Recretos

I remember saying that I will post some animations when things get interesting. Well, now I present 2 3D animations from the latest 12z GFS. Both present 3 layers. 10mb, 30mb and 100mb. The animation goes from 204h to 384h on a 12h interval. The main goal will be to spot the interaction on different levels and possible propagations. In this case I only have one parameter. Both the topography and the colour present geopotential height. I will do topography+temp animations when/if the whole "SSW" process intensifies in the coming days. First is a side view animation. To explain the perspective: It is like looking from Europe (man that sounds weird ). It is like looking Netweather.tv or meteociel stratosphere maps in 3D. The interesting thing about it, is the fact that the early shift of "power" from left to right (from Siberia to Canada) is pretty much instant in all layers throughout the strat. while the later height rises are mostly evident on 10mb level and slightly on 30mb, while 100mb seems mainly unaffected. The animation repeats 2 times. GFS_side_animation Second is the front view animation. This is the same perspective as on instantweathermaps.com So just imagine that you are looking those gph maps in 3D. The interesting thing here, is the intensity by which the vortex gets beaten up at 10mb. You can see fast height raises and around the end, the two waves almost connect over USA. If the animation would go on for a few days, the vortex would be pretty much a goner. GFS_front_animation I can only imagine how brutal the animations would look for the upper strat. I have to apologise for not making one, because I still haven't found the master grib files for the full GFS output, which has the whole strat included on the complete timescale. I can only find files for individual times, but that would takes ages to process. I guess I will have to wait for the event to go by, and then plot it from reanalysis. Personally I really like these animations, because it allows me to quickly asses the dynamics and spot some aspects that would otherwise be harder to notice on the classical 2D maps, since you cant see multiple layers at once. Nevertheless, here are 384h 3D layers of the upper strat. The layers from top to bottom are 1mb-3mb-5mb-10mb-30mb. The thing that stands out the most, is the wave intesity. In the upper strat, the Atlantic wave is the dominant one, but lower we go, the more dominant the Pacific wave gets, with the Atlantic wave hardly there at 30mb. This is pretty much the answer to the dynamics that Snowking was pointing out earlier, how the vortex gets tiled back with height on a horizontal axis.This pretty much explains it by showing how the stronger Pacific wave acts pretty much as a blocking ridge that prevents the vortex to tilt in general and prevents displacements towards that region. In the upper strat the Atlantic wave is stronger and is pushing the vortex toward west where the Pacific wave is not strong enough to hold in the "pat" position that we were used to see in the past days/weeks. First aspect is from the Europe side again, while the rest 3 are from the classical "USA in front" perspective, demonstrating the wave intensity with height and the impressive vortex tilt that corresponds with the changing wave intensity with height. I was thinking of pasting some ensemble output, but I dont want to be a partybreaker. The ensemble output has no dynamics, except for the classical two waves in the pat position. It seems that it just cant grab onto the dynamics, which is mainly the consequence of the low model top. I am counting on the improved ECMWF EPS to do the ensemble job here. Does someone remember the CFSv2 outputs I presented in November? 2-month lead time forecast. How about this for a verification? A few days faster than GFS, but still impressive with the general idea in my view, considering it was a mid-November run. (I cant believe I published such low quality processed graphics at that time, but It was as good as I was capable back then). Currently, CFSv2 is quite on terms with GFS, but as usually warmer on the waves and in the vortex core. I have noticed that compared to 12/13, we have somehow forgot about the ozone this season. There was some talk about it in the early parts of the season only. So much for now. Bring on the rock'n'roll. Kind regards.

