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Showing content with the highest reputation on 23/10/16 in all areas

  1. The daily updating SOI index has fallen into -ve territory for the first time since the end of Spring. As of today, being below the +7 to -7 ENSO neutral band, it "technically" suggests a Nino forcing reading across the Pacific. https://www.longpaddock.qld.gov.au/seasonalclimateoutlook/southernoscillationindex/ Of course the index fluctuates daily, and much more can be read into the rolling monthly figures - but nevertheless this further underpins the point I made the other day that weak Nina status is not a given at all for the remainder of 2016 Which neatly leads me on to ask why is there an Aleutian Low currently being modelled? Well, +ve torque tendency in the extra tropics triggers a rise in angular momentum tendency that causes an enhancement of the East Asian jet and this teleconnects to a fall of pressure the other side of the Himalayas across the North Pacific which in turn gives rise to a Wave 1 poleward eddy to further perturb the early season polar vortex. But an Aleutian Low/+PNA pattern is commonly typical of an El Nino signature in the Pacific - not one of the attempted La Nina base state advertised through the summer into autumn. The weakly +ve trend of the index has prevailed through October in conjunction with the significant -AO and looks set to remain into November I'm thinking that with the vortex so weak, further weakness programmed, and with the Atlantic and Pacific effectively de-coupled in terms of pattern, we might get the best of both worlds heading into winter. What do I mean by the two ocean patterns being de-coupled and the best of both worlds ? First of all the ENSO signal is weak and (in deliberately over simplistic terms) that helps the ocean and atmosphere "do their own thing". While there is, at least at present, an El Nino signal in the Pacific pattern, on the other hand the advertised amplified Atlantic Ridge in the modelling to quite conceivably bring the first early season cold, is a commonly seen aspect of a downstream La Nina pattern in the autumn. La Nina in the Pacific causes a retraction of the East Asian jet under falling torques - and this is manifested as a defined split flow in the central Pacific and a high pressure anomaly across the North Pacific. If La Nina conditions establish properly under definitively sustained low angular momentum conditions (that create the retrogressed Pacific pattern) the downstream effect is to, ultimately, pull the Azores ridge westwards in the Atlantic. The fact that, at this time, the Pacific is showing an opposite pattern upstream to the characteristic pattern has increasing ramifications ahead into winter IF it is recyclable, and/or is a signal of an adjustment of regime away from overall Nina forcing. The post the other day discussed those potential prospects Ultimately, the changes in seasonal wavelengths from autumn into winter proper mean that the upstream Pacific pattern will force itself more and more downstream - and happening at the same time as the annular mode becomes more and more coupled.. The latter I mentioned the other day. That is why I see importance that we continue to see low pressure across the Pacific to maintain a favourable teleconnectic profile to the stratosphere in terms of trop> strat disturbances. Also with an associated relatively higher angular momentum state, there is chance of seeing sufficient westerly wind momentum across the Pacific to enable favourable tropical convection (Phases 7/8) to force a -NAO in tandem with weakness and instability across the stratospheric polar field. The other long term benefactor of course under this regime ( if it is sustained) is the enablement of a strong Siberian High to take advantage of good snow cover in a way that last winters far too strong ENSO and QBO conditions were (famously) not able to. That is why indicators such as the SOI (in conjunction with monitoring angular momentum, torque and GWO orbit progressions) are obvious key indicators to monitor carefully for trends heading forward. Its why I keep posting on this particular topic. Its not to be exclusive of the overall picture at all, I just think that taking into account all the background factors this year, any bias that the atmosphere shows within a neutral ENSO regime could prove (one) crucial factor m moving forward "If "La Nina forcing resists the current "destructive" phase, angular momentum falls back and the pattern upstream reverts to Pacific anticyclones (and a SE US ridge) it would be the case that a favourable unstable stratospheric profile that might help a decent end to autumn or even start to winter ultimately leads to the amplified Atlantic ridging flattering to deceive. Seasonal wave lengths, especially in the event of any vortex intensification that may occur later, ultimately indicate increasing energy being sent into the northern branch of the jet from across the US and cold air