nick sussex

Unfortunately still too much energy running over the top, but its a positive that we see some energy going into the southern arm of the jet. If that northern arm could relent a little then it would help matters, still we'll have to see whether any future outputs build on that.

The ECM at 120hrs keeps troughing further west with a stronger pressure rise to the east. Big differences between it and the GFS which has a flatter flow with the jet well into Scandi, will the 144hrs deliver a bit more potential? Interesting! that small low in the Atlantic could head east into the main trough and help kick it further nw, could be a nice 168hrs chart coming up!

EML the problem with those NAO forecasts is that they're merely a bi-product of the GEFS ensembles. So if the ensembles are barking up the wrong tree then that NAO forecast will also be wrong. In terms of cold potential I'd agree though nothing tangible on the horizon. I would however keep an eye on what the models do with that Atlantic troughing, its likely that high pressure will remain to the east and we should look towards the tilt of that troughing to see whether this becomes negatively tilted. I'm not saying the BOM is anything but a cannon fodder model especially past 144hrs but that gives an example of how you get from a mild southerly to something colder. As the trough pivots and becomes negatively tilted it forces high pressure further nw extending from the initial Euro high, once pressure starts rising near Iceland you have the start of a pattern change.

Yes certainly a spell of milder weather looks likely given where that troughing is likely to set up, but historically we've seen quite a few balmy southerlies turn into much colder se then easterlies. I think patience will be needed though and we'd need that troughing to pivot and orientate nw/se to force high pressure nw out of Europe. The CPC map on Friday was better in that respect as it had positive anomalies heading over the top of the troughing, the automated one not done by the forecasters on Saturday removed those positive anomalies. We'll have to see what happens tomorrow, the ECM ensemble maps are a mixed bag but a few stand out in terms of potential. http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2009112700!!/

Not much change in todays output but whats becoming more evident is that whilst the operationals are trying to work out where any troughing sets up this CPC map may well be closer to the money. http://www.cpc.ncep.noaa.gov/products/predictions/814day/814day.03.gif Broadly speaking high pressure to the east and low pressure anchored more to the west. This could bring some mild conditions in connection with a southerly flow but where does the pattern go after that? This depends on whether that troughing sinks or a portion splits and edges into Iberia forcing a change in the flow more towards the se, also how much energy continues to run over the top towards Scandinavia. As yet too early to say here but given the current state of the stratosphere if you're looking for colder weather its more likely to be coming from the east at least initially.

Quite a large difference of opinion between the GFS and ECM today. Even more so when you look at the CPC maps. http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php Those negative anomalies certainly don't back up the GFS 06hrs run which has a flat zonal flow into the heart of eastern Europe and Russia. The positive anomalies suggest high pressure in that region with troughing to the west, indeed more like the ECM but with high pressure further east than what it shows. In terms of the weather on the ground the ECM later output is infinitely better with drier conditions coming up from the se, on the cooler side with some frost. Looking at the upstream pattern NOAA do highlight a pattern change to a more zonal flow but also stress some uncertainty within that. AN UNUSUALLY CHALLENGING FORECAST THIS CYCLE WITH THE LATEST GUIDANCE AGREEING ON A PATTERN CHANGE AT THE START OF DAY 3/TUE...WITH THE LARGE CYCLONE CURRENTLY OVER THE WEST WEAKENING AND FLATTENING OUT OVER SOUTHEASTERN CANADA AS THE FLOW BECOMES PROGRESSIVE. THE NEARLY ZONAL FLOW WHICH THE MODELS SHOW ON DAY 3 CONTAINS NUMEROUS UNDULATIONS...ANY OF WHICH COULD LEAD TO SUBSEQUENT SOLUTION CHANGES IN FUTURE RUNS. Thats not to say some Greenland high is likely to pop up but that there could be some changes in Europe in terms of where any high pressure might set up. Theres a vast difference at this time of year between a more se flow and s to sw in terms of temps.

