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Showing content with the highest reputation on 02/12/14 in all areas

  1. 67 points
    Good morning all, Following on from OldMetMan's comments regarding the NWS discussion, i'd like to add some further information. I'll try and keep this as simple as possible. Firstly though, the current weather situation we have here in the United Kingdom, or "reliable timeframe" as it's commonly known as. This week, Monday to Thursday is looking rather benign, dry, some sunshine and feeling chilly, especially at night time, where frosts may accumilate in favourable places. We can see this from the following charts: (I'll be using the GFS to illustrate in the reliable time frame, as most models agree unanimously) Tuesday Wednesday Thursday So, we can see from the above charts (MAX Temperatures) that it will feel rather chilly, especially after the mild(ish) weather we have been accustomed to as of late. The 500-1000hPa charts are of good use, these measure how warm, or how cold a layer is in the atmosphere. Thickness charts are a good way to measure the probability of snow, or other prospects like warm/cold air. The change is coming in from our North West of the United Kingdom, and we can see by Thursday night. We can see on the T850 chart, which measures the upper air temperature's and becomes instrumental to what we recieve on the ground, so to speak. It's also another good tool to use for deciding if you will get snow or not, and the general rule is: (Maritime flow) Sea Level: -7c 150m: -6c 300m: -5c 450m: -4c 600m: -3c I say "General Rule" as it can be different depending on what else is happening weather wise. So, anyways, we can see from the following thickness chart on Friday there is potential for snow, albeit mainly at elevated levels. The above chart is the 500-1000hPa. What we are looking for here is the "528 DAM Line" or 528 Dacameters. We want this to be as south as possible if you are looking for cold/snow. The 850's are showing at -5C. Using the rule we learnt earlier, places above 300-400m could see some snow. We can see from the Snow Risk chart below as the front pushes in, NW Scotland and higher ground 400m + is ideal for snowfall. After this time frame, we are really getting into the unreliable time frame, but it's always nice to check what the charts are showing within the reliable timeframe, as people tend to get carried away with silly posts like: "No cold for the next 4 weeks" "No mild weather for the next 4 weeks" "No snow in December" "Charts are crap" Etc etc, you get my point. If anyone can tell you with 100% confidence what the weather will be like in 4 weeks time, then they should be working for NASA/UK Met and running the company. Oh, and placing lottery numbers too. As I mentioned at the start of the post to go on from what OldMetMan was talking about, we can see as per comment from NWS: We can see where the Jet is at the moment in Mexico which attributes to the post above, it usually isn't their at the moment. Maybe this does mean a large pattern distruption, I am not sure, but will have a good look at the charts and data available to us and decide from there. If we look at the forecast for the Jet we can see it remains very strong for 14/12 But after this is where the NWS discussion and what OldMetMan was talking about might change, around the 17th as we see a strong surge from the Jet over Mexico at 180 hours. Which looks on course for Central USA & should start to impact upstream around the 17th. Remembering the Jet Stream from earlier, and how powerful it was, we can see around the time of impact C.USA we have a slack Jet coming from Canada and southerly digging: I am unsure if this is related, but will post again when I have done some research. Another thing to keep an eye out on is the potential storm, at the moment it's hitting Scotland, and Western Isles, but needs an eye kept on to track and see how it unfolds, but that's for another post, maybe. Regards, Dr. Astro
  2. 52 points
    Some interesting remarks spotted this morning in the NWS forecast discussion. It's not exactly clear to me what the implications are for the circulation pattern here, but it looks significant: "...AND WHAT IS BECOMING MORE EVIDENT...IS THE LATITUDE FOR THE WAVE TRAIN MIGRATION. TO ME---IT'S DISPLACED SOUTH OF A 'TYPICAL' LATE-AUTUMN LATITUDE---CLOSER TO 40N-42N THAN 47N-48N ALONG 140W LONGITUDE. IF THE ECENS MEAN IS ANY INDICATION OF WHAT CAN BE EXPECTED...ITS 1/12Z DETERMINISTIC RUN AND 250MB JET FORECAST SHOULD BE NOTED FROM THE SOUTH COAST OF JAPAN TO 40N 140W BY THE END OF DAY 7. A SECOND FEATURE OF THE PACIFIC---IS THE EARLY EMERGENCE OF THE SUBTROPICAL JET...AND ACTIVE OVER NORTHERN MEXICO SO EARLY IN THE LOW-SUN HALF OF THE YEAR. THIS IS USUALLY MORE A LATE JANUARY THROUGH FEBRUARY OBSERVANCE. AND WITH THE DETERMINISTIC GUIDANCE SUGGESTING NOTABLE INCREASES IN THE PACIFIC BRANCH OF A JET NEAR 25N...IN CLOSE PROXIMITY TO HAWAI'I NORTHEASTWARD INTO NORTHERN MEXICO BY THE END OF DAY 7...AM THINKING THIS MEDIUM RANGE FORECAST PERIOD IS TRYING TO TELL US SOMETHING---AND PERHAPS THE PATTERN IS CHANGING IN EARNEST...WITH THE DOWNSTREAM EJECTION OF THE CLOSED LOW OFF THE CALIFORNIA COAST SETTING THINGS INTO MOTION." I mentioned the unusual appearance of what seems to be some sort of sub-tropical feature by the GFS for this coming weekend, and with each run, the GFS has maintained the formation of this significant feature but has changed it's development. The latest run shows it becoming a major storm system next week. There has been a great deal of change within the longer term trends of the model output, even more than usual it seems to me and I can't shake the feeling that something important is going to happen within the next couple of weeks. What NWS are saying about the sub-tropical jet suggests to me a weakening of the northern stream, and subsequent reduction of zonal activity at our latitude. Others more knowledgeable about such things are welcome to comment. The model output is, in my view, even more unreliable in the longer term than is usually the case and I am struggling to see any consistent trend emerging from recent runs of all the major outputs. The storm system I mentioned above, well the projected development just looks plain wrong to me. As I mentioned in my last post, it looks more likely to introduce a greater amplification to the flow upstream and may be what the NWS is getting at. For now, things look pretty "normal" but by the end of the week, I suggest we may see the first signs of a major pattern disruption and change towards a colder and more blocked one. I shall have to mull this over in the coming days and come up with a less vague prediction than this! But I will say that when it comes to cold and snow, be careful what you wish for....!
