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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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#1
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I'm surprised there aren't any weather warnings out for Sunday. The
latest Fax charts are suggeting a low will develop over England and areas on the Southern and South-Eastern side of this could be subject to some fairly intense convection, perhaps leading to thundery activity, but also some heavy and persistent rain. There will still be some warm and humid air to the SE of that low and the front that is likely to spawn it. Keep you eyes on the weather warnings; tomorrow's nice day (and today's done here) could well be paid for in spades in the South. Further afield; the Atlantic looks stalled. The gfs has a low sitting over us for a week, funnelling warm air Northwards through Eastern Europe and into Scandinavia and even into the Russian Arctic. After that, pressure is forecast to rise over Western Russia. Possible May Easterlies for the UK? Paul Simons writes about exactly that in The Tombs today and talked about the NW of Scotland sometimes having the best of the UK weather at this time of year, if the Atlantic does completely stall, allowing Easterlies to develop. Paul |
#2
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On Apr 25, 7:54*pm, Dawlish wrote:
I'm surprised there aren't any weather warnings out for Sunday. The latest Fax charts are suggeting a low will develop over England and areas on the Southern and South-Eastern side of this could be subject to some fairly intense convection, perhaps leading to thundery activity, but also some heavy and persistent rain. There will still be some warm and humid air to the SE of that low and the front that is likely to spawn it. Keep you eyes on the weather warnings; tomorrow's nice day (and today's done here) could well be paid for in spades in the South. Further afield; the Atlantic looks stalled. The gfs has a low sitting over us for a week, funnelling warm air Northwards through Eastern Europe and into Scandinavia and even into the Russian Arctic. After that, pressure is forecast to rise over Western Russia. Possible May Easterlies for the UK? Paul Simons writes about exactly that in The Tombs today and talked about the NW of Scotland sometimes having the best of the UK weather at this time of year, if the Atlantic does completely stall, allowing Easterlies to develop. Paul The Met Office still don't think the rain will be heavy enough for any kind of advisory/warning tomorrow. The FAX charts still show the development of that wave depression and I still think there could be some atmospheric fireworks in some areas and some very heavy rain with that set-up. The MO has the low centred slightly further North than yesterday, bringing some central areas of England more into the firing line. The 06z gfs shows quite a change from last night's charts from T180 (next Saturday) onwards and now brings us into that warm air that is forecast to extend right into the Arctic, North of Western Russia and Scandinavia. Svarlbad as warm as some parts of the UK in early May? We'll see! It does this by locating the low slightly more West of last night's location, now allowing the UK to bathe in Southerlies, which encourage another plume of warm air from North Africa. Paul |
#3
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"Dawlish" wrote in message
... The Met Office still don't think the rain will be heavy enough for any kind of advisory/warning tomorrow. The FAX charts still show the development of that wave depression and I still think there could be some atmospheric fireworks in some areas and some very heavy rain with that set-up. Some heavy rain is likely but the detail has varied a bit from run to run and hence the risk for any particular area is probably deemed less than the required 40% http://www.metoffice.gov.uk/weather/..._warnings.html To a certain extent this is reflected in the 1000Z issue Long TAFs which indicate moderate rain with no mention of heavy as yet for any particular airfield (30% risk threshold). GFS currently has the highest 48 hour totals over parts of northern England, more especially over the Pennines http://91.121.93.17/pics/Rmgfs48sum.gif Visible imagery has some deeper looking tops due west of Biscay http://www.metoffice.gov.uk/satpics/latest_VIS.html Jon. |
#4
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On Apr 26, 12:56*pm, "Jon O'Rourke" wrote:
"Dawlish" wrote in message ... The Met Office still don't think the rain will be heavy enough for any kind of advisory/warning tomorrow. The FAX charts still show the development of that wave depression and I still think there could be some atmospheric fireworks in some areas and some very heavy rain with that set-up. Some heavy rain is likely but the detail has varied a bit from run to run and hence the risk for any particular area is probably deemed less than the required 40%http://www.metoffice.gov.uk/weather/..._warnings.html To a certain extent this is reflected in the 1000Z issue Long TAFs which indicate moderate rain with no mention of heavy as yet for any particular airfield (30% risk threshold). GFS currently has the highest 48 hour totals over parts of northern England, more especially over the Pennineshttp://91.121.93.17/pics/Rmgfs48sum.gif Visible imagery has some deeper looking tops due west of Biscayhttp://www.metoffice.gov.uk/satpics/latest_VIS.html Jon. Finally got a weather warning! I've been convinced for a day that this wave depression would produce some very heavy rain, but pinpointing it was beyond me! It has ended up further North than it looked like it would get, but there has been some excellent convection in instability, in advance of the front, creating storms for some. Then, as the wave tracked NE, another area of deep convection has brought thunderstorms and heavy rain to the North Midlands and Yorkshire. The present weather radar shows that heavy rain now in in the NE of England/ SE of Scotland and there's another nice circulation producing some heavy rain over Wales too. That could drag some storms over the SW later - perhaps they are just beginning to show in the SW approaches. An interesting night to come for some! Many of us, however, may be left thinking what all the fuss has been about! Paul |
