A 140-ton supercomputer that can perform more than 16,000 trillion calculations per second is set to give the UK its most accurate weather forecasts ever.

The £97m machine will be fired up at the Met Office next year and will crunch data at a blistering rate using the memory equivalent to 120,000 top-end smartphones.

It will be 13 times more powerful than the current system, making it one of the world’s fastest high performance computers (HPCs).

Met Office’s chief executive Rob Varley said the machine would be a “step change”, allowing hourly updates and highly detailed forecasts for areas as small as 300m.

For example, it will allow airports to pinpoint the timing and extent of fog disruption far more effectively.

The Cray XC40 system will weigh the same as 11 double decker buses and is expected to be split between Met Office Headquarters in Exeter and a new purpose-built building at the city’s Science Park.

Some £2bn of benefits are expected, according to forecasters, because it will allow the public and businesses to better plan for extreme weather, such as this year’s floods in the south of England.

“The new supercomputer, together with improved observations, science and modelling, will deliver better forecasts and advice to support UK business, the public and government, ” said Mr Varley.

“It will help to make the UK more resilient to high impact weather and other environmental risks.”

Sky News weather presenter Isobel Lang said: “The higher resolution will make it easier to map our orography and topography, but we still need the data coverage to match these improvements. It is an excellent step in the right  direction, though, towards the perfect forecast.

“There will be great research benefits especially regarding climate change and forecasting severe weather.

“It is exciting – all we need now is for it to make the weather we want.”

The boss of supercomputer company Cray, Peter Ungaro, said he was “truly honoured” to get the contract – the biggest international deal in its history.

The first phase of the system will be operational in September 2015 and it will reach full capacity in 2017.