  3. 45 points
    Things are still looking better than last year for snow, I know not perfect yet for coldies but if you compare it to thing time last year its a major improvement Thursday evening sees the potential for some wintry weather over high ground for a few parts Into early Friday and the snow starts to become more widespread in northern Scotland, still some wintry weather for higher parts in the rest of the UK So how are we doing for snow depths at this stage? well not a great deal to start with some a few cm max Now we fast forward to Midnight Saturday night and the next snow on show This event looks more prolonged for parts of Scotland but how will the snow depth fair..... ....well by 19:00 on Sunday the snow is starting to increase with 2 to 3 inches in places (7cm to 9cm in old money) Now lets continue to look at the snow depth we'll fast forward 24hrs to 19:00 on Dec 9th The snow in western Scotland is starting to pile up now with 3 to 7 inches (7cm to 18cm) notice also parts of western England, Wales and Ireland beginning to see some snow an inch or so for high ground in the Lakes What will the next 24 hours bring? well lets have a look we are now at 19:00 on Dec 10th So the snow continues to fall in Western Scotland but even the east gets a dusting totals also begin to increase for parts of England maybe even a dusting for Dartmoor. Higher parts of Herefordshire and Worcestershire could see around 2 inches but even lowers parts could see a dusting of snow And now the final 24 hours to 19:00 on Dec 11th As we can see a lot parts of the UK see a dusting of snow maybe even something in London. North western Scotland sees the snow continuing to build with some parts getting close to 10 inches and 3 to 5 inches widely. Over in eastern Scotland the amounts are also increasing with 2 to 3 inches for some parts So after all that things are looking good after today's 12z from GFS / GFS P with some snow possible for large parts of the UK by mid next week but without doubt the place to be in North west Scotland based on this run totals could really be mounting up for the higher levels. Fingers crossed for a snowy spell of weather to develop
  4. 41 points
    Tamara תָּמָר, on 22 Nov 2014 - 14:30, said: A much more coherent MJO signal emerging from the Central and Eastern Pacific would serve to heighten a more widespread El Nino response which in turn would assist further the -AO feedbacks in maximising that potential towards an SSW. Could it be that the longer term modelling is starting to sniff out those needed changes as above and showing how the stalemate eventually resolves itself with weightings towards our east rather than the atlantic? ie. the Aleutian low and better aligned Siberian High signature that leads to a pot of gold? The long term ensembles are tentatively suggested this in the 2 week and beyond period. No surprise to see the Canadian lobe weaken and Siberian sector become dominant on these suggestions Timing open to debate, but still greater things might be apparent in both tropospheric modelling and ammunition fuelled stratospheric modelling by this time. ---------------------------------------------------------------------------------------- A very important junction being reached in December modelling in terms of timing implications for longer term expectations and developments. My own posts, and various others who have been considering the December/ and further winter pattern have persistently referred to the background drivers expected to be of major significance. These have, as expected, and previously documented, already impacted the autumn into winter feedbacks and imprinted significantly the potential for -AO driven weather patterns over the UK and Europe. These drivers still require a forcing mechamism to release that potential. The 'template' for the season can be developed to a point, but a catalyst is required to complete the circle so that ocean vs atmosphere coupling ensures this potential becomes actuality. The atmosphere is trying to develop further El Nino tendencies begun in the ocean. The junction I referred to at the start of this post is that the ocean > coupling relationship is stalling at a time when the optimistic end of predictions were hoping to see something smoother and more seamless to lead to before end of year cold. A smoother evolution of the patterns has been quite credible. It is also true to say as well though that theories often create ideologies, however scientifically studied and well based they may be, and these ideologies are always going to be prone to setbacks and unforeseen developments. Much has been spoken on this thread and elsewhere about a disconnect between what seasonal models predict and what background drivers suggest. This apparent discrepancy brings us back to the ocean > atmosphere coupling and the issues that are (presently) putting on hold any progression to that properly colder winter pattern. The forcing mechanism we are speaking about is of course the MJO - in addition to conflicting signals wrt Hadley cell behaviour in the tropics which are behind the flatter atlantic pattern we are seeing in the models and frustrating, thus far, the amplification that would be the mechanism to resume wave activity on the stratosphere and continue the theme of backing the winter pattern west from Siberia. At the time I made that last post of mine on 22 Nov, in relation to the subject matter highlighted there, I enquired to the METO about the disconnect of seasonal models and background drivers and asked them to state what the 'other factors' were they referred to in their seasonal forecast which point to a +NAO above average season - and conflict many of the well laid out expectations written elsewhere, not least those from the official forecast on this website as well as many other members with similar thoughts. In keeping this strictly on topic, I won't copy all their comments about anthropromorphic forcings they discuss - but will copy the relevant part of the 'other factors' related to the +NAO. I've omitted names and references working at the METO to avoid upsetting any possible confidentiality protocols Dear Tamara, In making the forecast there are a number of factors to be taken into consideration: the current observations, known forcing factors and, importantly, several dynamical forecast models. <For this forecast (DJF 2014/15, issued 20th November 2014) there is good agreement across these models for enhanced likelihood for the positive phase of the North Atlantic Oscillation (NAO), cyclonic westerly circulation and warmer conditions for northern Europe. In addition, models have shown a very consistent signal for early winter in this respect for the past few weeks> The model physics is able to represent all the drivers that you discuss in your email, and in preparing the forecast we consider these in detail. Some caution is required in interpreting historical statistical relationships based on short observational records, as these relationships may change with both natural decadal fluctuations and through long term climate change. The models do include increasing levels of greenhouse gases, but the mean change in NAO that we see in the forecast is much larger than could be expected as a result of anthropogenic forcing on this timescale. Initial analysis of the forecast from our system suggests that the positive NAO signal may, at least in part, be driven by teleconnections from the tropics; the forecast shows anomalously high rainfall in the far west Pacific, associated with warmer than average sea surface temperatures in that region. In particular, there is a clear wave train in the upper level troposphere emanating from the tropical Atlantic and supporting the positive NAO. Understanding the drivers for predictability is an important part of the forecast process, although it’s useful to bear in mind