...about the Weather James May's Things You Need to Know

...about the Weather

James May asks the big questions about the weather, like why is the sky blue? What is a cloud? And how can you avoid being hit by lightning?

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Here is the forecast for the next 30 minutes. It will be an


unpredictable start, giving way to clear blue skies. Later it there


will be wind with rain and the occasional flash of lightning.


There is also the distinct possibility of a hurricane so


please stay tuned for further updates. And if you do decide to


head out, here is the important things you need to know about the


weather. First up, why it is the weather so


unpredictable? We have probably all been victims of bad weather


forecasts at some point. Believe it or not, you need a degree to be a


meteorologist. In their defence, the planet's weather is in chaos.


It is what scientists call a chaotic dynamics system. Dynamic


because it changes all the time, and chaotic because it doesn't


follow any set pattern. That is because the Alf has massive


mountains, huge oceans and a thick atmosphere -- the earth. It is


being constantly bombarded by heat from the Sun. This combination of


limitless energy and lopsided landscapes provide -- produces


large and violent weather systems, and they bump into each other as


they stomp around the planet. This complexity makes the weather in the


earth the least predictable in the phone system, but it has not


stopped us from trying. In olden times, we relied on guesswork and


folklore, like interpreting animal behaviour. Or entrails. But the


only vaguely accurate method was observation. During the Renaissance,


we invented machines like a barometer, which measures


variations in air pressure. This helped us with short-term weather


changes. Then Samuel Morse patented the electromagnetic Telegraph,


which meant we could find out what the weather was like elsewhere, but


that was still no guarantee that this weather was on its way to us.


We were still stuck in observation mode. A major breakthrough came in


1922, when a scientist, Lewis Richardson, developed a


mathematical model for forecasting future weather, using information


gained from observations of conditions around the world. This


was great, except it would have needed 64,000 people working flat


out to keep the forecast up-to-date. Luckily, we then invented computers


that did the math for us and the idea took off. But even with all


today's modern forecasting technology, meteorologists still


struggle to stay on top of the chaos of the world's weather, which


is why they can still be wrong about tomorrow. So now you know why


forecasters make bad predictions. Not that we should best as they


really give them a break about it. It does seem that all you need to


do is press this button and the weather changes, and all anybody


wants his sunny days and clear skies. Except they are not really


clear. They are blue. Why is the sky-blue? This would be a strong


contender for signs's dirtiest trick question because really, it


isn't blue. It isn't any colour at all. It all comes down to how the


human brain interprets visible electromagnetic radiation. Also


known as sunlight. Although sunlight appears as white, it is


actually a mixture of all the magical colours of the rainbow.


Isaac Newton demonstrated this when he used a prism to separate them


out, a nifty little party trick known as refraction. These colours


form the visible range of what is called the electromagnetic spectrum.


It includes super hero powers, like the Marais and X-rays, and the less


sexy microwaves and radio waves. Like waves on the spectrum of so


small they are measured in nanometres, and each colour have


its own individual wave length and frequency. But in space, they


combine to produce white lights and they all travel at the same speed.


