Unveiling Weather's Secrets: The Science Behind Clouds, Rain, Hail, and Avalanches

whether one of the most astonishing forces on earth capable of both devastating power and spectacular beauty

wherever you live on the planet whether shapes or world yet for most of us how it works is a mystery to really

understand whether you have to get inside it so I'm going to strip weather back to

basics science uncovering its secrets in a series of training ambitious and

sometimes just plain unlikely experiments to show you whether like you've never seen it before

water lies at the heart of our weather but not just as rain because water can transform itself redefining its powers

in the process creating the fastest the slowest the softest and the hardest weather on earth often changing from one

to another with alarming speed and striking consequences in this program I'll reveal water in all

its shapes I'll capture a cloud okay little ad let's see what you got to

see just how much it weighs discover why hailstones are able to do so much damage find out what would

happen if rain fell in one big lump it's amazing isn't it and I'll experience water and its most

voraciously powerful form as an avalanche speechless genuinely speechless all our

everyday weather appears to come from the clouds they're the best clues most of us have as to what the weather is

likely to do next they dictate if it's sunny or dull and there where all our watery weather seems to come from but

how what exactly is a cloud come on you've done it if not you should gazing at clouds dreaming up shapes

and the next time you do two things you should know about plans that might just change the way you think

number one clouds are really heavy even that fluffy little cumulus could weigh as much as two elephants and secondly

because of that weight all clouds are falling slowly steadily down to earth I know both those things sound pretty

unlikely which is why I'm going to put them to the test and I'm going to start by trying to

discover just how much a small cloud really does weigh there I know I'm not the only one who when presented with a

sign on a bench saying wet paint has to touch the bench just to check it really is so when I heard that a cloud can

weigh as much as two elephants but I'd to check it out the only thing is it turns out that weighing a cloud is a bit

more of a faff than checking to see if paint is wet obviously you can't just hang your cloud of a spring balance or

pop it on a set of scales but you could measure the moisture in it and work it out from that so I thought what if we

could fly a giant ball of cotton wool into the cloud to gather the moisture as an idea it needs a bit of finessing yes

so I've got an engineering mate of mine to win out some of the wrinkles and he came up with this okay so it's not

actually cotton wool it's an industrial version ceramic wool and it's not one solid ball either my friend reckoned

that by making the center hollow it would double the amount of wall that came into contact with the cloud

he calls it his sky sponge and then we've got that to put it in the cloud it's all fairly

standard stuff so first off let's check how much this sky sponge weighs dry that's 37 kilos which for a sponge is

already pretty heavy but we need that weight to be able to fly it accurately especially when the pilot it's someone

not that used to carrying Freight I know it's not a good start [Applause]

but as nobody is ever done anything like this before I'm as good a choice as anybody

in the end it was deemed not a job for an amateur no matter how enthusiastic so I took a co-pilot Andrew with me to keep

an eye on things mostly on me [Music] [Applause]

so helicopter check basket full of highly absorbent ceramic wool check all I need now is a nice that LeClair to dip

it into and that's not as easy as you might think because when you get close to them

clouds are well very Norma's you look at it from the ground they all look perfect and fluffy and spawn get up and they're

looking Tyler different I'm gonna find a nice individual one drop in it and see how much water it brings out of it

the shimmy won't soak up the entire Claire that we'll be left with underslung the weight of two elephants

that'll be bad a full-grown African elephant weighs on average four and a half tonnes

a quarter of that would pull my helicopter straight out of the air but if I just weigh a fraction of a

cloud then multiply my results it should give us some idea how much a whole cloud actually weighs a convicted

about the one in front up here yes a nicer bright cloud has been sourced it is quite important the helicopter itself

doesn't go in the cloud you have to remain visual with well pretty much everything I need to fly low enough to

dip the sky sponge into the cloud but high enough to keep the chopper above which is trickier than it sounds well

for me right well that's all ran bad first time around I miss the cloud altogether this is a fairly unusual

exercise plan connected that's my excuse anyway this hole will do a treat

okay little cloud let's see what you got [Music] close up the cloud seems so wispy it's

hard to imagine we're going to soak any water on the tour [Music]

okay we dipped it let's get this thing down and see what we've got well it's wet that's a start but how wet

