Eagle Eye

Atmospheric river coming late December/early January by the looks of it as that AR should transition east. May delay new year's potential.

The IOD dipole has been switching up recently with a collapsing of the +VE IOD pattern (look around the 90E area) subsurface with subsurface development of +VE anomalous sea temps in the area west of Thailand that is beginning to form. It should eventually work its way to the surface and the pattern slowly flips into a classic - VE IOD. With cold pushing its way eastwards. For now we stay strongly positive however, this is already having effects... The upwards pushing of - VE anomalous temps currently subsurface in the western Pacific with the surface El Nino is likely being driven by the evolving IOD change. So the slow change to a - VE IOD could well force the development of La Nina by maybe roughly Spring next year. A potentially bad thing looking at next Winter. Just wanted to quickly update on that. With a dipping IOD, easterly winds are forced over the WPAC being traded east from the Indian Ocean. Forcing a downwelling Rossby wave and an upwelling Kelvin wave pushing warm anaomlies into the eastern Pacific. These waves constructively interact with waves of opposing sign over the central Pacific due to the collapse of easterly winds in the area upon Winter. Forcing westerly wind developments into the central Pacific cooling the surface, which diffuses further down into the water where there's a higher gradient I suspect leading to a stronger cold pool developing and that eventually reflects back up. So we should see the ENSO effects slowly backing down towards the end of this Winter. Depending on how far the QBO has travelled in the final phase of the EQBO and whether or not we've had a SSW, this could have some previously unseen impacts upon the latter part of Winter with El Nino potentially losing its strength slowly. Interested to hear others thoughts on what this could mean. Current forecasts to look at the potentially speed of this and I think that is not a clear cut evolution and there's some mixing in the central Pacific in the future (180) between the easterly and westerly winds meaning a slight delay of the changeover is possible for now. Also interested about the sudden switch to westerly on the forecast for the first week of January around the IOD area. The near surface zonal winds of the IOD negative phase are westerly so potentially this is the forecast seeing a switchover properly beginning into January time.

Background signals not supporting this does suggest a SSW influence already showing up long term, a good sign if it's a sort of majority forecast. However, doesn't necessarily link with a SSW, the EC46 may be seeing something else but I don't know what else. Another good sign for now.

No long explanation just a bit of festive chart in the Stratosphere been showing last few days continuing. That setup isn't a reversal yet, it's complicated but it's another run going in a good direction.

Yesterday's sunset

Only a couple days till Christmas now, somehow. I'm not entirely sure how this has crept up on me so well. Meanwhile, the wave response towards the upper part of the Trop to the mid Trop Rossby wave around day 10/11 is very quick and I suspect it's where our split potential comes from. This kind of quickly pole ward forced wave is like a jack in the box with how much trapped energy it has for it to significantly push upwards and also vertically like that. If we do get something similar then I think we can really start looking at the Stratosphere. It's keeping an eye on how this evolves.

