Mike Poole

Yes, I agree. Some very interesting contributions today, thanks everyone. (And so much better than the kind of ’I didn’t get any snow so everything's rubbish’ argument that derails the thread.) I have always had the view that Iberian heights in winter were a consequence, not a driver, but it is really useful to have read more in-depth views on this, because it will no doubt be a subject that continue to crop up in winter, if the frequency of these patterns has indeed increased due to climate change. I agree with @Battleground Snow that the MJO predictions are improving. Particularly, the additional data point for 22nd Jan is considerably more amplified in phase 5 than the models predicted it on 21st Jan, so let’s hope that this trend can continue until it gets round to phase 7 or 8.

ECM clusters, nothing of interest from a coldie perspective until T240, so here’s T264+: Signs on both clusters 2 and 3 of an Altantic ridge, and the removal of Euro heights, still not really sure this is gaining traction, seems more prevalent this morning than last night though. Cluster 1 remains flat.

That’s good on both counts. And the strong positive Euro height anomaly disappears around the same time.

ECM clusters tonight, and winter slips further out of reach. T192-T240: 6 clusters, three essentially westerly, the other three develop a UK high, edging NE T264+: Clusters 1 and 2 remain zonal, with Euro heights. Cluster 3 flirts with the Atlantic ridge but doesn’t really get there, cluster 4 develops a weakish Atlantic ridge but that only has 9 members. So a downgrade since this morning, again.

It is difficult to see from the monthly average plots that we see from the seasonals, whether GloSea6 was seeing a moderately blocked signal for the whole month of February or a very blocked signal for the second half only after a meh first half. We have now to hope the latter…

If, indeed, the MJO ever becomes favourable in the first place…

It is certainly dragging its heels! But going off the 46 it is not until w/b 12 Feb that any kind of ridging towards Greenland properly manifests itself.

ECM clusters this morning, T192-T240: Generally a flat zonal picture, apart from clusters 3 and 5 which push a ridge up to Scandi, but it doesn’t hold and flattens again. T264+: Cluster 1 (21 members) shows the Atlantic ridge scenario on which hopes for more seasonal weather depend. The other two clusters maintain the +NAO regime. Just goes to show how once this +NAO zonal pattern sets in for the UK, it is hard to shift, there are, and have been, signs of change but they remain at the tail end of week 2 for now…

ECM clusters this evening, a bit more promise than this morning. Not much in the T192-T240 timeframe: Straight westerlies by day 10 which ever road you take. T264+: Now all 3 clusters show an Atlantic ridge by day 15, most pronounced on cluster 1 (20 members). I thought this was the firm direction of travel yesterday, but the 0z EPS didn’t support it, it is back on now so maybe safe to discount the 0z suite? The models can be grumpy in the mornings .

I think the strat has been very important this winter. Ever since the Canadian warming event. There has been a long period where the trop vortex has been allowed to do what it wants, another year - that could have resulted in an epic cold spell. But as luck would have it, this year, it didn’t. I think there is a lot still to be understood, and maybe research into the strat events this year will shed some light later. But it isn’t all about the SSW that wasn’t in early Jan, nor is it all about the SSW that was but probably shouldn’t have been, just gone. The whole evolution up above has seemed weird.

GEM not without potential at T240. Retrogression underway and nothing too untoward lurking upstream. GFS has at least dismembered the vortex by the close of play. That signal, at least, is consistent. But we are increasingly in need of a bit of luck as we move into February. A commodity that has been in short supply this winter (and last winter…and the one before…etc…)

ECM clusters this morning are pretty grim in terms of potential for a colder spell into February, T192-T240: The idea of a push of heights to the NW continues to decrease, and westerly flow driven by a strong vortex the theme. T264+: And more of the same really, with the idea of a height rise to the NW and retrogression relegated to cluster 4 with 7 members, with cluster 3 showing a watered down version of the same thing. Quite a downgrade in week 2 there from yesterday’s runs, hope that flips back on the 12z. (Note to self, don’t look at the 46 tonight, it’s based on the 0z input data!)

ECM clusters T192-T240: In this timeframe clusters 1 and 3 build a ridge to the NE, while cluster 2 remains generally flat. T264+: Cluster 1 collapses the nascent Scandi ridge to flat. Cluster 2 builds a strong Atlantic ridge. Cluster 3 looks like it might flirt with an Atlantic ridge after the end of the run. Cluster 4 has a decent attempt to ridge into Greenland, falling back to an Atlantic ridge. So the idea of a build of heights to the NW continuing to gain ground in this timeframe, consistent with the move on the 0z EPS.

