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Bring Back 1962-63

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  1. Bring Back 1962-63

    [Global] Teleconnections: A Technical Discussion

    At last we have what we've been predicting - a poleward surge in +ve AAM. Another important piece in the jigsaw for Arctic blocking: The relative GLAAM tendency anomaly has spiked upwards and looks set to reach its highest level of the winter. Global MT is surging upwards and both NAMT and EAMT are strongly +ve too. The GWO has already looped back into phase 5 and is set to go into a much higher orbit through phases 5, 6 and 7. This is the strong tropical forcing that we've been saying is needed to assist the down welling in the stratosphere. So far, I believe that the models have just begun to sniff out the SSW surface impacts. They usually struggle to pick up on the tropical forcing. So we go from a pretty destructive phase into a really constructive one. In the mid term (say day 10 onwards but perhaps sooner and remember that these charts have a 2 day output time lag) this should hugely assist with the HLB patterns. I would expect the models to start picking up on this over the next few days but with various blocking outcomes and solutions. A CAUTIONARY NOTE: We still need to monitor how the jet stream phasing in the Pacific behaves and this has impacts on the US storm system(s) and a knock on down stream in the Atlantic. This may or not not be favourable in the short term but given the prolonged SSW event, the strength of the MT spikes and poleward momentum the opportunity is likely to persist for many days (or weeks). Continued exciting model watching for the rest of this month and beyond. No more time this week. David
  2. Bring Back 1962-63

    [Eastern US] Jan. 2019 Pattern & Forecast Discussion

    Hi Zac, this is a truly outstanding post which is an early nomination for "post of the year". Although based on the teleconnections (as it should be) you've presented it in such a clear way, that many readers will be able to understand it. The forces which are producing this major pattern change across the middle and higher latitudes are exceptional. The models are still coming to terms with this SSW and it's impacts. Assuming that the downward propagation through the troposphere continues to the surface, this should provide even greater displacement of the Arctic surface cold to you guys and in Eurasia too (which should include the UK). Even without a full wind reversal down welling (full surface impacts seem inevitable now), the strat is starting to imprint on the trop patterns and widespread significant cold looks likely to dominate for quite a few weeks. IMHO the main building blocks are very much in place and it's the finer detail which will evolve during the next week or so which the models are still toying with. ECM (and the UKMO) do seem to be getting there now. When the other teleconnections (AAM, the torques, the MJO and renewed modest Nino-like forcing come into play again around the turn of the month and into early Feb, they only need to produce modest impacts to really constructively assist with a continuation of the SSW dominated set up. What an absolutely fascinating period for all weather enthusiasts. David
  3. Bring Back 1962-63

    [Eastern US] Jan. 2019 Pattern & Forecast Discussion

    A FEW COMMENTS ON THE GREAT LOOKING POTENTIAL FOR CONUS AND UK/EURO COLD Hi everyone, I rarely come onto this thread as I normally post on the Teleconnections thread and occasionally on the Stratosphere thread. This will not be one of my long in depth reports with loads of charts (I have little time for that now anyway) but I wanted to make a few comments. One thing that we know is that many weather forums are far busier during the winter and the majority of members are looking for cold and snowy conditions to prevail. Most of us who analyse the background signals and the teleconnections are also snow lovers but we try to tell it as it is and endeavour not to allow our emotions to overly influence the points that we are making. I'm from the UK, where we often miss out on snow in our marginal climate adjacent to the Atlantic and a major continent. Much of central and eastern Europe is currently seeing it's heaviest snowfalls for 30 years. Some spots at only moderate altitude have seen well over 1 m (3 feet) of the white stuff this week with 2 m to even 3 m in the mountains of southern Germany and Austria. Almost as much again is forecast for the next few days. Malcolm @Blessed Weather (another "33" UK member is currently on a skiing holiday in Bavaria (on the German/Austrian border) and he's snowed in there - far too much for skiing but he's having a wonderful time anyway and he'll post some pics on this forum in due course. Here's one pic that he took yesterday during a brief break in the snowfalls - just to get us all in the mood: Back in the UK, like you guys we're still waiting for the real cold to arrive. We need even more patience than you do across the pond and we have to be used to many disappointments and near misses. On the UK forum that I'm also a member of, the emotions runs even higher than they do on "33". I must say that I'm so pleasantly surprised that there is generally a far higher level of respect shown on here compared to back in the UK. I do, however, feel that Tom @Isotherm (amongst several others) has seen a few rather unfair comments. He has been trying to point out what can go wrong, although he remains very upbeat about the rest of the winter. I agree with him and feel that both the eastern/central CONUS (and eastern Canada) and western Europe (including the UK) are "likely" to see prolonged periods of very cold conditions starting to dominate from late January and through much of February (precise timing subject to some variation). We have been studying the stratosphere and the troposphere and looking at all the key teleconnections throughout the year especially during the fall and the run in to winter. The stratosphere looked like delivering an SSW this winter and these signs grew stronger from late November with possible triggering of a major event from late December into early January. As we know this actually happened with a displaced SPV (stratospheric polar vortex) between Xmas and the New Year and just a few days later with a fully split SPV - in fact a really impressive event indeed. No two SSWs are alike. Sometimes the "wind reversals" never reach the surface, sometimes they are delayed and sometimes they propagate down very quickly. Much depends on other factors and the key teleconnections. This is not the thread to go into any detail but we need to consider the ENSO state (a very weak and still struggling to move into full El Nino conditions - may not get there until the spring now but probably still enough "nino" like conditions overall to be favourable), angular momentum and the torques (were playing ball and likely will again in early-mid Feb) , the MJO (was in favourable phases for high latitude blocking and looks set to quickly return to those phases in early Feb too albeit at weaker amplitude), all this impacts on the critical amount of tropical forcing, the QBO (recently changed to west based - on its own not so favourable) and the solar cycle (getting close to a roughly 11 year minimum = very favourable). The consensus in our Teleconnections PM group was that we looked set for colder than normal patterns for large parts of this winter even without a major SSW. Indeed Tom's winter forecast picked up on this. What we have seen for a while was a disconnect between the strat and the trop and some of the favourable tropical forcing "was" initially being somewhat cancelled out by the strat warming (in the build up to the SSW). This is called acting "destructively". Things, however, now look like they are really falling into place and we should see some of the key teleconnections and the SSW impacts acting much more "constructively" later this month and even more so in February. With all this going on, we know that the models really struggle with both sniffing out these major broad scale pattern changes and the timing of any impacts. Our strat specialists are seeing signs of the "wind reversal" down welling through the troposphere. It looks like surface impacts will be seen in the high Arctic (close to the pole) within the next 7 to 10 days (again precise timing cannot be certain and there might be several more days delay but there is increasing confidence of this now which is starting to show up in some of the model op runs and certainly a good number of ensemble members are showing this evolution. The next question is exactly where will the impacts be felt first, how will they develop, how will they spread, how cold will it get and how long will it last? With split SPVs, surface impacts are usually much more widespread. The Arctic cold is pushed out towards the middle latitudes, Much depends on the strat/trop imprint and the tropical forcing processes that I outlined but this is looking like a really strong SSW impact which will be the dominant factor for some weeks. Sometimes North Am sees the impacts first but more often with splits Eurasia see them first. The Feb/Mar 2018 SSW impacted Siberia and then the blocking patterns spread westwards through Europe and across the pond reaching you guys about 10 days later. Then there was a secondary warming with a similar response. You ended up with repeated cold periods in March and into April. The models are starting to indicate more of an initial impact on our side of the pond with you guys seeing the main changes some days later. In the interim, both you and western Europe are likely to see some colder shots anyway. I'm not going to discuss your winter storm prospects or ours and how much snow any of us will see. Let's just say that there is some wonderful "potential" for the next 6 weeks (or even longer). Of course there's a small chance that things can still go pear shaped (slightly more likely for me in the far south west of England but less likely for the eastern UK, much of Europe and of course eastern CONUS) but I would be very surprised if we do not see at least some decent cold spells with snow pretty likely. We are in the middle of a truly fascinating transition with so much to look forward to. Let's all be patient and watch the evolution from now on and particularly during the latter part of January onwards. David
  4. Bring Back 1962-63