Whilst it is in a far distant time frame, we're currently seeing the start of a split potential to arise not just from a best guess based off the factors as they have been for a few weeks now but the model runs. They're not quite at split strength and haven't reversed it yet. However, this is the most significant run we've seen yet. With the development of the +VE heights of Greenland and the Siberian heights sliding into Kamchatka really tightening into the vortex. Also, that displacement if it were just that would be potentially good for us. The vortex stays quite strong after the mid run re-strengthening but it starts to lose its shape and the last frame I've attached of the anomalies really show how tight it gets stretched on the run. This has quickly changed into a weak Wave-2 event and mainly Wave-1 initiated, with a Wave-2 developing right towards the end from the Siberian eddies. The refraction caused by the large temperature gradient diffuses the temperature towards the north Pole.  The diffused temperature goes stronger towards the poles with a higher temperature gradient. Essentially forcing a stronger zonal wind pre-SSW. This forms a polar-night jet and a stronger Rossby wave in the Strat. The bigger the temperature gradient, the stronger the zonal winds and the more Waves, the better. That is the exact reason it's better. It causes a stronger Rossby wave and so to reach thermal equilibrium, the atmosphere tries to balance itself out. So the warm air pushes towards the cold air replacing it and typically displacing it typically if its a Wave-1 leading to a large decrease in zonal winds and sometimes but not always a reversal. Sometimes it can force a splitting but I don't feel like this is one of those times yet . So it's good that we get the Wave-2 development. With Wave-2, the temperature gradient is strong enough on both sides that if the warm air rushing into the Arctic on both sides, they can connect up and quite often lead to a major reversal. However, at silly run time still, it's ages away.  As the Rossby wave develops, it's an easterly wave that decelerates the vortex and that and the temperature movement act to completely reverse the polar vortex. So, I'd argue that we need the polar-night jet to form to really force a split here and it gives the time for the Siberian-north Pacific wave to properly form and stops a really messy and complex evolution to occur. The variability in the polar vortex to react opposingly to initial changes if they occur quickly is what forces a SSW. This is a different evolution to the polar-night jet forming over the space of a month as this is it being forced to strengthen.  What I mean by that is that the atmosphere kind of doesn't want to form the polar-night jet and it's reactionary. So to balance it out, it changes the temperature around to form a dynamic equilibrium. As my Geography teacher would put it (obviously not talking about the polar-night jet, something else), "it's over-compensating" and the atmosphere and the earth does that a lot. Just a natural reaction of physics. So, the imperfect world can benefit us, sort of the same reason we get thunderstorms as well.  The day-night temperature gradient (polar-night jet) is what forces the zonal jet formation during Winter along with the mid-latitude to Arctic difference. However, the unnatural oscillating jet disturbed by Rossby waves completely switches up. The amplification of temperature anomalies and movement talked about before forcing the reversal and downwards forcing of the reversal through wave breaking, which completely switches up the surface pattern pretty much. I would argue that the quicker it takes, the more it switches it up due to the less movement of the pattern which is essentially a reversed tropospheric Rossby wave pattern from rotation occurs. So a quicker amplification of Rossby waves, the better for us, especially this Winter.  The recovery is not necessarily as quick as you would think it would be if the MJO quickly re-transfers back. The radiative heating transfer can take months to properly recover, quicker at the surface though, in the Stratosphere and that implies a less zonal potential from downwelling the rest of the Winter. So, the earlier the better. The lower Stratosphere takes the longest to recover and so we kind of lose the connection assuming a major SSW were to happen.  If a PJO were to occur, it's our best scenario for this Winter. Now, in my opinion, we are at a potentially god scenario. They are typical with long-periods of wave activity going into the Stratosphere. Essentially, what we've been having since November ish with pulsed wave activity though not as strong as it has been in times before. I also suspect that's why 2018 was such an impactful SSW, as it was a PJO scenario.  The anticyclonic wave developing over the north Pacific connecting up with the main vortex is a very good sign in my opinion and the +VE wave driving just to the south over Greenland to Europe could also be good in the future. This temperature gradient will be really good signs for a split if the southern wave could become an anticyclonic wave connecting up with the main vortex. The clear polar-night jet formation is another good sign. However, right at the end of the run, it’s still not a particularly high possibility. However, assuming an eddy forced trop-jet connecting up with the Strat polar-night jet then we will have a good situation.  The significant polar-night jet occurring on one of these runs is in my mind that we're at least in with a chance of a major SSW and given how the ground is evolving, this is our best chance for a while. Looking at the specific setup into the future. The current runs have that meridional jet fired up by the eddy flux pushing towards the higher latitudes in the Arctic. This is a stronger flux into the mid-upper Strat (not quite at the Stratopause level yet and sometimes, top down is a more viable option but we'll have to wait and wait for this one. Often I find that SSW's are delayed and we aren't by any means guaranteed a SSW. I will often assume we are in this post just because I'm trying to analyse the setup deeper into the future. This is a cautious attempt to look at the best case setup. The different levels of reversals at the equator and showing up mid-latitude in the mid-upper Stratosphere are more than what happened last time. The setup with the polar-night jet and strong deep-rooted flux + mid-upper meridional anticyclonic wave that I've been talking about is good for Rossby wave refraction. Again, it's still way way into the future. We've seen this before on the models. This can easily be undone and messed up and I talked about that possibility earlier. If the polar-night jet doesn't get rooted out by a strong enough thermal gradient (e.g. we don't see a strong +VE anticyclonic wave or the polar-night jet is being overblown on the models or both then we end up in kind of a bad situation. However, if you don't play the game you can't win) then we get a Stratospheric downwelling of westerly winds and forcing a large +VE NAM response. I suspect that'll leave the convective forcing at a low for