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Singularity

Pro Forecaster / Meteorologist
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Everything posted by Singularity

  1. Singularity
    If there is a genuine downwelling of anomalies from the stratosphere in the works for next week, I can see why this is seriously messing with the models, as the alignment of tropospheric anomalies that this encourage is offset from those encouraged by tropical forcing. Any over or underestimation of either of these two processes will have major ramifications going forward. Today the broad trend appears to have been toward more tropical and less stratospheric, but this could well reverse without much warning. There are also knock-on effects in terms of further vortex perturbation, as more tropical forcing encourages a Pacific-Siberia ridge linkup that maintains WAFz when otherwise it subsides.
  2. Singularity
    Well, it all got a bit messy across N. America and I was thinking what a shame that was, but now GFS has gone and decided that a very strong poleward push of heights is on the menu after all. Pretty cool idea I guess - but I still prefer the stronger first attempt that UKMO 00z/12z and ECM 00z depict
  3. Singularity
    Into a critical period these next few days as we find out whether the tropical forcing will be sufficient to keep the N. American ridge-trough sharp enough that the Canadian-Atlantic vortex lobe remains more Canadian and we get to see it kept independent of the Scandinavian lobe, possibly with small LPs breaking away and moving across to the S of some degree of ridging NW of the UK. ECM 00z is the closest run I've seen so far from the more credible models, with UKMO looking ripe for similar progression as of day 6. GFS continues to suppress the tropical forcing more via stronger interference from the La Nina oceanic state in the Pacific. Chances are this is the forcing being overblown by bias relating to the GLAAM negative bias, but I'm wary of calling it out at this time... things are so very poised, but a poke from the wrong direction and we'll fall down on an unpleasant side.
  4. Singularity
    Too early to draw conclusions for sure, but the trend toward the Pacific cross-polar ridge has so far today been pretty major. Perhaps a case of gradually starting to smell the coffee... can only wait and see! Serves to make the later stages of next week nice and mysterious .
  5. Singularity
    LP no longer running over the Pacific ridge on day 6... brings the 00z GFS close to getting a wedge of higher heights in between the Canadian and Scandinavian vortex lobes on day 7. By day 9 the situation is akin to yesterday's 00z ECM run but then the poleward ridging on the Pacific side is bulldozed and the run loses interest. ECM 00z has made similar progress on the Pacific side but has also dropped momentum on the Atlantic side so much that we lose out on the consolidated trough over Scandinavia which then means a longer wait for the major trough to get east of us. Oh the irony! Wacky finishing pattern though and with the vortex being subjected to a lot of peripheral wave action.
  6. Singularity
    The mean is longer reaching near 3 SDs from zero (the circle is 1 SD) for any model, with GEFS having reduced the amplification a lot in a single day and ECM to a lesser extent. The stronger the MJO activity in phases 6-8, the more amplification to the Pacific pattern is likely, and so the more poleward the ridge from there is likely to go in the 6-14 day range, and as a result, the better our prospects for amplification in useful places later in time. Hopefully an over-correction... by 4 pm tomorrow the next update will be telling.
  7. Singularity
    When ECM took that low over the ridge from the Pacific on day 6, it was a genuine facepalm moment, either for the modelling or the actual route that we'll be following (which it is, remains to be seen!. The model managed a partial recovery afterwards as another round of amplification sent the ridge back poleward, but by that time we're left with the 2009-style road ahead of us whereby heights attempt to build N from Europe to Scandinavia and then NW from there, leaving us on the eastern periphery of a broad Atlantic trough and under threat of large rainfall totals plus some strong wind events. What with the MJO projections suddenly less amplified in today's update, there is some genuine concern regarding finding a way to beat down the more mobile spell this side of New Years. Could be worse though; with a different teleconnection state, I could have been saying this side of mid-late January!
