So it was, with such basic equipment, not even capable of automatic multiplication, that the Met Office began to fulfil the dream of L.F. Richardson, when in 1922 he suggested the possibility of numerical weather prediction using a grand 'forecast factory' - consisting of thousands of (human) computers, seated around a globe-shaped auditorium, each one calculating the future state of the atmosphere at a fixed location by evaluating a set of equations.

In the ten years following the purchase of the electrical desk-calculator, a small number of Met Office staff had access to a 'real' computer - the LEO 1 - which had been built by Lyons, the caterers. Eventually, in 1959 the Met Office purchased its first computer - a Ferranti Mercury, which the office named Meteor. With glowing valves and copious volumes of paper tape, the Met Office had entered the computer age.

Through the decades following the arrival of Meteor, the Met Office has regularly upgraded and replaced its computers, to take advantage of the speed and functionality provided by new technology. During this time, the size and complexity of the meteorological models and their associated data have also increased dramatically, reflecting the steady increase in computational power and memory sizes. The table below shows the increase in computational power of the Met Office's computers over the last 35 years, and how the meteorological models have also increased in both horizontal and vertical resolution during this period.

Between 1997 and 2004, the Met Office used two Cray T3E supercomputers. The T3E was a radical departure to what had been used previously. Instead of having a single processor like the IBM 360/195 or just several like the Cray Y-MP, it was capable of having several hundred processors. This type of computer is known as MPP or Massively Parallel Processor. The T3E used commodity ('off-the-shelf') processors rather than specifically designed ones like the C90 did and thus despite containing many more processors than the C90, it was not proportionally more expensive.

In 2004, following successful relocation to its new headquarters building in Exeter, the Met Office changed computers again. Initially the operational forecast was run on a NEC SX-6 supercomputer but was transferred to a more powerful NEC SX-8 supercomputer in April 2005. The SX-6 still remains key to the Met Office's capabilities; in addition to acting as a back-up machine, the SX-6 will be used for research and development.

The SX-6 and SX-8 differ to the T3E in that they have fewer, but much more powerful processors. The SX-6 and SX-8 machines are divided into 'nodes' with each node containing eight processors. Currently the SX-8 has 16 nodes, and there are two SX-6 clusters; one with 19 nodes, and the other with 15 nodes. Each SX-8 node is twice as powerful as an SX-6 node, so together, the combined systems deliver over thirteen times the sustained power of the previous Cray T3E computers, which the SX-6 replaced in 2004.

Weather forecasts will benefit from the extra power, which will mean increased accuracy and detail in the models run by the supercomputer. These models will provide improved forecasts of high-impact weather, building on data available from a new generation of satellites. Climate change predictions will become even more authoritative through increases in resolution; representation of new processes and the use of ensemble predictions to provide risk assessments.