Mike Poole

I think the flatter, more disrupted low (and therefore more southerly) is winning out here - as I mentioned last night, the EPS did have support for it. And if that is the case, one would expect GFS to be last to go with it, as it does have a bias towards blowing up lows rather than sliding them, which is kind of what we’re seeing.

The low at T120 is really causing the models some issues, probably because on some runs it splits into more than one low. My view when I looked at the clusters was that the UKMO solution should not be discounted, and here’s a handful of the EPS that show a more southerly track:

CoventryWeather Yes, bit of a bounce back on the SSW chances since yesterday. GEFS 12z have 48% going for a SSW. Blocking signal remains strong on the ECM 46. The progression of the MJO, according to the actual data (grey line), has been progressing round smoothly for weeks as it now tiptoes into phase 8. Once again, the model predicts a drunkards walk going forward, but then it’s done that every day there are charts still available for.

ECM clusters T120-T168: The op is in cluster 2, which has the most rounded low anomaly at T120. Bit difficult to see on these plots, but the other two clusters pass the low more southerly and quicker as far as I can see. So I think UKMO solution might have some traction, but you’d need to see the individual runs to be sure. T192-T240: The build of heights is NW of the UK by T240 on all clusters. None have a UK high at that time. Cluster 3, which contains the op, does look to inflate heights to our south slightly courtesy the low to the far west which is deeper than on the other clusters. T264+: The extended is a downgrade because of the presence of cluster 3 (14 members), which leads to an Atlantic sourced airstream and re-inflates the heights to the south. Clusters 1 and 2 have a strong block in the Greenland area by T360 - given the position of it, UK wind direction probably very dependent on which representative member they’ve chosen. Both cluster 1 and cluster 2 have good potential as we firm up the detail. We need to see cluster 3 sling its hook.

Not entirely sure what all the fuss is about. ECM hasn’t followed the UKMO for sure, but at the moment, the UKMO is right at the southern end of the envelope, so it is not really a surprise. If the UKMO has picked up on something, other models may move over the next couple runs. Moving on to the next phase, T192: Can only trend colder from here as a nicely positioned ridge enters the picture.

Cloud 10 Yes, it is isn’t it. The earlier part of the run was underwhelming (for the UK). But here’s the thing, I’m not sure how the micro-scale moving of the pieces to determine the snow or not question next week, affects the larger scale movement of the pieces on the longer timescale which seem to be all pointing in the same (blocked) direction. Are the models overegging the blocking in week 2? If they aren’t, could be some end to winter. But all that will have to wait, the first question is - will the ECM follow the UKMO tonight?

GEM has the easterly in by T216, after the low clears: Uppers not spectacular as yet, though. There’s suddenly an awful lot going on on multiple timescales.

UKMO T850s, T120, T144! Awesome! GFS meanwhile rather struggling to clear the low east. GEM a little south initially, but moves NE.

That ECM That’s the 0z, mate. UKMO T144: Quite an extraordinary shift south on this model. Fascinating.

Uncertainty Yes, I agree, the models are suggesting this could turn into a spectacular late winter cold spell. I think, perhaps, posters on here invested too much in what was a very long chase for something very mediocre in January, and are perhaps being over-cautious second time round. GFS 6z has this at T270: Very consistent with what the ensembles are saying about expected developments to our north on this timescale. It would be very unlucky to miss out on some memorable winter weather from this, will be fascinating to see how it pans out.

ECM clusters not holding back about the longer term evolution this morning! T192-T240: Blocking developing during this timeframe, strongest into Greenland in cluster 3. Northerly component to UK winds on clusters 2 and 3. Cluster 1 builds the ridge through the UK to the NE, with a ridge to the NW as well. T264+; Worth looking at the big picture across the clusters. A diffuse pattern of blocking at day 11 converging on strong blocking in the Greenland area by day 15 - on all clusters. Although, interestingly the 4 day 15 charts all have different coloured borders, so the algorithm has seen fit to classify them as different regimes! If anyone can explain why the day 15 chart on cluster 2 is +NAO, and on cluster 4 it is -NAO, please tell us! There are differences in the exact placement of the high, but the detail of that won’t be resolved for a while.

Concentrating on the medium range timescale, and the development of high latitude blocking, GEM already showing signs at T240: GFS a slower burner this morning, but well on the way there now at T330:

GFS 18z settled on a UK high for a while, but at T360 - surprise, surprise - it’s now on the move! Think we’re going to see some fascinating evolutions in FI over the next few days before the models converge on which one is actually going to happen, but all the signs now are that we have a real chance of nailing a proper cold spell.

ECM 46 looking good re pressure patterns. Zonal winds: Fewer members today going for the technical SSW than yesterday. This chart suggests we’ve made it into phase 8 on the actual data. The model would have us back in phase 6 by day 5, but I remain suspicious of that!

ECM clusters, T192-T240: Custer 2, which contains the op and has 22 members shows developing high pressure to NW possibly linking to NE. Cluster 2 a modest wedge of high pressure, but well placed. Cluster 3 similar to NW, but a low camped west tending to re-inflate Southern Euro high. Cluster 4 heights getting sucked north through the UK. T264+: Er, just bank, please. All of them! Clear trend to a northern block, clusters 1 and 2 centred south of Greenland, cluster 2 has NE’ly over UK. Cluster 4 extends the high east and brings in easterly. Cluster 3 just drags its heels with surface high pressure close to but west of UK. Major upgrade tonight!

