Predicting the unpredictable: inside the nerve centre of the UK's weather forecasts

Accurate weather reports can keep the country running – particularly in these uncertain times where changing conditions are ever-more apparent. Here's how they happens – and why they could be about to change.Friday, 7 February 2020

“Earlier on today, apparently, a woman rang the BBC and said she heard there was a hurricane on the way. Well, if you’re watching, don’t worry. There isn’t.”

Weatherman Michael Fish’s erroneous forecast on 15thOctober 1987 is perhaps the most infamous weather gaffe in British history. That night, the Great Storm, as it came to be known, battered southern England with hurricane-force winds. 18 people died, 15 million trees were uprooted, and damage was estimated at over £1 billion.

32 years on, should another storm of that magnitude approach these islands, it’s safe to say the Met Office – the UK’s national weather service – wouldn’t fail to spot it. Technology, computer modelling and forecasting techniques have advanced meteorically in the intervening years.

With just under 2,000 staff, the Met Office now has 15 bases around the country, ranging from its 20,000-square-metre headquarters in Exeter to satellite offices in Aberdeen, Edinburgh, and various military bases and airports. Internationally, there are stations in the British Overseas Territories in Cyprus, Ascension Island, Falkland Islands, Gibraltar and Antarctica.

This is just the tip of the iceberg, though. Constantly feeding into Exeter are weather observations from hundreds of different sources. The Met Office itself operates around 300 automated stations dotted around the country. Offshore, to the west of Britain, are 10 deepwater marine buoys, warning of weather coming in off the Atlantic. These were installed as a direct consequence of the Great Storm of 1987. (Too late for Michael Fish.) There are also lightvessels stationed in the Thames Estuary, in the English Channel and west of Land’s End. 

Information magpies

The Met Office piggybacks data from other parties. Around 70 ferries and coastal ships in British waters report back with their weather readings, and global readings are shared between other countries’ meteorological services through the World Meteorological Organisation. More locally, there are 150 or so voluntary weather enthusiasts around the UK supplying rainfall and temperature measurements. Then there are the thousand-odd gauges operated by The Environment Agency.

The variety of data coming in is staggering thanks to an armoury of measuring instruments. There are electrical resistance thermometers, pressure transducers, ultrasonic anemometers and tipping bucket rain gauges. There’s a network of 15 weather radars housed in radomes – golf ball-like structures on 15-metre-tall towers which use pulses of electromagnetic radiation to determine the type, intensity and movement of precipitation. Rather ingeniously, they listen for the echo of the pulses to bounce back from raindrops or snowflakes as they fall through the sky.

Weather balloons, charged with radiosondes and GPS units, are regularly released into the atmosphere where they measure temperature, pressure, humidity, wind speed and direction. The Met Office has six balloon stations in Sussex, Nottinghamshire, Northumberland, Northern Ireland, Cornwall and the Shetlands.

Aviation transponder pulses from aircraft (known as Mode-S) can play a part in weather forecasting, too. Every time an aircraft flies over an air traffic radar, the pulse it sends reveals its air speed and ground speed, allowing the Met Office to calculate wind speed and direction. Over six million observations like this come in every day.

(Read: Why some people risk their lives to record extreme weather.)

Even lightning strikes are measured. Across the UK and continental Europe, devices called ATD (arrival time difference) nodes listen out for electromagnetism during electrical storms.

Finally there are the satellite observations. On a hill beside their Exeter HQ, the Met Office has four operational dishes – two tracking polar-orbiting satellites, and two tracking geostationary satellites. This is perhaps the most expensive technology of all. To keep costs low, European countries share the service through an intergovernmental organisation called EUMETSAT.

Jim Trice is head of observations projects at the Met Office. He explains how the technology he and his colleagues use is constantly evolving. Right now he’s rather excited about teaming up with the UK’s telecoms providers to devise a method of taking highly detailed rainfall readings from the thousands of 5G antennae soon to spring up all over the country. He says the technology has already been proven on 3G and 4G networks in countries such as Israel and the Netherlands. Concern about 5G's potential impact on forecasting are being looked into – the current position is that the Met Office have 'lobbied Ofcom for a reassurance that filters will be put in place' to ensure that the frequencies utilised by both 5G and the satellites that read water vapour data. There is the suggestion that the new network may even be useful.

“[Readings] will be more powerful with 5G networks due to the increased density of connections,” he adds. “This street-scale information could be particularly useful in urban areas where intense rainfall can quickly result in flooding.” 

He also points to next-generation lidars (3D laser scanners) as a useful future technology for measuring humidity. And he suggests we might soon see autonomous weather buoys out at sea which could use their own propulsion systems to move around.

(See amazing images of landscapes from LIDAR surveys.)