  8. Singularity
    UKMO and GFS seem broadly similar at this point (day 5) but there is a critical difference; GFS has a LP system departing the Pacific vortex lobe and heading across to the Canadian one, while UKMO does not. A day forward and UKMO is doing some fine vortex assaulting via the EPO ridge, while GFS has 'rounded-off' the northern limits of it while also keeping that limit further south. The more rounded ridge shape sends cold to the SE or even ESE rather than SSE or S, increasing the thermal gradient in the western N. Atlantic with unpleasant consequences unless you're a fan of wind and rain. If GFS is wrong about this ridge shape then it's making all manner of incorrect suggestions regarding the pattern for late Dec and early Jan this year. The 'pointier' ridge of the 12z UKMO and 00z ECM runs sets us on a path toward a renewed split of the vortex with one lobe over N. America and the other over Scandinavia or Europe (or a bit of both). The 00z ECM was almost getting there as of day 10. Hopefully we are seeing a case of GFS' typical NE'ward bias with LPs resulting in that Pacific low behaving in a way that won't actually transpire. In fact the 12z has two potential cases of this happening in quick succession so there's a lot to play for! Best outcome I can think of going forward from day 6 - for the quickest cold weather results - would be if we had something akin to UKMO but then the LP to the N. of Florida engaged with the cold air pushing south toward the SW States and deepened into a large low while stalling out over the NE'rn US. The CFSv2 shows us that it's unfortunate we're not seeing more amplification retained days 5-6 i.e. akin to the 00z GFS of a couple of days back; it's the combination of that and a very pointy Pacific ridge (VPPR to save future writing space... ) that leads to such an interesting outcome by days 8-9. Sometimes the model is good fun .
  9. Singularity
    Worth noting that we're moving into a pattern which GFS/GEFS is known to perform particularly badly; a mean trough in the N. Atlantic but with ridge building trend signals both across the Arctic and across NW. Eurasia. This being in large part due to how critical the intensity and broadness of the N. Atlantic trough is - two characteristics that the model (more than most; but others do have similar faults) tends to take too far at more than 6 or 7 day's range. Much of the remaining error relates to the rate of change in Arctic heights and their orientation, which is a great bother for all of the models. With this in mind, I suspect wave-2 potential is being underplayed. How much, I'm not at liberty to speculate .
  10. Singularity
    Yes... the Pacific ridge is picked up a bit better on this run although it still has some work do to in this respect. This brings the run closer to keeping the vortex lobes separate in the 8-10 day range but it's unlikely that a scenario can be reached in which low heights don't transfer across at all from Canada. Instead, the process to look out for is the ridging from the Pacific side interfering with the Canadian lobe, triggering a collapse with some low heights escaping toward Scandi or Europe while the rest gets held back in the western N. Atlantic or across N. America (former more likely this time around, due to the shifted tropical forcing location and intensity compared to those of the past fortnight). GFS, being GFS, will likely have a hard time capturing this interference and collapse, but to be fair to it, other models often struggle as well in such situations - just look at the 00z ECM for example. Not that a wholesale transfer of a deep trough can be ruled out, of course - it's just that the outcome I've suggested seems more plausible to me at this stage. I could well be wrong on this (I'm only human, after all...). Into lower-res and GFS is also making a mess of the Arctic profile... again, which is probably down at least in part to the low-GLAAM bias that becomes most evident when the GWO is cycling around with GLAAM spending a little time in what is expected to be only weakly negative GLAAM, but is nearly always modelled by GEFS/GFS to be more negative. Let's see if it can recover the situation at least up there as per the 06z - that it did so on that run was a good sign I believe that the tropical forcing mechanism has a good chance of coming through at some point in the next few weeks (most likely next two weeks).
  11. Singularity
    Always an issue when the models are opting for the most efficient energy transfer possible and producing very large, intense storm systems as a result; they produce regionally flat-looking outcomes even when the broader-scale pattern is nicely amplified. It'd take a few days to push such a broad trough southeast and get back to a colder regime from the ECM day 10, but I question whether there will really be a large, deep trough to begin with; often enough I've seen these fail to come around, with the actual outcome featuring multiple smaller lows zipping across. In this case they'd do that and then merge with a trough to our NE, in a similar fashion to the past few days. It doesn't sound that exciting for southerners I know, but this is why the Scandinavian high signal is of interest longer-term (v. late Dec/early Jan) as it can potentially convert the polar maritime setup into a polar continental one, which works much better for those who've missed out so far this winter. It's tricky I know to get the sense of balance having already come so close to low-level snow in the far-south this winter. Fact is, snow to below 200 m asl in that region is very rare indeed in December - as I know all too well!
