[narrator] We have uncovered
a remarkable planet,
a world of extreme weather,
alien landscapes,
and bizarre phenomena.
It's the most complex system
we know of in the universe.
That planet
is Earth,
and we are only beginning
to unlock its secrets.
When the world turns to white,
a blizzard is in full effect.
The wind is just cranking.
Oh!
You can't see your hand
in front of your face.
There's some snow out here.
Before you know it,
they've got two feet of snow
in 24 hours.
That's unbelievable!
It's almost sensory overload.
[narrator] The worst ones
can even strike you dead
in a blinding flash.
[thunder]
[meteorologist] Listen to that!
Blizzards are one of the most
intense weather phenomena
on planet Earth.
[narrator] When the surrounding
world disappears,
and death
is a real possibility,
you'll know it's a blizzard...
We're getting upwards
at times of--
[thunderclap]
[narrator]
...on Secrets of the Earth.
In a galaxy crowded with
frigid, hostile worlds,
planet Earth is
a life-sustaining sanctuary,
unless a blizzard
is suddenly unleashed.
[wind blowing]
The wind howls,
a three-dimensional
wall of snow
erases the surrounding world,
and life comes
to a sudden halt.
[man] The way a blizzard
can affect a community
is unbelievable.
It can knock out transportation
for days.
Everything comes
to a standstill.
Power outages,
all but a certainty.
[narrator] February 9, 2013.
Winter Storm Nemo slams
America's Northeast.
Blizzard conditions drop
two and half feet of snow
in some areas,
immobilizing some
40 million people for days.
[man] The principal factor which
makes a blizzard a blizzard
is the strong wind.
A blizzard is essentially
a dust storm with snow.
[narrator] A storm like this
is a rare event,
and understanding its secrets
means peering directly
into the clouds that
manufacture it.
Overlooking
Steamboat Springs, Colorado,
at an elevation of 10,500 feet,
the wind-ravaged Storm Peak Lab
is the perfect place
to uncover the secrets
of a blizzard.
To qualify as a true blizzard,
a snowstorm must meet
very specific criteria.
[man] We can tell that we're in
blizzard conditions
through this instrument
right here
and wind greater than
35 miles per hour.
As well,
we need to have visibility
less than a quarter of a mile,
which we're witnessing right now
because we have
whiteout conditions here
located at the summit
of this mountain.
[narrator] If these wind and
visibility conditions persist
for more than three hours,
the National Weather Service
labels the storm a blizzard.
[woman]
Blizzard warnings in effect.
[narrator] Scientists
typically study blizzards
by flying weather instruments
through the clouds.
But at Storm Peak Lab,
the scientists
live in the clouds.
This land-based
cloud probe array
uses a continuous laser beam
to sample and decode
the secrets of a blizzard.
[McCubbin] These three probes
allow us to study
the inner workings of a cloud.
So by looking at the snowflakes,
looking at the ice droplets,
and looking at the liquid water,
we can determine what's going on
with the blizzard.
[narrator] A blizzard
starts high in the clouds,
with tiny, super-cooled
water droplets
that seem to defy
the laws of physics.
These are droplets many times
finer than a human hair,
and what happens is that
these droplets stay liquid
even though the temperature is
far below the freezing point.
[narrator] A water droplet
can remain in this super-cooled
liquid state all the way down
to minus-40 degrees Fahrenheit.
But when that droplet
encounters a small particle
of dust, it freezes
around the particle
and forms an ice crystal.
For that crystal to evolve
into a single snowflake,
it must begin growing
like a tree.
This happens when random bumps
form on the ice crystal.
Water vapor molecules
begin attaching to
and growing branches
on the bump.
More bumps grow
on the branches,
creating a stellar dendrite,
a snowflake.
[Garrett] We have all
heard the phrase that
no two snowflakes are alike,
and of course that is true,
but it is true to
an extraordinary degree.
We start off as these beautiful
symmetric, pristine snowflakes
that you've seen in books.
Thousands of these
will collect together,
because as one snowflake falls,
it collects others.
And then it falls faster
and gets larger,
collects even more,
and there's this runaway
growth process
that leads to a snowflake
falling on the ground.
[narrator] The result is
powdery snow that's light
and virtually water-free.
In fact, every snowflake
is 90% to 95% air,
taking up ten times as much
space as liquid water.
It's extremely light,
extremely powdery.
It's very dry.
The snowflakes don't have
a lot of moisture.
They haven't
fallen through a cloud
that would give lots
of moisture to the snow.
[narrator] The surprising
secret about these
light-as-air snowflakes?
Most never make it
to the ground.
Many are attacked in freefall
by an army of super-cooled
water droplets.
If the snowflake
falls through a cloud
with lower temperatures
and humidity,
thousands of super-cooled
water droplets
freeze directly on its surface,
increasing its weight
and water content.
Because they live
inside the clouds,
scientists at Storm Peak Lab
can actually capture and study
the super-cooled water droplets
before they can find
a snowflake to freeze to.
[woman] This is actually
a cloud catcher,
so essentially we're catching
the cloud water,
or the rime.