that they may not act together in a simple linear manner. Dynamical models are the best method we have for studying the interactions between the different drivers and there is a continual program for the development and improvement of these models. I hope that this information is useful and fully answers your questions. Kind regards, Climate Science Enquiries Coordinator, Met Office The relevance of the bolded part is what seems to represent the clear expectations from G5 and other seasonal models that MJO cycling, certainly the present cycle, is going to be resistant to arriving at the eastern progression of phases 8/1 that we require to amplify the pattern and kick start the process of further strong wave activity in the Greenland area to dislodge the Canadian/Greenland vortex and complete the energy transport process I have spoken about recently into Siberia. The bulk of the vortex into Siberia has held obvious further consequences for assisting Siberian High cold pooling feedbacks and advecting cold air much closer to our latitudes as we head through December towards years end and the start of the new year. Such evolution, courtesy of progression through Phase 7 toward 8 would be regarded as fine priming for SSW activity to follow. My own thoughts had been thinking along the lines of our first salvo comeing form the north and post this important atlantic amplification sequence - a whole raft of trop/strat wave activity following to 'finish off' the work begun on the vortex in recent weeks. Clearly the present lull inactivity due to the lack of upstream Pacific trigger and also the consequences of unfavourable Asian vorticity placement being manifested in recent poor orientation of heights to the NE and the strong progress of Siberian High development being interrupted, is showing itself in a more organised vortex (still much weaker in relative terms however obviously than last year). The MJO modelling still presents a stand-off ( much as Tony (Lorenzo) said in that excellent post at the weekend). ECM continues to suggest loss of amplitude and stalling phases 6/7 - and this does tie in at least with the early suggestions from the METO of the convective wave activity remaining rooted in the western Pacific. GFS forecasts have been bullish of good progress through the Pacific - but questions are to be asked as to who is right. ECM MJO forecasts allude well to the METO stance with the predictions of the wave losing amplititude - dying through P7 ( into the "circle of death") and re-emerging to head back again towards the Western Pacific. Assuming for a moment the current ECM forecasts verify similar to this ( METO seasonal scenario) then without the WWB (westerly wind bursts in association with the tropical convective forcing) sending the warmer than average waters in the western Pacific eastwards sufficiently to sustain El Nino tendencies in the eastern Pacific, then rossby wave activity as a result of WWB eastward progress is also subdued. This has implications for timing and arrival of any SSW event - especially as many thoughts, including mine, have been geared towards year end. In conclusion the models are a fair representation right now - with the lack of upstream amplification frustrating hopes for arctic cold and snow wishes. That is, not withstanding of course any short term transitional toppler developments which possibly hold some interest for a time for some northern areas in the coming days We should bear in mind though, that great uncertainties are attached to upstream Pacific forecasts as much as any other forecast. At least though we have a handle as to where the flies in the ointment lie. The METO allude to present Pacific patterns in terms of early winter - as I highlighted in the copied e-mail. Expectations have always been geared towards the last third of December and years end as the earliest time for any widespread and meaningful snow and cold wishes. Its best that at this time we simply view the situation in temporary terms (regarding cold hearted mid winter hopes which are still very much alive) even if reality looks to be removing any previously realistic hopes of significant seasonal festive cold.
  5. 38 points
    Is this the new parallel version of Summer Sun?
  6. 29 points
    Not surprised by Ian's update. I struggle to see where significant amplification is going to come from to lead to a cold spell / pattern change in the next 10-14 days. It certainly looks like a pretty unsettled spell is on the way in one form or another, could at least be PM sourced unsettled weather and the Scottish mountains could at least get hammered in time for Xmas! Interesting to see that for the 2nd run in a row the GFS (p) handles that tropical depression differently to most of the other output, not phasing it with the vortex but running it zonally underneath and straight into the North of the UK, one to watch. I have just read through the MET winter forecast paper. All a bit jumbled and messy and there was nothing in there most people on here didn't know but after 50 odd pages though, this summed it up... "positive NAO for DJF 2014/15, not clear which driver may be responsible for this response in models; most drivers which are in an active phase would typically favour the opposite" So it is a simple case of a computer model going against the collective primary driver states/forecasts? Interesting that even the OPI team were scratching their heads a bit that one of their models went completely against the low OPI/ high SAI forecast. Cohen himself has indicated recently hinted feedback response not as expected possibly due to anomalous low pressure system in NW Asia. December will be interesting in that respect at least. To my mind the holy grail of medium-long term forecats is knowing the primary drivers, forecasting how active (their atmospheric coupling, downstream response) and most importantly their interaction with each other. i.e.why does i.e. the MJO override the ENSO signal in one instance whilst not in another. In fact, that would be pretty straghtforward in itself but throw in a dozen+ drivers and I can't see how a 96M supercomputer can come close to resolving that little puzzle!
  7. 19 points
    Those who say its bleak this or dire that or even run of the mill are wrong in my opinion, we now have polar maritime incursions on the way for the first time and with patience which some clearly don't have..the deeper cold will come. If the models were showing a sw/ne jet profile with long draw south westerly mush I would agree it's dire or bleak or whatever but it's clearly not the case.
  8. 19 points
    How wonderful to see both questions from hocus pocus and Tamara answered so comprehensively from the Met Office. Wouldn't it be lovely for one of the scientists to drop in here occasionaly and offer these insights. (Hint hint if you ever read this!)
  9. 18 points
    Remember the GFS's penchant for over Atlantic....
  10. 15 points
    Welcome Dr Astro, just about the best and most informative first post I have ever seen.
  11. 15 points
    Yeah, I do think the whole 'no snow in the next fortnight unless you stand on top of Ben Nevis' type analysis is a bit over the top given we're looking at this in three days time: While there may not be much precipitation around (as is more the problem with today's 'northerly', as the DP here is sub 0C) the temperature profile still looks pretty conducive to snow: That's before we consider Sunday, when precipitation looks to be more abundant: Of course the upper air temperatures may well moderate a bit as we get closer to the time, but it's not that rare to see Polar-sourced northwesterlies deliver - early December 2011 delivered some notable snowfalls for central Scotland with upper air temperatures around -6C:
  12. 13 points
    Indeed, have now corrected as you rather mildly suggested. Only if you keep looking for it.