I think an easy assessment of todays output is unsettled in the outlook, colder showers some wintry, any snow accumulations mainly reserved for higher ground in the north. In the extended outlook if you want cold to remain then the neg NAO must not become west based. This is often a problem in these types of set ups. There has been some moderation in terms of the cold in relation to the initial colder shot, both the ECM and UKMO originally wanted to hold onto the straight northerly for longer,as we can see now another low pressure looks to track se'wards because of the timeframes what happens after this is uncertain. If you look at the ECM ensemble maps. http://www.ecmwf.int...t!2009112700!!/ It's easy to spot the members trending to a more west based negative NAO, once you get low pressure stuck over the UK the cold gets mixed out and you enter a more average showery type set up. We often see the cold pushed too far east with northerly topplers, the reverse problem often occurs with the trend in the later outputs, the cold funnels south to the west of the UK. So in a nutshell Negative NAO centrally based to the south of Greenland with Scandi trough= cold showery conditions West based negative NAO, core of heights near the Canadian Maritimes= average conditions with showers. Eastern based negative NAO= drier conditions for most of the UK, generally colder to the east with any showers more east and se as the flow often gets directed from a more ne quadrant. So thats what I'd concentrate on in future outputs, look out for events in the eastern USA and eastern Canada, low pressure track there does effect high pressure near Greenland.

I think people have to be realistic regarding snow in late October. Although there was a more recent event a few years back its very much the exception. Theres not even solid agreement on that cold plunge with the GFS pushing the main cold thrust to the east, although the rest of the models do indicate some much colder conditions let's see if the GFS comes on board and then re-evaluate the snow potential then. An outsider shot for some more interest would be a disturbance running se into the UK after the initial northerly.

It looks good for the Alps with a cold plunge and significant snow, which is the polar opposite of last year where the mountains were bare until the week before Xmas and then the snow arrived in copious amounts. I'd be wary of the infamous Icelandic shortwave spoiler appearing in later runs, the models are poor at these timesframes at picking up on this. A chance of some snow for higher ground in the north but at this range the 850's are subject to revision,so not worth getting too excited over until much nearer the time.

Certainly looks like a big change coming for mainland Europe aswell as the UK. The 850's heading south are very unusual for this stage in Autumn, I think its looking like there will be a cold plunge then another low heading se. The positioning of the cut off low in the Atlantic precludes a quick return to milder conditions but the point of interest is whether this type of pattern can last long enough to bring the UK an early taste of winter. Although pressure looks to remain high near Greenland there is a suggestion that the models might try and develop a more western based negative NAO. If that doesn't occur and the core of heights remain far enough east then it could bring some interest, more especially for northern areas.

Quite unusual to see such a big disagreement between the ECM and GFS/UKMO at 96hrs. Both the operational and control run of the ECM are having none of the low pressure moving ne, looking at the ECM ensemble maps very little support also. http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!96!pop!od!enfo!enplot!2012091900!!/ Of course given the higher resolution of the operational runs ensembles can sometimes lose the plot with this type of low pressure development. The UKMO fax charts at 84hrs develop that low to the sw and it will really be something if those charts are completely wrong at that timeframe. I'm sure all will be revealed this evening when we should get agreement at least on events within 120hrs.

Still some doubt as to whether that intense heat over Spain will make it into the UK especially se areas. We've seen these set ups shown a few times and the main heat gets shunted too far east, much depends on how far east that low gets and its orientation. French tv suggests we may hit 40c here over the weekend! Looking at the ECM/GFS in terms of 850's those 20s do get very close to the south and se so we'll have to see whether these make it over the Channel.

Theres alot of uncertainty regarding low pressure track at 168hrs from the ECM ensemble maps: http://www.ecmwf.int...t!2009112700!!/ If you look at some of those members they do hold low pressure further west which could drag up some warmer air from the south. Also its the track of this low even if it verifies to the sw. It would be nice to see a slow moving low stuck in the Atlantic to the west slowly filling and heading ne, that would help deliver some better weather but given the UK summer so far thats probably being too hopeful!

Yes so will I, whilst I don't want to spoil the fun of stormwatchers in here I certainly want to see a dry opening ceremony. There maybe some showers during the afternoon in London but that small trough shown on the fax chart is shifted eastwards during the evening, so these should hopefully recede in time for the start of the ceremony.

The 06hrs NAE tones down the precip and keeps the heavier amounts right on the East Sussex and Kent coasts. At this timeframe theres still room for a small adjustment north or south, the main area of thunderstorms looks to be just over the Channel.

Looking at the fax chart it does show a trough in the Channel which edges east as that weak front from the nw pushes se later on Friday afternoon. I think at the moment any storms look most likely for East Sussex and Kent, If you want a major light show I think you need to hop on the ferry and get over to France. For you lightning addicts you certainly would like being close to the Pyrenees, you can get some amazing displays, sometimes its dry here with storms in the mountains and with the right conditions with storms on the south facing side you can get a clear view of the mountains on the northern side at night as the lightning gives the most eerie light, I've never seen that type of light before in the UK. Personally I'm a bit phobic regarding storms, either I worry the lightning is going to hit the house, or we end up with a power cut, inevitably theres always something good on the television as the satellite gives up the ghost! Certainly I'm happy to see any storms stay in the Channel for Friday and keep clear of London!

