Thinking the op will be one of the coldest options!

Sub -14c 850s across the south !!

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So GEM18Z does exist out to T+84h, the crucial time is now T+72h when the lobe forms so we can compare GEM12Z with GEM18Z.

So the verdict?
The lobe is ALOT weaker on the GEM18Z compared to the 12Z. Take a look at T+78h. Look a little NE of where the surface low is (995hpa on the 18Z) and you can see the 18Z is consistently 3-6dm higher!

This is big. GEM has flipped sides!!!!!

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Gah this isn't so straight forward.

GEM18Z has swung massively towards the GFS solution, but ARPEGE has gone the other way. The lobe is stronger on the ARPEGE. Summary of the 18Zs so far.

GFS: Modest downgrade (saved by a lucky surface pattern)
GEM: Big upgrade
ARPGEGE: Downgrade
ICON: No substantial change (still terrible though)

 

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The difference at 140 between ECM and gfs is certainly an eye opener, one is going to be spectacularly wrong I feel ! Odds on it’s the GFS as it’s the 🥶version . 

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18z gefs a slight upgrade at +144 as a whole (synoptically)

 

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Early GEFS quite strong on agreeing a plunge in temps (London) from 7th/8th 

Some rather eye watering ensembles on the 18z GFS for us snow starved Channel Islanders!!
https://modeles16.meteociel.fr/modeles/gensp/runs/2023020118/graphe3_00000_220_245___.gif 
 

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Confidence.😁😎👿
 

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I'll take P08 from the 18z run please at +228: (-16c 850's!)

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GEFS: The lobe. These are the 500hpa heights on Jan mayen island (it might not be the best place, but its easy to click on and its roughly in the right area).

https://modeles16.meteociel.fr/modeles/gensp/runs/2023020118/graphe10_00000___-8.90625_71.25_.gif

The lobe  passes through where there is that first dip in the Geop Z500 lines, you can see a remarkable spread for such a short amount of time ahead (Z500 is usually about the lowest uncertainty parameter there is). Anyway you can see it varies from about 508dm (pale pink) to 532dm (dark brown). The OP is actually on the lower side; remember the higher the better - this is the crucial feature that governs everything. Anyway let's look at the ECMWF ensembles for comparison purposes.

https://modeles3.meteociel.fr/modeles/gens/ecmwf/runs/2023020112/grapheens3_0001_0_0_-8.90625_71.25_.gif
 

Now look at the same Z500 lines when the lobe is passing over. Varying from 504dm to only 523dm. The OP is stuck at about 510dm, compare that to the GFS which is at about 518dm.

And the ICON? Around 502dm!!!!!

 

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Interesting video, but the Med low is imo a consequence rather than a cause (or a less distal cause if that makes sense). The entire placement of the scandi high system, including that med low is determined almost entirely (in the sense that all other variables are basically equal across all model runs) by the strength of that upper trough in the greenland sea. And the neat thing is that there is pretty much a perfect correlation between the strength of that lobe and the cold downstream several days later (18Z was a slight glitch where the surface pattern was a bit better despite the lobe being a bit stronger)
 

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Plenty of ensemble support this time (18z)for the cold GFS op run. Be interesting over the next couple of days to see if the other models (mainly ECM and UKMO) go down this route or not, or meet halfway.

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No support at all or very little - Op was a cold outlier wasn't it? 18z if that's what you're referring too?



I am ready for more chopping and changing but ENS members have trended colder in medium term - the models are all over the place. I think there is a lot of confusion following this warming of Stratosphere and what's really confusing the models is this deep pool of cold airmass heading into N, and NE America/Canada which is also helping to fuel up the jet which could be why the models are flip flopping each run? Furthermore, the MJO is in phase 3.5 which doesn't favour cold weather for NW Europe but then again we have weaker PV and there could be another stratospheric warming occurring around middle of February - but will split the already weakened PV and reverse zonal flow to bring us a cold end to February this time? - Time will tell!?

At least the PV has been wounded and significantly weaker than before this stratospheric warming last week so shouldn't take too much of a warming to split it this time IMO. 

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Plenty dip into the -8C to -12C range,and more below -5C.
Also the majority have dew points dropping below freezing indicating at least the air should be cold. 

Blimey the GFS still refusing to let the easterly dream die. Another bitterly cold run this morning. 🥶🥶🥶

UKMO miles away again. 
 

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Lol the high migrates to Greenland and we get a northerly.  GFS 0z is giving us some entertainment at least.
 

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GFS vs UKMO & GEM unbelievable run from GFS again. As Quantum said that development to the North is key to the extent of ridging. Not in anyway resolved

GEM also a million miles away this morning. GFS still very much on it's own.

 

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GEFS look better as well P15 the star of the show.

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The GEFS mean data are very much in line with the other models’ output with high pressure centred somewhere to the east of the UK (in contrast to the op run).

I know there are a few cold options in the set but the overall picture still has a cold easterly as very much the minority option. It does however look like the outlook is largely anticyclonic for more S and E parts at least.

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Short GEFS and the OP brings the majority of its suite with it with the mean 850 now -6 by the 7th (London). 
We’ve seen some stark differences between the main players before but this is a proper chalk and cheese standoff. Admittedly it’s ‘only’ a 600 mile shift in the position of the high, but the ground truth couldn’t be more diverse.
I’d love to know what an experienced professional makes of the current battle of the NWP - I might have to ask.

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The ECM supports the GEFS mean and the other models that go out to around day 8 on the 00z op run so far: https://www.wetterzentrale.de/maps/ECMOPEU00_192_1.png  

The GFS op run is very much on its own in the medium to longer term. 

For comparison here is the 00z GEFS ensemble mean at the same time point https://www.wetterzentrale.de/maps/GFSAVGEU00_192_1.png 

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You'd have to think the GFS Op will come into line later today. 

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it’s just like being married, never wrong until they are wrong but they were right in their own way