  13. 13 points
    GFS 12z FI looks a lot better with wave activity starting to pick up once again with the vortex being stretched. Easterly incoming last few frames with some WAA right into the Arctic. We need to see more of this over the next week or so!
  14. 13 points
    Worth a look in detail at where we sit with previous syntheses and very latest (Nov) seasonal analysis: http://medcof.aemet.es/Medcof/events/medcof3/docMedcof3/presentaciones/MedCOF3_Brookshaw.pdf
  15. 11 points
    A couple of posts have been moved into banter/ramps.. Please could we try and keep the kind of 'if it's not snowing in my garden then the whole of the UK might as well be in a heatwave' type comments in there? Ta!
  16. 11 points
    Models don't look run of the mill to me, there is a very disturbed and rather cold pattern evolving with hardly any tropical maritime to be seen and a good deal of polar Maritimes I'm happy to say..bring on the wintry showers..I think there will be a fair amount of snow on northern hills at times this month and occasionally to lower ground.
  17. 9 points
    The positioning of the PV has never really concerned me when ever we have the Aleutian low/scandi/russian high scenario. During the Slow burning winters,which many will not remember,the above were common place. Lets face it if this chart was out now the Bartlett brigade would be weeing and the raging PV brigade s.o.s- ing Nick Sussex.So a typical example of a slow burning winter here: http://modeles.meteociel.fr/modeles/reana/1977/archivesnh-1977-12-15-0-0.png however notice the Aleutian low. So lets move it on to New year... http://modeles.meteociel.fr/modeles/reana/1978/archivesnh-1978-1-7-0-0.png Not many left on the thread by this time the slow burner still on and a raging PV. BUT the Aleutian low still everpresent with heights to our n/e http://modeles.meteociel.fr/modeles/reana/1978/archivesnh-1978-1-7-0-0.png Wave breaking events were probably taking place throughout December as they are at present because of this combination which ultimately leads to this dramatic pattern change and Winter starting. http://modeles.meteociel.fr/modeles/reana/1978/archivesnh-1978-1-12-0-0.png we went from this Northern Hemispheric pattern to this http://modeles.meteociel.fr/modeles/reana/1978/archivesnh-1978-1-27-0-0.png and then by mid Feb Bingo....http://modeles.meteociel.fr/modeles/reana/1978/archivesnh-1978-2-19-0-0.png http://modeles.meteociel.fr/modeles/reana/1978/archives-1978-2-19-0-2.png That is just an example but 78/79 winter evolved with the Aleutian low in situ as did 86/87 and did i mention 46/47 in fact all of our classic slow burner winters had the same combination. NCEP archives well worth a peek.There was always pain before gain but i did not have access to all these charts so patience was not an issue. EDIT:Super post Tamara puts mine to shame
  18. 9 points
    It's not run of the mill at all, run of the mill would be a sw / ne aligned jet with endless mild mush. What we have is frequent incursions of colder air from polar regions mixed with somewhat milder atlantic airmass, in that overall mix we will have wintry showers, night frosts and yes..some milder wet and windy spells but after such a ridiculously warm autumn..I would not call this run of the mill!
  19. 8 points
    While some snow could at lower levels cannot be ruled out, I'm not sure how you can suggest a good snow event at ground level from that chart? Whilst 850's may support snow, other factors need to be added in. One factor would be the 0C isotherm heights- Here's the chart from the same run and the same time. Typically, some transient snow (possibly heavy for a time) 200-500m, in heavier showers/bands of precipitation, the isotherm can be dragged down to allow snow to fall at lower levels. This experimental chart gives the sort of idea in what sort of heights/areas would see accumulations It's all speculative this far out of course, and I'm not an expert but it's wise not to expect a "good snow event at ground level" from the type of chart you posted. It'll be fun watching some of those webcams on the Scottish mountains though!
  20. 8 points
    Worth reading everyone to find out what Met use, throws a spanner in the ideas of some who suggest various things mentioned ie SAI they do not use. Also worth noting some of the results of scientific research rather than hope. Not nice for cold lovers but interesting results. Again a number will not like their assessment of no clear signal, that is what it shows so that is what has to be said. Interesting that they suggest an SSW late on. yes do read it-not what most coldies want with their cornflakes this morning but do read it. also worth a read is that from S4Lancia a bit back on this page=post 101
  21. 8 points
    Hello hello hello. Evenin' all. This chap, once of this parish, reckons it's beginning to look a bit like winter. So, time to dust off the almanacs, take out the crystal ball and maybe even lightly oil the sledge. As Ned Stark would say, winter is coming. OK so the 12z GFS isn't a Buffalo lake effect blizzard, but there are some tasty upper temps showing at almost all stages of the run. The evolution near the end, whilst FI, looks plausible. It will be interesting to see if that accelerates forward as I suspect it might. In other news: how is everyone?!
  22. 7 points
    There seems to be a chance of a potential storm arriving at the start of next week. At the moment the models are still unsure of the track it will take and each of them have shown us what may happen so I'm going to go through each one, Tracks North The ECM seems very keen and has consistently shown it to head in a Northerly direction. It makes it's way to the South of Greenland on Monday and deepens rapidly down to 960mb. On Tuesday the storm then moves South East and sits over the North of Scotland bringing plenty of unsettled weather across most of the UK and Ireland, Strong North Westerly winds affect Western parts especially over Ireland where gusts are shown to reach around 65 to 75mph, The GFS earlier agreed with this route but has recently changed for a more North Easterly path. The UKMO looks similar to the ECM along with the JMA model so there is at the moment a good chance it could take this route. Tracks North East Both the GFS Parallel and NAVGEM from earlier today demonstrated that if it takes this route it could turn into a serious storm for the Northern half of the country. This morning on the 06z GFS parallel it showed the low deepen down to 940mb and bringing very high mean wind speeds along with gusts over 90mph for the North. But as the GEM shows tracking North East doesn't mean a huge storm it all depends on the positioning of the jet stream something the models will handle better when it gets closer. But even the GEM shows a deep low to the North eventually forming although nothing as severe the GFS Parallel showed us. Tracks East The 18z GFS which has just recently come out shows this along with the 12z NAVGEM which looks very similar. The low crosses the Atlantic and deepens as it does. If it did take this route then the Southern half would take the strong winds as the gust chart below shows about 55 to 65mph. Overall the models seem to agree on a unsettled start to next week the question is where and how bad? Or will it even happen at all? The 18z GFS Parallel shows this could also happen as it passes over the South of Scotland not deepening at all.
