Episode 2 Storm Troupers: The Fight to Forecast the Weather

It's variable.

It's hard to predict, it has a massive impact

every hour of every day.

It is, of course, the weather.

I'm Alok Jha

and I'm a science journalist.

I want to investigate how, through history,

people have tried to predict what the weather will do.

That's what this series is about, the story of the extraordinary

characters who took on one of the hardest problems in science.

How to forecast the weather.

In this episode:

The ambulance driver who dreamed up the first

weather computer in the trenches of World War I.

The scientist who tried to predict weather disasters

and helped unlock global climate systems.

And the weathermen who risked their lives to help

win the Second World War.

I thought sometimes that I wonder if we can get back all right.

This is a story with a dark side.

All of the accomplishments that scientists made

in understanding the weather came out of catastrophe...

natural disaster...

and war.

This was half a century which tested meteorologists to their limits.

These are cirrus clouds.

Probably the most beautiful clouds in the sky.

They are pale and wispy.

Some people have called them mare's tails or compared them

to long strands of hair.

Cirrus clouds have fascinated skywatchers for centuries.

They are said to signal stormy weather.

There was actually a maritime saying,

"If you see mare's tails, carry low sails."

Because bad weather's on the way.

But in a village in Leicestershire in the 19th century,

the local rector decided to take a scientific approach

to studying cirrus clouds.

His name was William Clement Ley.

And in Ashby Parva, he had a reputation as a weather prophet.

During harvest time,

Ley would post his weather forecasts on these rectory gates

and it's said that farmers would come from miles around

to read the forecasts and only then would they decide

when to cut their corn or their hay.

Ley knew that the livelihood of the farmers depended on the weather.

A bad harvest could bring hardship to entire communities.

So Ley made it his life's work to try

and find a way to predict storms and bad weather.

He used a simple instrument.

It is thought he designed and built his own.

This is a nephoscope and it's probably less complicated than

the one that Ley would have built, but the principle is the same.

All around, there are 360 degrees of markings.

The zero points directly north and once you've set it up properly,

you just watch the clouds in the mirror.

Ley spent years plotting the clouds.

Cirrus clouds fascinated him.

They're the highest in the sky, at 18,000 feet and above.

For him, clouds were not just things of beauty and grace.

He realised they could provide clues

which could help to predict the weather.

This is a diagram made by Ley in 1877

and it shows a model of a depression,

a low-pressure weather system,

of the kind that blows in from the west to Britain all the time.

It's this that brings unsettled weather to the UK,

rain, clouds, even gales.

Low-pressure systems often dominate the weather

in mid-to-high latitudes

around northern America and northern Europe.

Understanding how they worked was the Holy Grail of meteorology.

Ley had cracked something extraordinary.

The structure of a low-pressure centre in three dimensions.

On this diagram, Ley marked the direction of the winds.

You can see at the bottom where these solid lines are,

the winds are rotating counterclockwise

around this central area,

and the whole pressure system is moving that way.

But as the winds move around here,

they move up and the winds at the top are diverging outwards.

Modern satellite images show that Ley was remarkably accurate

in working out what was happening thousands of feet up in the air.

Because of his careful observations of cirrus cloud,

Ley identified that on occasions, the upper flow was moving

at tremendous velocities and he measured speeds in excess of 150mph.

That would later be termed as part of the jet stream.

The jet stream is now recognised as a crucial part of how weather works.

But at the time, it was completely unknown.

Ley also gathered observations showing that cirrus clouds often

appear before an approaching low.

So he called for an international forecasting system to be set up.

Observers along the coasts of Europe could spot cirrus clouds

approaching and telegraph the data to a central forecasting office.

Improved storm warnings could have saved lives

in the 19th century.

In the age of sail, shipwrecks were all too common

and rural communities were blighted by extreme weather events.

Towards the end of his life,

Ley wrote a book pleading with the scientific world to take note.

But the scientific establishment didn't listen.

And his idea of using cirrus clouds was stillborn.

William Clement Ley is buried here in this quiet grave in Ashby Parva.

He had a sad end.

Towards the end of his life,

he was admitted to a mental institution in London.

In 1896, he was found dead.

