Eagle Eye

This looks to be a slight displacement but notice that the main vortex is placed over Greenland so watch for high latitude North American blocking signals into the future as the upwards wave movement from that direction could potentially split the Vortex but only if the Eurasian-Pacific warming signal keeps putting pressure on the main vortex shifting and hence the vertical baroclinic tilting keeps the polar-night jet from weakening the subtropical Eddy driven jet. If we can get that to happen then that'll be our best chance assuming this is correct. The UK pattern from the -EAMT relies heavily on the US pattern so I wouldn't start looking at that just yet but note the high latitude North American-Greenland blocking may be a signal with phase 8 Supported (I guess) by the composites though I'm hoping that it acts like a February signal (second image) as the first one might not be a strong enough signal though note that the MJO phase is fairly significant in creating that block in January compared to not really in February. So Im wanting a mix of the two . The MJO amplification of that phase is bery difficult to tell though as there's a lot of split at the moment. Anyway, just my musings on what could possibly go right for us but as we keep up the pressure on the Vortex then I think we'll get a more substantial chance as the NAO looks to be heading more negative over time by mid to late January and that would create a large Trop-Strat temperature difference as well as vortex tilt difference. I'm waiting for the next Stratobserve update though to see if there's more support from the ensembles for a Wave-2 increase by mid month as that's typically how a PJO (polar-night jet oscillation) influenced SSW happens with a Wave-1 onset before Wave-2 split. Its a lot of hope but the hope does have a little backing at least.

Even though the other teleconnections are fairly under amplified (such as the MJO), as long as the AAM lag remains +VE there's always a chance even if its not that much, it's there . That chance looks to build up mid month onwards based off the AO trend especially and its possible that we're moving towards a rebound of +VE EAMT by early Janaury and that feedback may respond with a Greenland or Scandi high depending on the PNA pattern or whether or not there's a Eurasian block. It may not be the best chance but I don't see an reason why shots of PM and/or a short-fetch Easterly aren't possible in the first couple weeks of January. Right now, the chance is low but but the chance always starts of as low and slowly building. I think the beat chance away from a SSW will be from a possible +VE EAMT at the end of the first week of Janaury and from mid month onwards that rise in AAM plus the downstream effects should increase the cold chances though until (if) the +VE EAMT happens the downstream interactions will be difficult to tell though I may have a go later with a general forecast assuming that one happens. It seems to be the general way that the GWO is moving towards and the collapsing Eurasian feedback could result in a pressure gradient difference over the mountains (hence +VE EAMT) as temperature and pressure flux moves south. Let's just see how we go.

Hanging on by a baroclinic tilt

GFS moving back to re-invigorating the Strat zonal pattern long-term with less of a baroclinically tilted upper Trop-Strat gradient and cools down the Strat polar vortex fairly significantly right at the end of the run (I.e a return to the polar-night jet). Remains on the stronger side of the zonal winds pretty much right from the start and I fear its not something we will know till mid way through January at the earliest. Is it picking up a new trend or just being over the top with the zonal wind recovery? Such an ensemble split that we can't really know as of yet.

And I've been provided with a voice . Anyway, its great to have so many knowledgeable people on this forum who know stuff about Meteorology, Physics, Manchester United transfer policy etc... But its always going to be that some people will try and ruin the fun by pointing out the facts rather than the hopes . Just kidding, Meteorology is a very opinion based subject becuase of the nature of having to look at model trends rather than looking at just one run because a trend towards something generally fares better than 1 run. With more and more different things to look at, piecing together a 3D model of the atmosphere is very difficult to do and I think that's what non weather enthusiasts don't get. The weather doesn't just happen at the surface, it happens pretty everywhere in the Atmosphere (even the Mesosphere can affect things as its so close to the Stratosphere) because theres particles that are moving. There's complicated processes involved over the span of just a few hours so naturally if some of the data is a bit off then that will lead to even bigger changes down the line. Forecasting is quite literally a forecasters nightmare because we can't just look at one GFS run and assume it to be true. Think about it, we've got so many different models almost all good at their own thing with their own little quirks. We've got so many different teleconnections that some of them I don't think have ever been talked about on here. Often these show mixed signals because there is rarely a perfect pattern evolving and to add to that we've got Strat influence, zonal influence, the way that energy is transferred up and down and all of the different general types of weather that we can expect. It's no wonder the weather is loved by so many but understood by so few but theres many people on here who have a ridiculously good understanding of the weather and are helping others understand what the professionals go through when long-term forecasting and why its so difficult. We can all have our own opinions on what will be the most influential background signal or what one low will do and its great. Its just a shame when some other people can occasionally ruin it for others (not the person I quoted of course just a few people but I'm not naming any names and it's not necessarily the people writing off January, they have some good reasons to, just as we have many reasons not to as well). Some of the occasional 'name calling' can be painful to watch because it's just not needed. The 'name calling' is very rare though and can I just thank the mods for what a wonderful job they do in calming us down when we get into perhaps 'anger' over a run or something. Remember, it's just the weather and there's lots of different ways that charts can be interpreted.

Tight isobar's and hence the wind flowing along them quite strong as you would expect. With some convection across the channel and south coast parallel to the sharp SE quadrant of the low lifting up some moisture and seemingly more near surface/slightly above boundary layer focused cold air advection and a fairly sharp Tropospheric temperature and wind vertical gradient. This combined with a lobe of lower Tropospheric relative vorticity has led to some fairly sharp coastal riding showers.

