The new system should be fully up and running by August
One of the most powerful computers to predict the weather in the UK is being tested in Devon.
The giant IBM machine fills two special halls, said to be about the size of two football pitches, at the Met Office headquarters in Exeter.
By 2011, the computer should have a peak performance of about one PetaFlop - equivalent to more than 100,000 PCs.
It is 30 times more powerful than what is currently in place and will give more accurate and detailed forecasts.
The Met Office "supercomputer" will offer 15 million megabytes of memory and requires 1.2 megawatts of energy to run.
The system, which is expected to be fully up and running by August, will also be used for research on climate change and its impacts on society and the economy.
Met Office chief executive John Hirst said the new computer was an important step.
"In a world where the effect of extreme weather events is becoming more severe and the potential impact of global warming is becoming ever more apparent, the Met Office plays an increasingly vital role in researching and forecasting these events," he said.