Frozen ducks’ feet and the flight paths of midges: the uses of forecasts by the Met Office over the 160 years that it has quietly underpinned the fabric of the nation are many and varied. They played a crucial role in D-day and still serve our military today; they keep planes in the sky and space missions on course. Should a mountain ever fall off the side of the Canary Islands, they will warn us of a tsunami. As unlikely an event as the latter should prove, be assured the Met Office has our backs.

In March, however, this long-established British institution will part company with another. After 95 years, the BBC will drop the national weather service in favour of an international private forecasting company, MeteoGroup, a move that the broadcaster says will save it millions of pounds.



In the huge glass and steel Met Office HQ in Exeter, staff are mystified and disappointed. The oldest national meteorological service in the world may be lauded around the globe but the decision – attacked as “madness” by the Exeter MP Ben Bradshaw – has dented collective pride.



The Met Office building in Exeter, Devon. Photograph: Jim Wileman/The Guardian

Ironically, MeteoGroup’s service will be based, partly, on Met Office data. And the Met Office does big data. If the number of grains of sand on Earth’s beaches is, according to one estimate, 7.5 x 1018 – or seven quintillion, five hundred quadrillion – then by 2020 there will be one bit of weather and climate research stored on the Met Office’s new supercomputer for each grain, or 1.2 exabytes of it, according to David Underwood, the Met Office’s deputy director of high-performance computers.

This massive number cruncher, laid out across three IT halls, ingests 215bn data observations every day, from outer space and the ocean’s depths and the atmosphere in between. Data is crunched, extracted, fed into simulations and regurgitated as 4m individual forecast products for customers every 24 hours.



It is a far cry from the first newspaper weather forecast, in 1861. The first BBC radio forecast was in 1922 and BBC TV forecasts began in 1954, 100 years after the UK’s national weather service was set up by Vice-Admiral Robert FitzRoy, erstwhile captain of HMS Beagle, of Charles Darwin fame.

Naval officer Robert FitzRoy. Photograph: Hulton Archive/Getty Images

FitzRoy’s priority was the safety of sailors and fishermen. A force 12 hurricane in 1859, causing the loss of 459 lives off Anglesey on the passenger steam clipper Royal Charter, led to his first gale warnings charts. He called it “forecasting the weather”, coining the term “weather forecast”, and drew data from 15 land stations that sent daily reports through the new telegraph system.



Today the Met Office draws data from 4,500 observational sources, including 16 operational radar and 330 monitoring stations in the UK, plus 19 satellites, and from other national meteorological services around the world.



“Mercury, Mars and Venus. Putting our people into military uniforms and sending them into war zones. Keeping two-thirds of the world’s airlines in the sky. Foot and mouth disease. Blue tongue. Cold ducks’ feet,” explains the chief executive, Rob Varley, 53, when asked what the Met Office remit covers.



The temperature of ducks’ feet apparently relates to alerts to suspend wildfowl shooting when it’s too cold for birds to fly. Foot and mouth is airborne. Blue tongue cattle disease is transmitted by midges. “So we predict the flight of midges, which is largely to do with wind direction, of course, and any other airborne hazards, nuclear and biological.”



The roll-call of planets pertains to its role in providing routine forecasts for the European Space Agency. “We used to pride ourselves on being the best weather and climate service in the world. Now we think of ourselves as the best in the galaxy,” says Varley, pointing out that for decades the Met Office has been consistently voted No 1 out of all the national weather services in the world.



Presenter Aidan McGivern in the Met Office studio Photograph: Jim Wileman/The Guardian

Not good enough, it seems, for the BBC. “Obviously we were disappointed,” Varley says. The Met Office’s bespoke BBC service included data, meteorologist forecasters and presenters, and graphics. “MeteoGroup is a service provider that relies on the national meteorological agencies to provide the data, taking data from a range of sources, some of which will be ours, and serving it into the BBC the way the BBC wants them to,” he says. “I don’t really see the public will notice a great deal of difference.”



Familiar weather presenters will remain on screen, but employed directly by the BBC rather than the Met Office, which trained them. As presenters made up the bulk of costs, it is hard to see how that shaves much off the BBC bill. Last year the Met Office invoiced the BBC substantially less than £3m; a fraction of the Met Office’s £230m annual funding.



As it is a trading arm within the Department for Business, Energy and Industrial Strategy, 85% of its funding comes from public sector contracts, the bulk through its public weather service role. This provides free data to other broadcasters, including ITV and Channel 5, as well as to government departments and emergency responders. The BBC will continue to broadcast its severe weather warnings to ensure everyone works from the same hymn sheet in a crisis.

Other big clients are aviation, both civil and military, the Environment Agency and transport. Varley says the future is international, and the Met Office is working to promote scientific collaboration with emerging economies, first and foremost China. Through the Department for International Development, it is also advising on drought and flood risks in Africa, improving early warning systems, even forecasting the best time to plant seeds.



Its job is not to forecast weather, says Varley, who is also the first vice-president of the World Meteorological Organization and president of EUMETNET, the European grouping of meteorological services. “Our job is to help people to make better decisions.”



The D-day map, hand-drawn in June 1944 by the Met Office’s group captain James Martin Stagg, who postponed the Normandy landings for one critical day, hangs outside the vast operations room. Next to it is a handwritten note from General Dwight Eisenhower, the supreme commander of the Allied Expeditionary Force, which reads: “Thanks. And we thank the gods of war we went when we did.”



Rob Varley, CEO of the Met Office. Photograph: Jim Wileman/The Guardian

Inside the operations room, data and graphics dazzle from rows of desktop screens in a space dominated by an enormous real-time graphic of swirling clouds and weather fronts. There is a flood desk and a volcano desk, which is showing a violent orange plume shooting out of Iceland. “Don’t worry,” reassures Mark Seltzer, monitoring. “These are theoretical runs in case something goes on today.” On the space desk, Michael Lawrence is checking “to see what the sun throws out at us”, coronal mass ejections thatcan hit the Earth’s magnetic field, affecting national grids and communications networks as well as space missions.



The chief meteorologist, Paul Davies, is examining forecasts on the aviation desk. “We are one of only two centres in the world to provide forecasts for the whole of the world for all the major long-haul airlines,” he says. Airliners plot paths to avoid clear-air turbulence or to hitch rides on jet streams, saving time and fuel.



Then there’s the shipping desk. Nigel Bolton is staring at a hypnotic screen of purple, blue, green and white computerised fletches – green is force 6, purple force 7, white force 8. The poetry of the shipping forecast, provided through the Maritime and Coastguard Agency, will continue on BBC radio, to the delight of fans and sailors alike.



Competing in the digital age is crucial for the Met Office, says Dee Cotgrove, the director of communications. The tipping point from TV to online as the public’s main provider of weather information has crossed over. There have been more than 4.6m downloads of the Met Office’s award-winning app launched last year, and the number is growing by thousands each week.

A chatbot using artificial intelligence is in development, as is a programme for Amazon’s Alexa flash briefings. “We go where the public are,” says Cotgrove. Recent research is looking at incorporating regional wealth colloquialisms – such as “parky” and “Baltic” – into forecasts to improve public understanding.

But it is in the aptly named cloud that she sees the future for the Met Office’s huge cache of climate data. “The way data will be used in the future is perhaps not something we can imagine now, the sheer potential of sharing it on the cloud. Who knows what other uses, as yet undreamed off, will come from that?”