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  1. 95 points
    Good afternoon gang ,its nice to be back reading all the posts again ,although i have been lurking .(Thanks to all friends on here for my much appreciated messages over the loss of my wife recently ,THANK YOU ALL ) .Its great to see that the charts are showing some Winter weather , really warms the cockles of my heart .And its the charts which keep us interested not always showing us what we want ,and i,m certain that over the coming winter there will be Prozack moments and of course STella times ,so with the Meteorological Winter looming we can look forward to 364 roughly Runs of the good old GFS ,182 of the ECM , AND HUNDREDS OF OTHERS .Looking around the Internet back last year i looked at many weather forums etc ,and found that ours is by far the best and most interesting around .In my next post i will stay on Topic ,just wanted to start with a light Hearted post today .Let the hunt for Winter Synoptics commence ,Curtain twitching ,hiding behind the settee etc ,cheers gang ,.
  2. 77 points
    You know what - I havent seen 1 hopecast on here. People have put all their points of view across in a pretty good mannor- infact its been pretty good debate. The only post that sticks out a mile as pointless is the one im quoting...
  3. 73 points
    Still coming slowly off a cautious fence Long term total global atmospheric angular momentum trends can tell you a lot about pattern changes due to the effects the rises and falls in global wind-flows have on jet stream patterns. Total AAM refers to the net balance of easterly and westerly flow in the atmospheric circulation and the outcome tells you which direction the atmosphere is presently headed and which has initiative forward momentum Latest levels, assisted by a second tranch of eastward moving tropical convection since October has taken total global AAM back to parity, with even a hint of peeping a head above the parapet. This is to be set as disconnect against the negative (easterly) La Nina base state. Its no surprise that the sometimes pausing, but still steady upward trend overall, began from early October and why the pattern has been increasingly amplified over this time The importance of these feedbacks keeps being stressed repeatedly I know in these posts, but they are very important in terms of recurrence patterns that can give a good insight into how future patterns may play out. On the basis of the seasonal wavelength cycles spoken of again yesterday, the start of the winter (like any other season) is one of those especially important times when trends within the layers of the atmosphere can be especially augmented by natural seasonal wavelength cycles. Behind the rises in total AAM is continued buoyant AAM tendency as a result of positive torque mechanisms which are programming swathes of amplification poleward. This begins in the tropics c/o of the MJO cycle and propagates to the extra tropics and then from the latter c/o mountain torque into the stratosphere to sustain a destabilised profile. The momentum being created is starting to assure a cold pattern persisting longer and longer through December and slowly cancelling out cautious notions that the traditional base state might interfere and de-amplify the pattern in the ways described previously. As a consequence of the atmospheric flux, the Global Wind Oscillation (a representative plot of rising or falling AAM and global windflows) has continued to stretch its Phase 4 amplitude and enlarge the disconnect with La Nina. In synoptic terms, the implications of this are for an upper flow into Europe that looks likely to continue to be somewhat flat against the Atlantic ridge and troughing to the NE(hence some of the apparent stubbornness for breakaway lows heading from upstream to deconstruct and take optimum southerly most tracks each and every time). But with the upstream +PNA pattern assisting split flow it continues to favour the angle of the jet stream to be on a NW-SE trajectory, its set well for increasing upper cold air in tandem with surface cold to become more and more in situ and increase the possibilities of surprise more widespread snowfalls popping up more and more as time goes by. This leads to the extended period. In December the NAO has a low relationship in its response behaviour to the state of the polar field (the AO) However this starts to rapidly change as New Year arrives and the relationship, as such, consolidates much more tightly in January. Hence another aspect of this crossroads theme referred to so often. The feedbacks in process are starting to suggest with a bit better confidence that lagged effects of these amplification programmes will help prime a cold pattern to sustain or recur heading into the New Year. Assuming the atmospheric circulation doesn't deviate much from the present (and in this respect its still necessary to monitor AAM as tropical convection returns to the Indian Ocean as a potential fly in the ointment), then the effects of seasonal wavelengths bring those height rises to the NE into the equation, and the implication of this is to repress the Atlantic ridge, with less mixing of milder air in trough disruption occurring and better and better chances of snowy undercuts.
  4. 68 points
    Afternoon All - A frantic few days on here with pages & pages of posts flying through in a matter of hours- I think we have 2 main discussion points at the moment- 1) The short to medium term prospects for the UK covering the next 10 days 2) The medium to long term thoughts on December & Winter as a whole... Short term then whats the bad news- well is there much to be frustrated with? only the fact I guess that the megasnow charts that appeared for a day or so have been moderated - Thats because even though the overall pattern is near as damn it identical - the timing & phasing of the jet + low pressures has been modified just slightly to reflect a slightly slower progression south of the cold air- The initial prognosis for the cold was always Thurs PM into the Eve- well now potentially the GFS just holds this off another 12 hours due to a track of that low not being as efficient for cold air advection alligned to the UK- This aside though the potency of the Northerly looks pretty substantial- at this early phase of Winter if you can get the -8c line to the South Coast then your doing very well- We deliver that with other areas of -9 & possibly the magical -10c The flow looks very unstable to me - bringing a rash showers across the usual places exposed in a NNW flow - NI included- perhaps some of the posts & general frustration today has reflected some IMBY desire for snow - well thats life. * In terms of more organised bands of snow I suspect the models havent quite resolved the finer detail yet so I believe we will see some kinks & troughs forming ... It will be all about timing and intensity as that whether areas further south can get any snowcover ! For Scotland & parts of the North /NW sustained snowcover looks a possibility from overnight Thurs onwards for at least 4-5 days... 'The slider lows' - personally I love the name - a potential again for some snow pushing across the UK ( mixed into rain ) for the western portions - The models havent got a grip yet of how these will develop- they are beginning to see the Energy & rough location of development - however angle of the jet is very much up for grabs -indications being the first system will slide past the UK- or possibly into the west, keeping the UK on the very cold side of the jet- although some runs do bring a higher chance of snow across the UK with a shallow system & acute angle... after that it is usually difficult to keep the jet attenuated enough for 2 sliders but we will see... * Post next weekend & more long term the prospects for sustained cold is highly probable- The starting point would be - how many times in the last 2-3 weeks have you seen a return to normal NH zonal conditions past day 10- the answer is probably very low.. From the top down we are seeing the GFS continue to show no coherent downwelling of any meaningful positive westerly winds, with infact a second bout of negativity building in the 10-30 HPA layer at day one 12 -16 The models have been a bit flip flop with this so its not a given- However even with the possible bonus of another reduction of the zonal wind the models persist with the disturbed hemispheric pattern. The H5 anomalies show considerable blocking across the Pacific / pole / Russia & a segmented vortex mostly languishing across the other side of the globe- Whats key here & the reason why we are seeing the models choose the 'non toppler' scenarios is because of how I believe the energy within the zonal wind is being distributed- when we have a high Westerly phase of the zonal wind the Easterly component ( moving west to east ) is very uniform & theres minimal deviation away from that direction- IE minimal poleward vector- In reduced phases & the highly desirable negative phases you have maximised poleward & equatorial vectors & no Easterly Vector- So for December in General we have a zonal wind that kicks on around 30-40 M/S - where currently its heading to around 10 M/S- Thats where all your Easterly progression has gone... Factor in the weak La nina base state which if you use the general analogues you will find a pretty good match for a negative December AO & cold in the mid lattitudes- With that in mind the odds of a below average December are high - with H2 of the month of particular interest as the Russian high starts coming into play potentially backing the pattern up even more... so.. for a change increase your expectation towards cold for the remainder of the month-blocking peak 9th Dec - with maybe a short relaxation before going again towards the 15th ish on the run in to the festive period.... S
  5. 67 points
    Afternoon All I guess a few of you/us are wondering whats going on with the weather this weekend & into next week... Strange, almost 'texbook' cold charts appearing in the models & actually landing with some degree of accuracy.... Well like many - you are probably wondering if its a precursor to the rest of the winter or a lucky double 6 roll in November.... Based on the information at hand I would say the nina base state forecasts of mild westerlies into december & throughout are going to be wrong & on very shaky ground - Looking at the current picture & the run up to the start of the winter season I commented on TWO about NW winters getting more extreme - The NOAA data for AO & NAO show the modes of these metrics becoming more & more diverse & when in a particular phase ( whether that be pos or Neg ) so the metrics would be topping / bottoming out at at close on record breaking levels - The whole post was in reference to the M.winter theory from IBrown To underpin this ( but without the data ) in the last 15 years we have smashed the AO record at both ends so many times - months like Dec 10 / Mar 13 spring to mind- but also the extreme mild ones as well ! However also in the post was the fact that steadily the incidence of Negative months had reduced in favour of more positive ones- so with Heinsite the M.Winter theory carries some weight but poorly communicated without all the facts- What also has become Crystal clear is the fact that the M.Winter or whatever you want to call it could be under attack by more front loaded cold winters especially when the total atmosphere favours a negative state of AO/NAO with winter 17/18 being just that- Post M.Winter ....? The fallout from the polar ice melting is creating massive impacts on the way the jet behaves in November in particular - The fuel needed to ignite the jet is simply missing in action - probably due to the self perpetuating feedback loop that develops at the same time as when the jet & vortex should be positioning over the pole ( Early Nov ) The chart below shows the current surface temp anomaly for November up until 22nd The green scaling is about 7-8c the orange & red 10-15c vice versa blue about negative 5-10 If you look close at the map the dividing line is generally alligned to 60N where the jet is usually located. We have a reducing in measured gradient by around 15-20 degrees > this essentially acts as a neutraliser on the jet- for which we are now feeling the benefits. This troposheric lead feedback is a far larger beast than El nino or La Nina - it covers the entire space North of 65N & a large part of Russia - It certainly needs a name so I am calling it this - Calido el hielo !! What we have is a troposheric feedback loop that feels lime it can run disconnected to the strat until the anomaly becomes muted but the inevitable increasing gradient as we had further into December & the strat can work its way down... So a watch out for future Novembers that Calido el Hielo may be creating more blocked extreme ( warm or cold ) Novembers.... Moving back to the hear & now we are in a rare situation, one of only 6 occasions since 1979 in winter ! of these 6 the EQBO years being just 2. 1st Jan 85 ( Front loaded EQBO ) 20 Feb 01 - So whats infront of then ? A troposheric induced stratospheric splitting event - the net being a massive deceleration of the zonal wind lagged about 10-15 days later. I would go with our splitting event to be dated 29th NOVEMBER !!!! ( This is why I kept referring to 31st Dec 84 in the model thread ) Here was the Jan 85 & feb 01 charts & the associated stratospheric response ( lag back down ~ 10-15 days ) Then importantly the following months anomaly After +10days lag * The key notes here are that the troposhere is primed for polar blocking with a core towards Greenland- Also low euro & Azores heights present... Now, Taking our event to be 29th of November we should see an immediate stratospheric collapse of the zonal wind & from about the 4th-5th & The blocking anomalies to be present from anywhere around the 8th onwards- Lets look at this mornings outputs - these are GFS based & depict a total collapse of the zonal wind - with this depiction being the daddy - showing a -35 M/S hit on the zonal wind which is a reversal at 10MB .... Jan 85 Merra data shows a reversal down to -15M/S Feb 01 shows bottoming out -3M/S So this is why the GFS / ECM are spewing out all this blocked data for first / Second week of December- Based on the science of the lagged troposperic response the 6-12th Dec will be peak for blocking & subsequent cold UK potential with Greenland being the favoured location a Below ave December / Front loaded winter is odds on favourite for me with a high probability of some very special charts appearing! fingers crossed.... Best S
  6. 61 points
    Having followed all the output and read all the posts these past few weeks I thought I would make my first post of the winter. A few points I wish to raise. 1. Current output does not suggest a major cold spell. 2. The NW,ly this Fri/Sat will bring snow showers to the favoured locations and may even spread SW through the cheshire gap towards even London. However many locations will remain dry and sunny with max temps of 2/3C. The snow showers will not be as extensive as some have suggested. 3. Beyond NW,ly the jet stream does appear to be taking a NW-SE track so slider low pressure systems bringing a risk of snow is possible. Remember though your location dictates whether a model run is good or bad based on the track of the low. 4. The risk of cold and snowfall from this pattern looks likely to extend into mid Dec. However I fear beyond this a return to a milder weather, flatter jet stream, lower heights to our NW/N is likely towards xmas. Love to be wrong. So a summary is this is much better than last year but certainly no repeat of 2010!
