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
all manner of ways. In fact the weight of professional opinion says
it's already happening. But let us stick with what I've told you for now
and maybe lets reconvene in a couple of years for a re-cap.