    [Global] Teleconnections: A Technical Discussion

    MUCH MORE ON AAM I'm really busy for the next few days and then have my annual business accounts to complete - so no time to review particular AAM papers now but here's the list of titles to papers and presentations already in the portal under the AAM heading (you can click on any title): Atmospheric Angular Momentum (AAM): A gentle stroll through EP (Eliassen & Palm) flux theory An Essay on the General Circulation of the Earth's Atmosphere (1947) Angular momentum in the global atmospheric circulation A Synoptic–Dynamic Model of Subseasonal Atmospheric Variability Atmospheric Dynamics Feedback: Concept, Simulations, and Climate Implications Atmospheric forcing mechanisms of polar motion Atmospheric torques and Earth’s rotation: what drove the millisecond-level length-of-day response to the 2015–2016 El Niño? Axial Angular Momentum: Vertical Fluxes and Response to Torques Centennial Trend and Decadal-to-Interdecadal Variability of Atmospheric Angular Momentum in CMIP3 and CMIP5 Simulations Dynamic coupling of the stratosphere with the troposphere and sudden stratospheric warmings Gravity wave refraction by three-dimensionally varying winds and the global transport of angular momentum Isentropic Pressure and Mountain Torques Latitude–Height Structure of the Atmospheric Angular Momentum Cycle Associated with the Madden–Julian Oscillation Mountains, the Global Frictional Torque, and the Circulation over the Pacific–North American Region Mountain torques and atmospheric oscillations Mountain Torques and Northern Hemisphere Low-Frequency Variability. Part I: Hemispheric Aspects Mountain Torques and Northern Hemisphere Low-Frequency Variability.Part II: Regional Aspects Planetary‐scale wave activity as a source of varying tropospheric response to stratospheric sudden warming events: A case study Regional Sources of Mountain Torque Variability and High-Frequency Fluctuations in Atmospheric Angular Momentum Relationship between Tropical Pacific SST and global atmospheric angular momentum in coupled models Relation between variations in the intensity of the zonal circulation of the atmosphere and the displacements of the semi-permanent centers of action Response of the Zonal Mean Atmospheric Circulation to El Niño versus Global Warming Stochastic and oscillatory forcing of global atmospheric angular momentum Studies of atmospheric angular momentum The Angular Momentum Budget of the Transformed Eulerian Mean Equations The atmospheric angular momentum cycle during the tropical Madden-Julian Oscillation The Dynamics of Intraseasonal Atmospheric Angular Momentum Oscillations The Effects of Mountains on the General Circulation of the Atmosphere as Identified by Numerical Experiments The intraseasonal atmospheric angular momentum associated with MJO convective initiations The layer of frictional influence in wind and ocean currents [1935] The remote effect of the Tibetan Plateau on downstream flow in early summer The Role of Mountains in the Angular Momentum Balance of the Atmosphere The tropical Madden-Julian oscillation and the global wind oscillation Topographic Instability: Tests Tornado Frequency in the United States Related to Global Relative Angular Momentum Torques and the Related Meridional and Vertical Fluxes of Axial Angular Momentum Uncertainty analysis of atmospheric friction torque on the solid Earth Unusual Behavior in Atmospheric Angular Momentum during the 1965 and 1972 El Niños What is the GSDM and how does it help with subseasonal weather forecasts? (A YouTube Presentation) Where is ENSO stress balanced? Some of these papers are entirely about AAM while others are make considerable reference to it amongst other related teleconnections. What we deliberately designed the Research Portal for was to enable visitors to skim through papers quickly by providing links to the abstract. Once anyone reads the abstract they can decide if they wish to look at the full paper (or view the presentation) itself with a direct link provided under the abstract. When I read papers, I initially look at the introduction and then the conclusions. If I feel that I want to learn more and especially if I wish to review a paper in one of my posts, then I delve into it much more deeply. I've learnt a lot more by reviewing papers and presentations as I have to get my head around the main points in order to comment on them meaningfully (hopefully ). I could never understand the maths and all the equations but focus on the text. There are always some bits that one can understand even in the more complex papers. One cannot learn much about AAM without understanding the GWO (global wind oscillation) which is referenced in many posts on this thread. There is a specific GWO heading in the portal index. In fact, check out all these headings (shown in alphabetical order): Brewer-Dobson Circulation East Asian Mountain Torque Frictional Torque Global Wind oscillation Global Synoptic Dynamic Model (more on this below) Mountain Torque North American Mountain Torque Planetary Waves Rossby Waves (similar to above) That's just a handful of topics directly related to AAM - there are many others. Here's a link to the full comprehensive index: INDEX TO PAPERS Unlike many meteorological topics there are no really simple guides available to AAM as it's such an extensive and pretty complex topic (it would be good if somebody wrote one!). A great place to start is with a brilliant YouTube presentation by Ed Berry all about the GSDM (global synoptic dynamic model) which I posted a review and summary on last May. Here's the link to that post https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=87746 . That reminds me, I've been working on an index to this thread which appears at the top of each page. I've got up to September but still have a lot of work to do in the coming months to bring it right up-to-date. There are some good earlier posts on here to explore. This index heading contains posts with significant references to the GSDM including my review on May 24th: Edward K Berry (Ed) and Dr Klaus Weickmann (devised the GSDM and the GWO and pioneers in the application of AAM and the torques) March 26th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83549 @Snowy Hibbo May 24th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=87746 @Bring Back 1962-63 July 1st 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=88574 @Bring Back 1962-63 July 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=89707 @Isotherm July 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=89714 @Bring Back 1962-63 Here's a list (below) of the posts with a focus on AAM. I highly recommend those from March and April when Zac @Snowy Hibbo, Tams @Tamara, Malcolm @Blessed Weather and myself were getting this thread off the ground with some posts introducing the subject and generally aimed at learners. I produced a long post entitled: UNDERSTANDING THE BASICS ABOUT ATMOSPHERIC ANGULAR MOMENTUM FROM A LEARNER’S PERSPECTIVE. I wrote it for early learners and go though how and why I wanted to understand this vitally important subject. Here's the link: https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83979 It does have several small errors in it but it does provide a comprehensive beginner's guide to the processes involved. It's the March 30th entry in the list below. Do check out the posts from the others too who have greater AAM knowledge than I do (especially back then): Atmospheric Angular Momentum (AAM) and Global Atmospheric Angular Momentum (GLAAM) March 26th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83549 @Snowy Hibbo March 26th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83567 @Bring Back 1962-63 March 26th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83568 @Tamara March 27th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83666 @Blessed Weather March 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83745 @Snowy Hibbo March 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83753 @Tamara March 30th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83979 @Bring Back 1962-63 April 17th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=86401 @Blessed Weather April 22nd 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=86675 @Bring Back 1962-63 May 24th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=87746 @Bring Back 1962-63 June 2nd 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=87925 @Snowy Hibbo June 3rd 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=87946 @Bring Back 1962-63 July 1st 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=88574 @Bring Back 1962-63 July 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=89707 @Isotherm July 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=89714 @Bring Back 1962-63 August 31st 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=91074 @Snowy Hibbo September 15th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=95282 @Snowy Hibbo September 15th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=95305 @Tamara Overall, this thread and the Research Portal already contain a vast amount of teleconnection information with plenty on AAM and the torques - all available on this great forum. I have nearly 1,000 more papers saved in my store ready to upload during the course of this year. The numbers grow more quickly than I can find the time to write the portal entries! Malcolm, Zac and myself are the portal administrators but if anyone would like to help us build it up we would really appreciate the extra help. Please PM any of us about this. David
  5. Bring Back 1962-63

    [Global] Teleconnections: A Technical Discussion

    An outstanding post Zac with a really clear and comprehensive explanation of the AAM processes which are difficult to understand and something that I'm still in the middle learning stages of myself after 2 years of trying to get my head around it. Geoff @33andrain - please can you make Zac's post a "recommended post" and leave it there at the top of the Teleconnections thread page for a few weeks. Not only will readers learn from this but it will help to refer to it when any of us post AAM and torque charts while the SSW impacts unfold during the next 2 to 8 weeks. David
  6. Bring Back 1962-63