An inquest found he'd killed himself while "of unsound mind".

It's said the local farmers gathered together

one more time for his funeral.

It's difficult to overestimate Ley's work.

When he died, any idea of using upper flow

essentially died with him.

There was this huge gap of about 40 years that was

literally lost in terms of meteorological advancement.

But, as we'll see, Ley did leave a legacy.

One which was to inform future scientists

in their search for the secrets of the skies.

At the beginning of the 20th century,

the Met Office was based in Central London above a piano shop.

It was underfunded

and did very little original research into the upper atmosphere.

It took the outbreak of war in 1914 for modern forecasting to be born.

The First World War was a human disaster.

When fighting broke out, the British Army saw no need for meteorology.

They planned to fight wars the old way.

But soon, that had to change.

By 1915, there was a grisly stalemate on the Western Front.

The British Army's high command realised they were facing

a new type of scientific, highly technological warfare

and it was something they were hopelessly unprepared for.

This was a war using new technology.

One of the most significant was airplanes.

They were mostly used for observational purposes over

the battlefield.

They were fragile,

lightweight machines at the mercy of strong winds.

Commanders soon realised they needed scientific input.

So, in spring 1915, the Royal Flying Corps sent a telegram

to the Met Office asking for their help.

An organisation called the Meteorological Field Service

was set up, commonly known as Meteor.

It set about gathering weather data along the front line.

They started off by using thousands of these things,

pilot balloons. And the method was very simple.

They let them off and then two men with the odd light would track them

as they rose through the air.

This was a basic way of working out the speed and direction of the wind.

But more sophisticated instruments were needed, because the war

was getting more complicated, especially for artillery.

Artillery was the most important weapon

system in the whole of the First World War.

1914 to 1918 marked a revolution in warfare.

It was the first time that artillery became the predominant

killer on the battlefield.

In the 19th century and the wars of Napoleon,

artillery had accounted for between five and 10% of all casualties.

By the time of the First World War,

artillery accounted for around 80% of all battlefield casualties.

By 1917, battle lines had got deeper and deeper.

Trenches now stretched back five, seven, sometimes ten miles.

EXPLOSIONS

Firing at longer ranges than ever before, firing the blind,

firing from map coordinates,

and flinging their shells up to 14,000 feet into the air,

it was essential that the gunners understood weather conditions,

atmospherics and wind speed.

This long-range form of warfare meant shells were hanging

longer in the air.

They were much more vulnerable to the temperature

and density of the atmosphere.

Meteor needed a new way of getting information from higher in the air.

Of course, what they really needed

was access to these beautiful things - biplanes.

These were the technological marvels of their age.

For most of the war, biplanes were used for military purposes,

like spotting targets for the artillery.

But there was someone doing pioneering research work

while flying over the front line.

He was an officer with the Royal Flying Corps.

He was universally known by his initials - CKM Douglas.

At first, Douglas fought as an artillery spotter in the war.

It was an extremely dangerous and difficult job.

You'd have to sit in a box in the nose of the plane,

fully exposed to the elements.

Douglas retrained as a pilot and was shot down three times...

..once by a squadron of German aces headed by Hermann Goering himself.

But incredibly, during all the fighting,

Douglas was indulging his real passion.

He was fascinated by the weather.

And he had an inspiring figure to draw upon.

Douglas read The Reverend Ley's writings from 40 years before.

He admired his work on clouds

and how you can use them to predict bad weather.

Douglas used his time in the air to conduct his own private

research, and now I'm going to try to the same thing.

I'm going to take with me

the instruments that Douglas would have had during the war years.

So I have my altimeter fixed to the cockpit here,

there's a thermometer fixed to the side there.

What Douglas did was to measure the differences in temperature

as he rose to different heights through the air, which is

exactly what I'm going to do.

Contact.

Up here, Douglas got an astonishing view of different cloud structures.

At 8,000 feet,

he said he could see the tops of cumulonimbus 100 miles away.

He was one of the first people in the world to realise

how useful airplanes would be in meteorology.

Lovely, thank you very much. It's beautiful.