True I was reading some comments online where you got the attitude from some people that because they don't live in London then they could care less, no Olympic Games can encompass the whole country in terms of venues. Some people almost want the whole thing to fail as to get back at the government without a thought for the athletes who have worked hard to get to an Olympics, or all the volunteers who are willing to give up their time to be ambassadors for the country. Theres a certain minority who can do nothing but bad mouth Britain, its utterly shameful and they can't even find it in their bitter hearts to wish for these games to go well or just be a little bit proud. I hope you have a great time at the dress rehearsal, I'm very envious but very excited about the Games and really look forward to Friday night. I have everything crossed that the weather holds out.

Yes well anyone gleefully hoping for a washout should be ashamed. Just like some of the miseries who have done nothing but moan about the Olympics, there were even people moaning on other sites about a few fireworks and noise from the Olympic dress rehearsal!

I didn't see anyone saying the Opening Ceremony was definitely going to be a washout more just that there was alot of uncertainty with a thunderstorm risk. Thats what the charts suggested and thats still a risk, although at the moment the thunderstorms moving up from France look like they may stay there. Theres still 3 days to go and the timing of those fronts to the nw could still also change. It's a case of just keeping our fingers crossed.

More than likely it will stay dry in London whilst thunderstorms down here knock out the satellite signal ! Unless theres a trough line then if its just showers then by 9pm they should start diminishing in the London area, I think its the second front which could be more problematical, that looks a bit more active. The BBC seem to be playing it safe, they probably will continue with the fence sitting even on Friday! Although it is a difficult forecast, we just have to wait and see and hope!

I think its now looking that any storms will be triggered by that front moving se rather than being imported from northern France. This makes the speed of that front pretty crucial to the Opening Ceremony, annoyingly the GFS 06hrs run brings the precip in at 8pm just ast the 00hrs did and the UKMO fax charts shows the front making further se progress than on yesterday evenings. We're left in a bif of a conundrum here as the GFS does show a clearance in the precip but typically after the ceremony is due to finish, that would just be rotten luck! So we either need a delay in that front or it to scoot through much quicker, at this timeframe there is still likely to be some changes so we just have to hope for the best.

High pressure continues to be reluctant to edge ne and we still see that troughing near or over the UK but this still remains a slack feature so its a case of showers and some sunshine in the medium term. A positive is that those Greenland heights diminish, lets hope that continues. In the shorter term looking at the fax chart this has moved that front to the nw se quicker and there still remains alot of uncertainty for the Olympics Opening Ceremony. Looking at the GEFS ensemble maps re precip it seems that at this stage we probably want to see a quicker progression of fronts as most of the ensembles have a clearance behind that precip which is largely shown to just be effecting the far se around the time of the ceremony.

Lol ! I'm not sure that Met Office operatives have infiltrated the data inputs yet OMM but there does seem to be little mention of the weather for the Opening Ceremony and you are right regarding some potentially heavy precip. I think that front moving se would intensify but perhaps high cloud ahead of it could reduce convection, those storms from France may well graze the se but I think the flow changes later as that other front approaches so maybe this is where the miracle dry gap comes into its own to save the Opening Ceremony!

The limpet trough returns and with it its equally hideous companion the Greenland high. This all culminates in unsettled conditions returning for the whole UK by Friday and not going anywhere fast. Any low pressure at the moment looks slack so showers will be slow moving, with some sunshine between the deluges. If only that high pressure would weaken to the north this troughing may edge a little further north and theres still a small chance that we could see the odd weakish ridge thrown ne towards southern areas to bring the odd dry day for the Olympics. Apart from that it looks a poor excuse for proper summer weather, still some time before the athletics start so we live in hope that there might be some changes but unfortunately this pattern looks very entrenched.

Did anyone notice that gap in the precip over London at 8pm on Friday? Miracle dry gap all systems go! Could we get lucky? Overall the UKMO and GFS look less than convincing , the UKMO in particular goes shortwave crazy at 144hrs to the west of the UK. Looking at the GEFS ensembles they have toned down the precip amounts for London for Friday, quite a few do have that miracle dry gap. It really is touch and go, the timing of the front moving se is still open for revision and those thunderstorms over France do get quite close to the se. I think we won't know till 24hrs out so until then just keep our fingers crossed, in terms of the medium term although we do look to have troughing near the UK, the flow looks quite slack and in any sunshine it won't feel too bad. Of course you do end up with slow moving showers but equally some places may get lucky with decent drier interludes.