Model output discussion - heading into 2018

[northwestsnow]

4 minutes ago, feb1991blizzard said:

Ext eps depict signals for a genuine Euro trough towards the end of the run.

By day 10 the euro high looks like its going to be very hard to shift Feb-

Still, i will take any positives at the moment (aside from NAO  obv)

[Paul]

6 minutes ago, Ed Stone said:

Something that's always puzzled me about the MJO: Is it an 'external' signal derived independently of the models (like the QBO?) or is it, like the NAO, something that's extracted from ordinary model output, and thus little more than a kind of shorthand for whichever facet of global synoptics it's supposed to explain/simplify?

I have a job discerning cause from effect...

 

Some good info here Pete:

https://www.climate.gov/news-features/blogs/enso/what-mjo-and-why-do-we-care

[knocker]

14 minutes ago, Ed Stone said:

Something that's always puzzled me about the MJO: Is it an 'external' signal derived independently of the models (like the QBO?) or is it, like the NAO, something that's extracted from ordinary model output, and thus little more than a kind of shorthand for whichever facet of global synoptics it's supposed to explain/simplify?

I have a job discerning cause from effect...

 

This is pretty good. probably similar to Paul's

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/MJO_summary.pdf

 

[knocker]

This is also interesting even though not recent  but unfortunately it's paywalled

Intraseasonal interaction between the Madden–Julian Oscillation and the North Atlantic Oscillation

Quote

Bridging the traditional gap between the spatio-temporal scales of weather and climate is a significant challenge facing the atmospheric community. In particular, progress in both medium-range and seasonal-to-interannual climate prediction relies on our understanding of recurrent weather patterns and the identification of specific causes responsible for their favoured occurrence, persistence or transition. Within this framework, I here present evidence that the main climate intra-seasonal oscillation in the tropics—the Madden–Julian Oscillation^1,2 (MJO)—controls part of the distribution and sequences of the four daily weather regimes defined over the North Atlantic–European region in winter³. North Atlantic Oscillation⁴ (NAO) regimes are the most affected, allowing for medium-range predictability of their phase far exceeding the limit of around one week that is usually quoted. The tropical–extratropical lagged relationship is asymmetrical. Positive NAO events mostly respond to a mid-latitude low-frequency wave train initiated by the MJO in the western–central tropical Pacific and propagating eastwards. Precursors for negative NAO events are found in the eastern tropical Pacific–western Atlantic, leading to changes along the North Atlantic storm track. Wave-breaking diagnostics tend to support the MJO preconditioning and the role of transient eddies in setting the phase of the NAO. I present a simple statistical model to quantitatively assess the potential predictability of the daily NAO index or the sign of the NAO regimes when they occur. Forecasts are successful in ∼70 per cent of the cases based on the knowledge of the previous ∼12-day MJO phase used as a predictor. This promising skill could be of importance considering the tight link⁴ between weather regimes and both mean conditions and the chances of extreme events occurring over Europe. These findings are useful for further stressing the need to better simulate and forecast the tropical coupled ocean–atmosphere dynamics, which is a source of medium-to-long range predictability and is the Achilles’ heel of the current seamless prediction suites^5,6,7.

https://www.nature.com/articles/nature07286#figure-title

[summer blizzard]

1 hour ago, nick sussex said:

Yes well in recent years its been muted out by other factors  even when its been in a favourable phase for us.

 

Not really. The last time we had really amplified phase 6-7-8-1 orbits in winter were November 2016 and January 2015. Nobody would much complain about either month.

It will be interesting to see if the MJO actually does head through a complete orbit.

[ArHu3]

Not often that you see such unity between the members so far out, especially in the wind direction plume 

[Guest]

Please note: I started working on this post this morning but I had to break off for a few hours. Then Paul closed the old thread where much of this post and all the charts were sitting in that thread's browser. I thought that I would loose it all ,especially the charts but the whole lot seems to have copied across okay into this thread's browser (whilst still in "pre-submit mode"). I just hope that all the charts are easy to view (in the quick/move across mode). EDIT: they seem to be ok, phew!