    [Global] Stratospheric Discussion and Forecasting

    LOOKING FOR SSW SURFACE IMPACTS NEAR THE POLE IN THE MODEL OUTPUT - COMPARISONS TO EARLIER EVENTS - PART 2: 2013 I'm writing this post for two weather forums (US and UK) but most of it is relevant to both N America and UK/Europe. I will be mainly drawing on charts produced by Meteoceil and these + archived charts from the NCEP reanalysis show the Northern Hemisphere from the UK perspective. Abbreviations used in this post: SSW - Sudden Stratospheric Warming SPV - Stratospheric Polar Vortex TPV - Troposheric Polar Vortex HLB - High Latitude Blocking QBO - Quasi Biennial Oscillation MJO - Madden-Julian Oscillation COD - Circle Of Death GSDM - Global Synoptic Dynamic Model GWO - Global Wind oscillation GLAAM - Global Atmospheric Angular Momentum FT - Frictional Torque MT - Mountain Torque EAMT - East Asian Mountain Torque NAMT - North American Mountain Torque What I want to examine are the surface pressure patterns and charts in relation to previous SSWs and to show what to look out for in the current output. My focus will be for signs of the reversal propagating down to the surface in the high Arctic and close to the North Pole. I will look at charts around the time each main SSW event started, at the time of the specific types developed (ie: the displacement and/or the split), the time that surface impacts were beginning to show up and one or more later chart(s) to see how blocking patterns fell into place. I am dividing this post into at least 3 parts over several days to cover separate SSW events. In part 1, I looked at the current set up and then the February 2018 SSW (direct link to that post: https://www.33andrain.com/topic/750-stratospheric-discussion-and-forecasting/?do=findComment&comment=115201. In this post (part 2) I'll focus on the 2013 SSW and in part 3, the 2009 SSW. Later on, I may move on to several earlier events - time permitting. I note a request from @Weathergeek wrt to the 1984/5 SSW. While there is no GLAAM, torque or MJO data available for back then, I can show the reanalysis charts for that "split" SPV event - I'll do a separate short post on it (next week) once I've completed this (and perhaps part 3) over this weekend. 2012/2013 SSW: SSW started in late December 2012; Rapid warming occurred between December 28th, 2012 and January 10th, 2013; 10hPa wind reversal on January 6th 2013; Type - Displaced SPV January 6th, 2013 and Split from January 8th; Ended February 8th, 2013; longest SSW on record (38 to 42 days depending on which analysis you read) in the modern "satellite" era (since 1979). MJO - phases 4 and 5 at increasing amp at the time of SSW, then on to phases 6 and 7 at moderate to high amp later in January; ENSO - neutral with perhaps slightly La Nina like tendency (see table below); wQBO (descending); solar cycle - closer to maximum (reached in April 2014 but the weakest since 1902) . The 2012/13 SSW was an unusual and fascinating SSW with both displaced and split SPVs. This is probably only the third (possibly fourth) time that this has occurred since at least 1978 (in the modern satellite era). Depending on which reports one reads the previous years were 1985/86 (some contention on the displacement but ended up as a split event), 1987/88 (split, then displaced with a further warming and another split two months later) and 2001/02 (displaced and perhaps a split later on). the 2012/13 event with combined wave 1 and wave 2 attacks leading to the displaced then split SPV events was the longest since at least 1978 lasting 38 to 42 days. With such a long event, the impacts lasted at intervals right through to mid April with repeated bouts of HLB and cold spilling out of the Arctic. You can see that ENSO was slightly on the -ve side of neutral throughout the period but not strong enough to be defined as a La Nina episode. This table (up to 2013) shows the phase state of the MJO at the time of the "start" of major SSW events. Although the MJO can have an influence at that stage, we also need to see to what extent it might have assisted during the impact period. From the archives, we can see that the MJO was actually still in phase 4 at the time of the initial SSW event and then progressed through the phases from 5 to 8 at moderate to quite high amp. ignore the green "forecast" period. I pick it up from mid February. Although the amp was much lower in phase 1 it never entered the COD and then managed another complete orbit at low to moderate amp. it reached phases 6, 7, 8 and 1 at slower reducing amp between Feb 25th and March 21st. The briefly slightly stronger amp in phases 6 and 7 (allowing for the time lagged impacts) was probably at least partly assisting renewed blocking through mid to late match (see model charts further below). It's a difficult exercise obtaining GLAAM and torque data from the archives. NOAA closed their map room in 2015/6 for this when Dr Klauis Weickmann and Ed Berry (who developed the GSDM and GWO) left. Ed berry (whom I'm in touch with by email) says that it's a time consuming (and therefore costly) exercise to reprocess the raw data (which is still available) to reproduce the archive charts again. I've been through countless papers, presentations and archived forum posts to find some earlier charts and have been building up a store of some of the key data. Unfortunately many charts no longer show in early posts and many charts that do show up were copied across with the (copy image address option" and these charts "auto update. I found a 2009 post with a current GLAAM chart showing! I save all of these type of charts to a file which freezes the image and date. if anyone has access to a good range of archived AAM and torque charts (and also GWD - gravity wave drag charts for my 2019 focus research project) from 2005 to 2016, please let me know. I (and the specialists in this field) would really appreciate having a permanent and complete record of all archived charts. Unfortunately, I could not find any torque charts for January to April 2013 but I do have enough useful data in my store to piece the GLAAM and torque position together. This MT chart is up to Dec 24th 2012 and shows a huge spike in global MT (black line) to an extremely +ve position and still rising at the end. NAMT (blue) was +ve but falling back and EAMT (red) is rising strongly and looking set to go into a strongly +ve phase. Given the 10 to 14 days (or so) time lag, it would look that once again, EAMT played a significant role in helping to trigger the SSW. As usual and fully consistent with the latest research (and the papers that I've read) the deeper red blobs in the upper part of the chart are between 35N and 50N and show us that the strongest MT was around the Tibetan Plateau and particularly the Mongolian Mountains. The area which generates the greatest uplift in the world with vertically propagating planetary waves and (gravity waves too through gravity wave drag). Remember that we should consider that this is still "theory" but I've been gathering more and more evidence to support that theory. We can see that relative AAM spiked just after mid January and that "may" well have led to another spike in the torques later in January and into early February. This table shows GLAAM averaged out for each calendar month from 1958 to 2014. December 2012 was +ve, January 2013 was neutral (as we can see the mid month spike was cancelled out but -ve momentum earlier and later), then Febraury to April 2013 all averaged out broadly +ve but not particularly strongly. That's confirmed by the chart above. That longer period of +ve GLAAM would have been strongly supportive of the repeated HLB patterns and may well have been the main factor in keeping the troposphere in its generally -ve AO and -ve NAO state for many weeks beyond the end of the SSW itself. Now on to what some of you have been waiting for - the archived model charts. I will not comment on these other than to say that you'll see repeated periods of HLB with some lulls. Here's the link so that you can go through the whole period: http://www.meteociel.fr/modeles/archives/archives.php?day=1&month=1&hour=0&year=2013&map=4&region=&mode=2&type=ncep Finally a word of caution wrt to the current event. No two SSWs are the same and even similar type of events can have very different impacts. There remains uncertainty on the timing issues but it seems that we can all take comfort in a long SSW event which may, like 2013 (which has both similarities but many difference too) see several GLAAM, torque and MJO cycles creating repeated opportunities. I do not know how patient we'll need to be but perhaps you can see why the models always struggle with these episodes - there is such a complex interaction of the strat, the trop. and all the teleconnections. I remain very confident of some prolonged cold or very cold weather but no one right now can nail down the timing of the impacts. GLMT and EAMT are still +ve but less so and their time lagged benefits (+ the MJO still in phase 7 and on to 8 for a while longer) should last through to around Jan 20th or longer. Part 3 on the 2009 SSW (which has rather more similarities to the current event but also some significant differences) will follow later on during the week - I'm unlikely to have more time before then. David
  7. Bring Back 1962-63