a while. That's an unfortunate possibility of what happens. The suppressed and active convective phase is dominated by zonal wind deviations. The tropical forcing from the GWO becomes an extension of the +VE TNH phase (/turning into a +VE TNH pattern) being stuck in a low AAM phasing situation and the evolution of the atmosphere becomes increasingly barotropic from the top down and the vortex spins up again. This feels like it could become a +VE EPO situation and the expansion of the Hadley cell would be pretty much entirely expected in this situation. The thermal gradient if it becomes big enough to replace the energy in the Arctic, it will become increasingly baroclinic and that forces, the anomalous polar-jet displacement and the reactionary atmospheric wave response which flips the reversal and positives on the graph. This would likely result in the AAM response to be increasing the AMB through rising frictional torque I would suspect. This is as with a net easterly wind, the rotary force on the earth slows down, transferring angular momentum out of the earth and into the atmosphere. The frictional torque response will lead to the synoptic SLP pattern having to balance out the atmosphere by decreasing mountain torque and retracting the north Pacific jet. Now depending on the exact scenario, the separation of two jets and the increase of tropical forcing into a rising Rossby wave over the Atlantic is the generic scenario that'll likely be slightly altered closer to time if a major SSW were to happen. Wave-2 is clearly on the rise right towards the end of the run compared to Wave-2 which is another good sign assuming it keeps rising. Then with the shrunken vortex, a split would be very likely. So, taking the 12Z at face value and it's very good. With the strong Wave-1 lasting right up till the Siberian wave properly develops with the Uralian omega block rapidly expanding in the Troposphere. We saw a similar evolution with the one earlier this year, however, we didn't have such a good Greenland-Svalbard signal. If that forms a dipole then we've technically got a tripole but that's just a bit of fun my mind had as that's a typical dipole that sets up. Again though, good signs are good signs on the models and we've been moving towards them for a while. Looking at the Wave-2 strength towards the end of the run as it's being transferred into the Strat and it really does look like a pretty perfect planetary wave setup. The energy transferred from the Rossby waves into the Strat is a clear opposite of the tropopause so a slightly deeper rooted trough than I initially thought a few days ago, which may mean a higher reach for the eddy flux but it's not a particularly big matter, I just noticed it. The Strat centre of the waves are very interesting as well. A south Greenland centre is a pretty good setup and I'm pretty sure I've seen this pop up on a few case studies I've seen before. Then a slightly displaced Uralian wave with a wider Rossby wave meaning that it's more over the Kamchatka area but nonetheless, it's the best I've seen in years. However, at this range it is still a wait and see. Not everything with a SSW is black and white, there aren't exact setups just guidelines. If a split occurs, most of the time it should favour us, as we're at a higher latitude than we tend to think. Also, a split here, in this evolution, with a few days of planetary wave rotation, is more having the strong zonal winds retraction towards north America and Russia. So it's a fairly good sign of the forecast being favourable towards a systematic reversal and a typical major SSW evolution if things went right enough. I couldn't tell you if the numbers and temperature gradients are enough to force a reversal here and I don't want to because it's one run and even though, I've written a lot here, it's mostly just been about the possibilities I see occurring. At this range the range of possibilities is rather large and so this specific run focusing on a fairly split focused set of circumstances is neither good or bad or maybe both. Who knows? Oddly good thing about weather forecasting, you can still make your own conclusions once you're beyond about 30 seconds ha ha. The baroclinic tilting with height of the vortex and it shrinking (apart from the top of the Strat) is a good sign but just that for now. The tilting isn't particularly strong away from the tropopause here but it's been shifted away from the initial vortex. Right at the end of the run, we see the meridional temp increasing quite strongly & the temperature gradient pre-that could well be a driving force force for Rossby wave refraction towards the polar vortex. That - VE noodle pushing down really helps force a potential split. The EQBO setup is a fairly typical one with a late stage EQBO, westerly trying to form in the far upper Strat. The downwelling properly could still take a few months, however, right now it's now in the crucial part of the late stage phase. Where we've got weak WQBO at the surface with a slowly downforcing -VE winds and colder forcing into the mid Strat. If this aligns well enough in January with +VE temps and easterlies mixing with the potential SSW, then we've got a near perfect scenario in my mind. Looking down at the surface and despite the -VE TNH, the extension of the Pacific jet appears to reach the Atlantic and force the building of a ridge and until the +VE NAM changes, which to be fair it is forecasted to sort of do, then we're still in a bad situation. The +VE EAMT hasn't faired well for us with the extension of the Pacific jet coupling with the Atlantic jet and the pattern flip in north America essentially being meaningless. The frictional torque response should occur late December and that might change the pattern setup, with the -VE frictional torque acting to balance the zonal winds into January and replace the +VE north Pacific basic non-wave setup w/a clear Rossby wave setup an a flip to -VE near the north Pacific leading to more backing of the Alaskan ridge. If this reaction occurs well enough, then that's part 1 of our SSW journey done with, pretty much a renewed pulse of our Greenland wave (it would be alternated to over Greenland) and if our Ural wave can materialise as well, that's 1/2 of the job done. The fact that it's on the ensembles is a good sign though. Another potentially good sign is the slightly blocking on the ensembles an this makes some sense given the eastern north American wave is allowed to exit and the north Atlantic ridge becomes flipped and we go into a neutral of -VE NAM scenario. We'll see though. The MJO is currently wandering really in the middle of nowhere, or rather were we don't really want it. Most of the convective envelope stalled over Africa for quite a while on the forecasts. A good thing potentially if a SSW were to happen, as it could force the MJO to push quickly towards a strong 5-7 phasing. Without it, we're kind of lost for January without any torque breaks. I want snow on my birthday as I'm being a bit selfish but hopefully the setup favours me ha ha. That's enough for now, I'm tired. Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4982285