TIME TO TAKE A STEP BACK, ASSESS THE VERY MIXED SIGNALS AND TRY TO MAKE SENSE OF IT ALL

Well, they say that 24 hours is a long time in politics and for all of us model watchers 24 hours can sometimes seem to be an eternity when the output can swing quite widely from run to run. In this post I will try to address some of the comments from a few of our most experienced and well respected posters and examine many of the conflicting issues and "possible" changes in the background signals that drives all the model output (usually with a time lag of at least a few days). As I always remind everyone, I am definitely not an expert and I only have a limited understanding of the key teleconnections. I use the simplest terminology just as much for myself as for the majority of readers on this forum. My strength is my study of charts and interpreting what we are looking at and how they "might" evolve, which I have been doing for over 56 years since the age of 8. Over the years, I have also read many papers on various aspects of meteorology but I am the first to admit that this knowledge/understanding/experience is not nearly enough on its own and I'm fully aware of my limitations. Nevertheless, I will attempt this overall assessment and I will have no problem with any one "respectfully" commenting on or correcting anything that I say (with at least a short explanation).

Most of you who read my posts will know that I'm very much one of the "coldie" brigade and I do spend a lot of time searching for possible changes to colder patterns. Some might dismiss this as "ramping" but I always try to provide a degree of balance and often use "CAUTION" statements to put what I say into context. Quite a few (certainly by no means all) of our much more experienced posters also have a strong preference for cold (and snowy) evolutions and they can sometimes get just as excited or as disappointed as anyone when they see possible changes in the background signals and the output. Most of them and the professionals do try to manage their expectations and still provide realistic and honest assessments. We must all exercise considerable restraint - so no throwing the toys out of the pram, no blaming anyone for simply "being the messenger" of any disappointing news and definitely no ridiculous arguments about dismissing the relative merits of teleconnection science (there is a tiny minority on here who often express highly disrespectful and nasty comments and criticising the post contents can be just as bad as criticising the poster especially without any real evidence to back it up (not just conveniently quoting several sentences completely out of context which almost always misses the very caveats and caution that was expressed elsewhere in the post; I do wish that the moderators would clamp down on this dreadful practise - otherwise we will lose some of our very best and most valuable contributors). Having said all that, I still remain pretty bullish about the overall prospects for this winter (may be just timing issues - more on that shortly) and the output for the period just after Christmas looks much more interesting (for coldies) than it did only a couple of days ago. 

When we see the likes of @Steve Murr start to tell us that any signs of a decent cold spell in January have all but gone we should sit up and listen. When one of our professional and highly respected posters @Glacier Point explains why things have changed we must pay even closer attention. Then we have some highly experienced members who mostly post on the stratosphere thread and rarely post on the model thread. So when, for example, we see @KyleHenry bothering to take the time today to post on here we can only show our appreciation and pay careful attention to what he says. Now an amazing coincidence - just as I am writing this (currently 1110) @Tamara has posted. Regular readers of my posts will know that I often refer to Tamara as I have the utmost respect for her dedication and how she explains how the background signals are behaving. Just as she "always" does, I never forget to stress that anything that she says should not be taken out of context and the downside risks must be taken on board. I urge any of you who have not yet read Tamara's post to study it very carefully indeed. She again stresses the uncertainties and describes what "might" go wrong as well what "might possibly" still fall into place (she stresses that bit in italics but with caution) . It is a terrible shame that the tiny minority that I already referred to above are responsible for Tamara deciding to take a break from this forum. It happened last year too. I will just say publicly how sorry I am that it has come to this and of course I wish her a Happy Christmas.   (I rarely use these but a one off one today to cheer up Tamara and all her supporters).