    [Global] Stratospheric Discussion and Forecasting

    LOOKING FOR SSW SURFACE IMPACTS NEAR THE POLE IN THE MODEL OUTPUT - COMPARISONS TO EARLIER EVENTS - PART 1: 2019 AND 2018 I'm writing this post for two weather forums (US and UK) but most of it is relevant to both N America and UK/Europe. I will be mainly drawing on charts produced by Meteoceil and these + archived charts from the NCEP reanalysis show the Northern Hemisphere from the UK perspective. Abbreviations used in this post: SSW - Sudden Stratospheric Warming SPV - Stratospheric Polar Vortex TPV - Troposheric Polar Vortex HLB - High Latitude Blocking QBO - Quasi Biennial Oscillation MJO - Madden-Julian Oscillation COD - Circle Of Death SOI - Southern Oscillation Index GWO - Global Wind oscillation GLAAM - Global Atmospheric Angular Momentum FT - Frictional Torque MT - Mountain Torque EAMT - East Asian Mountain Torque What I want to examine are the surface pressure patterns and charts in relation to previous SSWs and to show what to look out for in the current output. My focus will be for signs of the reversal propagating down to the surface in the high Arctic and close to the North Pole. I will look at charts around the time each main SSW event started, at the time of the specific types developed (ie: the displacement and/or the split), the time that surface impacts were beginning to show up and one or more later chart(s) to see how blocking patterns fell into place. I will divide this post into at least 3 parts over several days to cover separate SSW events. In part 1, I will look briefly at the current set up and then focus on the February 2018 SSW. In part 2 I'll focus on the 2013 SSW and in part 3, the 2009 SSW. Later on, I may move on to several earlier events - time permitting. Firstly, we need to see the dates, type and length of each event. I repeat this table for reference: This only goes up to 2010. Malcolm @Blessed Weather has kindly helped me obtain similar data for the 2013 event and there is plenty of data available on the Feb 2018 event. If nothing else, these posts will confirm that every SSW is different in many ways. The type of warming with the displaced and/or split vortex events as we know are highly important with the latter "usually" leading to more extensive HLB. The propagation and down welling of the wind reversal to the surface is often far from straight forward and precise timings are extremely difficult to nail down even within the D5 to D7 period. 2019 SSW: SSW started in late December 2018 (precise date to be confirmed). Type - Split, circa January 3rd, 2019. MJO - phases 5 and 6 with 7 and 8 predicted at moderate amp; ENSO - weak El Nino developing (there is a minor blip right now but do not get hung up on the SOI and on some of the S Hem ENSO impacts); wQBO (descending); solar - near minimum. I'll start with the current "ongoing" event which I'll call the "2019 SSW" to avoid confusing it with the earlier 2018 event although the warming in the upper layers started in mid/late December 2018 with repeated attacks on the SPV. GEFS and ECM are much more closely aligned now compared to the last couple of weeks but there is still some uncertainty over how fast the progression will be. In the second half of January we would normally expect this to favour HLB. As this SSW looks like being a long (or even very long) event it would not be too bad if the MJO misses out on its 1 to 4 phases and re-emerges in phase 5/6 again for a repeat performance (perhaps at higher amp) during February to give us a second bite of the cherry. I appreciate that on our side of the pond phases 7 and 8 (and 1) are better for blocking patterns while in N America phases 8 and 1 (and 2) are better. The GWO is now strengthening again and progressing through phase 5 and looking set for phase 6 (if it's not there already with the 2 day chart time lag). The relative GLAAM tendency anomaly has been rising again as is total GLAAM. That's encouraging for +ve tropical forcing but there has been a timing issue. Ideally, we would want to see the SSW surface impacts more or less coincide and it is not completely certain that GLAAM will be maintained in an elevated for more than the next 10 days or so. It is, however, pretty likely that the GWO will perform in a similar way to the MJO and it has been on a repeat cycle since early November. So we might see both January and February impacts. FT (not shown) remains +ve. A reminder of the GWO phase chart. Then we have further good news. Global MT (black line) is +ve and just recently, rising further. This should prevent EAMT (red line) from falling back too far and it'll likely remain +ve for even longer. The strongest signal is at 30N to 40N (the red blobs in the upper part of the chart) centred around the Tibetan Plateau (see my early posts for greater details on this). The +ve torques should assist in keeping GLAAM +ve for an extended period with perhaps only a short weaker or -ve blip. Now to relate this to the models. I prepared this post based on today's 0z and 6z output and I know that the 12z will be out by the time I've finished. As there has been considerable run to run variability this does not really matter as output is likely to remain volatile for at least several more days and possibly rather longer than that. What I noted however, was some remarkable "consistency" on the day 5 output (something not seen at all on previous runs with considerable disagreement): I'll just show the GEFS 6z "mean" for today. The moderate amplification that we've seen so far has been related to the +ve GLAAM, torques and the MJO at decent amp through phase 6. This has produced some quite stationary or slow moving ridges and troughs and the recent cold plunge into Europe which looks set to be repeated during next week. I'll leave it to other posters to comment on their shorter term "home" patterns be it UK, Europe or N America. I'm really focusing on the high Arctic. There are just hints of HP building closer to the North Pole. Now the January 9th chart. HP is building right over the pole. and the TPV is looking set to split just to the south. This is the mean chart but every GEFS ensemble member has HP over the pole at this time (see below), plus the control run + the GFS operational run. Here's the panel : EDIT: I had saved the 6z but the gif updated to the 12z which still has all the members with HP building around the pole. Moreover so do "all" the other main models - GFS (parallel), ECM, GEM, NAVGEM, JMA and ICON. As you'll see when I cover the 2018 and earlier SSWs, these are important early signs. This coupled with the latest news on the stratosphere suggesting that the reversal is now down welling through the troposphere with several commentators suggesting that this may only be 3 or 4 days away. Now, please do not take this as definite - things can still go wrong or at least we may have further delays. The fact that all the models agree on around day 5 for the first signs of polar impacts is encouraging. Rather than pushing things back, if we can move things forward then we'll get the best combination of GLAAM and the torques with the tropical forcing with stronger HLB much more likely and assisting better strat-trop coupling. The full story is still in its early stages. Will the existing amplified pattern link up to HLB? Will there be a transition of a few days with a flatter pattern? Where will the blocking set up? How severe will the cold be and how long will it last? "If" there is a further delay, things still look good into February. So the 2019 SSW still teases us but I remain very optimistic of widespread cold weather going forward with some earlier rather than delayed impacts. 2018 SSW: SSW started during February 2018. Type - Split, circa February 12th, 2018. MJO - phases 3, 4, 5 and 6 at increasing amp and entering phase 7 at around record high amp (see below); ENSO - moderate La Nina (but with a weaker phase in January) eQBO; solar - weak and falling. Note that the MJO was in high amp phase up to the time of the initial triggering of the SSW on February 12th, then continued at weaker amp through to phase 8 (ignore the forecast "green" bit as I'm looking at what actually occurred). The time lagged impacts on HLB fitted in very nicely. This chart from the archives (see below) shows that the MJO continued through phase 1 at increasing amp then onto phase 2 (good for N America which saw the SSW impacts a week to 10 days after the UK and Europe) and briefly into phase 3 before passing through the COD and back out to phase 7 towards the end of March. Here's a link to the archived NOAA weekly reports going back to 2006 and these contain the phase charts and a lot more. http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/ARCHIVE/PDF/ Unlike the current event, GLAAM had been strongly -ve through much of January 2018 and rose strongly at decent amp through phase 4 and 5 into early February and at moderate amp through phases 6 , 7 and into 8 by February 10th. So pretty strong and with +ve torques in the build up to the SSW. The spike in global MT and EAMT in early February and with that 10 to 14 day time lag almost certainly helped to trigger the SSW on February 12th. The next spike may well have assisted the secondary warming. I covered this in more detail in my last post. Now the models. I'm using the excellent NCEP reanalysis charts from the archives. You can trace the whole of the 2018 SSW and much more on this link: http://www.meteociel.fr/modeles/archives/archives.php?day=12&month=2&hour=0&year=2018&map=4&region=&mode=2&type=ncep The SPV split on February 12th and models were generally showing pretty mundane output (seems familiar?). We had some polar maritime air in the UK and central/eastern CONUS and Canada had a "standard" (not SSW related) Arctic outbreak. Just one week later and the models were starting to sniff out something going on and there were signs of the pattern reversal impacting with the build of HP at the pole but only very modest amplification of the Azores HP. Strong HP over central and northern Asia and building across from Alaska. This post is already getting very long but for those of you who want to see how variable the model "forecast" output was a few days before, run through the archived "forecast" charts - here's a link: http://www.meteociel.fr/modeles/gfse_cartes.phpjour=7&mois=2&annee=2018&heure=12&archive=1&mode=0&ech=6&runpara=0&carte=1 You can play around with all the output and reset the date ranges etc. A further week on and it's getting very interesting. Arctic HP extending to Iceland and Scandinavia. The "Beast from the East" was just awakening over Europe and the UK. Note that the TPV was still over northern Canada but it was shortly to be on its journey across to Siberia. Just 4 days later and the TPV had migrated across to Siberia. A true Greenland HP had developed. The surface flow reversal was now pushing on right through CONUS. The beast is at its most intense over western Europe and the UK. Three more days later and the reversed flow at the surface shot through Europe, the UK, across the Atlantic, Newfoundland and through to central CONUS. After weakening somewhat, the SSW (with its secondary warming impacts) is having another go. The "Mini beast" (or beast 2) hits Europe and the UK Canada and central CONUS saw the most severe impacts during much of April 2018. Although the current and the February/March 2018 SSWs were both "split" SPV events you can see that the build up had some similarities but also many differences too. One can see how quickly the model output changed and how dramatic these events can be. I hope that we will see something very special from this event. Watch out for those Arctic profiles and the HP building there. Next up in part 2 (tomorrow) I'll look at the 2013 SSW which had a displaced and a split SSW with separate impacts over a prolonged period. David
  8. Interactive Area for Members - Feedback and Comments This area is for you "the forum members" to get more involved where you will be able to share your views, comments, feedback and ideas about any aspect of this Research Portal by using the standard "reply to this topic" option below this page. You may have found a paper that you feel is suitable for the portal and would like us to upload the link into the portal. Full instructions for this are shown lower down on this page. Your Feedback, Comments and Suggestions There may be all sorts of reasons why you might wish to contribute to this area. These are just a few of them: 1. To help other visitors and researchers - for example: recommending further reading and suggesting other suitable papers covering specific "teleconnection" related subjects (see full instructions below). 2. You might wish to make comments or suggestions to the research portal moderators - for example; you might be aware that a particular author or paper has been discredited or the paper or theory has been superseded or supplemented by a later paper. We do not wish to or cannot be "judge and jury" and we will rely on input and feedback from you, the readers. So please bring this to our attention. 3. You may wish to provide a link to a special site where you feel certain information/data/charts are very useful and this is not easy to find in a run of the mill search (see full instructions below). 4. You may have noticed an error - for example: we may have missed out inserting a tag, used on a paper, into the search list. Please let us know. 5. You may have ideas for how we might develop the portal further or feedback on the current functions. 6. You may wish to discuss something that you have read in one of the papers. Holding Area for Members to Park Papers Awaiting Upload - Requirements and Instructions (+ example) If possible please provide the following details and copy this into the standard "reply to this topic" shown under this page: - the full title - the author(s) - the publication date or year (if known) - copy the full abstract or summary if there is one (if not then a brief description about the theme and contents of the paper would be helpful) - state the tags required (or alternatively, the main teleconnection related topics featured in the paper). Direct link to List of Tags (in User Guide) - copy the link to the full paper (please do not copy the whole paper). - add a note if you have anything to explain to us. Then one of us will upload it. Here's an example of one that was uploaded earlier to show the information required (with instructions in red): Mountain Torques and Northern Hemisphere Low-Frequency Variability. Part I: Hemispheric Aspects (full title) Authors: Francois Lott, Andrew W. Robertson and Michael Ghil (author/s name – if there are many authors you can use the first name and then “et al”) First Published: 2001 (the date the paper was “first published” if known which may be much earlier than when it first appeared online – or both dates) Abstract: (the full abstract or summary if there is one and the link to the abstract) The NCEP–NCAR reanalysis dataset for 1958–97 is used to analyze intraseasonal variations in mountain torques and the large-scale atmospheric circulation patterns associated with them. Spectral analysis of the atmospheric angular momentum (AAM) budget shows that the dominant variations of mountain torque have periodicities near 30 days and shorter, while the dominant AAM variations occur in the 40–60-day band. This difference is due to the 40–60-day AAM variations being primarily related to equatorial processes, while mountain torque variations are associated mostly with extratropical processes. The Northern Hemisphere (NH) mountain torque has enhanced power and significant spectral peaks in the 20–30-day band. The signal in this band accounts for 33% of the NH mountain torque variance, once the seasonal cycle has been removed. Lag composites of the NH 700-hPa geopotential heights based on the 20–30-day mountain torque signal show the latter to be associated with coherent large-scale patterns that resemble low-frequency oscillations identified in this band by previous authors. The composite patterns that are in phase quadrature with the 20–30-day NH mountain torque have a pronounced zonally symmetric component. These patterns are associated with substantial AAM variations, arguably driven by the NH mountain torque in this band. Principal component (PC) analysis of the NH 700-hPa heights shows that, in the 20–30-day band, the mountain torque is also in phase quadrature with the two leading PCs; the first corresponds to changes in the midlatitude jet intensity near the subtropics, while the second corresponds to the Arctic Oscillation. The relationships with AAM of the latter essentially occurs through the mass term. Mountain torques are, furthermore, nearly in phase with dominant patterns of low-frequency variability that exhibit substantial pressure gradients across the Rockies and the Tibetan Plateau. Link to full paper: (the link to the full paper which may be from another source if it is blocked as a “free-to-view” option on the main source) https://journals.ametsoc.org/doi/pdf/10.1175/1520-0469(2004)061<1259%3AMTANHL>2.0.CO%3B2 Please note that the following tags were allocated to this paper: mt, aam, mjo (your suggestion for suitable tags – optional as we can add these) (please add any specific comments that you wish to make related to the paper that you would like us to include in the upload)
  9. Bring Back 1962-63