  23. 7 points
    I must say I'm starting to get a bit concerned (having initially dismissed its appearance on yesterday's GFS(P) as being a classic GFS overdeepening ). Matt Hugo just tweeted that the op wasn't an outlier and, while the ensemble mean obviously tones it down a bit relative to the op, it's still a pretty nasty looking system, vaguely reminiscent of 'Hurricane Bawbag' in December 2011: Tonight's GFS(P) looked like one of the less severe solutions with its track, certainly compared to the ECM, but even with it has 50mph gusts across the central belt: With the ECM op, 50mph sustained winds (>20 metres per second on the chart) right across the Irish Sea and heading towards hurricane force for many coastal parts: From an IMBY perspective we would at least be spared another Central Belt sting jet event on that trajectory but still potentially quite a nasty storm for many, with the risk extending much further south into England on the ECM, and we'll have to hope it either tracks a bit further north or weakens significantly (ideally the latter). On a lighter note, the upper profile at +120 on the ECM ens looks reasonably good for Sunday snow up this way:
  24. 7 points
    Some fantastic posts in here today, great reading. Certainly not time to panic and begin the WIO posts. ECM mean pressure ensemble anomalies were not as promising yesterday evenings concerning possible big picture developments past day 10 but they are still light years from this afternoons GFS op predicted anomalies for the same period which highlights the possibilities that it may be VERY WRONG. ECM/GFS GEM is much closer to the sort of pattern we might expect if the ECM predicted anomalies were to come to fruition to though it may well be overdoing things, especially given this mornings ECM ensembles did not show such a smooth transition of low heights dropping away from Greenland/Canada and causing deep troughing into Europe with the expected height rises tot he East and strengthening of the Siberian/Russian high. GEM for the same period So I would say, don't panic! We know we have a period of cool zonal weather to get through which may provide some interest up North for snowfall and everywhere else for possible storminess and it will at least feel seasonal. The big picture suggests that the trough (PV) associated with low heights we would usually expect to keep recharging around Western Greenland/Eastern Canada will drop south and create deep trough into Europe this could well lead to much more amplified pattern downstream than GFS is modelling which would stall low pressure likely somewhere just NW of the UK which could then disrupt SE and give us some undercut. Unfortunately that would not be enough on its own and this is why the prediction of the upstream pattern is so important in how things develop from around mid month and why today's reading on the possibilities and background forcing were so interesting for me. If we get a more amplified pattern later then we must hope that GFS idea of replenishing the Greenland PV is incorrect and that the signal within ECM ensembles for low heights to drain away from the region is correct. This mornings ECM was somewhere between with the deep trough and associated height rises through Russia but with too much residual energy around Greenland - this may actually be not that far off what we get which would still offer potential with WAA being forced into Arctic regions and a strengthening Siberian/Russian high but it would be a slow burner. That said the end result could well look like the OPI anomaly predictions with lower pressure through Northern Europe and with Arctic/Russian heights gradually extending West. Of course that would mean a greater chance of cold weather for the UK but it also suggest it could be relatively unsettled - all a long way out though so I will stop there. Look for ECM to show good troughing into Europe with much more significant blocking to East with hints of undercut and retrogression by day 10 but if not then check the ensemble mean anomaly charts to see if there is any movement there for better or worse.
  25. 7 points
    Some improvements so far on both GFS's caused by a better upstream pattern, we are likely to see some more volatile outputs upstream for a while. Rather than repeat the same post again for anyone interested I did a more in depth one at Page 8, post 160 which explains a bit better why we might get perhaps a bit more interest. I should add these comments from the updated NCEP discussion are welcome: NRN AND SRN STREAM FLOWS OVER NORTH AMERICA SHOULD TEND TO AMPLIFY OVER TIME GIVEN THE SETTLED UPSTREAM NERN PACIFIC MID-UPPER LEVEL TROUGH POSITION. THIS PATTERN SHOULD PROVIDE SYSTEMS FOR A PROTRACTED WET PERIOD ACROSS THE NWRN US WITH SYSTEM APPROACH/PASSAGE AND AN EMERGING DOWNSTREAM WET PATTERN FROM THE E-CENTRAL TO ERN US. WHILE FLOW EVOLUTION DOES OFFER SOME POTENTIAL FOR SOME STREAM PHASING AND COASTAL LOWS FARTHER EAST...THE TIMING OF EMBEDDED SHORTWAVES IS TOO UNCERTAIN TO DETERMINISTICALLY DEPICT FEATURES WITH MUCH UMPH
  26. 7 points
    I received an email with regards too my enquiry about the GLOSEA 5 from the MetO today. Hope it's ok here Mods, Thank you for your email. I have received the following response from our Climate scientists: "The GloSea5 forecast is initialised with observed conditions. Unlike most short term forecast systems, which usually use an atmosphere model with specified sea surface temperatures for the period of the forecast, GloSea5 uses a fully coupled ocean-atmosphere dynamical model. Coupled models tend to ‘drift’ from the observed climatology, so to correct for this, a set of retrospective forecasts (often referred to as hindcasts) are run. From these we can estimate the drift and then calibrate the forecast. In this case the calibration period is 1996-2009. http://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/gpc-outlooks/user-guide/technical-glosea5 In making the forecast there are a number of sources of information taken into consideration: the current observations, known forcing factors (or drivers) and, importantly, several dynamical forecast models. For the forecast for DJF 2014/15, issued 20th November 2014, there was good agreement across these models for enhanced likelihood for the positive phase of the North Atlantic Oscillation (NAO), cyclonic westerly circulation and warmer than average conditions for northern Europe. In addition, models had shown a very consistent signal for early winter in this respect for the past few weeks. Of course, this doesn’t rule out the possibility of blocked conditions and a cold winter. It can be seen from figure T2 in the Temperature Summary that some forecast ensemble members lie in the lowest temperature quintile, but overall the probability distribution has shifted from climatology to favour a greater chance of warmer conditions. Note that this forecast is regularly updated for the risks of cold/warm and wet/dry as the atmosphere evolves so do look out for the update in December. Initial analysis of the forecast from the GloSea5 system suggests that the positive NAO signal may, at least in part, be driven by teleconnections from the tropics. In particular, there was a clear wave train in the upper level troposphere emanating from the tropical Atlantic and supporting the positive NAO. The forecast also showed anomalously high rainfall in the far west Pacific, associated with warmer than average sea surface temperatures in that region. Understanding the drivers of predictability is an important part of the forecast process, although it’s useful to bear in mind that they may not act together in a simple linear manner. Dynamical models are the best method we have for studying the interactions between the different drivers and there is a continual programme for the development and improvement of these models." I hope this helps. If you have any further questions or need any additional information please contact the Weather Desk on 0370 900 0100 where one of our advisors will be happy to help you. We are open 24 hours a day, seven days a week.
