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Showing content with the highest reputation on 30/11/14 in all areas

  1. Although the recent model runs have produced some tantalising possibilities of a northerly blast in the coming days, there has been no consistent trend in that direction. However, the current setup has some intriguing potential which is worth mentioning. Before I do though, I must say that this last week the models over overestimated the eastward progression of Atlantic systems, with the European HP holding its ground quite well. The upper vortex to our south will, while it lasts, inevitably lead to some form of upper ridge to the W, and the models take this and predict some transient HP for much of the coming week, which is fair enough. However, 2 things: there is currently a significant influx of very cold air heading in N Russia which would, I think, favour strengthening HP NE of Scandinavia. The models appear to brush this feature aside. Second, over several runs, the GFS has been developing what appears to be some sort of sub-tropical low towards next weekend moving N from N of the Caribbean, which if it were true, would be most unusual this time of year. But crucially, if it happened, a lot of very warm air would be pushed NW towards the US/Canada east coast and there would be, I think, a distinct possibility of a major upper vortex developing which would amplify the flow. As a result downstream, this could allow significant troughing into our area from the NW, perhaps feeding into what's left of the upper low to the S, which would pull in significantly colder air from the N. Fanciful speculation? Maybe, but as I mentioned on Friday, such troughing as I discuss has certainly come about in the past on a number of occasions. It just needs some decent upstream amplification to occur. The model output beyond the end of this week looks sillier than usual so I am inclined to ignore it completely. As I see it, even right now, there are still significant features in the upper and surface flow to suggest a much colder trend later in December. Where that cold comes from remains to be seen. I am keeping a close eye on 500mb developments in the coming days for a clearer idea of what's to come.
    38 points
  2. Here's my winter forecast for 2014/15. BACKGROUND In putting this together, I considered 7 different factors, some looking at their current state and others at their projected state during winter. I then compared these with previous years back to 1967 (where the data goes back that far), gave the factors in each year a score based on it's similarity to this year, and then assigned a weighting for each factor.( I won't go describing what each of the factors is in detail, or the influence they have, as this has been done by several forecasts already this year.) Below shows the factors considered and the weighting. .................... FACTOR ................ ............ ...........WEIGHTING.......... .......... ................ REASON Eurasian October Snow Cover Growth........ ............4 .......................Closest to the SAI I could get, useful for winter AO Quasi Biennial Oscillation (QBO).............. ...............4 ............... ...... Important in determining the strength of the polar vortex and chance of SSWs Multivariate ENSO Index (MEI)............... ........ ........4 .......... ............ Can alter the jet stream, influence SSW risk and more Kara/Barents Sea Ice Concentration .......................2 ........... ........... Influences Arctic and Eurasian winter weather patterns, NAO N. Atlatic Sub Tropical Gyre SST Anomaly...............1.............. ......... Can influence the state of the winter NAO NE Pacific SST Anomaly Pattern ............. ...............1 .............. ........ May alter the jet stream as it transits North America October Pattern Index ...................... .......................2 ............. ......... Might be a strong predictor of winter AO and CET anomaly So for each of the factors above, their current state and state in previous years were compared, and a score given based on the weighting system. This data was added into a spread sheet and each year was given a percentage value based on it's similarity, across the factors listed, with this year. Then the years with a similarity of greater than 50% were used for further analysis, these years were 1968/69, 1970/71, 1972/73, 1979/80, 1986/87, 2002/03, 2003/04 and 2009/10. Further analysis was then carried out by creating composite maps, and analysing the CET and AO values. This formed the basis for the forecast. WINTER FORECAST 2014/15 Below is the DJF SLP composite map A very clear signal for higher pressure to our north, and lower pressure just to our south. This set up would indicate an increased likelihood of easterly sourced winds and below average temperatures across the winter as a whole. Here's a look at each winter month in more detail. DECEMBER A very weak signal over December, with a slight positive anomaly showing over Scandinavia. This would suggests a lot of uncertainty in December. December AO The average December AO over the composite years is -0.42, with two months above 0.5, three below -0.5 and three close to average. This is skewed slightly by the -3.4 value in December 2009. Overall, a weak -ve AO signal increases the chance of cold conditions very slighty. December CET Across the years used, the average December CET value 4.8C, or 0.2C above the 81-10 average. This consisted of 4 above average months, 2 average months (within 0.5C) and 2 below average months, ranging from 3.0C to 6.2C. Like the AO, there's not a strong signal, but very little chance of a significantly cold month with a CET below 3C. December Overall The composites suggest a +ve SLP anomaly over Scandinavia, but it may not be strong enough to exert a strong influence on our weather. The data seems to suggest that significantly above or below average conditions are unlikely during December as a whole. Overall, the chance of milder than average conditions is greater than cooler across the British Isles. JANUARY A very strong signal is evident for January. A very strong +ve SLP anomalies are present from eastern Greenland across to Scandinavia, with strong -ve anomalies to our south. A pattern like this would bring an increase in easterly winds, and likely cold conditions. January AO The AO averaged over the composite years is very low, at -1.44. This would indicate a strong likelihood of a disorganised polar vortex and cold plunges across the northern hemisphere. Of the composite years, only one had an AO above 0.5 in January, with two average and 5 below average, of which three were under -2. January CET The average January CET across the composite years was 3.6C, or 0.8C below the 81-10 average. This consisted of 2 above average months, 3 average and 3 below average, with a range from 0.8 to 5.5C. Overall, a moderate signal for a below average CET, and so below average conditions over the British Isles. January Overall The overall signal for January is for a disrupted polar vortex and a high likelihood of high latitude blocking. This increases the chances of significant cold outbreaks and a below average months overall. Given the composite anomaly map, with both strong +ve and -ve SLP anomalies close by, a slight shift could give wet or dry conditions, but given the increased risk of easterly winds, below average precipitation is favoured. FEBRUARY The blocking signal for February weakens slightly, but is still present. The shift in the highest anomalies towards Greenland suggests an increase in northerly orientated air streams over the British Isles with much less of a Scandi high. The overall pattern would, once again, bring an increased risk of below average temperatures. February AO The average February over the composite years is moderately low, and -0.94. This consists of one month above 0.5, two average and 5 below 0.5, of which one was below -2. This suggests an strong chance of a disorganised polar vortex (though not as much as January), with significant cold outbreaks and increased blocking across the northern hemisphere mid to high latitudes. February CET The average CET across the composite years is 3.9C, 0.5C below average. This consists of two more than 0.5C above average, 3 close to average and 3 more than 0.5C below average. A weak to moderate signal for a below average CET, and so below average conditions over the British Isles February Overall While not as strong as January, the overall signal for February is for a continuation of the disrupted polar vortex, but with a focus toward a -ve NAO rather than general northern blocking or a Scandi High. This increases the chances of below average temperatures across the British Isles. WINTER OVERALL It seems very likely that the AO will be -ve overall and that at least 1 month will have an AO of less than -1.5, most likely in January or February. Given the large shift from no clear pattern and weakly -ve AO values in December to strong blocking and very -ve AO values in January, a SSW event is likely to be the trigger that causes a shift from December into January. While there is little risk of a significantly cold December, there is a moderate chance of very cold conditions in January, and to a lesser extent in February. Precipitation is more likely to be below average in northern and western areas, especially in January and February, owing to the increase in easterly winds and northerly blocking To summarise, a mixed December with close to or mild temperatures overall, followed by a colder than average January to February producing a close to or slightly colder than average winter overall.