Less of a large baroclinic tilt on the latest Stratobserve update though the tilt is still there (and holding firm it's just the Trop pattern that's become slightly less stretched), the 'amplification' of the Tilt has weakened some what but we'll only know closer to time whether this run starts the trend away from a highly active polar-night jet oscillation or just a minor wobble as of yet. It may be due to the Wave-1 height decreasing as the Wave-2 becomes stronger so we may still gain ground on putting pressure on the Strat in the long-term though the GFS is largely out on it's own with the increase of Wave-2 at the end of it's run. Nothing to be alarmed at for now as this is still a very good position with the baroclinic tilt still very much being there are the weakening of the Strat zonal pattern still the most likely of outcomes it's just how tilted it gets and how weak it gets. I won't worry too much unless we see the decrease in tilting strength to become a trend in the future; just a minor wobble for now. Plus the GFS looks to be some sort of outlier in most of the fields (I think it's the 00Z run so slightly out of date, Strat looking much better on recent runs). Today Vs yesterday, little difference in the Trop pattern so the thermal gradient may be slightly less but it's quite possible the GFS is under-amplifying the Eddy pattern especially long-term. Surface to Trop -VE NAM (AO) forms possibly due to a kick from the recent +VE AAM rebound, the MJO amplification having some implications and the -VE mountain torque event retracting the East Asian Jet. Unfortunately for us we're stuck on the wrong side of that as the energy is probably scattered to just introduce some more push into the Euro ridge but not really enough to form any Scandi blocking due to a more easterly based Eurasian feedback's properties not being able to push up WAA on it's Western edge into the Scandinavian region and instead the feedback results in the Kazakhstan high that doesn't really help us all that much though the exact formation area is of course fairly dubious. It's still good to know that this sort of pattern does support a sustained amount of thermal wave flux vertically integrating into the Strat and so perhaps the GFS is over-estimating the zonal wind pattern. This formation of the quickly collapsing high pattern may be enough to re-invigorate some +VE EAMT though I'm not sure what the pressure patterns would have to be for that and it's mainly based on the GWO progression towards phase 4/5 (phase 5 is a gain of mountain torque) and if we can get a significant enough even then slowly AAM could start ticking up fairly well especially if the MJO progression towards phases 6 and 7 is more amplified than currently forecast. The GFS suggesting that it's a slow movement towards that phase as we wait for the pressure gradient to increase so for now forecasting one would be a big call as it's very possible that it's a quick gain event followed by a loop back round of the GWO as the zonal lengthening of waves in the East Asian region just keeps the repeating pattern going. The last significant Rossby thermal transfer inducing +VE EAMT event was back in late October. You can see the packet slowly make it's way across the Northern Hemisphere but the stagnant North American trough may have caused it to result in a less helpful Atlantic extension and push back of MJO effects though it did increase AAM and so we were in for a relatively good pattern shape with another wave train in late November that was more helpful in just causing zonal flux havoc across the mid-latitudes and the eventual movement towards the large -VE NAO also linked with the steady +VE AAM state around the time. You can see there's not much of the sorts on the forecast at the moment but keep your eyes peeled because if we're lucky enough to gain +VE EAMT in a pattern where there's high pressure located over North America and the MJO is better placed than currently forecast. So away from the Strat signal and with how slow these things tend to evolve, late January/early February may be the next best time for a cold pattern though I think it'll mainly have to be Rossby packet and +VE AAM as the MJO looks to be in COD by then. Right now, it's probably highly unlikely as it just looks to be a cycle in the repeating pattern of EAMT events but I want to dream just this once (okay maybe a few times). Original post: https://community.netweather.tv/topic/98132-model-output-discussion-christmas-week-and-beyond/?do=findComment&comment=4779591

Less of a large baroclinic tilt on the latest Stratobserve update though the tilt is still there (and holding firm it's just the Trop pattern that's become slightly less stretched), the 'amplification' of the Tilt has weakened some what but we'll only know closer to time whether this run starts the trend away from a highly active polar-night jet oscillation or just a minor wobble as of yet. It may be due to the Wave-1 height decreasing as the Wave-2 becomes stronger so we may still gain ground on putting pressure on the Strat in the long-term though the GFS is largely out on it's own with the increase of Wave-2 at the end of it's run. Nothing to be alarmed at for now as this is still a very good position with the baroclinic tilt still very much being there are the weakening of the Strat zonal pattern still the most likely of outcomes it's just how tilted it gets and how weak it gets. I won't worry too much unless we see the decrease in tilting strength to become a trend in the future; just a minor wobble for now. Plus the GFS looks to be some sort of outlier in most of the fields (I think it's the 00Z run so slightly out of date, Strat looking much better on recent runs). Today Vs yesterday, little difference in the Trop pattern so the thermal gradient may be slightly less but it's quite possible the GFS is under-amplifying the Eddy pattern especially long-term. Surface to Trop -VE NAM (AO) forms possibly due to a kick from the recent +VE AAM rebound, the MJO amplification having some implications and the -VE mountain torque event retracting the East Asian Jet. Unfortunately for us we're stuck on the wrong side of that as the energy is probably scattered to just introduce some more push into the Euro ridge but not really enough to form any Scandi blocking due to a more easterly based Eurasian feedback's properties not being able to push up WAA on it's Western edge into the Scandinavian region and instead the feedback results in the Kazakhstan high that doesn't really help us all that much though the exact formation area is of course fairly dubious. It's still good to know that this sort of pattern does support a sustained amount of thermal wave flux vertically integrating into the Strat and so perhaps the GFS is over-estimating the zonal wind pattern. This formation of the quickly collapsing high pattern may be enough to re-invigorate some +VE EAMT though I'm not sure what the pressure patterns would have to be for that and it's mainly based on the GWO progression towards phase 4/5 (phase 5 is a gain of mountain torque) and if we can get a significant enough even then slowly AAM could start ticking up fairly well especially if the MJO progression towards phases 6 and 7 is more amplified than currently forecast. The GFS suggesting that it's a slow movement towards that phase as we wait for the pressure gradient to increase so for now forecasting one would be a big call as it's very possible that it's a quick gain event followed by a loop back round of the GWO as the zonal lengthening of waves in the East Asian region just keeps the repeating pattern going. The last significant Rossby thermal transfer inducing +VE EAMT event was back in late October. You can see the packet slowly make it's way across the Northern Hemisphere but the stagnant North American trough may have caused it to result in a less helpful Atlantic extension and push back of MJO effects though it did increase AAM and so we were in for a relatively good pattern shape with another wave train in late November that was more helpful in just causing zonal flux havoc across the mid-latitudes and the eventual movement towards the large -VE NAO also linked with the steady +VE AAM state around the time. You can see there's not much of the sorts on the forecast at the moment but keep your eyes peeled because if we're lucky enough to gain +VE EAMT in a pattern where there's high pressure located over North America and the MJO is better placed than currently forecast. So away from the Strat signal and with how slow these things tend to evolve, late January/early February may be the next best time for a cold pattern though I think it'll mainly have to be Rossby packet and +VE AAM as the MJO looks to be in COD by then. Right now, it's probably highly unlikely as it just looks to be a cycle in the repeating pattern of EAMT events but I want to dream just this once (okay maybe a few times).