  27. 7 points
    In terms of comments from NCEP alluded to by OMM I think this could bring some reliability issues upstream in the NWP. Theres often a problem deciding on whether you get an interaction between the northern arm of the jet and the STJ, this is important in terms of depth of any low pressure there and its track. Although the general pattern over Europe is generally agreed on across the model suite the upstream area may well alter the jet track into western Europe, low pressure in the eastern coastal USA will effect the Azores high, so the interaction between those jets is pretty crucial. You can see further into the NCEP discussion they're already discussing the will it won't it interaction: ...ONCE THE SOUTHERN JET MOVES INTO THE SOUTHERN TIER STATES...DOES IT PHASE WITH THE NORTHERN BRANCH...AND IF SO...AT WHAT LONGITUDE IN THE WESTERN ATLANTIC WILL THE PHASING TAKE PLACE. Below is the ECM T168hrs chart you'll see the STJ and the PJ: The phase point for those jets is important, for those hoping for something a bit colder you'd preferably want any phasing further west and one low developing thereafter which can effect the Azores high, so as an example I've superimposed the effects here: If you get a deep low there the natural effect is generally for this to travel more ne than east so you might then get some temporary ridging further north of the Azores high and more dig south downstream of troughing. However theres not much chance of any longer cold interludes in the expected mobile set up, effectively you're just trying to squeeze out as much wintry interest as possible. Longer term if the Siberian high does edge west then these phasing interactions upstream would prove even more important but with that strong STJ at least this throws in a variable, at this point some uncertainty is welcome given the general theme of the outputs.
  28. 7 points
    You've set the cat amongst the pigeons there OMM.
  29. 7 points
    Really? Looks like a fairly good snow event here for Sunday, at ground level
  30. 7 points
    HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY TUESDAY DECEMBER 2ND 2014. NEXT UPDATE WEDNESDAY DECEMBER 3RD 08:00 THE CURRENT GENERAL SITUATION. A cold front will edge very slowly SE across the SE of Britain followed by a ridge of High pressure across Central Britain later. MODELS-2 WEEK HEADLINE Mostly dry and benign conditions will slowly give way to more unsettled and changeable weather with rain or perhaps wintry showers at times. THE JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble forecast shows a brief dip South in the flow across NW Europe before returning North quite quickly and then blowing across the UK while slowly sinking to the South of the UK later in the run. GFS OPERATIONAL The GFS operational this morning shows a gradual change to more unsettled and very changeable conditions taking over with spells of windy and rainy weather alternating with colder and clearer air with showers, some wintry in places as Low pressure digs further South down across the UK displacing the High to the South and SW further away for a time. Late in the run the High returns close to the South over France and a mild Westerly flow re-establishes across the UK with wind and rain most likely to continue towards the North and West. THE GFS PARALLEL RUN The GFS Parallel run shows a similar synoptic setup as the operational though individual times and positioning of the driving pressure systems affect the weather differently over the UK day to day but the overall mess age is the same in that High pressure to the South and Low to the North remain dominant throughout. THE GFS CONTROL. The GFS control run also shows a more volatile and potentially stormy period a week from now as deep and vigorous Low pressure is allowed to make much larger inroads across the UK with gales and heavy rain followed by chilly aor with wintry showers at times. The trend later is for pressure systems to be less pronounced and with High pressure never far to the South the rain looks like it could become more biased towards the North and West later in a milder westerly flow THE GEFS ENSEMBLES. The GEFS Ensembles maintain a period of westerly winds over the next two weeks circulating around Low pressure to the North and High to the South. As the Jet Stream sinks further South later the winds will become chillier at times especially in the North with wintry showers at times between the passing rain bands. UKMO UKMO today shows a rather cold Northerly flow at the start of the weekend with outbreaks of rain being replaced by wintry showers for a time with a rinse and repeat pattern of rain followed by colder and showery conditions looking likely again early next week. THE FAX CHARTS The Fax Charts show a slow movong trough close to SE England at the weekend before a cold front moving down from the NW bring cold and bright weather with some coastal and hill showers falling as snow in places. Then at the end of the period a warm front brings milder Westerly winds back to Scotland by Monday. GEM GEM shows a pattern which deteriorates conditions across the UK from the North later this weekend as Low pressure makes it's way South deeper into the UK with spells of rain and gales for all interspersed by brighter and colder but still windy conditions with squally showers, wintry on hills especially in the North. This pattern then persists out to the end of the run. NAVGEM NAVGEM too winds up to a more unsettled spell next week powered by a developing deep depression close to Northern Scotland at the end of the run with Westerly gales and rather cold conditions following a band of rain with frequent squally and wintry showers especially across the North and West. ECM ECM this morning shows a pattern also is similar to the rest of the output with strong support for a more coherent attack from Low pressure to the North and NW next week with the quiet and rather chilly benign conditions between now and then giving way to wet and windy conditions followed by cold and showery conditions in a WNW flow. The end of the run signifies the unsettled and changeable period is expected to continue with Westerly winds carrying bands of milder rainy weather followed by colder and showery spells. ECM ENSEMBLES This morning's Ensemble data illustrate a typical Winter pattern for the UK with Low pressure to the North of the UK and High pressure near the Azores giving rise to a strong Westerly flow across the UK with rain at times and average temperatures overall. NOTABLE TREND CHANGES FROM PREVIOUS RUNS The theme has now become strong in support for the quiet and benign spell of late giving way to much more unsettled and windy spells of weather with rain bands and gales alternating with colder and still windy weather with showers, wintry on hills. MY THOUGHTS The models have firmed up on the trend towards much more changeable weather with strong winds developing for all areas as we move through next week. The High pressure to the SW looks like losing a lot of it's influence as deep Low pressure areas tilt towards a slightly South of East track to the North of Scotland. This powers up strong Westerly winds with spells of rain followed by successive periods of colder and showery conditions with some snow likely on high ground mostly in the North at times before the next surge of Low pressure brings the next band of rain and milder air through. This type of structure and sequence is supported by all output with the longer term trend beyond the end of the 1st week maintaining basically Westerly winds and rain at times for all with no clear indication of any major shift towards anything other than a continuation of the zonal train at the end of week 2 this morning. With support for this theory from both the GFS and ECM Ensemble data this morning one has to believe that this evolution maintains a strong chance of verifying from todays output.