    20 points
  3. A lot of disappointment creeping in ref the flattening of the ridge later on. I'm not really sure why, it was never seriously on the cards. Everything on track for about 10-14 days onwards for a realistic opportunity of some proper amplification. And in the meantime, despite the (almost desperate) insistence by some it will be otherwise, it will be turning colder. Oh and this zonal train fuelled by the cold start in the US must be running late...
    20 points
  4. Hard to say, I find those weatherbell charts pretty but annoying to read... to the point I don't bother to click on them. I wish you'd put up wz charts instead as sometimes you make good sense.
    17 points
  5. I hate to pour cold water on some of the hopes in here. Really apart from the cold 'feel' to this week for most compared to what most areas have had over the last weeks there is currently little sign of any marked change. The upper pattern shows, see below for the general idea, http://www.cpc.noaa.gov/products/predictions/814day/500mb.php that is a flow from about WSW at 500mb for much of the period, and this is a consistent signal with NOAA over the past few days. This does allow for a 48h colder spell if everything falls right at the right time as cold air flows down the western side of a travelling surface feature. Once this has passed then the upper flow is going to revert to a similar pattern as indicated above. There is no signal even further out really for any marked cold plunge. If/when this does occur I would suggest it will be from N of west not east of north. The MJO does suggest (using the GFS model) that the phase, currently in 3 is going to move through 4-5-6-7-8 with a reasonable amplitude. This would give (looking at the 500mb patterns such phases give-see below http://www.americanwx.com/raleighwx/MJO/MJO.html the probability of some kind of northerly oubreak sometime beyond day 14-16 from now. All very tentative and perhaps best look to the views of several well read folk in the Stratosphere thread for information on what help for coldies may come from that area of the atmosphere. So to sum up, cold starts and coldish 'feelin' to some days but no major outbreak before mid December at the earliest in my view. Watch the 500mb anomaly charts, for sure I will post any probable change they may seem to be offering and read the views of several well respected members in the Stratosphere thread for further background signals.
    15 points
  6. A glance through GFS suggests a risk of snow wintry showers developing in the north later in the week and into the following Not much of a risk away from the Scottish mountains on Saturday before the risk rises again late Sunday and into the Monday (8th) So in the semi reliable timeframe and also backed up by the beeb we could see some wintry showers / longer spells of snow starting to develop in the north later in the week. Better than the Atlantic train of storms last December! ps the 00z had snow in the south I just didn't have time to post the charts earlier
    15 points
  7. HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY SUNDAY NOVEMBER 30TH 2014. NEXT UPDATE MONDAY DECEMBER 1ST 08:00 THE CURRENT GENERAL SITUATION Slack pressure over the UK will prevail with weak troughs slowly clearing SE but returning SW across the East later today. MODELS-2 WEEK HEADLINE Becoming mostly dry with just a little rain chiefly in the North at times. Some frost and fog patches in variable temperatures. THE JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble forecast continues to highlight a generally flat Jet Stream pattern with it's West to East axis lying across the North of the UK around High pressure to the South. GFS OPERATIONAL The GFS operational this morning shows High pressure dictating the conditions across the UK through the period. The positioning alternates between a point to the South with milder Westerly winds covering the UK and to the SW and West at times later allowing polar air to cross SE behind successive and stronger cold fronts with rain at times later followed by cold and frosty weather with some wintry showers towards the North and East later THE GFS PARALLEL RUN The GFS Parallel run is broadly similar in status although the push of colder air is less pronounced for the most part. It does show a separate High pressure crossing East across the UK and on to Europe making for more in the way of frost and fog for a time before colder air slips South again late in the run. THE GFS CONTROL The GFS control run mirrors the operational well this morning with mild Westerly winds affecting all of the UK with the North seeing some rain at times while the South stays fairly dry and benign day and night. THE GEFS ENSEMBLES The GEFS Ensembles also show a fairly flat pattern with persistent High pressure to the South and SW minataining generally benign Westerly winds across the UK with just the briefest intervention of colder conditions from the North at times before a pattern reset takes place repeatedly. UKMO UKMO today shows a riddge of High pressure about to topple SE across the UK late next week and weekend replacing the brief cold Northerly airflow across the UK after midweek. Dry and bright weather for many with frost and fog patches at night seem likely in rather cold conditions. THE FAX CHARTS The Fax Charts show a ridge of High pressure across the UK for the period with a NE flow over the South and a SW flow to the NW with dry and fine weather for many with areas of fog and frost in relatively dry and benign condions the most likely forecast GEM GEM shows a similar pattern to the rest with High pressure to the SW persistent and instrumental in providing a lot of dry and quiet weather for the UK with areas of cloud, mist, fog and frost at times the biggest factors controlling our weather. Occasional interventions of colder and more unstable weather will hit the North at times and these are indicated to perhaps trend South somewhat late in the run. NAVGEM NAVGEM brings a change to colder weather than the rest following a cold front South later this week with new High pressure forming near Scotland before drifting towards Scandinavia and allowing cold NE winds