It's like spot the difference . Have the models all of a sudden decided to become 99% accurate at 11/12 days out because I'm all for it (makes the ride up to any future cold spells a bit boring though, part of the reason we love the ride is the minor differences causing major differences long-term). I think people on here forget that Scotland exists and that if you're snow starved you can probably look at their thread and enjoy the pictures of the snow that they get. I think it'd be easier if we all moved to Scotland though I don't get the feeling the Scots would like that (sorry mods me going off topic and all that).

Sort of agree but there are still signs of it re-stengthening in phase 7 like I said and I'd rather that than nothing. It'll still have some backing of an amplified pattern as long as it stays fairly far away from COD anyway as it can still help retract the downstream jet when combined with the East Asian Jet Retraction signal in reply to the -VE EAMT. Of course, the Atlantic zonal pattern still stays fairly strong initially but as the energy starts making its effects downstream it could well weaken the Atlantic zonal pattern assuming it interacts with an in-situ High over either Notth America or somewhere similar. The timing of this is important as to the weakening and chipping away of such an Atlantic zonal pattern but I see no reason as to not keep up hope that we'll get lucky because hope will keep up sane for now. It's not unfounded hope either just relies on a bit of luck to fall our way. it's not that strong of a zonal pattern beyond mid January anyway. The intiial VI from the development of the polar-night jet should essentially start slowing down soon and the Subtropical Eddy jet upwelling into the Strat could likely pish the polar-night jet abnormally and cause a refracting wave to bend it baroclinically (or however you spell it) and weaken the Strat zonal pattern into the second week of Janaury. Even if this only causes a minor SSW or doesn't cause one whatsoever it doesn't matter much as we could well see that amount of upward Wave flux with an increasing Wave-2 amplification signal to cause the anomalous weak Strat zonal jet to downwell and weaken the Trop to at least fairly average zonal levels. Plus the GWO may be moving back towards regaining some AAM through a +VE mountain torque event and with this kind of repeating pattern due to the relatively unbalanced balance () over the East Asian mountains and how the pressure evolves, a regain of mountain torque at least once is unlikely. The recent regaining signal was unfortunately overriden by the downwelling of the polar-night jet but if the thermal transfer into the Strat weakens that signal quite quickly then we may be luckier the 2nd time around. Original post: https://community.netweather.tv/topic/98132-model-output-discussion-christmas-week-and-beyond/?do=findComment&comment=4779138

Away from long-term and more short-term, we could see some local date records being broken in Europe with warm air sourced from Africa and just off the coast of Africam its apparent moisture rich look is just because of the time of the year and really its just because theres some moisture adverting from the South West due to the presence of the low and that moisture is slowly transporting across the Atlantic (possible Atmospheric River, the transport looks fairly tight, I mentioned the possibilityof a secondary one a few days ago) so the area its sourcing it's advection from is anomalously moisture rich in the first place. Original post: https://community.netweather.tv/topic/98132-model-output-discussion-christmas-week-and-beyond/?do=findComment&comment=4779161

A few too many Christmas drinks at Devon Live it seems. Funny thing is the 'fueling powerful jet stream' that they talk about is likely to do pretty much the opposite and just set up the Atlantic as we're seeing in the forecasts. I'm not even sure who their source is because I want to know what model they're using to come up with that result . Maybe part of the new model called the "Just Kidding ensemble forecast". I think we're going to be zonal for the next couple weeks and there's very little escape of that despite what Devon Live say but beyond that forecasting becomes more difficult. One thing we can have a good laugh over is some of these online newspapers such as Devon Live and the far fetched scenarios they make up.

The models(just the GFS, not sure about the other ones) have been under progressing and/or amplifying the MJO pattern recently. It is possible that they're doing the same for the future as well. Though its unlikely to move away from the so called COD initially, the latest run suggests we may see a re-amplification of the RMM values over phase 7 by the second week of January and if that becomes a trend then cold for late January into early February may be a fair possibility even without a SSW. ECM extended less interested and probably more likely but still keeps the 'interest' up before moving on to the generally more nondescript phases 8 and 1. This slow move towards phases 8/1 is likely to happen which generally doesn't fabour -VE NAO though being quite nondescript in nature, will likely not have too much effect until it enters phases 2/3 in the Indian Ocean which favours a +VE NAO signal and by then we'll be ready for another MJO cycle. I'll talk more about the MJO either later today or later this week though. Original post: https://community.netweather.tv/topic/98132-model-output-discussion-christmas-week-and-beyond/?do=findComment&comment=4779113

Away from long-term and more short-term, we could see some local date records being broken in Europe with warm air sourced from Africa and just off the coast of Africam its apparent moisture rich look is just because of the time of the year and really its just because theres some moisture adverting from the South West due to the presence of the low and that moisture is slowly transporting across the Atlantic (possible Atmospheric River, the transport looks fairly tight, I mentioned the possibilityof a secondary one a few days ago) so the area its sourcing it's advection from is anomalously moisture rich in the first place.