So, no more bursts of unwarranted emotion from anyone please (let's have some Christmas spirit). Now on with my post. I know that looking into deep FI can sometimes be about as reliable as picking the winning lottery numbers but there are important occasions when we need to get an idea of future "possible" pattern changes and if a new direction might just be starting to be sniffed out in the distant model output. As always, remember it's the background signals that drive all the model output not the other way around. Unfortunately, we only have the GFS and GEFS models going out that far (plus the extended EC46, monthlies and ens etc). Knowing that the 6z runs would be coming out while I'm writing this, I deliberately saved the 0z for making an important comparison. I had noticed several comments that the GFS 0z operational run was completely out of kilter with the GEFS control, mean and ensembles. This does not mean that it's wrong, of course. In fact it can be the Op run that latches on to a possible change prior to the other output. Update: in fact we now have the 12z rolling out but this comparison is purely to make my point. So, let's have a closer look:

T+384 0z Run:

              GFS Operational                                            GEFS Control                                                  GEFS Mean Run                                             GEFS Ensemble Panel 

                                                      

The GFS operational run does show a somewhat strengthened and rather more organised PV but not particularly vigorous. There are no Arctic HPs and and only a "Cold" faux Greenland HP. There is still a little amplification. HP has built north-eastwards from southern and central Europe towards north-west Russia (not a Scandi HP but equally not a flat pattern with a "Euro-slug" at the D16 stage). The GEFS control is more amplified with HP drifting into Scandinavia and still pretty high pressure over the Pole. The mean (caution: remember this averages out all the 20 ensembles, the op and control runs and can be misleading) actually has a broad band of HP extending from central northern Canada, through the Pole and across into Siberia/northern Russia. The average depth of LP is very weak  and far from a raging PV. There is an even bigger spread in the ensembes. Anything from a stronger PV to a fully split PV and a cut-off proper Greenland HP - for coldies is that as close as we get to something very special? There is a larger group of ens with disrupted PVs. So, yes the op is out on its own with a stronger PV, the mean paints a very different picture and many of the ensemble members showing continued disruption and the control run is somewhere in between. All this being clearly reflected in the 850s chart below (unfortunately, it was too late to get the 0z surface temp and pressure ens charts as the 6z ones were already showing).

    GEFS Ensembles - London:                     850 Temperatures            

                                                                       

Moving on to the 6z run, let's look at the same charts and then look for any possible trend (far too early to draw any meaningful conclusions but just a possible indication).

T+384 6z Run:

              GFS Operational                                            GEFS Control                                          GEFS Mean Run                                      GEFS Ensemble Panel 

                                               

Well, seeing as the 6z run was still rolling out when I was writing up the 0z analysis, I was pleasantly surprised. The GFS op run has back-tracked to some extent although it is still one of the warmer runs (see 850s below) but it shows only a moderately stronger PV and much higher pressure over the UK and ridging through southern/central Scandinavia, northern and north-eastern Europe and right through to north-west and north Russia. Is that merely a GFS "dead cat bounce" or are they dropping the hints of a much flatter pattern set up? The GEFS control run still shows WAA through Alaska and towards the Pole with HP there and some HP in north-east Russia. The mean (which would never show a split PV unless almost all the ens showed one and in very similar positions) still has HP from central/northern Canada, through Arctic, across the Pole and right through to northern Russia and Siberia. Now, we are back to an even better set of ensemble members. We have three with fully split PVs through the Arctic, one north to south but two more east to west. Steve Murr alluded to the latter pattern being of interest and dismissed the former but I will focus on this below as I have several important points to make. The ens charts below show the spreads nicely. The 850s are not indicating much in the way of upper cold with only a few members below or well below 0c. The op and control are amongst the warmest towards the end of the run. The mean surface temps are mostly around 5c with some of the ens up to 10c and some closer to 0c. The op is around the highest at the turn of the year but falls away thereafter. So mostly temps look close to or slightly below average. With warmer 850s and rather lower surface temps mostly shown, that might indicate some higher pressure around (with some surface cold). The op and control have us under HP (as mentioned above) around 1030 mb but there is quite a spread with the mean closer to 1016 mb.