across the South to be complicated by disrupting Low pressure feeding in from the NW or West later with wintry showers and perhaps more generall rain and hill snow possible after next weekend. ECM ECM this morning is reverted back to a flatter pattern with High pressure always to the SW steering depressions crossing East to the North away from most of Britain. Winds will remain between West and North and generally light. Average temperatures will prevail with patchy night frost and fog mixed with cloudier and benign periods when a little rain in the North is possible. THE ECM ENSEMBLES The Ensembles continue to paint a poor picture for thos looking for cold over the UK with the pattern of High pressure to the SW or South and Low pressure to the North of the UK maintained on the 10 Day Mean chart today. NOTABLE TREND CHANGES FROM PREVIOUS RUNS The theme remains for the UK to lie under the influence of High pressure most likely positioned just to the SW of the UK over the period with a variety of long term solutions shown none of which point to sustained and notable cold weather. MY THOUGHTS Time is my enemy this morning so a short report from me again today but the general message is one of a revolving pattern based around a general message of high pressure to the South and SW and Low pressure to the North of the UK the general theme. With pressure quite High overall the weather will base itself as relatively dry with just brief outbreaks of rain from occasional troughs moving down from the NW at times. As each of these take place some colder air will be dragged briefly down with them accentuating the risk of frost and fog before milder and cloudier West winds return. Long term today I can only see a slow trend for the High to slowly pull back closer to it's native home of the Azores allowing slightly deeper encroachment across the UK of cold fronts from the NW at times later allowing a bigger chance of permitting some wintry showers across the NE in particular but even then I'm afraid such an event would likely be short-lived. I expect to see further slight changes in model output over the coming days, all revolving around attacks from the North in varying degrees of penetration but at this stage with the angle of Jet flow and the positioning of such pointing to be where shown only temporary phases of this remain likely taking us out towards mid December.
    14 points
  8. Going to issue an update of previous forecast, same general theme but seeing a colder balance between mild and very cold spells. DEC -- After a few mild days some cold anticyclonic conditions will develop, and with retrogression indicated, this may turn into an exceptionally cold mid-month period with below freezing temperatures in daytime and heavy snowfalls in eastern England and many parts of Scotland as well as exposed coasts of Northern Ireland and the Republic of Ireland. This bitter blast may be followed by slightly milder temperatures around Christmas and New Years but there is some chance of a white Christmas as recovery might be rather slight at first. Now revising December CET down to 2.0 C. JAN -- Very stormy to start as the Atlantic tries to regain a hold against an entrenched blocking pattern over Europe. Possible severe storms around 4th to 6th at the high energy peak of full moon and northern max. These may take the form of mixed rain and snow in many areas although where winds are strongest in south, a brief thaw and heavy rainfall event associated with temps briefly near 10-12 C. Scotland may not see much of this milder air and blizzards may develop. Exceptional cold is then likely mid-month, followed by much milder weather towards the end of January. The CET may be quite low but will go with 1.7 C. FEB -- Mild for a few days near the start of the month then blocking will return and it could produce severe cold at times. Some chance of a subzero CET month. Will say 0.1 for the verification. MAR -- It will remain cold for most of the month then break to quite a warm end of the month but not in time to make much of a dent in a subnormal CET value around 4.5 C. The basic difference (if any) between this and earlier forecast is that I have reduced the overall average temperatures although retaining a similar high-variability oscillation in pretty much the same time sequence. November showed only faint indications of this high-variability trend in the UK, more so in Ireland which has seen colder days recently than most of Britain, however, the hemispheric pattern is clearly winding up for a very active winter.
    14 points
  9. Nothing has changed since my last post, good riddance mild muck, hello and welcome to relatively much lower temperatures, especially overnight with frosts becoming more widespread along with fog patches which may linger in places with temps not much above freezing. A cold Northerly incursion is still likely by the end of the week with showers turning wintry in the north and looking further ahead, more frosts and the best of the fine weather in the south, more generally unsettled further north and west with average temps and persistent rain interspersed with colder,brighter and showery weather with night frosts..at last a seasonal spell during the early stages of winter 2014-15. :-)
    13 points
  10. Key similarities between all models this evening and that is for core position of heights to remain out to our west allowing the atlantic to attack from the NW by the end of the week - giving most likely higher ground in the north the first widespread snowfall of the season (rather late it has to be said). Another similiarity is the projection for the Polar Vortex to splinter somewhat away from Siberia and energy transferred to Canada/Greenland - though no major strengthening, it still looks to be in a fractured volatile weak state. Longer term - the signs are there for a generally unsettled run into the middle of December, temperatures near average with the chance of further attacks of polar maritime air from the north, reminds me a little of the first half of Dec 2011. Quite a seasonal outlook, nothing overtly cold nor mild with promise of widespread frosts, hill snow in the north, how early December should be..