Just seeing a subtle change around day 10 in the models tonight which could have positive ramifications. After the low has passed, there is a tendency for the high pressure that follows it to track to a slightly higher latitude, which means that instead of the UK high which was seemingly the destination days 10-12 in recent runs, a block further north of that is now looking more likely.

Eagle Eye Yes, GEFS 6z have 58% chance of a SSW now. In an ideal world, the QTR from this will kick in just as the lagged AAM/MJO response is waning and ignite a BFTE 2024…well, it could happen, couldn’t it? Or, for balanced commentary, the SSW could demolish a perfectly placed block established as a result of the AAM/MJO. Something to keep an eye on, as you say…

Where’s this high going? GFS T270: If you accept that potential for Thursday’s snow is confined to the north, then moving on, the next phase is the surge of cold south as the low passes - this looks good on both GFS and GEM this afternoon. And GFS heading for a decent finish…

Met4Cast I see what you are saying, but I do think sometimes the teleconnections view is always on to the ‘next thing’, before the current thing has had a chance to play out, the lagged response to which is what the models are currently struggling with out in FI. It has not yet been resolved as to what the local UK impact of this might be. Too early IMHO to call this a bust. (And there is still a possible SSW around the 16th which may further complicate things.)

LRD Yes, bear in mind the regimes are for the Euro-Atlantic region, which the UK is towards the east of. So the red would include a mid latitude UK high as well as a high centred over Scandinavia regardless of what the description says, and indeed, in summer, the desirable (for most) charts are those with a red border.

ECM clusters are back after going AWOL last night. Only 1 cluster out to T168, so no light to be shed on the potential for snow in the next week, and to be honest the op runs will be a better guide to that anyway. T192-T240: Cluster 2 looks cold for the UK, with the trough extending way south and a wedge of heights to the NW providing a northerly flow. Cluster 1 has stronger heights to the NW but more distant, and the trough is less pronounced, but still a cold evolution. T264+: There is a lot going on here. One thing that strikes me is the amount of red borders (Scandi block). This highlights the possibility of drawing in an easterly or northeasterly. Cluster 3 shows this well - evolves a very well placed block. Cluster 2 could be good too with some tweaks. Cluster 1 heads the block up to Greenland, again slight tweak needed to align with the UK. Cluster 4 has a much weaker attempt at blocking that largely fails to take hold. Plenty of cold options in the mix in the extended timeframe. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5028583

bluearmy According to ECM, on the cluster plot: a red frame indicates association with the blocking climatological scenario, a blue frame indicates association with the positive NAO climatological scenario, a green frame indicates association with negative NAO climatological scenario, a violet frame indicates association with the Atlantic ridge climatological scenario. The same colours are used on the 46 dayer regimes plot, where they are described as follows: Blue - positive North Atlantic Oscillation (NAO+). Green - negative North Atlantic Oscillation (NAO-). Red - Scandinavian Blocking (BL). Purple - Atlantic Ridge (ATR). Grey - members with no regime attribution Assuming the regimes are the same or close, then I think it is right to interpret red as Scandi block, but obviously each regime covers quite a wide range of possibilities, and sometimes the plot doesn’t obviously look like the regime it has been assigned by the algorithm! In fact, one could simplistically interpret the regimes as: blue - high to the south, green - high to the north, purple - high to the west, red - high to the east. And that wouldn’t be far wrong.

ECM clusters are back after going AWOL last night. Only 1 cluster out to T168, so no light to be shed on the potential for snow in the next week, and to be honest the op runs will be a better guide to that anyway. T192-T240: Cluster 2 looks cold for the UK, with the trough extending way south and a wedge of heights to the NW providing a northerly flow. Cluster 1 has stronger heights to the NW but more distant, and the trough is less pronounced, but still a cold evolution. T264+: There is a lot going on here. One thing that strikes me is the amount of red borders (Scandi block). This highlights the possibility of drawing in an easterly or northeasterly. Cluster 3 shows this well - evolves a very well placed block. Cluster 2 could be good too with some tweaks. Cluster 1 heads the block up to Greenland, again slight tweak needed to align with the UK. Cluster 4 has a much weaker attempt at blocking that largely fails to take hold. Plenty of cold options in the mix in the extended timeframe.

Moving south at T156: Just shows that there is a chance that large swathes of the country could get a good dumping from this, and within 7 days.

No sign of the clusters this evening. ECM 46 has a few points of interest, here’s sea-level pressure anomaly: Signal remains for high pressure to the NW until mid March. But where does it get the Greenland high for w/b 5th Feb from? Zonal winds: Again an increase in the cluster going for an SSW around 16th Feb. MJO: This is a slight concern - for days the actual MJO has verified more amplified than the model predictions consistently. But there is little signal in the model to now move it into phase 8 with any amplitude, do we keep the faith or will it fall at the final fence? (It has form for this!)