Brace yourselves: the perfect storm is coming your way

Gales, tidal surges, flooding and widespread havoc - but this time it's only a simulation

A perfect storm is about to gather off the east coast of Britain, whipping up the sea and menacing the coastline with gales and torrential downpours. Before long, it will head south and make landfall, sending a wave of water up the Thames estuary, battering the hotchpotch of flood defences erected since Victorian times.

The surge will trigger an alert to raise the Thames barrier, but downstream widespread breaches and floods are expected. Where the most vulnerable areas will be is anyone's guess.

Fortunately, the storm and the havoc it brings will go unnoticed by anyone except a handful of the country's leading scientists. The extreme weather, like the damage it causes, will exist only in the ones and zeroes of a programme running on powerful computers at the Meteorological Office in Exeter.

The virtual storm lies at the heart of an unprecedented £5.5m experiment involving the Environment Agency, the Met Office and eight universities to test cutting-edge artificial intelligence systems designed to foresee dangerous storm surges. Beginning tomorrow, they will be put through their paces, when a team led by Brian Golding, head of weather forecasting at the Met Office, will digitally recreate a storm that struck Britain in November last year.

Over the following three days, weather experts will play along, issuing forecasts of the storm's intensity and path across the sea, while separate teams of scientists race against the clock to feed the information into their computers. Some aim to churn out predictions of how big a storm surge will hit London. Others will use 3D digital maps to reveal how water might gush through the urban sprawl and what areas are most at risk of flooding. Another team is charged with deciding whether the public can be given accurate warnings in good time.

Together, they will need to answer pressing questions: should the public be warned? The emergency services? Should the underground be closed and the military put on standby to start shifting sandbags? "It's going to be one hell of a nailbiter. It'll reveal any cracks in the system," said Ian Cluckie at Bristol University, who heads the Flood Risk Management Research Consortium.

When the real storm hit in 2005, the wall of water it sent up the Thames caused little concern because it arrived on a neap tide, when water levels in the estuary are at their lowest. In the simulation, the surge will be electronically pasted on top of an extremely high spring tide due on September 30 2015. It will amount to a rare but entirely plausible storm surge of up to 3.5 metres (11ft) charging up the Thames on the highest tide for 25 years.

To make matters worse, the Met Office will introduce a nasty kick. By programming strong northerly winds into the simulation, the swelling river will be blown up against the riverside defences, straining them beyond their limit.

The simulation will give the researchers a unique opportunity to test whether artificial intelligence can predict such events and also be used to save lives and prevent damage. "We want to see if these systems can tell us further ahead when we've got a major issue. And we want to know definitely what's going to happen, because if you get a pile of false alarms, it just causes chaos," Prof Cluckie said.

The Thames barrier is old engineering, but its designers anticipated rising sea levels and worsening storms. By 2030, it will still be able to shield against a freak one-in-a-thousand-year storm surge topping 7 metres, but the flood defences downstream, in low-lying Thamesmead, for example, are a mixed bag of earth embankments, grassy flats and sheet pile walls - piles set close together. "They are so different and they each have their own ways of failing," said Andy Batchelor, Thames tidal flood risk manager at the Environment Agency.

The test is part of crucial planning for the unexpected that could prevent a real disaster unfolding. When Hurricane Katrina was bearing down on New Orleans, officials knew from simulations that protective levees would be breached and lives would be lost. "If you don't have a plan, you end up repeating what went wrong with Katrina. If the worst does happen, you don't want to be looking on and scratching your head wondering what to do next," said Garry Pender, of Heriot-Watt University in Edinburgh.

The simulation will give the Met Office a chance to test another fledgling technology - ensemble forecasts. Instead of issuing one forecast for the storm laden with uncertainty, Met Office staff will issue more than 20 to cover the breadth of possible futures. Whether scientists and their computer models can cope with such a swamp of information is unknown.

Throughout the three-day simulation, Hazel Faulkner and her team from Middlesex University will check how information is passed between the groups. Even if individual groups perform perfectly, if their advice is misinterpreted by others, it could badly damage the emergency response to the storm.

"Science is couched in such different language that sometimes it fails to deliver what it should. We're trying to improve that without losing the sense of the message," she said.

Ultimately, the research team believe they will be able to use artificial intelligence systems to foresee dangerous storm surges up to a week in advance. Bulletins including maps of areas under threat and simple advice could then be sent to mobile phones in regions at risk, with specific instructions given to local TV and radio stations to help protect the public.

In the quiet after the storm, the teams will reconvene to pick over events to see if their new hi-tech systems worked quickly and accurately enough to make a difference. "You have to do these tests. If you hear a storm surge bigger than you've ever seen is on its way, you want to know you can cope with it," Prof Pender said.