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  1. 67 points
    Evening Based on the pretty successful thread around the current seasons NH patterns I thought I would lay out the thoughts for Winter 2018. Headlines - Following on from Autumn > Winter 18 Globally is set to smash records- From record warmth to record cold, record rainfall & record drought... This will be driven by weak westerlies & a possible SSW in mid December- Teleconnection notables **could** be * Lowest negative AO on record ( or at least a challenger ) * Lowest & or most positive POL on record ( this metric can be good for us in either positive or negative mode, however its the extremes of pressure that support the -AO ) * Most negative 100 or 10HPA zonal wind on record in Merra2 data at any point during the Winter ( most likely earlier rather than late ) UK wise - The overall theme is a very high probability of a below average winter with the sub 3c breeched twice - ( maybe 3 times ) Winter NH patterns For a winter forecast this last 10 or so years a traditional method by most has been adopted - taking the state of the Teleconnective background signals & matching them to analogue years in the 1900s - & I still believe there is some merit in this especially when we are in very high NINO index years as this can be the overuling global driver over & above any favourable ones - The last 5 years or so have seen attempts to create a winter forecast by morphing analogue years for the stratosphere - again with some limited success- However there is one fundemental issue with using these analogues which is the assumption that should the same metrics repeat themselves then the tropospheric responses would all align & the H500 height anomalies would be at least very similar across the NH. Well now, as we get better understanding of how climate change is impacting the weather (most notably the ice & arctic heat ) then all these analogues potentially become redundant due to the troposphere becoming more & more independent in relation to not allowing the stratosphere to downwell - ( otherwise known as being 'decoupled' ) The main driver of this is the surplus warmth left over in the arctic at the end of the summer & Autumn as well as the record breaking ice loss along the peripheral ice edges - Not only this, as the mid lattitudes heat up we have grown larger more 'intense' areas of high pressure transporting yet more heat upwards into the pole- ( NB even now this week in November we see record High pressure developing towards Scandi pumping more warmth upwards ) The feedback then becomes self perpetuating- I would also like to add to this the 2018 'spin' that not only does this year have a massive heat anomaly,but perhaps ( IMHO ) a dipole of heat / cold across the areas with early ice build up V no early ice What you then allow is even more inconsistency with heat creating vast gradients across the pole allowing for yet more blocking - & because of the dipole the balance of heat then allows potential displacement of the tropospheric vortex - Its no wonder then that we see the amount of wave 1 & wave 2 blocking attacking the early vortex & the inability of the stratosphere to couple downwards as the resistence upwards is balancing it out - What you get as a net of all this is no tropospheric analogues because there isnt a teleconnection that quantifies Arctic Amplification ( AA ) & there are no stratospheric analogues because if the strat cant downwell then its overall strength is much less impactful on the troposphere - - So as mentioned then- Autumn has been one of blocking highs - even when the stratospheric jet has increased along its seasonal pathway the troposphere has refused to couple with it- ive highlighted this is due to the anomalous vertical heat flux & perpetual bombardment of upward waves thats served to offset the downward propergation of the strat leaving the polar cap sitting in equilibrium Seen here ( Source AER ) Also shown is the continual warmth in waves pushing upwards from the troposphere - & now potentially down from the strat- Remember the upper vortex is *Stronger* than average this year so while its vulnerable to attack - early displacement to russia * Isnt * the same as a SSW split - for this we need to see a reversal of the zonal wind @60N/10HPA * Classic winters like 1962 had early warming over the canadian side which took the vortex out for the entire winter then went on to allow for blocking to remain in situ for long periods of time- I believe this winters signal of a tropospheric decoupling could allow for a similar scenario especially if the SSW underpins it - QBO support - The initial concern is that a downwelling WQBO would omit us from the chances of a SSW however we are still in the transition phase where 30MB moves to positive but the 50MB lower down holds negative- The impacts of this are that the QBO will not act as a blocker early on the potential SSW this winter - Ive uploaded the image & I should have shortened the timeline but hey ho! h Possible Strat warming ~ Mid December... The strat as we know has been under attack this winter & the lower vortex especially has recently born the brunt of any deceleration - dropping to around 5M/S where as higher up the 10HPA wind has remained less impacted The day 16 disks which when the next wave of vertical flux peak starts to show a canadian warming & relocation of the vortex - So worst case scenario a dipsplaced vortex towards Russia, best case is a split & even less eastward zonal wind speed !! ** Key date proposed for major displacement / poss warming Dec 15th but remember because of the decoupling this may only serve to reinforce the blocking thats already there - ** DJF UK CET - Viewpoint & Anomaly plot The seasonal