    13 points
  11. Since there doesn't look to be any major cold outbreak in the next 10 days at least, and the knowledgeable think the cold will come after the middle of December, It is probably worthwhile looking at signs of this happening. The most important thing is the placement and strength of the Polar Vortex. There has been a trend for days now for the Polar Vortex to move to the East, and the low heights over Greenland to move away. ECM at day 9 shows this: At day 10 we see a very weak Polar Vortex, which the guys over on the Stratosphere thread expect to happen as we move into the middle/latter stages of the December: Obviously, if the Polar Vortex does move to the East it increases our chances of getting cold from the East, and heights building towards Greenland. I think we will get our first cold snowy spell when we get heights building towards Greenland giving us a Northerly. Recent runs have moved away from this but I think we will increasingly start to see this happen more often in the GFS FI. We saw this exact thing happen in last nights GFS. At day 15 this is an example of how I think we may get our first cold snowy spell: (Just the ridging to Greenland resulting in a cold NW) So I think the things should be looking for are: 1. A weakening of the Polar Vortex 2. The Polar Vortex moving East 3. Attempt of heights building towards Greenland
    13 points
  12. If you're here to use the strat as a forecast for cold and snow in your back garden - then, yes - sling the hook is a good suggestion. If you're here to learn about a newer aspect of the science of meteorology, pull up a chair and don't be so impatient!
    9 points
  13. Quite a nice run from ECM tonight, pretty much sub-zero uppers all the way through. Its lovely to see the UK covered in blue!! Welcome back winter was just wondering if the low pressure at the end would bring us snow next Monday/Tuesday? We'd have been in -4 850s for a couple of days and then the fronts and showers would come through in cold air too? Id hope for some wintryness at least on hills quite far south? Upon closer inspection, the uppers are actualy -5 from Midlands northwards, with pockets of -6 tucked in there:
    8 points
  14. Well i,v actually watched the GFS unfold today not usually what i do , certainly looks like our vortex Could be migrating east but as we all know a very unpredictable traveller who likes to park itself in comfortable well known locations where it feels at home ,so a possibility that it Could give us a taste of winter if as modeled today .But cant help but notice high pressure to our s west is also well modeled ,All a real pickle past 7/8 days so lets hope tonights ecm and others can shed some light ,but we are sat i think in a good position for possibilitys, enough changing spread in models also, so fasten your seat belts i think a change is very likely after next weekend but details still to be sorted atleast interesting times gang .
    8 points
  15. Sorry MODS if this is in the wrong place. BBC forecast for the week ahead and unusually looking at next weekend and a little beyond... the `s` word is mentioned http://www.bbc.co.uk/weather/features/30268791
    8 points
  16. First post from me for a VERY long time. Been following this Strat-thread for a long time now,some very knowledgeable people on here. Fascinating subject and i,m pleased to see Stratospheric Dynamics being used as a forecasting tool. About 14 years ago on (Other)weather site......I was very keen to get across the importance of Strat-Dynamics in the overall pattern of Northern Hemisphere winters.Nobody at the time, gave it much credence(apart from Steve Murr).I think he realized, as I did,that really, the wintertime polar vortex is the governor.Liken it to a giant flywheel,it gains its energy from the thermal gradient in autumn/winter.Like a flywheel,if you knock it,it will loose energy and slow down,untill it gains MORE energy,and speeds up again. Keep on knocking it and you will eventually slow it right down......and stop it. I think the classic events that took place in the Stratophere in December 1962,and Jan/Feb 1963 can be used as a benchmark in Tropospheric/Stratospheric dynamics.In late December 62,and early Jan 63 the polar vortex was a very cold,almost circumpolar cyclone.(This ties in with what Chionomaniac was saying about the vortex strength)It seems to me, that the kinetic energy that the votex gains,ultimately, can sometimes lead to its own DISTUCTION.The central temperatures of the votex were near to -85C,with a band of westery winds at 10mb sometimes exceeding 200kt. The Major Stratopheric Warming then was quite astounding,and explosive.Around the middle of January,10mb temperatures above Edmonton,Alberta.began a rise.Over five days,the temperature rose 67C.The changes in circulation in Jaunuary and February 1963 extended from the Tropopause to at least 55km. F5
    8 points
  17. Thank you kindly EML Network. I could just be talking a load of rubbish (not for the first time!) but I tend to trust my instincts when I spot something unusual or in some way significant in the model runs. You make some valid comments in your post re the movement of HP over the next week or so with cold fronts in between. I think we tend to forget sometimes that a great part of our day-to-day weather is pretty ordinary, but with, it seems, increasing incidence of more extreme conditions. Half the fun of model watching is being able to detect real signs of such events in advance as well as significant pattern changes, which the models don't often do in the >5 day range. But it's all good fun!
    8 points
  18. So UKMO gives up the ghost this morning and joins the others in their flat nirvana. The ECM once it decided to drop the more amplified upstream has become progressively more flat with each run. Overall after alot of uncertainty the models have settled on a rather uneventful outlook. Turning somewhat colder with high pressure never too far away. The ECM has dropped its mini tease re the high retrogressing and unfortunately is actually in tune with whats expected over the USA, a flat zonal picture is expected over there. If you want to draw on a positive at least the PV hasn't reformed into one foreboding blob to the north but unless theres some change in the outlook upstream then theres no way of drawing south some much colder air. On a slightly Schadenfreude view at least we won't have to put up with the Americans stealing all the cold and snow, its looking much milder over there with any cold reserved for well north of the border . At least theres no deluge in the offering and it will feel a bit more seasonal but any deep cold for the timebeing is out of reach.
