Twitter footages from Nantes is showing a car being driven axel-deep in floodwaters down the high street; other pics showing trees uprooted by 60 mph winds. The leading tip of the line of storms is just off the coast near Worthing right now - will it manage to extend this far north or will the entire system transfer east, affecting Kent and the Sussex coast? This is proving quite a nail biter!
Stormy Weather II
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It looks as if the big low stationed out to the northwest will park itself right across the whole of the UK on Friday, and once established remain here in situ until at least Tuesday, possibly dividing into two centres dumb-belling around each other. There's been discussion on a weather website asking how come we've gone from exceptionally dry to exceptionally wet conditions in the blink of an eye, and it all comes down to the effect the warming up of the Arctic has on the jet stream. While there existed a sharp temperature differential between surface temperatures at the tropics and those at the poles, this resulted in fast west to east-moving jet streams, which maintained the formation and movement of depressions within a relatively narrow latitudinal range, with the occasional diversion north or south caused by blocking highs - notably the northward extension of the "Azores high" in the summer months, when the sun passes directly overhead at the Tropic of Capricorn, shifting the tropical convergence Zone to its south northwards, and the "Siberian high" in midwinter, where conditions in the northern hermisphere are at their coldest. Scientists have discovered something from the periodic "El Nino" becoming a more frequent event as a consequence of global warming, namely that the resultant piling up of the warmest ocean temperatures affecting us, which occurs to the west of Central America, with knock-on effects in the Gulf of Mexico, which is the birth place of many of our Atlantic depressions, causes much warmer than usual ocean and associated air currents to stream Arctic-wards up the eastern US seaboard, building larger than previous high pressures on their eastern side (our western side), which have been steering the warm sea temperatures further north than previously, bringing about Arctic melting. This brings about a greater equalisation of temperatures between the tropics and the north polar region, which, in turn, causes the jet stream, which steers the Atlantic depressions, to move in huge meanders, rather like a river in lower reaches crossing a flood plain. Likewise this creates conditions in the upper atmosphere similar to ox bow lakes, or cut off meanders: the low pressure systems move more slowly; the jet stream can make a u-bend temporary reversal allowing a blocking high to form, and the cut-off low becomes as it were stranded. Cold arctic air then streams down in the rear of the low from the north, helping maintain the low and delay its decay. And so, with the whole atmospheric momentum slowed, any location becomes trapped for lengthy periods in blocked weather systems - either dry or wet - and the situation and weather type remains locked in until pressures - which are the result of living on a revolving globe which is hotter in its middle than at its extremities - are released, and the equilibrium is restored.
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At about 5pm the clouds broke and partly dispersed to give welcome sunshine and blue sky, followed by a bit of a sunset, all very welcome after a very grey(although thankfully dry)day. Wednesday isn't looking promising for the volunteer gardening slot but perhaps the forecast morning rain will miss rather than hit - I can always hope! At least as a volunteer I'm free to call it a day rather than having to stick it out.
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Originally posted by DracoM View PostWonderful virtually cloudless [so far] day, warm sun, fantastic autumn colours, briskish westerly...what's not to love!
Caveat: erm......so far!!
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