winter CET stands from Hadley @ 4.13C broken down into D 4.7 J 3.9 F 3.8 Statistically across the last 100 years sub 0c months are - 8/300 which is about 1 every 40 years ~ 2.5% chance. sub 1c months are 17/300 which is about 1 in every 18 years ~ 6% chance sub 2c months are 29/300 which is about 1 in every 10 years ~ 10% chance. So we can see the numbers are low- in terms of our chances I try to quantify this winters numbers by saying that a sub 2c is as high as 50/50at this stage ! & sub 1c maybe 25% - Sub 0c maybe 10%... Overall projected winter CET SUB 3c ~ 2-2.5c Overall pressure anomaly locations for Winter 18- These may wax & wain however general locations feel about right- Storm track is in green - Cold winter for central states as well as possibly the east depending on whether the blocking is more East based towards a +PNA or more west based -EPO ( the further west you get the -EPO you do encourage a ridge on the SE coast ) UK sits on the NW side of the low anomaly in Europe - so in that respect continental air is sent west in our direction- which will drive snow events- Europe as a whole cold & below ave - especially central & Western, however places like Greece / Turkey could benefit from warmth up from the south - It is my belief that confidence in the projected patterns for this winter are about as high as they can be in terms of potential blocking- especially in the locations we need it - what you will see from the models is perpetual ridging to the pole from every angle across the globe ( -EPO / -NAO / -POL ) If the vortex remains uncoupled then the speed of the 100HPA vortex is more crucial than the 10HPA one higher up- This will continue into December where the idea of a 'front loaded but possibly fully loaded winter comes from' - The nature of reduced westeries also impacts the UK around rainfall- Mean averages especially for the NW will be lower however what you lose over a month in terms of loss of westerly driven wind & rain events may well be offset by slow moving PPN events ( The same as Autumn ) So there you have it - 2018/19 Global extremes of weather & for the UK higher probabilities of exceptional weather which for once is more in favour of exceptional cold instead of warmth.. S
  2. 52 points
    It's a pity the debate broke down a bit on here today - there were some interesting points made and I'll stick to these. Tamara is fundamentally right - the blocking pattern that is emerging for the last third of the month was written large in the predictable rise and fall of tropical forcing, and in predictable kick starts provided by frictional and mountain torques. The impact of these is to create a pattern that rarely sits still - it oscillates with an ebb/flow that isnt random - it is generated largely from the global powerhouse that is the pacific ocean and moderated by local factors. If it was easy to get all these in line we would have produced models that could nail the global pattern years and years ago: bottom line is that the large scale drivers combining with significant local factors creates a weather mess that can be hard to untangle. When we consider the impact of the stratosphere we have to be careful considering it as a local factor - it isnt. It's a huge driver of things particularly if it couples to the troposphere...and in some winters effective coupling like this can spell the end of any significant ridging and an end to snow chances in most of the UK. My head hurts when I try and read into the academic literature on this - but I believe I am accurate when I state that more and more research is pointing to clear links between the pacific pattern, the GSDM that Ed Berry piloted and stratospheric variation. I dont think these links are clearly stated anywhere (hence why my head hurts trying to grasp it) - but they are undoubtedly there and I suspect over the next 10 years we will see a lot of research tying the two together. We certainly cannot deny that significant warming episodes in the strat lead to dramatic impacts in the trop at times - and that reason alone guarantees that the research will happen. So - Tamara is on solid ground here. The GSDM is a tool that provides a really strong background for us to consider future weather developments, and as the link to the strat becomes clearer I suspect we will see the potency of the teleconnective argument grow. However - there is a very big BUT in all this. More local factors that can skew things to my mind are growing in significance in our warming world. As Steve pointed out - we have a signficant change in albedo effects in autumn now purely because there is so little ice left in place come September, and research is suggesting that black particles in the ice are going to continue to accelerate the melt pattern. What does this mean? It suggests to me an almighty spanner that can be thrown into the works for winter forecasting should the model algorithms be insufficiently sensitive to reduced ice impact and resultant impact of heat transfer from sea to atmosphere at this time of year. We saw last week exactly what a rogue local element like storm Oscar can do to patterns in the Atlantic - the storm became swept up in the jet, parked itself next to the strong block in place over Europe and gave the UK some decidedly dodgy weather for a few days. The severity of that weather was not predictable within the GSDM model even if Oscar slotted into the trough/ridge pattern that was definitely suggested at the start of the month via the last round of pacific forcing. I'm with Masiello on this - past analogues are bin lining material at this time of year now because we simply arent on the same playing field as we were 30 years ago. We have less ice and warmer oceans in general - and these are helping create a storm pattern that is hard to nail down. Each of these storms can add a huge amount of heat energy to high latitudes and become a local factor that creates a regional/global impact. What does this mean for the coming winter?? Keeping it as simple as I can: 1. Never move too far from the analysis provided by phases of the GWO as a product of the GSDM. These are key guides as to the global longwave pattern and as sure as we are heading for circa 10 day blocking pattern we will surely see that blocking pattern relax a bit into December as AAM tendency falls and the polar jet is reawakened. This can only serve to flatten the pattern in relative terms. 