Well, you're both right in different ways.  The ensemble suite is useful for gauging the stability of the evolution in the short- to medium-term, ie perhaps out to 4 or 5 days.   It is beyond that the ensembles can't detect something unexpected that happens in the atmosphere: clearly things do change otherwise the forecast charts would be rock solid for a much longer period of time.  We have all seen the ensemble suite flip unexpectedly; it's happened in the last couple of days, as Brian commented.

As Rumsfeld said, in a different context, there are known unknowns but there are also the unknown unknowns. It's the latter that brings the uncertainty.

I suspect the OP meant that individual members of the ensemble rather than "the ENS are just as fallible as a single chart". A single chart (by that I am asuming a chart from one model run) is efffecively one element of the ensemble, which by definition is a collection of all of them. It is all the perturbations viewed together. Thus viewed as such we can see the variability and the deviation from the mean will indicate the degree of confidence around that mean.

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Shocking downgrade for the ECM mean
Is this the moment we all feared?
https://www.meteociel.fr/modeles/ecmwf.php?ech=240&mode=1&map=0&type=1&archive=0 

No, it's the moment that happens every year. Except every ten it doesn't. You only have to read or remember the threads every winter since 2013 to know that!

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Hi David, 

Yes, better than the GFS 12z and it handles the LP approaching (or in this case not approaching) from the SW very differently. It does mean no widespread snow event but it also drops a deep LP SSE from Baffin Bay, west of Greenland, down into the North Sea and sets up a renewed Arctic plunge as we head towards Xmas.

Obviously it will all change again in the 00z and that evolution may not have much ensemble support. It just shows how tricky this is going to be.  The Met Office guy on that YouTube video was saying it will be several more days before the behaviour of that LP away to the SW is resolved.

Hi Peter 🙂

If the GFS 18z op is right (a big 'if' in itself), it could be that the LP to the south-west doesn't really make inroads to the UK at all and simply decays to the south. An added complication as suggested by that run is the possible development of another low over Greenland which then dives south-eastwards towards the UK. Hopefully, by the time we get to the end of this week, we will have a rather better idea of what will likely transpire from early next week onwards.

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GEFS mean just about keeps the 850s subzero at the critical point. 

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From what i can see, there has seem to have been either a watering down or a subtle change in the charts over the past few days.

Although its looking cold, it doesnt look that cold for widespread snow, indeed showers look marginal, and thats if there are showers, if anything any subtle signs of some showers developing seem all but gone.  BBC called this 2 days ago and 8 think theyve got the short term spot on. Snow to northern scotland and NE england... some showers to ireland... even the temps seem a little up on where they first were. In the main, this looks dry. Which is disapointing given the synoptics of a LP diving south over the uk.

Hoping for inprovements 

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its literally like we order our winters from Wish.... nothing like we wanted, and about 6 months too later than expected.

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JFF

P 30 from this @ 192


https://www.meteociel.fr/modeles/gefs_cartes.php?code=30&ech=192&mode=0&carte=0&ext=0 

To this at 384 

https://www.meteociel.fr/modeles/gefs_cartes.php?code=30&ech=384&mode=0&carte=0&ext=0 

🤣

Going by the 18z imby its 
4-5 days of 2-3C and -2 to 4 C at night, with the outside chance of a wintery shower then back to square one. So just a average at best cold snap-spell. 🥱 

https://www.meteociel.fr/cartes_obs/gens_display.php?x=311&y=100&run=18&runpara=0&type=3&ext=1 

 

The hopecasters continue but based on tonight's ensembles the reality looks like a standard but welcome  very cold one week winter cold snap then remaining chilly. Looking at the overall pattern further cold snaps are possibly more likely than last few winters but that would be really be damned by faint praise. 

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A cold snap implies 2-3 days....this wintry occasion is going to be about a week (at least for us Southerners, and probably longer for those further north), so would that be called an interlude? Or something else? An incursion perhaps?

Early days but GFS looks to be an improvement on the cold lasting

the high almost drops into Scandi by 216 

UKMO is a snowfest this morning. 🥶
Nice GEM out to day 10.
GFS ok but goes pear shaped day 8.
Clear as mud basically.

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https://www.meteociel.fr/modeles/ukmohd.php?ech=168&mode=1&map=10 
This mornings 👁 candy ❄️ 

https://www.meteociel.fr/modeles/ukmohd.php?ech=168&mode=1&map=10 
This mornings 👁 candy ❄️ 

Excellent for our part of the world.👍

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I expect many people in the south will want to bag this one.

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UKMO, ICON, GEM, ECM and GEFS swinging towards sustained cold this morning. EC at D7 is a beauty, along with the UKMO.

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It looks like the picture for the middle of next week is not really much clearer this morning. Before then, cold.

The 00z ECM op run is as good for wintry weather fans as the previous op run was poor.

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There's always one isn't there? UKMO and now ECM going cold so of course GFS throws out a stinker.

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There's always one isn't there? UKMO and now ECM going cold so of course GFS throws out a stinker.

😂😂 I was thinking exactly that. Certainly keeps us on our toes. 

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In these situtions you do need cross model agreement at 120 and sometimes 96 hours.  Cold in the short term, uncertain in the medium term. A fascinating period of model watching coming up and by the end of the weekend things will be clearer for next week,.

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