After long 6 days, the Telecom people finally came around and repaired my modem. I had internet on my smartphone, but I was already over the data transfer limit. I will get straight to the point since I am low on time. SK and Matt have nicely summed the EC forecast, so I will be a bit unconventional again and just quickly present some basic plots. The most aggressive output is from the GEFS Control run this morning. Even the bias corrected version isn't that bad. It is pressuring quite hard, which can also be noted on the zonal mean zonal wind graph. GFS 6z isnt bad either. Greatly reduced polar night jet, with negative zonal mean zonal wind slowly approaching that notorious 60N threshold level. Vortex is almost beyond the point of return at 1mb in the 6z GFS. Emphasis on the "almost". On 10mb it is also struggling but after all that is going to hit it up to that point, I guess that it wont take that much more before it says "thats it, im out". Tho this is just a forecast, as I always try to emphasise. Nice graphics from @Lorenzo' previous post. I will try to gather the data, and make precursor pattern climatologies. Tho we have seen quite a few of them already, I will try to make it with my "new graphics" and we can perhaps store them somewhere on the netweather,tv domain for future reference. This would take much less effort than the GWO composites, since the amount of data-to-gather is like 1000x smaller. Best regards.

Naturally. As one wave decreases, the values of the other one can ramp up if it holds its position, since the zonal mean amplitude of one wavelength is generally higher than a double wave zonal mean. There is a limit to how much the double wave can compress the vortex (without an SSW or a general split). So as one wave starts to back off, the pressure on one side of the vortex is being decreased and the dominant wave can start pushing the vortex (if strong enough). Or in layman's terms, the energy of the compression is being released towards the weakening wave, naturally trying to reshape the vortex. And if at that stage the wave1 is strong enough to hold the energy "release", than the vortex can get from the "sausage" look directly into a displacement or at least into a quasi-displacement reformation. As for the actual values on the wave graphs, it is also only natural that as wave2 decreases, wave1 will pick up since it is "taking" over the matter, and it is usually on a shorter wavelength. So it also has generally higher values. Having a 1500m' wave 2, is in general terms as strong as 2500-3000m' wave 1, which is a lot. Tho this is just for the "feeling" of it, since of course it varies from case to case.

I made two composites for El Nino and La Nina. Nothing new, but just as a reference to a "average" winter pattern in the specific ENSO phase. Regards

When dealing with wave "activity", there is one vital thing to keep in mind. Troposphere and stratosphere are on two different "planes" (nothing new there lol), Meaning, that as we all know, most of the atmosphere' mass is in the troposphere. And as we rise up, the pressure is falling fast at first, and the higher we go it is basically falling on a logarithmic scale. The height is increasing at the same rate, while the pressure drop is getting lesser the higher we go. Basically what I am trying to say is, that 1km of height difference in the mid to upper stratosphere. may only mean the difference of 1 or 2mb (in general terms), while in the troposphere it can mean a difference of 100-150mb. At the same time, when going through a horizontal distance on a single pressure level, lets say 500mb, you are going to have a faster and smaller height change in a wave (100-200m, depending on the wave amplitude), than when compared to the stratospheric waves when you are going to have a wave on a bigger distance, but much more amplified (800+m), due to the reasons I mentioned above and some general rules of meteorology. So most (if not all) of the time the tropospheric wave amplitudes are all but impressive when they are on the same graphical scale as the stratospheric waves. Just a graphical example, I draw you "basic-general" wave amplitude in comparison at different height. Y axis is height in milibars, and X is horizontal distance. The height is only to represent, well, the height (isobaric). (tho the horizontal distance of the waves is not really in realistic proportions). As for the troposphere, due to the generally know causes, you can have more than 2 waves, up to 5 at least, depending if you count shortwaves or not. GFS and some other models actually have a special parameter, called "5-wave geopotential height" that is calculated only for 500mb. When compared to normal height map, it averages out the field to a max 5 waves. Basically showing more or less just the (actual) long waves (Rossby waves). Practical example: Reforming : Regards.

Thanks aginob, it does takes some time to plot all the stuff. The last 4 (wave) products are basically only meant as an example of a typical wave1/wave2, and not as a forecast. Btw, the CFSv2 mean is kinda in the same field as the GFS, tho with only one side warming up. But just as the 18z GFS, it retracts the core of the vortex back towards Siberia. And I will finish off with the 18z GFS zonal means. Temperature mean starts at 15000pa (150mb). The polar night jet still holding its act together, despite the otherwise decent 18z run. Regards.