  7. 59 points
    This thread is a mix of analysis and the occasional toys out of prams. We’re not the BBC giving a forecast . And the ups and downs and some of the melodrama and humour in here are part and parcel of the success of these forums . Coldies in here are not your average members of the public , the majority are snow lovers who are passionate and so no I don’t want a dry humourless emotionless thread just discussing the track of a low. Yes of course you want to see some analysis and there’s lots of that in here, but at times it’s going to happen that we might lose it and and have the occasional moan.
  8. 59 points
    So sorry to hear that mate Dont want to clutter up this thread but im sure i speak for everyone in wishing you the very best and hope you will be ok.
  9. 57 points
    I know it's an absolute disgrace and a complete waste of public money when they refuse to tell us what we want to hear,
  10. 56 points
    we have an SSW forecast- a Sudden Stratospheric Whale....
  11. 55 points
    WINTER 2017/18 REPORT No. 3 WITH DECEMBER 3rd INPUT PART 1: As this will be a long report (even by my standards!) I am splitting it into to two parts. Part 2 will probably be posted much later on this evening. It will include an updated analysis of the Arctic, European and Asian snow, ice and temperature profiles. A REVIEW OF THE MODEL OUTPUT OVER THE LAST FEW DAYS Another extraordinary week in the volatility of the model output and continuing uncertainties even for later this week. In response to all this the general mood on this forum has gyrated from agony to ecstasy and back again – at least amongst many of those seeking cold and particularly snowy weather. I broke one of my golden rules during the week and produced a one liner with a single chart while an ECM run was in the middle of being churned out. The comment proved pretty inaccurate on the very next chart! I’ll endeavour to leave the instant reactions to others but for any cold and snow starved “coldie” it’s so easy to get sucked into the frenzy. I shall stick to these occasional (perhaps weekly) long reports with some shorter interim posts when I feel that I can add something to the overall discussion which hasn’t already been covered. There is much still to be decided in the short term. The period around Thursday to Saturday, December 7th to 9th had been identified a few days ago as being critical in terms of determining the direction of a broader pattern change. Most of the models (including the big 3) swung at some stage between a longer lasting northerly, a much briefer northerly and no northerly at all for the end of this week. Just as one or more of the models moved in one direction, at least one other moved in the opposite direction. Then about 2 days ago it at last looked like we had some general agreement on a decent Arctic outbreak towards the end of this week. There continued (and still does now) to be considerable variation on its longevity and its potency. For several days now, most of the models have shown a LP crossing the country from south-west to north-east on different paths and at different strengths with the northerly sweeping in behind them. Just small variations in the path, speed and intensity will make huge differences in terms of how much precipitation there might be, how much (if any) cold lies ahead of the system, how quickly the cold moves in from the north, how much it might undercut , how much snow there might be and how windy it might get. Several GFS runs showed the LP deepening rapidly and crossing the centre or south of the UK. At one stage it showed an intense LP in the south North Sea which, if it verified, would probably have led to a substantial tidal surge with high Spring tides due mid-week and still high tides during the critical period. I did a short post on this potential threat on page 81 of this thread. Fortunately for those in the firing line, the intensity of the LP has been considerably downgraded. Just ahead of the Arctic air stream the south in particular, is likely to see some pretty mild conditions. Whatever path the LP takes (unless it goes much further south) it has really looked like rather too much of this mild air would initially mix into the system which would almost eliminate any “early” snow prospects over lowland areas (at least south of the Scottish border) ahead of the Arctic air arriving. Again, several GFS runs showed much lower temperatures at an earlier stage with considerable widespread snowfall. Many on here (including me) did get very excited about this prospect but a number of the wisest posters (and perhaps also several who are more pessimistic or even “warmies”) did warn us to manage our expectations. Even the GFS (at least at the time of writing this part of my report – it’s currently 1030 with the 6z output still rolling out) has moved away from the early snow scenario. Much will then depend on how quickly any mild air is forced away by the surge of Arctic air and the depth and intensity of this incoming cold air and also how long the LP hangs around close enough to our east to produce more widespread wintry precipitation and not just wintry showers close to exposed western, northern and eastern coasts. Another factor will be whether there are any troughs or minor disturbances (even the outside chance of a Polar Low) embeded in the northerly flow. At this stage most of the potential for “widespread” snowfall for next weekend has been downgraded by GFS and the other models, several of which never really showed it in the first place. Obviously there is still huge uncertainty and things can easily change again even within the 24 to 48 hour period particularly in terms of snow events. Nobody can seriously rule it in or out at this D4 to D7 range given the current set up. It still looks like there will be some snowfall but how much of the country will see it? Stay tuned to this forum all week for comments and analysis from our regular (and occasional) posters for the latest developments! LOOKING FURTHER AHEAD Things still look very interesting going beyond next weekend and current uncertainties continue which is hardly surprising given that the next few days are still to be decided. There seem to be far greater than usual complexities. The main overnight runs have shortened the direct northerly to just several days. The GFS and ECM 0z runs both continue to show a pretty cold pattern even though the jet stream appears to strengthen considerably with a lot of energy moving over the top of the Atlantic HP and flattening it to a lesser or greater extent. With a likely north-west to south-east jet and the UK remaining on the eastern side of it both models in their own way show a succession of LPs moving down over the vicinity of the UK and engaging some of the colder air remaining over us. The “potential” for snowfall almost anywhere in the UK will continue as long as this broader pattern is maintained. We cannot see what the UKMO shows beyond T+144 and their longer range outlooks have varied somewhat in recent days. Several models like GEM as well as a few of the GFS and ECM ensembles have gone for a much flatter flow with a much more direct jet stream pushing almost all before it. Let’s have a look at some of the different possibilities predicted for the jet stream using the control run and several perturbations from the GEFS ensembles from today’s 6z run which has just rolled out (currently 1145). GEFS 6z on December 3rd Jet Stream Predictions: T+0: Control – current: T+144: Control Perturbation 5 Perturbation 7 Perturbation 13 T+180: Control Perturbation 5 Perturbation 7 Perturbation 13 T+264: Control Perturbation 5 Perturbation 7 Perturbation 13 T+384: Control Perturbation 5 Perturbation 7 Perturbation 13 I selected these particular perturbations as they show quite (or very) different outcomes and routes of getting there. The time periods chosen are to show the position around the start of the so-called critical period for a possible pattern change at T+144 and the interesting changes just 36 hours later at T+180. I found more variations around T+264 and towards the end of the run at T+384. I will not comment on all the detailed charts (until part 2 of this report), they are simply there to show the significant range of variations going forward after around T+144. One of the causes frequently cited of a strengthening jet stream is the North American temperature profile with the conditions down the eastern side contrasting to the adjacent much warmer Atlantic Ocean. The greater this contrast, the greater the likelihood of establishing or maintaining a stronger jet stream. It is much more complicated than just this and this is in danger of getting rather above my pay grade and technical ability, so I shall keep it simple for my sake as much anyone else’s! In recent winters we have got very used to seeing the jet stream frequently roaring across the Atlantic and blowing away everything in its path, although last winter saw long periods of MLB but very little in the way of any deep cold (just surface cold at times). This winter does seem to offer something rather different. The strong and quite persistent Pacific and Atlantic ridges have not only caused significant MLB but, unlike last winter, have so far caused the jet stream to buckle leading to some greater amplification and a much more meridional pattern. Now let’s have a look at the North American temperature profiles for the same time periods as I used for the jet stream predictions. I could have taken the temperature predictions several days ahead of each jet stream chart as there is usually a delayed response from temperature changes but the five time periods from T+0 to T+384 should give a rough idea of the predicted changes for each model run. Again I shall comment on these in part 2 of this report. GEFS 6z on December 3rd 2m Surface Temperature Predictions: T+0: Control – current: T+144: Control Perturbation 5 Perturbation 7 Perturbation 13 T+180: Control Perturbation 5 Perturbation 7 Perturbation 13 T+264: Control Perturbation 5 Perturbation 7 Perturbation 13 T+384: Control Perturbation 5 Perturbation 7 Perturbation 13 GEFS 6z on December 3rd 850 Temperature Predictions: T+0: Control – current: T+144: Control Perturbation 5 Perturbation 7 Perturbation 13 T+180: Control Perturbation 5 Perturbation 7 Perturbation 13 T+264: Control Perturbation 5 Perturbation 7 Perturbation 13 T+384: Control Perturbation 5 Perturbation 7 Perturbation 13 I think that this will be the first and last time that I do such a detailed overview with so many different charts! Apart from the time to prepare and post them, it is difficult to look at all the changes and comment on each run. Hopefully the end product will have made it all worthwhile! Part 2 to follow this evening – quite late.