Rime is water
that exists in a cloud
that's below freezing
temperatures,
and as soon as hits a surface,
it freezes immediately.
So rime ice
that you're seeing here
is similar to the rime
that collects to a snowflake
that makes the snowflake
heavier,
creating more heavy, dense snow
and blizzard situations.
[narrator] When a heavily rimed
snowflake falls,
it carries with it
a secret identity.
It is no longer a snowflake.
It's a graupel pellet,
and it contains as many as
one million water droplets.
When blizzards hurl millions of
tons of heavy graupel pellets,
planet Earth
becomes a danger zone.
Power lines collapse under
the weight of frozen graupel.
And when graupel accumulates,
the astounding weight
can even
bring down buildings.
December 11, 2010.
After nearly 18 inches
of dense graupel snow
accumulates on the roof
of the Minneapolis Metrodome,
the weight of the snow exceeds
the air pressure in the arena,
causing the roof to fail.
Luckily, no one
was inside the building
when the roof collapsed.
But blizzards
have other secret weapons
that can kill
without warning.
On planet Earth,
blizzards can turn deadly.
Sometimes what kills you
is what you can't see.
Windblown snow
can lead to a sudden,
inescapable whiteout.
[man] A whiteout is a situation
where you really
can't see anything.
There's so much snow
and it's blowing so hard
that you can't see your hand
in front of your face.
[narrator]
Shadows cease to exist,
removing the hard edges
that human eyes depend on
for reference.
[Wolf]
It's almost sensory overload.
It's--It's like being in a void.
[Haller] Whiteout conditions
can be extremely disorienting.
They're associated with
feelings of vertigo,
essentially where
you can't quite tell
which way is up or down,
which way is front or back.
[narrator] One of America's
worst whiteouts in 1888
claimed hundreds of lives.
[Steenburgh] The Schoolhouse
Blizzard was a snowstorm
with very strong winds
that struck the upper Midwest
at a time when a lot of kids
were getting out of school,
and the timing
couldn't have been worse.
[narrator] Dozens of children
walking home from school
are caught in sudden
whiteout conditions.
More than 235 people
across the Midwest
lose their way
and freeze to death
in the deadliest blizzard
in U.S. history.
Modern weather forecasting
has virtually eliminated
the chances of this scenario
ever happening again.
But when commuters hit the road
during a blizzard,
all bets are off.
Driving conditions
can be so dangerous,
cars are often
abandoned in place.
Supercomputers with
sophisticated snowfall models
can predict blizzard conditions
and potentially save lives.
But what if the very foundation
of these snowfall models
was wrong?
[Garrett] We have sophisticated
instrumentation for measuring
winds, temperature, humidity,
and many other things,
but currently nothing
for accurately showing
what types of snow
are falling where.
[narrator] At the Alta Ski Area
in Utah's Wasatch Mountains,
a group of scientists
is out to uncover
the secrets of the snowflake.
And they may be on to something
that the world's
top meteorologists
have all but ignored.
Using high-speed photography,
the Alta project
is cataloguing thousands
of snowflake shapes
and observing
their aerodynamics.
[Garrett] Different types
of snowflakes fall faster
than other types of snowflakes,
and being able to represent
what sorts of snow form
and how fast it falls
is a key ingredient
to being able to make accurate
weather forecasts.
[narrator] Current weather
supercomputers
base their blizzard forecasting
on a few hundred
snowflake photos
from another era.
In 1973, University
of Washington scientists
spent weeks in
the Cascades Mountains
photographing snowflakes
by hand.
[Garrett] These guys collected
individual snowflakes,
and they put it
under a microscope,
and they photographed them
one by one.
[narrator]
Through human contact,
the delicate snowflakes
were routinely damaged.
It's these same flawed
snowflake samples
that state-of-the-art
computer models use
to forecast a blizzard.
The Alta project
could revolutionize
snowflake science.
[Garrett] Our snowflake cam
is unique because it photographs
snowflakes in freefall
without touching them.
Inside this box are three
high-speed cameras.
The snowflakes that fall
through this hole here
are illuminated by
these three lights.
What this provides us
is an unprecedented view
of what snowflakes look like
as they actually are.
[narrator]
What nature manufactures
is a wide spectrum of designs,
from the lightest,
driest snowflakes
to the most heavily rimed,
wettest graupel pellets,
and everything in between.
The high-resolution photos
could one day lead
to up-to-the-minute
blizzard tracking,
critical information
that could one day
save lives.
In some parts of the world,
blizzards are a freak
occurrence.
But in others,
they come relentlessly.
This is America's secret
Blizzard Alley.
February 9, 2013.
Winter Storm Nemo demonstrates
the power of a blizzard
to shut down the entire
Northeast region
of the United States.
Despite the intensity
of winter storms
in the eastern half
of the U.S.,
it's not the blizzard capital.
You've heard of Tornado Alley.
America's secret Blizzard Alley
is the upper Midwest.
[Steenburgh] You're talking
about North Dakota,
South Dakota,
and western Minnesota.
The upper Midwest is generally
a very windy place,
but also,
you don't have any trees.
So snow can be blown very easily
and transported
for long distances.
Trees help keep
the winds near the surface
down a little bit.
