Wednesday 24 April 2013, 15:25
I am already receiving questions from viewers asking about this summer’s weather.
As ever, long range forecasting remains the Holy Grail to meteorologists, a complex subject with many different variables.
The wise ones amongst you might even prefer to turn away now!
But one thing we can all agree on is that the run of poor summers now stretches back to 2007; summer that year most of us will want to forget because of the severe flooding that occurred in June.
The culprit is the jet stream which has since 2007, on average, been positioned further south than normal.
In summer this leads to cooler, wetter weather; in winter we are left exposed to the cold from the north and the east.
There are various theories as to why the jet stream has behaved like this.
Low solar activity is thought to be one possible reason for the jet stream being forced further south, particularly in winter.
And, as I discovered towards the end of last year, researchers at Sheffield University believe warmer than average Arctic conditions can have a direct impact on our weather.
The Arctic has been one of the fastest warming places on Earth.
According to their theory, a warmer Arctic in summer and autumn could be weakening the jet stream.
Normally it would force its way across Greenland, but in recent years Greenland has deflected the weakened jet stream towards the UK and Northwest Europe bringing with it rain-bearing clouds.
So it’s interesting to note that the winter Arctic ice maximum recorded last month was the 5th lowest on satellite record, mainly because the negative Arctic Oscillation (AO) kept temperatures warmer than average across northern-most latitudes.
In the past, a negative AO in winter has favoured more extensive sea ice at the end of the summer melt season.
But in recent years, this relationship has not held and warmer Arctic conditions with low summer ice extents have followed winters with a strong negative AO.
It’s only one variable in what is the very complex and unreliable world of long range forecasting, but if this particular theory is to be believed - and please don’t shoot the messenger - it suggests we could be in for another cool, unsettled summer.
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Tuesday 16 April 2013, 15:30
Wednesday 1 May 2013, 16:13