    8 points
  19. At last GEM has ditched its outlier op runs and is more in line with last night's UKMO at D6: And flattens out afterwards: UKMO this morning: That northerly is very brief and rather underwhelming and that assumes it will not continue to be downgraded. This morning GFS op plays with the LP system at around D8 that develops as it interacts with the jet. I have been watching this for a few days in case it does cause mid-latitude disruption, however it has been rather anonymous till the GFS 0z op. Today it sends WAA on its back end and we develop a temporary Greenland ridge. Again it is too early to sustain due to the PV profile to its North: All well and good but the GEM at D10 still has that LP system in the W.Atlantic! The P has it innocuously roaming to the west of the UK and the pattern as in previous days remains flatter: The control pushes that low into the jet and simply reinvigorates it over the high, pumping up the UK MLH: The London ENS keep the 850s between -5 and +5, a sure sign of no cold spell developing, just alternating between TM and a PM flow. The op looks on its own synoptically: ECM at D6: As usually the case, ECM and GFS meet in the middle ground, not as flat as GFS but a lot less amplified than GEM and ECM. D7 onwards and the flow flattens as expected due to the PV energy flow to our north. At D9 ECM continues with the consistent modelling of the PV energy moving east and draining the Greenland lobe and with the Atlantic storm entering stage left this could help exploit the Atlantic ridge's propensity to build towards Greenland: Miss on this run: The ECM op height rises are nearly always the best case scenarios, feasible as the GFS op shows, but very reliant on all the pieces of the puzzle fitting together, so mainly unlikely. Early days to dismiss a D10 chart but the op, IMO would appear to be more in line with its mean when that arrives later. However very fine margins with that theory as timing issues will greatly effect the result as we have seen from the GFS different solutions. The trend at D10 for the PV movement is fluid but the mean suggests that there is a strong indication low heights are moving east and then back towards Greenland and it is this morning a more even flow: At D16 the PV is still mobile and mainly disorganised with no clear signal a lobe will set up in Greenland/NE Canada: So uncertainty as to the Atlantic storms introduction into the mix, but the GEFS after D10 although seasonal, don't suggest any blocking leading to a cold setup (apart from the unsupported op).
    8 points
  20. Well that is nonsense because the strat has just recorded record polar temperatures at 10hPa and a split lower vortex occurred - so the FI forecasts did reel in and verify. Also I know very well that the chart I posted is at the very extremity of FI but it was linked to my previous post and was demonstrating what I expected to see and in that respect was fit for purpose. Edit - I hope that cigarette was worth it LOL
    8 points
  21. I don't think we should be so quick to trash a northerly on w/c 8th December. The latest run was one of the mildest of the ensembles. Sorry if this has already been mentioned
    7 points
  22. Here's my winter forecast for 2014/15. BACKGROUND In putting this together, I considered 7 different factors, some looking at their current state and others at their projected state during winter. I then compared these with previous years back to 1967 (where the data goes back that far), gave the factors in each year a score based on it's similarity to this year, and then assigned a weighting for each factor.( I won't go describing what each of the factors is in detail, or the influence they have, as this has been done by several forecasts already this year.) Below shows the factors considered and the weighting. .................... FACTOR ................ ............ ...........WEIGHTING.......... .......... ................ REASON Eurasian October Snow Cover Growth........ ............4 .......................Closest to the SAI I could get, useful for winter AO Quasi Biennial Oscillation (QBO).............. ...............4 ............... ...... Important in determining the strength of the polar vortex and chance of SSWs Multivariate ENSO Index (MEI)............... ........ ........4 .......... ............ Can alter the jet stream, influence SSW risk and more Kara/Barents Sea Ice Concentration .......................2 ........... ........... Influences Arctic and Eurasian winter weather patterns, NAO N. Atlatic Sub Tropical Gyre SST Anomaly...............1.............. ......... Can influence the state of the winter NAO NE Pacific SST Anomaly Pattern ............. ...............1 .............. ........ May alter the jet stream as it transits North America October Pattern Index ...................... .......................2 ............. ......... Might be a strong predictor of winter AO and CET anomaly So for each of the factors above, their current state and state in previous years were compared, and a score given based on the weighting system. This data was added into a spread sheet and each year was given a percentage value based on it's similarity, across the factors listed, with this year. Then the years with a similarity of greater than 50% were used for further analysis, these years were 1968/69, 1970/71, 1972/73, 1979/80, 1986/87, 2002/03, 2003/04 and 2009/10. Further analysis was then carried out by creating composite maps, and analysing the CET and AO values. This formed the basis for the forecast. WINTER FORECAST 2014/15 Below is the DJF SLP composite map A very clear signal for higher pressure to our north, and lower pressure just to our south. This set up would indicate an increased likelihood of easterly sourced winds and below average temperatures across the winter as a whole. Here's a look at each winter month in more detail. DECEMBER A very weak signal over December, with a slight positive anomaly showing over Scandinavia. This would suggests a lot of uncertainty in December. December AO The average December AO over the composite years is -0.42, with two months above 0.5, three below -0.5 and three close to average. This is skewed slightly by the -3.4 value in December 2009. Overall, a weak -ve AO signal increases the chance of cold conditions very slighty. December CET Across the years used, the average December CET value 4.8C, or 0.2C above the 81-10 average. This consisted of 4 above average months, 2 average months (within 0.5C) and 2 below average months, ranging from 3.0C to 6.2C. Like the AO, there's not a strong signal, but very little chance of a significantly cold month with a CET below 3C. December Overall The composites suggest a +ve SLP anomaly over Scandinavia, but it may not be strong enough to exert a strong influence on our weather. The data seems to suggest that significantly above or below average conditions are unlikely during December as a whole. Overall, the chance of milder than average conditions is greater than cooler across the British Isles. JANUARY A very strong signal is evident for January. A very strong +ve SLP anomalies are present from eastern Greenland across to Scandinavia, with strong -ve anomalies to our south. A pattern like this would bring an increase in easterly winds, and likely cold conditions. January AO The AO averaged over the composite years is very low, at -1.44. This would indicate a strong likelihood of a disorganised polar vortex and cold plunges across the northern hemisphere. Of the composite years, only one had an AO above 0.5 in January, with two average and 5 below average, of which three were under -2. January CET The average January CET across the composite years was 3.6C, or 0.8C