Weather

David said the reason for the bad weather is that the Polar Jet Stream is further south than normal for this time of year but why it is so far south is unknown.

David explained what a jet stream is: "Caused by the meeting of air masses just under the tropopause where winds are the strongest. When two air masses of different densities meet here, the pressure created by the different densities causes winds to increase."

"As these winds attempt to flow from the warm area in the nearby stratosphere down into the cooler troposphere they are deflected by the coriolis effect and flow along the boundaries of the original two air masses.

"The results are the polar and subtropical jet streams that form around the world."

Typical Polar Stream in July

So what has been different in the last three years?

During 2007, 2008, and 2009 the Polar Jet Stream has been abnormally low across Britain lying over the Channel rather than lying north of Scotland.

"The exact reason for this is not fully understood but it is believed to be down to a variety of components including the warming of the Atlantic due to climate change, fluctuations from La Nina to El Nino, and recent volcanic activity in other parts of the world," said David.

"It has now been further south for 3 consecutive summers which is now contrary to the general trend of movement northwards of the jet stream that has been recently detected."

"Whatever the position of the jet stream though, it has a significant impact on the world's weather patterns and severe weather events like floods and droughts," he said.

"It is therefore essential that meteorologists and other scientists understand as much as possible about the jet stream and continue to track its movement, to in turn monitor such weather around the world."