2. Watch carefully the disconnect between Strat and Trop. It is interesting that, as per last year, we seem to have a disconnected setup in operation, though I guess the real strat expects might argue it simply reflects the descending stage of the QBO and isnt so significantly disconnected at all. Not convinced about that - I think we could have expected a stronger connect in 2017 and again this year as we move towards winter proper...and I wonder whether all that latent heat loss into the atmosphere via the refreeze is making a bit of a mess of standard autumnal patterns in years when we dont have a rampant vortex ignition. 3. Look for the global semi permanent highs that it appears we are starting to get in winter. Ice loss would seem to be assisting high pressures around Kara/Barents and over in the north pacific. If we end up with a sustained year on year tendency for a Kara High then be sure this will lead to local assistance in any disruption to the vortex. 4. Keep an eye on the temperature profile of the equatorial pacific. Currently cool over the Indian Ocean, warmer over the Pacfiic proper. As Snowy Hibbo very interestingly pointed out - this may help reinforce an MJO repeater pattern centering around phases 6 - 8 and this will not harm our chances at all of winter snow and cold interest. 5. Watch out for solar activity spikes...or in the case of the current year watch out for long spells of a spotless disk. I wouldnt dream of really understanding the physics of lower TSI and the reasons for the impact, but observationally I have certainly noticed a tendency for a more meridional jet at times of low solar impact, and we are in one of these now. And arguably this can be a big factor that can interfere with predicted long wave developments - anyone remember Dec 2012?? I dont feel confident making a major forecast out of all this - but I am drifting towards agreeing that we will see an above average winter of snowy satisfaction because factors 2 - 5 above will help reinforce the weak Nino background state and encourage a pattern conducive to ridging rather than flat atlantic jet dominance....and if we see the huge high Steve alluded to stick around and promote wave breaking to really threaten the strat then maybe a SSW can occur (despite the low solar, weak nino combination that statistically isnt the best for an SSW) and then a spell of proper winter weather might bed in. Better tie all this into a model diagramme otherwise a zealous mod might click delete - so any basis in NWP to support this optimism? In the shortish term this is a great anomaly chart if you want some colder intrusion (though like Tamara I'm afraid at this time of year I tend to think this is more likely to bring very cold rain rather than snow) And longer term I like the bottom of these 3 glosea probablity maps. Note the definite suggestion of below normal heights over Europe with less chance of that to our north. That's a good signal for a cold/snowy winter if you ask me.
  3. 49 points
    We really couldn't ask to be in a better place at the beginning of winter than where we are now. Incredible Scandi blocking/moving to Greenland with continued warm pulses of WAA into the Arctic making things favourable for more blocking and more WAA = it becomes a self sustained pattern. MJO moving into phase 8 which for December is suggestive of Northern blocking and then when you take into account the increased chance of blocking with low solar activity/low sea ice and combine that with a weak ENSO not overriding any other signals, we've basically hit the jackpot. I see no real Atlantic threat going forward, the atmosphere is primed for blocking to continue probably well into December, we then have the possibility of an SSW which could cause a split/displacement in the Vortex and bam, you've got December/January, 2 months of potential almost continuous below average temps/snow. Blocking doesn't = cold of course so we need to be cautious there, but things are looking fantastic. Cold this week, perhaps slightly less cold in the South by the weekend but with models agreeing on the slider/undercut of the low, don't be surprised to see further upgrades as things trickle from FI into the reliable. This isn't currently about "will it snow here, there or anywhere" for me, it's about the bigger pattern and going forward it looks fantastic!
  4. 46 points
    If we take the ECM at +168 two days ago And compare it with the ECM +120 from tonight You can clearly see that as we’ve got closer to reality, the model has; 1) Underestimated heights around Iceland area 2) Has started to disrupt the trough to our west more, it is more negatively tilted and a little more elongated. 3) heights in Europe lower than previously modelled If that trend continues in the next two days and the same for the subsequent frames after this, perhaps Day 10 will look a lot different come T+0 than it does now. This is the same for GFS too, not just ECM. Uncertain outlook but certainly upgrades in the mid term from the models. UKMO pretty solid. Going to wait a couple of days at least yet.
