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Catacol

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  1. Genuine musing as posters in another place get increasingly frenzied at the lack of -NAO and the resilience of a troughing pattern coming east out of Canada that is either preventing the formation of Greenland blocking or benefitting from the failure of the blocking signal to translate into any action. Mid atlantic ridge just sitting tight as it has approximately for a long time now. A lot of evidence continues to point to a -AO on the back of the SSW downwell and a high amp pattern that should see pressure rise somewhere in the greeny to scandy corridor.....but I'm just beginning to wonder if the constant pushing back of the beginning of this pattern is telling us something we should be listening to. i'm out of my knowledge base in explaining it as so far this winter every moment of expected amplification after November has ended up with a limp product, and while Europe now slips under the influence of a trough that is setting up a long way south, implying strong amplification, the accompanying ridge just doesn't want to bounce. Any thoughts here would be useful. I popped out a few twitter messages yesterday to some of the main US weather gurus and got a reply from one saying effectively all good - no change... - NAO on the way. But assertion isn't argument and the silence is beginning to become deafening in some quarters as to just what is making a -NAO signature so very difficult to achieve in the recent past. Without digging out the stats the number of -NAO months in recent months has been extremely small. Anyone got thoughts?
  2. Really good and interesting post Tamara - enjoyed it very much. I've cut and pasted some bits by way of some follow up discussion - I'd value your thoughts... 1. Timing. Agree 100% that timing has been an issue this season so far - with signals in place and being pushed back. And not for the first time to be honest - in previous years we have seen timings pushed back and processes slowed. The only exception I can think of immediately would be the very swift end to the "Beast" of March this year where extraordinary processes led to such a swift retrogression of the block that warm air undercut our late winter UK cold much faster than anyone, including the Met, predicted. Ignoring that example as an example of really unusual conditions is there any thought as to why timescales tend to run longer than expected, and why NWP is often too progressive with signal reading? Is this just a bias we need to absorb, or are there physical processes within GSDM modelling that arise frequently to jam the spanner into the wheel? I'm happy to accept bias if that is all it is....but wondered if you have any insight into the physical processes going on. 2. Paras 2 and 6. I also see a disconnect in terms of sub tropical mid latitude ridges - but am also very aware of higher than expected GLAAM readings for the season as a whole so far - and have posted about this before. Given what you neatly describe as a "pre-amplified pattern" what is your reading of the impact of this pre-amplification....and do you think it has any impact on the apparent mid lat disconnect we are seeing? Has pre loading of the atmospheric AAM served to boost the Hadley Cell by impacting significantly just north of 30N? I cant quite conceptualise the overall impact of this pre amplification - and being a visual learner of less than average scientific knowledge but quite sharp visual/conceptual understanding I need to get a handle on a process before I can interpret it! 3. NOAA have posted that the MJO slowed down as it interacted with rossby wave activity - relates to para 3. I'm struggling here. I thought that MJO activity initiated much of rossby activity in the first place....but their pdf post recently suggests they are mutually exclusive and this activity has interfered with the forecast. From where does rossby activity originate if not from MJO passage - and why would it slow progress down? Just more model bias?? 4. Parallels with 2013 are really interesting. Funnily enough I was just running this site linked to me by Singularity that shows the 2013 split...and thinking that it looks much like the one we have coming. Very similar around Jan 9 http://birner.atmos.colostate.edu/SSW-animations/anim-PV/2012-2013_530K/loop.html - and the same wQBO label too for that year. Sebastiaan over on Netweather has noted that the majority of split vortex events in wQBO years tend not to downwell. In 2013, however, we got the downwell. Or....was it actually more of a tropospheric "sandwich" - with upwelling impacts caused by the 5 - 8 GWO orbit impacting on the trop which was simultaneously being harangued from above...and ultimately is the success of any downwelling SSW all about timing between strat and pacific? Which puts us back, once again to timing. My current bugbear. My own thoughts for this season have panned out not too bad - but timing is a problem. I notice you also referenced my little pet issue of "seasonal wavelengths" - a topic I've asked several people about on more than one occasion and never had a concise and punchy answer as to what these wavelength transitions/processes are and why. If you have guidance there I'd be glad of it. Keep up the great work - very thought provoking.
  3. It's only 12th December and there is a way to go on this one yet. I don't have all the archive data - how many times (if ever?) has a wave 1 warming attack done enough to shatter the vortex? The flux charts posted by Amy Butler tonight certainly suggest a high level of heat about to strike at this already weakening vortex....but is a wave 2 setup a necessary precursor to destruction? Maybe early January. I've seen that suggested by Chio...