below the 81-10 average. This consisted of 2 above average months, 3 average and 3 below average, with a range from 0.8 to 5.5C. Overall, a moderate signal for a below average CET, and so below average conditions over the British Isles. January Overall The overall signal for January is for a disrupted polar vortex and a high likelihood of high latitude blocking. This increases the chances of significant cold outbreaks and a below average months overall. Given the composite anomaly map, with both strong +ve and -ve SLP anomalies close by, a slight shift could give wet or dry conditions, but given the increased risk of easterly winds, below average precipitation is favoured. FEBRUARY The blocking signal for February weakens slightly, but is still present. The shift in the highest anomalies towards Greenland suggests an increase in northerly orientated air streams over the British Isles with much less of a Scandi high. The overall pattern would, once again, bring an increased risk of below average temperatures. February AO The average February over the composite years is moderately low, and -0.94. This consists of one month above 0.5, two average and 5 below 0.5, of which one was below -2. This suggests an strong chance of a disorganised polar vortex (though not as much as January), with significant cold outbreaks and increased blocking across the northern hemisphere mid to high latitudes. February CET The average CET across the composite years is 3.9C, 0.5C below average. This consists of two more than 0.5C above average, 3 close to average and 3 more than 0.5C below average. A weak to moderate signal for a below average CET, and so below average conditions over the British Isles February Overall While not as strong as January, the overall signal for February is for a continuation of the disrupted polar vortex, but with a focus toward a -ve NAO rather than general northern blocking or a Scandi High. This increases the chances of below average temperatures across the British Isles. WINTER OVERALL It seems very likely that the AO will be -ve overall and that at least 1 month will have an AO of less than -1.5, most likely in January or February. Given the large shift from no clear pattern and weakly -ve AO values in December to strong blocking and very -ve AO values in January, a SSW event is likely to be the trigger that causes a shift from December into January. While there is little risk of a significantly cold December, there is a moderate chance of very cold conditions in January, and to a lesser extent in February. Precipitation is more likely to be below average in northern and western areas, especially in January and February, owing to the increase in easterly winds and northerly blocking To summarise, a mixed December with close to or mild temperatures overall, followed by a colder than average January to February producing a close to or slightly colder than average winter overall.
    7 points
  23. Yes, ECM has all but dropped it's several northerlies, so too has GEM and the models have very much moved into line. However, we have also lost the dreadful Biscay High charts Gfs was putting out a few days ago so we are left with very benign conditions with dry weather a few frosts and temperatures never far from normal. For early winter it could be worse and it many ways it's the ultimate blank canvas and anything could happen. Be thankful that you didn't book a late November break to the Canary Islands which are enduring repeated storms as cut off lows slide underneath the mid Atlantic High, in Lanzarote on Friday the capital Arrecife recorded 130mm of rain, for this near desert island that's about a years worth! Andy
    7 points
  24. Looking at the GEM control, it again does not support the D10 GEM op: Its mean is more in line with the GFS mean: The ECM mean does not marry with the GEM or GFS mean in that it sends energy through Siberia feeding the N. Pacific PV lobe, allowing the Greenland/NE Canada PV to drain. Completely different NH synoptics and important for D10+ for the UK NH quadrant: Bearing in mind GFS has proven better at the D8-10 pattern of late I slightly favour their outcome. Good call for the UKMO pros to go with the GFS over ECM a couple of days ago re the mid week ridge.
    7 points
  25. not sure why a commercial numerical weather prediction model, or its creators, would have a "marketing ploy" or "seek attention" by being inaccurate...
    7 points
  26. Evening all. So with winter a few days away it is worth looking where we are stratospherically and where we expected to be at this point. So far this stratospheric winter we have seen a completely different position to last year. Last yera we saw the stratosphere cool dramatically = there was some early wave activity, but his hardly interrupted the dramatic cooling seen especially during December. 2013/2014 fluxes Note the 1 10 and 30 hPa u wind totals leading into Dec - they were a lot higher and wave activity hardly had an impact but This year so far shows how the u winds have been dramatically affected by the wave activity. Every year we will see tropospheric wave activity affect the stratosphere - but the strength of this activity and susceptibility of the strat differs from year to year. This year we are seeing an extremely susceptible strat vortex as expected. To get a better idea it is worth looking at the Merra data and look at the mean temperature at 10 hPA It is as high as it has ever been recorded in November and it is no surprise to see the mean zonal winds follow suit. Well below average for November. So it is no surprise to see a the stratosphere cool down and try and returm to some sort of barotropic normality over the next few weeks. But I don't think that we should consider that this is a bad omen for the rest of winter. a period of increased zonal winds is always seen prior to bigger events - look at 2012/13 u winds For me this winter is behaving exactly as expected so far - with perhaps better wave activity that we could have envisaged. And what do I expect from now? It has been great to get the winter forecast out of the way because we can concentrate on the tropospheric and stratospheric forecasts. Well I am know on the lookout for wave 1 activity followed by wave 2 activity rebounding into the stratosphere. The tropospheric forecast pattern is not quite set up for this yet - the MJO phase and presure anomalies to create favourable mountain torques will take a couple of weeks to align, but I am liking the progression of these forecasts so I don't think that we will have to wait too long and the phase 7 will be a good SSW precurser.. http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml So keep an eye on the 1hPa forecasts because I believe that you will see the first clues exhibited on the extremities of the vortex here.... But in the meantine the troposphere should still be favourable for an increasing cooler pattern in the meantme.
    7 points
  27. Enjoy the frosty nights this week..better than mild mush. It's only grim for those who want yet more..yawn.. unseasonable warmth. :-)
    6 points
  28. There are a few off topic and one-liner posts creeping into the discussion.........I'm not going to remove them as we're approaching the season of goodwill and all that stuff.......(actually, I'm just very lazy) but if you can bare it in mind, it'll be much appreciated........cheers
    6 points
  29. I can promise knocker that most breezes in the next two weeks will feel cold! Still think Decent amplification will appear week 2 somewhere between the east coast of America and w Russia. Exactly where remains the question. If it doesn't, then the alternative is probably a sinking upper trough which would be cold and unsettled.