Sort of agree but there are still signs of it re-stengthening in phase 7 like I said and I'd rather that than nothing. It'll still have some backing of an amplified pattern as long as it stays fairly far away from COD anyway as it can still help retract the downstream jet when combined with the East Asian Jet Retraction signal in reply to the -VE EAMT. Of course, the Atlantic zonal pattern still stays fairly strong initially but as the energy starts making its effects downstream it could well weaken the Atlantic zonal pattern assuming it interacts with an in-situ High over either Notth America or somewhere similar. The timing of this is important as to the weakening and chipping away of such an Atlantic zonal pattern but I see no reason as to not keep up hope that we'll get lucky because hope will keep up sane for now. It's not unfounded hope either just relies on a bit of luck to fall our way. it's not that strong of a zonal pattern beyond mid January anyway. The intiial VI from the development of the polar-night jet should essentially start slowing down soon and the Subtropical Eddy jet upwelling into the Strat could likely pish the polar-night jet abnormally and cause a refracting wave to bend it baroclinically (or however you spell it) and weaken the Strat zonal pattern into the second week of Janaury. Even if this only causes a minor SSW or doesn't cause one whatsoever it doesn't matter much as we could well see that amount of upward Wave flux with an increasing Wave-2 amplification signal to cause the anomalous weak Strat zonal jet to downwell and weaken the Trop to at least fairly average zonal levels. Plus the GWO may be moving back towards regaining some AAM through a +VE mountain torque event and with this kind of repeating pattern due to the relatively unbalanced balance () over the East Asian mountains and how the pressure evolves, a regain of mountain torque at least once is unlikely. The recent regaining signal was unfortunately overriden by the downwelling of the polar-night jet but if the thermal transfer into the Strat weakens that signal quite quickly then we may be luckier the 2nd time around.

Like I said, theyve been under amplifying the MJO for a while (well the GFS has anyway), you're entitled to your opinion but its a step in the right direction to see that loop try and amplify the MJO and a step in the right direction is purely that. Simply put, we're in a bad position but its getting slightly better and that is and always will be better than nothing.

The models(just the GFS, not sure about the other ones) have been under progressing and/or amplifying the MJO pattern recently. It is possible that they're doing the same for the future as well. Though its unlikely to move away from the so called COD initially, the latest run suggests we may see a re-amplification of the RMM values over phase 7 by the second week of January and if that becomes a trend then cold for late January into early February may be a fair possibility even without a SSW. ECM extended less interested and probably more likely but still keeps the 'interest' up before moving on to the generally more nondescript phases 8 and 1. This slow move towards phases 8/1 is likely to happen which generally doesn't fabour -VE NAO though being quite nondescript in nature, will likely not have too much effect until it enters phases 2/3 in the Indian Ocean which favours a +VE NAO signal and by then we'll be ready for another MJO cycle. I'll talk more about the MJO either later today or later this week though.

Hope everyone had a great Christmas and you are looking ahead at the New Year. Signs that we may get a SSW are slowly starting to appear despite the intensification of the Strat polar vortex (polar-night jet) and its downwelling into the Trop pattern. The good news about the two connecting is that the subtropical jet fired up by Eddy thermal transfer has connected up with the polar-night jet. The polar-night jet as it intensifies zonally, it gets colder. So the connect up with the thermal Eddy's is good as the temperature gradient increases between the Trop and Strat, pronounced upwards wave flux starts increasing and warming up the thermal outer wave on the Strat which increases the temperature contrast between the Pacific warming and the much colder polar vortex. That helps to abnormally oscillate and displace the Vortex but unless we see a Wave-2 increase after the initial Wave-1 displacement it may all be for nothing as displacements Pacific side are typically more minor warming and favour cold for North America whereas the European pattern is less disturbed. If Wave-2 does increase then that favours a split vortex which typically ends up in a major SSW and favours a colder pattern for us as the change in zonal Strat winds (to reversal if we're lucky) downwells to the Trop. So we need to be wary that a SSW does not guarantee cold for us especially in a Wave-1 setup (though Wave-1 followed by Wave-2 is a very good setup) and so we've got to hope that the Wave-1 increasing does onset the initial SSW but we see a quick Wave-2 increase as well. Its too far out to guarantee we'll get anywhere near a SSW yet but we do need to be wary of how the Wavenumber pattern evolves as well.