  5. 46 points
    Aside of the significant and near record kicking the stratospheric vortex will be receiving for this part of the early cold season (c/o wave 2), interesting to note that the tropics are choreographic themselves nicely in the -NAO context. The week 2 forecast depicts a strong suppression signal in the Indian Ocean and, consistent with El Nino events (of similar magnitude), a convective signal across much of the central Pacific basin. That's consistent with top 10 -NAO Decembers: Even more so when +10 Decembers are subtracted: Decembers with similar other drivers for context.. We are at the point where, if models are near correct, feedback loops begin to be established - cooling of the sub-tropical Atlantic and warming at higher latitudes, development of strong Siberian ridge and Aleutian low, stratospheric feedback into January and February.
  6. 44 points
    Through the mist people should be starting to put the jigsaw together- Scandi / Iceland / Scandi oscillations- becoming ever colder... We are set for Winter - Winter forecast out later tonight....
  7. 44 points
    Considering the sort of charts that are starting to appear, and since it’s getting closer to the crazy season, it’s time to start re-opening up this store. Might also be worth saying that your access to this store will be banned if we see lots of bad behaviour from you in this thread during Winter! Just an advance warning...
  8. 43 points
    The models have retracted away from the warm NW push of southerly air to be replaced by trough disruption & energy moving ESE A classic case of models moving away bias into reliable modelling--... Its like for once the models have listened to what the forecasters on here have been saying.....
  9. 42 points
    Nino is here, and has been for some time since October. We are playing real time Nino climatology here, which suggests December may be a touch too soon on cold backing sufficiently far west. That said, +ve height anomalies to our east and NE and low to the west are exactly what we should expect. GEFS mean 12z starting to rebuild a ridge across NW Europe as the MJO quickly cycles through the Indian Ocean. CFS stratospheric modelling continues to look 'interesting' for last week of December, which would have some merit given recent musings.
  10. 40 points
    Amazes me that in a thread titled 'hunt for cold' some are hellbent on writing off colder weather for several weeks because the Atlantic gains control and GFS has been showing mobile / mild southwesterlies deep into FI. We all know a pattern change can occur within a week or so and takes the models a week until they start to cotton on to the changes sometimes. I don't think the usual 'mobile/zonal takes weeks to budge' applies atm given state of the upper patterns to start winter. Plenty of clues to the triggers for this potential change already been posted by myself and others last few days, so lets not write off all of December for starters! Back to the 12z, day 10 onward shaping up nicely on the GFS operational, the ridge building to the N/NE kind of follows what I might expect for the response to the MJO heading into P7-8 albeit expecting this to occur a little later than advertised.
  11. 40 points
    Guys I concur with @bluearmy Lots to look forward to as we enter December - Also the zonal winds dropping throuhh the floor- Im off to New york - So offline till Sat next week Have fun !
  12. 40 points
    Morning all, snow arrived on time, just as predicted by the high spatial resolution snow model from 48 hour out. Amazing accuracy produced, even predicted the start time and snow depth to the hour and cm with my location 1km x 1km. As usual its result was spot on, 10pm start time Sunday evening and snow depth of 5 cm 6am Monday morning. Some of its data is fed from the longer range single powerful model our experts use over here. This model has been rock solid in showing a strong Arctic ridge towards the last week of this month with low pressure over Southern Scandinavia to produce a more meridional flow. Yesterday our team indicated the low would be near Denmark at day 10 and with any Atlantic milder air incursion only making limited progress to remove the cold block developing to the NE ( if any ) So that was a optimistic update for colder forecast. Will get an update from them in about 2 hours time to see how things are looking and will ask for specifics with regards to UK interests. Meanwhile we now have the excellent service of the snow fine mesh model now providing us with hourly information here in resort. Try and get some pictures of the snow this morning to wet your appetite . C
  13. 39 points
    THE GLOBAL SYNOPTIC DYNAMIC MODEL (GSDM) That was a superb post Tams @Tamara. Spot on as usual and providing some very sensible balance to some of the hype expressed by a few posters on this thread (far too early to say whether the upcoming cold spell will last for weeks on end). You came in for some very unfair criticism and Ed Berry and the GSDM have been thoroughly quoted out of context. Rather than get into this unfortunate ongoing debate on this forum over the relative merits of teleconnection science, perhaps we can let readers decide for themselves. I have been in touch with Ed Berry during this year and had some fascinating exchanges with him. In May, he sent me a link to his YouTube video on his outstanding one hour seminar presentation on the GSDM. Feb - this will answer your question in full I posted exclusively about this on the Teleconnections thread on two forums back on May 24th. I copy my opening paragraphs below (marginally edited to be current): What is the GSDM