  12. 54 points
  13. 53 points
    Always worth taking a lead from the GSDM (Global Synoptic Dynamical Model) at all times in my opinion, but in the context of current discussions then NWP may be especially likely to oscillate in the period ahead, both with the tropospheric pattern, but also across the polar field in terms of the AO benchmark. Each post for quite some time from my own point of view has, in anticipation of possible outcomes, focussed on the upsides and then the downsides in terms of where atmospheric angular momentum is to be led during the upcoming transition of the MJO (tropical convection) from the current wave to the start of the next one. As stated yesterday, definitely coming off the fence with this one, though still stressing the need, as expressed in each post, to monitor how far AAM falls from the maximum disconnect with the La Nina base state currently happening - to the cyclical ebb as the tropics re-set patterns through the mid period of this month. The Phase 4 Global Wind Oscillation (at present) orbiting to Phase 8 and then in turn back to Phase 4 (and not heading back into Nina Phases 1,2 and 3) will underpin the bullish notions that the atmospheric circulation wants to continue to pave the way towards an even colder trend heading towards and into the New Year as the North Pacific ridge and Canadian vortex configurations relax sufficiently to allow height rises to the NE but without too much northern branch of the Jetstream to spoil deeper sources of upper cold air advection to head south-westwards across the North Sea. We could espouse the easterly of late December 2005 as an example of this sort of thing, but not at face value in terms of "intensity" (or otherwise )of cold air and snow distribution necessarily, or indeed replica precise timing to take too literally. It still has good purpose for illustration use though of how things could conceivably evolve in principle. I expressed slowly growing confidence in this sort of evolutionary possibility to NE heights yesterday. However the UK initially fares, the jist of it is that a deep source of cold air would be in place in this scenario that is highly unlikely to move very far in these circumstances and sets up a very very interesting January scenario Still with the attached caution caveat that prospects of a fall back in AAM sufficient to take the GWO back to Phases 1,2 and 3 is becoming less likely with each passing day of positive data - *should* this occur then the more traditional La Nina pattern would re-surface which implies the North Pacific ridge and Canadian vortex combo not retrogressing and in this way pressurising the polar jet and neutralising an -AO profile. At the same time, the Azores/Atlantic ridge would be ascendant at the expense of greater influence of heights to the NE and too much energy transport to the N to allow the pattern to back deeper cold air advection westwards Its highly possible that the models will show especially erratic trends on the way to the final destination, notwithstanding that as posted earlier on this thread, the GEFS suite is pointing a way towards the upside scenario in the extended period. But as a precaution anyway, in terms of keeping a sanguine open mind to keep enjoying the ride, I would suggest not allowing any model vicissitude to correspondingly engulf human emotions into equal vicissitude. On that basis best also to take AO/NAO forecasts with an equal pinch of salt - these will simply reflect the swings of NWP, and equally, ensemble suites The theme is the same old for me - the signals lead the models, the models don't lead the signals. Highly interesting start to the winter (for a change), if you don't let every model suite overwhelm you, whichever way
  14. 52 points
    So just to finalise my thoughts / comments on the 12z suite.. We often find ourselves in Winter with an atlantic high ridging into the pole- & the longivity of that wave / ridge remaining in situ before getting flattened ( as well as the final height ) is directly related to the general consistency & strength of the pacific jet - because after all thats what normally comes barrelling over the top shearing the top of the highs- Its also important to remember that at this usual point in late November the heights over pole @500MB are generally sub 516DAM & this more often than not coupled with a strengthening zonal wind means the tip of the ridge usually gets to the southern point of greenland before the westerly directional flow is already getting to work on moving everything East - So on a 'typical' Early winter chart we see a Northerly toppler - Day 1 we have our ridge & 4 days later its been flattened- look at the pacific jet blasting away- no sustainable meridional flow going forward , just a temporary interuption to the sinuous flow... Also notice the persistent low heights over the pole - Now look at the starting point when the second wave of ridging occurs at 120- * The all important residual +VE heights over the pole consistent with the original -4 AO ( which is why people like me / Bluearmy always refer to it ) * The fairly strong but still attenuated pacific jet & weak subtropical jet - with this attenuation there is now an ripple in the jet over the states which is a sharp +PNA pattern creating a big 'dig' of cold air in the NE is, that dig then supports the returning flow upwards back towards the pole @144 Post this ( from the GEM ) @144 the entire hemispheric jet is rippled & attenuated creating a 'weak' easterly component in terms of a zonal wind. Not only this but the stratosphere is decelerating at the same time - With the detached tropospheric negative anomaly almost upwelling with time- This shows a decelerated zonal flow around the pole So all the fall out means that based on the starting point of T96 & the rupture to the jet - combined with the persistance of higher heights over the pole makes any eastward progression of the jet a lot Weaker than normal- & with considerably more North / South components - more so than westerly ( moving East ) Its a rare scenario - but based on the starting point at day 4 the continuation of Cold is odds on favourite, maybe not quite to the magnitude of the ECM in terms of outright blocking, but solid in terms of the pattern remaining blocked & slow out to day 10- I would go with the final solution being less extreme than the ECM but overall closer to the ECM than the flat GFS .... best s
  15. 51 points
    AN APPEAL FOR SOME SYMPATHY AND RESPECT TOWARDS THE MODERATORS Before I start working on my next weekly report, which will appear late tomorrow (Sunday), I must get something off my chest and I feel that it might be better coming from a poster/reader like myself rather than from a moderator. I strongly feel that some posters on this thread need to understand and respect what Paul and his team of moderators have been requesting repeatedly during the last couple of weeks in particular. Like the vast majority of posters and readers, I love cold and snowy weather and I can get as excited as anybody with much of the recent output but we must remember that this is a model output analysis and discussion thread. Yes, that does overlap with many related topics but it’s not really that difficult to know what is completely off topic. Just ask yourself, is what I’m about to post related to something about the model output. Think about the audience and what they expect to see on this type of thread. For example, posting a chart (or charts) showing what the GFS 6z output shows is fine. Ideally, this needs to be backed up with at least a short comment like how it has changed from the previous run or how it compares to other model output or how it might result in a particular type of weather or a more general view about a perceived trend. This can include short term events such as potential snowfall when it bears a direct relationship to the model output. It does not include posts which only ask “will it snow in my location?” Even worse, some of the posts contained some quite nasty one liners about so and so getting the snow while they will miss out. Whether this was purely banter or something more sinister is not really the point, those comments simply do not belong on this thread. There are other threads for such things. Sometimes we see some highly disrespectful and quite rude contradictions. If you really disagree with another poster's view(s) then politely explain why with a short and reasoned analysis or comment if it's relevant or send them a PM. I really sympathise with the moderators who have had their work cut out in deleting or transferring unsuitable posts. This is NOT a game of seeing just what you get away with. I know that sometimes one feels that certain questions about the snow will only get answered if it appears on the model thread but some of the other threads have also been far busier than usual and the moderators and others from the NetWeather team do take the time to answer genuine questions. If posts consistently appeared on the correct threads then the usage and activity on those threads would increase accordingly. One can also send a personal message to any poster and many of these do get answered and now we have the “sticky note” option too. I was away on a short business trip from Thursday until today and I had to use my laptop instead of my normal desktop computer. The signal wasn’t very good and I really struggled to catch up with the latest analysis. Wading through so many posts that didn’t really belong on this thread made it particularly tough going. I skimmed through and only stopped where I saw a particular poster or where there were quite a few likes – which is not the best way to judge it all and I’m sure I missed a few really good posts that were buried in there somewhere. One of the real positives about this thread is the huge diversity of posters. There is a whole spectrum and wealth of skills and knowledge from professionals, experts, scientists, technicians, many of the NetWeather team and also keen and/or experienced amateurs through to beginners and those wishing to learn more about this wonderful subject. We get some amazing reports on what is driving the models from the likes of @Glacier Point @Tamara @Catacol to name a few and we get great analysis of what the charts show and why with some thorough explanations from a whole hosts of posters. A few, like me, usually prefer to do a longer analysis looking at particular aspects of the subject. All of the above is what this thread is all about. So, please let’s all make an effort to keep things on track so that we can all benefit from the experience. Finally, things seem to be rather better this evening - perhaps as @phil nw. says the regional threads are being used for the forthcoming snow event.