Right well it's time for my first proper look long-term since before Christmas so hope you all had a great Christmas and boxing day and are looking forward to the New Year... Time to watch how the seven nation army are evolving and by that I mean the AAM, MJO, Stratosphere, Troposphere , GWO and I'll chuck in the QBO for good luck! Starting with the AAM. Typically if we want a more blocked pattern with colder prospects for us we want a positive(+VE) AAM as the momentum increase which is directly related to the total integration of torque in the Atmosphere as proved by the equation: dM/dT = r x F dM being the differentiation of Momentum dT being the differentiation of Torque And r x F being the distance from the origin times the Force. r x F being the equation to find out torque. Hence momentum is the product of the total torque in the atmosphere (well, essentially, there may be more to it) Equation thanks to Reading University, anyway... The reason momentum increasing in the Atmosphere is good for blocking prospects is because torque is the rotational force around a pivot point and we know that momentum is directly correlated with the total torque. That torque will draw warm air up and slow down the westerly jet stream due to increased easterly wind integration in the Atmosphere and so an increasing or sustained +VE AAM should theoretically weaken the zonal winds. Well, if we look at the zonal winds in the Trop pattern from mid to late November through to early December we see a fairly weak zonal pattern evolving just as the sustained +VE AAM at the time suggested there would be. It's good as it shows the link between the two (though this is excluding external facts, the MJO and AAM seem to have been the main reasons for this though) and can be used fairly accurately as a forecasting tool if you include the GWO and therefore you get yourselves a fairly decent signal for working out long-term signals though there are no real numbers that I can put to it in terms of how long or how strong, you've just got to go on your gut instinct. The upper Trop pattern for November suggests that northern blocking is more likely (slower winds typically mean a more oscillating jet and transfer of heat polewards) and we did get a lot of northern blocking especially towards the end of the month. I think the zonal looking Atlantic is mainly to do with how the first part of the month evolved because the second half I don't think saw such a strong Atlantic setup though it did throw a few spanners in the works, that was more due to shortwaves and areas of stretched tropical influence quite late into November/early December (ish) I think it might have been. The current +VE AAM does look to be slowly fading as we are losing (negative or -VE) some mountain torque (likely East Asian as that seems to be a pattern trend emerging where collapsing waves of energy followed by increased energy waves with other interactions as well are evolving) over the next few days and that will likely mean that early January does not offer us much hope (unfortunately Vortex Intensification or VI in the Strat has dismissed much hope I had of energy being scattered well by the anomalous East Asian Jet Retractions and/or Extensions) but there is the possibility of a Scandi high if we can get a well formed Eurasian Feedback to this loss of mountain torque as the one last time that could have delivered a Scandi high waned slightly too early and we ended up with the dreaded Euro high. Shows how little one thing changing can have either good or bad consequences on how our weather evolves. I'll go over the Scandi high chances later though. As we lose this mountain torque, the AAM may go fairly -VE but I think that's unlikely as it still doesn't want to interact properly with the La Nina oceanic base state and so our +VE AAM chances should remain. Slowly there are tentative signs that we may regain this torque long-term on the CFS and that does make sense with how the repeating rebound pattern we seem to be entering works. The pressure signals are likely quite differing over the East Asian mountains in such an un-amplified but helpful pattern right now as things generally flip-flop when we get into these sorts of situations. Until the AAM or MJO signals get stuck in strongly -VE or phase 2/3 respectively, I think these rebounds will keep happening and if we can sustain one for just long enough at a high enough amplitude, it may be enough to give us some longer-term cold prospects away from a SSW but right now I probably find that unlikely to happen over the coming month or so. Quicker cold events cannot be ruled out of course due to the possibility of a Scandi high and beyond that it's hard to tell with almost all Teleconnections fairly neutral it takes just a little movement to create a lot of 'noise' and we could see the development of a Greenland high though it's looking fairly unlikely for now. That's three of the 7 nation army done now, onto the MJO... On the border of phase 5/6 and slowly moving towards being a fairly substantial phase 6 just slightly less amplified than it was in November so under amplified is probably a yes but it's still fairly amplified and we aren't really losing the signal and there's still a few ensembles showing the possibility of it keeping amplification towards phase 7 but the VP shows that we're probably finding the signal beyond phase 6 difficult to interpret and probably we're likely to see it lose amplification and slowly move into the so called COD. So we're probably relying on phase 6 over the next week or so (14-21 day lag probably) and a rebound of AAM (6 day lag initially but can be much longer) to time themselves together and we do get some form of mid to high latitude blocking. An entire pattern flip is probably unlikely as it's usually an amplified phase 7 that we would want for that but that doesn't mean we can't see some form of Scandi or Greenland blocking with a -VE AO by mid to late January. Obviously, the MJO amplification probably won't spike a significant amount of momentum to form that kind of blocking but if it can time itself well with a gain of East Asian mountain torque scattering thermal and zonal energy downstream and maybe allowing for some Eurasian (ish) blocking if it allows for an East Asian Jet Retraction. One of the main reasons why I wouldn't rule January out for cold (especially the second half) is just look at that scatter beyond phase 6 and it's clear that the models aren't handling the MJO well, maybe the ECM is doing better but the amount of spread means that you cannot really be sure off anything so long-term forecasting is likely to be either exactly correct or very far off or anywhere in-between there. Onto the firth and sixth ones and that's the Strat and Trop patterns... First thing to note is that Wave-2 does look fairly strong but dips towards the 10th as Wave-1 takes over, I think this is where the initial onset of a SSW would have to happen with strong baroclinic tilting and a large thermal gradient displacing the Strat vortex. The initial onset would then have to be followed