    6 points
  30. The atlantic low which has now transferred to the western Med is drawing up some exceptionally warm air from Africa with 28 C at Palermo in Sicily at midnight. Some of the warm air is filtering into parts of mainly southern europe. The low is modelled to expand NE wards over the next few days and is expected to back the flow over southern UK drawing in colder air form further east. At the same time the atlantic ridge is modelled to extend across the middle of the UK. An increasingly cold week looks likely for much of the UK as the warm air currently over the UK is gradually replaced by a feed of colder low level drier air from northern Europe. http://meteocentre.com/analyses/map.php?lang=en&map=eur_full&area=eur&size=large http://www.wetterzentrale.de/pics/brack2a.gif
    6 points
  31. Just to clarify now that i am able to post charts. UKMO nice early winter chart http://www.meteociel.fr/modeles/ukmo2.php?nh=1&ech=144&carte=1021 vortex shifting west to east. GFS Has the vortex correcting eastward too and i feel the ukmo will follow something similar. http://modeles.meteociel.fr/modeles/gfs/runs/2014113000/gfsnh-0-192.png?0 ECM Polar Vortex as of today http://www.meteociel.fr/modeles/ecmwf/runs/2014113000/ECH1-0.GIF?30-12 And by the end of the run http://www.meteociel.fr/modeles/ecmwf/runs/2014113000/ECH1-240.GIF?30-12 GEM http://modeles.meteociel.fr/modeles/gem/runs/2014113000/gemnh-0-240.png?00 All variations of a theme that will reap rewards later.One thing is for sure,there will be no repeat of the vortex machine that set up way to our N/W and bombarded us with maritime misery.This year could well be the polar opposite.
    6 points
  32. Tonights model headlines sponsored by the Star Wars Trilogy appreciation society and not those dismal prequels! The ECM after being lauded by NCEP for the last few days has decided it wants to join the dark side Darth Vader, however its not quite as dark as the Emperor GFS and GFS P. The UKMO alias Luke Skywalker with amplified light sabre stands in their way, the GEM alias Princess Leia including dodgy hairstyle is ready to join the fight. The JMA that dodgy bloke from the Empire Strikes Back who betrays Han Solo but then decides it wants to develop pressure towards Scandi. The ECM may yet see the error of its ways as the polar region is more like the UKMO than the GFS, so we may yet get to the scene in Return of the Jedi where Darth Vader tries to make amends to Luke. At T240hrs the ECM indeed has made a good try at making amends but no one believes Darth after his less than stellar recent efforts!
    6 points
  33. I have to agree with you. Theres no sign of any deep cold being able to head sufficiently south and PM air really doesn't cut it unless you're high up, the models especially the GEFS tend to overplay the southwards extent of cold upper air at longer range. This is especially when this cold advection is not in connection with HLB, the pattern over the USA is expected to be flat zonal for at least the next ten days, in terms of positives from the output at least the Azores high is expected to remain displaced to the west and the PV although reforming to the north is then expected to break up so in that sense it doesn't at this stage look like a repeat of last Decembers mildfest. At this point looking at the overall set up if the high remains displaced to the west and the jet tracks se into the UK then that may eventually develop some interest if the upstream pattern improves. The output's not the worst I've seen but just a bit underwhelming. At least there will be a cool down into the start of December and mainly dry for the next week so its not all bad.
    5 points
  34. The GEFS T240 anomaly. Some upstream amplification, trough Pole/Greenland and swathe of HP eastern seaboard through to eastern Europe. The jet basically funneled between the two Atlantic systems Upshot of this on the surface is not much change in the overall picture with LP Iceland area and HP below. Temps a little below average. Moving on into the future the main indication is that the Pole/Greenland trough will move east and south and possibly disrupting the HP to the south and could introduce an easterly. Oh. Charts weatherbell (for those that can read them)
    5 points
  35. Sorry AJ and coming from a moderator, I wouldn't setting a good example but all I can say is OMG! In fact I'll attach a chart for folks for good measure, this will NOT verify as shown but Christmas would have come early if it even went close for those who like a wintry bite to their winter weather. Off to watch the darts now, goodbye all and behave for AJ. *the chart actually looks better than it what would be produced by it in reality, but who cares* December 1st tomorrow, here we come.*
    5 points
  36. I only really remember the date of snow because of naming my piccys as Nov-10 snow. Came as a bit of a surprise, if I'm not mistaken.
    5 points
  37. Good afternoon on the last day of Autumn , fellow posters .generally all output today points to a fairly quiet spell of weather ,Ok it will be turning Cooler as we go through this week with some frosts Fog perhaps some wintryness over fairly high elevations and a promise of some sunny early winter sunshine .but as we approach the later stages of next weekend and early the following week Alot of uncertainty in my opinion .some Data pointing towards an attack from the north /west others saying pressure will be high from azores to europe .But remember last December ,Mother nature was cooking up some pretty spectacular weather .looking at current Vortex modelling and it seems to have very itchy feet but will probably find a place to Roost but Destination currently [unknown ] .as many experienced posters have pointed out keep an eye on model runs over several days as apposed to just One run ,REmember all data whether surface maps upper air maps including Jet stream vortex etc will change constantly ,this model forum i find a very interesting learning area .For new members and those who want to learn more about Meteorology especially those who want to understand upper air patterns and what is actually taking place a couple of miles above our heads could fin d the study of Aircraft contrails a good Tool for visually studying the upper air along with of course natural clouds .If you type in Science of contrails on Google ,there are many interesting sites .I,v mentioned this on Model output discussion as i know some posters are new and learning .well 13 weeks of winter about to start ,182 ecm runs 364 GFS runs ,not forgetting the others of course ,Cheers gang
    5 points
  38. Can't really argue with those weightings BFTV. Good luck. With so many forecasts suggesting the same it'll probably be the warmest winter on record!!!