[narrator] Wind speeds often top
70 miles per hour
on the open plains,
blowing snow horizontally
and delivering an average
of three blizzards per year.
Blizzard Alley produces
strong winds,
but it does not deliver
the most snow.
That distinction belongs
to America's Snowbelt,
those cities and towns that are
just east of the Great Lakes.
Here, nature's snow machine
is called the lake effect,
a powerful alliance of water
and frigid winds.
Some of the biggest,
baddest snows
are lake-effect snows.
Yeah, you can see the wind
down here.
It's just howling off
Lake Superior.
You get these warm waters--
Lake Erie, Lake Ontario,
any of the lakes, really--
and it's ice cold outside,
and next thing you know,
Cleveland or Buffalo
is buried like that.
You're getting snow
that's coming down
two, three, four inches an hour.
[narrator] A single blizzard
can deliver five feet of snow
or more and can last
up to several days,
causing millions of dollars in
damage and lost productivity.
[Monmonier] The principal parts
of a lake-effect-snow recipe,
you have to have a large lake,
which is a reservoir of heat.
Lake Ontario is one of the five
Great Lakes,
and it's a tremendous source
of heat,
which is picked up slowly
over the summer.
[narrator] When a cold,
Arctic wind
sweeps across the warm lake,
it picks up
the evaporating warm air
and becomes infused with
a massive load of water vapor.
As the combined air mass
moves away from the lake,
it encounters trees,
buildings, and hills
that create turbulence.
The instability causes
the water vapor to condense
and fall out as
lake-effect snow.
Typically by January,
cold weather
partially freezes the lakes.
As the ice forms,
it can build a platform
for one of the deadliest kinds
of blizzards,
one that doesn't require
falling snow.
There are blizzards that are
simply called ground blizzards,
and it's just snow on the ground
that's being blown by the wind
that causes the blizzard.
[narrator] Winter, 1977.
Buffalo, New York,
on the shores of Lake Erie.
At an average depth of 62 feet,
it's the shallowest
of the Great Lakes
and the first to freeze.
Over several weeks,
three feet of snow accumulates
atop the frozen lake.
On January 28, a frigid
70-mile-per-hour wind
picks up
10,000 square miles of snow
and hurls a ground blizzard
at Buffalo.
[Bettes]
The wind is just cranking,
and it's blowing snow
off the ground
and it's causing
whiteout conditions
and it's impossible to drive,
it's impossible to walk.
[narrator] The winds pile up
drifts as high as 30 feet.
But there is
a secret blizzard effect
that no one can prepare for.
It arrives in a spark
of high voltage
and disappears
in a blinding flash of light.
[thunderclap]
When a blizzard descends
on planet Earth
with shrieking winds
and blowing snow,
conditions are treacherous,
but they are not unexpected.
There is one secret
blizzard phenomenon
that is always unexpected.
It's called thunder snow.
When you have thunder snow,
you know you have got
a serious snowstorm.
[thunder]
[Steenburgh] It really causes
your hair to stand up on end
because you never
hear it coming.
There's usually only a--
a couple bolts of lightning,
and then it's over,
so that first bolt really
catches you off-guard.
[thunderclap]
[narrator] Occasionally,
video cameras
capture its arrival,
like during a news report
by meteorologist Jim Cantore.
He's doing his live reports
on Michigan Avenue
during this blizzard in Chicago,
and all of a sudden, crack!
[thunderclap]
[Cantore] Listen to that!
And everyone just freaked out,
especially Jim.
[Cantore] Son of a...
That's unbelievable!
This is rapid-rising air motion.
And when you get ice crystals
that build up
and you get electricity
that builds up a charge,
both positive and negative,
within that thunderstorm action,
you're gonna see a bolt.
[thunder]
We just had a lightning strike
and thunder here.
And it just shocks you because
you're not expecting it in snow.
[narrator] Humans rarely hear
a thunder snow strike.
The reason?
Because snowflakes are 95% air,
they are natural
sound suppressors.
A summer thunderstorm
can be heard
from up to six miles away.
Thunder snow is only detectable
within a three-mile radius.
The winds have been gusting
to 50 miles an hour...
[narrator] In the 21st century,
blizzard images are broadcast
as they happen.
Everywhere, that is,
except the one place
with the worst blizzards
on planet Earth.
Antarctica only experiences
two inches of snowfall
annually,
but that's enough to sustain
eight blizzards per year.
[Steenburgh] Wind can transport
about ten times as much snow
horizontally as can fall
from the sky in a storm.
And even if there's not snow
falling from the sky,
if the snow on the ground is dry
and can be picked up
and moved around very easily,
the wind can basically
create a ground blizzard.
[narrator] Most of Antarctica's
snow never melts.
It's driven by winds often
exceeding 150 miles per hour,
and the ground blizzards
can persist for a week or more.
During a storm in July of 1972,
wind speeds were clocked
at 199 miles per hour.
Despite the savage conditions
at the polar regions,
Earth is not a frozen planet.
The momentary chaos of a
blizzard is a weather glitch,
a sudden anomaly that,
without a doubt,
is one of the wildest weather
events on planet Earth.