    Interactive Area for Members - Feedback and Comments

    Hi, thank you for your kind comments. We had started work on the glossary but progress was very slow as our main work in the time available has been to add papers and presentations into the portal and maintain the comprehensive index. This takes a vast amount of time and eats into our posting and reading activities during our "weather" time. I've also been working on a Teleconnections thread index and was planning one for the Arctic thread but I've already taken on far too much - I run a full time online business (not weather related). The Glossary page is currently "hidden" as is the "Learner's Area" page which has had no work done on it yet. We may have slightly more times in Spring and we'll review our Research Portal activities then. You are the first to comment on the Glossary and if we get a few more requests, this would encourage us to develop it. David
  10. Bring Back 1962-63

    [Global] Stratospheric Discussion and Forecasting

    This post could just have easily gone on the Teleconnections thread but it's here to address several queries relating to the SSW. Unfortunately we cannot get MT charts for that far back - Dr Klaus Weickmann and Ed Berry were in the pioneering early stages of developing their GSDM (global synoptic dynamic model) and these charts did not appear until a few years later - I think around 2007/8 (but others may know the precise date). When they left NOAA in 2015 their service was discontinued but the data is still being assimilated to produce the current output. I've been trying to build up an archive of MT charts as there is no official archive and it is costly and time consuming for the few that have access to the raw data to reproduce them. I've found a few from forum and library archives back to 2010. If anyone can provide charts prior to 2010, that would be great and please let me know with the link or copy of the chart, so that I can update my archive records. A few of us are researching MT especially in relation to SSW events and @Blessed Weather and myself are keen to take this a lot further - an ongoing long term project. There is another way of judging the approximate strength of EAMT from the pressure and jet stream charts and we have excellent reanalysis charts going back to 1871. Here's the link: http://www.meteociel.fr/modeles/archives/archives.php?mode=2&amp;month=12&amp;day=15&amp;year=2001&amp;map=4&amp;type=ncep I set it to Dec 15th 2001 but you can look at any date with a range of options, including the 850s. The northern hemisphere charts are set from the UK view (0 longitude). For east Asia we need to focus on the top right corner. I show a map for reference. That 985mb LP in the chart below is centred over eastern China/Mongolia. You can just see Japan sticking out under "1015mb" . From the chart that I show in my last post on here yesterday (several posts above) we can see that the 2001/2 SSW had a central date of day 361 or Dec 28th 2001, a duration of 35 days (would have lasted from about Dec 11th to Jan 14th), was a displaced vortex (with no split) with the peak of the displacement on day 357.75 (late on Dec 24th). We are looking for HP to the east and north of the main mountain massif (mostly east China and south east Russia) and LP to the south and west. The chart below is a very simplified version of this which applies perfectly to NAMT and the Rockies as they are a north to south range and perpendicular to the westerly motion. The east Asian mountain massif covers a vast area. In that Dec 15th chart we can see that EAMT is actually most likely to be -ve with LP to east and HP to the west - below on the chart. If I had more time, I would rotate the chart by 90 degrees to make the viewing easier. The uplifting from the Tibetan Plateau and the Mongolian Mountains can also be generated by the jet stream blowing strongly across and being intercepted by the very high Himalayan peaks and channelled north eastwards down the lea side of that range and beyond. So we should look for strong jet streaks (orange/red colours) blowing over several days. We need to spin through both charts (pressure and jet) from late November to early January. I've just checked this quickly and the southern branch of the jet was mostly blowing extremely far south and for long period actually south of the Himalayas. There were several short periods when it blew more directly over the mountains but these look to me to have been brief and probably insignificant. Wrt the pressure, I note some unusually HP to the south west of the Himalaya range (over 1070mb on Dec 22nd) which is an odd pattern but suggestive of -ve EAMT. In fact the only time when we had LP to the south west and HP to the north east was briefly around January 6th. IMHO, I doubt if there was any +EAMT during this entire period. I would like others to comment on these charts too - such as Tom, Tams and Zac as my interpretation may be wide of the mark. Overall, if I'm right, then we need to examine all the SSWs in relation to the archive charts and the MT charts when they are available (from 2010 onwards) and we also need to look at the different types of SSWs and near misses and failures too. I certainly want to research the correlation a lot more. Perhaps we "always" need +ve EAMT events to help trigger SSWs, for splits and to assist down welling and propagation down to the surface. David EDIT: I nearly forgot the mjo archive charts which were requested too. The NOAA weekly MJO reports go all the way back to 2006. The chart types evolved over the years but there is enough data there to assess the phases and amp at any time. Unfortunately, they are not available before 2006. D http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/ARCHIVE/PDF/
  11. Bring Back 1962-63

    [Global] Teleconnections: A Technical Discussion

    Hi @Newman, we get them from a friend of Ed Berry who along with Dr Klaus Weickmann developed the GSDM and devised the GWO phase charts. We have special access and have made the links available to everyone on this forum. Several of us are in regular contact with Ed. If you go to Zac's @Snowy Hibbointroductory post at the head of this thread you'll see that he posted many useful links including the AAM and torque data that I obtained from Ed's friend. I wrote out full instructions as you'll need the user ID and password shown. David
  12. Bring Back 1962-63