  GEFS Ensembles - London:              850 Temperatures                      2m Surface Temperatures              Mean Sea Level Pressure

                                                               

Overall, if this run was any indication to go by at all (very unlikely to be accurate) this would be far from very unsettled and very mild by January 5th.  Before some of you think that this exercise is a complete waste of time (some will of course!) let me remind you why I bothered to show it. Firstly, I was looking for any very early hints of the GFS picking up on us moving away from the possible change to a colder regime - just as I was looking for any pointers supporting this change. Only on this very scant evidence, one might say that the GFS is pulling in both directions! The op in the 0z and the op and control in the 6z are amongst the warmer evolutions but the mean, supported by many of the ens charts, suggests otherwise. As we always say, far more runs needed (and you will have had a chance to comment on all the 12z output when this post goes live) and will the output from the other models start to move away from the WAA and HP into the Arctic pattern in the middle term (say D7 to D10)? This gives an idea of what to look for in the longer term and then the route taken by all the model output towards or away from that destination. We will need to look at many more runs and as @johnholmes often reminds us, it is often a good idea to compare like with like and not the changes in every run (eg: every 24 hours with the same run each time like the 0z or every 12 hours with say the 0z and 12z runs) as this often achieves better consistency with the same new (latest) input data becoming available in time for certain runs. CAUTION: remember the lag time for the models to start factoring the possible changing background signals - this can take a few days. Unless those signals improve, there may well be some significant downgrades in the extended model output. I am still taking my more optimistic approach and some of my points below "may" address a few of the issues.

Timing Issues:

If FI is unreliable then mid to late January is even more unreliable!  We need to turn towards the broader background signals. When the majority of our specialists (teleconnection including "some" from the strat thread) were talking about a "possible" change to a more amplified and colder regime for some parts (a few weeks ago) not only did most of them mention the downside risks but also uncertainty on just when it might occur and how long would any transitional phase take. I've picked up on this in several previous fairly recent posts. Originally, the period from after Christmas through to early January was mooted as a possible period for the changes to start. The models were late to pick up on this and then we started to see some interesting Arctic patterns merge, initially in deep FI but then quite suddenly into the middle term (D6 onwards) with all the models coming on board eventually. The PV coming under attack is one thing and delivering a cold spell is quite another (again I'll look at this towards the end of this post but I was going to do a current and predicted temperature analysis which will have to wait for another day or two). Might it be a case that there'll be a move away from this pattern change but with a move back slightly later on and we merely end up with a delay to a possible colder regime?. To understand this we need to recognize just what has been happening and, in particular, some of the conflicting signals.

Conflicting Signals:

Our teleconnection specialists and quite a few others have told us how this could be a "winter on a knife edge". I'll list some of the issues here (with the simplest of comments):

1. The ENSO state - La Nina conditions but not a particular strong one would usually signal a colder run into winter with early blocking, giving way to much flatter patterns in mid-winter as the PV goes through its typical strengthening phase and the jet stream usually gets to around its strongest at this time of the year. Then it looked like a more unusual Nina signal with it becoming an east Pacific based event (the colder currents and upwellings in the east and warmer currents in the west, perhaps allowing for a more extended period of blocking; then very recently a suggestion that the La Nina might be strengthening and moving into its more usual central Pacific position with a more typical La Nina winter impact - then back to timing issues of whether the impacts of this could take hold before or after an increased amplification (favoured until recently) despite a strengthening PV and jet stream (the latter "could" still be the case).

2. The various oscillations and how they interplay - we have an eQBO, tropical forcing, the GWO, angular momentum (possibly a less favourable phase); the MJO might be moving into more favourable phases to enhance HLB patterns. There had been talk that the MJO signature may have been masked by other signals. Will it move quickly or slowly on through the key 7.8 and 1 phases and at a decent or lower amplitude, will it actually play a major role in assisting or is it less relevant right now. I have just noted another excellent post from @Singularity and a similar comment from @nick sussex who both both that there may be continuing uncertainty in the progression of the MJO. This could prove to be a very important ingredient down the line. (UPDATE: just read Nick's fascinating post with the NOAA report - possibly encouraging for coldies) It strikes me that if all the ducks fall into a row to assist each other rather than compete that this would make predictions a lot more straight forward! LOL. Just what are the more dominant forces in any particular situation? - way beyond my limited understanding. 

