Mike Poole

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!)

GFS 12z has another strong reversal in the strat, -14m/s by the end: This is gathering momentum, the impact of this would most likely felt be towards the end of the month, but the GFS 6z responded very quickly from the top down:

Cold Winter Night That’s a very good point. Any snow end next week would be a bonus that has never been guaranteed, it is possible with the right wedge/slider combination, but the real interest, and what the teleconnections, and ECM 46 have been suggesting begins w/b 12th Feb. I am with others in having the jitters about all that getting downgraded before it reaches the reliable, but as yet there is no specific reason why that should happen other than Sod’s Law (which has tremendous forecasting accuracy when it comes to UK winters, it has to be said).

GEM the pick this afternoon, brings in easterly nicely, T204: GFS is good also, cold is delayed compared to the best runs yesterday I think. UKMO poor again (and bear in mind the majority ECM cluster favoured it). Snow towards next week end still very possible for some, I’d like to get that nailed - there are likely to be good opportunities to follow, but in the UK those cannot be taken for granted yet. Still uncertainty over the MJO and whether it will make a decent phase 8 that I’d like to see resolved to have confidence that the consistent longer term forecasts from e.g. the 46 will deliver.

GFS 6z has very nice wedge at T144, helps the cold flood south by T180:

ECM clusters T120-T168: Looking at the T168, they differ in the position of the trough, cluster 1 has it west like UKMO (21 members), cluster 2 goes with the op (17 members) and cluster 3 has it deeper more like the GEM (13 members). T192-T240: Here, cluster 3 (16 members) has the most northerly line of attack with a deeper trough. T264+: Cluster 3 is the one we want here (16 members) with a very good strong block in a great position. Cluster 2 develops a ridge in the Atlantic and pushes it too far east, cluster 1, despite being -NAO retains a westerly flow to the UK.

GFS is able to bring in an easterly T246: Initial cold plunge delayed a little on this run compared to 12z, but an interesting evolution so far afterwards. There are quire a lot of options for a cold evolution beyond day 9, I think.

ECM 46 increasing the chances of another SSW just after mid month. We’ve seen a reversal on some GFS runs too. The main cluster remains centred on a reduction to 15m/s as it has for a few days. Will be interesting to watch, because of those that do show a SSW, some have the zonal winds going negative big time. Just another variable in the mix here, and given how closely the strat and trop have evolved all winter, one would bet on a quick trop response of one of the more energetic SSW members came off.

ECM clusters T192-T240: The genera trend clear across both clusters is the Euro trough and a high west of Greenland. Cluster 2 has more of a wedge in the Atlantic meaning that the trough is sharper in the vicinity of the UK through day 9. T264+: An explosion of uncertainty at the extended range. Cluster 5 brings in an easterly under a block through Iceland in to Scandi abd is probably the pick, cluster 3 looks a return to westerly. Clusters 4 and 6 have a northerly ahead of ridging in the Atlantic, in cluster 4 extending to Greenland. Clusters 1 and 3 look a lot going on with wedges and so on, would be useful to look at in-between charts as things are moving. As I say, a lot of uncertainty to resolve, but all with plenty of interest.

Harsh Climate There’s two things in play now, one is the wedge (or not in case of ECM) and whether that will result in snow in just a week’s time - and if so, where? I think that is a separate issue as to the longer term evolution (Euro trough and blocking to the NW) but if the wedge verifies it will certainly help bring the Euro trough a reality sooner. But it should happen anyway, in the no wedge scenario, the models will just find another route if that destination is the one driven by the background signals. ECM T216, and the northerly is in, courtesy of the flimsiest ridge to our west imaginable!

frosty ground Modest wedge in the Atlantic at T192 helps, will be interesting to see if height rises progress into Greenland later in the run. I think it has been clear that, initially, modest wedges are part of the evolution rather than a sudden large block - although a large block later has been evident on the EPS clusters in the extended since yesterday.

GFS 12z is turning into an absolute belter! T210: It’s often said in jest, but I get the impression that, for once, this really is a case of the models ‘smelling the coffee’ as regards MJO evolution, and upgrading accordingly.

Things are continuing to gather momentum this morning on the ECM clusters. T192-T240: The Euro trough now in place by day 9 across the clusters, The build of heights towards Greenland is most evident on cluster 3, all clusters have a strong northerly component to the flow by day 10. T264+: Cluster 1 here has the strong Greenland block from yesterday and has 22 members. Cluster 2 hugs this closer to Iceland extending to Scandi and draws in an easterly, has 15 members. Cluster 3 ends up with a UK high and cluster 4 westerly then builds another Atlantic ridge. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5027310

Things are continuing to gather momentum this morning on the ECM clusters. T192-T240: The Euro trough now in place by day 9 across the clusters, The build of heights towards Greenland is most evident on cluster 3, all clusters have a strong northerly component to the flow by day 10. T264+: Cluster 1 here has the strong Greenland block from yesterday and has 22 members. Cluster 2 hugs this closer to Iceland extending to Scandi and draws in an easterly, has 15 members. Cluster 3 ends up with a UK high and cluster 4 westerly then builds another Atlantic ridge.