    5 points
  39. Thank you for all the hard work hat went into that BFTV, interesting that you and others tend to favour below rather than above average temperatures overall this winter. Even more so when the model data from weather centres suggests the opposite. It is going to be an interesting 3 month period as we see how this plays out. thanks again,
    5 points
  40. I think your charts are from a pay website so cannot be linked as the animation - FIM is free to view and here's the same parameter in animation format. http://fim.noaa.gov/FIM/jsloopLocalDiskDateDomainZip.cgi?dsKeys=fim_jet:&runTime=2014113000&plotName=ptemp_pv2&fcstInc=360&numFcsts=57&model=fim&ptitle=Experimental%20FIM%20Model%20Fields&maxFcstLen=336&fcstStrLen=-1&resizePlot=1&domain=201 Full menu. http://fim.noaa.gov/FIM/Welcome.cgi?dsKey=fim_jet&domain=201&run_time=30+Nov+2014+-+00Z
    5 points
  41. Great post, written with the maturity and knowledge I could only dream of having !! To my untrained and very much bedroom enthusiast eye, Looking further ahead (which always going to be about looking for trends ??), IMO that there really doesn't seem to be one and when there's a lack of trend in the models it tells me that a half way house between what is being shown is the most likely outcome. To that end I wouldn't be surprised if after this week, we see a continuation of the UK being stuck between High pressure to the West, and High pressure to the East with Low pressure squeezing between the gaps. Something a bit like what peturbation 12 is showing As you say though anything is plausible I just wanted to find some way of saying that your post was awesome other than putting some one liner that would be deleted :-)
    5 points
  42. A glance at the GEFS and ECM anomalies this morning. Broad agreement at T168 with troughs Canada - Greenland - Russia. HP Siberia/Pole and a swathe of HP America to Europe. Surface analysis much the same as now with HP dominating the Atlantic and LP relegated to the north centred around Iceland. At T240 the similarities take a parting of the ways. Amplification upstream and the Canadian trough now aligned south from the pole down the eastern seaboard with a branch line just west of Norway. HP eastern Atlantic and eastern Europe. The ECM has the HP America to mid Atlantic but the Canadian trough spreads east with branches to Russia and south through the UK into N. Africa, HP over the Pole. Having said all that the surface analysis is still the domination of the HP in the eastern Atlantic. For the life of me I can't see where the next cold breeze is coming from. I'm quite concerned. Charts courtesy weatherbell Apologies the charts loaded willy nilly, as they say.
    5 points
  43. Following on from what the Captain said, let's keep this thread friendly please. We don't want to have to put some of you in the naughty chair... Just a quick summary of some of the models, but it looks as though some kind of cold Polar Maritime blast looks possible very late next week and into the weekend, maybe with a chance of something wintry for some. Whether it will be a cool/cold blast from the North-West, or from the North, would still depend how much amplification that can be achieved to the West of the UK. Some models like the ECMWF, though, generally keeps the UK locked into a flattish Westerly flow, but with another Polar Maritime shot right at the end. The operational GFS, for example, has a Low dropping to our South-East in fairly deep FI pulling in a chilly flow from the East/North-East with heights building to the North and North-West. The blocking High slowly gets knocked down to become a Mid Latitude Blocking high to our West. But still with the Atlantic quite blocked and Lows getting steered well to our North. The GFS Parallel bears similar ideas to the ECMWF beyond next weekend with a general Westerly or South-Westerly flow for the UK with spells of rain or showers at times, especially for the North - perhaps wintry at times over the Northern hills during the moor cooler Westerly interludes. Does briefly go for a High Pressure system taking a seat over the UK in quite deep FI, but gets knocked off its seat rather quickly. The GEM looks as though it is gearing up to provide is with a Northerly at 240 hours with High Pressure significantly amplifying behind a trough of Low Pressure trying to swing down towards the UK. Before then, the models continue to show High Pressure building through the UK from the West next week, with varying brighter and cloudier periods. Could feel quite chilly, especially at night-time with some quite sharp frosts possible. A cold front will also slip through the country tomorrow bringing some rain to places.
    5 points
  44. Having flicked through the output and read a couple of posts I have come to the conclusion that the week ahead is getting steadily colder.UKMO at 144 says cold that's as far as it goes.ECM cold run.Gfs also cold.Welcome winter.Most of the charts have been posted above and how some find fault at this early juncture is open to debate.
    5 points
  45. Bringeth it Oneth 00z Tuesday potential albeit altitude at 1800ft. Then 5th to the 7th at the far end of reliable (+144?) but this has been trending on quite a few runs - we will as ever see. (Back home visiting relatives in Cumbria on 7th so the sledge will be in the boot.) Happy Advent Sunday everyone. Ian
    5 points
  46. Don't understand the negativity on here tonight, ECM looks very good too me. Polar Vortex moving East away from Greenland, ridging towards Greenland from the Atlantic. If day 10 verified we would be in a brilliant position.
    5 points
  47. Hey.....I've got a great idea! Why don't we create a thread where we can actually discuss the current model output?.......what a novel concept! ....yes, you've guessed it, several posts are about to be binned for being off topic and rather personal
    5 points
  48. I always wonder when I see this type of response at what timescale you think that we should stop trying to predict the weather for - because you must have one in mind. Is it 3 days, 5 days, a week, 10 days? Where do you think we should draw the line? I think that we should always be trying to push the boundaries as Pete suggests to further the science. After all, 30 years ago a forecast for 5 days out was considered to be long range! And as for the metoffice - I think that you will find that they do bother - they just aren't made public, perhaps wisely so.
    5 points
  49. I think the issue is more that we don't remember the runs which aren't cold in fi. I promise you there are far more of those!
    4 points
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