  16. 51 points
    WINTER 2017/18 REPORT No. 1 WITH NOVEMBER 22nd INPUT Hello everyone, I’m back! I have been following all the activity on this thread for a few weeks and I wasn’t intending to post any more due to major time constraints but I’ve been sucked in again! Last winter I produced weekly full reports as well as various ad hoc posts. These were often very long (too long for some readers) and took many hours to prepare. This winter I am busier than ever running my business and I have just decided to produce very occasional posts. These will not be as extensive as before and I will cover only a few of my regular features. I will endeavour to avoid repeating some of the general model output, charts and comments which are given excellent coverage by many posters on here. Instead, I will focus on particular “model related” topics and try to add something to the overall discussion. Like many of you, I am a serious “coldie” but I do attempt to provide some balance in my comments. I have noticed numerous comments regarding the lack of any significant cold and not low enough 850s despite some excellent synoptics. Today, I will examine this issue in relation to the current model output. As I always say, I am certainly not an expert although I have been a keen “weather enthusiast” for well over 50 years. Some Great Synoptics but Little Significant Cold Showing – Why?: We have seen some very promising output on many recent model runs but a real lack of low enough temperatures to produce little if any lowland snowfall. The surface and the 850 temperatures are not really low enough. There are a whole host of reasons for this. This includes, the source of the cold and depth of the cold at that source; how long the airstream lasts; the modification of the airstream over its journey to our tiny country and the length and direction of that route. The time of the year – late November is not deep mid-winter. High sea surface temperatures. Near record low Arctic sea ice extent and well above average temperatures there. No deep cold over most of Europe. This list is by no means exhaustive. I shall go through some of these now Selection of Current Model Output for T+144 (Tuesday, November 28th): PRESSURE: UKMO ECM GFS GEM 850s: UKMO ECM GFS GEM These generally show Arctic airstreams of sorts. Some more direct than others. The 850s over much of the UK are mostly around -2 with a few closer to -4. Today’s ECM 12z (rolling out as I’m writing this) looks great again but is still struggling to get to -4. Even in the coldest GEFS ensembles (not shown), the lowest values are around -4 to -5 (several perturbations show this at T+144). I’m sure that there must be some colder ECM perturbations. If the Arctic airstream lasted long enough and/or intensified, it is possible that rather lower 850s might reach our shores. Renewed bouts of Arctic incursions (or reloads) might also see rather lower values later on. In recent winters, even the seemingly more potent (albeit brief) Arctic incursions have struggled to deliver significant cold. Despite all this, I do believe, that with various factors falling into place, it will still be possible to see colder conditions. There have been very few examples of early winter (or even late Autumn) cold spells during the last 30 years but we only have to go back to 2010 to see that it is possible. That was of course an extreme example and the coldest and earliest start to a British winter since 1890. That might well have been a once a century occurrence but for most of the time the air arrived via a polar continental rather than a direct Arctic flow – so not a good comparison for several reasons (at this stage). Back in the 1960s and 1970s there were a number of early winter cold snaps with Arctic airstreams and quite widespread lowland snowfall(s). These were all from memory – amazing how I recollect these but my memory of more recent events is poor these days. Let’s compare several of these to the current (predicted) colder spell. PRESSURE 19/11/1962 30/11/1965 7/12/1967 29/11/1969 850s 19/11/1962 30/11/1965 7/12/1967 29/11/1969 These are all taken from the excellent “NCEP Reanalysis Archives” website. For those of you who have not visited it before, here’s the link: http://www.meteociel.fr/modeles/archives/archives.php?day=1&month=12&hour=0&year=1967&map=7&region=&mode=2&type=ncep You can select any date back to 1871 and set rolling 15 day periods. All these earlier examples were at times when the Arctic sea ice extent was almost twice the current levels. There were generally rather lower 850s compared to today’s but not hugely so. Arctic Sea Ice News and Analysis: The last full monthly report was published on November 2nd. This shows that the Autumn recovery in ice growth has been slow and the overall ice extent is currently very close to the record low levels of 2012. Here’s the link for the latest report and updates: http://nsidc.org/arcticseaicenews/ These charts shows the current extent of the sea ice (as on November 21st) in relation to the 30 year means. Source: National Snow and Ice Data Center (NSIDC) Arctic Current Sea Surface Temperatures (SSTs): SSTs November 21st SST Anomalies November 21st SSTs UK November 21st The anomaly chart shows that there is a wide area of open water in the Arctic with well above surface temperatures. The SSTs need to be below the -1.5c threshold (the purple colour). Sea water will start to freeze when it is below -2c but that is for normal salinity. There is slightly lower salt content in the Arctic (mainly due to ice melt) and the threshold is nearer to -1.5c. There are some areas with SSTs well above freezing and the current anomalies are widely 4c to 6c above average and up to 8c above in places. These higher SSTs are a legacy of the 2015-16 winter when the Atlantic Jet Stream powered well into the Arctic for much of the first half of winter. This shifted much warmer than average currents right up to the edge of the ice sheet. This strong anomaly has persisted for 3 years and is exceptional and comes on top of the already generally warming Arctic. Unless the SSTs reduce substantially, the anomalies might be carried through to next summer and into a fourth winter. There is a small area of the North Atlantic, mostly south-east of Greenland with a negative anomaly. Northern Hemisphere Current 2m Surface Temperatures: GEFS ens mean 12z T+0 - Current GEFS ens mean 12z T+144 for Tuesday, November 28th: If you compare the current and T+144 charts the main area of deep cold is over Siberia, with less widespread and less intense cold in North America. There is little change over Greenland and in most of the Arctic Ocean. Quite honestly, there is far too much of the Atlantic and Arctic to our north that is warmer than average. It will be difficult to see much deeper cold heading our way on a direct Arctic airstream during at least the next week or so. Svalbard Daily “Maximum” Temperature Forecast for 10 Days: Here are the links to the 3 Svalbard stations that I monitored last winter together with a summary of D1, D5 and D9 values: Central/West Svalbard – Longyearbyen 28 m asl: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/forecast.pdf November 23rd -6c; November 27th -7c; December 1st -4c. North-West Svalbard – Ny-Alesund: http://www.yr.no/place/Norway/Svalbard/Ny-Ålesund/forecast.pdf November 23rd -6c; November 27th -10c; December 1st -5c. Central South Svalbard – Sveagruva: http://www.yr.no/place/Norway/Svalbard/Sveagruva/forecast.pdf November 23rd -5c; November 27th -12c; December 1st -9c. Please note that the links above will update automatically at frequent intervals throughout the day. They are the Norway met office’s predictions. We need to be aware that these are only a forecast that is subject to change and I am told that the Arctic surface temperature forecasts are not completely reliable even at quite short range. The temperatures were above freezing for a week or so earlier this month but they, at last, fallen well below freezing for the last week or so and are set to remain at these levels for at least the next 10 days. Nevertheless, temperatures are well their 30 year means. To put the above figures into context, here is a link to the main Longyearbyen site: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/statistics.html Tabular view for temperature and precipitation per month Months Temperature Precipitation Wind Average Normal Warmest Coldest Total Normal Highest daily value Average Strongest wind Oct 2017 0.5°C -5.5°C 7.7°C Oct 23 -5.8°C Oct 25 27.4 mm 14.0 mm 18.9 mm Oct 24 5.1 m/s 13.2 m/s Oct 23 Sep 2017 4.9°C 0.3°C 13.3°C Sep 26 -0.7°C Sep 1 20.8 mm 20.0 mm 5.3 mm Sep 19 4.9 m/s 16.3 m/s Sep 23 Aug 2017 6.1°C 4.7°C 11.6°C Aug 2 0.2°C Aug 27 16.2 mm 23.0 mm 7.4 mm Aug 29 4.7 m/s 14.6 m/s Aug 16 Jul 2017 6.9°C 5.9°C 13.1°C Jul 18 2.7°C Jul 4 20.4 mm 18.0 mm 6.5 mm Jul 14 5.5 m/s 13.6 m/s Jul 14 Jun 2017 4.6°C 2.0°C 9.0°C Jun 11 -0.2°C Jun 5 5.6 mm 10.0 mm 1.9 mm Jun 17 4.3 m/s 11.6 m/s Jun 29 May 2017 -3.9°C -4.1°C 7.3°C May 31 -11.5°C May 9 5.3 mm 6.0 mm 1.7 mm May 15 4.1 m/s 13.9 m/s May 15 Apr 2017 -8.3°C -12.2°C 2.9°C Apr 29 -21.3°C Apr 1 6.2 mm 11.0 mm 2.5 mm Apr 28 5.5 m/s 15.0 m/s Apr 5 Mar 2017 -11.8°C -15.7°C 2.5°C Mar 14 -23.5°C Mar 18 15.8 mm 23.0 mm 2.8 mm Mar 7 5.6 m/s 15.6 m/s Mar 26 Feb 2017 -6.6°C -16.2°C 5.9°C Feb 6 -21.3°C Feb 18 45.4 mm 19.0 mm 10.6 mm Feb 8 6.5 m/s 21.0 m/s Feb 21 Jan 2017 -10.3°C -15.3°C 2.2°C Jan 16 -21.1°C Jan 31 24.6 mm 15.0 mm 8.7 mm Jan 19 6.3 m/s 17.9 m/s Jan 17 Dec 2016 -6.0°C -13.4°C 4.8°C Dec 21 -18.5°C Dec 8 22.7 mm 16.0 mm 3.4 mm Dec 20 5.9 m/s 24.8 m/s Dec 29 Nov 2016 -0.7°C -10.3°C 6.4°C Nov 8 -11.1°C Nov 27 58.0 mm 15.0 mm 41.7 mm Nov 8 5.7 m/s 16.5 m/s Nov 8 Oct 2016 3.2°C -5.5°C 10.1°C Oct 7 -3.8°C Oct 15 57.0 mm 14.0 mm 18.3 mm Oct 15 5.7 m/s 17.8 m/s Oct 8 This shows monthly means and actual highest/lowest temperatures recorded during the last 15 months. Svalbard has been seeing “maximum” temperatures often running at 8c to 10c above their long term average throughout most of the last 4 years. This is reflective of the warming Arctic and the near record low sea ice cover. Overall, it is not difficult to see why it is so hard to achieve prolonged cold and wintry weather from an Arctic airstream these days. Let’s see if the current synoptic pattern is sustained for long enough to achieve something more memorable. I do feel that the better route to cold, even in late November, is to have an Arctic or Siberian blast over mainland Europe and/or Scandinavia and then to import this cold into the UK with winds from either a north-easterly or easterly direction. I will looking for the Arctic airstream to veer into that direction and set up a pattern more akin to 2010. When I have time to write another report, I’ll look at Asian (well above average) and European (very little right now) snow cover as well as temperatures in those regions.
  17. 50 points
    If I may clarify a point here. I have absolutely no idea who are members of the so called "mildness" gang but I am certainly not one of them. It is no secret that I detest cold weather and I do so mainly for two reasons. Firstly, the imprint of 62-63 will forever remain with me and secondly, and far more importantly, as a vulnerable, elderly pensioner, and of course I'm not alone here, cold weather very much affects my health. But none of that is relevant as to how I approach the model output, which in my very simplistic manner, is based purely and simply on a meteorological analysis. Preferences and deliberate bias are no go areas.