Different outcome on GFS 12z, but the same big picture point, by the end of the run, the trop vortex has vacated Canada/Greenland and moved to the half of the hemisphere to our east. I just think we are now picking up on a theme, which will leave the door open to height rises in the Atlantic towards Greenland into February.

Thanks @lorenzo, will read the paper you linked to.

I read that blog, but one thing that confused me with that picture, is that the often quoted (on here, anyway) Ural high, Aleutian low combo, as a SSW precursor, isn’t one of the two main patterns. Instead the two patterns are Aleutian low, North Atlantic high (for wave 1) and Aleutian high, Ural high (for wave 2)? In fact, the Aleutian low, Ural high is more similar to the left picture of what happened this year. Can anyone explain/reconcile this, please? I am confused!

Well, it was in that sort of state before the Greenland block collapsed and we reverted to +NAO.

The GFS 6z in FI gives a pointer as to what we might be looking for if the retrogression idea comes off, from T192: 850 temperatures at T384:

ECM clusters T192-T240: All show a ridge through the UK to Scandi, but this is much stronger on cluster 2 (20 members) than cluster 1, which has a more westerly influence. T264+: The Scandi high option seems to no longer be on the table this morning, with a UK high being the destination in cluster 2, whereas the more mobile cluster 1 eventually puts up an Atlantic ridge. This is the retrogressive option - and this seems to fit with the signal from the seasonals, and also the ECM 46 - which, as @blizzard81 noted earlier, was a stronger signal for heights to the NW yesterday than recent runs. I’m still not wildly optimistic that a cold spell is on the way in February, but all the evidence seems now to suggest that if it does materialise, it will be from height rises somewhere to the NW. Original post: https://community.netweather.tv/topic/99793-model-output-discussion-cold-spell-ending-what-next/?do=findComment&comment=5019542

ECM clusters T192-T240: All show a ridge through the UK to Scandi, but this is much stronger on cluster 2 (20 members) than cluster 1, which has a more westerly influence. T264+: The Scandi high option seems to no longer be on the table this morning, with a UK high being the destination in cluster 2, whereas the more mobile cluster 1 eventually puts up an Atlantic ridge. This is the retrogressive option - and this seems to fit with the signal from the seasonals, and also the ECM 46 - which, as @blizzard81 noted earlier, was a stronger signal for heights to the NW yesterday than recent runs. I’m still not wildly optimistic that a cold spell is on the way in February, but all the evidence seems now to suggest that if it does materialise, it will be from height rises somewhere to the NW.

ECM clusters T192-T240: Cluster 2 (14 members) has a proper go at a Scandi high. Cluster 4 has a strong high but ends up to the east of the UK. Cluster 1 (contains the op) has a less strong build of heights, and cluster 3 weaker still, remains +NAO regime. T264+: Clear retrogression signal shown on cluster 1 - even makes the Atlantic ridge regime (purple border) at the end - this has been hinted at previously, but this looks a stronger signal. Cluster 2 has a high in the vicinity of the UK, to the east. Cluster 3 has a strong then weakening Scandi high (some members surely in the previous cluster 2). So still plenty in the mix there, from which something colder could develop…

8, now that does look good. But there’s a minefield to cross before we are in 8 at any decent amplitude!

February composites for 6 and 7 El Niño, amplitude >1. 6 looks rubbish, I’m sure someone was ramping it slightly on here the other day, can’t remember who. 7 looks good but that’s where the question mark over amplitude on the model output is at the moment.

I think we may get a heads up on this one from the MJO analysis, because looking at today’s: Ignoring what the model is predicting, we are right now going into phase 5 at high amplitude. If that amplitude is maintained, where the models have it decreasing, as we go through phase 5, then I’d be a little more confident it wasn’t going to collapse on us the moment it reaches the ‘good’ phases. Original post: https://community.netweather.tv/topic/99793-model-output-discussion-cold-spell-ending-what-next/?do=findComment&comment=5019183

I think we may get a heads up on this one from the MJO analysis, because looking at today’s: Ignoring what the model is predicting, we are right now going into phase 5 at high amplitude. If that amplitude is maintained, where the models have it decreasing, as we go through phase 5, then I’d be a little more confident it wasn’t going to collapse on us the moment it reaches the ‘good’ phases.