3. The near record low Arctic sea ice build up and very high anomalous sea surface temperatures there. The cause and effect relationship with these favouring split or disrupted PVs (see my post on page 72 of the now closed  9.12.17 winter model thread).

4. Very high Asian snow cover. Judah Cohen has conducted extensive research into this and believes that this combined with the Arctic profile (above) can favour strat warming events (more on this shortly).

5. Solar weather - very low (zero for several months, I believe) sun spot activity, solar bursts expected this week with uncertain impacts.

6. The conditions in the stratosphere and the stratospheric/tropospheric relationship (more below).

7. The PNA -  was positive, briefly negative and was expected to go positive again but has this/will this change? Impacts for favouring amplification and down the line possibly leading to a mid-Atlantic ridge and some HLB nearer to us and/or sending the jet stream further south with a potential for a build of heights to our north-east (might this still be on the cards, delayed or far less likely?).

8. Probably various other factors but I'll leave the list at this point.

The Stratosphere:

As I said at the opening, this is getting way out of my comfort zone but I'll make a few points, some of which I suggested in some of my recent posts. I'm a reader and (slow) learner when I look through some of the highly impressive posts on the strat thread from an array of often highly knowledgeable contributors. I have noted that some of the conflicting signals have been part of the recent discussions. Until perhaps only several days ago, there were indications of warming in some layers (whether a brief early to mid-winter warming or the precursor to a sudden stratospheric warming - SSW). Then there was discussion of whether the changes both warming and cooling were propagating up or down properly through the layers. I thought that the consensus "was" that changes in the stratospheric PV were not imprinting on the tropical PV. Some commentators pointed to a strat/trop disconnect and I thought (perhaps quite incorrectly) that some of the tropical forcing might interfere with the usual processes - again way out my depth here but has this happened or changed recently? What does occur to me is that it can take some time for any reconnection to have an impact through the lower layers and down to the surface. We "had" been expecting a flatter surface pattern for the run into Christmas and on into the New Year and much of the output started to reflect that change. More recently, we have just seen some traces of moderate amplification again in the middle term (say D6 to D10+ period) and possibly beyond. Could this in part be due to some of the earlier amplification signature still embedded in the lower layers and/or could it be due to the MJO being more active than recently recognised and held back for longer in the key phases (7/8/1 or at least the 8/1). One or both of these might be sufficient to produce at least some further HLB and perhaps that build of heights to our north-east and even a Scandi HP. Yes, clutching at straws here. Many posters have been pinning their hopes on a strong warming or even a full on SSW. In a recent post I said that many cold winters have been achieved with little or no warming events. We know from past experience that predicted SSWs do not always propagate down to the surface or they do so in several stages, delaying the full impact (I'm not going to discuss wave 1 and wave 2 or multiple events). Then, even with a strong mid-winter warming or full on SSW, the associated HLB and the expulsion of Arctic cold towards the middle latitudes only sometimes falls into place to bring that cold into western Europe and the UK. The GFS model has been quite consistent with showing strat warmings towards the end of each run, then sometimes bringing that forward close to the more reliable period, then, more recently dropping the notion almost altogether and finally today's 12z runs brings it back strongly. Is this just GFS natural variabilty? I thought that the modelling of stratospheric changes was more consistent than modelling the layers nearer to the surface. It probably is but I assume that occasional unexpected upticks or coolings do crop up. Just how confident are you guys of the current signals and particularly the impacts playing out down the line.    