#5
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On Apr 27, 10:47*pm, Dawlish wrote:
On Apr 26, 12:56*pm, "Jon O'Rourke" wrote: "Dawlish" wrote in message ... The Met Office still don't think the rain will be heavy enough for any kind of advisory/warning tomorrow. The FAX charts still show the development of that wave depression and I still think there could be some atmospheric fireworks in some areas and some very heavy rain with that set-up. Some heavy rain is likely but the detail has varied a bit from run to run and hence the risk for any particular area is probably deemed less than the required 40%http://www.metoffice.gov.uk/weather/...warnings..html To a certain extent this is reflected in the 1000Z issue Long TAFs which indicate moderate rain with no mention of heavy as yet for any particular airfield (30% risk threshold). GFS currently has the highest 48 hour totals over parts of northern England, more especially over the Pennineshttp://91.121.93.17/pics/Rmgfs48sum.gif Visible imagery has some deeper looking tops due west of Biscayhttp://www.metoffice.gov.uk/satpics/latest_VIS.html Jon. Finally got a weather warning! I've been convinced for a day that this wave depression would produce some very heavy rain, but pinpointing it was beyond me! It has ended up further North than it looked like it would get, but there has been some excellent convection in instability, in advance of the front, creating storms for some. Then, as the wave tracked NE, another area of deep convection has brought thunderstorms and heavy rain to the North Midlands and Yorkshire. The present weather radar shows that heavy rain now in in the NE of England/ SE of Scotland and there's another nice circulation producing some heavy rain over Wales too. That could drag some storms over the SW later - perhaps they are just beginning to show in the SW approaches. An interesting night to come for some! Many of us, however, may be left thinking what all the fuss has been about! Paul- Hide quoted text - - Show quoted text - HI all, Monday - Another fascinating day weatherwise. That little wave has begun to occlude, but is still being accompanied by some very heavy rainfall in Fife and Perthshire. It's slow-moving too. There could well be reports of flooding with that lot. It shows that the uplift associated with this wave depression and the location of the heaviest precipitation at a given future point was extremely hard for the MO to predict. No weather warnings were given up until late on Sunday afternoon, as far as I'm aware and I can fully understand why. I was expecting the major area of uplift to be to the SE of the main trough and there were some significant trough lines and some thunderstorms, but they were concentrated in bands and many areas missed out and stayed dry. For the main trough and its developing wave to drift so far North, took forecasters by surprise; as did the intensity of the precipitation that developed around the centre of the developing low. So: not a great forecast, MO, late on the weather warning, but entirely understandable. Its possibly down to data grid sizes and the small area occupied by the "wet" part of that wave. The forecast models just didn't have enough data to produce accurate forecasts of precipitation intensity and location. Dead interesting though - as was that circulation over Wales last night and the rain which is presently over NW England, behind the main trough. It looks like an eddy effect, swirling behind the first wave, or it may be that the wave developed a double centre and the second on is beginning to decay and is being presently re-absorbed. Any other views on all this? Paul |
#6
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"Dawlish" wrote in message
... For the main trough and its developing wave to drift so far North, took forecasters by surprise; as did the intensity of the precipitation that developed around the centre of the developing low. So: not a great forecast, MO, late on the weather warning, but entirely understandable. Its possibly down to data grid sizes and the small area occupied by the "wet" part of that wave. The forecast models just didn't have enough data to produce accurate forecasts of precipitation intensity and location. I don't think that's how or why it happened. The main frontal zone was split with elevated storms tied to the forward upper front, effectively in the warm sector, with further storms developing to the rear of this in and around the shallow moist zone/near the surface front. Hence the wave, as far as I can tell, wasn't the key player that it was originally expected to be and didn't really develop over the UK. Also, given that much of the forward precip. was falling into a relatively dry boundary layer surface totals were likely to be low and not necessarily likely to trigger flash warnings. Either way all the models that I'd seen struggled with the complexity of it all and it looked like a very difficult day for those tasked with getting the detail right. 00Z ASXX http://www.wetterzentrale.de/archive...ka20080428.gif showing the split system. Jon. |
