Recretos

Well, looking at the negative MT event in 63, and the recent negative MT spike in NA, I present some reanalysis charts. 500mb is just for corresponding pattern. The MT itself seems to be calculated from SLP integral and topography gradient. I have just started to look into this, because I have in plan to actually plot MT forecasts from models. I just need to figure out the correct equation/formula and somehow script it into software. And I would not be surprised if you would find a similar pattern for a positive MT event in S. America.

Well, funny enough, speaking of the 1963 event, I went over to the ECMWF data server, and grabbed the ERA-40 reanalysis data for this event. I made two animations for Geopotential height and temperature, on 10mb and 5mb levels. The reanalysis dataset goes all the way up to 1mb, from 1958 to present, which is quite remarkable, since NCEP datasets go only up to 10mb. Looking at the latest GFS, and previous runs, I think you might find some striking similarities. Data belongs to the ECMWF, I just plotted it. (I usually forget to give credit of the dataset). Notice: There might be a slight positive temperature bias in the time leading up to the event, due to the event itself being in the non-satellite era (at least not in the main one), but the overall positioning and temporal-spatial values are quite on the spot. Notice2: The colour legends are not the same as on the plots I made above from MERRA and GFS. I usually make custom colouring, based on the values. Notice3: 62/63 was a strong -ve QBO phase allover. Tho we are in transit from + to .- Notice4: It is painfully obvious from the animations, that the source region of the temperature wave was North America. Looking at archives and doing some reanalysis, there was actually a strong negative MT event (-2 to -4) over North America prior to the intrusion, and a positive Asian MT event (+2 to +3). Values are averaged over the month. Notice5 (and the last one ): Looking overall, it almost seems like the vortex sealed its own fate through atmospheric succession in the first place, seemingly triggering a chain of events, leading up to its demise. This is just my opinion after going through all the data so far. I haven't read the report yet, that Mr. Gael_Force linked. But in the end, its almost always like this, or is it not (including me, not reading any technical papers ) ? The sequence shows the warming appeared on 5mb before 10mb, normally due to downward propagation. So lets look for that upper strat warming over North America, shall we? The main purpose is just to show these animations for comparison, since the 1963 event was pointed out. I am not trying to imply that we are going to have a 63 event allover again. Tho it is not impossible. But lets leave that for another time. 10mb. The "Highs" are in black contours, for better visibility. The time frame is from 01/01 to 31/01 (time included on the plot), when the main activity leading up to the event was in progress. 1963 10mb Animation (37MB) 5mb. Again, the highs are in black, for better visibility, and in the same time frame. 1963_5mb_Animation (40MB) Best regards.

I plotted the 5mb and 1mb gph+temp., from the awesome MERRA (@NASA) dataset, as a reference to the max. period of current forecasts. I gave black contours to the high on 1mb, for better visibility. And the latest 6z GFS forecast, for comparison. Again, black high, for better visibility. I am not trying to say that we want to see the same development as last year. These are just comparisons of the development (or expected development, in the case of the GFS plot). Max temp. -20°C, SE of Japan. About the wave 2: Lets just say that I am not really thrilled to see wave 2 activity picking up, while the core of the mid-low strat. vortex sits over Greenland/Canada. If it were to back off first, to the pole or Siberia/Scandinavia, than we can talk. But nonetheless, it is still better to poke the vortex at least and try do disrupt its momentum, rather than leaving it alone to "wreak havoc". Its all in the perspective basically.

Sadly I don't think you can find any explanations that are "user friendly". The topic itself is quite linked to heavy physics. The only way would be that some expert in this field can interpret the knowledge for you in a user friendly manner. But to answer you, even tho this is not really my field of expertise. I had my dull moment yesterday obviously, because I said left and right instead of west and east. You need high pressure east of the mountains and low pressure west of the mountains, for a MT event that we want to see. Looking at your specific case: This is clearly one of the "many variations". Looking at some previous cases it actually does look semi favourable, now that I have actually rotate it for a better view. I drew the ridge axis and trough axis. North America on the other hand, is much more straight forward in being obviously less favourable, with clearly what you don't want to see for a favourable MT event. Just my two cents. Best regards.