The Tropospheric PV:

Now I'm much more confident with this part of my post! In my post last week (page 72 of the old thread) and in a number of other posts, I have been monitoring the state of the PV and the Arctic pressure patterns. I produced an analysis looking into just how rare split PVs are. I found several interesting papers (all the links are in that post) which demonstrate how split or at least thoroughly disrupted PVs have been becoming much more commonplace in recent winters and there is the cause/effect relationship with the reduced Arctic sea ice extent and the anomalously high sea surface temperatures there. These events displace the Arctic cold, often to North America but less frequently towards Asia and Europe and only occasionally towards the UK. As these events are seemingly becoming much more frequent (at the expense of the warming Arctic), the UK's opportunities should increase.

I researched previous cold winters using the re-analysis archives and came up with some quite unexpected conclusions. Fully split PVs are actually very rare (probably modelled far more often but without actually verifying). When they do occur they hardly ever last for more than a couple of days. What happens in some winters is that the PV comes under attack from various angles over a period of time. I would not normally disagree with @Steve Murr.as he is so much more experienced than me but my research suggests that the angle of the split may not be the important part of the event. The split is the result of WWA into the Arctic. The warming from the Pacific side through Alaska as shown on quite a few models on successive runs during the last few days, typically produces a cut-off Arctic HP or on the odd one or two even a cut-off "warm Greenland HP. I agree with Steve that this angle of attack may not be the best but I also do not believe that an east-west attack would be either. The evidence (which I can easily reproduce) would suggest that any full split or partial split thoroughly disrupts the PV for a short period but it's the multiple attacks (from any angle) over a few days or several weeks, which disrupt, disorganise, displace and weaken the PV for an extended period. The impacts from this are usually delayed by a week or two. I showed this in some of our notable cold winters. The PV sometimes tries to reform (probably due to the natural seasonal climatologocial strengthening processes) but then comes under further attacks. Disrupted PVs were a lot rarer back in the 1960s  and 1970s! Quite a few cold winters were achieved with quite strong PVs. Even 1962/63 only saw occasionally disrupted PVs.. 

Turning to this winter and the currently modelled patterns. If we can get these patterns (for only a week or so away) to verify, then we might be able to disrupt the PV sufficiently before the anticipated strengthening. This could have significant affects down the line and might really put the spanner in the works and interrupt the more natural climatological patterns that the changing background signals may now be indicating. So, I will continue to focus on the Arctic charts and monitor what is going on. This and the MJO behaviour may be at least two factors that do confound some of the expert opinion. If this winter is still on a knife edge, then perhaps I've just sharpened the knife!

That's enough (or too much) from me for now!  

 

  

Edited December 21, 2017 by Guest
Check charts + correct typos

[bluearmy]

34 minutes ago, northwestsnow said:

By day 10 the euro high looks like its going to be very hard to shift Feb-

Still, i will take any positives at the moment (aside from NAO  obv)

Apparently not according to the latest eps  ....... of course, looking at the eps spreads by day 10, the euro high may not even exist at that point anyway. The eps looking particularly troughy this evening and eventually dropping into Europe though at this timescale the clusters will reveal the appetite. The previous run looked very euro high leaning around T300 so not sure what to take from this mean which heads the other way as the run progresses 

[northwestsnow]

7 minutes ago, bluearmy said:

Apparently not according to the latest eps  ....... of course, looking at the eps spreads by day 10, the euro high may not even exist at that point anyway. The eps looking particularly troughy this evening and eventually dropping into Europe though at this timescale the clusters will reveal the appetite. The previous run looked very euro high leaning around T300 so not sure what to take from this mean which heads the other way as the run progresses 

Must admit i was very very very suprised when Feb posted about the Ex eps-

I'd sure like to know how we would get to a position of Euro troughing looking at the day 10 mean..

 

[Man With Beard]

Possible snow event for 28/29th December is showing on most individual ECM ensembles. Mostly for higher ground Midlands northwards, but a couple also bring a snowfall to SW England (highish ground) on the 27/28th.

