New research may help scientists predict UK's summer climate

Researchers have identified a number of possible factors that may influence the Atlantic jet wet stream and can, therefore, help to predict summer climate from one year to the next.

The weather in the UK and northwest Europe during summers is influenced by the position and strength of the Atlantic jet stream, a ribbon of very strong winds caused by the temperature difference between tropical and polar air masses.

A northward shift in the Atlantic jet stream tends to direct low-pressure systems northwards and away from the UK, leading to warm and dry weather during summers.

But if the summer jet slips southwards then it can lead to the jet shifting the low-pressure systems directly over the UK, causing miserable weather like the one experienced in the first half of this summer.

The big question is "why does the jet stream shift?"

The report discovered that up to 35 percent of this variability may be predictable, a significant advance which may help in the development of seasonal forecasting models.

Richard Hall, the lead author of the study, said: "There is nothing people in the UK like to discuss more than the weather. This is because it can fluctuate so drastically, we can be basking in high temperatures and sunshine one week only to be struck by heavy downpours and strong winds the next."

"Our study will help forecasters to predict further into the future giving a clearer picture of the weather to come," he added.

The findings suggest the latitude of the Atlantic jet stream in summer is influenced by several factors, including sea surface temperatures, solar variability and the extent of Arctic sea-ice, indicating a potential long-term memory and predictability in the climate system.

Professor Edward Hanna said: "Working with The Met Office we were able to look at the different factors which may influence the jet stream, which paves the way for improvements in long-term forecasting."

Professor Adam Scaife from the Met Office said: "We've made big inroads into long-range forecasts for winter, but we are still limited to shorter-range weather forecasts in summer. Studies like this help to identify ways to break into the long-range summer forecast problem."

The research has been published in Climate Dynamics journal.