    [Global] Teleconnections: A Technical Discussion

    I just posted this across the pond for a slightly different audience - only slight editing: REALLY GREAT NEWS! Now some of you will not realise the significance of this: Those of you who have been reading my posts and those from the likes of @Tamara, @Isotherm @Snowy Hibbo and others who comment on the key teleconnections will know that we've been banging on about +ve EAMT (East Asian Mountain Torque) in particular. We could see this event unfolding a few weeks ago as part of the GSDM (global synoptic dynamic model), the GWO (global wind oscillation), GLAAM (global atmospheric angular momentum) and both FT (frictional torque) and MT (mountain torque) which all link in with tropical forcing, the ENSO state and the MJO. These charts are produced 2 days after the actual position - so this afternoon's chart (above) shows the position as on Dec 29th. In my previous posts I said that EAMT was already rising strongly and that could be seen in the pressure distribution over eastern Asia (I showed the StormSurf charts, most recently yesterday). Well, EAMT is not just rising but it's sky rocketing as can be seen by the red line in the chart and looks set to climb quite a bit higher, in fact with that 2 day chart time lag it already is. I'll not go into the complexities but +ve EAMT events have an extraordinary influence on all levels of the lower and middle atmosphere and especially on the northern hemisphere global weather patterns and many of these assist directly or indirectly with setting up ridges and troughs and blocking patterns. Here are some of them: 1. A "major contributor" to wave breaking in the stratosphere (there are other influences too, of course) and vortex attacks by creating huge uplift and vertically propagating planetary waves from the Tibetan Plateau and particularly (as discovered more recently) the Mongolian Mountains, which can reach the upper stratosphere and even the lower mesosphere before reaching the "critical level" which is effectively "wind shear" in the troposphere as shown in this chart. In the stratosphere the critical level has the easterlies above it which are the reversed winds and the planetary waves cannot break through it and are reflected (or even deflected) back down and they break at increasingly lower levels. This produces one or more attacks on the spv (stratospheric polar vortex) and prolonged events can send up further planetary waves with attacks from above and below. The last surge in EAMT occurred during Dec 4th to 12th and peaked around Dec 9th/10th. A few days later we saw some attacks on the SPV. 2. Now we have a further event which is likely to repeat the exercise and if there's any problem with the split or the downward propagation this may well deliver the final blow to the SPV in a few days. In fact the timing is almost perfect with the split (if it happens) predicted for later this week. 3. EAMT also influences the tropospheric patterns with lateral planetary waves influencing the jet stream and downstream patterns in winter across the North Pacific and into N America. This can cause the jet stream to meander and/or buckle. This action in association with other factors can have knock on effects setting up the pattern and distribution of troughs and ridges around the hemisphere. 4. In the summer half of the year EAMT has a powerful influence on the Asian Monsoon. 5. The planetary waves also spread polewards and this is where it gets very interesting. Some of us will have heard of and studied Judah Cohen's theories on early Asian Snow Cover extent and the greater likelihood of SSWs. He recently admitted that it is more complicated than that and it was not a perfect correlation but nevertheless it does seem to work more often than not.. Over some years and particularly more recently, research has strongly suggested a link between North Asian blocking and the priming of the lower tropospheric layers and the surface to be receptive to a down welling SSW. In several of my recent posts I've been showing those Asian pressure charts and the extraordinary expanse of HP over almost all central Asia northwards, Russia and Siberia. I've been looking at the timing of these events and I'm pretty sure that it's no coincidence that a combination of +ve EAMT, extensive Asian snow cover (well above average right now as I showed yesterday) and the blocking regime are all coming together to make the patterns receptive or even highly conducive to downward propagation of the SSW to the surface. This obviously needs to be explored much more extensively and research into earlier SSWs (including near misses and failures) need to be considered. Another factor is GWD (gravity wave drag) which is mostly generated by the the east Asian mountains as well. That will be one of my 2019 projects and Malcolm and Tom are likely to participate and others will be welcome. Malcolm @Blessed Weather and I have been studying these events and found that they fitted in perfectly to last February's SSW. Here's the MT chart for back then: Note the 3 spikes in EAMT. The first one around Feb 1st to 5th and the SSW was triggered a week later on Feb 12th. The second one around Feb 20th-25th and we saw the full propagation down to the surface and just a few days later with the "Siberian Express" rushing westwards and producing the "Beast from the East" in the UK and progressing around the hemisphere to N America about a week or so later.. The final spike was March 5th-10th and the "Mini Beast" followed about a week or so later and with further impacts on N America a few days later (and lasting much longer). Overall, some of this is still theory but the extraordinary influences of +ve EAMT events have been studied for over 20 years. Now more of you might realise why I'm so excited about this month's two +ve EAMT events. The models simply do not have much of these influences factored into how they churn out their nwp solutions and it's why they often need a few days to adjust to changes in the background signals. Before long we are likely to see some much more sophisticated models being developed. The next few days of monitoring the model output will be totally absorbing and fascinating. Finally a Happy New Year to everyone and what a January we have in store for us! David
  13. Bring Back 1962-63

    [Global] Stratospheric Discussion and Forecasting

    It's happened a few times - 6 or 7 times between 1979 and 2001: David
  14. Bring Back 1962-63

    [Global] Teleconnections: A Technical Discussion

    Just to add a little more to Tom's @Isotherm excellent update and several updates today (above) - things do seem to be going very much according to plan with perhaps some real clarity likely to emerge during this week. EDIT: and while writing this I see that Tams @Tamara has just posted with some encouraging comments but with some wise words of caution too. An excellent post as usual and an interesting comparison to the 2012/13 SSW and the key teleconnections at play back then compared to now. I'll make brief comments below each chart: The total GLAAM anomaly which has remained +ve all month but eased back recently is now rising again. The strongest +ve anomaly is currently at the equator. The relative GLAAM tendency anomaly which spiked for 5 days, remains +ve but has levelled off. Tom showed us the latest +ve FT and +ve MT charts with the strongest rises showing in the highly important EAMT which is +ve and climbing. The highest values (red blobs) are once again being seen over the Tibetan Plateau and (with the 2 day time lag in these charts) is almost certainly over the Mongolian Mountains right now. As I expected (well - as I hypothesised) GWD should be rising in that same area just before EAMT is at its strongest and indeed it is around 35N to 50N. More below on this. The GWO has stalled temporarily in neutral orbit but looking set to emerge in phase 5 (IMHO). With rising AAM and the torques we are likely to see the GWO rising though phase 5 - I do note several comments on this with some views expressed going for a slightly longer delay in this progression and we'll need to see exactly what unfolds during this week. I feel that the key torque right now is EAMT but it is unwise to separate out any part of the whole GSDM process and we must consider all aspects together. So, I'll rephrase that and say that +ve EAMT has some very strong influences on planetary waves - lateral (eastwards impacting on the Pacific patterns downstream), northwards (to aid North Asian blocking) and vertically (strong uplifting often into the upper stratosphere and lower mesosphere). I note the views expressed by @Allsnow and @donsutherland1 and understand some of the pros and cons of the RMM plots versus the VP200 and I feel that they both have their place but as the latter update has been posted today, here are the latest RMMs. The GEFS bias corrected maintains its strong amp through phase 6 and into 7 before stalling there. ECM continue to go for a faster progression through phases, 6, 7, 8 and at decreasing amp and entering the COD later than on recent runs. Most of the other models are somewhere in between the big 2. That vast expanse of high pressure extends across almost all eastern, central, northern and western Asia , Russia and Siberia and pushed even further westwards. Strong blocking in this region is considered to be a key precursor for SSW impacts and very likely to assist with strat/trop coupling making the lowest layers more receptive. This + the spiking EAMT are very encouraging. I posted this chart recently but the northern hemisphere snow cover has extended even further south and looks really impressive before we even consider the SSW and tropical forcing impacts. Global surface temps and particularly N Hem temps have fallen close to their lowest levels since Feb/Mar at the time of the last SSW. The trend in much of Europe and the UK is a downward one for the next 7 days but this is due to slightly greater amplification under the existing HP and not HLB (high latitude blocking) at this stage. There are some low anomalies over Alaska and -ves over SE and parts of eastern CONUS. The lowest anomalies of all are in the key North Asian/Russian/Siberian region with some parts seeing -ve anomalies approaching 20c below average. I also note that the Arctic has turned much colder with overall -ve anomalies developing there (Greenland remains +ve). The more cold to be displaced from the Arctic the better. I will do an Arctic update within the next few days. It's not just global land temps that have been falling, global SST anomalies have continued to fall back steadily almost all month and if anything the trend is accelerating again. They are close to their lowest values for 5 years as shown below. This may be a temporary trend and is something that we'll need to examine more closely on the Teleconnection thread but it's good to see some respite from the global warming trends. Overall, in the context of the SSW, the tropical forcing and the other key teleconnections there are some very encouraging signs and a lot might be revealed during this week. David
  15. Bring Back 1962-63