  12. Singularity
    Better Pacific ridge than GFS; sharper with more of a pull on the vortex back into N. America. In theory it should not end up as flat as GFS did. Potentially not even close, although that's probably pushing it for within the 10-day range.
  13. Singularity
    GFS past day 8 or so makes little sense to me from a teleconnections perspective as it removes the poleward ridging that's meant to set up in response to the MJO forcing. Very strange, that. This seemingly extreme torque event in phase 8 may be the culprit. The t+0 diagnosis is often overblown though - for example yesterday's point was originally almost as far across in phase 8 as today's supposed observation - so if this is the troublemaker, we may see a marked improvement from GFS again tomorrow. Hopefully. Alternatively, having lost it's very fast route to disrupting the push from the west, the model may simply have reverted to getting very carried away with the +NAO pattern via climatological bias. It shouldn't inspire as much dread as it has been doing for some of late, though. Those who state that once a +NAO establishes it can be hard to take down... well. it depends on the background forcing - if it's sufficient to force amplification, the +NAO can break down very swiftly. We've seen in the past few months just a scattering of short-lived +NAO spells for this reason. As a final note for now - phase 8 of the GWO is typically associated with some of the most wildly fluctuating model output in the mid-longer range. Chaos beckons!
  14. Singularity
    Interesting and yet... highly contradictory to the points made by A-Team in this forum thread; https://forum.arctic-sea-ice.net/index.php?topic=2141.450 ... which make a good amount of sense to me having followed developments closely these past few years. This could mean that we’ve either already had the freshwater flush, or that it moved differently or even just stagnated in place and slowly modified (during occasional storm events mixing the layers at least a little) due to anomalous into-Arctic currents these past two years. I must stress ‘could’ though; reliable measurement of the gyre is not as straightforward as I had once hoped it would be. p.s about time we switched to a freezing season thread I should think?
  15. Singularity
    The progression we're seeing the models explore (somewhat inefficiently perhaps, but getting there) is one in which the Canadian vortex has a window in which to venture towards Europe via Greenland, but then comes under attack from upstream changes with the Pacific ridge heading back poleward and initiating a buckling of the jet pattern that should encourage the vortex lobe to come apart a bit, with some getting pulled back into N. America while the rest either heads into Europe (as either a large organised trough as 00z ECM tries for or a smaller one following trough disruption as per the 00z) or digs south in the middle-N. Atlantic. The former resembles our predominant pattern of Nov-Dec so far, but tweaked to allow for more the way of Scandinavian height rises as a follow-up to the trough dropping in. The latter is a different path, more like we had to go through in Nov 2009 - and laden with the risk of some mild, wet weather while we wait for ridging to make its way sufficiently north from Europe to turn the tables in favour of cold. This manner of evolution has a habit of drying out just as it turns cold enough for snow, though. GFS 06z is very much the latter scenario. This setup is also easy to tilt unfavourably with a bit of climatological bias and/or over-deepening of troughs, which I believe explains some of the less than inspiring ensemble behaviour of late. It is for reasons like this that the festive period has a valid stormy weather risk, but given the (at least) equally plausible alternative scenario of a trough setting up over Europe again, I'm not inclined to expect a windy washout route at this stage. GFS still managed to get quite close in the end on a hemispheric scale - a nice interpretation of the Pacific-Scandi relationship, shame about that dartboard low!