advection sent eastwards into Europe as milder air flows across the top of the high. In that sense, if the early season stratospheric weakness is to pay dividends, then it will require a teleconnectic pattern framework ideal to perpetuate vortex perturbment our side of the NH - and not once again across the Pacific side... After a promising start. Maybe September (monthly SOI average of +13) could be the base Nina "low point" perhaps to watch with the ENSO tide. Inevitably in all ENSO cycles, weak or strong, the momentum ebbs and flows according to significant recurrent intra seasonal phenomena like MJO tropical convection activity. But should this be the case, then there is reasonable cause to start thinking that the early season feedbacks across Eurasia with snow cover in tandem with a persistence of the Aleutian Low will start to have positive effects in terms of wave activity that in tandem with increased westerly momentum across the Pacific increasing the chances of tropical forcing an a flip in the NAO substantively in conjunction with stratospheric weakness. But here she is getting ahead of herself...time to do some baking and housework
    38 points
  2. After annoying everyone for the last few months over in the politics thread I've decided to move back to less annoying territory in the model discussion. I've come out of my hibernation a bit early this year due to the shocking appearance of a possible Greenland high. This rare sight is the Olympic Gold Medal of synoptics for coldies, we're a bit early in the season to expect too much from this but its more the difference with the NH pattern compared to last winter which is good to see. I wouldn't raise expectations for anything too wintry if the GH does verify but some frostier conditions look likely. Of more interest is how long this northern blocking can last for because if it can hold then as we get into November things could get more interesting.
    27 points
  3. ....and some very interesting ongoing signals for rest of Nov and 1st half of winter. Rest assured we have some very interesting model-watching coming our way :-) Enjoy.
    26 points
  4. GFS loves Halloween then... eyes to Greenland. Been a few years since we have seen even a hint of this type of chart, let alone in the NH anoms overall. Strat impacts are marked ( given unzipped/splits) modelled across nearly all layers... that Aleutian Low is the story of the run. Think of Butler precursor region for assault on the vortex. Critically different and triggering so many questions for evolution into winter, the propensity for the atmosphere to either 'lock' or 'repeat' with respect to blocking regimes is a point of interest, has the long lasting Scandi High imprint given way to something toward Greenland. Are we seeing a temporary phase shift in the base regime of the NAO.. Brilliant 4 days ahead as the diluted vortex profile decides on it's route to recovery...
    21 points
  5. TBH Karl, whether we actually get a cold spell early November doesn't rock my boat. It's all about seeing what is feasible in the modelling for the time of year and what then verifies. The hemispheric pattern is what counts plus activity in the strat. Extended eps broadly in line with the gefs notable observations for the back end of week 2: atlantic jet weak and way south of where we would expect it to be oct into Nov canadian arctic extremely warm (inc n Greenland) scandi anomalously cold heights in the majority of the arctic much above where they should be all the low heights aleutians and n e Siberia main feature in the NH remains the aleutian low And just for Steve, AO's on the ens are all solidly below through week 2. Eps and gefs sub -2 whilst geps not so enthused although even they have dropped to now be negative neutral rather than undecided neutral.
    18 points
  6. Spread even less with todays update and much more tightly packed... plus dropping to -4 values too .. Mr Vortex taking it on the chin for been a bad boy last winter
    17 points
  7. Scandi / Taymyr/ Archangel ridges for the win. unzipped across many layers - trop led carnage - what a wave break this is... Heat Flux across the polar cohort is brilliant - total perturbation, couple of early 80s CW profiles at U wind level to whet the appetite. And u wind stuff It is running severely shallow - initial thoughts are that Nino is additive on Sea Ice vs the other analogs that do not compound, first season then second season lag effect in strat - next winter if so is looking outrageous given solar profile. The hear and now sees this amazing Scandi ridge as the entree into winter patterns and what an entree, as things move with strat support to greenland and higher arctic one wonders are we in a new regime, literally a new regime given previous CW era related to a different Sea Ice background. The QBO canary in the coal mine analogy may be gathering further clues.... ESRL projection for CW Nov U wind difference from present, very interesting given tilt to intensification..