Whilst it is in a far distant time frame, we're currently seeing the start of a split potential to arise not just from a best guess based off the factors as they have been for a few weeks now but the model runs. They're not quite at split strength and haven't reversed it yet. However, this is the most significant run we've seen yet. With the development of the +VE heights of Greenland and the Siberian heights sliding into Kamchatka really tightening into the vortex. Also, that displacement if it were just that would be potentially good for us. The vortex stays quite strong after the mid run re-strengthening but it starts to lose its shape and the last frame I've attached of the anomalies really show how tight it gets stretched on the run. This has quickly changed into a weak Wave-2 event and mainly Wave-1 initiated, with a Wave-2 developing right towards the end from the Siberian eddies. The refraction caused by the large temperature gradient diffuses the temperature towards the north Pole.  The diffused temperature goes stronger towards the poles with a higher temperature gradient. Essentially forcing a stronger zonal wind pre-SSW. This forms a polar-night jet and a stronger Rossby wave in the Strat. The bigger the temperature gradient, the stronger the zonal winds and the more Waves, the better. That is the exact reason it's better. It causes a stronger Rossby wave and so to reach thermal equilibrium, the atmosphere tries to balance itself out. So the warm air pushes towards the cold air replacing it and typically displacing it typically if its a Wave-1 leading to a large decrease in zonal winds and sometimes but not always a reversal. Sometimes it can force a splitting but I don't feel like this is one of those times yet . So it's good that we get the Wave-2 development. With Wave-2, the temperature gradient is strong enough on both sides that if the warm air rushing into the Arctic on both sides, they can connect up and quite often lead to a major reversal. However, at silly run time still, it's ages away.  As the Rossby wave develops, it's an easterly wave that decelerates the vortex and that and the temperature movement act to completely reverse the polar vortex. So, I'd argue that we need the polar-night jet to form to really force a split here and it gives the time for the Siberian-north Pacific wave to properly form and stops a really messy and complex evolution to occur. The variability in the polar vortex to react opposingly to initial changes if they occur quickly is what forces a SSW. This is a different evolution to the polar-night jet forming over the space of a month as this is it being forced to strengthen.  What I mean by that is that the atmosphere kind of doesn't want to form the polar-night jet and it's reactionary. So to balance it out, it changes the temperature around to form a dynamic equilibrium. As my Geography teacher would put it (obviously not talking about the polar-night jet, something else), "it's over-compensating" and the atmosphere and the earth does that a lot. Just a natural reaction of physics. So, the imperfect world can benefit us, sort of the same reason we get thunderstorms as well.  The day-night temperature gradient (polar-night jet) is what forces the zonal jet formation during Winter along with the mid-latitude to Arctic difference. However, the unnatural oscillating jet disturbed by Rossby waves completely switches up. The amplification of temperature anomalies and movement talked about before forcing the reversal and downwards forcing of the reversal through wave breaking, which completely switches up the surface pattern pretty much. I would argue that the quicker it takes, the more it switches it up due to the less movement of the pattern which is essentially a reversed tropospheric Rossby wave pattern from rotation occurs. So a quicker amplification of Rossby waves, the better for us, especially this Winter.  The recovery is not necessarily as quick as you would think it would be if the MJO quickly re-transfers back. The radiative heating transfer can take months to properly recover, quicker at the surface though, in the Stratosphere and that implies a less zonal potential from downwelling the rest of the Winter. So, the earlier the better. The lower Stratosphere takes the longest to recover and so we kind of lose the connection assuming a major SSW were to happen.  If a PJO were to occur, it's our best scenario for this Winter. Now, in my opinion, we are at a potentially god scenario. They are typical with long-periods of wave activity going into the Stratosphere. Essentially, what we've been having since November ish with pulsed wave activity though not as strong as it has been in times before. I also suspect that's why 2018 was such an impactful SSW, as it was a PJO scenario.  The anticyclonic wave developing over the north Pacific connecting up with the main vortex is a very good sign in my opinion and the +VE wave driving just to the south over Greenland to Europe could also be good in the future. This temperature gradient will be really good signs for a split if the southern wave could become an anticyclonic wave connecting up with the main vortex. The clear polar-night jet formation is another good sign. However, right at the end of the run, it’s still not a particularly high possibility. However, assuming an eddy forced trop-jet connecting up with the Strat polar-night jet then we will have a good situation.  The significant polar-night jet occurring on one of these runs is in my mind that we're at least in with a chance of a major SSW and given how the ground is evolving, this is our best chance for a while. Looking at the specific setup into the future. The current runs have that meridional jet fired up by the eddy flux pushing towards the higher latitudes in the Arctic. This is a stronger flux into the mid-upper Strat (not quite at the Stratopause level yet and sometimes, top down is a more viable option but we'll have to wait and wait for this one. Often I find that SSW's are delayed and we aren't by any means guaranteed a SSW. I will often assume we are in this post just because I'm trying to analyse the setup deeper into the future. This is a cautious attempt to look at the best case setup. The different levels of reversals at the equator and showing up mid-latitude in the mid-upper Stratosphere are more than what happened last time. The setup with the polar-night jet and strong deep-rooted flux + mid-upper meridional anticyclonic wave that I've been talking about is good for Rossby wave refraction. Again, it's still way way into the future. We've seen this before on the models. This can easily be undone and messed up and I talked about that possibility earlier. If the polar-night jet doesn't get rooted out by a strong enough thermal gradient (e.g. we don't see a strong +VE anticyclonic wave or the polar-night jet is being overblown on the models or both then we end up in kind of a bad situation. However, if you don't play the game you can't win) then we get a Stratospheric downwelling of westerly winds and forcing a large +VE NAM response. I suspect that'll leave the