Well, basically the elongation from the strat is reflected in the trop with each basically having its own "elongation" mechanism. The "filter zone" seems to be around 100mb. To put Chionos words into a graphical perspective with 10mb height examples : Wave 1 on the left, and wave 2 on the right. The wave 1 lat/lon chart is actually an analysis from 28/02/1871. Not the perfect example, but It gets the point over. The wave 1 perspective from above, is the analysis on my birthday in 2012. It is quite a vigorous wave 1 at that point, but again its a good example. And the wave 2 charts are the 12z GFS 384h forecast. I think that the stratospheric analysis that far back is way beyond our abilities. It is just too far back and there is hardly any data to do reconstructions. There was more data towards the end of 1800's, but event that is not really enough data to do an in depth analysis of the stratosphere. We can just speculate about it. At least that is my take on it. As for the LIA itself, I think there are plenty of technical and less technical publications on its possible/likely causes. Best regards.

I have noticed that ECMWF is perhaps slightly too optimistic in the 10 day range for the upper strat, being a bit too warm and having the vortex slightly too weak. I cant say if it is a bias or not, because I dont have enough observations. But it probably all originates from the over optimistic wave activity in the 10 day range, which I have noticed on more occasions this year and last year. I am not saying that the last run is unrealistic, but just trying to point out a possible bias. All that, while the GFS has a negative bias for height and temperature, growing with time. basically meaning that it has a slightly too strong vortex at 10mb in the FI. There is a notable difference after the resolution decrease (204-384). The same goes for ensemble means, while they have no obvious bias for temperature. Best regards.

Chionomaniac you beat me to the explanation, but since I have put time in it, I will post it anyway and for anyone else that might not be so familiar with the concept of "heights". Chionomaniac is referring to the geopotential height. I am not sure how familiar you are with that, so I will make a quick explanation (at least I will try to). Geopotential height is represented by the white lines (contours) that you can see on this chart, or on the "instant weather maps" geopotential height charts. Basically it s a parameter that tells us at what geometric height (elevation) is a certain pressure at a certain time. As an example, on this chart, we have 30mb geopotential height lines in DM (dekameter = 10 meters). If you look at one of the labels, it says 2224, which means that at that layer, 30mb pressure is at 22.240 meters. Now about the statement from Chiono: if you have lower geopotential height (or GPH, gph, height, heights, etc,.. as we call it), that corresponds with lower pressure. And this goes for our tropospheric cyclones just as much as for the polar vortex. Lower heights-lower pressure-stronger cyclone. That is why the lowest heights are associated with the "core" of the vortex. Over time, if you see heights decreasing (lowering) that means the cyclone is intensifying. If you see the heights rising (increasing), that corresponds with weakening of the cyclone or the vortex. (And opposite for anticyclones/ridges). Now the closer these height lines are to each other (or the faster the height changes perpendicular to the height lines), the stronger the wind, because of the pressure gradients. The faster the pressure changes through a specific distance, the stronger the wind (that is the general rule of thumb, but it has its variations, which are not so important at this moment). So to sum it up, the lower the heights are in the polar vortex, the stronger it is (or its core, depending on the overall picture), and if you would see the heights rising in the center of the vortex, that would mean that the polar vortex is weakening. And it also implies that the overall pressure gradients would decrease and the "jet stream" (polar night jet) around the vortex would begin to weaken, basically reducing the momentum of the polar vortex and making the warmer air intrusions (might there be any) more viable to penetrate the surf zone. And the vortex might even split if there is decent wave activity pressure being applied on the vortex itself. Of course this is just a general "flow of events" that you have to keep in mind, because it mostly varies from situation to situation and it depends on "why" and "how intense" the height rises actually are. There are usually some normal fluctuations of heights in the core of the vortex, so you want to see more intense or prolonged height rises. It is not easy to explain this, since there are so many variations, and I haven't even mentioned how the temperature comes into play. But for the general understanding, I hope I got the point over and now you might understand why the heights are just as important to monitor as the temperature. Best regards.