I made some plots for comparison. All temperatures are in Celsius. Keep in mind that ensemble mean tends to average out the "spikes" in temperature. GEFS gribs only go up to 10mb. But its no good news there. Highest temperature of the ensemble mean is at -40 over Japan. The calculations do go up to 2mb, so if there would be any significant warming up there in the model going down, I am sure we would see it eventually on the 10mb plane. GFS Control run isnt really impressive either for 10mb. Max. temp at -36, on the other side of the globe, compared to GEFS. The CMC ensemble mean for 10mb looks almost better than the two above, with the max temp at -30. CMC Control similar, with max temp at -30. CFSv2 for the same period also looks similar, with max 10mb temp at -27. At 1mb, the CFSv2 max temp is at 1°C. Now for fun, going further with the CFS to 1/1/2014, it has max temp of -17 at 10mb, and a decent "antivortex". The core of the vortex is also not as cold, with the low around . CFS really picks up the pace in just one week. Looking at that chart, I would say you need just the opposite. High pressure right of the mountains, and low pressure left of the mountains, I think is the general "rule of thumb", with a huge number of variations of course. Best regards.

Ensemble FI, but still, very decent tropospheric setups appearing on the ECM EPS lately.

Well, I was about 60% done (or around there somewhere), when I had some other priorities, thinking I can just go back to it when I will have time. Turned out that my methodology was just as complicated as it was efficient, so I totally forgot the system I was using in just two weeks (yes it was that complicated but very efficient, as I said). Later I got a new computer, delaying it even more, so I gave it a shot two weeks ago but I just couldn't figure it out (changed excel versions in between too). I will just try to salvage the finished data, and complete the rest when I create a new methodology for the efficient data extraction from the dataset. Talking about GWO composites of course. MJO is also in plan. Well, that's a funny story actually. Yes of course I tried that, but got my RAM almost up in flames because when I changed the name macros it started to reload the whole datasets for all layers. Gotta get around this first, and then tweak my methodology a bit, to start with the names before I have a XY amount of layers and data that starts reloading. It was too late yesterday to start layering from beginning just to add the time stamps. So I decided to post the animations just for the sake of the feeling how a 3D SSW visualisation looks like. So the time stamps are definitely a priority in this case. Animations like these just don't look professional enough without it. Thank you. It is late, so just a quickie from me, too keep this post on topic: GFS and EC are generally on terms, with EC looking better actually, because of that wave 2 which seem more defined on EC. GEFS 10mb mean, is kinda closer to EC than GFS actually (tho I plotted CFS instead). Further on, we might see that Aleutian high picking up the pace (as the CFS was also suggesting at some point), as it is also suggested on the ECM 15day ensembles. These are normalized anomalies, so you wont get confused. Best regards. edit; Lets also not forget to look at possible MT upticks in the near future.

Very interesting. I will definitely consider this one as more legitimate. But there are probably differences in the testing modes. Some used averaging of the runs, some just individual runs, etc... Too bad the full article that I mentioned is not free, so I could see what was their method and compare it to the results from Long. That pdf does give some basic info, but the methodology is not really described. Speaking of the 2009 event, I actually plotted some 3D visualisations (never before seen ) for it as a test. I extracted the data from the NCEP DOE Reanalysis 2 dataset, on 6-hourly intervals. The time period is from 12/01/09 to 05/02/09. The 3D surface is the geopotential height, and the colours are the temperature at that layer. Layers from top down: 10mb, 20mb, 50mb, 100mb, 250mb, 500mb and surface temperature. https://dl.dropboxusercontent.com/u/16376055/09.mov This is is from the pacific viewpoint: https://dl.dropboxusercontent.com/u/16376055/09_pac.mov This is just some preliminary testing. I am just trying to figure out the system, so in the future I will be able to plot basically any SSW event. Will try to figure out how to plot additional parameters too. Best regards. EDIT: As a bonus, here is another animation for the same period as above. There are only 2 layers. The layer above is the 3D 10mb geopotential height, and the second layer is the 10mb 3D temperature topography. The temperature topography is lower so both can be nicely seen, and the temp. topo kinda looks like a better indicator of the dynamics. https://dl.dropboxusercontent.com/u/16376055/09_up.mov