convective forcing at a low for a while. That's an unfortunate possibility of what happens. The suppressed and active convective phase is dominated by zonal wind deviations. The tropical forcing from the GWO becomes an extension of the +VE TNH phase (/turning into a +VE TNH pattern) being stuck in a low AAM phasing situation and the evolution of the atmosphere becomes increasingly barotropic from the top down and the vortex spins up again. This feels like it could become a +VE EPO situation and the expansion of the Hadley cell would be pretty much entirely expected in this situation. The thermal gradient if it becomes big enough to replace the energy in the Arctic, it will become increasingly baroclinic and that forces, the anomalous polar-jet displacement and the reactionary atmospheric wave response which flips the reversal and positives on the graph. This would likely result in the AAM response to be increasing the AMB through rising frictional torque I would suspect. This is as with a net easterly wind, the rotary force on the earth slows down, transferring angular momentum out of the earth and into the atmosphere. The frictional torque response will lead to the synoptic SLP pattern having to balance out the atmosphere by decreasing mountain torque and retracting the north Pacific jet. Now depending on the exact scenario, the separation of two jets and the increase of tropical forcing into a rising Rossby wave over the Atlantic is the generic scenario that'll likely be slightly altered closer to time if a major SSW were to happen. Wave-2 is clearly on the rise right towards the end of the run compared to Wave-2 which is another good sign assuming it keeps rising. Then with the shrunken vortex, a split would be very likely. So, taking the 12Z at face value and it's very good. With the strong Wave-1 lasting right up till the Siberian wave properly develops with the Uralian omega block rapidly expanding in the Troposphere. We saw a similar evolution with the one earlier this year, however, we didn't have such a good Greenland-Svalbard signal. If that forms a dipole then we've technically got a tripole but that's just a bit of fun my mind had as that's a typical dipole that sets up. Again though, good signs are good signs on the models and we've been moving towards them for a while. Looking at the Wave-2 strength towards the end of the run as it's being transferred into the Strat and it really does look like a pretty perfect planetary wave setup. The energy transferred from the Rossby waves into the Strat is a clear opposite of the tropopause so a slightly deeper rooted trough than I initially thought a few days ago, which may mean a higher reach for the eddy flux but it's not a particularly big matter, I just noticed it. The Strat centre of the waves are very interesting as well. A south Greenland centre is a pretty good setup and I'm pretty sure I've seen this pop up on a few case studies I've seen before. Then a slightly displaced Uralian wave with a wider Rossby wave meaning that it's more over the Kamchatka area but nonetheless, it's the best I've seen in years. However, at this range it is still a wait and see. Not everything with a SSW is black and white, there aren't exact setups just guidelines. If a split occurs, most of the time it should favour us, as we're at a higher latitude than we tend to think. Also, a split here, in this evolution, with a few days of planetary wave rotation, is more having the strong zonal winds retraction towards north America and Russia. So it's a fairly good sign of the forecast being favourable towards a systematic reversal and a typical major SSW evolution if things went right enough. I couldn't tell you if the numbers and temperature gradients are enough to force a reversal here and I don't want to because it's one run and even though, I've written a lot here, it's mostly just been about the possibilities I see occurring. At this range the range of possibilities is rather large and so this specific run focusing on a fairly split focused set of circumstances is neither good or bad or maybe both. Who knows? Oddly good thing about weather forecasting, you can still make your own conclusions once you're beyond about 30 seconds ha ha. The baroclinic tilting with height of the vortex and it shrinking (apart from the top of the Strat) is a good sign but just that for now. The tilting isn't particularly strong away from the tropopause here but it's been shifted away from the initial vortex. Right at the end of the run, we see the meridional temp increasing quite strongly & the temperature gradient pre-that could well be a driving force force for Rossby wave refraction towards the polar vortex. That - VE noodle pushing down really helps force a potential split. The EQBO setup is a fairly typical one with a late stage EQBO, westerly trying to form in the far upper Strat. The downwelling properly could still take a few months, however, right now it's now in the crucial part of the late stage phase. Where we've got weak WQBO at the surface with a slowly downforcing -VE winds and colder forcing into the mid Strat. If this aligns well enough in January with +VE temps and easterlies mixing with the potential SSW, then we've got a near perfect scenario in my mind. Looking down at the surface and despite the -VE TNH, the extension of the Pacific jet appears to reach the Atlantic and force the building of a ridge and until the +VE NAM changes, which to be fair it is forecasted to sort of do, then we're still in a bad situation. The +VE EAMT hasn't faired well for us with the extension of the Pacific jet coupling with the Atlantic jet and the pattern flip in north America essentially being meaningless. The frictional torque response should occur late December and that might change the pattern setup, with the -VE frictional torque acting to balance the zonal winds into January and replace the +VE north Pacific basic non-wave setup w/a clear Rossby wave setup an a flip to -VE near the north Pacific leading to more backing of the Alaskan ridge. If this reaction occurs well enough, then that's part 1 of our SSW journey done with, pretty much a renewed pulse of our Greenland wave (it would be alternated to over Greenland) and if our Ural wave can materialise as well, that's 1/2 of the job done. The fact that it's on the ensembles is a good sign though. Another potentially good sign is the slightly blocking on the ensembles an this makes some sense given the eastern north American wave is allowed to exit and the north Atlantic ridge becomes flipped and we go into a neutral of -VE NAM scenario. We'll see though. The MJO is currently wandering really in the middle of nowhere, or rather were we don't really want it. Most of the convective envelope stalled over Africa for quite a while on the forecasts. A good thing potentially if a SSW were to happen, as it could force the MJO to push quickly towards a strong 5-7 phasing. Without it, we're kind of lost for January without any torque breaks. I want snow on my birthday as I'm being a bit selfish but hopefully the setup favours me ha ha. That's enough for now, I'm tired.