  18. 50 points
    Casper the Ghost points the way at T96
  19. 49 points
    PLEASE READ THIS POST WITH EXTREME CAUTION! DISCLAIMER: I bear absolutely no responsibility for the contents of this post! The analogue charts that I refer to (later on) are purely to look at certain similarities between the current pattern and a "certain" earlier winter. It would be wholly wrong to conclude (or expect) that earlier events might be repeated this winter. This particularly applies to some of the tabloids, to those expecting a severe and snowy winter and some of the less experienced readers on this thread. As we know, the models have been struggling for a while in first agreeing upon another Arctic re-load and a northerly blast, how potent it will be, its longevity and what follows afterwards. There have been some large swings from one run to the next, even just 4 to 5 days out. Although the northerly (of various descriptions) has now been agreed upon, the detail is still up in the air and very little else has been resolved beyond next weekend and I expect there to be further swings in the model output for much of this week. I will not get into the technical side to this and will leave that up to the experts. What we have seen during the last month or so is a number of brief northerly outbreaks, roughly a week apart. These have not produced any really significant cold so far although each one has been slightly colder than the previous one, "partly" due to the natural cooling off as we progress into winter. That pattern of MLB in the Atlantic with periods of amplification into the Arctic has produced short lived meridional patterns. The undulating jet stream has meant that the UK has more or less alternated from being on the warm and then the cold side of the jet. For several weeks now we have seen a fairly static pattern with the blocking HP mostly located in the mid Atlantic and LP extending southwards from the Arctic, through Scandinavia and into northern and now central Europe. Here are some of the charts from the last few weeks. They are all ECM 0z runs using the T+0 output to show the actual "current" pattern for the date selected: 5th November 2017 13th November 2017 24th November 2017 30th November 2017 4th December 2017 - current These all, more or less, show the last four brief northerlies. Now let's look ahead for several charts moving on from the current pattern on last night's ECM 0oz chart (above) and then the rest of the run from T+96 to T+240 and also GFS and GEM for T+240:: ECM: T+96 December 8th T+120 December 9th T+144 December 10th T+168 December 11th T+192 December 12th ECM T+216 December 13th ECM 0z T+240 December 14th GFS 0z T+240 December 14th GFS 6z T+234 December 14th GEM 0z T+240 December 14th The last four charts are for D10, 0100 on December 14th. These all show colder patterns at that time. I fully appreciate that we are moving well into FI and this time period is "after" the likely broader pattern changes expected around T+120 to T+168. The main point here is that whatever route some of the main models take (and some go for a short milder interlude) they generally end up with a colder pattern with renewed amplification into the Arctic. Some runs are cold throughout. Note that UKMO only go up to T+144 and the JMA model only shows yesterday's 12z for this D10 period although it too ends up with another northerly at that time, so these two models are not shown. Several of the recent runs and some of the GEFS and ECM ensembles showing a succession of slider lows running south-east from Greenland or south of Iceland usually via some part of the UK and then phasing with the Scandinavian/European LP block. These are based on the jet stream taking a north-west to south-east route. If there is sufficient cold air maintained in our vicinity and to our east (and north), then there is potential for snowfall as well as quite severe frosts, especially in any slacker period of pressure in between systems. There might be short-lived less cold interludes as the LPs engage with the mild air to the south. Now the interesting and highly speculative bit. I have been racking my brains to think of past winters with similar patterns. Most of our longer lasting cold spells come in from the east such as in December 2010 Sometimes there is an alternation between northerlies and easterlies. At this stage of the winter there are actually very few close analogues. Let's assume that we get lucky and start to see the pattern of successive "sliding" LPs moving across us and with some cold air embedded. At this time of the year, the UK is very capable of building and maintaining its own cold pool, given the right synoptics to initiate it and without the jet stream suddenly switching to a direct west to east or south-west to north-east trajectory and blasting everything away in its path. I have come up with 1962-63!!!! Again, I should remind everyone that it's very dangerous to use analogues as only minor differences can produce very different outcomes. Back in the '60s the Arctic ice sheet frequently engulfed the north Iceland coast and was over 50% more extensive than it is today. I'll let the experts provide comparisons on the state of the ENSO and other teleconnections for that epic winter. The 1962-63 winter produced some highly unusual synoptics. The winter started off with a number of brief northerlies during the second half of November and early December very similar to some of those we have seen so far this winter. Then there was a period with HP right over the UK with some cold and very foggy weather during the first week of December (this seems less likely for this December). After another brief northerly, the HP then built into Greenland just before Christmas and the severe spell commenced. There were a number of Arctic top ups and sometimes a proper cut off Greenland HP and there were also long periods of only MLB with little amplification. There were occasional easterlies with short lived Scandinavian HPs but actually hardly any long fetched easterlies. Much of the severe cold was confined to a deep cold pool which developed and stagnated over central and western Europe, including the UK. In fact much of Asia, Russia as well as North America had a pretty average winter! One of the most frequent and repeated patterns were sliding LPs moving east-south-east from the mid Atlantic. Examples of these occurred throughout the 10 week cold spell from Dec 26th onwards. I remember numerous occasions when the forecast was for a short spell of snow followed by much milder weather with a steady thaw. These never materialised and there were various accounts of that winter which suggested that the tracks of these LPs were "against the whole weight of meteorological probability". There were only very occasional and very short lived less cold interludes (mostly confined to the extreme south-west) and many parts of the UK saw long periods with "ice days". Let's have a look at some of the charts which all come from the excellent NCEP Reanalysis Archives on Meteoceil (link: http://www.meteociel.fr/modeles/archives/archives.php?mode=2&month=12&day=30&year=1962&map=4&type=ncep). You can examine the charts and 850s etc for the whole of that winter and move through the charts on a rolling 15 period. The records go all the way back to 1871: November 15th 1962 December 10th 1962 December 26th 1962 December 30th 1962 January 2nd 1963 January 5th 1963 January 6th 1963 February 6th 1963 February 8th 1963 February 9th 1963 February 15th 1963 February 17th 1963 February 24th 1963 March 5th 1963 - the end! I really do feel that readers should consider all this as a "bit of fun" and that "Bring Back 1962-63" permanently lives on Fantasy Island! There is a more serious side though. Despite anywhere near a repeat of the epic '62/63 winter being extremely unlikely, it does show what can happen when the pattern gets stuck in a rut and just very occasionally that rut is with the UK under the coldest part of it all. I will be looking out for these sliding lows and whether the renewed PNA and mid-Atlantic ridges set up with some further bouts of amplification into the Arctic and the jet stream is sometimes set on a north-west to south-east path to sometimes allow LPs to break through and/or very cold air to stagnate over the UK and north-west Europe. If we get that pattern, then its a question of how long it might last. Now, any advice on how I can "de-ramp" my reputation!
  20. 48 points
    WINTER 2017/18 REPORT No. 3 WITH DECEMBER 3rd INPUT PART 2: As this is a long report I split it into to two parts. Part 1 was posted much earlier today – now buried on page 117! That focussed on a review of the model output over the last few days and looked ahead to the pattern changes expected later this week and beyond with a closer look at the jet stream and the temperature contrasts over North America and the adjacent Atlantic Ocean. I shall now focus on an updated analysis of the Arctic, European and Asian snow, ice and temperature profiles, with some of my regular features. While I was writing part 1, the 12z model runs started to be churned out. In general there has been a real improvement from last night’s 0z runs (from a coldies' perspective) on upgrading the forthcoming northerly as well as the period beyond that. As this thread will probably be knee deep this evening in analysing the latest output (if not the snow next week!), I shall leave this to our regular and occasional posters (for now). Here’s the deal – you concentrate on finding the right synoptics and I’ll search for some deeper cold!!! In my first full report for this winter on November 22nd (see page 192 of the 1.9.17 model thread) I focussed on some of the reasons for the lack of any decent cold uppers. I looked at the current temperature profile of the Arctic. The exceptional relative warmth there is very worrying and making it that much harder for the UK to tap into a deep cold source. I felt that we would need a sustained and direct Arctic flow to enhance our chances. Several of the more recent model runs have indicated that we might see some surprisingly low uppers – possibly -8s generally and perhaps nearer -10s in parts of Scotland. One GFS run yesterday even showed several spots under -12s. This would be quite exceptional for several reasons – so early in the season, on a northerly being heavily modified after crossing well above average sea surface temperatures (SSTs) and from what “was” (see later) a much warmer than average source. There is a study which suggests that even with a warming Arctic and near record low sea ice extent that the amount of modification is actually quite limited – I’m not quite sure that I entirely agree with that. Yesterday I replied to another post enquiring whether -12c 850s (if they verified) would be close to a record for Scotland this early in the winter. I looked at a number of early winter cold spells going back to 1878 and showed the 850 charts for the coldest periods during some of these spells (for those interested, see page 101 of this thread). This demonstrated just how rare -12 uppers are even in some of our severest early winter cold spells. Most of the UK’s lowest 850s come in on Polar Continental air streams with a much shorter sea crossing with the south-east usually (but not always) seeing the lowest values. I do still feel that sub -10s will be very difficult (but not impossible) to achieve from the forthcoming predicted northerlies. I would love to be proven wrong about this but widespread sub -8s will do nicely for now! Arctic Sea Ice News and Analysis: During last July the Arctic sea ice extent briefly hit a new low for that time of the year challenging the record lows seen in 2012. It reached its lowest point in mid-September when it was