You have to consider two things while at it. First: Reanalysis like the ERA project, or NCEP R2, or JMA25,... are all basically just "hybrid models". Meaning they also have resolutions just like normal models. Usually the resolution is from 0.5 to 2.5 deg. or more, depending on the dataset. This also affects spatial distributions of different parameters and that is also why the warmer temperatures (on the analysis that I presented for Jan. 63), look more widespread out and not as close and focused to the main core as in the GFS chart. I have noticed exactly the same features in low resolution ensemble outputs. And second: These datasets are basically close approximations, calculated from all available data by numerical methods. So everything before the main satellite era (1979) has less data than after, also affecting the output besides the resolution. Now I am not saying that the outputs are not accurate, not at all. My main point is, that in reality, the situation in Jan. 1963 perhaps looked pretty much similar to our GFS FI scenarios, regarding the warming being closer to the core, as you would expect. But I had to explain in the long way. Couldn't agree more. I do believe that there is perhaps just slightly too much emphasis on the temperature itself. That is also one reason why I am trying to present other products, like zonal mean zonal winds, etc,.. to show in what state the vortex really is, and eventually if it is close to a "breaking point" (so to speak). Lets not forget that in the beginning of Jan. 1963, we also had wave2 and warming associated with it, but the vortex reformed after the wave 2 activity backed down, and it was more than 3 weeks later that it "fell" under the new wave 2 activity, this time stronger of course. Not trying to do any direct comparisons, but just a real life example from the past. Basically it is all still a bit too far in the FI to even start speculating about possible SSWs (tho I know no one here is doing that, but I read about it on other forums), especially while there is no real sign of the vortex actually starting to weaken at a high pace from inside out, which will be seen first on the GPH charts and on the zonal mean of the polar night jet. If I would have any power in weather, I would remove the Atlantic wave and keep the Pacific one, displace the vortex and then throw in the Atlantic wave for the final blow. But now we have almost extreme wave 2 activity, that is basically amplifying the vortex more than it is (/it will) destroying it, which was my main "concern" already way back when we first saw glimpses of a decent wave 2 coming into play. Who knows, perhaps the weather surprises. It certainly wouldn't be the first time. Kind regards.

Well, funny enough, I posted some 1963 animations, not long ago. To refresh the memory: ECMWF ERA-40 points at 27.1 as the SSW date. GFS 12z doesnt look too bad. Here are two zonal means. The temperature height goes from 150mb up. The vortex is getting more and more compressed, as also reflected on the jet, but it is still fairly compact. On a fun note, did I hear someone say "east QBO coming down slowly"? Cheers.

As I promised, some 12z products. Some old and some new. GEFS, Navy ensembles and CFS 12z, are more or less on the same page, with the FNMOC and CFS looking better. GEFS peaks at -28, FNMOC at -20 and CFS at -16. I will soon have to expand the colour scale up to +5 from current -5. I would also like to present some new products that I will add into my "stratosphere model artillery ()", since this year I decided to really try and model the stratosphere as best as I can, because there is a limited availability/diversity of stratospheric products on the internet, except the awesome FU-Berlin which sadly only goes to 240h. And admit it, we/you all want to see as deep in the FI as we can. I even included the netweather link on two products, as a test feature more or less. The graphics don't look the same (text font/size for example), but that is a matter of tweaking. The first new product is a zonal mean lat/time display, in this case GEFS zonal wind. It has a gradual poleward movement of the jet. The same display, only for temperature. Poleward warming is obvious in the later stages. Next is a simple stereographic display. I am experimenting with this type of display to use it mainly for reanalysis. Next are two "fixed time" lat/hight zonal mean products, which might seem familiar, since it is the same type of display as on the FU-Berlin, but not as pretty as there, because of the lower resolution of the FI GFS. Note: the vertical scale is in pascals, which means 100pa=1hpa=1mb. Last bu not least, zonal mean zonal wind. This is more or less useful for determining the SSW timing (if there is one), by spotting the zonal reversal at 60N @10mb. Best regards. EDIT: GEFS 18z really ramping it up, to -22. The best perturbation goes up to -8. This is a time/lat display through the longitude with the highest temp. increase.