have we managed to collect enough moisture to make a difference on the scales we have 10 whole kilograms of

difference I know that doesn't sound like much but look at the size of the cloud then look how much of it the sky

sponge flew through just that small section had 10 kilos of water in him if every section that size weighs the same

then that little cloud must be getting on for well not quite 9 tonnes lot [Music]

and a good-sized thundercloud might be ten kilometers tall and ten kilometers wide

which would make its total weight more like a million elephants Dorothy prefer about 60,000 jumbo jets

so how on earth does all that weight stay up there to find that out we're going to have to build a cloud of our

own [Music] right what I've asked to achieve here is

an indoor cloud what I've got is a cattle trough full of water and I don't know what these things are fortunately

what I've also got is Jim who is an atmospheric scientist and can hopefully help I don't what is this how's it gonna

work so this is how we're going to make something akin to clouds rice is not a it's not a cloud but it's a closest

we've got to a cloud making machine right so what we've got in here are some ultrasonic humidifiers so you quite

often see these sorts of things at garden centers and things like that then just they just produce very very fine

mist garden centres sounding less high-tech now I'll be honest they're masquerading as nice ornamental

devices but secretly they're cloud making devices well there we go well come on then make it work so what we

need to do is turn this on don't man up there you go suddenly miniature clouds appear and that's just by breaking the

water molecules down into smaller bits of breaking the liquid water yeah into just very very tiny droplets of water

these garden pond devices turn the water into tiny droplets and that is exactly how a cloud works clouds float because

the water drops inside them are so small and so light what's the difference in size how big is a droplet of this

competitor a droplet of that is 5 microns but that means absolutely nothing too small okay

so but the rain droplet you can you can get your head around the size of raindrop the raindrop it's about two

millimeters so the difference in size between these and the rain droplet is the same as if you've got a sugar cube

and a caravan and on which is the caravan so the caravan it's the rain droplet

right and the sugar cube is these tiny little droplets right well that is working

the humidifiers have split all our caravans up into billions of sugar cubes okay let goes on okay but to really

complete the effect we want to see if we can get those tiny moisture droplets to float in the air what's in the funnel

now and we'll see clouds emerge there it is weirdly it feels dry hard to believe our sky sponge managed to soak this

stuff up so this isn't just something that looks a bit like a cloud this is pretty close to again these are just

droplets of water very very small droplets of water and nuts that's what a cloud is is that Jim not being critical

of your cloud but it looks a lot more frantic I think clouds is just solid state really just drifting what you're

seeing here is what's happening around the edge of cloud it's constantly changing so you get up close to a cloud

and it's really quite busy yes so whilst I'm very impressed with your homemade cloud here it's kind of not

[Music] [Applause] now this might look like overkill but

actually our cattle trough is surprisingly heavy just like the water in a real cloud and I do need to get all

that water off the ground to check that second fact are all clouds really falling back to

earth [Music] Jim and I wait with bated breath we

might have made the water droplets small enough to float but it's true once they're up in the air they drift back

towards the ground so this effect where I can see it rolling over the top and then some falling that's accurate yes

our cloud is dropping out so if you look at clouds with binoculars or something like that you'll see you'll see bits of

streams of cloud so because this is small it all looks faster but if this were as big as a real cloud this effect

this exact effect is what's going on all the time yes just continuously all the time around the edges of cloud around

the periphery of clouds with all this this process going on all the time so there you have it clouds are heavy

and they are all falling slowly down to earth [Music]

it's just the most evaporate before they ever get there in fact the typical lifespan of a small

cumulus cloud is only 10 to 15 minutes but while they're up there they act as a sort of public transport system for

water carrying it from one place to another until either the service goes off duty

or they dump all their passengers at as rain there are about 13 trillion tons of water being moved around in the

atmosphere and every day about 1/10 of that comes crashing back down to earth

sometimes these storms are incredibly intense the quickest on record dumped 12 centimeters of water in just eight

minutes the heaviest managed nearly a meter and a half of rain in under 10 hours

and so to my home territory where on average it rains one day out of every three this is my favorite place in the

entire world it's in the Lake District Hollister pass running down to Lake butterman I've been coming here for 27

years it has one of these best views in the world I've seen it once that's because this specific place is the

wettest in England on average four meters of rain falls here every year specifically to talk to you about rain

