Mike Poole

Up she goes! T234: Of course, the real story is the movement of the vortex, to our NE!!

I guess we are only just approaching crunch point on this run, here GFS 18z T192 v 12z T198: You’d have to say the pub run is pushing the vortex away even faster than the 12z…where will this one go…

Yes, agreed, and actually the 18z has higher heights across Scandi than the 12z, T156 v T162 12z: But ultimately this cold is going to have to come from the north, so the low heights into S Europe are also very important - better on 12z. Plenty of the run to come though.

Whatever it is the pub run will have had a lot more, I think . Look with the run coming out, I think we just need to see something that is vaguely similar to the 12z in the early stages, anything more is a bonus, and - if it were to happen - would strengthen the case for a proper cold snap, let’s wee - typo! but I’d let it stand given the 12z, with the 18z let’s see.

I’m strapped in buddy! But can we get back all those so many members who have declared winter a busted flush, all in for Christmas, and no chips left, to persue this chase? Hope so, the pursuit of the holy grail as epitomised by the GFS 12z run begins right now!

Cumulative snow to T48 on the 12z short range for UKV, EURO4 and HARMONIE:

I haven’t posted much in here this year, and it is because the strat seems to have been played out of the game! Not sure why, but still, and we are into January now, the strat and trop vortexes are not connected, see todays NAM plot from Stratobserve (GFS 0z data): Well, yes, while the strats away the trop will play, but it hasn’t benefitted the UK in terms of cold yet. But it must surely be the case also with the disconnect, that there are no trop precursors to a SSW, because they would have to impact the strat vortex. So no chance any time soon of a SSW, I think, maybe something will happen in late winter, but by then it is too late for anything other than ruining the Easter holidays.

ECM clusters, and I’ll cut to the chase, the extended T264+ because that is where the interest is: Well the GFS 12z is certainly represented, it is in cluster 2! But an Atlantic ridge (purple border) regime is yet again the ultimate destination of all 3 clusters, although as we have seen today, not all Atlantic ridges are equal. Cluster 3 looks like a toppler, bit too much of a vortex lobe behind that one. Cluster 1 somewhere in the middle. Let’s count this down folks!!

GFS high res right through the run now, since FV3 upgrade, for anyone who doesn’t know. Compare GFS and ECM T240, it is those small features on GFS that give initial WAA right into Greenland, which the bigger system later builds on, that can’t happen on ECM because of the low which has developed and already gone past the opportunity at T240: But worth watching the GFS evolution from T192 to the end: Weather model porn, that run!

GFS 12z op while extreme, fits within the pattern envelope on the ECM clusters T264+ on both the 0z and yesterday’s 12z. So it will be interesting to see what the clusters say tonight. It looks like there is a window for some proper amplification to the NW post day 10 but the timing will have to be split second, or it will end up being another toppler. It’s one to watch over the next few runs to see if it gains any traction, or (more likely at this stage, of course) fizzles out! Interesting!

Evening all. Just want to show the four T216 NH charts from the 12z: Do not look at the UK - we know that is high pressure of one orientation or another. Instead look at the PV, ECM has it rather slack, GFS has it piling into the eastern side, GEM shows a split with a chance of a ridge up the middle, and JMA shows it encroaching from the NW allowing heights into Scandi. If the trop PV was coupled to such a strong ~40 m/s strat vortex, you wouldn’t see this variability, the trop PV would be roaring away in its preferred location at day 9 and probably day 19 as well. But this is not the case, the PV approaching its strongest around this time of year, is there, but is to some extent free to move or split. This is what we go into the last 2 thirds of January with, and all those of you who write January off, or even write the whole of winter off, or even (1 post) practically write every winter ever again off, are just reacting to emotions. There is no reason at all why a cold spell should not be the outcome of this high pressure spell, that is not to say there will be, it is just that we cannot know at the moment, it is entirely possible for the vortex to be punctured in one of the right places… Finally ECM clusters in the longer range T264+: All 3 clusters suck the high pressure to our NW leaving us in the Atlantic Ridge (purple border) pattern.

It usually is!

Yes, that’s the message I took away from the 12z runs too. With the trop PV not coupled with the strat PV, it is at the mercies of other stuff going on in the trop and will be pulled wither and hither, a point I tried to make last night. It isn’t a golden ticket for UK cold, but what it does mean is it isn’t weeks and weeks of zonal rubbish, in fact zonal rubbish has stopped right now, and instead we see a calm high pressure period (probably cloudy) but with the movement of the trop PV gathering momentum, there are chances of something more interesting down the track.