As we rose through the air, I did manage to write down

the temperatures at different heights,

and even in my very unscientific survey, you can see that

the temperature, as you go up, does decrease fairly consistently.

On the ground it was 12 degrees Celsius.

By the time I got to 1,500 feet,

it was eight degrees Celsius in the air.

The reason Douglas was interested in how temperature changes with

height is because it's such an important

part of understanding how the weather changes.

And that's very closely linked to a question

we all ask ourselves around the British Isles - is it going to rain?

Douglas was investigating the fundamental physics of weather.

Warm air holds more water vapour than cold.

As the air rises, the vapour condenses to form clouds.

And if the cloud becomes too heavy, the water falls as rain.

THUNDER RUMBLES

My own reading showed that the temperature was dropping over

three degrees per 1,000 feet, which is faster than average.

It's probably because the air was quite dry.

Temperature drops faster in drier air.

Because there was less moisture, there were no clouds.

So we had a beautiful day for the flight.

After the war, Douglas became one of Britain's foremost meteorologists.

He wrote ground-breaking papers and became one of the leading

forecasters during the Second World War.

As for Meteor, it finally got its own planes to take readings.

This helped the artillery increase in accuracy

and contributed to the Allied victory.

But the question remained, how could you use all this information

to accurately forecast the weather?

The way ahead lay in physics.

It was known at the time that all the variables of weather,

wind speed, temperature, humidity

are base-specific laws of physics.

But what wasn't known was how to turn the physics into forecasts.

Professor Ian Roulstone is an expert on the terrifyingly complex

maths of weather.

So, let's write down the equations that we use in weather forecasting.

And we'll start what is eventually Newton's law of motion

for the atmosphere.

This tells us how wind speed

and direction is affected by things like that Coriolis effect,

which is due to earth's rotation.

Then, of course, gravity also plays a role.

Then we need to add the pressure gradient term,

and finally we add a term which represents friction.

And that's just for the wind.

You need an equation for air density,

one for pressure related to density and temperature.

You need the first law of thermodynamics.

And you need an equation for water vapour,

condensation and evaporation.

So here we have it, on one board,

all the equations that encapsulate the physics of the atmosphere.

But that's just a theory.

In the real world, all the variables, in all the equations,

act on each other all the time.

So, wind speed and direction responds to changes in pressure.

The changing wind blows clouds around,

so that alters the temperature distribution.

It also alters where moisture is in the atmosphere.

Changing levels of moisture,

whether it's evaporation or condensation, change temperature.

That changes pressure, that changes the wind speed and direction.

So everything is hopelessly interrelated.

How do we unscramble this Gordian knot?

There was one man who decided to take it on.

Lewis Fry Richardson was quite a remarkable mathematician.

He was born in Newcastle in 1881 to a Quaker family.

He studied mathematics at Cambridge University, getting a first,

and then had various jobs,

until he was offered a position in the Met Office.

Richardson's great-nephew remembers him

as a scientist interested in explaining everything.

Even when he poured the water out in a glass and it slightly spilled,

he then told us why the water did spill or didn't spill,

depending exactly on how the water went over.

So everything, everything was studied.

In the First World War, Richardson had a crisis of conscience.

He was working for the Met Office, but it was helping fight a war.

Because he was a pacifist, he didn't want to get involved in fighting,

nor did he want his science to be used in fighting.

So he then resigned and joined the Quakers' Friends Ambulance Unit.

Richardson had decided to help those suffering in war.

He worked on the front line,

driving an ambulance in extremely dangerous conditions.

Between shifts, lodged in a freezing cold billet, he carried out one

of the most remarkable metrological experiments ever attempted.

Richardson brought these with him to the front.

They're weather charts of northern Europe, taken on a specific time,

on a specific day and the data had been collected

by an international conference of meteorologists.

What these charts did was to give Richardson an idea

of the weather at a very specific time.

But what he wanted to do was predict the weather a few hours after this.

It wasn't a forecast as such, more of an exercise to see

if his methods worked.

Richardson had decided the only way to solve the equations

of weather was to break them down into smaller calculations,

each one looking at a part of the problem.

He began by simplifying this map

and drew a series of squares over northern Europe.