  31. 7 points
    Disagree on first sentence (I recall well the persistent zonal & routinely deeply cyclonic signature it accurately offered almost every run!) but largely subscribe to your second point!
  32. 7 points
    No disrespect, but Glosea was spectacularly wrong last winter though, didn't it go for a dry December?
  33. 6 points
    http://www.weathercharts.org/ukmomslp.htm hi all not doing much updating for now as weather is stuck in this cloudy drizzly muck at present cold day but holding temps at night due to cloud and mist nights where frost might happen are friday and saturday and sunday sunday will be a shock if correct a strong north west wind temps cold around 4-5 degrees showers early but clearing quite quick but likely to be sunny after morning so all in all pretty boring for now i will update from tomorrow to see how the weekend looks and possible frost friday night
  34. 6 points
    So...what you're saying is you think it's going to be a "cold-hearted winter"? Totally left field, that! I must be a glass half empty sort of person because i really can't get excited by anything being shown. What happened to my nice crisp, frosty high pressure? Certainly wintry at times on northern hills but cold, miserable rain doesn't do it for me. that really isn't an inspiring chart, is it?
  35. 6 points
    I think you need to visit the stratosphere thread and do some basic reading if you think that a stratospheric event (warm or cold) in December will take till spring to evolve the atmosphere! lol
  36. 6 points
    As for the comment about strat cooling, that's just scare mongering since we haven't even felt the benefits of the much trumpeted strat warming yet, these changes downwell very slowly so the cooling strat is unlikely to impact our weather until spring if it even exists at all!
  37. 6 points
    Thanks Good to be back There's something massively reassuring about this mushy! Like old times
  38. 6 points
    I think its difficult to draw too many conclusions from the output in terms of detail although the overall pattern looks agreed on upto T240hrs. The problem really is the uncertainty over in the USA regarding phasing or not of the polar jet with the sub tropical one, its likely from the outputs that some retrogression of the Azores high is likely to take place and with the trend to push low heights into the Continent its unlikely to be mild. We don't see as much ridging west of the Siberian high on the ECM compared to the GFS P but still pressure is likely to rise to the east, effectively this will slow down the movement east of low pressure which unfortunately means a lot of wind and rain and indeed some snow to higher elevations. I think of particular concern this evening is the ECM low which looks nasty, generally though the ones to really look out for are secondary features, these small lows can often bomb and lead to the worst problems. Hopefully the ECM will tone down this low with time. For coldies although the output isn't perhaps what you want to see there are some chances for something wintry, any snowfall though is likely to be transitory in nature. But good news for the Scottish ski resorts aswell as the rest of European ones. The area to look out for which really determines any cold into the UK is in the eastern USA, this is the area where you're most likely to get some phasing of those previously mentioned jets and the amplitude of any low there will determine the position of the Azores high and therefore the jet track into the UK. So overall although nothing in terms of deep cold for the next ten days, it certainly should keep the UKMO on its toes and of course us as we look to the eastern USA for developments there.
  39. 6 points
    Huge LP from the ECM at 168 hrs,could this be a game changer,or has it just gone off one one? Looking at that chart from the closer UK view reveals a nasty looking secondary LP approaching Ireland.
  40. 6 points
    This is exactly what we want to see and good news for coldies in the UK, this isn't a PV setting up shop there as the cold will be transient in that part of the USA. In this instance because of the set up the more south the cold gets in the heart of the USA the better displacement of the Azores high downstream as this reacts to the more amplified low. The GFS P is very encouraging upto T240hrs especially as it also shows the Siberian high edging west and trough disruption near the UK.