it's not actually raining yes sprinklers in the wettest place in England however this will suffice

perfectly to allow me to show you what I wanted to show you puddles puddles hold the key to seeing how those tiny cloud

droplets turn into raindrops we can't look into a cloud to see how raindrops form but we can get an idea of what's

going on by looking in a puddle [Music] as the raindrop hits part of it is

attracted to the water what bounces back up is a smaller droplet about half the size when that

droplet is the same thing happens again around half of it stays in the puddle [Music]

now imagine that in Reverse and upside down the puddle is declared a water droplet doubles in size by

attracting other water droplets please stick on in a process scientist called coalescence

it increases again and again until it's so heavy it falls away and that is roughly how rain is formed

[Music] it feels right like this this is how it feels here which is just as well because

I've got one more thing I want to tell you before I get them to turn these sprinklers off and it's about the

official difference between rain and drizzle not closely at a puddle surface if the drops are splashing like here

then it is rain but if there are no splashes there it only qualifies as drizzle officially clever isn't it

splashes rain no splashes drizzle but what they've both got in common is that they're just too heavy to be held and

loved we talk about heavy rain but water is heavy very heavy give us an idea of just

how heavy we are about to see what would happen if all of four adele's four meters of water fell in one go now

obviously we can't get a bigger the size of the Lake District so we're just going to recreate what it's like when four

meters of water hits one small area so we have four cubic meters of water in the bucket which amounts to four tons at

height then beneath it you'll see we've found a car for scientific purposes let's see just how much damage that

amount of water can do hmm looks like rain [Music]

yeah pretty brutal but I shouldn't be surprised because the water actually weighed four times more than the car and

the needed every minute of every day 900 million tons of rain land on our planet

that's about the same amount of water as in all 16 lakes of the Lake District [Music]

or they're going to notice but it does prove the point water is really heavy that is just the annual rainfall for

Borradaile we're up in go on holiday all of my life explains something about it it's amazing isn't it luckily this could

never happen with real rain not even in a tropical storm where sometimes it feels that the heavens have

literally opened partly because as we saw earlier raindrops fall the moment they get heavy

enough and partly because of what happens to rain as it falls

[Music] to show you what I mean I'm hard at work building a sandcastle

and professor jane Rickson from Cranfield University is filling a plastic bucket there are always kids

like you on the beach one ok so what's all this about well pour water on a sand castle and you completely flatten

no surprises there but rain doesn't fall from waist height it falls from clouds that are at least 300 meters above the

ground and that makes all the difference let me show you by building another sandcastle and throwing the water off

something just a little bit higher [Music] they're obviously this isn't as high as

a real cloud they start at around 300 meters is Terry's 30 but it's tall enough for what we want to do okay

Richard yeah wrong side how was I to know let's try it again and so another bucketful leaves the

tower but what arrives they love is rain and there it is it's still standing so why why is it if I throw the water

from up there you'd think it would smash it to bits even more but it's still standing what's the difference well what

happens is you were throwing that water down air resistance the turbulence in the air is overcoming the surface

tension of that lump of water breaking it into smaller drops you want to go and see that you do it again yes I'll get

the bag of the water [Music] as the water falls it meets air

resistance and the larger the lump of water the more resistance it experiences that friction breaks the water up into

smaller pieces sometimes inflating the drops like parachutes before blowing them apart the further they fall the

smaller those drops become until finally they're so small that the air has little effect on them and they land as rain so

that's why the water landed in drops and didn't smash it rather than a big bucket shape lump that's right and in fact you

can actually see the point at which that lump starts to break up into those smaller drops well you can if I climb

the tower again [Music] it actually happens surprisingly quickly

within 10 meters there's enough air blowing on our bucket full of water to break it down into drops if our digger

had been just a few meters higher then the cup might well have survived so even if it was possible for water to fall out

of the sky in one big lump by the time it got to the ground it would still be rain because they break down like this

the average raindrop ends up about two millimeters across but there is a way the water can fall out of the air in

bigger more dangerous pieces by shape-shifting into ice now most of us think that when we see ice falling out

of the sky its hail so what if I told you this wasn't hail at all sure it looks like hail but it can't be hail you

can't get hail in winter that only happens in summer I know you think you've seen hail in winter but trust me

you haven't what you've seen is this ice penny ice pellets have formed when a snowflake

partially melts on the way down losing all its pretty branches and then refreezes forming a small ball before it

hits the ground just to make things even more confusing in North America they call this sleet which over here means a

slushy mix of rain and snow either way this is not hail hail is something entirely different

