Earlier predictions of floods

Earlier forecasts of floods could soon be made possible with the introduction of improved mesoscale modelling and radar technologies in the UK, according to Prof Ian Cluckie of Swansea University.

Cluckie claims that historic data on weather patterns are proving less useful as the effects of climate change create more extreme and unpredictable weather patterns. He believes implementing technology that can provide earlier predictions will be crucial to preparing for these floods in the coming years.

‘As the atmosphere gets hotter, it has a greater ability to absorb moisture,’ he said. ‘That doesn’t necessarily mean thunderstorms all the time but it can mean huge structures of rainfall hidden inside fronts, which is precisely what’s happened in Cockermouth and Workington over the last seven days.’

The recent floods in Cumbria were caused by a slow-moving front of air that came in over the Atlantic. Large areas of depressions around these fronts were embedded with intense rain cells, which can be difficult to model accurately with existing radar technology.

‘Forecasting technology is absolutely improving,’ said Cluckie. ‘We now have greater supercomputing power and a better understanding of our physical surroundings. We have developed the resources over the past few years, particularly for dual polarisation radars and mesoscale modelling. It is now a matter of investment and testing of these systems.’

Currently, the UK has a network of 15 rainfall C-band radars that are analysed by the Met Office. These radars are dopplar and can determine the motion and velocity of storm cells. However, a new radar based on dual polarisation technology is currently being tested by the Met Office at Thurnham in Kent, which could replace these systems.

This radar is hoped to improve the accuracy of rainfall prediction by being able to discriminate between different forms of precipitation. Unlike conventional radar technology that can only send out horizontal radio waves, the system is able to produce both vertical and horizontal pulses to provide more detailed information of rain cells.

‘The new kind of radar is at a key point in terms of decision making jointly between the Met Office and the Environment Agency,’ said Cluckie. ‘If they were to upgrade the network to these multi-parameter radars, it would involve expenditure over a period of three to five years at a cost of around £40m.

‘Britain took the lead on this by investing in research for the technology,’ he added. ‘However, other countries have now caught up with us again and France, Germany and the US have all made the decision to bring these into our National Network. If we follow their example, I think it will have a huge impact in providing better estimates.’

High-resolution numerical weather (mesoscale) models are another area in which the UK is hoping to improve its forecasting capability. These systems use a mathematical model of the atmosphere to provide a set of equations that can predict future weather fronts.

‘The reason we couldn’t develop this system in the past is that the mathematics is horrendous,’ said Cluckie. ‘There is very high-resolution micro-physics in these things but this has been improved over the years alongside computer power, which the Met Office is enhancing at the present time.’

The current forecast model system is able to analyse weather at a resolution of around 40km over the UK, meaning that 160 million equations have to be solved to understand the atmosphere 15 minutes in time.

While this is sufficient for general weather conditions, the resolution is unable to represent convective clouds, which are often responsible for the UK’s most damaging weather.

However, improvements in supercomputing capabilities have allowed the Met Office to embark on a project to develop mesoscale models with a resolution of around 1km – enough to represent thunderstorms as they form.

Cluckie said: ‘The problem with the recent floods in Cumbria is that, while they could have been normal extreme floods, it is more likely that they were that intense because of impending and current climate change.

‘Technology in this area is improving and will continue to do so,’ he added. ‘However, we have to keep in mind that more heat will create more chaos and forecasting this accurately is only one part of the challenge we face.’