the got it pretty much OK in June. didn't we get 30C a couple of times?
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Nothing remarkable in that, you'd be entitled to expect that during a Summer as its nothing more than a par score and hardly a heatwave (it might be in Scotland) but then we're talking about borderline tundra.
You can look longingly at high pressure systems out in the Atlantic and they can give pleasent enough days at about 25c but the serious hot weather comes from a stationary system over North Africa called the Azores high. This is largely immobile and sucks in warm air that just heats up, and the more it sucks in, the more it continues to heat up. If this is able to force its way northwards then it sits on top of us and pushes the Atlantic weather systems to north of the UK. To a large extent it's controlled by the jet stream. If the jet streams comes to far south it surprsses the azores high and it takes up residence over Sourthern France and North Africa where it's impact is even more pronounced due to their more southern lying latitiude (as indeed 100's died in southern France last year, and there was an outbreak of fires too). The Azores system requires that it is built up though, a bit like a crescendo to a symphony. Even if the jet stream finally released us from its clutches it wouldn't follow that the Azores high would automatically follow it and head north in burst of sudden heatwave. The air of over us won't have been warmed enough to encourage it to join in, and this needs to be built up. We'd be in unstable air which could go either way. Its slow moving system, and there's no guarantee that the Azores high would impose primacy over the occluded Atlantic fronts, unless it had reached a critical mass through the cumulative build up of hot air. A series of Atlantic fronts could easily disrupt it and provide changable and unsettled periods of weather instead as it needs high lead times to settle and develop its strength through drawing in more and more hot air before it is able to exert primacy over Atlantic systems and start pushing them to more inhospitable northern latitudes like Iceland, Norway and Scotland.
The pattern is normally settled around St Swithins day hence our forefathers who relied more on knowing the weather patterns than we for making a living noted. Admittedly they didn't know of the existance of the jet stream, nor how it impacted on the Azores high, but had noticed a pattern develop that at a certain time in the year, bad weather begat a month of further bad weather, as what had happened is that the Jet stream had pushed the Azores high too far south, and as it settled over the Mediterranean instead and it tended to stay there. This is basically all they were observing with their 40 day rhyme
We normally get an Indian summer on the back of it, but personally I'd rather have temperatures of 30C + in the proper Summer months than ones of 18-20 in mid Septemeber and early October.
Another shite Summer, 3 in a row now.
When you write your christmas present lists out for santa this year, be sure to put the Azores High on them please