The speed of light. The action doesn't really begin until the


light reaches the Earth and crashes headlong into the oxygen and


nitrogen molecules that make up 99% of our atmosphere. It is then that


the colours started separate, with some getting knocked about more


than others. An effect known as Rayleigh scattering. The shorter


the colour's wavelength, the more it gets bounced around and the blue


light is that the shorter end of the spectrum. This means that when


it hits the atmosphere, the air molecules scatter the blue light


everywhere, while other colours pass straight through with barely a


scratch. So the colour blue appears to be coming from all over the sky


as it makes its way to your eyes. But here is why it is a trick


question. This guy isn't really blue, we just think it is. -- the


sky isn't really blue. The are his only pick up the wavelength and


send that signal to be a brain. The brain and then decides what colour


that wavelength should be, while painting a picture in real time. It


is the original blue-sky thinking. This guy isn't the only vast


expanse that appears to us to be blue -- the sky. The oceans do for


the same reasons. They scatter at the Blue Light while absorbing the


other colours and that is probably why the Earth is referred to as the


Blue Planet. There are 1.3 billion cubic kilometres of water out there


and that begs the question: How do oceans affect the weather? Water,


water, everywhere and not a drop to drink. Unless, of course, you are


one of these. Oceans cover 71% of the Earth's surface and contain 90


tempers cent of its water. So it is not surprising that the ocean has a


big say in the world's weather. Their most important role is in


storing and distributing heat. In fact, over half of the heat we get


from the sun is stored in them. Most of its days near the surface


in the first few metres of what is called the epic pelagic zone. Ocean


temperatures can reach up to 36 degrees Celsius and this warm-water


it swims around in surface currents, created by passing winds. Other


currents move about in water as Col des minus two, and this change


helps to keep worldwide temperatures in balance -- as cold


as minus two. The most well-known is the Gulf Stream. It starts out


in the Gulf of Mexico and passes the tip of Florida, where it begins


a 2500 kilometres migration across the Atlantic. Amazingly it shifts


over 100 times more water than all the rivers on earth. Ocean's also


supply around 90% of the water used to create rain. They are hugely


effective at absorbing carbon dioxide, which manages the Earth's


climate. They are also home to more slippery things, like hurricane.


But perhaps the most slippery of phenomenon is a mean you have. It


is a complex phenomenon in the earth's climate -- L Lemieux. It


appears every three-- El Nino. Its arrival causes a number of strange


things to happen, including a dramatic increase in rainfall in


South America, while at the same time droughts in Australia, and


these extremes caused upset to everyone. We still don't completely


understand what causes El Nino but did implement on the weather is


second only to the changing of the seasons. And we are never really


totally sure when it will return. So you can think of the oceans


might joined factories where a lot of the weather is manufactured --


like joint factories. But it would not get anywhere without another


vital component, the wind. Sometimes it is a gentle breeze,


sometimes it is strong enough to blow you over, but how does that


come out of thin air? Why does the wind blow? The wind is guaranteed


to get you on the moves. The key is the Sun, which produces 386 billion


billion megawatts of power every second. Some of this energy gets


transferred onto the Earth's atmosphere. The equator receives


the most direct sunlight while the North Pole and the South Pole have


to make do with whatever they can get. To redress the imbalance, the


warm air at the equator rises and heads off to the North Pole and the


South Pole. Once there, it gets colder then goes back to the


rises because the molecules get excited and begin to jump about so


that the air expands. Colder temperatures, the molecules down,


so the air contracts, becomes more dense and fought back to earth.


These motions create regions of high and low air pressure and the


air will always flow from where the pressure is high to where it is low.


This results in wind. Added to that is friction, caused by the planets


dips and bums. This helped to decide when speed and direction.


Then at the Coriolis effect comes into the mix. As the Earth rotates,


it sends the moving air into a spin, throwing it to the right in the


northern hemisphere and to the left down under, leading to weather


systems that rotate in opposite directions. But wind is not simply


a global phenomenon. It also happens on a much smaller scale.


With different surfaces, such as forests, mountains, deserts, Oceans,


all been heated unevenly, it creates localised wind patterns.


What you end up with are those funny circles on a weather map that


look as though they have been drawn by a two-year-old. They represent


regions of high pressure and low pressure, with the Arrows telling


you which way things are going. The wind comes recommended by


Christopher Columbus, geese and the Netherlands. But please remember to


treat it with caution. As it can, in some cases, lead to extreme


devastation. The wind is a fundamental part of Mother Nature's


game plan for the weather, but occasionally she throws in a couple


of other players as well, and almost, their least favourite


opponent is the rain. Love it or loathe it, it is an essential part


of the weather. The next question is: Where does all of the rain come


from? Rain, rain, go away, come again another day. You might


remember that one from your childhood. It is actually a good


summary of the hydrological cycle. The never-ending journey mortar mix


between the Earth and the atmosphere. -- water makes. It


begins with water vapour, which is water in gas form that has been


sweating of the planet's surface by heat from the sun. As it rises, the


Weber calls off, ready to condense back into a liquid -- the vapour


calls down. It uses condensation nuclei, the microscopic stuff that


gets coughed up by dust storms, volcanoes, fire and pollution. The


vapour condenses into these particles, forming water droplets


or, if it has travelled where the temperature was below freezing, ice


crystals. This process is repeated until then number in the trillions,


forming what scientists call clouds. To fall as rain, the droplets have


to be heavy enough to succumb to gravity and large enough to power


through the rising warm air beneath a cloud. To do this, the droplets


joined forces to create raindrops, which can be up to one centimetre


in diameter. Some parts of the world are more prone to heavy rain


and others because of the different way the climates work. India is


famous for its monsoon season. There would monsoon actually


referred to seasonal changes in wind direction -- the word monsoon.