GFS 12z forecast: 3D geopotential height, with colours representing temperature. Layers from top down: 10mb, 30mb, 50mb, 100mb and 300mb. Time period from 27/11 to 4/12, one image per day. The animation repeats 4 times, so try to find some propagation. The facing is the same as on the "instant weather maps", with USA in front and EU to the right. Cant wait to do these animations with some actual SSW related up/down-welling. gfs.mov And the CFS just doesn't want to give up on that Aleutian high. I was reading some recent studies on the daily CFSv2 and stratosphere, and I came across this abstract from a recent study from Qin Zhang, Chul-Su Shin, Huug van den Dool and Ming Cai. "...We further show that the CFSv2 has a high prediction skill in the stratosphere both in an absolute sense and in terms of gain over persistence except in the equatorial region where the skill would mainly come from persistence of the quasi-biennial oscillation signal. We present evidence showing that the CFSv2 forecasts can capture both timing and amplitude of wave activities in the extratropical stratosphere at a lead time longer than 30 days." "...In particular, the CFSv2 is capable of predicting mid-winter polar stratosphere warming events in the Northern Hemisphere and the timing of the final polar stratosphere warming in spring in both hemispheres 3–4 weeks in advance." It would be interesting if I could get a hold onto some daily averages from the daily CFS, except only individual run averages. As a said some time ago, I do remember some updates or fixes being applied last year, that probably affected the increase in skill scores since the bad scores in 2010 that were presented in the study by Perlwitz and Zhang. Tho the CFSv2 ensembles still have some issues with implementing the Eurasian snow extent. Looks like fun times could be ahead. Best regards. Edit: Thanks Lorenzo. My goal this year is to test these visualizations and products, especially if we manage to get a MMW, and analyse propagations with the help of these 3D animations.

Speaking of heights and waves, I have managed to plot a 3D geopotential height. Its just a random GFS forecast, only to show how the heights look in 3D. The vertical scale is obviously not proportional with the real one. Just so you can get the feel of the "fluid" dynamics with the P.V. The levels from top down are: 10mb, 30mb, 70mb, 250mb and 500mb. The right image is a look from bottom up. The "valleys" are lower heights associated with troughs and cyclones and the polar vortex up in the strat, while the "mountains" are ridges and anticyclones (higher heights). Pretty basic stuff to understand. And the same system, only the CFS and this time for the 27.11 around that wave 2 period. Levels from top down: 5mb, 10mb, 30mb, 70mb, 300mb and 500mb. I will try to make some animations in the future, which might look really interesting. I'm just trying to model the polar vortex as good as possible this season, as we head into more interesting times, and of course to help present the perspective and the real "feel" of the vortex and its influence. And also to support all the great analyses here in this awesome thread (for which I have a real lack of time lately) and trying to take them up to the next level. (no pun intended ) Netweather.tv dominating the stratosphere scene. EDIT: Added a 30mb height animation from GFS, with nicely seen pressure on the vortex and the reformation, and the new waves pressuring in the last time periods, as also seen on the 2D version: 8.mov

Yes, I missed this one, because it was not implemented yet. 14 levels above 5mb is a good upgrade. The testing was since June, but looking at the score card, it is actually worse than the current cycle in the lower strat. Too bad they don't have the mid and upper strat. test scores. I guess that I better remove my critique from the post above.

~ GEFS has the model top at 2mb with 42 layers and CMC also at 2mb with 40 layers. This isn't so important in our current case, but it is important in general for upper strat. wave breaking implementation and downwelling processes. Ok about the current forecast which seems to be the hot cookie at the moment. It is a pure demonstration of the trop-strat relationship, which has been mentioned quite a few times now. In this case we have the pure troposphere effect on the strat. But since there is no warming and nothing particular to go with this effect, I expect the P.V. to reform without much difficulty, which would basically mean that the strat. would not "respond" to the poking from the troposphere. To put it like that. Another thing to consider when talking about the trop-strat relationship is the scale of the polar vortex. You have to put the polar vortex into a real-scale perspective. If you could take the polar vortex and resize it to the size of your palm and keep the original proportion, it would look like a CD or even thinner. All the maps and cross-sections increase the vertical scale because otherwise it would be hard to see anything, if the original ratio would be kept in a hemisphere cross-section. So the trop. and strat. are much more connected that it may seem from the very "high" cross sections and other products. The actual height of the polar vortex from the ground up to the stratopause is the same as the distance between London and Reading. Putting this into perspective really helps to easier understand the processes like wave breaking and mountain effects through mountain and frictional torques. Ok, I wondered off a bit there, so back to the forecast. After playing around with ensembles for stratosphere I can say that they are a decent indicator of development, but after 240h, the usual spread kicks in and averages out most of the potential dynamics. Especially with a system like the ECM EPS with 50 members. So I wouldn't worry too much if there is no access to the ECM EPS. As a "consolation prize" I will show you 50mb forecast around 240h from NAEFS, GEFS and CMC/GEM ensembles which I plotted fresh from the 17/11 00z run gribs. The ridge is already mostly averaged, but it is still early enough in the forecast range that the main idea of the wave2 pressure is kept and seen. And the quite averaged 10mb GEFS and CMC ENS 384h forecast, but it sees the Pacific high, just like some latest operational runs. Less intense of course, because it is the ensemble mean. On the far right is the CMC control run at 384h. Out of time for now, but I might present some latest CFSv2 strat. forecasts soon. Best regards.