What he wanted to do was see if his mathematical equations

could predict the weather in this central area of Germany.

He then entered his data into these computing forms, all 23 of them.

And he used these to carry out even more calculations.

He calculated how winds might affect air pressure,

how air pressure might affect air density and temperature.

He took into account the curvature of the earth,

radiation from the sun and from the ground,

he even had a calculation to work out

how piles of dead leaves might move heat and moisture through the air.

Temperature in the soil, latent heat of evaporation,

character of vegetation, thermal conductivity,

accumulation of sensible heat,

the flux of sensible heat, sheer stress.

The detail in here is incredible.

The work was so complicated, it took him two years -

half the First World War - to complete it.

It's been estimated that Richardson had to solve 60,000 equations

to get to his prediction.

And he did it all by hand, on the Western Front,

in between shifts as an ambulance driver.

It was the world's first attempt at what's now

known as a numerical forecast.

And unfortunately, it was a complete failure.

THUNDER CRASHES

Now, one of his key results was that the pressure would change

over the six-hour period following the observations.

It would change by 145 millibars.

Now, this is an astronomical figure.

It's 100 times bigger than anything realistic.

THUNDER CRASHES

It's the equivalent of a hurricane the size of which has never

happened before or since appearing out of nowhere in Germany.

It seemed either his maths or his method were wrong.

But Professor Lynch decided to go over

Richardson's calculations again.

So, some years ago, I thought it would be very

interesting to replicate his work using a computer and sure enough,

after a very short period, the computer produced the number 145.

So he came up with the same result as Richardson,

proving his maths was right.

The real problem lay in the original data.

Now, Richardson didn't realise this.

His initial data was essentially corrupted by spurious noise.

So it was a matter of making small but subtle alterations

to the initial fields and when this subtle adjustment was made

and the forecast was rerun, the change in pressure

was reduced to something less than one millibar in six hours.

Which, of course, is a realistic number.

So, if Richardson had made some adjustments to his original data,

his forecast could have been much more accurate.

But there was another problem.

You could never do these calculations fast enough to predict

the weather before it happened.

But Richardson had an answer to that, too.

After the war, Richardson published this book

and in here there's an extraordinary passage about something

he dreamed up called the forecast factory.

The forecast factory was Richardson's

strange solution to the problem.

It's so colourful a concept,

it's inspired works of art in the years since.

This was painted by Stephen Conlin in 1986.

It gives us a vivid representation of what Richardson

described in his book.

You can see that Richardson described the round theatre,

something like the Albert Hall, but painted with countries all over,

to make it look like the planet earth.

Around the outside of the globe are a series of boxes filled with

people calculating equations for their part of the world

and controlling all of them in the middle of the globe

is the conductor,

and he's making sure everyone's doing their job at the right time.

On one side, you can see he's beaming some red light,

which shows that those people are making their calculations a bit

too quickly. On the other side, he's beaming some blue light,

meaning they're making their calculations a bit too slowly.

Outside the globe, there's actually people having a game of football.

Because Richardson was clear, he said that people calculating

the movement of the air should also be allowed to enjoy it.

For Richardson, this was a fantasy.

And even to us, it looks highly unrealistic.

But it was actually a glimpse into the future,

because what Richardson had dreamt up here was essentially a computer.

But the data-crunching powers of a modern computer

were still years ahead.

I'd think the significance of what Richardson did can be seen

by reflecting on what we actually do today.

We assemble the observations, we analyse them,

assimilate satellite data and so on,

but the method of solving the equations is essentially

of the same character as the method which Richardson invented.

Richardson may have been a visionary,

but it was clear that using maths was, for now, impossible.

What was needed was a workable model to forecast the weather

with some kind of confidence.

And here, in the northernmost country in Europe,

a major breakthrough would provide just such a model.

Bergen is a city on the coast of Norway.

Often battered by storms and low-pressure systems,

it's an ideal place to study the weather.

Even the local geography makes it a meteorologist's paradise.

And so, here at the west coast of Norway, in Bergen here,

we get the weather systems coming in and here

they are well-behaved in the sense that they have very distinct

structures, they have not been blurred or disturbed by

big modern changes or the heat-land-sea contrast,

so they come in here and we can monitor

or measure these features very well.