    [Global] Stratospheric Discussion and Forecasting

    Hi @sebastiaan1973, Interesting post and a fascinating paper which I've just placed into the Research Portal and given you credit for finding it - thank you. I found another link to the "Atmosphere" (Volume 9, issue 12, December 2018) site which provides the full paper without having to download a personal pdf file (these direct links are usually available for "Open Access" papers like this one). This link will take one to the abstract and from there the link to the full paper: Enhanced Stratosphere/Troposphere Coupling During Extreme Warm Stratospheric Events with Strong Polar-Night Jet Oscillation That's the way we set up the portal to allow visitors to read the summary and then to decide if they wish to read the full paper. On this occasion, for fast and direct access, here's the link: https://www.mdpi.com/2073-4433/9/12/467/htm For balance and for those interested in this fascinating and important aspect of SSWs, I show below a list of the papers which focus on stratosphere/troposphere coupling. Most of these are in relation to SSWs and many are quite recent papers. Just click on any title for a link to the abstract for a quick skim through what we already have and then you can decide if you wish to read the full paper. If I had more time, I would review a few of these papers on here. You'll see that between them they relate to and cover all the teleconnection interactions that we've been covering wrt this SSWs on this thread and the Teleconnection thread. The point that some of us have been trying to stress is how important the tropical forcing influence is and the spike in relative GLAAM tendency Global Atmospheric Angular Momentum), FT (Frictional Torque), MT (Mountain Torque) and especially EAMT (East Asian Mountain Torque) as part of the GSDM (Global Synoptic Dynamic Model) and the GWO (Global Wind Oscillation) processes including the ENSO state and the MJO. It is surprising how much is referenced to the stratosphere and the SSW itself by some of the authors but they often ignore some of the other Teleconnections. Perhaps the least understood aspect of SSWs is the propagation or down welling of the wind reversals to the surface, the strat/trop coupling and the surface impacts of displaced and/or split SPV events. I firmly believe that a lot of the answers are in looking at how receptive the lower trop and surface layers are to strat influences. In this respect the 2012/13 event (full surface impacts) looks to be a better match than the 2001/02 event (struggled to down well fully). This is something that we've discussed on our PM thread and Tams @Tamara suggested - but I would not wish to quote her out of context. Overall I remain very bullish of a full on SSW but some on here have a much better understanding of the strat than I do. David Coupling - Stratosphere/Troposphere: Comparing Extreme Heat Flux Events for Wavenumber 1 and 2 Coupling of Stratospheric Warmings with Mesospheric Coolings in Observations and Simulations Defining Sudden Stratospheric Warming in Climate Models: Accounting for Biases in Model Climatologies Dynamic coupling of the stratosphere with the troposphere and sudden stratospheric warmings Enhanced Stratosphere/Troposphere Coupling During Extreme Warm Stratospheric Events with Strong Polar-Night Jet Oscillation Eurasian snow cover variability and links to winter climate in the CMIP5 models Interannual variability in the gravity wave drag – vertical coupling and possible climate links Linking stratospheric circulation extremes and minimum Arctic sea ice extent MJO‐Related Tropical Convection Anomalies Lead to More Accurate Stratospheric Vortex Variability in Sub-seasonal Forecast Models Multi‐decadal variability of sudden stratospheric warmings in an AOGCM On the dynamics of the formation of the Kelvin cat's eye in tropical cyclogenesis - Presentation Preconditioning of Arctic Stratospheric Polar Vortex Shift Events Progress in research of stratosphere-troposphere interactions: Application of isentropic potential vorticity dynamics and the effects of the Tibetan Plateau Propagation of planetary‐scale disturbances from the lower into the upper atmosphere Revisiting the ENSO–SSW Relationship Role of Finite-Amplitude Eddies and Mixing in the Life Cycle of Stratospheric Sudden Warmings Role of gravity waves in vertical coupling during sudden stratospheric warmings Snow-atmosphere coupling and its impact on temperature variability and extremes over North America Snow–atmosphere coupling in the Northern Hemisphere Snow–Atmosphere Coupling Strength. Part I: Effect of Model Biases Some Observed Features of Stratosphere-Troposphere Coupling - Lecture Stratosphere‐troposphere exchange The association between stratospheric weak polar vortex events and cold air outbreaks in the Northern Hemisphere The Life Cycle of Northern Hemisphere Downward Wave Coupling between the Stratosphere and Troposphere Three Types of Synoptic Events and Their Associated Troposphere-Stratosphere Coupling Transfer of the solar signal from the stratosphere to the troposphere: Northern Winter Tropospheric and Stratospheric Precursors to the January 2013 Sudden Stratospheric Warming Why are Upward EP-Flux and Temperature Positively Skewed in the Stratosphere?
  16. Enhanced Stratosphere/Troposphere Coupling During Extreme Warm Stratospheric Events with Strong Polar-Night Jet Oscillation Author: Dieter H.W. Peter, Andrea Schneidereit and Alexey Y. Karpechko Published: November 29th, 2018 Abstract: Extreme warm stratospheric events during polar winters from ERA-Interim reanalysis and CMIP5-ESM-LR runs were separated by duration and strength of the polar-night jet oscillation (PJO) using a high statistical confidence level of three standard deviations (strong-PJO events). With a composite analysis, we demonstrate that strong-PJO events show a significantly stronger downward propagating signal in both, northern annular mode (NAM) and zonal mean zonal wind anomaly in the stratosphere in comparison with non-PJO events. The lower stratospheric EP-flux-divergence difference in ERA-Interim was stronger in comparison to long-term CMIP5-ESM-LR runs (by a factor of four). This suggests that stratosphere–troposphere coupling is stronger in ERA-Interim than in CMIP5-ESM-LR. During the 60 days following the central date (CD), the Arctic oscillation signal was more intense during strong-PJO events than during non-PJO events in ERA-Interim data in comparison to CMIP5-ESM-LR runs. During the 15-day phase after CD, strong PJO events had a significant increase in stratospheric ozone, upper tropospheric zonally asymmetric impact, and a regional surface impact in ERA-Interim. Finally, we conclude that the applied high statistical threshold gives a clearer separation of extreme warm stratospheric events into strong-PJO events and non-PJO events including their different downward propagating NAM signal and tropospheric impacts. Link to full paper: https://www.mdpi.com/2073-4433/9/12/467/htm Credit goes to @sebastiaan1973 for finding this paper
  17. Bring Back 1962-63

    [Global] Stratospheric Discussion and Forecasting

    Hi Tom, that's a great read and I had it in my store ready to place into the portal. It was behind a paywall until quite recently. I've just added it right now: Eurasian snow cover variability and links to winter climate in the CMIP5 models Click on the title for a link to the portal abstract. There are many more papers on SSWs, the Stratosphere, the SPV, Coupling - strat/trop, Siberian Snow Cover and related teleconnections in the portal.. Why not check out the index while you're there: INDEX TO PAPERS AND PRESENTATIONS I am wondering if those early impacts in North Asia will help make the surface more receptive to strat/trop coupling. Certainly North Asian blocking is another strong precursor to an impacting SSW. I hypothesise that a combination of Eurasian snow cover, north Asian blocking, +ve EAMT and perhaps also +ve Gravity Wave Drag are all part of an inter relationship which assist SSWs in several ways: 1. The huge uplifting from the Tibetan Plateau and particularly the Mongolian Mountains which sends the strongest vertically propagating planetary waves from anywhere in the world right up into the upper strat and even the lower mesopshere which is probably associated with the final triggering of major SSW events or at least a strong contributory factor to attacking the SPV (from above and below as the waves break once they hit the critical layer of wind reversals and then break at increasingly lower levels). 2. They help to make the surface more receptive to the final downwelling through the tropospheric layers. This is the area of SSW theory which produces the most challenges and there have been many recent papers and many more in the pipeline as we learn from every SSW event and this is a truly fascinating one. We are just entering another bout of +ve EAMT which will show up on the mountain torque chart by tomorrow or Sunday (always a 2 day time lag) . The red line is EAMT. The upper part of the chart shows where it is most +ve (red) and most -ve (blue). The spike in EAMT around Dec 10th (chart segmented in 5 day slots) was strongest over Tibet/Mongolia (35N to 45N). With a few days time lag, that was very likely playing a helping hand in an earlier attack on the SPV. The next spike "should" be happening now and I await the Dec 28th and 29th charts (on Sunday and Monday) with great anticipation. This should be perfect timing with the split expected in the first few days of January and that's exactly when the next bout of planetary waves should be breaking up there. We do not need to wait for confirmation of the +ve EAMT event as we have a vast belt of very high pressure there right now. The pressure is anomalously high in northern Asia, much of Russia and Siberia in mid winter but I've rarely seen anywhere near such an expanse as right now. Widely over 1050 mb and over 1060 mb around and to the north of the Mongolian Mountains. Global temperatures have the lowest -ve anomalies in that region right now too - widely 6c to 9c below average. We already have some really impressive northern hemisphere snow cover extent before we get into this January cold spell! I must finish now as I'm off out again. David
  18. Eurasian snow cover variability and links to winter climate in the CMIP5 models Author: Jason C. Furtado, Judah L. Cohen, Amy H. Butler, Emily E. Riddle and Arun Kumar Published: 31st January, 2015 Abstract: Observational studies and modeling experiments illustrate that variability in October Eurasian snow cover extent impacts boreal wintertime conditions over the Northern Hemisphere (NH) through a dynamical pathway involving the stratosphere and changes in the surface-based Arctic Oscillation (AO). In this paper, we conduct a comprehensive study of the Eurasian snow–AO relationship in twenty coupled climate models run under pre-industrial conditions from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Our analyses indicate that the coupled climate models, individually and collectively, do not capture well the observed snow–AO relationship. The models lack a robust lagged response between October Eurasian snow cover and several NH wintertime variables (e.g., vertically propagating waves and geopotential heights). Additionally, the CMIP5 models do not simulate the observed spatial distribution and statistics of boreal fall snow cover across the NH including Eurasia. However, when analyzing individual 40-year time slices of the models, there are periods of time in select models when the observed snow–AO relationship emerges. This finding suggests that internal variability may play a significant role in the observed relationship. Further analysis demonstrates that the models poorly capture the downward propagation of stratospheric anomalies into the troposphere, a key facet of NH wintertime climate variability irrespective of the influence of Eurasian snow cover. A weak downward propagation signal may be related to several factors including too few stratospheric vortex disruptions and weaker-than-observed tropospheric wave driving. The analyses presented can be used as a roadmap for model evaluations in future studies involving NH wintertime climate variability, including those considering future climate change. Link to full paper: http://web.mit.edu/jlcohen/www/papers/Furtado_etal_CD15.pdf Credit goes to Tom @Isotherm for recommending this excellent paper.
  19. Bring Back 1962-63