As Lorenzo has pointed out, there is some wave2 appearing on the EC forecast. The anomalies suggest that, and I also plotted the flux vectors through the Atlantic wave from the GFS for that time, and there is some pressure being applied on the vortex. The left axis is the height in meters. The CFS forecast is somewhat in line with the latest GFS runs, but it is kinda slower. It has the similar look on the 10/12 period, which latest GFS runs are promoting for 01/12. Just throwing it here for future verification. Best regards.

I agree too. I wasn't pointing out that as an actual CW event by definition, but more like in a literal meaning "warming over Canada". I am calling this a run error for now. And an obvious one too. You cant really shift from +QBO to -QBO in one day. And all plots for day 7-10 seem out of context, so most if not all of the products in that range seem false to me. We will see what will happen with the new run.

I apologise for the double post, but here is CFS very deep FI with some Canadian warming for you. 10mb left, 1mb right. And yes I know very well that the CFS-Stratosphere relationship is not that perfect (tho I remember some updates being applied, but I am not sure if it was tested yet). So this is not meant to be a real forecast, but just something to show an option for early Jan. strat conditions. Regards.

I've been playing again with models, now that I have figured out how to plot different stuff. For fun, here is the CFSv2 latest daily forecast for 10mb for Christmas. Very deep FI, so basically this is more like a test plot to show you that I will be making all kinds of model plots for stratosphere, from models of which you cant find stratospheric forecasts anywhere in the world (GEFS, NAEFS, CFS). I also have in plan to plot cross-sections of mean(U-V-Z) flow, and other parameters on different levels. We do have the GFS basic strat forecasts and special parameters from the ECMWF control run at FU-Berlin up to 240h, but that's about it. There is no other special stratosphere modelling anywhere on the internet (like ensembles or plots beyond 384h) for the sake of diversity and to look at different perspectives when/if there will be interesting situations. So I decided to take matters into my own hands and make individual plots for our beloved stratosphere. I am only experimenting with this, so for now I can only make individual plots, but with time I think I can figure out how to make automatic plotting. And the visual look is also pretty basic, but It is more than enough to show the main idea of the forecast. Best regards.

I've been playing around with model grids, and somehow I managed to figure out a system, which allows me to plot NCEP model data. So the first graphic that I am going to present, will be GEFS 10mb ensemble mean, for height and temperature on the 384h period. This should be very interesting when potential SSW come into play, when I will be able to monitor how the GEFS can grab onto it. All in all, the P.V. seems to be in a fairly good shape. The minimum centre temperature is at -85°C. The second graphic is also GEFS 10mb ensemble mean, but this time the height and the height deviation on 384 period. The maximum deviation (red areas) is around 350m, which in fact is not that much, but I am 100% sure that it has to do with the positioning of the vortex centre (different members have it shifted slightly). Best regards.

Well, I would say just the opposite. Both GEFS and ECMWF are forecasting a phenomenal blocking to develop over Aleutian islands in the 8-10 day period. Considering this is in ensemble 240h period, such anomalies are really significant.