    16 points
  8. For the start of November - just wow! Look at the mid Atlantic ridge into Greenland and mean SLP pattern. let's hope we're in for a season of repeating patterns.
    16 points
  9. The GEFS 00z mean is very bullish about retrogression and the scandi trough eventually becoming the main player..so I think we have taken a big step towards our first of hopefully many cold snaps / spells during the next 5 months with height rises to the NW and lowering heights to the NE...please make it so..i mean snow!
    16 points
  10. Just for posterity - let's be clear this is the ECM at 192.. Aleutian low is outrageous the next days modelling will possibly map winter 16-17 - superb time to be dialled in..
    15 points
  11. Either way, I would call this next week high-end modelling debate - given it's timing early in the season - so good to have discussion here and now. Previous incarnations of atmospheric dynamics have heralded much success here SAI / OPI correlation - we are in geomag declining phase, cloud 10 cleverly pointed out this analog may come back on line this year, truth is it is still geomag related to SSTs / Sea Ice... coincidental r when not SMax or S Min. So where are we on geomag... Declining phase - atmosphere written for a weakly prevalent positive NAO over DJF - yet canonical predictions, analogs all point elsewhere - that is why this early initial slow down at 60N is pivotal.. This as I said could be the most fascinating period of modelling ahead this winter a) for up close and northerly and b) for heralded impacts down the line... make no mistake those over the last 36 months who have viewed this thread, this pattern is elusive to us old timers too...
    14 points
  12. Well good agreement between the ECM and the GFS for a retrograde of the pattern sufficiently west to deliver a plunge of colder air into the UK. The GFS shows more blocking across the pole with the ECM showing a deep trough west of Greenland. Both produce snow to high ground in the 8-10 day period, perhaps wintry precipitation to low levels at times too with night frosts. No point talking further ahead just yet given the divergence in the northern hemisphere profile, though the signs are encouraging if cold weather is what you want.
    14 points
  13. The Gfs 00z shows high pressure building north into the uk during the week ahead along with unseasonable warmth for the south of the uk with temps reaching 17/19c..very nice BUT..then..hello Arctic..Boom
    12 points
  14. The GFS this morning shows a long drawn Northerly by next Thursday, With -5/-6/-7 850's covering a large swathe of the UK giving the potential for the 1st snowfalls for some..
    12 points
  15. Yes, GloSea5 performance has been good thus far (including stratospheric modelling for this period from runs even output back in mid-Sept), but ECMWF Monthly model was equally very keen on picking-out the potential (as now reflected by operational models, albeit devil will be in detail) for +ve MSLP building to NW and resultant cooler/colder flow into early Nov (refer to my earlier posts re this expectation). How much this emergent pattern will then sustain through November is quite another matter, but for now at least, there remains scant sign of 'mild 'n wild' Atlantic-borne weather within the latest (12z) ECMWF ensembles across the 15d period. With the GloSea prognosis equally considered, such a pattern still remains less likely than average during the early to 1st half of next month.
    10 points
  16. With regards to the northerly shown by the Euro and GFS it's probably worth saying that pressure looks relatively high (the bulk of the action is too far east) so that and the wishbone effect will probably prevent anybody outside north eastern Scotland from getting any snow out of it. That said, we should get frosts and it will feel absolutely freezing with a very cold, dry airmass.
    9 points
  17. The Gem 12z is now going for retrogression of the high with a scandi trough which is a big upgrade compared to its 00z which showed very limited retrograde with the high remaining over the uk before sinking south allowing the atlantic to flow over the top..this run is much more in tune with the current trend..to cold.
