Mike Poole

damianslaw It is really weird. I am sure the models did have it heading SE a few days ago! Then the GFS got the idea of it heading NE, and now, particularly the GFS and GEM have it heading north or even NW. The thing is, it’s put a major diversion in the route to longer term cold.

ECM 46 zonal winds: Noteworthy chart because it shows a reversal on the mean. So it does now look like we’re getting another SSW. This one has a good chance of being a significant reversal. Will only add to the uncertainty… Except, I’m not sure I need the likes of ECM or GFS to work out how this is going to pan out. Oh, no! It’s perfectly clear that no sooner than longer daylight means that a decent snow event is no longer possible, the perfect cold synoptics will miraculously present themselves in time to ruin spring!

bluearmy T192-T240 charts to back up your comment: T264+: Clusters 1,2,3 all build a Greenland block formed by retrogression. On cluster 1 it is a monster stretching into the pole, cluster 2 retains some higher heights to our NE. On cluster 3, a white hole anomaly over Greenland results. Clusters 1 and 3 look cold for the UK, with 28 members in total. Cluster 4 is rather different with a westerly to the UK and Russian high. So, another day, and still jam the week after next. But the models really struggle in these setups that promise UK cold and then fail to deliver it…

Daniel* 1 hour difference there between the two plots might explain?

ECM clusters T192-T240: Cluster 1 demonstrates what has rather gone wrong with the output in the last couple of days, to build the high lat block, the ridge is through the UK, which leaves a build up of heights to the south and a lot of warm air that has to be shifted later. Cluster 2 has this further west, and cluster 3 further west still which is much better - low heights retained to the south and the block taking shape near Iceland. T264+: Clusters 1 and 4 make a decent fist of getting a northeasterly in by day 15. Cluster 5 goes a bit west-based. Cluster 3 holds some promise, cluster 2 leaves the block poorly orientated. Given clusters 1 and 4 total 23 members, I would say chances of getting a decent cold evolution within the next two weeks about 50/50 at the moment.

I wish people would stop declaring victory for the GFS (or the like) when neither its solution or that promoted (until this afternoon) by the ECM and UKMO has yet verified. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5030981

A look at the medium term evolution, from the ECM clusters, first T192-T240: The signal across the clusters is towards northern blocking. The presence of the high towards Russia probably tips the algorithm into assigning these as Scandi block (red border) as this weights the high pressure to the east of the Atlantic region, but the area that will affect the UK is more central on clusters 2 and 3, and to the NW on clusters 1 and 4. The concern though, as I mentioned this morning, is the fuel to build this high pressure tends to be from a ridge through the UK, so there is no cold incoming immediately. T264+: Cluster 1 has a Greenland high moving to Iceland. Cluster 2 has a Scandi high retrogressing to Greenland. Cluster 3 has a Greenland high drifting west. Cluster 4 has a strengthening Greenland high. Cluster 5 has a Greenland high drifting north. These are all rock solid consistent with the expected direction of travel from the 46 dayer, which still shows this today. We would be extremely unlucky not to get a substantial cold shot out of this, although, palpably, we do seem to be extremely unlucky this year.

I wish people would stop declaring victory for the GFS (or the like) when neither its solution or that promoted (until this afternoon) by the ECM and UKMO has yet verified.

ECM clusters T192-T240: The GFS solution at T192, in which the low clears away NE, is not really represented. Cluster 3 seems the most northerly track of the low. But the theme across all 5 clusters is blocking to our north. T264+: Both clusters end with a block to the NW, cluster 1 it is over Greenland but declines, cluster 2 it is to our N then retrogresses, with an initial easterly in this timeframe. Given the UK is very much on a gambler’s losing streak at the moment, one worry I have is that the high latitude block will prove to be a mirage - no evidence for that at the moment, but a concern might be ridge up to that does seem to pass through the UK on some runs, which would keep the cold at bay. So more detail as this counts down is needed… Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5030267

ECM clusters T192-T240: The GFS solution at T192, in which the low clears away NE, is not really represented. Cluster 3 seems the most northerly track of the low. But the theme across all 5 clusters is blocking to our north. T264+: Both clusters end with a block to the NW, cluster 1 it is over Greenland but declines, cluster 2 it is to our N then retrogresses, with an initial easterly in this timeframe. Given the UK is very much on a gambler’s losing streak at the moment, one worry I have is that the high latitude block will prove to be a mirage - no evidence for that at the moment, but a concern might be ridge up to that does seem to pass through the UK on some runs, which would keep the cold at bay. So more detail as this counts down is needed…

sheikhy I think it has been rock solid because it is erring on the side of its known bias to blow up lows, rather than disrupt them. The fact that the other models are seeing a shallower feature should not be discounted, I think it is likely that they are right and GFS has it wrong.

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!