutes,

so we're waiting
to try

to collect
the data.

The team will release weather
balloons up into the cold pool,

to measure temperature,
pressure,

humidity, and moisture.

This cooling of the air
you can feel,

and the wind you're feeling,

that's this boundary that's
actually starting to hit us.

So we're going
to release that balloon.

Everybody ready?

Three, two, one.

Oh, and there's
some thunder.

Please release.

30 minutes
after the rain bomb dropped,

that bank of cold air,

here graphically rendered
to be visible,

has covered the 17 miles
from the epicenter of the storm

and breaks over
the flying curtain of drones.

On the ground,
the team analyzes the data.

So right here, we're,
we're looking at data

from the balloon
that we just launched.

What we're looking at
is pressure, moisture,

temperature, and relative
humidity.

And this is telling us

the depth of the cold pool

that just came through.

So right now, based on the
temperature data,

we're seeing a decrease in
temperature

that is going
about 500 meters high.

The team has learned
the cold pool

reaches 500 meters,
or about 1,600 feet high,

but that's not all.

These balloon observations
allow the team to measure

what's happening to the air
above the advancing cold pool.

What they've found
is that the cold pool

acts as a wedge, pushing up
an updraft of warm air.

When we have a storm

forming a really strong
downburst

and its associated cold pool,

that lifts the surrounding air

up and over the edge
of the cold pool

and forms a new updraft.

That updraft can go on to build
another really strong storm.

That storm can then, of course,
make its own downburst,

its own new cold pool,

which can then
form another updraft,

and so we get into this cyclical
process of updraft formation.

Background winds can stretch
downburst cold pools

from circular outflows
into fan-shaped fronts.

If atmospheric conditions
are primed

for multiple thunderstorms,

the cold pools can merge
into one broad line

of advancing cold air.

The advancing boundary
lifts warm air ahead of it.

This rising warm air feeds
a new generation of updrafts

and helps build
an even larger storm.

It's a self-sustaining cycle

of updrafts, downbursts,
and cold pools

that sweeps
across the landscape.

Meteorologists call this
a derecho.

One thing that distinguishes
derechos

from other types of wind systems

is their sheer size and how long
they can last.

The longest one on record
is some 1,300 miles.

Derechos can stick together

for time periods
of six to 12 hours.

So these are extensive,
very dangerous wind storms.

The 2024 Houston storm
was a derecho--

an organized system of multiple
repeating downbursts

that ripped across
a thousand miles of Gulf Coast

from Central Texas
to the Florida Panhandle.

Back in Arizona,
Mike has a hunch

that the beginnings
of a multi-storm system

are brewing west
along interstate eight.

Oh, man, this storm!

Big towers in the air going up.

Man, this is...
This looks frigging great!

Oh, my God, look at this demon!

Holy rain bombs!

Now, that's a downburst!

We have a monster rain bomb
right here,

a downburst of, like,
that we haven't seen so far.

I mean, this looks
like a bomb went off.

That thing just collapsed
right on those mountains,

and all that air is just
exploding and hitting us.

This is awesome!

I could see the towers up there.

They were probably 50,000-plus.

They were kind of twisting--
even right here, I see, like,

this updraft has
got a little twist to it,

and when that happens,

it's suspending that rain,

because it's rotating, so
it's suspending up there more,

so then, when it comes down,
it just has so much more force.

And all that air, all the stuff
we're feeling,

it's just blasting
from that storm,

and it's constant, because there
was probably multiple downbursts

that happened--
there was, like, an initial one.

There, there was one on the
right, one on the left,

and then just, like,
the main thing went down,

and now we're getting this dust
that's appearing right here.

The dusty outflow winds from the
rain bombs are racing west,

and Mike jumps in his vehicle

to get ahead
of the growing storm

and reset in a new position.

There's-- you can kind of
make it out.

So, we actually
have a dust storm coming.

So just overall, it's
getting better as it goes west.

Oof, lightning!

This dust in there
is looking good.

This dust is just food
coloring in the atmosphere.

Basically, the dust
and the shelf structure

are showing us the outflow,
or the cold pool,

where it's all consolidated
and pushing.

But without the dust,
you don't get to see

what the air's actually doing.

This is gorgeous-- the color,
this is what...

This is what you live for.

But this is the result

of stronger downbursts
that consolidated

and just formed intense outflow.

This is amazing!

What?!

Whoa, it's making them
disappear now!

What a day! What a day!

This dust storm produced winds
of over 55 miles per hour.

It was the result
of multiple microbursts

organizing into a larger system,
creating a macroburst.

If this dust-filled cold pool
had hit Phoenix

instead of the desert,

it could have caused
extensive damage.

And if it had grown further,
it could have become a derecho--

exactly what hit Houston.

Downbursts and derechos
are dangerous

wherever they strike,

but especially so
when they hit built-up areas.

So is there any way
to protect against them?

Ian Giammanco
is lead meteorologist

at the Insurance Institute
for Business and Home Safety,

the IBHS.

His team investigates

how a downburst's devastating
combination of wind and hail

inflicts damage on property.