I cannot understand the negativity in here tonight, I just cannot (although I note exceptions from a few posters!!). While there has recently been a week or so of Atlantic sourced weather, from the comments in here, you’d be forgiven for thinking we have a fully coupled strat and trop vortex and raging jet stream directly across the Atlantic towards us, until the end of winter. Nothing could be further from the truth! My view is this. There is a lobe of the trop vortex over Greenland / Canada, and this will provide forcing from that direction at times. But the trop vortex is in pieces, how many depends when you look because it is a fast moving whirlpool of weather, but for the sake of argument it appears in 3 pieces on the ECM at T216, and an Arctic high floating about (not near here mind) for good measure: Meanwhile in the strat, the zonal mean zonal winds remain strong: And, crucially, the disconnect between the strat and trop vortexes remains really stark, as shown by the NAM plot, with -AO down here and +AO up there: So what that means is, yes, there is a driving force from the Greenland lobe of the vortex, across the Atlantic, but it is not by any means firing on all cylinders because some of those cylinders are elsewhere! Brings me to the clusters, here in the T192-T240 range: Plenty of blocking there, let’s leave aside whether it is in precisely the place to benefit the UK, the first myth I want to bust is that we are in a period of raging zonal weather. That would equate to +NAO - blue border - and that only applies to part of the sequence for cluster 2. Most of the others have a red border by the end, indicating Scandi blocking of some sort. And in the longer range T264+: Again with that blue border, cluster 1 is the Atlantic one, the other two are blocked. My view is that through January we will see periods of Atlantic dominated weather with wind and rain affecting the UK that don’t last too long, interspersed with rather colder more blocked patterns that also don’t last too long, but giving the wintry interest, with the potential for snow. A SSW is not even in the game until February, so January will be very much trop led patterns. We will see…

Think this one may give a cleaner northerly later, here at T138:

ECM clusters T192-T240 range: Decent support for a rise of pressure to our NE into Scandi, on clusters 1 and 3, 4 also looks interesting, just cluster 2 that we don’t want. Re Tuesday or Wednesday, I’m mainly in the no camp, but just feel somewhere might see a surprise, particularly if any precipitation happens in the small hours of the early morning. But definitely interest going into day 9 or 10.

Well, @Nick F did highlight in his winter forecast the Aleutian high. Plainly here to see on GFS T312, but has been building for a while: Good call (made end of November). But it isn’t the end of the story (it probably would be if the strat and trop vortexes were connected, but they aren’t). The trop vortex is essentially in 2 pieces, and now in the heart of winter, what’s powering up upstream has only half the oomph that it would do in a truly +NAO winter. So this is why we see the regimes other than this -NAO, Atlantic Ridge, Scandi Block, show up on the clusters so often. Provided the trop doesn’t couple fully with the strat (no evidence of it doing so yet) opportunities for cold snaps, as opposed to cold spells, for the UK should occur. We are not facing a 2019/20 zonal onslaught. Happy 2022 everyone. Edit, so wrapped up in trying to make a sensible comment, i completely forgot to mention the very constipated bunny rabbit in the plot above - I must be losing it…

Might it? T90 this feature here? Wedge? Edit T114, probably not now! Very fine margins with this, but the chance is there. let’s see what tomorrows runs bring…

Pub run rolling, interesting this one if it goes towards the UKMO / GEM tonight - I say that because it would be going against its own bias to do so, if the GEM was correct, I would expect the GFS to be the last to see it. ICON said ‘no’ by the way!

ECM clusters T120-T168, and it looks to me (bit difficult to see on these plots) that the UKMO / GEM wedge evolution is in the minority 12 member cluster 3. So a 1/4 chance roughly at the moment.

Yes, it is an interesting and rather surprising evolution that’s popped up on the GEM and UKMO today. Means nothing yet, but I will be very interested to see if it has much traction on the ECM clusters in an hour or so.

Pub run T192: Where we would actually go from here on is a question…it could lead to some interesting outcomes…but I’ll check it out in the morning, night folks.

Pub run T150, normal Atlantic fayre? You might think so, but +60 hours and it might look very different:

My point exactly, Matt! I have never found this tool to be useful, and maybe that’s because I don’t have access to it other than what gets posted here. But it has messed up on two potential really cold potential outlooks in the last few years now. I’d rather take up the study of tea leaves.

Fair enough, but for me the ECM 46 timeframe falls between two stools, that which it is possible to predict starting from T0 with the op models, and that which it is possible to detect (from a model point of view) teleconnections operating on a longer timescale.