@aginob: Hi and welcome. There is no source of these graphics, because I plot them myself, from the raw model data a.k.a. "GRIB" (gridded binary file) system or OPenDAP, GEMPAK, netCDF, etc. Depends on the model, or if it is reanalysis data, etc.. You wont found these graphics anywhere on the internet except here on netweather when I post them, or if someone else plots and posts them. I usually try and plot as much various models that I can find, including monthly ensembles, but I am surprised how many monthly/seasonal EPS' have a low model top (making it quite useless for strat. forecasting) As for the black/white background: That is just my experimenting with the graphical design of the product. And sometimes I change it for better visibility, etc... Hope I answered your question, even tho it might not be the answer you were hoping to get.

The EPS control has some height rises around 2-4/1, but you cant tell if it is related to the strat or not, tho it could be possible. The EPS mean has the overall vortex divided into two entities, one over the Canadian sector (connected with the main core in the lower strat) and one over E Asia. It is pretty much in line with the control run, but less intense since it is a 50-member average of course. AO does drop just slightly, proportional to the trop. pattern, but not really going negative since it is calculated at SLP. ECM32 mean and control are similar as their medium range cousins in this range. Further out, the control and the mean go for a reorganisation of the tropospheric P.V. complex. Tho in the end, the control run raises a high in the polar circle out of nowhere, pretty much like it would just drop out of the sky (hint hint? ). And the overall energy of the tropospheric P.V. complex is pretty dispersed around. As for the GEFS, it goes along with the ECMWF. To sum it up, I don't see any type of trop-strat response that we would expect to see. Actually we don't even have anything firm in the stratosphere to begin with. Best regards. P.S.: The variety of models+ensemble means (aside of GFS op, tho it is also not as good in the 6z run), have almost unanimously stepped down their game for the stratosphere in the last two runs. I will swing around later in the evening with some 12z products when they become available.

Indeed the GFS 12z operational run has stepped up the game from its cousin control run 06z. But I wont start cheering before there is some consistencywith the variety of models and in the GFS itself. This is the 3D profile of the upper layers, (1,5,10 and 30). 3D height is geopotential height of the respected level, and temperature in color. It is fixed on 384h, and basically just turning around, so it is visible from all sides. GFS_Profile.mov In the upper stratosphere, the vortex is having a slight difficulty breathing. Of course, this is just a part of the forecast. As for the GEFS. The control run remains fairly warm at -25°C, and GEFS mean goes further up to -28°C, reaching a new highest forecasted temperature. About the MT: yes there is an E. Asian MT in progress, though I doubt at the moment that this is really the root of the current GFS FI fun and games. Tamara has spared me quite a few words, by being the lovely voice of reason, amidst the slowly growing excitement from the GFS. Best regards.

CMC starting to ramp it up a bit, with the control going to max. temp at -25°C. Tho the temperature spatial placement looks kinda funny. The latest GFS Control going up to -23°C. Best regards.

As the GFS control run backs down to -36°C max. temp at 10mb, the GEFS ensemble mean goes up to -31°C, which is the highest forecasted so far this year. In the meantime, CFSv2 is still in overdrive with its best scenarios, with -8°C Max. temp.