Onto matters further out: I haven't seen the ECM D15 mean this evening yet, but I have looked through about 30 of the ensembles - and all I see for the UK is variations on a westerly theme, with the odd random run going for something different. Nothing to hang cold hopes on really. Not too different from the GEFS at that time either.

Had a look at the D10 ensembles and again, troughing addicted to Iceland on both GEFS and ECM ensembles - so a westerly theme at this time too.

One bonus though is that intense storms don't appear to be developing in our vicinity on many runs.

 

[knocker]

Although tonight's NOAA, GEFS and EPS anomalies are not in complete agreement the consensus is no significant divergence from a continuation of the westerly upper flow and thus portending unsettled weather with temps varying around the average as different weather patterns become applicable in the mobile pattern  So this obviously does not rule out some transient wintry episodes.

Anyway upstream in the 6-10 day period some disagreement over the Alaskan ridge but probably it drifting west and becoming a cut off high cell, but still tending to ridge into NW Greenland, as the Canadian vortex lobe adjusts back to it's usual position Thus still a trough in the north east N. America with a strong jet running around the south of it across the Atlantic to the trough in the vicinity north of the UK associated with the secondary vortex lobe around Franz Joseph Land, I suspect the presence to the N/NE of the UK of this upper trough coupled with height rises in the east may complicate the surface evolution a tad with eastward movement becoming restricted. Anyway some thing for the det. runs to sort

In the ext period the Alaskan ridge/Siberian high cell, virtually loses it's identity as the vortex slips back into the fold but still the strong jet running east south of the trough. Downstream the influence of the secondary vortex has waned and the trough is now in the Iceland area as an extension of the Canadian vortex thus probably a more straightforward westerly flow over the UK and remaining unsettled. Usual caveats apply.

Edited December 21, 2017 by knocker

[Man With Beard]

4 minutes ago, FiftyShadesofWine said:

The ECM ext eps have been crap so far all Winter. Flip flop every day,night...their consistency is as good as the CFS.

I think they have been very good, actually. All through November they churned out a majority of blocked runs to the north or west, and what did we get? Blocked to north and west. They went AWOL for a couple of days at the end of November where there forecasted a return to average conditions too soon, but shortly after they correctly nailed on a renewal of north Atlantic amplification for the 16th-17th December extremely consistently from two weeks out and correctly called the end of the cold period shortly after, again from two weeks out. Since about the 12th December, they have been forecasting strong troughing close to the UK between Christmas and New Year with just enough potential in the pattern for a marginal snow event and, guess what, it is now the 21st December, 9 days on and they are still forecasting this for the same period.

Actually just recalling what has happened, they've been better than good in the D10-D15 period - they've been brilliant. I've followed them avidly since the start of November and they've rarely led me down the garden path in either direction. 

[Daniel*]

25 minutes ago, northwestsnow said:

Must admit i was very very very suprised when Feb posted about the Ex eps-

I'd sure like to know how we would get to a position of Euro troughing looking at the day 10 mean..

 

Really? Azores high displaced to south-west low heights in situ over NW Europe. Outlook looks remarkably wintry for the high ground of Scotland...

 

[summer blizzard]

Both models appear to be having issues with the handling of the Arctic heights in around a week or so. Both models agree that the increase in heights will push the vortex onto our side of the hemisphere but the GFS goes flat out zonal with a raging vortex whereas the Euro maintains a hemispheric split with obvious potential down the line the next time the pattern shifts.

 

[northwestsnow]

18 minutes ago, Daniel* said:

Really? Azores high displaced to south-west low heights in situ over NW Europe. Outlook looks remarkably wintry for the high ground of Scotland...

 

Shows a flow off the Atlantic?

As posted above by knocker..

Edited December 21, 2017 by northwestsnow

[bluearmy]

39 minutes ago, FiftyShadesofWine said:

No they've been poor, since I gave Feb the link, the flip flopping is awful...iv stopped posting them, they fluctuate from troughing to ridging far too often. The 10-15 period lately has been way out if you study them morning an evening. Remember they showed fantastic Scandy highs for a while....Scandy highs, we have nowt.