the fourth lowest on record. There was a limited recovery during October and early November with only 2012 and 2016 lower. The overall ice extent in late November again fell below the 2012 levels. It does appear to be gaining ground again during the last few days (still below 2012 levels) as can be seen in the charts below: Sea Ice extent Dec 2nd Sea Ice Concentration Dec 2nd Ice Extent Dec 2nd and 30 year Means Ice Extent Nov 2nd over Last 6 Winters Note: for some reason the first three charts did not update properly today but you can view them on the link below. These charts shows the current extent of the sea ice as on December 2nd (November 2nd for the last chart) and this is in relation to the 30 year means. I believe that these particular charts will automatically update even after I’ve posted them!). Source: National Snow and Ice Data Center (NSIDC) Here’s the link for the latest monthly report (from November 2nd) and the current charts: http://nsidc.org/arcticseaicenews/ The next monthly update is due out later this week and I shall probably post this separately shortly after it becomes available. Arctic Current Sea Surface Temperatures (SSTs): SSTs December 2nd SST Anomalies December 2nd Source: NOAA Marine Modelling and Analysis Branch The anomaly chart shows that there is a wide area of open water in the Arctic with well above surface temperatures. The SSTs need to be below the -1.5c threshold (the purple colour). Sea water will start to freeze when it is below -2c but that is for normal salinity. There is slightly lower salt content in the Arctic (mainly due to ice melt) and the threshold is nearer to -1.5c. There are some areas with SSTs well above freezing and the current anomalies are widely over 4c above average and up to 7c above in places although they have fallen very slightly in the last couple of weeks. These higher SSTs are a legacy of the 2015-16 winter when the Atlantic jet stream powered well into the Arctic for much of the first half of winter. This shifted much warmer than average currents right up to the edge of the ice sheet. This strong anomaly has persisted for 3 years and is exceptional and comes on top of the already generally warming Arctic. Unless the SSTs reduce substantially, the anomalies might be carried through to next summer and into a fourth winter. There is a small area of the North Atlantic, mostly south-east of Greenland with a negative anomaly. SSTs have fallen in recent days in the open water north of Svalbard – I’ll pick up on this shortly. British Sea Surface Temperatures: December 2nd November 21st I was struck by how fast sea surface temperatures around the UK have fallen in recent days since my first winter report on November 21st. This is partly due to the recent Arctic outbreaks and the lack of strong south-westerlies as well as the normal steady decline from the summer to the winter months. Svalbard 10 Day Maximum Temperature Forecast (December 3rd) : The very good news is that the forecast temperatures for the Svalbard stations that I monitor are mostly forecast to fall somewhat in the next few days. I summaries the D1, D5 and D8 values for each station with the previous values (from the November 25th forecast) immediately below. I also show the website link for each station so that you can view the full details. Central/West Svalbard – Longyearbyen 28 m asl: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/forecast.pdf December 3rd Forecast: Dec 4th -3c; Dec 8th -9c; Dec 12th -9c; November 25th Forecast: Nov 26th -6c; Nov 29th -8c; Dec 3rd -6c. North-West Svalbard – Ny-Alesund: http://www.yr.no/place/Norway/Svalbard/Ny-Ålesund/forecast.pdf December 3rd Forecast: Dec 4th -4c; Dec 8th -14c; Dec 12th -11c; November 25th Forecast: Nov 26th -5c; Nov 29th -12c; Dec 3rd -10c. Central South Svalbard – Sveagruva: http://www.yr.no/place/Norway/Svalbard/Sveagruva/forecast.pdf December 3rd Forecast: Dec 4th -3c; Dec 8th -14c; Dec 12th -15c; November 25th Forecast: Nov 26th -10c; Nov 29th -15c; Dec 3rd -13c. Please note that the links above will update automatically at frequent intervals throughout the day. They are the Norway met office’s predictions. We need to be aware that these are only a forecast that is subject to change and I am told that the Arctic surface temperature forecasts are not completely reliable even at quite short range. The temperatures were above freezing 2 weeks ago but fell below freezing towards the end of November. They are continuing to fall back further and will not be far off their 30 year means for this time of year later this week. They look set to remain at these lower levels for at least the next 10 days. To put the above figures into context, here is a link to the main Longyearbyen site: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/statistics.html Svalbard Airport, Longyearbyen: Temps for last 30 Days Temps for last 13 Months Temperatures, Precipitation and Wind for the last 13 months Tabular view for temperature and precipitation per month Months Temperature Precipitation Wind Average Normal Warmest Coldest Total Normal Highest daily value Average Strongest wind Nov 2017 -3.6°C -10.3°C 2.5°C Nov 15 -13.4°C Nov 29 1.9 mm 15.0 mm 0.6 mm Nov 28 6.7 m/s 17.7 m/s Nov 11 Oct 2017 0.5°C -5.5°C 7.7°C Oct 23 -5.8°C Oct 25 27.4 mm 14.0 mm 18.9 mm Oct 24 5.1 m/s 13.2 m/s Oct 23 Sep 2017 4.9°C 0.3°C 13.3°C Sep 26 -0.7°C Sep 1 20.8 mm 20.0 mm 5.3 mm Sep 19 4.9 m/s 16.3 m/s Sep 23 Aug 2017 6.1°C 4.7°C 11.6°C Aug 2 0.2°C Aug 27 16.2 mm 23.0 mm 7.4 mm Aug 29 4.7 m/s 14.6 m/s Aug 16 Jul 2017 6.9°C 5.9°C 13.1°C Jul 18 2.7°C Jul 4 20.4 mm 18.0 mm 6.5 mm Jul 14 5.5 m/s 13.6 m/s Jul 14 Jun 2017 4.6°C 2.0°C 9.0°C Jun 11 -0.2°C Jun 5 5.6 mm 10.0 mm 1.9 mm Jun 17 4.3 m/s 11.6 m/s Jun 29 May 2017 -3.9°C -4.1°C 7.3°C May 31 -11.5°C May 9 5.3 mm 6.0 mm 1.7 mm May 15 4.1 m/s 13.9 m/s May 15 Apr 2017 -8.3°C -12.2°C 2.9°C Apr 29 -21.3°C Apr 1 6.2 mm 11.0 mm 2.5 mm Apr 28 5.5 m/s 15.0 m/s Apr 5 Mar 2017 -11.8°C -15.7°C 2.5°C Mar 14 -23.5°C Mar 18 15.8 mm 23.0 mm 2.8 mm Mar 7 5.6 m/s 15.6 m/s Mar 26 Feb 2017 -6.6°C -16.2°C 5.9°C Feb 6 -21.3°C Feb 18 45.4 mm 19.0 mm 10.6 mm Feb 8 6.5 m/s 21.0 m/s Feb 21 Jan 2017 -10.3°C -15.3°C 2.2°C Jan 16 -21.1°C Jan 31 24.6 mm 15.0 mm 8.7 mm Jan 19 6.3 m/s 17.9 m/s Jan 17 Dec 2016 -6.0°C -13.4°C 4.8°C Dec 21 -18.5°C Dec 8 22.7 mm 16.0 mm 3.4 mm Dec 20 5.9 m/s 24.8 m/s Dec 29 Nov 2016 -0.7°C -10.3°C 6.4°C Nov 8 -11.1°C Nov 27 58.0 mm 15.0 mm 41.7 mm Nov 8 5.7 m/s 16.5 m/s Nov 8 The second chart and the table show monthly means and actual highest/lowest temperatures recorded during the last 13 months. The chart has just been updated with the November 2017 figures when the monthly average temperatures were 6.7c above the 30 year mean. Svalbard has been seeing “maximum” temperatures often running at 5c to 10c above their long term average throughout most of the last 4 years. This is reflective of the warming Arctic and the near record low sea ice cover. European 2m Surface Temperatures: Current "live" Dec 3rd 1450 Dec 3rd 0650 Dec 2nd 1450 Dec 2nd 0650 Note that it is important to allow for min/max temps when comparing the charts. The 0650s are usually close to the minimums and the 1250s are usually close to maximums. Northern Hemisphere Surface Temperature Charts: These were shown in part 1 of this report on page 117 of this thread. Northern Hemisphere 850 Temperatures: These were shown in part 1 of this report on page 117 of this thread. Northern Hemisphere, Asian and European Snow Cover: I show animations for snow cover and sea ice changes. These are produced by the National Ocean and Atmospheric Administration (NOAA). When you go to their site you can change the date range and go back over 10 years. You can change the speed and pause on any particular day. These are brilliant, very informative charts and great to play around with. I’ve re-set the links below to show the last 2 weeks from November 18th to December 2nd but you can change the dates on the site and choose your own options. I also show the first and last charts below for this same date range. a) Animated Northern Hemisphere Snow Cover Changes (updated by NOAA on December 2nd): https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/nh/20171118-20171202 December 2nd chart November 18th chart b) Animated Europe and Asia Day Snow Cover (updated by NOAA on December 2nd): https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/ea/20171118-20171202 December 2nd chart November 18th chart North Asian snow cover has been well above average since mid-October. During the last 2 weeks it has grown steadily and expanded southwards and westwards into Eastern Europe and small parts of central and western Europe (not just the mountainous regions) as well as to parts of the Middle East. Europe had been almost snow free. The snow cover over northern and central Scandinavia has now spread to much of the south too in recent days (note that the high central plateaus usually have pretty complete snow cover for most of an average winter). Meanwhile, the extensive snow cover over the northern USA has receded and is mostly confined to northern and central Canada due to the mostly milder conditions there until recently. Overall, the Arctic indicators show that there has been quite a cooling trend during the last few days. SSTs are very slightly lower, sea ice on our side of the Arctic has expanded (best viewed on the snow cover animated maps from the link above). Svalbard, north Asian as well as central and western European temperatures are falling. In fact a colder pool is starting to develop over western Europe. Asia, European and Scandinavian snow cover has expanded. So, in the simplest terms, there are some better signs that air streams sourced from or travelling over the Arctic, Scandinavia and Europe are becoming better suited to delivering rather deeper cold. Much will depend on the ongoing synoptics and the broader patterns. Finally, this is an exciting time with great potential for coldies with some fascinating model viewing continuing as we move further into winter. Next report (no. 4) probably next weekend if I have time.
  21. 48 points
    In case people are wondering about this warning system! Lol it did appear a few years back but I shelved it because so few decent cold synoptics ever appeared in recent years there was nothing to warn about ! Red - low margin for error , liable to implode at any moment ! Amber- medium margin. Green- prepare to dust off the ear muffs, scarves and ice scraper. Green Plus- as above but include the sledge !
  22. 47 points
    Re: days 11-15 and uptick in 850 values GEFS days 11-15 longwave pattern an excellent representation of the expected GWO phase 8 signal Note the position of the polar vortex centred Canadian Maritimes. Cue 'winters over' calls. However, we will be entering a transitional period when the behaviour of the North Pacific ridge will be dynamic and repositioning itself. If we stay exactly where we are, January GWO phase 8 and look what happens to the positioning of the North Pacific Ridge and the polar vortex. The North Pacific ridge becomes less pronounced and part merges with the Arctic ridge. The polar vortex over Canada is shifted westwards. With the next convective tropical wave signal likely to send angular momentum upwards in second week of January, phase 4 of the GWO the next broad scale evolution. Again, where's the polar vortex ? Merging those two phases continues to suggest the blocking to our north and north-east will be a persistent feature. The uptick in 850s being indicated on ensemble means is reasonable, but suggestion being that focus for colder air will becoming more from NE and E vectors in January, possibly sooner. I would be focused on a week of milder values and the trend downwards in ensemble members.
