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uk.sci.weather (UK Weather) (uk.sci.weather) For the discussion of daily weather events, chiefly affecting the UK and adjacent parts of Europe, both past and predicted. The discussion is open to all, but contributions on a practical scientific level are encouraged. |
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#41
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On Apr 19, 9:53*am, "Will Hand" wrote:
"Dawlish" wrote in message ... On Apr 8, 1:14 pm, Dawlish wrote: Well, there you go.The possible warmth has continued for 5 runs, I can now be 75-80% certain of this: By 18th April at T240, the effects of the first warm plume of the year will be being felt in Southern England. Temperatures on the 17th and 18th of April will peak above 18C and may well be higher. Winds around this time will be from a Southerly quadrant and the air will have had its source in North Africa. This air could well be unstable enough to bring the possibility of heavy, perhaps thundery showers. If the showers stay away, Southern England, at least, will have some pleasant, warm conditions for April. It can never be a higher confidence forecast than 75-80%, as my success from the past is about 78%. It's not a certain forecast, as certainty doesn't come in to forecasting. See how it goes. Paul I always return to any forecast I make, be it good, or bad! OK a hopeless forecast. This one fell into the 20-25% of faliures and it ranks as a stinker amongst those (Euro stinker? No muck on the ground in the rain though in Devon!) . It's not even a near miss and it ranks on the abysmal level of the Cold Northerly I forecast at Easter 2007 (remember that glorious, warm sunny weather at an Easter which now sits in the warmest April for 350+ years?) The reason was a combination of a Southerly diving jet, producing cold uppers and an associated lee depression which is likely to track W to E along the channel and across Northern France. It has stymied any development of that warm plume that was shown on the gfs for a few days, in one form or another, 10 days ago. This was compounded by* the Northern blocking of Early April continuing and sitting there over Iceland, like a giant high pressure toad, squatting with its heavy haunches and putting up an impenetrable wall of toady atmosphere against the release of my predicted North African plume. OK, stretching a metaphor, but I hope you get the picture. Maybe I've got the first plume right, at 10 days, on the max temp record thread! Paul * Does high pressure at our latitudes result from the track of the jet, or does it alter the jet's path. Has this jet been forced South by an anticyclone which stretches from ground level to the 200mb hpa level, or did it form as a result of the jet tracking south? It's a chicken and egg scenario that I've always found hard to interpret. In this case, I'd go with the high developing and the jet being forced around it, but I could be wrong! Any clues, anyone? ===== NEW POST I cannot quote your previous text as Outlook Express does not recognise the format you used. It is the jet, itself arising from temperature variations, that forms the high pressure regions in our latitudes. Don't foget the global circulation Hadley cells that help form the various jets in the first place, which themselves arise from insolation and the earth's rotation. And then there are the Rossby waves affected by major mountain structures like the Rockies which meander around and alter the jet streams. The atmosphere should always be thought of as a system as per Systems Theory. Isolating various parts is good for understanding physics etc and causes of weather such as rain, thunder etc, but you need to treat it as a whole to get rid of chickens and eggs. Re your forecast. I too was interested in that southerly at T+240. I was tempted to say something but my instincts (backed up by ensembles) told me to keep quiet. I've gone for a warm and sunny weekend next weekend instead! We all make bad forecasts, nobody is perfect, not even WL :-) No pongs up here, I had a good sniff last night but all I could smell was wet grass! A bit of a pong yesterday morning as I reported but very very faint and there a lot of cess pits anyway in these upland parts :-) Cheers Paul, Will --- Hide quoted text - - Show quoted text - Thanks Will, that sounds highly sensible and the textbook theory is that the jet causes the surface pressure systems and it is good to be reminded that it is a system that cannot be broken into its component parts and there is no chicken and egg, really........... however, it still bugs me! This is such a weak Southerly jet in this particular Rossby wave and the I think the blocking anticyclone (and now it is memory, which is never a good thing on which to base any scientific speculation) formed before the jet tracked southwards. I'm sure you are right and I know the theory.............but it still makes me think! Paul |
#42
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![]() "Dawlish" wrote in message ... I hate this country. Dave R. I have to disagree there! It's one of the most interesting in the world for weather watching; maybe THE most interesting. Just imagine being in Bahrain! Mind you, if you hate this country, there are a whole load of others that you could hate living in! *)) Spring NOT coming Yes I knew you'd say that its been said a multitude of times about the interesting British climate. Bahrain? a bit extreme however. Well ok its interesting yes but all I ever seem to do is scan the forecasts for some nice settled weather certainly at this time of the year (I dont do this from November to March) until say November when you just cant get outside anymore without loads of heavy incumberant clothing then theres the dark and short days so miserable they are. Pessimistic I am and theres only 75 days left until Midsummer with the prospect of there not being one then its all downhill again. Anyway this year I am retiring which is about time an I know one thing I wont be around for 2008/9 Nov - March in the UK I'm off somewhere i dunno were yet but i'm off south - leave you all too the wonderful british climate. Dave R. |
#43
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![]() Another run with hints of a warming, but a subtly different set-up and the outside chance of a plume heading our way. http://www.wetterzentrale.de/pics/Rtavn1802.png Still not enough confidence for any kind of forecast at T240. This mildness has come in under my radar. Some warmth would be very welcome, though. Paul Wow that looks fantastic I hadn't seen that one at the wetterzentrale site and only have to wait until the 12th! fingers crossed and thks Dave R. |
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