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Last Updated: Friday, 27 July 2007, 09:48 GMT 10:48 UK
UK forecasts to zoom in on towns
Climate model of UK rainfall (Met Office)
Future forecasts will be able to zoom in on much smaller areas
Weather forecasters will soon be able to zoom in on regions that are the size of a town, UK meteorologists have said.

Currently, accurate forecasts are limited to county-sized areas; but a supercomputer to be introduced at the Met Office will give much finer detail.

Experts said this would help planning for extreme weather events, like the UK's recent downpours, as they could pinpoint areas most likely to be hit.

The Met Office said the forecasts would be fully available by 2011.

Speaking at a press briefing in London, Dr Brian Golding, head of forecasting research at the Met Office, said: "There are areas in which the forecasts we produce at the moment fall short of the ideal."

He said that the forecasts issued in the hours before last week's deluge were accurate on a large scale, but, when examined in more detail, could not pinpoint the towns and rivers that would be most affected.

He said: "We are focusing in on how to get that information better."

Quantifying probability

Supercomputer upgrades to the current Met Office systems, to be introduced in 2009, will help meteorologists to predict the weather down to areas that are less than five square kilometres, rather than being limited to areas that are about 60 sq km.

It would be like using a 15 megapixel digital camera instead of a one megapixel one, said Dr Golding.

The new supercomputer, along with new modelling research, will also help meteorologists to measure the accuracy of their forecasts.

Man wading in flood
The UK has recently suffered extreme downpours

Dr Golding said: "When we give a warning, particularly a severe weather warning, there are actions that can be taken, but some of them are quite costly and people want to know how sure we are of the forecast."

The supercomputer will allow meteorologists to run computer models with a multitude of slight variations.

He said: "If they are all pointing to the same story, then we can have confidence in that prediction; if they are all pointing to different outcomes, then the particular event is much less likely."

The supercomputer, which will be about 10 times more powerful than the Met Office's existing infrastructure, will cost about 100m.

However, Met Office scientists cautioned that having greater forecasting power alone would not be enough to improve planning for severe weather.

Dr Golding said: "We are working with the Environment Agency and other government agencies to work out how we can use this information to best effect."

More rain

The rainfall experienced by the UK this summer has made it the wettest early summer period experienced since 1766. Meanwhile, southern Europe has been suffering from record breaking heatwaves.

heat gauge
Areas in Europe have been having extremely hot weather
Extreme weather events like these would become more frequent in the coming decades, other Met Office scientists speaking at the briefing said.

Dr Peter Stott, a climate scientist at the Met Office, said: "We no longer have a stationary climate - what we thought of as a one-in-200-year event in the past is no longer relevant."

A recent paper published in the journal Nature suggested a significant human influence on global rainfall patterns.

Scientists said that globally wetter areas were getting wetter and drier areas were getting drier.

The study suggested that in the future the UK would have increasingly wet winters and drier summers, Dr Stott, who was one of its authors, said.

However, when it did rain it would rain harder, he added.

This summer's downpours have been caused by a broad band of low pressure sitting across the UK; while in Europe, high pressure systems bringing hot air in from Africa have boosted the temperatures.

Map showing location of jet stream
In a "normal" summer, the Atlantic jetstream directs areas of low pressure, which bring cloud and rain, to the north of the UK. High pressure systems over Europe and the Atlantic bring warm, settled conditions.
Pressure chart: 29/6/06. Source: Met Office

Map showing weather patterns in Europe
This summer, the jetstream is flowing further south allowing low pressure systems to sweep straight over the centre of Britain. It is also pulling in warmer air from the subtropics and Africa which is sweeping over south-eastern Europe.
Pressure chart: 24/07/07. Source: Met Office


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