[Music] Charles Knight has been studying hailstones

for the last 50 years and in his refrigerated laboratory in Boulder Colorado he offers to show me exactly

how hailstones are different by sawing one in half it's very simple we just use a hobby bandsaw like he's just gonna

slice in half yes I know if you had that has done Oh about 10 years actually but it's worth it as soon as Charles

opens it up the difference is revealed Heil is made of layers and there you can see one layer there anyway so when is

that the circle yes but in the bigger hailstones there's much more obvious layering this is an example of a really

what we would call it a giant hail it's enormous its enormous yeah yeah but that's

obviously not gonna stop him cutting it in half even though this one is 15 years old

this time the layers are crystal clear if you make a thin section then you can really see the layering that's a slice

right through that's absolutely beautiful that's really telling his own stories just like the rings of a tree

these layers chart the story of how this hailstone groom it's a story that starts with a

thunderstorm and thunderstorms only tend to happen in summer because of the height of thunder clouds some of the

water droplets inside them freeze but the powerful updrafts created by the warm weather keep the droplets supported

in the cloud where they collect more water with new layers freezing on in a separate shell until finally there are

so many layers that they're too heavy to be supported and they fall to the ground which got me thinking because it's made

in layers does that mean hail is stronger than a single solid ball of ice you make wood stronger by laminating it

you make glass stronger by laminating it so does laminating ice make it stronger certainly hail is powerful it causes

over a billion pounds worth of damage a year but is it any harder than conventional ice

[Music] to find out we're gonna have to go into uncharted territory with an experiment

that hasn't been done before using that yeah I know it looks like and lent the plastic pipe on some tables in a field

and to some extent well it is but you should see what it's about to do to that table tennis bat its inventors Purdue

University's Jim Stratton and Craig's Eric wanted to see just how fast they could get an ordinary ping-pong ball to

fly [Music] and the answer using this contraption

turns out to be very fast indeed [Music] it's astonishing this projectile is

moving when it comes out of there oh yeah about 919 miles an hour so you brought along your device which

is if you think about it a sort of nightmarish automatic serving machine and you've agreed to help us yeah okay

right so here's the plan we're gonna see which is harder ice or hail but first of all we're going to make some hailstones

we've already seen how much of a faff that is and even for Mother Nature but luckily Jim and Kraig have a plan a plan

that starts with dry ice the greatest pop video a pop video starring a bead on a bit of stream the dry ice makes the

bead really really cold to rolls well before it's dropped into cold water if you'll notice every time he puts it

in there you can hear just a little bit of a crack you can hear a little bit of fizz and that's the water

instantaneously freezing to the outside so that's one layer of ice ran that little seemingly very small air how long

does this take about 10 minutes oh god please do we need quite a few and they need to be the size of ping pong

balls to fire them from Jim and Craig's gun can I go yeah right dip it in here

very quickly into there that's it it's already the size of a pea I'm just I'm just suggesting we'd probably need to

find a way of mass-producing these I mean this is the land of Henry Ford right one is good

we can try three and now you've tripled your efficiency haven't I half a night sometimes on TV

we don't do things in actual time this is one of those occasions [Music]

you gonna do anything I'm reading this there's no words you just looking at the pictures it's my turn again yes

oh you've been busy [Music] Hales ready they're done they are done

magnificent they are as well look at that okay they might need a little bit of rounding off to get them down the

barrel of the gun but the size is good say goodbye one excellent three of 30 we're gonna throw some more away so we

have something to compare them with we've also frozen some water into ordinary ice using a few of Craig and