    8 points
  18. As others have stated, the air to the North of us has been under a warm airflow for a while now. Combined with above average sea temperatures in the region, we are unlikely to see low lying snow in the south, at least from the the initial blast. This area will rapidly cool under the northerly flow, and i believe the sea temperatures would too if sustained long enough. I believe the best shot at widespread snow would be the winds veering to E/NE for a time,as shown above. We are seeing this on some runs, and i would of thought with such a short distance across the sea that the air travels, that the air would be cold enough for inland low lying areas. The northerly flow does look as if it may more or less be sustained, in which case it would just be a matter of time before the air becomes cold enough for low lying snow in the south.
    8 points
  19. Today Eastern Scotland still under the influence of the North Sea low and the NE wind so cool with showers whilst the west of Scotland and N. Ireland should be dry and sunny. England and Wales also dry, perhaps less sunny, but rain spreading to the south west this evening moving ENE and petering out as it goes. On to the GFS. As the low to the south west drifts south it is quickly replaced by ridging from the Azores HP connecting to the HP to the NE. This leads to a high cell to the south of the country by Thursday 12z with a quite intense trough to the NW in the vicinity of Iceland. Ergo quite a tight gradient with a 130kt jet running just north of Scotland and and any systems running ENE confined to affecting the Latter As the week progresses the trough tracks east, pressure rises over Greenland and the European high pressure retrogresses NW to connect with the latter leaving this situation by 0600z Sunday. The pattern then amplifies with pressure building to the west and the trough slipping south east to be east of the Baltic by Tuesday. All of this has the potential to drag some quite cold air down from the north at the beginning of next week with snow a distinct possibility on high ground. Of course how the detail of this pans out will be resolved in the next few days. Just a quick glimpse on how the GFS proceeds. It actually rotates the upper pattern clockwise which results in the trough moving SW
    8 points
  20. Cheers yes I saw them in the gym- The execution of the 12z & its total coverage of the pole in high pressure with 3 main areas of low pressure around mid lattitudes means that for November 1st which coincides with the optimum low point of the next phase of the negative AO means that the 1st day reading could be -5 AO i will whizz through & check the records...
    7 points
  21. If we are going to Profit from at E/NE flow later in Nov and Dec we need a cold Northern Europe and Scandinavia, that is definitely one of the benefits from the forecast cool down early Nov - Scandinavia looks like its heading for an early "big freeze" starting late next week.
    6 points
  22. Oh i think he shouldit makes it more fun that way It brings out the inner child in most even if they won't admit it
    6 points
  23. You do know you shouldn't tease the customers like that Ian..
    6 points
  24. Morning all. I'm just enjoying a week away in North Devon, Woolacombe, but can't stay away from the charts! But I have noticed a big shift to a new blocking high setting up somewhere around Greenland or Iceland, whilst I know there is caution with that as previous years overdue heights around Greenland this year has proven to be very different! And yes your right I did cherry pick but who doesn't! As far as I'm aware this is what most people wan't to see unless your against cold weather which can't be many people considering winter is the busiest time at netweather
    6 points
  25. No disrespect SS,But I would say colder not cooler C.S
    6 points
  26. According to yesterday's ECM 12z op, we were only 10degrees latitude away from a modelled SSW (at the start of November!)
    6 points
  27. Greenland high's can be real teasers as has been pointed out in previous posts.Too far west such as shown in the later ECM frames and we are on the south side of cyclonic activity and in the milder westerlies. Not really a big deal at this early stage and liable to change in future runs but something to be aware of if new to chart watching.Yes the Aleutian vortex is already quite extensive and seems to be the major feature which is continuing to drive warm air north over the Canadian/Greenland Arctic weakening the vortex on the Atlantic side.
    5 points
  28. As you would expect with the mean looking like this, there are an increasing number of chilly looking GEFS 6z perturbations in various timeframes in early november..could be a cold bonfire night this year!