When wind attacks a building,

it's always looking for
the weakest link in that chain.

And a lot of times,
that is at the edges of roofs

or if an opening,

say, a garage door, a window,
a door fails,

and that air is allowed
to rush in.

They use a monster wind tunnel

to test
the construction standards

of North American homes:

an extraordinary array
of 105 fans.

Each fan is almost six feet
in diameter

and packs 350 horsepower.

Together, they can produce winds
topping 100 miles per hour,

just like the Houston derecho.

Wind is a cascade of damage.

It often starts
with one little thing

that cascades to the next,
to the next, to the next.

And the next thing you know,

you're looking
at a catastrophic failure.

To reinforce homes
against the destructive power

of downburst winds,

Ian and the team at IBHS

have developed
a new building standard.

It's designed to help

minimize the amount of damage

that comes
with severe wind events.

The IBHS construction methods
include

a hail-resistant roof,

and also adds anchors
and metal connectors

to lock the roof to the walls

and the walls
to the foundations,

transferring the wind's force
down into the ground.

Build a home to these standards

and put it
alongside a typical home,

and the difference is clear.

As our wind speeds increase,

the front door fails.

That allows wind
to rush into that structure

and start pushing out.

The fortified home,
however, sitting on its right,

it's structurally sound--
it can take those forces,

whereas the conventionally built
home simply couldn't.

And the next thing you know,
the wall has failed...

...and it comes apart.

As our atmosphere warms,

that's simply producing
more fuel for thunderstorms.

It's air that wants to go up.

Those thunderstorms
can take advantage of that.

In a warming world,

you can store more water vapor
in the air,

so as we have
more of this fuel in the air

that can then condensate
and release heat,

these thunderstorms,
the derechos,

can become more intense.

As the world warms,

there will be more moisture
in the atmosphere on average.

But some regions
could actually dry out.

Drier air has to rise farther
to cool enough to condense,

so cloud bases would be higher.

That could have
big consequences.

If you had a cloud base
of this high

and now you raise it
to this high,

you have so much
dry air

to put raindrops through,
to put hailstones through,

that it gives the storm system
a lot more time

to evaporate and melt.

More evaporation and melting
may mean

there is less precipitation
hitting the ground,

but it also means
faster-falling, cold, dense air.

And so there's every reason to
expect, with changing climates,

stronger downbursts.

Derechos already
became more powerful

over the last 40 years

because the air is warmer
over the U.S. nowadays

than it was in the '80s.

So, this is a race to get
our building codes

and get our structures ready
to deal

with what could be
the weather of the future.

Protecting homes
and businesses will reduce

the financial cost of
future downbursts and derechos.

And better forecasting
is also essential.

But weather forecasts
face limits

because of the inherently
chaotic nature

of the atmosphere.

If you start a model

with slightly different
initial conditions,

the end results can be
very different

based on some
very simple differences

in the initial information
we put into our models.

We can't
actually accurately predict

the weather
beyond about 14 days.

By updating the model every
few minutes with live data,

the forecast can be nudged back
to reality.

But data quality is crucial.

And some of the best data comes
from space-based instruments.

French Guiana.

An Ariane 5 rocket delivers

a 4.2-ton next-gen
weather satellite

into a geostationary orbit,

where it stays positioned
above Europe and North Africa.

It's one of three satellites

that will be co-located
in the same orbit

to probe
the region's atmosphere.

Olivier Brize is part
of the team

behind this new satellite
system.

The Meteosat mission
is a geostationary satellite.

You have a constant
and stable view of the Earth.

The aim is to improve
the short-term nowcasting

and also to provide alerts
on a severe weather event

on a very short term,
within one or two hours

and within a very small area:

on a valley,
on a village, on a town.

These satellites will provide
a 3D profile

of the atmosphere
above Europe and North Africa,

including humidity,

wind speed,

and temperature.

This real-time view
will enable forecasters

to spot the warning signs
of an atmosphere

primed to produce downbursts:

rapidly cooling cloud tops

or banks of dry air around
developing thunderstorms...

...allowing forecasters
to give downburst warnings.

For us working on this project,
we are convinced

that we are in a position
to save lives.

So far, the U.S. has

no equivalent geostationary
satellite system,

but there are plans
for future deployment.

If we want to save lives
around the world,

we really need
global observations, and so,

the best way to do this
is to build satellite platforms.

We've made progress
with the forecasting

of extreme downbursts
and derechos,

but there's still
a lot of things

that we don't know about them.

However, our modeling systems,
our observational systems,

and our field campaigns

have allowed us
to really move forward

with understanding these storms
and better predicting them.

Earth's atmosphere is a cauldron

mixing warm, wet air
with cold air above,

a mixture that generates
huge thunderstorms.

And as the Earth's atmosphere
warms,

it will hold more moisture
and more energy to fuel them.

As we move forward
with new satellite technology,

I believe that our ability
to forecast these systems

will be even more improved
in the next zero to ten years.

But while we wait for forecasts
to catch up,

more severe winds,

more deadly hail,

and more extreme rainfall

will mean
more devastating rain bombs.