by a weakening or dipping of Wave-1 amplitude as we see a second thermal wave forming probably around the North Atlantic area. This would be the best chance of a Polar-Night Jet Oscillation (PJO) type of SSW as that would put a cooling Strat vortex on either side of 'outer riding waves' and that thermal gradient cut push through the middle of the vortex and split it in two. I'm definitely not saying that's what's going to happen here but that is exactly how a PJO onset happens and a PJO is almost entirely linked with a major SSW. So if we can get Wave-1 displacement followed by Wave-2 split then that amount of upward wave flux would likely be enough for strong downwards reflection and a quick weakening of the Strat zonal wind downwards. At the moment that's still unlikely but there's a fair number of ensembles taking the Wave-2 amplitude and ramping it up right towards the end of the run. If that becomes the trend then we can become excited but for now I'd stay calm as that's quite a few hours away. The zonal winds continue to support the idea that a Wave-1 displacement would at least weaken the Strat vortex and that may translate itself into a slightly weaker (though maybe still zonal) Trop from mid-January onwards but only if we see some downward zonal wind reflection. It means that even if the MJO phase 7 isn't strongly amplified we might see at least a slight weakening of the Trop zonal pattern. So looking long-term is probably our best solution now with a slight increase in cold chances and hopefully a SSW happens with Wave-1 followed by Wave-2 but that'll only happen if we're lucky. We've got to hope that the Eurasian warming signal moving across the Pacific is followed by some sort of North Atlantic (ish) warming signal with increase Eddy's from the North America-Greenland area in the Troposphere and propagating vertically. In the Troposphere... Pretty much only the Atlantic is looking largely zonal with the East Asian Jet Retraction helping everyone except us. Still think that the Eurasian feedback across 90E might spread further West and we can get some energy into the Euro high amplifying it but how much is difficult to tell. If we're lucky it interacts with the more Westerly Eurasian Feedback. What looks more likely is the Eurasian Feedback staying too far East and any interaction will be un-interesting and it'll just push the Euro high up slightly. Possibility of a Scandi high remains there but what is most likely is a continuation of this pattern till mid January unless the Eurasian Feedback pushes much further West than is currently forecast. 6 of the 7 nation army done, 1 more to go and that's the QBO... QBO is still in the Westerly Phase but it seems to slowly be weakening and will likely turn to Easterly but that'll likely be after this Winter is over. Just good that the sleeper signal for the zonal wind is at least weakening and so may start having less of an effect as we slowly go over time. I'm not really focused that much on the QBO as I still don't fully understand how it works. So overall, the first half of January does favour a zonal pattern as people are saying but the increased tilting between the Trop and Strat layers (especially the upper Strat) could really help with the thermal transfer, in turn weakening the 10-1hpa zonal values fairly well. Wave-1 dominance looks to stay fairly stable so displacement rather than split would be the most likely way a SSW could happen if it does but a few ensembles are showing Wave-2 increasing as Wave-1 and hopefully that becomes a trend but I find it unlikely. What it could do is reflect some of the upward wave movements down and slow down the zonal winds in the Trop pattern so mid-late January we may see that form of downwards (non SSW related) connection between the Strat and the Trop. Away from the Strat pattern and the Trop pattern will mainly rely on the MJO phase 6 and 7 being more amplified than currently forecast and despite the rebounding +VE AAM, it's probably going to continue to be a forecasters nightmare as per long-term forecasting with multiple contrasting signals and a significant amount of spread on the Teleconnections. As long as it remains fairly neutral then rebounds in AAM from mountain torque events especially can help us in the longer term so it's not all dire in the Trop front but the MJO looks mainly uninteresting unless we get right at the top end of the amplification of the ensembles. Probably the best Strat pattern is the we see an initial Wave-1 onset causing the oscillation of the polar-night jet and an unstable thermal transfer from vertical Rossby waves and Eddy Heat Flux also increasing into the Strat before Wave-2 splits the displaced Strat vortex. It's unlikely at the moment but not impossible with a fair number of ensembles increasing the Wave-2 amplitude right towards the end of their runs and the 12Z GFS showing the possibility of how one would evolve if the Wave-2's strength did increase (do not take 1 run in isolation, I'm just using this as an example). This would significantly impact the stability and inertia of the polar-night jet and a Wave-1 followed by Wave-2 would likely cause a major SSW as long as it's caused by a fairly strong amount of upwards wave flux. One of the worse ways that the Strat pattern could evolve would for polar-night jet to continue to intensify and overpower the Eddy-driven subtropical jet and so the amount of thermal flux reaching the Strat would be fairly minimal. This situation wouldn't see a lot of pressure being put on the vortex and it wouldn't be sustained enough to cause that snap. It's a possibility but relies on the polar-night jet's downwelling to the Trop to be fairly continuous which just like the best possible scenario is fairly unlikely. The most likely scenario right now (in my opinion) is that we see increase Wave-1 strength with a slight increase in Wave-2 after the Wave-1 signal but not enough to cause a split and so at best we end up with a displaced Strat (but maybe not a SSW) and typically the cold is better positioned for North America in that scenario as the downwelling of any zonal changes happens. We do need to check up on how the Wave-2 pattern evolves though because if we do see it strengthen and we do end up seeing the best case scenario that is probably one of the better ways a SSW could set up for us and the large thermal flux and change over time would likely cause a major SSW. Like I say though, that remains unlikely for now. The Trop signal beyond the early part of January remains fairly mixed and so I wouldn't write cold off just yet. Without a SSW, I'd say that a zonal setup is slightly favoured right now but that's only because of the seasonal setups and general un-amplified evolving pattern right now and if we can see the AAM rise sharply again relatively soon then we can think about cold prospects away from a SSW for mid to late January so I certainly wouldn't write it off whatsoever. Original post: https://community.netweather.tv/topic/98132-model-output-discussion-christmas-week-and-beyond/?do=findComment&comment=4778855