    5 points
  29. Halloween Going to be a Tad chilly 06z Has Temperatures ranging from 0c over the Highlands to 7C in the south C.S Edit Even colder 1st November daytime high of-1c over the Highlands to 4c in the south
    5 points
  30. 00z 06z The upgrades continue... far better warm air advection into the Canadian arctic on the 06z As a result, the core of the cold air mass currently over the Canadian arctic is removed. The core of the coldest air is situated over the northern tip of Canada on the 00z. The WAA fails to make inroads on the 00z Whereas on the 06z, the cold core is completely removed, and is infact heading straight for the UK.
    5 points
  31. The EPS maintains the flow from the northerly quadrant with temps below average for the ext period.
    5 points
  32. The GEFs also show a flow from a northerly quadrant throughout week 2 Interesting to note the the ensembles increase the influence of that Scandi trough over time suggesting an increasing risk of showers down north facing coasts to start but potentially affecting inland areas if disturbances crop up under low heights. 850 anomalies between 2 and 4 degrees below normal so in the wintry mix bracket in terms of precipitation at low levels, but good signs for Scottish resorts of a potentially lengthy spell of colder weather which should allow some significant snow to build up in the ski resorts. What a change from last year where the last 2 months of 2015 where southwesterlies dominated. That is not to say that we couldn't pull in air cold enough for snow at low levels though, but it is a case of getting the general pattern in place with the acceptance of the time of year and hoping this can be sustained or repeated at a time of year where snow would be more likely, that said it won't be long with the arctic rapidly cooling now as we enter late Autumn.
    5 points
  33. Looking at the anomaly charts the EC-GFS version continues to change emphasis between ridging having more effect and troughing. Indeed this morning the EC version has much as the chart above suggests posted by sb. NOAA on the other hand has, at least over the last two days, stayed with the idea of ridging being the most important player for the surface weather. In all my detailed checking over the years of these 3 anomaly charts, and at this time of the year, I cannot recall any such lengthy period with so much variance between hem. Even the NOAA outputs have been far from steady. No doubt much of it is due to the input from several tropical storms/hurricanes. Possibly also some kind of basic difference in the overall northern hemisphere upper air pattern as that which is giving such an unusually prolonged spell of blocking at 60N + in the main. Just why we have this feature this year I have no idea. Anyone out there with positive theories about this?
    5 points
  34. The ECM 0z for next Sunday with pressure rising to the NW and first signs of a tilt towards retrogression. Also Scandinavian snow cover develops as cold floods south over Northern Europe:
    5 points
  35. Pretty much! in short - it's a measure by Judah Cohen of how quickly snow cover advances from east to west across the Eurasian landmass south of 60N through October. This significance being that some of Cohen's work has shown correlation between the rate of advance of snowcover and the Arctic Oscillation (AO) during the following winter - namely the quicker the snow advances, the more negative the AO in the winter that follows tends to be. It should, however, be noted that the correlation is far from perfect and a good SAI is not always a guarantee of a negative wintertime AO...which even in itself is not a guarantee of a cold winter for the UK necessarily. It certainly helps though!
    5 points
  36. Hi folks, been a long time since I've been on here, in which time I've graduated, moved to Stockholm (well Vaxholm actually which is an island a few miles northeast of the city) and started a Masters in Meteorology! It's pretty chilly at the moment, around 5-6C with smirry rain today, and the models are hinting at the first snowfall here by the end of the month. I've been keeping an eye on the prospects for this winter, including the bizarre aborted QBO flip over the summer and the impressively negative Arctic Oscillation and snow cover advance for October, and I'll be releasing a winter forecast by the end of the month. Obviously living over here I'll have a bit less anxiety about seeing any of the white stuff but the setups needed for deep cold here are pretty similar to what we're looking for for Scotland. Anyway, I should be on here more regularly from now on, and I'll try to post some updates on the situation in Scotland as well as (hopefully) gloating about the snow over here LS
    5 points
  37. Yesterday's output takes the wave to 700 by day 10 shame that the Berlin graphical output doesn't kick in until Nov 1 because some of the predicted data re wave amplitude and temperature plus zonal flow reduction is impressive. Charts are there but the graphs bring it all together. Our understanding much better than 7 years ago. (And as I posted yesterday, the strat modelling far better) reminded of many false dawns in previous winters but to have a weak beginning for the strat vortex and a weak looking trop chappie on the Asian side really is a great place to be starting from for coldies and those amongst us who crave for extremes.