A century ago, some extraordinary work was carried out

at the Geographical Institute in Bergen.

A scientist called Wilhelm Bjorknes came here in 1917,

and once again, it was human catastrophe that drove

the next breakthrough in forecasting.

Fisheries was a quite important, and still are important,

activity and source of income in Norway.

And at that time, when Bjorknes came here,

they knew about several incidents where fishermen deceased

and the boat sank due to unexpected weather, so to speak,

so Bjorknes immediately saw that there was a need

for weather forecasts.

Bringing together all the data, they set about tackling the big question.

How do low pressure systems work?

What Bjorknes and his clever students...

They put together this information and they came up with

the pattern or the anatomy of the weather systems.

They discovered two crucial features inside a depression.

The warm front and the cold front.

The theory of weather fronts is something every meteorology student

now learns, even 100 years later.

I'm back at my old university, Imperial College London,

to take a look at today's weather map.

OK, Jo, so we have a map of north-west Europe here. There's the UK.

The Arctic's somewhere up there, so that's north, Greenland.

What else are we looking at on this map?

So, you've chosen a very interesting day to come.

You can see it looks like a real mass,

but there's features on here that you'll see in any weather map,

and particularly you'll see that high pressure's marked with a H

and you'll see the low pressure's marked with an L.

And you'll also see these features,

these lines with marks on, which are the fronts.

Perhaps I could show you a rather simpler version

on the blackboard here.

So, if I stylise the low pressure system as a circle, like this...

And here's the low in the middle here.

And associated with the low pressure,

you get these frontal systems.

And here's the cold front.

And the cold air's coming in from the north.

And here's the warm front.

And the warm air's coming in from the south.

So, this essentially is the structure that was discovered

by the Norwegian school in Bergen,

and it's associated with the cold air in the north

and the warm air in the south and it's where these two air masses

meet that you get the low pressure and the fronts.

-And this is where the weather happens, at these fronts?

-That's right.

So, over here we've got a fluid dynamics experiment

which is going to illustrate what happens in a front.

So, we're going to illustrate using water what happens in the air.

How do the things relate?

Well, of course, air is a fluid and it's flowing, and so is water.

And what we're going to do is remove the divider between the two

-and see what happens.

-OK. Let's do it.

-Cold water on the left, hot water on the right.

-That's right.

So, what we expect to see...

is the cold water flowing underneath the hot water.

So, it's just like in the frontal system.

And the clouds would be forming between those two layers.

'As the warmer air rises, it's cooling, causing clouds and rain.

'The air masses meet along a turbulent boundary,

'like two armies clashing along a front.

'That's why the Bergen School called them fronts.

'It's an echo from a generation

'still scarred by the First World War.

'The theory of fronts showed that Ley was right about cirrus

'clouds decades before.

'Different types of clouds form at different stages

'of the development of fronts.

'And we now know that cirrus clouds are usually the first

'to develop as a warm front advances.

'The theory also helps explain why Britain has such varied weather.'

The UK sits right at the place where a number of different

types of air masses meet.

There's the polar air masses coming roughly from the north,

the continental air masses from the east, the tropical air masses

from the south and the maritime air masses coming from the west.

Over the course of the British year, different types of air masses

meet with varying temperatures and humidity.

Generating the changeable weather we're all so familiar with.

So, with the Bergen School,

meteorologists finally had a way of predicting the weather in Europe

and North America and those latitudes all round the world,

which are all dominated by weather fronts.

Now, the next frontier of forecasting awaited.

In the years after the First World War, on the other

side of the world, meteorologists were facing up to another challenge.

Trying to unpick the complex, interlinked nature

of the world's climate.

Across the Indian subcontinent, flooding, drought

and other natural disasters kill more people than any war.

Even now, extreme weather events are hard to predict.

This is Professor Ram Babu Singh.

He and his students have set up a simple weather station

on top of the campus buildings at Delhi University.

Here we can gauge the temperature,

the latest humidity, rainfall

wind direction, wind velocity.

This is a very small initiative, but through this

we want to develop the culture of monitoring weather,

you know, so that this will become the mass movement in our country.