Right well it's time for my first proper look long-term since before Christmas so hope you all had a great Christmas and boxing day and are looking forward to the New Year... Time to watch how the seven nation army are evolving and by that I mean the AAM, MJO, Stratosphere, Troposphere , GWO and I'll chuck in the QBO for good luck! Starting with the AAM. Typically if we want a more blocked pattern with colder prospects for us we want a positive(+VE) AAM as the momentum increase which is directly related to the total integration of torque in the Atmosphere as proved by the equation: dM/dT = r x F dM being the differentiation of Momentum dT being the differentiation of Torque And r x F being the distance from the origin times the Force. r x F being the equation to find out torque. Hence momentum is the product of the total torque in the atmosphere (well, essentially, there may be more to it) Equation thanks to Reading University, anyway... The reason momentum increasing in the Atmosphere is good for blocking prospects is because torque is the rotational force around a pivot point and we know that momentum is directly correlated with the total torque. That torque will draw warm air up and slow down the westerly jet stream due to increased easterly wind integration in the Atmosphere and so an increasing or sustained +VE AAM should theoretically weaken the zonal winds. Well, if we look at the zonal winds in the Trop pattern from mid to late November through to early December we see a fairly weak zonal pattern evolving just as the sustained +VE AAM at the time suggested there would be. It's good as it shows the link between the two (though this is excluding external facts, the MJO and AAM seem to have been the main reasons for this though) and can be used fairly accurately as a forecasting tool if you include the GWO and therefore you get yourselves a fairly decent signal for working out long-term signals though there are no real numbers that I can put to it in terms of how long or how strong, you've just got to go on your gut instinct. The upper Trop pattern for November suggests that northern blocking is more likely (slower winds typically mean a more oscillating jet and transfer of heat polewards) and we did get a lot of northern blocking especially towards the end of the month. I think the zonal looking Atlantic is mainly to do with how the first part of the month evolved because the second half I don't think saw such a strong Atlantic setup though it did throw a few spanners in the works, that was more due to shortwaves and areas of stretched tropical influence quite late into November/early December (ish) I think it might have been. The current +VE AAM does look to be slowly fading as we are losing (negative or -VE) some mountain torque (likely East Asian as that seems to be a pattern trend emerging where collapsing waves of energy followed by increased energy waves with other interactions as well are evolving) over the next few days and that will likely mean that early January does not offer us much hope (unfortunately Vortex Intensification or VI in the Strat has dismissed much hope I had of energy being scattered well by the anomalous East Asian Jet Retractions and/or Extensions) but there is the possibility of a Scandi high if we can get a well formed Eurasian Feedback to this loss of mountain torque as the one last time that could have delivered a Scandi high waned slightly too early and we ended up with the dreaded Euro high. Shows how little one thing changing can have either good or bad consequences on how our weather evolves. I'll go over the Scandi high chances later though. As we lose this mountain torque, the AAM may go fairly -VE but I think that's unlikely as it still doesn't want to interact properly with the La Nina oceanic base state and so our +VE AAM chances should remain. Slowly there are tentative signs that we may regain this torque long-term on the CFS and that does make sense with how the repeating rebound pattern we seem to be entering works. The pressure signals are likely quite differing over the East Asian mountains in such an un-amplified but helpful pattern right now as things generally flip-flop when we get into these sorts of situations. Until the AAM or MJO signals get stuck in strongly -VE or phase 2/3 respectively, I think these rebounds will keep happening and if we can sustain one for just long enough at a high enough amplitude, it may be enough to give us some longer-term cold prospects away from a SSW but right now I probably find that unlikely to happen over the coming month or so. Quicker cold events cannot be ruled out of course due to the possibility of a Scandi high and beyond that it's hard to tell with almost all Teleconnections fairly neutral it takes just a little movement to create a lot of 'noise' and we could see the development of a Greenland high though it's looking fairly unlikely for now. That's three of the 7 nation army done now, onto the MJO... On the border of phase 5/6 and slowly moving towards being a fairly substantial phase 6 just slightly less amplified than it was in November so under amplified is probably a yes but it's still fairly amplified and we aren't really losing the signal and there's still a few ensembles showing the possibility of it keeping amplification towards phase 7 but the VP shows that we're probably finding the signal beyond phase 6 difficult to interpret and probably we're likely to see it lose amplification and slowly move into the so called COD. So we're probably relying on phase 6 over the next week or so (14-21 day lag probably) and a rebound of AAM (6 day lag initially but can be much longer) to time themselves together and we do get some form of mid to high latitude blocking. An entire pattern flip is probably unlikely as it's usually an amplified phase 7 that we would want for that but that doesn't mean we can't see some form of Scandi or Greenland blocking with a -VE AO by mid to late January. Obviously, the MJO amplification probably won't spike a significant amount of momentum to form that kind of blocking but if it can time itself well with a gain of East Asian mountain torque scattering thermal and zonal energy downstream and maybe allowing for some Eurasian (ish) blocking if it allows for an East Asian Jet Retraction. One of the main reasons why I wouldn't rule January out for cold (especially the second half) is just look at that scatter beyond phase 6 and it's clear that the models aren't handling the MJO well, maybe the ECM is doing better but the amount of spread means that you cannot really be sure off anything so long-term forecasting is likely to be either exactly correct or very far off or anywhere in-between there. Onto the firth and sixth ones and that's the Strat and Trop patterns... First thing to note is that Wave-2 does look fairly strong but dips towards the 10th as Wave-1 takes over, I think this is where the initial onset of a SSW would have to happen with strong baroclinic tilting and a large thermal gradient displacing the Strat vortex. The initial onset would then have to be followed by a weakening or dipping of Wave-1 amplitude as we see a second thermal wave forming probably around the North Atlantic area. This would be the best chance of a Polar-Night Jet Oscillation (PJO) type of SSW as that would put a cooling Strat vortex on either side of 'outer riding waves' and that thermal gradient cut push through the middle of the vortex and split it in two. I'm definitely not saying that's what's going to happen here but that is exactly how a PJO onset happens and a PJO is almost entirely linked with a major SSW. So if we can get Wave-1 displacement followed by Wave-2 split then that amount of upward wave flux would likely be enough for strong downwards reflection and a quick weakening of the Strat zonal wind downwards. At the moment that's still unlikely but there's a fair number of ensembles taking the Wave-2 amplitude and ramping it up right towards the end of the run. If that becomes the trend then we can become excited but for now I'd stay calm as that's quite a few hours away. The zonal winds continue to support the idea that a Wave-1 displacement would at least weaken the Strat vortex and that may translate itself into a slightly weaker (though maybe still zonal) Trop from mid-January onwards but only if we see some downward zonal wind reflection. It means that even if the MJO phase 7 isn't strongly amplified we might see at least a slight weakening of the Trop zonal pattern. So looking long-term is probably our best solution now with a slight increase in cold chances and hopefully a SSW happens with Wave-1 followed by Wave-2 but that'll only happen if we're lucky. We've got to hope that the Eurasian warming signal moving across the Pacific is followed by some sort of North Atlantic (ish) warming signal with increase Eddy's from the North America-Greenland area in the Troposphere and propagating vertically. In the Troposphere... Pretty much only the Atlantic is looking largely zonal with the East Asian Jet Retraction helping everyone except us. Still think that the Eurasian feedback across 90E might spread further West and we can get some energy into the Euro high amplifying it but how much is difficult to tell. If we're lucky it interacts with the more Westerly Eurasian Feedback. What looks more likely is the Eurasian Feedback staying too far East and any interaction will be un-interesting and it'll just push the Euro high up slightly. Possibility of a Scandi high remains there but what is most likely is a continuation of this pattern till mid January unless the Eurasian Feedback pushes much further West than is currently forecast. 6 of the 7 nation army done, 1 more to go and that's the QBO... QBO is still in the Westerly Phase but it seems to slowly be weakening and will likely turn to Easterly but that'll likely be after this Winter is over. Just good that the sleeper signal for the zonal wind is at least weakening and so may start having less of an effect as we slowly go over time. I'm not really focused that much on the QBO as I still don't fully understand how it works. So overall, the first half of January does favour a zonal pattern as people are saying but the increased tilting between the Trop and Strat layers (especially the upper Strat) could really help with the thermal transfer, in turn weakening the 10-1hpa zonal values fairly well. Wave-1 dominance looks to stay fairly stable so displacement rather than split would be the most likely way a SSW could happen if it does but a few ensembles are showing Wave-2 increasing as Wave-1 and hopefully that becomes a trend but I find it unlikely. What it could do is reflect some of the upward wave movements down and slow down the zonal winds in the Trop pattern so mid-late January we may see that form of downwards (non SSW related) connection between the Strat and the Trop. Away from the Strat pattern and the Trop pattern will mainly rely on the MJO phase 6 and 7 being more amplified than currently forecast and despite the rebounding +VE AAM, it's probably going to continue to be a forecasters nightmare as per long-term forecasting with multiple contrasting signals and a significant amount of spread on the Teleconnections. As long as it remains fairly neutral then rebounds in AAM from mountain torque events especially can help us in the longer term so it's not all dire in the Trop front but the MJO looks mainly uninteresting unless we get right at the top end of the amplification of the ensembles. Probably the best Strat pattern is the we see an initial Wave-1 onset causing the oscillation of the polar-night jet and an unstable thermal transfer from vertical Rossby waves and Eddy Heat Flux also increasing into the Strat before Wave-2 splits the displaced Strat vortex. It's unlikely at the moment but not impossible with a fair number of ensembles increasing the Wave-2 amplitude right towards the end of their runs and the 12Z GFS showing the possibility of how one would evolve if the Wave-2's strength did increase (do not take 1 run in isolation, I'm just using this as an example). This would significantly impact the stability and inertia of the polar-night jet and a Wave-1 followed by Wave-2 would likely cause a major SSW as long as it's caused by a fairly strong amount of upwards wave flux. One of the worse ways that the Strat pattern could evolve would for polar-night jet to continue to intensify and overpower the Eddy-driven subtropical jet and so the amount of thermal flux reaching the Strat would be fairly minimal. This situation wouldn't see a lot of pressure being put on the vortex and it wouldn't be sustained enough to cause that snap. It's a possibility but relies on the polar-night jet's downwelling to the Trop to be fairly continuous which just like the best possible scenario is fairly unlikely. The most likely scenario right now (in my opinion) is that we see increase Wave-1 strength with a slight increase in Wave-2 after the Wave-1 signal but not enough to cause a split and so at best we end up with a displaced Strat (but maybe not a SSW) and typically the cold is better positioned for North America in that scenario as the downwelling of any zonal changes happens. We do need to check up on how the Wave-2 pattern evolves though because if we do see it strengthen and we do end up seeing the best case scenario that is probably one of the better ways a SSW could set up for us and the large thermal flux and change over time would likely cause a major SSW. Like I say though, that remains unlikely for now. The Trop signal beyond the early part of January remains fairly mixed and so I wouldn't write cold off just yet. Without a SSW, I'd say that a zonal setup is slightly favoured right now but that's only because of the seasonal setups and general un-amplified evolving pattern right now and if we can see the AAM rise sharply again relatively soon then we can think about cold prospects away from a SSW for mid to late January so I certainly wouldn't write it off whatsoever.