 

i have never seen a scandi high in the eps .....  actually possibly never ever thinking about it !   Sceuro ridge last year but never a true cut off upper ridge over scandi. Not never. 

Im with mwb - the extended eps are are tremendous aid. The fact tha we now see the Icelandic clusters make them even more useful. From my memory  they have flipped twice this last eight weeks  - one occasion when they dropped a euro trough/low anomoly as they approached day 10 and the other when they found a one approaching day 12.  Both times they were right to flip as the solution then verified. 

Edited December 21, 2017 by Paul

[bluearmy]

4 minutes ago, northwestsnow said:

Shows a flow off the Atlantic?

Not particularly impressive but 3 1/2 days later shows this. If it's right, you would expect a sig cluster to be sharper 

[northwestsnow]

1 minute ago, bluearmy said:

Not particularly impressive but 3 1/2 days later shows this. If it's right, you would expect a sig cluster to be sharper 

Cold rain...maybe aside from north scotland..if im reading the DAM lines correctly ..

[fromey]

10 minutes ago, bluearmy said:

Not particularly impressive but 3 1/2 days later shows this. If it's right, you would expect a sig cluster to be sharper 

If I’m reading it right the 528 dam is just on the north coast of Scotland so cold rain for the majority 

[feb1991blizzard]

ECM 46 is just about as dyer as it can get.

[Longtimelurker]

2 hours ago, Paul said:

This isn't specifically aimed at you, but way too many are falling into the trap of expecting a silver bullet when it comes to forecasting - short or long range. The MJO is an indicator, one possible signal to use in amongst 100 others.

It's never been and never will be the single answer to the weather forecast, so to say it's useless because it can be over-ridden or muted is pretty much the equivalent of saying using air pressure in forecasts is useless because you expect it to always be sunny when pressure is high. If forecasting were that simple, we'd have next to nothing to discuss in here!

Weather is complex, rather than railing against the complexities and difficulties of forecasting, i'd recommend embracing it, and trying to learn why things over over-ridden, why some indicators fair well sometimes and not at others, that's the challenge and interest of it all. Failing that, there's always the moans thread  

I never said it was useless so don't put words in my mouth. I'm not expecting a silver bullet either. My point is it gets mentioned more than anything else when it comes to signals on here and almost always some excuse is made for it when it doesn't pan out as expected, a wishy washy non descriptive one at that . I'm not railing against anything just pointing out the jibberish and your post would be well suited to the moan thread. How dare anyone on here question background signals. How very dare they. 

Edited December 21, 2017 by Longtimelurker

[northwestsnow]

5 minutes ago, fromey said:

If I’m reading it right the 528 dam is just on the north coast of Scotland so cold rain for the majority 

Yep...thats as wet as an otters pocket for the vast majority..

[northwestsnow]

5 minutes ago, feb1991blizzard said:

ECM 46 is just about as dyer as it can get.

Doesnt tie in withe euro trough on the ext eps then!!

[bluearmy]

3 minutes ago, northwestsnow said:

Yep...thats as wet as an otters pocket for the vast majority..

It's a mean chart at 13 1/2 days range. It's nothing more  than an indication of the likely upper air flow and potential anomoly location. View in conjunction wit the clusters in five minutes.  I think you should give it a few days to consolidate before making a forecast for jock's back garden !!!

and yep, the ec 46 looks pretty dire, especially weeks 3 and 4 (not that bothered re 5 and 6 anyway). Awaiting the global view to put the Icelandic into perspective 

[feb1991blizzard]

1 minute ago, northwestsnow said:

Doesnt tie in withe euro trough on the ext eps then!!

No, this is derived from the 0z run though, so what we need is that the 12z has picked up on a new trend and that continues on the overnight runs, thus rendering that poor EC46 run as irrelevant and that xmas days run will then flip.