    5 points
  38. Looking at the gets anomolys I begin to wonder if the Euro anomoly isn't modelled quite right then we could see a west based -NAO develop at some point once the greeny ridging develops. the ECM 12z op brings this early on at day 8. Much easier to cope with these kind of model evolutions when the stakes are so low!
    4 points
  39. The reason behind the odd QBO locking in earlier this year was due to the strong el Nino event. That explains a lot, actually. In the ensemble with observed SSTs we find a strong and significant alignment of the ensemble members in the equatorial stratospheric winds in the 2 to 4 years after the strong ENSO event in 1997. This alignment also includes the observed QBO. No such alignment is found in the ensemble with climatological SSTs. These results indicate that strong warm ENSO events can lock the phase of the QBO. http://onlinelibrary.wiley.com/doi/10.1002/2016GL070751/abstract
    4 points
  40. Never rated the GEM. It is wrong far, far more often than it is right at that timescale so I wouldn't worry too much. I don't even bother looking at it these days.
    4 points
  41. Not a huge amount of change between the 00z and 06z to end October
    4 points
  42. We have had to remove a few off topic posts so just a reminder to keep your comments around the model outputs please. Thanks all.☺
    4 points
  43. Well it's not November the 5th yet but I think the blue touch paper has just been lit.
    4 points
  44. Lovely Autumn walk this morning just under 3mile,8c fantastic colours,nature really showing off.So much fresher this time of year. Passed a couple in full puffy jackets,woolly hats,2 layers underneath at least,gave me a strange look,me in my t shirt and shorts....no idea why!
    4 points
  45. A note of caution for coldies from the Gem 00z, not enough retrogression means the high stays over the uk before sinking south and allowing the atlantic over the top.
    4 points
  46. Perhaps,the fear would be by the time we get to winter proper the pattern will have moved on etc. Im hopefull though the pattern is a good sign for the coming winter or at least the first half. Perhaps a good chance of a front loaded winter. Well the last few winters it was thought that the second halves might deliver,so we waited and waited and waited but nothing ever happened ,so i dont mind too much if we do cash in our chips a bit early this yr.
    4 points
  47. Another essentially very dry GFS 0z this morning, certainly the signal remains for a pretty strong Greenland High as we move into November. Perhaps a WQBO doesn't preclude strong heights at Higher latitudes afterall
    4 points
  48. The evolution of the wave 2 disturbance is also nicely shown in the GFS forecasts with a significant tropospheric wave 2 pattern in the next couple of days. Then an increased wave 2 pattern can be seen at higher altitudes in the end of October with a westward phase tilt indicating upward propagation. The wave 2 seems to fade in the end of the forecast range and the vortex is forecasted to somewhat recover. Instead there seems to be an increased wave 1 when moving in to november
    4 points
  49. There is fairly strong support for cold northerlies into early November, though Knocker is right about the caveats, especially at this time range. Those expecting widespread snow from the northerly, though it is not unheard of at this time of year, are likely to be disappointed, because the Arctic will be anomalously warm for early November, partly as a consequence of the very amplified weather pattern, and unlike on 26/27 October 2012 (when, remarkably, many north-eastern districts saw snow in October despite the abnormal warmth around the Barents Sea that year), we are unlikely to tap into a localised cold pool to the east of Greenland. NOAA's 8-14 day outlook strongly highlights the impending north-western blocking: http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php With the MJO likely to hang around phase 7-8, a transition to less settled and rather cool weather is likely into early November with frequent north-westerly and northerly winds, perhaps cold enough for some wintry precipitation in the north if the pattern keeps up for long enough into the first half of November, but a less cold west to north-westerly type could also develop. However, at present things do look remarkably different to how they did this time last year.
    4 points
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