IDO

Yes, it makes a nice change. Hoping this is reinforced in subsequent runs. The scatter in the ensembles suggests ups and downs for the next few days regarding post-D6-7 output. GEFS for London: There are all sorts of solutions in there, and low confidence inter or cross model as of 0z today.

I would say at D9 there are differences: GFS - GEM - EC

Let us see if EC takes us to a place different from the GFS after this delay. I'm not sure there is much certainty post this delayed northerly if we look at the GEFS and GEM. This is unsurprising, as a low(s) undercutting can be difficult until D2-3 to model. We are at least now more confident of D6-7. EC: maybe sleet to rain to snow at D7-8? Then D9:

Well, there you have it, EC is finally moving towards that surface high that delays the northerly at D6-7: It has proven again that it is no longer the top dog. The low from the Azores now moving towards the UK, and 850s are disappointing at D7: GFS clearly as of 0z better modelling in the last two days.

Hoping the early morning crew...if any of you bother...are the harbingers of better news. I would say that the uncertainty from D5-6 is clear and that we cannot rule out anything. The GFS 18z shows that even with a poor run it can get some surface highs in a favourable position with wedges to maybe get something out of the NW to SE diving jet. D9:

Like the GEM, the Arctic wedge is on our side on this run:

We avoided the GFS road, but the next frame will decide if it goes the GEM route with that shortwave:

You can all breathe now. Def, not GFS route: D6:

I think that waiting for the EC is the sensible solution. If that holds firm, we can move to the 18z with hope. If the EC moves towards the GFS, we have a problem, although the grey area between GFS and EC may still have a route to cold like the GEM. But IMHO the GEM got lucky with a wedge of heights from the Pacific conveniently re-stocking the GH, which the GFS didn't really: The ^^^GEM getting help from a wedge just at the right moment!

Looking at D7 UKMO, I would say it has moved towards the GFS, just slower: UK: GFS: That is a step away from the EC 0z and a move towards the GFS; EC at D7: Look at the gap between the two troughs and the surface highs on the UKMO and GFS. GEM also has that surface high spoiler but has better heights in Greenland that don't make it end up with the troughs converging. No idea what is correct, but the GFS solution is possible, and EC 12z may tell us if that is the trend.

We can see the surface high form on the GFS at T144: This slowly sinks SE, taking the residue heights with it, and the Scandi and Atlantic troughs converge north of the UK, and we are hopelessly placed from there. T168:

The Met Office deep dive on YT suggests what most of us have interpreted from the recent model runs. The low(s) arriving from the Azores interact with cold air over the UK on late Tuesday and the possibility of a snowline over the UK. Looking at Manchester North on their graph, they advise low confidence in the sweet spot. This ties in with the general trend: cold moving south from the weekend and possibly a snow event mid-week. After that is where it gets even trickier! Indeed, the web update does not suggest that the GFS outlook is their best guess. It suggests an Atlantic high/ridge, which I am unsure what makes them think; maybe cold zonal with an NW to SE diving jet is feasible. We wait for D8-10 to be resolved before I take that seriously.

No beating around the bush; if the 06z verifies, this period of model watching will shoot into my top 10 of all-time model fails. From my IMBY POV, the GFS run is poor from start to finish and a waste of 16 days of prime-time winter. Clearly, the feedback GFS is receiving has trended the whole model to move away from what looked nailed on as recently as yesterday. We can only hope it is fundamentally wrong. The D8-14 washout from GFS 06z:

The Pacific Heights are changing the pattern from D8, with the axis of cold moving from N-S to E-W over the pole, so guess who is in for a cold spell on the 06z, D8-12: That is clearly something that could easily change.

Let us see where this route takes us. With wedges and a NW to SE diving jet, we will remain on the colder side, which may be good for those further north: D9 jet:

I thought the 0z GFS OP was progressive in the breakdown, but this trumps that! It does appear that my hatred of GH modelling is seen in all its pain here, with a poor show if GFS is correct. D7:

We can see where the GEM has issues. The surface high is back again between D6-7: That takes a while to slide away and blocks the cold long enough for the low coming from the Azores to reach the UK before the cold air gets south of Manchester. Meaning the lows are a rainfest for most. That is popping up regularly, but hopefully, we can see that eliminated from the GEM, and maybe that model will show more like the EC.

Looking at the ECM standard deviation from D7: We see very strong support for the ens with the initial cold plunge, clearing the south coast. Then D8-10 we see the south has lower confidence, as to the snow line. The mean supports the low incoming from the Azores into the UK region. I think that this is now highly likely versus what was showing 24+ hours ago. D10 mean: On this run, excellent chances for those in the north to get real dumping. Further south on the ens is less clear. The good news is that we will get a GH and a cold plunge over the UK, and snow chances according to the 0z EC ens.

We can see the high risk of this attack from the disrupting Azores Low, with even the EC at D10, FWIW, pushing the milder uppers into the south; D7-10:

There is no doubt on this run the EC is a corker for snow. But we saw the same on the GFS 12z yesterday and the two subsequent runs have had the low(s) further north and further south. So, at this range, I have low confidence EC has nailed that track. Hopefully, we can see it firm up on a UK snowstorm.

I was talking about the Azores Low that had previously been progged to sit in situ and eventually interact with the Atlantic trough. Models now show it will slide east and interact with the Scandi trough. All three models show this link-up and the variability. There is no Azores High. So it is all about undercutting, which the EC achieves, and GEM and GFS fail to some extent or another!

Models firming up on the Azores Low moving in around D8-9: This is the next bend in the road. If EC has is right, that would be snowy, but we see the problem with GFS and GEM. It seems like endless hurdles to jump to get anything out of this GH!

That is true, and I suspect the culprit is the Alaskan High that has squeezed the life out of the pattern on our half of the NH: The Pacific heights vary from run to run, so I would not put much weight on this run at this range. But as you say, the short straw is cold but primarily dry.

D10 GFS versus the EC: I would say the models are struggling. See if the EC can get two runs in a row tomorrow.

D9 and the undercutting means the Azores low(s) are further south versus the 12z: The GH dissipates progressively on this run, the fastest I have seen it modelled and with no help from the Arctic high. We are in a cold trough, so we'll see what happens next.