Thank you. I learned a lot here, so its only fair to try and give something back. But of course I still have a huuuge amount to learn in the coming years, because this subject is way too big to handle it in one year. @Chio (or as I first called you, Mr. Chionomaniac ): The averaging does take away some possible correlation. I will have to wait until the tool can plot monthly subsets, before we can go deeper in the matter, with your recommended areas. I will try to do some subtractions of the polar vs. tropical temps, and then try and correlate that with the zonal mean zonal wind. About the ozone: I came across some O3 data during my short but rich reanalysis career. Total stratosphere ozone by ECMWF data. Recent years on the left, and zonal monthly mean on the right. For further in-depth analysis and year-to-year (even daily) comparisons, you can find the best O3 data on the web here: http://www.temis.nl/macc/index.php?link=o3_msr_daily.php Meanwhile, GFS and GEFS are slowly but steadily starting to agree. Regards

by chionomaniac: "The tropical stratosphere at 10hPa is currently running at 5ºC below average and this has reduced the thermal differerential by about a third between that and the polar stratosphere. it will be interesting to see how this is affecting the mean zonal mean winds at 60ºN (when I can find a site that is accurately measuring this presently)" To divert your attention from the probabilities of a mild winter start, I made these two plots for you. I've plotted a comparison between 10mb/30mb 25S-25N temperature and 55N-65N (averaged at 60N) zonal wind. I used ECMWF' ERA-Interim reanalysis dataset. Values are averaged over 3 months (Oct-Dec). Blue line represents the temperature, and the black line represents the zonal wind. It is not easy to find a direct correlation in this, but it is averaged, because the tool doesn't support the creation of monthly subsets yet. Keeping in mind that there are obvious correlations expected with the onset of SW events, when the zonal flow is disrupted/reversed and the tropical strat. tends to cool at about the same time. We had a slight up-tick recently in the EP-flux department, and some in the days before, with the wave 1. The first "episode" seems to be adjacent to the wave 1 that we have/had from the Pacific region, centred mainly between 55N to 70N. Added is the overlay of the normalized height anomaly and the wave 1 activity in the same temporal and spacial scale. Given the analysis, the latest "peak" of the EP flux seemed centred around 40N, most likely in E Asia, and connected with the recent mountain torque event in the region. Next up, something a bit more "average user" friendly: The GFS operational seems to continue with the idea that slowly strengthens the vortex in the mid-late period with slowly increasing zonal flow, after the wave 1 declines, but keeping some pressure from the E Asia/Pacific region. In the troposphere, both GEFS and ECMWF ensembles reintegrate the vortex, with a responsive peak in the AO. In the FI, GFS tends towards a somewhat like wave 2 scenario. The North Pacific and the Atlantic areas being the "pressure zones". A similar scenario is also evident on the NOAAs experiment model, but with less intensity than the GFS, and also constantly increasing the mean wind speed (expected for this time of year). Which is a reminder that no matter what we throw at the vortex at this time, it will strengthen further at every change it gets. And the as we head deeper into the cold season, the vortex core will cool down, more or less regardless of what is happening around with the height fields. Unless some dramatic events would take place, but that is highly unlikely at this point. Since the operational runs are useless in FI, we have to lean towards ensembles for some support of the corresponding tropospheric pattern for the before mentioned possible wave 2 "look alike" situation. Emphasis on the look alike. The support is kinda in place, but the ensemble spread at this range is blurring the overall image. http://shrani.si/f/2Y/3n/2KIOXBJU/z500cpcterciles198to360h.png In the meanwhile, the upper strat vortex doesn't seem to be bothered too much by this mess below, keeping a steady strengthening trend throughout the forecast length, showing how all the arguments are between the mid-lower stratosphere and the troposphere. Which only further proves the point Chiono was trying to get over to all, about the complexity of the troposphere-stratosphere "dance" (which by the way, was an awesome analogy http://f1.nwstatic.co.uk/forum//public/style_emoticons/default/biggrin.png). http://shrani.si/f/23/8w/3y3tXFGt/wmag5f336.png http://shrani.si/f/3D/VR/3cFdrDLX/nhhgt1mb384.gif http://shrani.si/f/e/Ab/2O6fpLBp/nhhgt5mb384.gif We will have to wait for the decline of the wave 1 activity and the strengthening of the vortex, before we can make further assumptions of the vortex situation as we head into November. But it does seem like a quite busy start of the stratosphere watch season, which is quite positive down the line. http://f1.nwstatic.co.uk/forum//public/style_emoticons/default/smile.png Kind regards. edit: applied a quick fix of the quote at the start, over the phone, because the quote window somehow disappeared.