and how does it help with subseasonal weather forecasts? - A Review of This Presentation This specialist "Teleconnections" thread was set up to examine and learn more about the main drivers and influences on the broader global weather patterns and how these drivers interact with each other and which are the more dominant ones. Some of the posts have already focused on the great importance of understanding the major role played by AAM (Atmospheric Angular Momentum) and the torques. Several of us have discussed the GSDM (Global Synoptic Dynamic Model) which was jointly developed by leading meteorological scientists Edward K Berry and Dr Klaus Weickmann while they were working at NOAA in the late 1990s and earlier years of this century. They also devised the GWO (Global Wind Oscillation) as a way of plotting and measuring the amounts of relative global AAM, FT (frictional torque) and MT (mountain torque) at different phases of the cycle. They became leaders in this specialist research which has been used to assist in understanding impacts on global weather patterns and upcoming changes up to a few weeks ahead.  Unfortunately, they left NOAA several years ago (in 2015) and it seemed that their vitally important work had ceased with a great loss to advances in meteorological science. We have been trying to track them down and recently found an email address for Ed Berry. I sent Ed an email and I was delighted when he replied almost immediately. He explained that Klaus Weickmann retired several years ago. Edward K. Berry (Senior Weather-Climate Scientist) continues his excellent work on the GSDM and retains his lifelong passion to develop the model and its meteorological applications further. We have exchanged a few more emails with Ed and he is very supportive of the work that we are doing on this thread. I hope that we can persuade Ed to post on here in due course. (Ed Berry should not be confused with another Ed Berry who is Dr Edwin Berry and a climatologist) I asked Ed if he could assist us with obtaining past AAM, FT and MT data (which had been withdrawn from the NOAA Maproom archives) as well as more comprehensive current data and I explained to him that we had been in touch with Victor Gensini (Assistant Professor, Department of Geographic and Atmospheric Sciences, Northern Illinois University) who has been working on and producing some of this missing data - several of our posts include examples of Victor's charts. Ed told me that he was in touch with Victor and they had discussed some of this work. Victor hosted an AMS seminar recently (American Meteorology Society - Student Chapter, College of DuPage, Chicago on 28th March, 2018) and Ed gave a one hour presentation on the GSDM (as shown in the title to this post). Ed emailed a link to his presentation last week (May) and I have already viewed it three times, learning a little more about the GSDM each time. He gave me full permission to review it on here. Firstly, here's the link to the Research Portal entry where I placed it. It will take you to a short summary with a direct link to the full presentation. Just click on this title: What is the GSDM and how does it help with subseasonal weather forecasts? A YouTube Presentation It is a brilliant seminar with clear charts and explanations, ending with a question and answer session. For anyone wishing to learn more about AAM, the torques, the GWO and how they interact with other major teleconnections like phases of the ENSO (El Nino Southern Oscillation) and the MJO (Madden Julian Oscillation) then this is absolutely essential viewing. I also strongly recommend this for more advanced viewers as well. The presentation is right up-to-date and includes the 2018 SSW (Sudden Stratospheric Warming) event and links to key issues like climate change. Much of the presentation is slanted towards the North American climate and US weather patterns but it has a global significance and includes impacts on both hemispheres. I show a small selection of the charts from Ed's presentation below to whet your appetite: (see note below) My full post is on page 7 of the Teleconnections thread and contains a selections of the charts from the presentation. Here's the link to that page (just click on the chart below): We can all learn from this presentation and I sincerely hope that some of the misunderstanding of this vital part of the science will now be alleviated. I will only rarely post on this thread during the busy winter period. I will be on several of the specialist threads, including the Teleconnections thread, the Arctic Sea Ice and Stats thread (where I've recently posted on Greenland and Global Glacial Ice) and Antarctica thread (where I also produced a long post) as well as on the South West regional thread (when things get interesting locally). I shall also be very busy building up the Research Portal on the US forum (where I'm also a member) and I will also cross post on both forums where it is appropriate. David
  14. 39 points