If someone would give me 10€ for each time I experienced this, than this time next year, I'd be a millionaire. I experience this around 3-5 times per year at least. I live on a south slope (1050m ASL) of a 1600m high hill. Now every time there is a storm on the north side of the hill, or sometimes even right next to the north slope, I see awesome lightning displays (at night of course), but practically no thunder. I remember once, when the storm was not far to the north, so pretty much 50% of the tower was visible, and the anvil stretching to the south, pretty much beyond my house at around 14km I think was the height measured by the radar. So as I was getting my photo gear up and ready, the fog moved in and engulfed us. And that was a decent show, because the lightning in the tower, and some occasional crawlers in the anvil, lit up the fog. At one point, my mom said, "oh gosh we are in the storm", because the flashes were so bright and there was fog everywhere. It wasn't long before she figured out that there is no thunder to go with that lightning, so I explained to her what was going on. The bottom line is, that there is no possibility for a lightning discharge in a storm to not produce sound (thunder). You just either hear it, or not. This storm I described, was one of many that is in the location, from which the sound waves just don't reach me. Despite the fact I was only around 4-5km from the storm. There is terrain configuration, sound dissipation, sometimes the wind can reduce the sound range of thunder, etc... Each storm has a visible and audible range. Of course the visible range being far greater. I usually also see strong flashes of light that can light up the ground, from storms that are up to 60-80km to the north in the mountains, like this year in July when there was an amazing flashing display from an MCS in South Austria. And one one occasion, I was photographing lightning around 80km to the SE. I am on a hill, and towards SE I see a flat terrain (more or less) as far as the eye can see (clear day visibility here is around 100-150km). And I heard deep low frequency thunder from that squall line, associated with positive discharges. Which is another thing to consider. The intensity of the discharge. More energy released (higher voltage and amperage), the louder the thunder, and vice-versa. Cold season lightning is usually weaker, so I would guess the thunder range is not really that far out, but situational by different "variables" I mentioned earlier. You also said that you only saw flashes and no forks, which means that the lightning must've been more CC in nature than CG (if any at all). And with lightning higher up in the the cloud, it will produce brighter flashes to places further away, but of course no thunder will reach those places. I could go on with many examples when I can hear thunder (most of the time its low frequency rumble from positive discharges) from quite a distance, but little to no thunder from storms close to the north. And I dont really like the term "heat lightning", because that was originally used to describe the lightning far away, as a result of the heat building up during the day (and being unrelated to storms), which is nonsense. But nonetheless, @TheToastPeople gave a correct description of this "phenomenon" if you wish to call it that way. So to sum it up: To see lightning (even bright flashes) and hear no thunder is not uncommon or strange at all. There are many variables that affect the distance that sound waves travel. And sometimes bright flashes from far away can give you the wrong idea of the "spacial placement" of its source. So use weather radars and lightning locators, which will quickly and accurately explain what is going on. Best regards.

I had the same feeling all along. Studies of this particular kind are also not really that old, so I am sure that there is some great potential in it, just waiting to be further discovered. In a certain way, perhaps similar to recent years, when most of the public never heard of the polar vortex, let alone an SSW event. It was kinda a "taboo" topic, reserved for people who can work around the heavy physics. But now, every year there is more emphasis on the real potential and role of the stratosphere in winter synoptic patterns. And it is also getting more and more popular and recognized with each passing year. And even tho it is not really an easy subject, people seem to like it overall and the intensity of an SSW and the potentialy good outcome for winter lovers, around the N hemisphere. In the mean time, GFS control run kicks it up a notch, with the max. temp. at -23°C. Best regards.

No problem, tho my intention was not really to correct you, but just to point out the date, so people wont get confused. GFS Control run doesn't look too bad, considering how the operational run looks like. And considering the ageostrophic flux, it does seem to have some decent wavebreaking, which is quite remarkable, given its 2mb model top (or perhaps that is the reason. ). Cheers. P.S.: On a side note, as noted on the NOAA modelling site, they are considering ensemble resolution increase to T574L64 (model top at 0.3 hpa) in 2014. Not confirmed yet, but it is a possibility. And I would say that it is a likely possibility, given the resolution increase priority at NCEP. The most evident being the considered GFS resolution increase to T1148 (~18km) on a semi-lagrangian grid. Tho the question remains, how the FIM model comes into play, with its revolutionary icosahedral grid.

The scales are not the problem. Its the date. You have made the composite from 1.1 to 13.12. This is the actual mean so far for December. And this is the daily mean for 30/12, from the year collection in Chionos composite form the first post.