Not at all. I would go as far to say that some ridging/blocking conditions are of great importance in the first place. Just like chiono said, its all a part of the troposphere/stratosphere coupling. And as is also evident on the composite for the weak polar vortex. And just for consideration: Split SSW: If you have a split vortex from the Pacific and the Atlantic, I don't think we will have to think twice where the split is "likely" to connect, or what would happen to the connecting ridge. A huge generalisation, with exceptions to every rule, but I hope the point I am trying to make here is obvious. As Matt has pointed out, a decent mountain torque event is in progress in E. Asia, starting around 14th, with the increasing pressure gradients, and currently peaking. The 10mb and 30mb temperature graphs look intriguing, with a temporary hold of the cool-down. I have plotted the 30mb and 10mb GFS forecasts, with 30mb on the downward trend, while 10mb kinda holds. Best regards.

The 2009 SSW was a nice "downweller" actually. Thanks Matt for the links. Some nice content there, which is somewhat more "pro" oriented, but I am sure that we amateurs can also make the best use of it. I am late for work, so just some quick correlations between Oct-Nov QBO and the stratosphere. I caught the brief window when the NCEP reanalysis sites were available (offline atm.) and decided to make some correlations for use/comparison in the near future. A quite high positive correlation between the 10mb temp. and the QBO. In this particular case, it shows where the temperature changes/increases in a west (positive) QBO (positive correlation). Nothing new really, because of the known relationship between the QBO and BDC. Geopotential height. Some more pressure form the Pacific area is evident on the correlation, as well as on the forecast. But we have to keep in mind that the QBO-Stratosphere relation is also affected by the Solar activity. So the problem with these correlations is that it has all the years with low and high activity. I am sure I could get even better correlations when filtering the years, but that is impossible with these basic reanalysis tools. Now, a somewhat more interesting (but expected) correlation between the PNA and Z30mb. The correlation is not all that high, but when considering the year range and the fact that all years are included, it is quite decent. Added is the latest GEFS PNA forecast. I will end with the "experiment" correlation of Oct-Nov solar flux, and Jan-Feb 10mb temperature. The 4 month lag did gave a slightly better correlation than no lag or lower lag. It is evident that the increased Oct-Nov solar flux does tend (emphasis on the tend) to promote SSW in general, with leaning more towards splits. But this correlation is generalised and unfiltered. It would require QBO filtering. I will contact NCEP and ask them about the possibility of filtering. Too bad I dont have the time for a longer post, but I was trying to make these correlations for some time now, but of course that wasn't possible due to the gov. shut-down. Luckily the sites are now available again and I have some more correlations in plan for the near future. p.s.: In case some of you are unfamiliar with the concept of correlations, or you dont know how to interpret these graphics, please tell me, and I will write a simple guide how to interpret these correlations. Best regards.

Oh snap. Cant believe that I forgot to address that. Of course that also got my attention, as soon as I made those composites a year and a half ago. After some research, I got down to a few points that I think are worth considering: 1.- Pre satellite era - data. The data in that period might be somewhat less reliable than after 1980 when the satellite era began. All the surface data gathered from land observation is accurate, so we can get quite accurate ideas about the patterns above or near the landmasses (proportional to the data available), especially when reconstructing patterns that correspond to to the classical configuration, like NAO, PNA, EPO, WPO, AO, negative and positive phases. So I have no doubt at all in the accuracy of the basic patterns. The problem are areas out in the middle of nowhere and tropics. There are ship and some buoy data, but it is slightly harder to accurately reconstruct the patterns without some specific configurations. And the areas that are unaffected or less affected by NAO, PNA for example. And of course because there are more drivers than just the PDO and AMO, there are other possible influences for the negative anomalies. Tho I still don't believe that such widespread deep negative anomalies would exist near or at the tropical belt. Which leads me to my second point. As you can see on the composites, with 1980 on, there are no more widespread negative or positive anomalies anomalies. The overall picture is much less noisy. 2.- Dataset errors. I remember when I was doing some reanalysis for the march pattern. I came across a few days in the 60' ( I think 65 and 62), that had dataset errors. Large widespread negative anomalies, going below -2000, with normal positive anomalies. If there is one or two days like this, it doesn't mean much, but when you have around 10 or 15, the anomalies can have significant influence on the overall picture. I also made a few composites with the ECMWF ERA reanalysis dataset, and surprisingly enough, there are some negative anomalies, but not like in the NCEP dataset. Climatology doesn't really have any effect. Anomalies are just departure of the mean from the norm. So regardless how you change the norm, the mean values are always the same. So the only thing you can change with the climatology, is the distribution of the blue and red colours. These are two main points to consider before even starting to look at linkage with other factors. I hope I answered your question. You did gave me something to think about, and I will look into it again, as soon as the USA federal sites get back online. These composites were originally made in march 2012 I think. There were some changes to the dataset since then. ---------------------------------------------------------------------------------------------------------------------------------------------------- To get back on topic. Good post by SK. Again, I really wish that the NOAA sites get back up a.s.a.p., and we can dig into reanalysis and data search again. When looking at those temperature charts, the idea seems to be there. So I am going to add the corresponding vertical mean cross-sections. And this year so far: So far, the 01/02 situation seems "close" to what we have now, but to be realistic, that warming event was basically useless, and not even a downweller (like the classic 81 and 91 events), which serves as a reality check in the great world of the stratosphere and cold shots. About the current situation. A powerful rossby wave (successively through the typhoon re-curve, as it was nicely pointed out just before) emerging in the troposphere, and having its implications all the way to the lower-mid stratosphere. And of course the corresponding wave1 activity we can see on the ECM charts. The issue I have with this, is that it leaves the main vortex slightly off, but it is still mainly intact and free to cool down and deepen. We are in the time of the year where the vortex get stronger by the day. This rossby wave will probably drop off soon after, giving the vortex some more free time to get its act together. Maybe some Eurasic shots after that? Well, in an interactive system like the BDC (refer to the great intro post by chionomaniac for more details), you better believe in its influence. Not to mention the solar role in the whole energy budget. And of course keeping in mind that short range on a climate level is not really the same as the short range on the "local weather" level. Best regards.