Perhaps most intriguing of all is the idea of using autonomous cars as mobile weather stations. Imagine if, in the near future, the UK’s roads were populated by a vast fleet of self-driving cars, each of which could measure the weather and send data back to the Met Office. “Some of my colleagues are in discussions with transport companies,” Trice says, not willing, however, to reveal which companies. “There’s a whole variety of metrics their cars would need to understand, from fog and rain to wind and temperature.” 

Crunching the numbers

All in all, this amounts to billions of pieces of data pouring into the Met Office every minute of every day. Gathering it all is one of the most powerful weather computers on the planet – the Met Office supercomputer, with its two petabytes of memory and 24 petabytes of storage. (A petabyte is 10 to the power of 15 bytes). Built by a company called Cray, and completed in 2016, this comprises three main systems. Two identical computers, known as Cray XCE and Cray XCF (no snappy nicknames here) sit in separate halls in the main building, providing “time-critical operational weather forecasts”, while the third computer, Cray XCS, lives in a nearby science park, providing “research, development and collaboration capabilities”. When they were first commissioned, these three machines were among the top 50 most powerful computers in existence.

“Beyond two weeks ahead, there’s very little predictability, especially when particular storm systems are involved.”

David Walters

It’s technology which, the Met Office claims, gives the nation £2 billion worth of benefit thanks to better weather forecasting at airports, better flood prediction, more detailed information for the energy markets and climate impact research.

How accurate can we get? 

Dr David Walters is head of the research to operations team, and it’s his job to use the supercomputer to model weather forecasts. He explains how computer science has advanced so much that, using pressure readings, a four-day weather forecast today is as accurate as a one-day forecast was 30 years ago. “Even 20 years ago, the idea of postcode-based forecasting would have been an alien concept,” he adds.

And when it comes to temperature forecasts, over 86 per cent of minimum temperatures and 95 per cent of maximum temperatures are accurate to within two degrees.

If that’s not enough, Walters promises that forecasts will become even more exact in the future, offering precise predictions up to two weeks ahead. “But there are limits to accuracy,” he concedes. “Beyond two weeks ahead, there’s very little predictability, especially when particular storm systems are involved.” There are simply too many variables.

The Met Office works hard to assimilate and interpret all the data it gathers. Leading the way are the 25 or so staff on each shift toiling in the operations centre, arguably the most important room of the building. Here, working 24 hours a day on a rota system, employees are divided among nine clusters of desks, each cluster housing a separate team. Some issue flood and extreme weather warnings, or study solar flares, or observe atmospheric weather affecting aircraft. Others observe weather on the road and rail networks, or communicate with the media, or field calls from the public. The Shipping Forecast, much loved by Radio 4 listeners, is here too, with its own cluster of desks. 

“This is the pinnacle of any meteorologist’s career.”

Steve Ramsdale

The most vital cluster of all – and the one that ultimately determines the weather we all follow on TV and online – is called the guidance unit. Here, the chief operational meteorologist (the Met Office has eight in all) keeps the entire nation abreast of the weather, and warns of impending problems.

“This is the pinnacle of any meteorologist’s career,” says Steve Ramsdale, one of those eight chiefs. “These are some of the best meteorologists in the world.”

In front of the guidance unit, and dominating the entire room, is a five-metre by two-metre video screen, displaying maps of the British Isles and Western Europe, monitoring rainfall, cloud cover, water vapour, wind and lightning. These are enlarged versions of the images on the chief operational meteorologist’s computer monitors, so that, on the day National Geographic visits, in the bottom right-hand corner is a photo of his children on holiday. It’s a reassuringly human touch amid all the science.

‘A massive buzz.'

The impact of all this information on Britain’s citizens, businesses and services shouldn't be underestimated. Will Lang is the Met Office’s head of civil contingencies services. He oversees a staff of 18 specialists who base themselves around the UK, helping emergency services, hospitals, the Environment Agency, transport operators, utility companies and local and national government whenever the weather misbehaves.

Like the Beast from the East, in March 2018, for example. “That involved all these organisations,” Lang remembers. “We had to give regular information on how much snow was expected and what the effects were going to be.” 

Rail and road transport operators were desperate for updates every few hours, as were hospitals. “It’s not our job to say what people should do, but we can give them the best meteorological advice,” Lang adds. 

Knowing that their advice saves lives gives Lang and his colleagues an enormous sense of pride. “There’s a massive buzz,” he says. “When things are busiest and most stressful, with big weather events, this is a hive of activity and people are rushed off their feet. But they’re helping people make good decisions. They’re thinking: ‘I wouldn't want to be doing anything else.’” 

Conversely, the job is especially taxing on the rare occasions when the Met Office gets its forecasts wrong. “We’re quite self-critical,” Lang adds. “We always look to learn from events.”

Like that event back in 1987 when Michael Fish missed the mark entirely. There was plenty of self-criticism then. 

This article was updated on 10 February to clarify the Met Office's position on 5G.

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