  4. Big question for me is whether we can get a second bout of wave 2 impact. A split is certainly better for overall winter synoptics than a displacement - and current extended modelling isn't picking up further wave 2 potential. Will the Siberian one sided punch be enough to take this weakened vortex down? Or do we end up with a very stretched and distressed vortex over the atlantic, but still intact? Big difference in tropospheric impacts down the line....
  5. Sorry for the slow reply Matt - was hoping we'd get some updated files from GSDM to show what I think is about to happen vv 30N and 60N - but in essence: yes.... when there is a jet surge at 30N AAN has to balance itself out and there is a consequent fall in AAM up towards 60N. If you look right across that chart you posted the oranges are almost always balanced by greens and purples to the north - that balancing of the AAM budget. Right now we are seeing the jet extend and when we get our next GSDM update I'm pretty sure we will see an ongoing increase in MT at 30N. This will almost certainly be matched with a decrease at 60N. The increased resilience of the Scandy High in the next few days maybe more than just hocus pocus and natural "resistance" of the block - the atlantic is gradually having the rug pulled from under it...
  6. JMA MJO composites here.... easy to use. http://ds.data.jma.go.jp/tcc/tcc/products/clisys/mjo/composite.html
  7. Hehe - that's as close to a winter ramp style post as I've seen from you Tamara... Eyes firmly fixed on mountain torque to start - looks to me like the forthcoming spike in AAM driven my MT could be quite steep judging by forecast pressure anomalies over Rockies/Himalayas. GSDM from there fairly predictable as you point out. The tricky bit is knowing how the vortex shake down is going to look. Much harder at the moment to get a handle on this into January. On its knees it may be - but whether it splits or not will be important as to specific weather patterns to follow.
  8. We will wait and see whether the high declines significantly - I suspect NWP might be a bit over progressive, but given that we wont see the impact of the next frictonal/mountain torque cycle hit until after the 15th (probably more like the 18th I reckon) then a waning of some kind was always likely. Progression of the MJO back through the IO is going to be important, particularly if the magnitude of that signal is as significant as some data is suggesting. It will provide the extra oomph on top of a NH pattern still predisposed to potential blocking thanks to the ongoing impact of GLAAM to maintain high lat blocking longer term. Superimposed on top of the long term impacts of the SH/AL combination and the end of December into January looks very interesting. The rate of decline in relative AAM has certainly been steep in recent days. To be honest though it probably had to be. AAM had reached such significantly high levels that they could not be sustained - and like an elastic band stretched hard the ping back has been strong. Relative momentum between earth and atmosphere constantly tries to equalise, and when momentum at 30N falls away sharply it has the impact of increasing momentum via poleward momentum transport at 55/60N. So - we see some extra energy in the atlantic now precisely because the drop back at 30N has been so steep. At least that is my understanding of one of the complex mechanisms at work here. Likewise - when torque is fully reengaged according to fairly predictable cycles we will see a rise in momentum at 30N and consequently less of an atmospheric signal across the north atlantic for a trough aimed straight at the UK. The atmosphere will once again be predisposed to a more meridional look and blocking returning. See also MJO signal reemerging on top. And if that torque includes an east asian element which looks likely, then the extension of the pacific jet serves to force eddies both equatorward and poleward as it passes through, also helping to reinforce that meridional effect and possibly introduce a signal for retrogression (never read that....but it is my interpretation.) So - to conclude. And this is purely my own take on it, and not grounded in extensive knowledge of atmospheric physics because I am not a physicist. GLAAM was high and under lowering pacific wave and lowering torques has pinged back, noticeably at 30N. This has injected energy at 55/60N while torques remain low and the next pacific wave reforms. So - the Scandy High will come under pressure, though it may hang around long enough to benefit from the next torque cycle that has already begun in terms of frictionals, and will soon see mountain elements emerge. Cue extension of pacific jet forcing with accompanying eddies, and cue also a fall in momentum at 55/60 which will promote less of a westerly pattern. So - sometime around 18-20 Dec a blocking signal strengthens once again. Reemergence of the next pacific wave will reenergise the nature of that pattern and further reinforce blocks in place. Impacts of any vortex disintegration then to sit on top of this in the New Year - but that is too far ahead to get my small brain around. Where might blocking sit? This is my own area of greatest frustration, because I struggle to conceptualise the process. Others are wrapped in data and composites - I need to visualise a process to understand it. I have asked questions about the impact of various patterns on the exact position of the wave pattern and never received an answer that has made my puzzlement go away. I have read of "seasonal wavelengths" - but again never had a clear answer to what that means. So - my best guess would be a reemergence of a Scandy high with a signal for retrogression if we get the jet extension - but none of this is grounded in any certainty because I cannot get a clear visual model in my head. It could quite easily by a mid atlantic high on that basis, or maybe a UK high. But my gut, and best sense of where the pattern will sit when torques reengage, says Scandy once again. I am an enthusiastic amateur and not a qualified Met like you - so please take my analysis as both potentially imperfect and certainly not intended to be anything close to patronising!!