You pretty much explained it with the rest of your post. I still cant decide if I like this wave 2 or not, to be honest. I guess that it can be both a blessing and a curse at some point. But it is always good to see some activity, rather than an overpowered polar vortex, "wreaking havoc" on us with positive NAM. (tho we really aren't far from it at all) Looking at the 5mb 384h forecast from the latest 12z GFS: Really an impressive wave 2 pattern. The "Highs" really compress the vortex, and this is as close to the Chiono's balloon analogy as it can get at this point. They also tighten the pressure gradients, thus increasing the polar jet speed (/zonal flow). That is also why you see the jet tightening, and the strong easterlies allover tropical stratosphere on the FU-Berlin plots. That is also evident on the GFS U/V plots I presented just a few posts back. At this point I do feel that this easterly phase in the tropical stratosphere due to the wave2, is more important as the +ve QBO down at 30-50mb. But lets leave that for some other time. Basically one of the "problems" I have with this wave 2 pattern, is that the Atlantic wave normally blocks the disposition that would otherwise occur with just one wave (and boy would that be a decent wave1 in this case). And it is also keeping it in place or immovable. But that is a logical assumption, so what's really "bothering me", is the question what would happen if we would have just wave1 disposition and how much it would affect the low-strat/trop. pattern. But I guess we will never know. Another forecasted effect of this wave2 is on the momentum or energy of the vortex. The vorticity forecast for 5mb 384h, from the 12z GFS, does show just how the Pacific high is interacting with the vortex, showing the "hook" feature, indicative of wave breaking. But overall, the vortex still has a fairly good composure, tho quite under pressure (no pun intended). Left (in green/blue) is relative vorticity, and on the right (in many colours) is isentropic potential vorticity (IPV) ~5mb. Both showing the well defined, almost textbook "leak" of the vortex' energy, induced by wavebreaking. Speaking of wave breaking, another indicator of the latter, can sometimes also be spotted on the ageostrophic wind plots, basically due to it showing geostrophic wind imbalance and deviations, which can be induced by fluxes in wave breaking. Normally in a healthy textbook polar vortex, you don't expect to see much ageostropchic wind, since it is a quite balanced planetary scale feature. And usually the only thing disrupting it, is wavebreaking in the upper strat. To put it in practice, lets look at the ECMWF wave chart and some ageostrophic wind plots. Strong wave activity, focused between 35N and 65N in mean, maxed in upper strat. at around 50N. The GFS plot for 1mb ageostrophic flux for the same time period as the ECM above, is quite in the same area actually, on the outskirts of the vortex and in the waves. Tho there are some differences to be expected, since we are talking about two different models here. GFS does seem to be weaker with the wave2 at this point, based solely on the ageostrophic plot, which would also explain why the ECM is much warmer and aggressive at the highest level of the strat. than GFS at the same time period. Notice the strong fluxes over tropics, but that is a different system. Now going to latest GFS 12z 384h, lets look at 5mb (left) and 1mb (right). Added on the plot is the ageostrophic flux vector (arrows). It kinda goes wild, but if you look at the 1mb height that Chionomaniac has posted, it is logical that somewhat decent wavebreaking could be occurring. Poleward ageostrophic fluxes also sometimes seem to correspond with areas of increased temperature. But it can be situational. Just some of my experimenting with stratosphere modelling. Now of course, some might want to know what all this mumbo jumbo really means in terms of possible SSW. First we have to realize that these graphics are basically just model forecasts. And in those forecasts, we have decent wave activity occurring and quite some pressure is being applied on the vortex, tho I must say that it is one beastly vortex to bring down. But you know what they say, the bigger they are, the harder they fall. Chionomaniac has pointed out a thing, that is actually the second problem I have with this upcoming wave2. Wave activity does not last forever. It either ends on its own, through the change of forcings, couplings, propagations, etc... or by an SSW also. Now something is telling me that an SSW is not likely to end this wave 2 domination, at least not by what the forecasts are showing right now. So we might waste all this time with the wave2 without much of an effect in the end. But that is quite a bold statement, I admit. Is the wave 2 activity expected to apply pressure onto the vortex? Yes. Do we have forecasted warm air intrusions into the core of the vortex? Not yet. In my view, a cold vortex is a healthy vortex. At least what we have on the charts with an overall strong momentum around the vortex. I don't think that the pressure-gradient force is enough to disrupt or even split the vortex on its own. Or looking back at the 1963 event, where there was also wave 2 with decent pressure-gradient force, but the vortex kept its composure without much problem, until the warm air finally began engulfing it, and warmed the core of the vortex, reducing the overall pole-tropics thermal gradient, raising heights and pretty much split it down the middle with ease, since warmer air also promotes height rises and so it was easier for the two waves to connect through, while it would be almost impossible to penetrate a -85°C cold core vortex just by pressure gradients alone. At least I haven't seen that before, and I've been through quite a few historic SSW events in the last year, by reanalysis. So please feel free to correct me if I am wrong. So to sum it up: Tho the upper strat height charts look really nice in the FI period, I would really like to see some warmer temperature to go with it, which should be our main "wish" at the moment. It really pains me to see such a pattern and just -35°C max. temperature over only a few grid points. Even the CMC ensemble mean is warmer than GFS operational, not the mention the CMC control run, with quite an area of -30°C. But the model forecasts are not perfect, and there might be a cool temperature bias at the moment on GFS, especially if we compare the GFS to EC. I would personally expect quite higher temperatures to go with such intense wavebreaking in GFS. Basically I am suspecting that GFS is greatly underestimating the temperature aspect of this wave, from run to run. Occasionally we do get a warm run, and then the next 3 are cold ones. So perhaps the GFS cant really handle such intense processes the right way in the FI? So many questions, but almost no answers. I guess only time will tell. At least we have some very interesting stuff to work with at the moment (tho it could/should be warmer ). Best regards.