    Ive quoted this post ( all of it ) & bolded your words that are important. This isnt anything personal nor anyway to be '1 upman' however whats clear here (to me) is using the GSDM doesnt generate a forecast & at a more local level does little to forecast the type of change we will see in the next 10 days - In your own words you do not believe that the tropics & associated teleconnective GSDM numericals indicate a change indeed the metrics above whilst up & down actually fit in a regular oscillation of normality... So, as you indicate - relative normality should remain in situ all be it perhaps 'slightly' orientated to weak amplification- Some points if you will... - I watched Ed Berrys presentation on the GSDM & in his summation at the end he particularly cited 2 areas of weakness in the whole process - - Lack of understanding of the stratosphere - Little or no real understanding of the link of arctic ice loss to arctic amplification - As a result of this look at the facts before us - The GSDM stand point is in your opinion nothing more than temporary amplification & no indication of patterns like the 80's yet in 5 days or so we are at a start point where the depth of Scandi high pressure is ~ 588 DAM circa 20 -24 Dam higher than any that can be found- Quote Blue army - Also post this nothing stands out in the GWO / MJO or indeed the GLAAM that supports high pressure retrograding to Iceland & edging to Greenland- The logic to me is that the method has low credibility if it cannot pick out extreme change- I scoured you entire post & couldnt see any mention of ice anomaly - Yet this year saw the highest net polar temperature anomaly on record & the lowest every recover on record, adding to this the balance of ice in october being heavily weighted to the Canadian Side & record low anomalies over kara / Barents & laptev - this is creating a further dipole allowing for massive heat transfer North... So I dispute anything that the people write on 33andrain relating to GSDM because your putting a puzzle together without using any edges - This winter is going to be a decoupled winter Trop > Strat created by the heat transport driven by residual summer heat & ongoing ice loss - Your record High pressures are the result of more mid lattitude heat which net allows more robust high pressure to deflect the jet - If you put all this together plus the suns weakness we stand on the cusp of a historic winter - which can forecast in advance - with little mention of the GSDM- The UKMO whilst great will never press release any of this because it would create hysteria - however I can guarentee they will be concerned by now especially after Glosea updates... Best. S
  15. 38 points
    T324 gefs mean across the polar field .... I doubt this place will be so quiet in a weeks time ...
  16. 38 points
    An interesting viewpoint. Here is another. GLAAM remains high - in fact it is very high and the last AAM cycle really did not dip very far - it is back on the up and let's not forget the MJO forecast I posted a day or so ago What is interesting is that the current uptick in AAM once again has happened without input from frictional/mountain torque, as these normally precede such activity. Meanwhile we are in the middle of modest wave 2 action on the vortex, with a ramping up of subsequent wave 1 in the forecast With these background forcings I cant see any return to zonal for any period of time. We might get a trough stuck in a position that causes some grief to cold lovers, but sweeping west to south westerlies in the true "zonal" fashion look long odds at the moment. I'm not sure that NWP will be resolving this data particularly well, even assuming the vortex keeps its shape and coherence. I dont have the skill of GP or Chio on wider implications, and if Tamara is still surfing these pages then she has far greater experience in analysing GSDM patterns than I.....but optimism regarding the broad pattern (if you want snow chances that is) looks pretty well founded to me at the moment. It's still early days.... but confidence in a cold spell around mid December continues to grow....and the current shape of things would suggest that this could be only the beginning of a recurrent pattern.
  17. 38 points
  18. 38 points
  19. 37 points
    Compare days 1-5 GEFS z500 mean height anomaly: With days 11-15: Substantive shift with mean trough in the North Pacific being replaced with a mean ridge. That ties in with this: MJO fairly rapidly moving through the Western Hemisphere and into the Indian Ocean. That's a Nina like cycle within a broadscale Nino base pattern. Usually this type of juxtaposition is good from a -NAO evolution. Next evolution would be for the MJO / convective signal emerging across the Maritime Continent and associated tropospheric impacts to the stratosphere, which continue to look like mid to late December, with perhaps earlier evolution of a -NAO through more conventional (MJO/GWO) feedbacks.
  20. 36 points
    Worth noting that in the day 4 - 10 timeline the sub-tropical jet will get very energised over the Southern US. That ties in nicely with an El Nino tropical signal, enhanced through passage of a tropical wave. Without any strong blocking feature to the north / far NE, and no scrambling of the upper level polar westerlies across the North Atlantic, we will be exposed to a poleward returning 200 hPa flow. That's not expected to last much beyond day 10, so chances are that an eddy will form in our locale setting up a ridge over NW Europe and trough becomes more slow moving to our west. Next phase of ridge development over NW Europe very much on the cards during the 10-21 day period. Stress that doesn't necessarily mean instant cold, and we could still get trapped the wrong side of a ridge for a time.
  21. 36 points
    Perhaps this thread will be better considering you seem hell bent on only ever posting the worst looking charts in terms of UK cold NAVGEM is perhaps the worst performing model currently on the planet so not entirely worried about what its showing. Given the UKMO's solid consistency, the GFS/GEFS moving towards the undercut option and the ECM also showing the undercut, GFS(P) is currently largely out on it's own for the time being. I wish we could see it's ensembles, could be the warmest one out of the bunch.