A great new topic, and so much material to work with. And the awesome intro post by chionomaniac. That composite speaks for itself, but you have to keep in mind that there is much more to those years than just the low sea ice, like the oceans. So if I could rephrase that sentence, I would say "The current AMO/PDO combination 500 hpa anomaly give us a massive tropospheric headstart". Of course among many other things, but keeping the main players in mind. Also realizing that the PDO and AMO are the "gatekeepers" to the Arctic. Too bad the sea ice data goes only back to 1980, because it would be interesting to see a correlation of these two cycles and the sea ice, for at least 100 years back. For example: Comparison of the last 3 great ocean cycle swings. 50-75= Cold PDO / Warm AMO 80-98= Warm PDO / Cold AMO 99-12= Cold PDO / Warm AMO (as 50-75) That would be all for now. Best regards.

Its been a while and I have nothing but good memories on this topic from last season. Cant wait for the new debates to really kick off in the new thread. Ok, down to business. As I said, its been a while, so I am a bit rusty in this department (especially at the MT and FT , but I was rusty at this last season too) but I will still give it a shot. And I will try to make it a quick one while at it. Those are some legit points given, about the current forecasts and the state of the Polar vortex. Till this point, it was all more or less normal. Someone said, that there must be something moving up. Given the GPH time series, something does look like it is moving up. Latest ECM does have some nice wave1 activity scheduled. Now looking at the troposphere. The positive GPH anomaly on the time series above can be seen on the maps, with decent ridging near the polar regions. Going further in, the ridging really increases around the polar region from the Pacific/W Asia regions, so I wouldn't say I am really all that surprised that there is wave1 activity forecasted. I have made an overlay of wave 1 and GPH anomaly, where both the positive anomaly and later wave 1 nicely coincide on late Sep., early Oct. And with new strong ridging forecasted in the Pacific/W Asia region, I would be surprised if there would be little or no wave1 activity. Keeping in mind that these might not be the typical early/mid-winter dynamics, since we are not in early/mid winter, and we will see how the "teenage" polar vortex will react. Especially interesting is GEFS when going in 240h and beyond. These are basically the same features that we can see on the operational run, reaching from the upper trop. into the mid. strat. And Interitus beat me to the fact, in a fraction of the time it took me to write this. Just a notice: I have made quite a few analysis of the model skill scores for the stratosphere last year. And I have to point out that even tho the strat. forecasts have a much higher skill score in the FI than the tropospheric forecasts (especially when you have a calm/uninterrupted strat), you have to realise that when it comes to strat-trop "coupling" with wave breaking and ridging and so on, the skill scores drop off slightly, and you can get quite some variance in the FI for the stratosphere. Especially now when the polar vortex is not at its max. yet, and the results and effects of wave breaking at this period in time might be somewhat more unreliable that later in the season with an established low and enough "skill" from past events. Best regards.