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

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