  22. 35 points
    This one is tight, that one is wrong .....etc etc etc none of them are ever right ....... that’s why we do this ! There can be little doubt that ec op has led the way on any initial attempt to bring deep cold in failing. That’s to do it’s the way it has never been happy to leave the upper low to just dissipate to our advantage and was always progressive in taking it further west and phasing with the trough headed in from the sw. has it been totally correct? No it hasn’t and it still isn’t now. Has it been more correct in respect of what happens to the weather in nw Europe? Yes it has. Anyway, the clusters will reveal later that there is definitely one which brings winter to w Europe days 9/10. How big is unknown but I haven’t noticed it thus far on the model getting this far west. All is not lost ....... still two weeks of autumn left ............ the overall mean pattern establishing for the end of vobember and into winter is one which has been trailed on the seasonals the Atlantic storm track is deflected into w Europe by northern/ n Atlantic blocking in this scenario, the uk will often lie in the broad battleground area ...... that looks like it’s coming for later this month but whether we end with Scotland or Hampshire being closer to the dividing line is the question. Any failure of low heights to our south will affect things and we know how fickle they can be ...... despite the current general malaise, ( which is totally misplaced) you know you will all be back later ............ that’s why your reading this now ................
  23. 35 points
    This quoted statement strikes quite a chord - looking in as I am from the outside of the thick panelled window of this particular utopian world The METO are professionals and interpret numerical model data, as well as utilising the considerable investment they have in tropical modelling - and make their own conclusions. As such they are completely divorced from any hysteria attached to weather preferences. One can of course dispute their own findings and conclusions based on other collective/ individual professional or amateur analysis and many rightly do this. Assuming that is, that such alternative offerings remain credible in themselves and designated such that the signals are derived from applied meteorological science, and so fit a realistic range of probabilistic solutions, and not merely as given lip service to try to fit an idealised one Sensibly, the Met are quite right to state things as they see them - and not instead on a regular basis feel obliged to please (and equally reassure!) their public of any perceived preferences they may have through making extemporaneous interjections in the interests of satisfying bias neurosis. Therefore as a consequence making a skewed mockery of probabilistic solutions (and making them redundant as a credible service provider at the same time!) On that basis, the idea of them trying to inject a little calm into the proceedings takes on a highly absurd quality if one stops to consider that the "hunt for cold" thread world is a very different planet - objectivity and non pre-occupation with ice age synoptics being deemed boringly alien and kill-joy because it spoils the entertainment and threatens a tribally protected species. So, with that in mind, some one-off attempted analysis before vanishing back to my own planet of Venus. Process of +ve momentum transport c/o CCKW driven tropical convection has been progressing through I/O and has spiked frictional torque tendency +ve with associated westerly wind burst anomalies representative of this around 30N (orange shading) The frictional torque response reflects the inflexion point of where additional westerly winds are added to the atmospheric circulation through progression of advancing organised MJO thunderstorm development - and convergence of macro scale wind-flows creates a turning force on the Jetstream and changes the direction of travel of relative angular momentum. So this increased +ve momentum transport and associated +ve frictional torque response registers immediately as a fairly significant spike in atmospheric angular momentum tendency - - A mechanism that leads towards programming the highly amplified pattern as advertised by numerical models within the atmospheric circulation, as according to the spatial poleward propagation of those +AAM anomalies over time. It is the lagged timescales according to this progression which provides the lead for further +ve mountain torque tendency in the extra tropics and sustains the amplified pattern through the majority of this momentum accounted for over the Himalayan ranges, setting up an extended Pacific jet and supporting phasing of energy into sub tropical flow (of which the models are presently balancing the equation over the medium term) The 'however' that is coming is that the adage is "what goes up must come down". Catalysts as they are for major pattern changes, there is no indication (to me at least) that the present tropical convection cycle matches those that have been a prequel to some of the classic early to mid winters. Meaning by this that the tropical signal aborting and losing amplitude sooner as seems currently likely than on those occasions implies a faster reverse scrubbing out of more sustained +ve momentum to follow that may, in turn, prevent the upscaling of the switch to an ever colder and colder pattern as some of the extended numerical model fantasy, filling the cracks of these pages, panders to. So a complicated sequence in terms of the lagged +ve momentum propagation which impacts the tropospheric/stratospheric pathway in the second half of November and reverse sequence to follow reflecting loss of the tropical signal