With the wave propagation wandering in the middle of nowhere and the dampening signal going towards January, the tropical forcing signal towards the Maritime really gets pushed down and weakened. So we essentially lose most of the forcing by early to mid-January. However, this is almost perfect for a SSW not to mess w/tropical forcing. However, convective forecasting even whilst using wave propagation can often become mixed out or overdone after the first week or so of the forecast. So we'll see. This is all just assuming a SSW happens earl January which is only about a 30% chance right now. Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4981566

With the wave propagation wandering in the middle of nowhere and the dampening signal going towards January, the tropical forcing signal towards the Maritime really gets pushed down and weakened. So we essentially lose most of the forcing by early to mid-January. However, this is almost perfect for a SSW not to mess w/tropical forcing. However, convective forecasting even whilst using wave propagation can often become mixed out or overdone after the first week or so of the forecast. So we'll see. This is all just assuming a SSW happens earl January which is only about a 30% chance right now.

Yeah a Nacreous is the same thing as you said .

Some nice nacreous clouds at sunset.

ECM SSW potential support has gone up very quickly for an early January SSW, which the troposphere has supported for quite a while. Not guaranteed by any means but still a very good switch up in the forecasts that validates what I've been saying recently. Wave-2 amplitude has a sudden tropopausal based increase driven by the right tropospheric setup to allow for a significant wave driving along the tropopause area that quickly, where we have a large temperature gradient driven by quickly switching EHF parcel's with height. In the troposphere itself we have the Greenland Rossby wave switch and the warmth transferring lagging behind the driven Rossby wave. The dipole with a mid-tropospheric based trough forcing the switch to warm transfer at the top of the trough (is it a convergence-divergence thing?) and the low rooted trough means that the transfer to warmth manages to react strongly to the typical perpendicular reaction to a trough, except it's usually cold air when it meets the tropopause rather than warm air. So there's a different reaction than typical and a large Rossby wave backs westwards up into the Stratosphere. There's a more basic setup over Siberia which follows the normal ridge meeting tropopause and eastwards upwards slip transfer of eddies transferring warmth. This all leads to a sudden quick movement to a Wave-2 force onto the Stratosphere. There's a lot of close to or at a large aspect ration of baroclinicity in the vortex on the forecasts. A couple splits as well but still distance and not really at the time of the SSW potential just yet.