Jim's spare ping-pong balls as remodels so we've got solid ice and we've got Hale which is ice in layers time to put

them up against each other to see if there really is a difference and we can't resist starting with one of our

homemade hailstones I'll give you the honors again something see quite dramatic yeah believe it or not we're

breaking new scientific ground here so to make sure we capture any differences between the ice and the hail we're

recording everything at ultra-high speed and sure enough our cameras capture every detail from the plastic seal

topping off the tube to a hurtling hailstone punching through the talk is it worth experimenting now with just

seeing how much more resilient one is than the other yeah we brought plenty of materials we can shoot out so we can

actually shoot - I'm at the same thing and see well want to go through one won't go through and the type of force

that we have and that's exactly what I was gonna do that all right so here's the setup we've got lots of different

sorts of wood and we're going to take two shots at each piece first with plain ice then with our homemade Hale

first up chipboard right three two one ice straight through Hey straight through okay slightly thicker

piece of chipboard same result plywood [Music] the ice barely dented

come on hail three two one well there is a difference the hail splintered the back of the plywood let's

try a slightly thinner piece this time the ice barely makes it through the hole it makes is far smaller than the

projectile itself right fingers crossed [Music]

awesome did it work what happened - and there's your impact yeah that's why the way

through yeah you fellas completely different same piece of wood same shooting speed

different results in slow-mo you can clearly see how much of the ice ball never makes it through the board well it

might be crude but that is on a hoped would see this mark here that's from the straight ice barely getting through that

is our homemade Hale with its laminated layers around it clearly a more fearsome projector

[Music] both balls are made of frozen water so you wouldn't expect any difference in

how hard they are but the layers inhale do appear to make it stronger so summer hail does seem to be harder than winter

ice but water can shape-shift into something even more dangerous naturally quicker than hail with a

mightier punch than hail and what it is might well surprise [Music]

this is how most of us are used to seeing snow move delicate flakes floating gently down to earth

floating so gently that a snowflake can take nearly an hour before it finally reaches the ground

[Music] traveling at just four miles an hour little more than walking speed

and yet snow can be the fastest form of water that there is [Music]

because when it's in an avalanche it can hit 80 miles an hour in six seconds flat and then well it just keeps on

accelerating the fastest one ever recorded on max and Helens in America taught a staggering 250 miles an hour

so how can snow move down a mountain faster than water can Walter Stein Coppola of the Institute for snow and

Avalanche research is trying to find out how that incredible speed is possible by starting an avalanche every zone Walter

yes is this where it's gonna happen that's absolutely you can see it quite nicely now it's the whole slope you see

to spontaneous avalanches already and we're gonna try to release the avalanches from the very top

well tell those to our launch is made it's already happened this is all over see there's plenty of snow still on the

slope ok and I - this is a really good indicator for us that there is the potential to produce noise Evelyn and

then when that's going on you're going to be conducting experiments and learning I mean this is part of an

ongoing piece of work for you isn't it it is it is actually my part of my PhD thesis and this data is really essential

from my work yes right there are several different types of avalanche but the fastest by far is what's known as a dry

powder avalanche and that's the type we're hoping to get if he can trigger a dry powder avalanche

Walter can find out more about how they moved so fast and we've offered to help by putting a barrage of slow-motion

cameras on the slope we're not gonna mess up your PhD I will tell you afterwards but I would appreciate if you

don't do that if I do send him the bill oh let's hope it doesn't come to that but I would like to add an extra element

into his experiment so Walter can I place these on the slope if there are known distance apart I thought I could

time when the front day head we call it the front that the front of ever lunch pass is one of these yes I can time it

over that distance and I can work out how fast it's going sure sure that's a nice approach you can do that yeah thank

you very much right well do I just need a helicopter [Music]

okay well that's that sorted but now we need to work out how to fly our fences into precise positions without

triggering an avalanche ourselves our safety team have been thinking long and hard about the best way to do it and

what they've come up with is dangling someone on a bit of rope this someone in fact

who apparently enjoys this kind of thing [Music] [Music]

if you single coolest thing I have ever witnessed that man is without a doubt the best helicopter pilot ever seen in

action I mean that sky sponge was difficult enough I'm just leaf lying that close to

mantids and sheer rock faces in this gusty wind each angel weather just that let alone with another bloke Daniels

with a piece of road below you and then below that a huge belt basically wooden sail speechless genuinely speechless