It seems to me that the GFS 18z is showing a similar longer term evolution to the ECM and EPS, with the pattern change heralded by the clearing east of the UK of the low at T216 on this run:

Northern Sky Hi, yes, I think I do. The ECM T240 leaves a good space open after the low clears the UK east for a ridge to build towards south Greenland, while the CAA on the lee side of the low establishes the Euro trough. The fact that it is supported by 32 of the EPS is worth noting, and also it is consistent with MJO phase 7-8, with some lag. One thing I’ve been watching lately is how the MJO is behaving compared to how it’s modelled. Here’s the ECM 46 take today: Now here’s the same plot yesterday, looking at phase 7: The grey square is where it was yesterday, the cloud of red dots are the 1 day forecast from all 100 ensemble members yesterday, I’ve put a gold star roughly where the actual data from today’s plot goes - none of the members are near it! And that’s day 1 - the models don’t seem very good at predicting this measure of the MJO at all, and on this occasion, it has consistently verified at higher amplitude through phase 7 than modelled. This may mean that as we are now in the key MJO phases 7-8, the models may increase the signal for blocking as they get to grips with their own error on the MJO, and that might also bring the pattern change a little earlier. But all looking very interesting from 10 Feb onwards, I would say. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5027140

Northern Sky Hi, yes, I think I do. The ECM T240 leaves a good space open after the low clears the UK east for a ridge to build towards south Greenland, while the CAA on the lee side of the low establishes the Euro trough. The fact that it is supported by 32 of the EPS is worth noting, and also it is consistent with MJO phase 7-8, with some lag. One thing I’ve been watching lately is how the MJO is behaving compared to how it’s modelled. Here’s the ECM 46 take today: Now here’s the same plot yesterday, looking at phase 7: The grey square is where it was yesterday, the cloud of red dots are the 1 day forecast from all 100 ensemble members yesterday, I’ve put a gold star roughly where the actual data from today’s plot goes - none of the members are near it! And that’s day 1 - the models don’t seem very good at predicting this measure of the MJO at all, and on this occasion, it has consistently verified at higher amplitude through phase 7 than modelled. This may mean that as we are now in the key MJO phases 7-8, the models may increase the signal for blocking as they get to grips with their own error on the MJO, and that might also bring the pattern change a little earlier. But all looking very interesting from 10 Feb onwards, I would say.

ECM clusters show a strengthening signal for cold in the extended. T192-T240: Here, cluster 1 follows the op run, well supported with 32 members, with a cold northerly to follow the low clearing east. Cluster 2 a little slower. T264+: Clusters 2 and 3 build a strong block over south Greenland by day 15. Cluster 4 has it slightly further east, cluster 1 retains the upstream ridge. Taking a step back from the individual patterns depicted, the trend towards stronger heights to the NW and a Euro trough are starting to match what we have been seeing on the 46 for a while now. Details to be firmed up (a lot) later…

ECM T240: Pulls the cold south as the low clears to the east, establishing the Euro trough, cold for some time thereafter with nothing significant upstream to dislodge it.

ECM linking through Greenland to the Arctic high - be interesting to see where this one goes, possibly stronger wedge to come here, T168:

Yes, I think earlier in the season people would have been hoping that a significant block might establish itself with some longevity, the downside of that with a Greenland block is it could just be cold and dry - longevity isn’t an aspiration right now, increasing daylight with see to that anyway, so if a setup that brings in snow from sliders under wedges transpires, then that will do fine - and if it is a bit marginal, again, we can’t really be choosers. A concern is how far south might be in the game, but with a bit of luck, some of us might see some snow before February is out.

GEM and GFS at T168: I prefer the GEM here with regards to the first slider low. The GFS rather making a mess of it. I think this is just the first salvo though - and should it deliver, it will be one for the north only. But the upstream low also looks slidy on both models, have to see how the runs pan out, but I wonder if we are now sleepwalking into a pattern of lows going under wedges of high pressure a little earlier than we might have expected.

ECM clusters from T192: Not quite sure what to make of these this morning, I would imagine the clusters shown hide quite a lot of important variation, given what we’ve seen on recent runs. The op is in cluster 1 in the earlier timeframe, which heads towards a -NAO, looks a bit wedgy in the extended (31 members). Cluster 2 in both timeframes has the Scandi block regime, but not really evident from the charts shown, the key feature seems to be an upstream ridge. I think once we get the pattern change (assuming we do) we may be looking at chances for transient cold snaps rather than any prolonged cold spell, but that might work out OK for snow for some, still too much uncertainty so more runs needed…

I wonder if this might be another thing going right for us this time? Weakening westerlies in the strat allowing a promising trop driven pattern to take hold, whilst not adding in the randomness of another SSW (probably). As I mentioned yesterday, MJO actual data continuing to progress calmly through phase 7 at decent amplitude (grey line) regardless of the bizarre projection the models have continued to predict in just the very near future:

ECM clusters T192-T240: The consistent part of this timeframe is the erosion of Euro heights by day 10. Cluster 3 probably the best for some earlier cold, also cluster 4, but at this point, setting up the pattern change is the most important thing. T264+: Clusters 1 and 2 look excellent, with significant trough to our south, especially cluster 1 at T264, and a nicely placed high. Cluster 3 has the pattern a little too far west. Cluster 4 look like it might tee up an Easterly and cluster 5 builds heights into Scandi. We are back in the game properly now. Yes, this could go wrong, it could land with poorly positioned chess pieces! But it could also go right, we will see…