#7
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On Apr 28, 12:20*pm, "Jon O'Rourke" wrote:
"Dawlish" wrote in message ... For the main trough and its developing wave to drift so far North, took forecasters by surprise; as did the intensity of the precipitation that developed around the centre of the developing low. So: not a great forecast, MO, late on the weather warning, but entirely understandable. Its possibly down to data grid sizes and the small area occupied by the "wet" part of that wave. The forecast models just didn't have enough data to produce accurate forecasts of precipitation intensity and location. I don't think that's how or why it happened. The main frontal zone was split with elevated storms tied to the forward upper front, effectively in the warm sector, with further storms developing to the rear of this in and around the shallow moist zone/near the surface front. Hence the wave, as far as I can tell, wasn't the key player that it was originally expected to be and didn't really develop over the UK. Also, given that much of the forward precip. was falling into a relatively dry boundary layer surface totals were likely to be low and not necessarily likely to trigger flash warnings. Either way all the models that I'd seen struggled with the complexity of it all and it looked like a very difficult day for those tasked with getting the detail right. 00Z ASXXhttp://www.wetterzentrale.de/archive/2008/brack/bracka20080428.gif showing the split system. Jon. I agree, Jon. It certainly wasn't easy! I'm not sure why you say that the wave didn't develop over the UK. Did you mean "England" It certainly developed over the UK, though not so much over central England, as was forecast Friday/Saturday. Instead it developed over the far NE of England and finally gave some high rainfall totals over SE Scotland, triggering the eventual weather warning. It ran along the trough, pressure fell as it did so and a clear circulation developed, with a warm sector, which is shown to be occluding on the present FAX chart. Thank you for your analysis of the front over England though. Yes, there were clear pre frontal troughs, consistent with the front splitting, producing pre-frontal instability and the air was dry. In England, high rainfall totals only occurred along these lines of destabilisation and even then were not enough, as you say, to have triggered a weather warning. I've read reports of rain being seen at a distance, but very little being recorded at ground level. A lot of evaporation may have occurred in the precipitation from some of those lines of showers. Much of England, Southern Scotland, Wales and Ireland appears to have chicken pox today with some beefy showers, one of which is presently falling on Dawlish! With the stalled Atlantic I talked about, we're likely to have the unusual circumstance of a retrogressing low. It looks like it will move W to E, bringing us into the coold Northerlies that I'd forecast for the 1st May, but that now looks unlikely, with it heading into the Atlantic and allowing some warm air to spread across the UK for next weekend. Another possible, plume, 21C+, possible thundery breakdown and showers/bands of rain/strong sunshine in-between, all this week too! Suprb weather watching! Off out over the Haldon Hills soon, on my way to the gym. Looking forward to seeing some big Cu+/Cbs. I'll wave at Haytor from little Haldon, Will! Paul |
#8
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![]() "Dawlish" wrote in message ... I agree, Jon. It certainly wasn't easy! I'm not sure why you say that the wave didn't develop over the UK. Did you mean "England" It certainly developed over the UK, though not so much over central England, as was forecast Friday/Saturday. Yes, essentially England and Wales. I haven't looked at the totals but I only noticed one flash warning for NE England yesterday evening and if anything that looked to be linked to the activity on the surface cold front rather than the wave/developing occlusion. Jon. |
#9
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On Apr 28, 2:43*pm, "Jon O'Rourke" wrote:
"Dawlish" wrote in message ... I agree, Jon. It certainly wasn't easy! I'm not sure why you say that the wave didn't develop over the UK. Did you mean "England" It certainly developed over the UK, though not so much over central England, as was forecast Friday/Saturday. Yes, essentially England and Wales. I haven't looked at the totals but I only noticed one flash warning for NE England yesterday evening and if anything that looked to be linked to the activity on the surface cold front rather than the wave/developing occlusion. Jon. Yes, could be. Thanks for your help. Paul |
#10
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On Apr 25, 7:54*pm, Dawlish wrote:
Possible May Easterlies for the UK? Paul Simons writes about exactly that in The Tombs today and talked about the NW of Scotland sometimes having the best of the UK weather at this time of year, if the Atlantic does completely stall, allowing Easterlies to develop. Paul Looking possible with developments over the alst couple of days on the gfs. http://www.wetterzentrale.de/pics/Rtavn2402.png at T+240 and http://www.wetterzentrale.de/pics/Rtavn2762.png at T+276 Some opportunities for some warmth, next weekend before that though. A warm and a dry Bank Holiday? Paul |
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