Mike Poole

@sebastiaan1973 Yes, the 46 showing a strengthening signal for blocking in the Greenland area w/b 12th Feb, last 6 runs: The low pressure anomaly into Souther Europe is stronger too - that blue wasn't there yesterday. We need to see this signal start to show more strongly in the EPS over the next few days, building on the excellent cluster 4 in the extended on today’s 12z.

ECM clusters this evening are starting to develop something more interesting. T192-T240: While cluster 1 remains zonal, and cluster 2 shows a brief collapsing ridge, cluster 3 develops a much more substantial Atlantic ridge, albeit with only 5 members. T264+: Cluster 3 is the obligatory zonal cluster, but the others are more interesting, with some kind of ridging in the Atlantic on clusters 1 and 2, and the appearance of a proper Greenland block (for the first time) on cluster 4 (8 members) - one to watch…

Yes, it does seem from the modelling in this range that the force driving the westerlies peters out. But there doesn’t seem to be any strong blocking pattern to follow it. Nothing consistent that I’ve seen from the op runs and ensembles. We could drop lucky with a wedge, for sure. But I am still expecting to see more evidence in our sector of the +AAM and MJO into favourable phases than I’m seeing - it could just be a bit too early.

ECM clusters from T192 onwards: There is interest to develop an Atlantic ridge of some sorts from day 8, but the evolution thereafter is a bit of a mess. I’m not seeing a clear signal for a Greenland high here, rather the possibility that some clearer signal might develop once the trend to a more amplified pattern gets underway. Maybe a little soon for a response to the MJO. But time is tight now, particularly for the south, as the period of interest is now mid February.

An oddity from the 46 dayer tonight, from the regimes plot: On Monday 29th January, all members have no regime! Does this mean we aren’t getting any weather? More likely, the algorithm has given up the ghost for some reason!

The Strat profile has been very much in tandem with the trop profile all winter! With a strong vortex that would be a bad thing. But despite a very weak vortex, it has even so managed to thwart us at every turn. Maybe our luck about to change?

A little more cheer for coldies on the clusters this morning, T192-T240: Clusters 3, 4 and 5 all develop an Atlantic ridge extending into Greenland. Cluster 2 is the only really flat one, with clusters 1 and 6 hinting at height rises to the NW. T264+: +NAO not the favoured outcome here, a collapsing Atlantic ridge on cluster 2, clusters 1 and 3 maintain some ridging to the NW. I think the earlier timeframe needs nailing before giving too much credence to the scenarios in this one. I think the message that is most clear, is that the relentless zonal train is going to run out of steam. What is not clear (to me anyway) is what will replace it. There is no guarantee it will be a UK cold scenario, but the chances are there - think it will take a while before reality becomes clear.

@MJB That signal in Greenland for w/b 12th is the strongest since the runs go back to (9th Jan). Also, there are signs of a transition to it the week before which wasn’t previously evident.

@Singularity Well maybe, but I think there are too many possible pitfalls to be confident of the signal from mid-February to actually still be a thing by the time we get to mid February. An MJO fail certainly looks possible, and the strat vortex looks to be gathering in strength for the first time in winter, if that gets placed badly and starts to really rule the roost, then it could wipe out the rest of winter. We will see…

ECM clusters T264+: Well, there’s something still there in this timeframe, with various takes on an Atlantic ridge, cluster 3 looking the most convincing, but I’ll believe it when I see it, I think. The 46 dayer - the signal looks to be getting weaker there too. If all our eggs sit now in the MJO basket, then we really are up against it expecting that fickle beast to behave itself… The upcoming weather holds little interest for me, so I’ll take a break from model watching for a few days.

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.