Ironically, it's actually classed as a largely increased Strat jet that half led to this problem in the first place but it's the fact that it's evolving and connecting up with the subtropical jet in the Trop that's directed by Eddy's that means that the North Pole being in daily darkness right now increases the thermal gradient between the cooling Strat vortex due to the polar-night jet oscillation and the thermal Eddy's from the Trop, there's a larger thermal gradient than there normally would be. Which is good for abnormal heat transfer and hence it may help the onset of a SSW. Original post: https://community.netweather.tv/topic/98132-model-output-discussion-christmas-week-and-beyond/?do=findComment&comment=4778611

Agreed, the polar-night jet sort of helping here because it increases thermal gradient when there are Eddy's integrating into the Strat (polar-night jet oscillation) which could possibly further the baroclinic tilt by helping the misalignment of the thermal gradient. So despite being Wave-1 dominant we may get lucky though I'm not entirely sure of how my mind came to that conclusion it just sort of does it's own thing from piecing together what I remember from reading about the polar-night jet oscillation about a month ago. Original post: https://community.netweather.tv/topic/98132-model-output-discussion-christmas-week-and-beyond/?do=findComment&comment=4778598

Ironically, it's actually classed as a largely increased Strat jet that half led to this problem in the first place but it's the fact that it's evolving and connecting up with the subtropical jet in the Trop that's directed by Eddy's that means that the North Pole being in daily darkness right now increases the thermal gradient between the cooling Strat vortex due to the polar-night jet oscillation and the thermal Eddy's from the Trop, there's a larger thermal gradient than there normally would be. Which is good for abnormal heat transfer and hence it may help the onset of a SSW.

Agreed, the polar-night jet sort of helping here because it increases thermal gradient when there are Eddy's integrating into the Strat (polar-night jet oscillation) which could possibly further the baroclinic tilt by helping the misalignment of the thermal gradient. So despite being Wave-1 dominant we may get lucky though I'm not entirely sure of how my mind came to that conclusion it just sort of does it's own thing from piecing together what I remember from reading about the polar-night jet oscillation about a month ago.

I'm loving(or rather hating) all the anger in here, it's funny how ridiculous we get over weather meanwhile I'm just enjoying my day and am definitely not writing off the next 4 weeks. A reminder that we were in a zonal pattern in early-mid November(if memory serves me correctly) not that long before we saw that cold. I know it was different circumstances but we haven't even entered January yet and we're writing it off?