During in the year's summer, warm, wet air is drawn in from the ocean,


In winter, the wind changes direction and blows the rain away.


Although, like the Rhine says, it will come again another day. The


high score for the most rain in 24 hours is held by a tiny island off


the east coast of Madagascar. It was swamped by 73 inches in 1952.


That is going to be tough to beat. Precipitation can come in other


varieties besides rain. My least favourite example of this is snow.


It always makes me think of my grandmother, who used to look out


of the window and say things like "it is trying to snow but it is


just too cold". I wonder if she was ever write about that. Can it be


too cold to snow? Snow might look soft but don't be fooled, it can


close down schools, roads, and even airport. It is hardly likely to let


the drop in temperature get in the way. It can see no no matter how


cold it is, but there is more to it than that. Just like rain, snow


needs water vapour to rise up from the ground, which then freezes into


snow crystals. However, the further the air temperature falls below


zero, the less water vapour there is floating about. So any crystals


that do fall will lack the moisture they need to get bigger. This makes


it harder for snow to fall, but not impossible. It has been seen


falling below minus 40 degrees Celsius. At these temperatures


there is less of it about and the crystals are much smaller. Another


commonly asked questions about snow is weather or not any two


snowflakes can be identical. Let's find out. Snowflakes definitely


seem to think they are too cool for school because they do look


different when viewed close-up. The random way in which they fall as


they fall through the atmosphere means there are more potential


shapes than atoms in the universe, so the likelihood of two snowflakes


being exactly alike is bordering on impossible. Apparently scientists


came close in 1988 with two that were very much alike, but that is


not the same as identical. Of course snow is not the only Ic


thing falling from the sky, there is also sleet and hail. When hill


is earthbound, you had better watch out, otherwise you might end up


losing some of your teeth. The largest hailstone on record that


landed in Bangladesh in 1986 weighed over one kilo. Of course it


did not travel alone. Incredibly, cold as it is, hill has been


identified as a major contributor to the creation of lightning. Which


is right off the other end of the temperature scale and more


difficult to sidestep. Maybe I can give you a few pointers. How do I


avoid being hit by lightning? Lightning flashes up to 100 times a


second worldwide. You would think this would be enough for us to


understand it properly, but it isn't. We can't predict when or


were lightning will strike. We know Ben Franklin was very lucky with


his kite experiment because lightning has up to 1 billion


vaults of static electricity. It mainly appears during thunderstorms,


which are named after the sound of a lightning strike. The big issue


is that we don't fully understand how lightning forms. One of the


leading theories is that in a storm tiny ice crystals and lumps of


hailstones are crashing against each other. This causes electrons


on some of the ice crystals to break off and attach themselves to


some of the heavier falling hailstones. Then the hailstones


become negatively charged. We know the electricity is divided into


positive and negative charge. It was Benjamin Franklin who


introduced this idea. The negative charge starts to collect in the


base of the storm cloud. The ground below contains negative and


positive charge, but the negative charges are repulsed by the


negativity in the cloud base, leaving the positive charges or


loan. Just like in a bad romantic comedy, opposite always attract.


Eventually, this attraction becomes overwhelming and all the pent-up


energy is released with a bold five times hotter than the sum.


Lightning comes in several additions, including four Oct,


streaked, rocket, and the very rare ball. Not all lightning strikes the


ground, in fact most of the time it just fires around inside the storm


cloud. It you see this happening, count the seconds from when you see


lightning to when you hear thunder, and then divide that number by five.


This will tell you how many miles away the storm is. If you get


caught out, Steer clear of any metal. Water it is also a good


conductor of electricity, so avoid that. Try to get indoors if you can


but don't use the telephone to let people know you are OK. That is


wind, rain, snow and lightning taking care of. It is getting


lively but I can't help thinking that we have not yet hit on the


real big movers and shakers, like Hurricanes for example. They are in


a class of their own when it comes to big weather. When is a hurricane


not a hurricane? They are dry rating mega machines with a minimum


speed of 119 kilometres per hour. Really, they are just very big


storms. And they are not the only storms that operate like this,


there are also typhoons and tropical cyclones. Want to know the


difference? There is not one, at least not from a meteorological


perspective. To develop, all three need the water temperature to be


26.6 degrees and they all have the distinctive look to them known as


closed wind circulation. Simply put, they have been given different


names according to where in the world they form. They are called


hurricanes in the North Atlantic and the north-east Pacific.