With the jet retraction in the lagged rough 2 week (Rossby wave transversing the planet) response to the jet extension and the pattern flip. We'll likely see a flip to nuetral/negative PNA in the first week or 2 of January. This could well work in our favour. As long as we don't see a full recovery initially, we may well see the initial reaction to be dampened and so trough response is to push everything up (well, pivot most up) in north America and that could see a +VE heights response pushed from Canada towards Greenland. The composite also suggests the development of a mid-Atlantic ridge connecting up with the Greenland signal. Depending on timing, this could be the final push for the Stratosphere (earlier reaction) and/or could set up a blocking pattern for cold potential here. However, it is a setup very close to the ridge becoming a zonal setup with the Hadley cell expansion into Europe and Greenland heights Retrogression leaves us in a bad position with Euro heights and a very zonal setup. So if the Greenland +VE heights do happen, they probably won't have much time to work and so we'd much rather prefer for a Stratospheric response in my opinion but we'll see what happens. The switch to - VE PNA isn't guaranteed and it's just a composite setup. Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4980535

With the jet retraction in the lagged rough 2 week (Rossby wave transversing the planet) response to the jet extension and the pattern flip. We'll likely see a flip to nuetral/negative PNA in the first week or 2 of January. This could well work in our favour. As long as we don't see a full recovery initially, we may well see the initial reaction to be dampened and so trough response is to push everything up (well, pivot most up) in north America and that could see a +VE heights response pushed from Canada towards Greenland. The composite also suggests the development of a mid-Atlantic ridge connecting up with the Greenland signal. Depending on timing, this could be the final push for the Stratosphere (earlier reaction) and/or could set up a blocking pattern for cold potential here. However, it is a setup very close to the ridge becoming a zonal setup with the Hadley cell expansion into Europe and Greenland heights Retrogression leaves us in a bad position with Euro heights and a very zonal setup. So if the Greenland +VE heights do happen, they probably won't have much time to work and so we'd much rather prefer for a Stratospheric response in my opinion but we'll see what happens. The switch to - VE PNA isn't guaranteed and it's just a composite setup.

The +VE EAMT extension of the - VE TNH and allow the Rossby wave forcing to be unimpeded by a weak zonal flow despite a bad looking Greenland. Not a perfect or particularly great setup nor bad, it's a very middling and wait for each model run kinda setup.

Quick look at typical eddy heat flux dynamics. Red arrows is the +VE EHF (essentially warm transfer) and blue (essentially cold transfer) are - VE. I've numbered them in terms of order of transfer to make it easier. With height, troughs tend to tilt more westwards with height, whereas it's eastwards for ridges of warm air. As that moves on, around mid Stratosphere is where the switch over happens and the transfer of flux essentially switches. I'm not sure way, perhaps something to do with refraction reaching a certain point. Looking at the setup by around day 7/8 in the tropopause with the EHF. Arrows pointing down are the furthest the ridge reaches with height and up arrows are the centre of the troughs with height. Imagine this pushing past that refraction point. You've got a Rossby Wave pushing into Northern Canada and northern Greenland and may extend into Svalbard beyond the current forecasts if it can properly displace the vortex. With Alaska being cooled down. If it can get enough to the Aleurian area, then one to watch. However, for now this is setting up in early January the vortex for something maybe late January. Also, very good to note the Siberian one, that's a better setup for displacement I've just realised but you want the Aleurian - VE heights and Greenland +VE heights for the start to a split. I don't expect it to be enough for a split yet without another of the same north American setup pretty much straight after.

Bit of stuff from today.

The +VE EAMT causing a rise in AAM and potentially helping on the ground , is also helping the Stratosphere. The extension looks to push - VE heights across the south of the USA and hold the - TNH pattern and weakens zonal possibilities. That also means that it's allowing multiple rounds of +VE heights to be pushed into the NE part of north America. That's a good sign for the Rossby wave to push into the stratosphere and at least displace the vortex. In Asia, the +VE Uralian ish heights development pushing north westwards after a pivot. Looking quite good for ground level developments as well. One for others to keep an eye on. This should contribute to a Wave-2 development in the stratosphere and as it comes closer on the forecasts, so does the likelihood of a reversal. Very Strat driving looking Trop here. Slight reversal on the forecasts already.