    [Eastern US] Dec. 2018: Consolidated Discussion / Obs

    Hi, it's always useful to learn from those past events as long as we accept that every SSW is different. The Feb SSW built up in quite a different way and once the wind reversal reached the surface in the Arctic, it impacted on Siberia and then progressed very rapidly westwards through Europe and the UK and on to N Am about a week or so later. We called it the "Siberian Express" in Europe and in the UK "The Beast from the East". Then we had the secondary event about 2 weeks later - the "Mini Beast". Those impacts were also felt initially over on our side of the pond but when they reached you, you guys remained cold for a lot longer than us. Malcolm @Blessed Weather and I reviewed the 2018 SSW in several posts on the Teleconnections back in April. In fact Malcolm's main post was outstanding and I would like to nominate it as a contender for the "33andrain post of the year" award. Here's the link: https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&amp;comment=86401 I urge everyone who is interested in the current SSW to read it - it's so informative and filled with many great annotated charts. Malcolm looks at the strat from November right through to April and guides us right through all the build up and the impacts. David
  20. Bring Back 1962-63

    [Global] Teleconnections: A Technical Discussion

    Some Dramatic Pattern Changes Look Even Closer Just a very brief update as I'm off out again in a minute for further family celebrations. I noticed the further increase off the scale of the MJO in phase 6 on yesterday's bias corrected GFS chart (as posted by @Nchaboy above with Joe Bastardi's tweet and repeated below) - we should be looking for ECM and others to increase their amp too later this week for the week 2 period BOMM has already joined the party). Just to underline @earthlight's excellent update above, the current SSW impacts over North Asia, Russia and southern Siberia are showing up even more so now: Over the next 1 to 2 days, the enormous expanse of HP is set to go over 1060mb. This will be associated with a huge spike in EAMT. This chart is only from Dec 23rd but as I said with the previous chart it'll be +ve by now and going much higher. Note that the SST anomalies have all dropped in all 4 Nino regions, and especially in the EPAC 1+2 (a 1.5c drop in 2 days). Global SSTs and land surface temps have continued to fall (for over a week now). Out of time. More tomorrow. David
  21. Bring Back 1962-63

    [Global] Teleconnections: A Technical Discussion

    Short Update - More Changes in the Right Direction and Looking Great for a Cold Spell Our AAM and torque specialists (and myself) have been consistently pointing towards a huge spike in MT following the recent fall to -ve levels. It's a bit like an elastic band being pulled back and stretched to the limit and then released and the lower it goes then the bigger the bounce back as mother nature must restore the balance. Well this is already underway: GLMT (black line) having nose dived is now rising again. We can expect something similar to what we saw at the beginning of December. Remember that these charts are always 2 days behind. I would expect that values are already going +ve right now. Note that NAMT (blue line) and EAMT (red line) are climbing too. EAMT is so important and the ups and downs can be seen clearly in the upper part of the chart. That blue blob at 30N to 45N is the -ve EAMT over the Himalayas, Tibetan Plateau and Mongolian Mountains. We can expect that to turn to deep red (again) during the next 3 or 4 days and this will be bang on schedule. This is likely to send yet more planetary waves up into the upper stratosphere and may help to apply the final blow to trigger the major SSW several days later (perhaps around New Years Eve/Day). That's if downward propagation is still struggling by then. Surface impacts may well be seen more quickly than has been forecast by some. In any event, the poleward shift in +ve momentum is very timely for favouring high latitude blocking as well as making the lower troposphere highly conducive and receptive to any SSW impacts. Just read the recent posts by Tams @Tamara, Tom @Isotherm @isotherm, Zac @Snowy Hibboand others too for confirmation of what to expect. The relative AAM tendency anomaly and FT are also rising again and the GWO is steady in phase 8 and set to rush back to phase 5 with the rising AAM and torques - no time to include those charts now. . Then we have this - have GEFS been on the Christmas drinks We expected an adjustment to increasing amp but this is going off the chart and it would be even higher than the record breaking phases 6/7 that we saw during the February SSW event. This is the bias corrected version! Let's not get carried away (perhaps I should be!) - ECM still maintaining a change to low amp after Xmas but also progressing through the key phases favouring HLB. Still time for the amp to increase. We may not need "all" these teleconnections to fall into place but something very special seems to be brewing with some extreme events coming together. Once again, I wish everyone a very Merry Christmas. I'll try and produce several updates later this week after Christmas as what's on the cards as we move into January looks incredibly exciting for cold hunters in the eastern CONUS, eastern Canada, Europe and the UK. This is dramatic stuff and absolutely fascinating for all those studying the background signals. David
  22. Bring Back 1962-63

    Bring Back 1962-63

  23. Bring Back 1962-63

    [Eastern US] Dec. 2018: Consolidated Discussion / Obs

    What Not To Expect! We know the GFS has a bias for over intensifying LP systems. Well I was just running through the northern hemisphere GEFS 0z run and came across a record breaking Aleutian or Bering Sea LP (the GFS chart version view we get in the UK is angled from our perspective not N America) . This is perturbation 2 for next Sunday - just for fun. With 925mb shown, I would say that the CP would be nearer 922mb or 923mb. The existing NPAC record (excluding tropical cyclones and hurricanes) is 925mb set on October 25th, 1977 at Dutch Harbor, Alaska. That's the "official" record but I believe that there have been several unofficial readings of 924mb with one as recently as December 14th, 2015 during the peak of the super El Nino. With GFS struggling to model the SSW - displaced or split - with some highly variable output from run to run, we should not take this outcome seriously. Last February, they modelled a sub 930mb LP off the southern tip of Greenland on several op runs a week before the SSW impacts and they were a mere 105mb out! All models have their known biases and inaccuracies but these "barrel" lows appear all too frequently on GFS models and I thought that they would have ironed these major deficiencies out by now. David
  24. IMPROVING THE SAFFIR-SIMPSON SCALE AND OUR RESPONSE TO HURRICANES Author: Logan Giles Published: 22nd December 22nd, 2018 Abstract: This paper analyzes why the Saffir-Simpson Scale remains outdated and dangerous, and will offer a suggestion for a new scale. Currently, the global scale on how we measure hurricanes and tropical systems continues to be the Saffir-Simpson Scale. This scale, first created in 1971 provides a means for the public to better assess the severity of these storms. The Saffir-Simpson Scale uses one factor – wind. The higher the wind, the stronger the storm, and therefore, the higher assigned number. While wind speed certainly remains important, it should not be the only factor used to determine the severity of a storm. Additional weather threats should factor into the analysis to better account for potential damage hurricanes and tropical storms bring. By including these additional threats, the public will be better informed to make decisions that affect their safety and that of their families. Link to full paper: https://docs.google.com/document/d/1MqPn6Aq_KjmQVtVlNtchjgAer7SAySsQG8WSNck1lw8/edit Link to Blog On This paper: https://www.33andrain.com/topic/1541-research-paper-on-hurricanes/
  25. Bring Back 1962-63

    Research Paper on Hurricanes

    Hi Logan, an interesting paper with some very valid points and suggestions. I really like the idea of your new proposed scale. We know that it can be a tough exercise to persuade the "establishment" to embrace changes, especially for a widely used internationally accepted scale. I've seen quite a few comments wrt having a category 6 for the most powerful storms as cat 5 covers a wider range than the others but NHC so far does not seem to be interested in making any changes. Getting them to consider adding your key criteria will be hard enough let alone actually adopt any changes. May I suggest that you start to use your methods and put them out there for all to see every time a major hurricane and/or a landfall tropical storm is predicted. Those of us that post regularly on this forum's hurricane thread (like myself) could easily include references to "The Giles Scale" when it's appropriate. As this embraces the potential impacts and dangers it could easily be used alongside the Saffir-Simpson Scale and I'm sure that the media would catch on to it very quickly as they want to report on all the dangers and damage. Frankly, anything that helps the authorities to prepare for the and quantify the potential impacts is a useful warning tool and your proposed scale does exactly this. You need to give this wider exposure. I've just placed your paper into the Research Portal (just click on the title for a link to portal entry: Improving The Saffir-Simpson Scale and Our Response to Hurricanes) so that anyone checking out the "hurricanes" heading in the index will become aware of it. To get members who view this thread to read your excellent paper, we should whet their appetites - so I've copied your table below: The Current scale looks like this: I often posted the Saffir-Simpson scale in my hurricane reports this year (such as in my updates on the Florence thread) to remind readers of the relative strength of major storms. I'll add your table to these during the 2019 season. The more posters that refer to it, the more publicity you'll get and the more likely that NHC and others start to take your proposals seriously. David
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