  16. Singularity
    Can't speak for UKMO as its MJO output has been missing from these plots for some time now, but the ECMF prediction has increased in amplitude with each of 5 new days in a row now, taking it ever closer to the enthusiastic GEFS. This isn't the first time this season the model has been correcting toward GEFS either, so this is likely a factor in those periods of strangely flat output relative to the other models (or even in general, in this most recent case) that have been observed. With the Alaskan ridge it really is critical to get it sufficiently poleward enough to flip the switch to easterly potential from relentless westerly dross. Not sure why GEFS have so many members (13 or 14 out of 20; one of those only just) going in the zonal direction given the MJO projections. Could it be a resolution thing... or a sign that even with such MJO amplitude, victory is far from assured...?
  17. Singularity
    The increase in heights not only over but also out to some way WNW of the UK from ECM, coupled with the 00z EPS spread covering it, does suggest to me that GFS has once again played the trend-spotter although the transient northerly prior to Scandi high is beyond what I have been expecting so it will be interesting to see if even that bonus round manages to come through in some shape or form.
  18. Singularity
    Agreed - on balance, a general theme of strong ridging across the UK makes the most sense as our ‘holding pattern’ while awaiting sufficient upstream changes, which do tend to take more than one bite of the cherry when it comes to Scandi Highs. Encouraging to see GFS finding a route despite the less optimal day 7-9 progression than the 00z produced.
  19. Singularity
    Indeed BA (I believe Netweather should include the GEM output to day 10 in their chart viewer, at least for entertainment value ).
  20. Singularity
    As trends go, this is a good one from GFS today, and with the tropical forcing helping with amplification plus the dishevelled vortex state, it does seem very credible to see an Alaskan/Aleutian ridge punching well into the Arctic circle with the Canadian vortex lobe shifting W and/then S.. and so on.
  21. Singularity
    Indeed it is, and I'm not seeing any particularly troublesome stratospheric behaviour at the moment, well not consistently in model projections anyway. Still signs of a strong warming event, in fact, although more uncertain since the modelled tropical forcing started dancing about. The ENSO state is tied into the MJO and GLAAM behaviour, with the eastward bias of cold anomalies allowing the MJO to move further east than would be seen during a canonical La Nina and so send GLAAM on the rise. This has led to interesting developments in similar historical years as discussed by GP (for example) at times these past few days and weeks. The Met Office now putting back renewed HLB chances to early January does make me wonder if something's lurking in the shadows, though...
  22. Singularity
    Quite the turnaround from the models with the dip into the 'circle of death' almost eradicated and much better amplitude into 6/7 from GEFS and 7/8 from ECMF. Both are good for boosting HLB starting a week or two later in time from onset... so around 10-18 days from now. Question is whether we can achieve the 'almost' situation of recent GFS runs in the 7-10 day range, or end up with more work needing to be done to rescue things as per recent ECM runs. With the near-term reduction in MJO forcing removed, there may even be additional amplification on offer in the 6-10 day range so that's something to watch out for. Maybe.
  23. Singularity
    So about 10 of the last 24 hours have brought temps of 1*C and mostly rain with a bit of sleet here and there. Given a few reports of snow to the south of me at what appears to be similar or even lower elevation, it appears all I need is a bit of added intensity to the precipitation - but the radar is so messed up this morning that I can't really tell what's coming my way. I can see these heavier pulses moving through London but then there's a cut-off not far to the SW beyond which it all looks light. Which is the real deal? Then there's the extremely dodgy Dean Hill radar cutting a hole in the observations. It's all guesswork going forward! Must say though, this has been in the top 3 most miserable spells of winter weather I've had to endure this past decade.
  24. Singularity
    Very impressive looking storm to the SW on IR satellite... hopefully it won’t intensify faster than expected having absorbed the weak secondary low several hours ahead of schedule, as that could bring more in the way of milder air around the circulation... although if the convergence line to the N was able to hold its ground that could simply serve to increase precipitation intensity while cold air feeds in from the NE... hmm yes I see why MWB considers this one of the trickiest forecasts in many a year!
  25. Singularity
    Worth noting that Met Office only speak of sleet below 100 m - although whether this becomes void if precipitation is heavier, I'm not sure. It hasn't worked today until very briefly at the last minute (before it all cleared up) but the parameters look a tad more favourable tomorrow.
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