This data could help predict probably the most important

and mysterious climactic phenomenon in India - the monsoon.

As you know, India has more than one billion population,

and for feeding them, we need agricultural production.

The monsoon is very, very important for our country.

The monsoon rains are brought to India by seasonal winds.

Sometimes they fail to come

and the consequences can be catastrophic.

Continuous, for two years, failure of rainfall

will bring tremendous damage to our society

through loss, through reduction of agricultural production.

Under the British Empire,

monsoon failures caused horrific suffering.

There were fast famines with millions of deaths.

By the time of the First World War, the scientist tasked with

trying to understand why it was happening was called Gilbert Walker.

He was head of the Indian Meteorological Department

and he had some unusual interests.

He would throw boomerangs and projectiles around,

even in front of the Viceroy of India.

Sir Gilbert Walker was really interested in the dynamics

of throwing sticks, of spears, of boomerangs.

And all those sort of things, and to try and understand what were

the fundamental processes involved with aerodynamics?

Walker's fascination with dynamics made him an ideal choice

to tackle one of the most complicated

scientific conundrums of the age.

Planetary dynamics - how does the climate work on a global scale?

During the First World War he was left with the Indian

clerks in his department, a mass of people.

And because there was all this information, predecessors,

he had been looking to try and forecast the monsoon.

What he did was to pull all this information,

all the hydrological and meteorological data

that he had round the world,

and basically to create a human computer,

getting his clerks to work together in mass to do correlations

of all sorts between these variables.

They made some extremely significant breakthroughs.

What he basically found with these Indian clerks

was that there was a pressure fluctuation,

which you called an oscillation, between the Indo-Australasian region

and in the southeastern Pacific region of the globe.

So, when the pressure is high over the Pacific,

it's low over India and vice versa.

The seesaw in pressure is one of the elements in the dynamics

of the climate system over the globe -

its linkages to monsoonal systems like in India.

It's not one-to-one in India but it certainly has an impact.

And so the whole system of the rainfall is related to

the fluctuation in pressure that Walker discovered.

Walker's efforts added another piece to the picture

of our understanding of global dynamics,

and I think he's a person that we really need to really give

high praise to, for his efforts on understanding the climate system.

In the 1920s and 1930s, meteorologists were beginning

to realise the global, interlinked nature of our climate.

But their understanding of our hugely complex atmosphere

was still limited.

Again, it would take a world war to provide more investment,

more challenges and more breakthroughs.

It would also provide meteorologists with their toughest test yet.

When the war broke out in 1939, the Met Office was once more mobilised.

They set up a top-secret camp outside London in Dunstable.

They faced an extremely difficult task,

gathering data in wartime conditions

with the technology available at the time.

The Met Office had thermometers,

had barometers.

They may have had a weather vane, a wind speed indicator

and a device for measuring humidity.

And then they would look out the window

and see what it was doing and they also had...

..the wet finger.

As the war progressed,

a sophisticated system for gathering data was developed.

This included weather ships taking readings out at sea.

And they also had men aboard weather reconnaissance flights.

Long, lonely flights over the north Atlantic.

That gave them a pretty accurate picture

of what was actually happening.

Colin Mentz is one of the few Met Air Observers still alive.

As a teenager, he flew on hundreds of reconnaissance flights

with the RAF, and later in American B-17s.

These are some of the chaps with me.

That's me. Tallest of the lot.

I think the longest flight I ever did was about 16 and a half hours.

I used to enjoy it.

All the time you were keen on looking

out of the window at the weather.

Because you had to make notes

and code the stuff up

to send back, otherwise your flight was wasted.

This is a Met Office weather chart from 1944.

It shows readings which Colin sent back during a flight

from Cornwall out into the Atlantic.

His data was highly important as he was one of the few observers

Dunstable had out to the west.

But it was dangerous work.

23 Met Air Observers were killed during World War II.

PLANE ENGINE ROARS

The most dangerous part was flying at 10, 20, 30 feet above the sea.

It's sometimes very rough.

So, were you ever frightened?

No. Not that I can think of.

Eh...

I thought sometimes that, "I wonder if we'll get back all right."