Wow, thank you very much for your positive opinion! I've been learning English for about 17 years now, since I was 5 years old, so I guess that in such a long period I should know some basics of the language. The professional terminology on the other hand, is something totally different. About that career, well, I have no formal education in meteorology and/or physics, so that is out of the question. But nonetheless, I really enjoy learning on my own, step by step. Lets face it, just a year ago when I joined this forum, I hardly knew what wave 2 actually was and how to interpret it. So at this point it is my turn to say thank you to all who contribute to this great thread in any way and also help us all to learn more and contribute to the collective knowledge. Since the paragraph above is perhaps a bit offtopic, I made some GFS plots of the zonal (U) and meridional (V) wind components, to keep the post on topic. I changed the perspective to lat/lon grid instead of the usual polar stereographic, because this perspective really gives you the feeling of the overall connection between the north and south hemisphere, the QBO and the fairly textbook wave-2 height pattern. And the +ve QBO struggling to keep its composure at 30mb. And I must say it is quite interesting to see that there is no +ve phase whatsoever to bee seen above the new negative phase coming down to 10mb. Tho I guess there is still time for that to develop. Best regards. P.S.: I apologise if my usage of smiley icons is perhaps excessive.

CFS looking similar to other models. But boy oh boy, does it turn into overdrive just a little bit later. But there is no reversal at 60N (as it is also obvious from the GPH chart above) at 10mb (around 30.000m). Or it hasn't propagated down yet, since it is reversed in the upper strat. This cross section is over the 60N lat. line around the globe. Distance (X-axis) is equal to 0-360 deg. longitude. So the middle of the map is at 180W for example. I kinda prefer this height-longitude cross sections over the zonal mean charts, because you can get a better feeling of the actual spatial distributions of the zonal momentum. Based on all the stuff I have seen from CFS so far, it really seems that it is always in a hurry to tare the vortex apart, with some godlike wave-breaking at the top of the stratosphere. Or in scientific words, it has a bias. The forecast of this run is highly questionable, so my main purpose with this post is to present new experimental plots, like the zonal wind for example. And I have managed to finally put a temperature legend on the single level plots. Tho I must admit that it looks quite on par with latest GFS. Or vice-versa.

Thanks to Lorenzo for reminding me about the vorticity. Not really of much use, but still, the 850K potential vorticity (~10mb) for the 1963 SSW. It doesn't look that pretty because of the low resolution (2.5°). These animations seem more useful as bundles of images, so you can pause on a certain date to see the plot on that day, rather than an animation sequence, because the images are on a 12h interval, because the file size would be really big if I would do the animation on 6h intervals. 1963_850K_Potential vorticity And the 6z GEFS 10mb ensemble mean at 384h. Max temp. at -36°C. And all the same as above, only this is the CMC 00z ensemble mean. Max temp. -30°C.