  23. 47 points
    We have an arctic rabbit on the gem
  24. 47 points
    Hi everyone, I do not normally allow myself to get too involved in the run by run analysis, especially whilst they're being churned out - I leave that to the regulars for their comments, which are sometimes as variable as the model output or even more so! This is in no way a criticism and I enjoy reading many of the posts. I normally prefer my more balanced and thorough analysis. I must say, however, that today's 12z ECM is consistently much better than some have suggested. In general, most of our longer cold spells have brief milder or less cold blips. The November/December 2010 spell was split into two severe spells and a milder chunk in between. What I am seeing in today's runs is an adjustment from the Arctic northerly to a quite probable easterly into week 2. The initial indications start at around T+168 to T+192. Obviously we cannot be sure that this will be the eventual evolution but there are various encouraging signals.This is what I have been looking (and hoping) for as I said in my long report this afternoon (on page 222). I'll explain what I'm on about with some of the charts: ECM 12z charts: T+168 T+192 T+216 T+240 As the likes of @stevemurr and @nicksussex and several other regular posters keep telling us, it's a good idea to look upstream and not just in the immediate vicinity. At 168 we see the Atlantic heights sinking somewhat and heights also starting to fall over Greenland. This is more than compensated for with a strong build of heights over central Russia and into the Arctic.By 192 heights are building from Russian into Scandinavia. There are also signs of renewed heights building up into western Greenland - I do not believe that this is the dreaded west based -NAO setting up residence but just a part of the overall evolution. Shallow low heights are spreading south and west over Europe. The lower heights over eastern Greenland are beginning to shear off. By 216 this evolution continues with heights rising over most of Greenland. The Russian high continues to build strongly into Scandinavia. The lower heights which were over Greenland have been forced south-east over Iceland.This process continues nicely into 240. The low heights over Iceland are steadily sinking south-east into Europe with strong heights building to the east, the north-east, the north and the north-west from Russia into the Arctic, across Scandinavia and also in Greenland. This is an entirely possible (perhaps even probable) evolution and how many a decent cold spell has developed in the past. I hate to ramp this too much but it is not dissimilar to December 1962, December 1984, January 2009 and December 2010. Yes, we'll have to see on the next run if this trend continues. I feel that if there was a T+264 ECM chart it would show the low pressure completing its journey into central Europe and a strong Scandi high building behind with a long fetch easterly starting to assert itself and much colder air being dragged down into north-west Europe and the UK. Just briefly, a look at a couple of the ECM 12z 850 charts: T+168 T+240 Some -8s starting to show up, with an area of -12s over Scandinavia and that wedge of milder air to our west is being steadily squeezed out. By 240 there is a decent pool of -8s and a lobe from Siberia is moving steadily south-west through north-west Russia heading towards Scandinavia and northern Europe with some -12s, -16s and even -20s upstream. Now I and the ECM may be wrong but this is my take on it right now. Fingers crossed that we see an evolution along these lines. I'll be interested to hear others comments on this and I'll be happy to exchange PMs so that we do not clogg up this thread too much. That's about the most bullish I've been for many years!
  25. 46 points
    for future reference, when referring to a situation where a potentially exciting scenario turns into disappointment, the term "damp SQUIB" is used. a squib being a type of firework. you can see how a wet firework could lead to disappointment. instead of "oooh!" and "aaahhh!", "meh" or "pffft" would be a more likely utterance from the casual observer. this is a damp squid- i have yet to find a situation where a wet cephalopod would be a good analogy but if i do, i will get back to you. thanks
  26. 45 points
    Huge number of people reading this evening *waves* hello hello! Welcome. If you’re new here (or have been here a while) just a general reminder that questions like ‘will it snow in my garden?’ Are best answered in the regional threads which are full of local weather experts and enthusiasts. There’s some really knowledgable posters in them that will help you with your detailed location specific questions. If you have a ‘feeling’ or are just unhappy with the output your post will be most welcome in the Moans Ramps and Banter thread. Ditto animated gifs of dying snowmen, game of thrones etc etc. The thread is moving really fast again tonight and I imagine it will continue until the pub run so rather than having delete and hide five million posts and upset a load of people please consider the best destination for your posts. please remember we aren’t trying to censor or limit the conversation. There’s only a handful of us to try and keep things ticking over and when 300 people all want snow answers on one thread which is for technical discussion, the technical discussion gets a bit diluted which makes people who have spent time giving analysis a bit peeved when their carefully constructed post is buried in other stuff. aaaaaand GO! 😘
  27. 44 points
    Furthermore to this it may just as well help by backing this up with some facts. So to recap where we are this winter: We have a descending solar cycle aligned with an descending eQBO - historically most NH blocking episodes and -NAO have been seen during this time - we have previously shown the papers that suggest this. EDIT I have got this bit wrong - so apologies for misleading - for a descending solar cycle the NAO is mostly positive - but this data was taken with far higher solar max values rather than the subdued cycle max we have just seen - so at the end of the descent the results may be more closely aligned to the minimum rather than the descending phase. Paper is here http://onlinelibrary.wiley.com/doi/10.1002/2013JD021343/full We have a disrupted trop polar vortex that has been ruling the roost over the lower strat vortex - hence the mean zonal mean winds (u winds) at 30 and 10 hPa are significantly lower than we are used to with no signs that any upper vortex intensification (VI) is likely to occur and filter down anytime soon. The MJO forecasts in a Nina'ish year are surprisingly good http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml and I am sure that @Glacier Point and @Tamara can come and confirm how this affects the GWO. But if we look at the composites for December for this type of set up then we see this Without the Nina then these height anomalies are stronger over Greenland. The trend is definitely for a southerly tracked jet in a NW to SE axis exactly as we are seeing currently and I don't see anything that will change that in the short term to the usual SW to NE axis. That does leave the door open for Scandi height rises so well done to GP and Tamara for suggesting this. But overall the pattern forecast by the models looks 'right' and I would be highly dubious of any that suggest a return to mild zonality for a while. Now all we need (on a personal note) is for the snow charts for this weekend into next week to include Sussex!
  28. 44 points
    Fantastic news!! the local council have just replaced the light bulb for the lamp-post outside my house!
  29. 44 points
    Please can I urge anyone tempted to go buy a sledge, tell friends or relatives, or post about the models runs elsewhere on social media NOT TO You wiil only jinx it Thanks
  30. 44 points
    Someone called 'Sizzling Heat' says he, or she, sees the GFS 12z giving 'a mild week' with 'not much cold showing up now anymore.' Hmmm. There's always this sort of trolling and you may well prove right. Statistically and historically you probably will be. But, for the avoidance of doubt, that 12z GFS is not a 'mild' run. In fact, synoptically it's a storming run bringing biting north-west through north-easterly winds which would feel bitterly cold: the wind chill off that would be off the scale. I mean, seriously, you are having a laugh ... right? Look. No, truly, look: I love the synoptics of this. And I'll take a fired jet if it shifts things too. 90% Sizzler will be right that the reload will go mild. But I'll take these odds because one day, boy, are you mild-spectacled folk going to be in for a rude shock. The 10% roll will happen.
  31. 44 points
    the ECM looks distinctly nippy in the short to mid term time frames.................Our roving reporter asked renowned NetWeather mascot Sidney Squirrel for his snapshot of the upcoming weekend
  32. 44 points
    I suspect some are missing the significance of the deeply neg AO upcoming the amplification introduced into the NH pattern and subsequent vortex disruption provides for further opportunities to bleed cold into the mid latitudes thereafter. Whilst this particular negative phase may not bring any snowy wintry conditions to nw Europe, it could well leave us with a mid lat high which could lead to a greeny or Scandi ridge a week or two down the line. there is currently no sign of the vortex returning to Greenland on the extended two week ens suites. N American upper temp profile is not predicted to be cold which would fire up the jet. Upper strat zonal flow whilst on the strong side is not descending. there is nothing to be downbeat about as we approach winter proper.
  33. 43 points
    Thanks Broadmayne Blizzard This isn't, or shouldn't be an ego platform, and I think its a good idea myself to appreciate the good thoughts and contributions of a very wide breadth of posters on this forum, and not focus on select contributors. Much as BB62/63 outlined so well yesterday evening Furthermore, as keeps being repeated but equally keeps getting ignored by a few members, its a good idea to represent correctly what posters say, in the correct perspective and context and not put a misleading slant on them, however un-intentional, in most cases at least, that may be. It takes enough time to put posts together, let alone having to keep re-correct words that often get put in the mouth Last week, advice was given not to get too sucked into ups and downs of intra day and ensemble suites and take them at face value. The summaries of bluearmy and MWB read between the lines very well and seem quite appropriate to range of possibilities over the medium terms. But, at present, from evidence that is available and up to date, the Global Wind Oscillation is heading to Phase 8 and the December composite is reflected pretty well in the upcoming weeks synoptics, and within a reliable time period I think beyond this time, is where extra care is particularly required in terms of NWP suggested output. Models are going to be very sensitive to the natural ebb in the tropical cycle and climatology will play a part in bias to a longer sustaining westerly pattern in these circumstances - especially set against a highly disorganised stratospheric profile But there has continued to show a willingness for tropical convection patterns to mirror the definitively east based nature of this La Nina - and hence display synoptic traits that are quite different to the predictable increased vortex intensification and flatter pattern that I happily admit I approached this season with a plenty of caution The evolution back to Phase GWO 4 (where we have just been), crucially assisted by seasonal wavelength cycle changes the pattern heading towards and especially into January. Nothing is ever guaranteed and no-one can be wholly psychic with the complexities of weather science. But that composite isn't too different to the anomaly chart that is still clearly in NWP running in ba's post this morning. Best not get hung up on translating that to a precise surface pattern or take the timing too literally, (though Christmas would be nice obviously in an ideal world). The downside pattern in terms of Indian Ocean tropical convection patterns taking over is the flatter pattern risk, emphasised in each and every post. But on the basis of the above analysis, the point to continue to labour is not to get pushed and pulled reactively by each and every model output suite I'm very much anticipating some atmospheric and angular momentum budget updates which will give some further important clues as to the extended Pacific and Atlantic patterns, and also developments beyond that in terms of looking NE. I'm sure others are very much doing the same By the way, its snowed in the last couple of days around the UK, away from the far south, and is snowing as I type outside folks windows at the moment and so please get out in it, take lots of pics and enjoy it whilst it lasts! Today illustrates what a microcosm one region of the country can be, let alone differences across the country commonly seen themselves. I'll trade the very underwhelming autumnal charade being played out here at the moment for putting some faith in a change of angle of approach and hopefully improve my own fortunes in joining in with some fun before too much more time has passed
  34. 43 points
    Surface temps 2c below, often 4c below average as a mean, right out to T360. That's a mean of 50 members, and widely across Western Europe within the trough
  35. 43 points
    The 18z GFS is overdue one of it's reverse zonality specials, if it takes the idea of the 12z GFS and goes to the nth degree who knows. We have - Atmosphere wanting to deliver huge negative AO -NAO in the area where it has not been the default for a few yrs A Solid eQBO following the blip in the QBO metronome A Pacific not ruling the pattern one way or next A three wave assault on a disconnected vortex and the best projections for Aleutian, Greenland waves for years. The pacific conduit for wave driving seemingly on an endless wave train for wave driving into the strat. Global AAM positioned to launch an EAMT. Solar heading into the circle of death vs Classic Vortex Intensification Period, Nina front loaded winter and poor strat analogs for displacement events of this nature. All in - tremendous model viewing, and something we have not had to enjoy for a few years. Lets make the commentary on said viewing as cool as it can be..