Typhoons occur in the north-west Pacific, and cyclones fall in the


south-west Pacific and the Indian Ocean. Even though they have been


given different names, they function in the same way. It begins


with what experts call tropical disturbances in the atmosphere.


Warm, wet air rises into the sky and cools rapidly creating


thunderstorms. The Coriolis effect, caused by the Earth's rotation,


blends these storms together, spinning them around together. This


becomes the eye of the storm where it is actually pretty calm. These


storm systems can only get upgraded when their wind reaches that magic


119 kilometres per hour mark. But although they are not really


different, they are all record- holders in their own right with a


top wind speed of 408 kilometres per hour. Tropical cyclone of


Bolivia, which struck Australia in 1996, was the fastest. Typhoon tip


was the largest, but hurricane Catrina, which hit the US in 2005,


caused the most damaged - $81 billion. So a hurricane is not a


hurricane when it is a typhoon or cyclone. It is all a roller-coaster


ride but it is not amusing. Things don't come much bigger than a


tropical cyclone, but there are smaller forces at work, subtle


forces all around you that you didn't even know existed. They are


called micro-climates. Try to imagine the important stuff that


can affect the weather, like wind, temperature, a humidity and


rainfall. Then imagine cramming it into a small box. You are just


about ready to build your very own micro-climate. Essentially, micro-


climates are small areas where the climate is different from the one


outside it. These differences are caused by the lay of the land in


your plot and the way it influences the weather's behaviour. For


example, if your plot has sandy coloured soil, it will bounce more


heat back into the atmosphere than darker soil, which absorbs it. This


will affect how hot it is. Trees can provide shade in the summer,


which keeps the plot cool, but deciduous trees lose their leaves


in the winter so the sun shines through which warms it up. Trees


their leaves, making the air more moist. If your plot has a mountain


near it, this will affect the way the wind blows through it and will


force moist air to rise, creating rain clouds. You also need to think


about what latitude you want to be on, and how far above sea level


because for every 1000 metres you go up, the temperature can drop by


10 degrees Celsius. These features have created countless natural my -


- micro-climate around the world. Cities can be several degrees


warmer than rural areas. The pioneering amateur meteorologist


Haward was the first to document this in 1818. He described London


as having an artificial excess of heat, one of its many excesses that


continues today, although scientists now refer to the place


as an urban heat island. You can even change the micro-climate in


your own garden, depending on what plants you have got, what the soil


is like, the direction it faces and so on. Your DIY contribution to


micro climate change. The weather works in time as well as space, and


some aspects of it are as regular as clockwork. Four of them at any


rate, these are the seasons. Why do we have seasons? Up close, the


Earth looks like a well-built machine, but take a step back and


you will realise it has a few flaws. For starters, it has a wonky


vertical axis, off by about 23.5 degrees so that North Pole does not


point straight up. This tool was first measured accurately over 2000


years ago by this Greek mathematician, a very smart man. It


always tilts in the same direction, pointing towards the North Star, no


matter where it is on its journey around the sun. And, depending on


where you live, the tilt affect how much sunlight you get during


different times of the year. This results in the four very different


seasons. Spring, summer, autumn, and winter. The people in the


northern hemisphere get more attention during their summer


months when the Earth's tilt is in their favour. But they get the cold


shoulder in winter, when the Earth is tilting away and the sun is


shining on everyone below the equator. Although seasonal weather


changes gradually, there are days when the polls of the Earth are


tilted as near to or as far from the sun as is possible, and we call


these the solstices. The summer solstice is the longest day of the


year, and the winter solstice is the shortest. You will know when


they are because you will see people dancing at World Heritage


sites on the news. Not everywhere has four different seasons. If you


live near the equator, you only get wet and dry seasons because you get


a lot of sunlight nearly all the time. The polls only have summer


and winter, but that does not seem to bother anyone who lives there.


But they will be concerned by the fact that they are melting and the


long-term forecast is for global warming. That will change things in


Do you ever look up at the sky and wonder why it's blue? Or what a cloud is? Or how you can avoid being hit by lightning? In this programme James May asks the big questions about the weather.

To find the answers he is swept up in a storm of exciting, entertaining and sometimes downright bizarre motion graphics. The answers he comes out with are packed with facts that will surprise, amaze and entertain.

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