The Allied forecasting system got many predictions right

and saved lives.

But they still didn't really understand some crucial parts

of the higher atmosphere, and when they got things wrong,

the consequences could be dire.

In the winter of 1943,

Bomber Command launched a series of raids on Berlin.

On the night of 24 March 1944,

a huge fleet of 811 aircraft set off for Berlin.

The original idea was to fly the planes over Denmark

and the Baltic Sea, drop the bombs on Berlin

and then come back as quickly as possible,

avoiding the Ruhr industrial area, which was heavily defended.

Predicting upper air speeds for a bombing run like this was

one of the toughest tasks for forecasters.

That night, the prediction was for winds of around 45mph.

The first wave of bombers took wind finders,

weather observers who sent back reports.

By the time the fleet reached Denmark,

the wind finders were reporting extraordinary winds

coming from the North, air currents up to 130mph.

This was far, far more than expected.

In fact, we now know the planes were encountering jet stream winds.

These are the very same winds which William Clement Ley

had discovered 50 years before.

But still, meteorology hadn't properly understood the phenomenon.

That night, the results were catastrophic.

Even before the Allied planes got to Berlin, they were scattered,

off-target and in disarray.

Then, when they turned westwards to head back to Britain,

the German night fighters were lying in wait.

The Allies were sitting ducks.

72 bombers were destroyed.

Over 500 men were lost.

That night was known for ever afterwards by the RAF

as "the night of the big winds".

This disastrous night was a stern warning for weather forecasters

who had to accept their limitations as well as their successes.

And coming up was the most important forecast of all.

D-Day.

Throughout 1944, the Allies were assembling a colossal

invasion force around the coast of Britain.

11,000 aircraft.

6,000 sea vessels.

150,000 soldiers.

Their target?

The beaches of Normandy,

100 miles in that direction.

As overall military leader,

Eisenhower needed an accurate forecast

for the day he was to invade.

But the Allies had developed a complicated forecasting structure

with three centres.

The admiralty had its forecasters.

There was the Met Office at Dunstable.

And the American Air Force had its forecasters, too.

The forecasters in Dunstable made their predictions

based on the theory of fronts, as pioneered by the Bergen School.

The US Air Force, though, had different ideas

under its chief, Irving P. Krick.

Irving Krick was in the weather business to make money.

And he used his position in the US Air Force

for self-promotion.

He was bombastic...

he was absolutely convinced that he was right.

His reputation among other American meteorologists...

He is considered a charlatan.

Krick advocated a highly unusual method to predict the weather.

Analog theory is the idea that a weather map from history...

is the key to understanding the weather of tomorrow...

because it's based on the notion

that weather repeats itself in cycles.

And it does not.

Irving Krick believed that he could forecast the weather almost anywhere

in the world for a month in advance, because of his analog system.

With different forecasting centres using different methods,

one man was given the job of melding the forecasts into a single report.

A Scotsman called Group Captain James Stagg.

Stagg was an interesting character.

On the outside, his shell was as hard as a conker shell.

On the inside, he was filled with self-doubt.

Would he get it right?

The Allies only had a few dates on which it was possible for them

to invade. They needed the moon and the tides to be perfect.

The first date they set was June 5th.

As the date neared,

Stagg was under extreme pressure to get his forecast right.

One general even said to him that if he got the forecast wrong,

he'd be strung up from the nearest lamppost.

This is a weather map created using original data

from those crucial few days.

It shows the situation at the end of May.

What you can see is that Britain generally has good weather

because of a high-pressure system.

But look out to the west

and you can see some low-pressure systems developing.

They're the counterclockwise winds.

This highly complicated weather map divided the scientists.

The Dunstable forecasters were very worried about the lows.

But Irving Krick was confidently predicting

that the weather would be good enough to invade.

So it was that over those few days,

a tiny weather station on the west coast of Ireland became

the most important meteorological centre in the entire world.

Blacksod Point is a remote spot overlooking the Atlantic.

Vincent Sweeney keeps the lighthouse,

just like his father, Ted, before him.

My dad lived here and he was in the lighthouse,

he was the attendant at the lighthouse here in Blacksod

before he retired in 1981. And then I took over.