  36. 43 points
    Can I just pop in and say that we had very similar ‘winter’s over’ commentary not two days ago, then a staggering pub run with everyone on the cusp of bulk buying salt and now we are back to despair, all in the space of 48 hours. As tempting as it is to get emotionally invested into these outputs, given next week is still all rather interchangeable depending on the model, I’d suggest not hanging on every frame of every run.... as the wise have probably said, the models don’t set the weather. The weather (and some mind boggling statistical data) sets the models. It’s going to be a very very long and frustrating winter otherwise! Of course if you need to vent your frustrations there is the Moans and Ramps thread just a couple of clicks away...
  37. 42 points
    Ecm must be male as it always overstates the number of inches that you'll actually see ....................
  38. 42 points
    Thats the kind of comment I expected from you, no respect for other posters who contribute a lot to this thread, even in summer when it's so quiet. As I do.
  39. 42 points
    I know the drama in here is part of it, but those jumping about like cats on hot tin roofs based on every run, probably need to calm down a tad. Especially since it's not even mid-November yet. All this talk about the cold being gone, winter being over, or the next 1947 being on the doorstep blah blah blah, based on single runs, is going to get tiring very quickly - especially in this thread. (Hint: head to the model banter thread to ramp/moan). Taking today's 00z as an example. Here are the ensemble means vs climatic averages - hardly mild, and a negative NAO. That's not to say it's exactly how it'll play out, but we're looking at forecasting models at 7 days plus here - you're not going to get exact or consistent answers from it. Best to step back a tad, and look at trends, and the wider picture.
  40. 41 points
    Well I can confirm you are in the correct thread
  41. 41 points
    Model watching is all about looking for trends, and having looked really closely at the text and charts posted the past few days, I've noticed a trend that is really starting to stand out ...... That Steve Murr desperately needs one of these, can we organise a whip around or nice letter to Father Christmas? I'll fetch me coat.... banter aside, some very good charts if one is of a cold persuasion, but as always are subject to change......and just goes to show how things can change model wise in 24 hours......can't wait for the 18z and overnight runs in the ongoing saga of 'Shortwave Wars - The Phantom Menace'
  42. 41 points
    The updated NOAA monthly forecast has just been issued. http://www.cpc.ncep.noaa.gov/products/predictions/long_range/fxus07.html If the UK can't get some snow and cold from what I've read then theres a curse! It might be wintry in the east USA with energy firing east into the Atlantic but with a negative AO and the MJO on the move towards the west Pacific low track into the UK should be forced further south. So to be frank it would be tragic beyond belief if coldies here don't get something to enjoy during December.
  43. 41 points
    So, another long one (I'm afraid) of intending to manage expectations before returning back to the rollercoaster sidelines My own perception of the start to winter. (like any other season in terms of weather preference), largely differs from most because I am far more interested and curious how the signals play out (either way) and not how cold and snowy it might get. So I will have to be forgiven for a different tone that frankly intends to neither optimistic or pessimistic, but simply hopeful objective how I see it. There is neither the time or inclination to get absorbed in the daily swathes of NWP operational and ensemble suites - but instead the usual non NWP approach is most helpful to me. In the final analysis anyway, the signals dictate the models, not the other way around. Apparently consensual ensemble suites gauge assessment based on a moment in time captured, but they are prone to switch direction like shoals of fish when they realise something different may be going on... So, for what it may be worth: Sorry no time for links. Atmospheric angular momentum tendency (essentially in context referring to the turning force of the jet stream) has tumbled back with lack of tropical convection (MJO) focus allowing easterly wind inertia to return to control the atmospheric circulation in line with La Nina consolidating at all levels in the Pacific. The SOI is consistently +ve and there are colder waters to upwell and strengthen La Nina into the close of the year The Global Wind Oscillation (which represents a plot representation of global wind flows as referred to above) in reflection of all this, has progressed from quite an amplitude Phase 8 and is set to hover around Phase 2 for a while. This slow/stationary orbit underpins the modelling over the coming days in terms of the very big signal for a very amplified holding Atlantic ridge - and certainly favouring a cold pattern sustaining into the medium term as the vacuum occurring upstream slams on the brakes with jet flow rapidly decelerating In terms of the stratospheric feedbacks though, the question mark in my mind is the extended hints of the Pacific pattern starting to show the first signs that La Nina is going to tighten its control from upstream with the building of the Alaskan ridge. On that basis a highly anticipated two week stratospheric forecast is just that, and on the basis of potential upstream changes that ultimately spell return of the jet, it cannot be wholly assumed it will automatically favour this side of the pole as the Pacific pattern starts to take control. So I don't personally agree with some of the views being expressed that this is a "good thing" for downstream prospects in terms of sustaining a cold weather pattern beyond the early to (possibly?) mid December period. Its a typical La Nina development that often happens as wavelength cycles occur with the change of month and season and has the effect of increasing Canadian cold and re-booting the energy into the downstream polar jet. Such inications are minority model solutions at the moment that show increased upstream flow in FI, but I think its not a case that they are automatically wrong, simply maybe on the progressive side. And I would be highly cautious of 100% confident assumptions then return energy will automatically split and encourage trough disruption under the Atlantic ridge On that basis I'm not sure that any equal assumption (however valid) can be made that the present amplified pattern has a sustainable feedback. Or at least not sustainable without a further eastwards moving MJO catalyst, to engineer further tropics>extra tropical rossby wave train and set up further downstream amplification via +ve MT and then, just as importantly in turn externally pressurise the polar stratosphere. Even the freeze of 2010 ended on the basis that no follow up occurred to the high amplitude MJO event of October and that led to the rapid taking of control of the default La Nina Pacific ridge and return of polar jet flow after Christmas So the La Nina default will not favour any undercut of -NAO automatically. The upcoming pattern is a traditional (extra amplified) mid latitude ridge pattern. The irony is that the higher AAM pattern we have been seeing of late has actually featured something of a Greenland High and an attempted -NAO (albeit west based). Its no coincidence that falling AAM redistributes the blocking pattern into the Atlantic. I think this has already been forgotten by quite a few because of the pretty charts at the moment However much the warm air advection from this ridging may perturb the troposphere/boundary and help prop up the poleward nature of the ridge in the short and medium term, the increasing upstream amplification in the Pacific that will carve out the default La Nina ridge will, eventually, increase cold air advection upstream and focus jet energy into the polar branch. That is not going to assist cold air advection downstream and both negate stratospheric destabilisation this side of the pole, and transfer the weakness to the Pacific side. This is an old and familiar story, and though we are certainly in a different place to last winters weak La Nina, the possibilities remain the same with the arctic in such an alarmingly fragile state. Its getting increasingly hard for the whole hemisphere to be cold - there is simply not enough cold air to go around. Something, and somewhere, has to give The importance of the Aleutian Low and Siberian High moving forward in terms of cold air feedbacks have been identified a few times on here as a means to sustain a cold pattern into winter proper. Any Pacific heights, as a key part of an arrangement of circumglobal La Nina mid latitude ridges and polar jet flow, are counter intuitive to this. The stratospheric pathway can certainly override the tropospheric winter La Nina effects, but its going to require tropical forcing to play ball and come into play just at a time when the upstream pattern shows signs of coming back to life once more. Strengthening La Nina and changing seasonal wave length changes are going to become increasingly resistant to this the further we head towards January and especially beyond. There is no certainty either way, and whilst the pattern could sustain in a few ways yet - the "quick fix" I spoke of in the MOD a couple of weeks could easily still be just that. At the moment I see things much as I would at the end of a warm La Nina Spring, that so often does not transfer to a warm La Nina summer. That said, there is more to encourage a cold pattern, certainly to start, beyond what the weak La Nina went on to deliver last year - but I don't see the straightforward path to sustained cold nirvana many others see. Ciao
  44. 40 points
    If the gfs 18z shows snow to the south can we southerners please all bang on about it for hours on end. Thanks in advance Not that I’m bitter or anything
  45. 40 points
    well... is the GFS showing us the light at the end of the tunnel? or a mirage in the desert? i can only see the ECM going in one direction from this chart- and if it does, netweather members will be fainting like teenage girls at a One Direction gig. (or the Beatles for knocker )
  46. 38 points
    300 people online don’t come here to read mudslinging. If you take issue with a post then report it. Or Pm the member involved. This isn’t the place for ego wars.
  47. 38 points
    The text to your mrs has somehow been posted on here
  48. 37 points
    Hi Several posts since early-mid November have anticipated possible developments and detailed thoroughly in each post both the upside and the downside of the way ahead. My own initial doubts are well documented that weighted a milder trend, but increasingly plenty of evidence posted to show why "usual service" this season may not be so straightforward Also just yesterday I suggested that too much face value paid to intra day operational and ensemble suites could lead to quick and not necessarily correct reaction in terms of the implications of any milder phase mid month. It might be worth reading yesterdays post carefully Its clear, I believe, from there where the boundaries lie, and why there is reason to believe that any milder phase could be a bridge towards a pattern that changes emphasis towards looking across the North Sea Finally, as stressed fairly recently, my interest is very much driven by enthusiasm and curiosity of how patterns might pan out, not just based on weather preference and ideals. On that basis, creating a skewed basis for fitting evidence around either a cold or mild outcome would be futile, self defeating and a waste of my own spare time putting together some thoughts purely intended to help discussion on the thread
  49. 37 points
    Look at the energy west of the high pressure it’s split going North East & south / south west- minimal eastward component ... people posting that it’s a ‘toppler’ are the usual crew that want it to happen anyway.
  50. 37 points
    What do you mean sane I thought we’d all passed the point of no return ! Spending hours observing model outputs and obsessing over the direction of a shortwave could be seen by others as a bit strange ! My friends who know all about my obsession call us the snow people! But I don’t care, I find people strange if they don’t like snow ! I cant get my head around that, who couldn’t love snow . I’m just as excited now to see snow falling as I was when I was a kid. Anyway in a desperate attempt to move back on topic, the minutes seem to be taking ages to count down to the ECM run!