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Our most changeable weather . . .

In some parts of the tropics and Australia, weather forecasting is a doddle. TV weathermen have to come up with different ways of saying: "It's going to be dry and sunny, with temperatures of 30 degrees for the next four weeks."

But the weather in those places is stable and predictable. Ireland, because of its latitude and the fact that it's beside a huge ocean, has some of the world's most changeable weather.

The action of jet streams -- narrow ribbons of fast-flowing air that move at altitudes of 35,000ft -- are notoriously hard to predict. "They don't flow in straight lines," says Helen Chivers of the UK's Met Office. "They can often coil like snakes -- and that is what happened at the beginning of the year."

The jet streams hovered and circled over Ireland and the UK, trapping an area of high pressure over us, and giving us the sunny and warm spring.

Then they straightened out and brought cloudy and rainy weather across the Atlantic, giving us a mainly cold, dull and dry summer, but dumping huge amounts of rain on Britain.

"Every summer, every year, we get different weather and we always want to know what factors were responsible. But you have to accept that we're in the centre of a very variable system," says Alan Thorpe, director of the European Centre for Medium-Range Weather Forecasts.

Mark Twain summed it up nicely: "Climate is what we expect; weather is what we get."

Indo Review