The lighthouse is situated in a vital area

for collecting weather data.

It's a strategic location into the North Atlantic.

It's poised right on the tip and any weather systems that come over,

they hit us first.

Blacksod's position made it a very important source

of data for Dunstable,

who had an information-sharing arrangement with the Irish Met.

Just down the road was where the data was collected.

This house here was where the weather station was.

In the garden of the house, as you can see,

where the daffodils are, there, there was some weather instruments,

so this is where all the readings came.

Vincent's dad has passed away.

But his mum Maureen is still alive.

She's 92 years old and still lives at Blacksod Point.

'What was it like during the war around here?'

It was quite enough, you know.

We had plenty of planes overhead, you know?

But the thing is, we didn't know whether

-they were British or German!

-SHE LAUGHS

It was a bit frightening, yeah.

Especially at night.

D-Day was approaching.

And the family were asked to take readings every hour.

On the hour, every hour, night and day, Sunday and Monday.

We were told that all reports were the first to show any change

coming in for good weather or bad weather.

On the crucial night, the 3rd of June,

it was Maureen's turn to get up in the middle of the night.

She measured 4-6 winds and a rapidly dropping barometer.

A sign of approaching bad weather.

The figures alarmed Dunstable and they rang Maureen back.

We took the weather in the ordinary way and passed it on.

I wasn't told anything until we got it back again, saying,

"Please check and repeat."

I went back again and I checked.

But it was right.

It HAD dropped.

This is the situation on the morning of June the 3rd.

There's Blacksod Bay on the west coast of Ireland,

where the air pressure is dropping and the winds are on the rise.

As the day progresses, the low gets deeper, the winds get faster

and the low-pressure weather system starts to move

north-east across the Irish coast.

At 4am on the 4th of June, with less than a day to go,

Stagg headed into Eisenhower's office.

He walked into the room full of generals

and told them that the conditions in the Channel would be too choppy,

too much cloud, too many high waves.

The invasion had to be called off.

The future of the war hung on what Eisenhower did next.

You know, the weather outside was reasonably good.

So everybody was a little perplexed by that.

But Eisenhower had taken measure of Stagg

and he knew that he could rely on Stagg

to give him completely unbiased information.

Eisenhower agreed and postponed for a day.

Some of the ships had already set sail and had to return to port.

Stagg was dismayed for much of that day as the weather stayed calm.

But that afternoon, the wind picked up

and the bad weather that he'd predicted swept in.

If the invasion had been held on the night of 4-5 June,

as it was planned, it would have failed.

The results would have been catastrophic

for our own history.

The next day, the weather improved and the invasion was launched.

It was a success.

The Allies gained a crucial foothold in German-occupied France.

To think that so much hinged on a single weather forecast.

GUNFIRE

The D-Day forecast was a triumph.

It showed that the theory of fronts could be used to predict

the weather, at least for the short term.

It was also a success for those meteorologists who understood

that their science had limits.

The Met Office camp at Dunstable is long gone.

On the site now is a school.

Staff and children here have set up a monument and a weather station.

71 members of the Met Office died in World War II

while on active service.

As for Colin Mentz, he flew on D-Day itself.

I can remember travelling over southern England,

saw all the aircraft lined up on the airfields,

and when we came back the next morning,

the airfields were empty.

They'd all gone.

We got the message saying that the invasion of France had taken place.

I turned to the skipper and said,

"Do you want to go over and have a look, Skip?"

-LAUGHING:

-He didn't.

Ted Sweeney now lies buried overlooking the Atlantic,

where the D-Day depression first blew in.

And Maureen is still contacted by veterans

who've thanked her for getting her readings correct.

Recently I was reading a piece in an English paper and had Eisenhower

declared war that night or gone to war, it would have smashed America.

-It said that. I should've kept that paper.

-'Yeah.'

'So it was your weather report, your barometer reading...'

Yeah, from Blacksod,

above all places!

-SHE LAUGHS

-That ended the war!

In the next episode:

Richardson's dream becomes a reality

in the face of some of weather's greatest challenges.

Forecasting becomes a global enterprise,

built on high technology.