  9. That looks about right to me. MT peak in around 10 days time will be interesting to gauge - in the context of global pressure patterns a strong spike could potentially be the beginning of a multicausal process that witnesses vortex destruction in early to mid January. Timing this year could not be better.
  10. Given that FT started to rise about 5 days ago I'm expecting MT to follow mid month and not later. It seems to me on his tweet that Masiello is simply reading the pressure anomalies, with positive anomalies forming around all 3 major mountain ranges at around the same time and creating the spike in torque. Reading those forecast anomalies, unless the forecast proves wildly incorrect, I'm not sure how his interpretation can go awry. Which leads me back to where my musing on all this started. Given that Glaam remains high - how can we have another interaction of torques and another predicted rise in tendency? Given that we are still above +2SD in total momentum it seems bizarre to me that we have not experienced a fall in momentum, but have instead witnessed a best fit line that has projected upwards consistently. This in the context of a Nino that is not huge. But as Zac says - it may not be intense but it is a widespread phenomenon that reaches north as well as a long way west. And the Siberian High Aleutian Low combo is allowing all that energy to be channelled onto a destructive path for the winter vortex. It's a fascinating season beginning to unravel. The timing of Nino's arrival in early autumn on the back of a Nina that had maintained broad control for around 2 years and a transitioning E to W QBO last month, may prove in the end to be of critical significance in how this season progresses. The timeline context of every event is surely as important as the snapshot blueprint of that event itself.
  11. Catacol

    Catacol

  12. Some really interesting reading - thank you. I'm still scratching my head a bit in terms of the size of the AAM surge over several months, and the consequent compensation reaction to higher levels of momentum is underway and more punchy than might have been the case had Glaam remained in moderate bounds. Will the spiral of upwards momentum be sustained and pushed to equally high levels in December as the strong MJO signal reconnects with phase 5/6? The ventrice site continues to show as strong an MJO progression out to week 2 that I can remember seeing in recent winters and with potent early season wave 1 activity ongoing and set to hit a good and sustained peak as Tamara stated - there are interesting times ahead for the vortex as we head towards the heart of winter.
  13. Yep - accepted and agreed. Monthly average not the same as a short term peak. However the climb up to +3SD is still a surprise given ENSO context, at least to me.
  14. A really good post I think Tamara - and this bit in particular highlights well how we need to think carefully about the actual profile of the Nino/Nina in operation. I think last winter taught us much about this. I'm musing now - but Total AAM is high - in fact it is very high. If we look at the long range picture going back many years we are looking at an event that smacks of top 5. There would seem to be a link in the graph above to previously strong Nino years for spikes at +3SD - but this year we are in low Nino territory at the moment but experiencing a significant uptick in Glaam. Taking the year as a whole the best fit gradient since the summer is clear: Our current MJO forecast is strong too - and I'm sure I've read somewhere that in a Nino event the strength of the MJO tends to fall in winter. No sign of that yet. Anyone got any theories as to why we are seeing such a strong development in Glaam over many months? Given that we appear to be looking at a more west based than east based Nino at the moment, the analysis you put forward here would suggest a pattern more conducive to blocking in the atlantic with an almost Nina-esque feel to the wave pattern....but where in all this does the Glaam total fit? From a position of +3SD one would assume there has to be a response that will force it down....but this seems to run counter to the MJO setup at present, which in itself seems higher than we would expect? (or am I off beam here....?) I guess in simple terms I'm just wondering what has created such a dynamic upwards trend in glaam, and just what this is likely to mean given the ENSO profile this winter season. I had not expected to see it climb so high.
  15. Thanks - got the Attard links already...but for some reason had not spotted the cpc archive. That's useful - thanks. I like the complete shape from top to bottom. A single horizontal cross section doesn't quite do the business....
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