  41. 6 points
    Fascinating developments continuing as we head deeper into the working week and beyond, as suspected. First hints of the 5th December being the first date to watch came from around the timing of my post below. https://forum.netweather.tv/topic/81842-model-output-discussion-1200-hrs-151114/?p=3077689 Well at only t+51 hours we have the NH Jet in the following position according to the GFS P 12z, which to be fair isn't anything worthy of over-scrutiny at least at first glance. Resulting in the following snowfall risk, yes I did just utter that "S" word, hold your horses though. Some 15 hours on, the snow risk remains distributed over a few parts of the UK by then but invariably only a fleeting opportunity for a few flakes blowing in the wind, generally restricted to higher elevations. Oddly, these synoptics are brought about oddly, by the following NH Jet positioning and are within the reliable timeframe. Note the split flows (shown in both Jet profiles) were highlighted a few days back by Chionomaniac as a phenomena to expect as we head deeper into Winter. More specifically from NH viewpoint, there is a general trend in developing the Arctic Blocking High signal across all model suites into week 2 of December, most pleasing to the eye for coldies, I might add. This is something I've witnessed across a great many outputs of late and I am led to believe, as it works alongside other factors in the stratosphere it may aid us with moving any deep entrenched cold into our neck of the woods by mid December for example. All in deep la la land for now so let's get back to more immediate timescales. As alluded to, the blocking signal is holding firm by 1500hrs on Sunday 7th December, which is t+129 hours and is reflected in the NH Jet profile below. A NW air flow is affecting most parts of the UK by then and brings with it, further hope of snowfall for a lucky few. In fairness, Temperatures away from the various weather fronts will be nearer average if not slightly below by day and we should perhaps focus our attention on the heavier bursts of showery precipitation for any likely wintry bursts. Not forgetting these are simply ONLY risk charts, so please take them as intended by their description. I WILL END THIS APPRAISAL NOW OF THE GFS PARALLEL RUN AS YOU KNOW WHAT. ITS ACTUALLY BASED ON THE 6Z, SORRY IT CANNOT BE ACCESSED YET ON NETWEATHER. NO MATTER THOUGH, SAME THOUGHTS WILL APPLY UNLESS SOMETHING DRASTICALLY ALTERS THE NORTHERN HEMISPHERIC PICTURE COME THE 12Z. Time for me to dive into an offline cesspit. High Arctic Blocking signal largely remains throughout the middle to latter stages, which is a good sign for a Winter far removed from the likes of last year.
  42. 6 points
    Although the ECM NH pattern continues with the theme of the PV being less organized and more mobile, at D10 it has returned to Greenland vicinity. In fact much like the GEFS have been suggesting for many days. ECM have seemingly ditched its medium term travels to Siberia. GFS has proved very solid in the 8-12 day range re synoptic changes (compared to the ECM op): With that sort of starting point for the middle of December it is no surprise the ECM 32 day update suggests a more zonal pattern till the New Year. It does tie in with many long range models for the UK's Winter (GloSea and UKMO just a couple). So the SSW is possibly going to be a make or break for this Winter and I know the Pros are very confident of this sometime in January, hopefully not too late in the month. Even GEM, who have arguably led us up the garden path more than ECM have a zonal onslaught at D10: Both have been playing catch up with GFS. The GEFS are maintaining the mobile PV in FI, a time sequence of the mean: D10: D13: D16: This does not really promote any HLB in that period due to the mobility of the pattern and I am assuming that it will then transfer its energy elsewhere afterwards. There is also a flow of the mean cold uppers from D10 towards Siberia and this is not ideal for the UK to grab any trop cold: D10: D16: So in reality just run of the mill December weather coming. Absolutely no sign of any cold snap (meaning snow) let alone spell (through blocking) and with the synoptics not conducive to cold then it remains a waiting game.
  43. 5 points
    Models in tandem today with the projection for a deep trough to become established over the country next week, before then, fairly settled in the main, with cold frosty nights and chilly bright days with a weak front on Friday producing light rain for most and snow on higher ground in the north. Sunday will see a repeat performance but with a more active front and thereafter polar maritime air again so chance of wintry showers to modest levels in NW parts. Into next week - the Jetstream looks like becoming preety active and there is a strong likelihood of a deep low tracking just to the north of the country becoming quite a feature and perhaps dropping southwards a little with cold polar maritime air being directed down from the NW as the week wears on - hence the reason for the BBC suggesting eventually a lot of snow in the north.. A very 'seasonal outlook' on the horizon bit of everything eventually for most, calm sunny frosty conditions, light rain/snow on northern high ground, becoming potentially stormy with heavy rain, and the chance of more significant low level snow in the north.
  44. 5 points
    The GFS is cold throughout it's run, we also start to get a block to our NE again with the Azores moving SE of the UK. Some snow potential as well with -6's covering the whole of the UK and -8's for parts of Scotland at day 10. I'd take this run If I was offered it!
  45. 5 points
    fantastic first post dr astro, welcome!.
  46. 5 points
    Way back in the early noughties, the May SSTs were used as an NAO indicator in the Met Office's winter forecasts. It wasn't mentioned after they dropped the public seasonal forecasts but seems to have made a reappearance in a paper about the GloSea5 prediction skills. I would offer a tentative suggestion that the long range models are being skewed by very warm oceans, all over the Globe. It is interesting that the NOAA LR forecast, predicated only on SST anomalies, is showing something very different as a forecast for this winter.
  47. 5 points
    On for this weekend - the 5th to the 7th Dec was trending as early as the 27th November so all credit - still time to go all **** up though. Keswick on Sunday ppn of sorts down to 600ft - tops should see their first realish falls although Scafell has had a dusting already. Ian
  48. 5 points
    ...but not based on this evening's EC Monthly, which if anything has whiff of slight positive temperature anomalies into week 4 and very few genuinely cold solutions amongst postage stamps (or extended ENS site plumes) through weeks 3 & 4. So, thus far in broad alignment with GloSea5's take on things. But hey-ho, it's light years away in reliable timeframe.
  49. 5 points
    Certainly a very interesting GFS parallel tonight with something for everyone, from rain and storms to snow showers with increasingly potent cold incursions from the NW. By day 10 it is not a million miles away from what we might expect an average run from ECM mean pressure anomaly charts show except with a flatter trough which results in lower heights to the NW and no strong Siberian/Russian high backing West. Still snow falling to low levels in showers on this chart and shift things West and add a little more amplification East and West and bingo a cold spell would be setting up. Goes to show that we are not staring down the barrel at Atlantic dominated weather right through to mid December and beyond at this point.
  50. 5 points
    At last we have some charts worth posting, after weeks of dross with the models giving coldies the blues, the Ecm 12z op run shows some blues for most of us to enjoy, regular cold incursions with wintry showers and night frosts and then a peach of a chart to end the run with a big bubble of 522 dam covering the BI..and it's low pressure and cold uppers..hold on, surely that means a good chance of snow. I feel like a stella now
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