which suggests greater polar jet flow in relative terms to the generally weak vortex and some relaxation, at least for a time, of -ve AO. This makes making any prediction moving forward sensibly erred towards caution this side of the glass window, and irrespective of any personal preference. Unfortunately the link to the consolidated Global Wind Oscillation plot has been down for some time to confirm precise position, But taking into account the relationship existing between an atmosphere co-operating well with an establishing Nino standing wave in the Pacific, as reflected by GLAAM retaining generally around a +1SD to parity... ….is suggestive and supportive of the GWO progressive into the El Nino attractor phase 5 (illustrative of +ve extra tropical momentum poleward propagation as discussed above) to be followed by an orbit through the Nino phases and depending on how far AAM falls thereafter, possibly returning to Phase 8/0. These phases within the tropical>extra tropical "mini ENSO cycle" being in simplest terms indicative of a 'waning' sequence during the major long term evolving +ve ENSO phase This forcing sequence roughly translates to the possibility of Scandinavian ridge and euro trough morphing into mid latitude Atlantic /UK ridge as the Pacific pattern re-amplifies somewhat (GWO Phase 8/0) following the relaxing of the +ve momentum phasing, switching some energy back into polar jet flow There is also a notion of argument to subscribe to, that the +ve QBO transition has already passed its optimum tropospheric/stratospheric disruption potential as it continues to downwell further, and moving ahead the onus becomes increasingly further on active amplitude tropical forcing resuming to re-stock +ve poleward +AAM transport processes and keep the tropospheric/stratospheric boundary unstable in the face of ever colder mid and upper stratospheric layers- and so manage to sustain blocking mechanisms at higher latitude. This occurred during early/mid winter 2009/10 under an emerging El Nino, bottom rung of solar forcing and being within -ve QBO phase and away from advanced westerly transition - but, notwithstanding polar stratospheric ozone distribution and concentration is (presently)elevated indicating the Brewer Dobson circulation between tropical and polar stratosphere is at least (currently) buoyant, the variables are not aligned the same this year. Any shortfall in all these respects renders the chances of a closer struggle between the upper and lower atmosphere, and a 'less warm' tropopause boundary which alters the complexion of the establishing Nino pattern evolving more towards a mid latitude European blocked one rather than one sustained long term between vectors at higher latitude to the NE and NW. Following what for some off us, away from the sole priorities of this thread, is a very pleasant and highly welcomed mid November week of weather to help save unnecessary heating bills, its certainly a cold outlook with perhaps some equally cold rain to match it and possible marginal wet wintry mixes for a few But whether it morphs into the freeze frenzy that is the utopian paradise the other side of the glass from where I am sitting, remains (at least in my humble opinion) yet to be seen.
  24. 34 points
    So - on the cusp of the last third of November. Anticipated blocking pattern a certainty for the week, and we will see all parts cool down significantly. What of the turn into December? 2 interesting charts tonight: Calculated tendency is around half way through the descending cycle - with an interesting hiccup just visible in the last few days. A predicted surge in westerlies in the western pacific may possibly serve to prop up the descending cycle a bit and prevent too deep a dip and overall we are looking at relative AAM in the medium/high category with most of the western momentum being experienced just north of the equator. This should help undermine sub tropical ridges and encourage the jet to remain further south than normal Conclusion? The pattern has to relax: but I'm pretty sure it wont relax all that much. High atmospheric AAM at the equator has to be balanced by a reduction of momentum at higher lats - and this means a weak jet overall, a tendency for blocks to hang around and certainly no signal for an atlantic return. The models are picking up a retrogressive signal in the long wave pattern so the high will drift westwards through the week, but I don't think it will sink. The downside to this descending AAM phase however will be that the trough may struggle to undercut fully - there just isn't the oomph in the supporting pattern to force it through so the EPS signal for 10 days time looks about right and the south may experience much milder air in 7 - 10 days' time than many on here will like. However - what about mid December? Next surge in GLAAM will occur on a base that is already fairly strongly positive provided the trend for decent westerly windbursts in the pacific continues. Let's assume the pacific stays lively....what will this mean? Another torque cycle, probable forcing of the jet on a SE axis through the US and a signal for a return of a scandy height rise as the atlantic trough is pushed through. Colder air in place...lower sun....high pressure over Greeny/Canada already in situ - link up possible to scandy? Winter then on its way.
  25. 34 points
    Superb outlook now - Scandi High - chance of snow, then retrograde to iceland with a reload from the NE - Finally ECM churning out the kind of charts that the UKMO would have done if it had run past 144- Cant really see how anyone can be critical this morning when we normally are ramping up the zonal westerlies now!
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