Yep, I used to do thst for some reason but I decided that last year for 3 months, I'd research in-depth a lot and now I try and write paragraphs explaining my thoughts where I don't let my biases overtake by using "could" for example. This just means that I realise that sometimes I may be assuming a lot about what happens if this certain chart is right. I'll try and give examples of each situation that could play out to show the full picture.

I've explained everything at least 20 times before so quite frankly I can't be bothered to do it again.

Ha ha, I use way too many abbreviations but I would never not explain them to someone if they were struggling.

Goooooood morning.

It appears that the +EPO wave shrinks away quite quickly with the development of a - TNH via the vertical driving of the +VE height. The jet extension happens around this time but should be displaced south enough to drive the - TNH pattern and also form the +EPO again (talked about a bit later) but more favourably and a slightly less zonal than typical +EPO. The - TNH pattern looks to force the Greenlaand - VE heights to shift poleward and disconnect the north Atlantic jet and allow for tropical forcing to have more of an impact with a slight increase around the same time. Potentially leading to a cold pattern but I'll leave that to model to model runs. Then a +VE EPO redevelops but a veriation of it forms. With the shallow heights centred over Alaska, then if the north American signal can stay +VE, then a jet retraction in response the the jet extension (w/about a 14 day lag, assuming no other +VE EAMT event) would collapse the high over the just south of Aleurian region and the Alaska height could well be driven southwards by being tilted on the opposite side of a Rossby wave ridge if one could form over Siberia. Then that's a great stratosphere setup for a SSW, I'll get onto that later quite a lot is on the +VE heights over the NE part of north America at least staying fairly strong (assuming the height do form which they should, just not sure how strong it'll stay) and hold out the - VE heights. Hypothetically, if it did, it'd drive the Quebec heights further north but more importantly would disperse the wave vertically, diffusing the heat up into the stratosphere with a 3 way Rossby-wave setup for a 2-Wave attack (Siberia and Quebec-Greenland) on the stratosphere with the vortex displaced over to the north Pacific. The Mon-development of the mid stratosphere jet looks to be partly due to the downwelling from the development of the EQBO. The 1hPa being +VE isn't necessarily something to be worried about as it acts rather erratically compared to the mid Stratosphere. It's quite easily affected by eddies compared to below it and therefore switches up more than other heights. As we aline with the 2021 EQBO, it'll be interesting to see the difference with the El Nino episode and if we can get a prolonged - TNH period, whether that can work with the EQBO to form a potentially good partnership. Still that eddy driven jet helping connect up with the Stratosphere but nothing particularly out of the ordinary yet. It's sitting around waiting time with the stratosphere but as I've said before, a good setup. Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4974508

It appears that the +EPO wave shrinks away quite quickly with the development of a - TNH via the vertical driving of the +VE height. The jet extension happens around this time but should be displaced south enough to drive the - TNH pattern and also form the +EPO again (talked about a bit later) but more favourably and a slightly less zonal than typical +EPO. The - TNH pattern looks to force the Greenlaand - VE heights to shift poleward and disconnect the north Atlantic jet and allow for tropical forcing to have more of an impact with a slight increase around the same time. Potentially leading to a cold pattern but I'll leave that to model to model runs. Then a +VE EPO redevelops but a veriation of it forms. With the shallow heights centred over Alaska, then if the north American signal can stay +VE, then a jet retraction in response the the jet extension (w/about a 14 day lag, assuming no other +VE EAMT event) would collapse the high over the just south of Aleurian region and the Alaska height could well be driven southwards by being tilted on the opposite side of a Rossby wave ridge if one could form over Siberia. Then that's a great stratosphere setup for a SSW, I'll get onto that later quite a lot is on the +VE heights over the NE part of north America at least staying fairly strong (assuming the height do form which they should, just not sure how strong it'll stay) and hold out the - VE heights. Hypothetically, if it did, it'd drive the Quebec heights further north but more importantly would disperse the wave vertically, diffusing the heat up into the stratosphere with a 3 way Rossby-wave setup for a 2-Wave attack (Siberia and Quebec-Greenland) on the stratosphere with the vortex displaced over to the north Pacific. The Mon-development of the mid stratosphere jet looks to be partly due to the downwelling from the development of the EQBO. The 1hPa being +VE isn't necessarily something to be worried about as it acts rather erratically compared to the mid Stratosphere. It's quite easily affected by eddies compared to below it and therefore switches up more than other heights. As we aline with the 2021 EQBO, it'll be interesting to see the difference with the El Nino episode and if we can get a prolonged - TNH period, whether that can work with the EQBO to form a potentially good partnership. Still that eddy driven jet helping connect up with the Stratosphere but nothing particularly out of the ordinary yet. It's sitting around waiting time with the stratosphere but as I've said before, a good setup.