Walter has told us where he expects the avinash to fall so we position the first fence slap-bang in its path

but the conditions up here are very changeable as we discover when we try to fly the second fence

suddenly the winds quicken and start to gust alarming at any moment the whole fence could be

dashed into the side of the mountain taking that load with it not to mention the helicopter

and the fence needs to be exactly 100 meters from the first one never have the words rather him than me

be more directly applicable it's death so everything is now in place my two

boards I know where 100 meters are parked when the front of the ambulance passes the first one I'll start the

stopwatch on my phone stop it when it passes the second and we'll get an idea of the speed and I do know we're gonna

be surprised has something that a little snowflake can take an hour to drift down out of the sky can suddenly be part of

something so fast and so powerful all we have to do now is wait for them to trigger it

[Music] okay they're off thanks one thanks I missed it

but I suppose it does prove in a way just how fast an avalanche can be and luckily for me

slow motion cameras captured everything so let's take a look at that Avalanche again this is the moment that dynamite

is dropped from the helicopter causing this explosion at the top of the mountain

immediately it's surrounded by a powder cloud made up of 1% snow than 99% air this is a dry powder avalanche the

Avalanche accelerates down the steep incline until it reaches our first fence they're not exactly at the angle we

expected the leading edge passes the first one now and that particular bit of snow

reaches the second fence now almost exactly the same time the first fence is destroyed no wonder I had trouble timing

it Avalanche was actually only traveling at 25 miles an hour just 1/10 of the speed of the fastest one ever measured

but still faster than if we just pushed that snow over a cliff I want to know how that's possible let's imagine if

there's a chunk of snow at the top and then it starts to move what's happening to that snow from the moment it starts

to move down well first it will break into pieces and it gets rounded a bit and it also gets compressed and these

are the pieces which you can see up there they look like snowballs technically most of them are snowballs

yes these snowballs are the secret of what's going on underneath that powder cloud voltar offers to show me how

okay Walter this is like an avalanche how well you imagine an avalanche that's moving down a slope it's gonna pick up

snow like you are doing now and it's gonna put it in motion as in our tumbler here it seems you losing

your motivation come on keep on going one more you can do it perfect I think we're good there

you can see already it's compacting that it's breaking apart again then it's compacting again and at some point you

will end up with fall shape features it is magically making of course in an avalanche this is happening much faster

and it's much more violent process going on there but this is a slowed down version at exactly the same process and

you can see that sort of grinding rolling motion you can imagine happening perfectly that's exactly the case - so

understanding this will allow you to understand more about how fast it might go where it might go how it will behave

absolutely I would say they're quite down yeah yeah tonio perfect yeah turn it off please yeah so in here it's

Nobel's perfect snowballs right don't date me I mean that's seriously packed it's quite hard right I mean it would be

not that nice to throw it on it personally guess this one is everything he's looking over there and thinking

targets cuz I was the old ed tech cross-country runners he was scared for a second did you see Walter wants to

excavate the Avalanche to see how much snow it contained and I follow him into well a big hole because I want to be

sure whether it's these snowballs then make the Avalanche move so fast this is not answer because still going on

ongoing research but for sure it defines the motion of the Everland yes so you can't say for definitely yet as

scientists and I love it when you guys can't give a definitive answer yes I can because it's my research and if I say it

now I mean I need to publish this stuff first so would you ever end up with your Avalanche effectively rolling along on

like ball bearings or like when they used to build you know they got a huge stone and move it to

place to put it up it's a monument they roll along on logs wouldn't they is it like that I think it's you can

kind of say it like that yeah I'm I'm from a scientific point of view I'm not a hundred percent sure that's rubbish

don't you know that there are studies that say that really it's the ratio between the bigger cranes or the bigger

balls to the smaller poles that can significantly influence the speed and emotion of the events so you're not that

far off actually if your comparison is just jealous because it's my own day yes I know but ya know you you can publish

that back to me that would be something for I have to write it out yeah but you can't go to recent decades

put something on wheels and it can accelerate quicker than if you simply drop it and these snowballs

maybe the wheels of a dry powder avalanche [Music]

snow is the softest lightest way that water can fall to earth but an avalanche can move faster than any other type of

water four times faster than the fastest flash flood ever measured and it seems snowballs might well be the secret

[Music] of all the water on our blue planet only a tiny fraction is actually in the

atmosphere yet waters incredible powers of transformation that mean that that's enough to bring us all our clouds rain

hail and snow and with it all the everyday weather on earth [Music]