Model Output Discussion - Christmas week and beyond

[bluearmy]

1 minute ago, nick sussex said:

I’m going to start from the worse case scenario of the UKMO which means the only way is up ! It’s not been interested and has been horribly consistent. It’s day 7 does deliver a slither of hope , shame it blows up that low .

The GEM I’ve never rated and its huge change over Greenland between runs means it’s going into the cat litter tray .

The GFS is the horrible creature in the Poltergeist closet pretending to be Carol Anne’s friend  . As the mother  says in the film at one point , “don’t go into the light, stop where you are  “ ! ( One of my favourite horror  films although I hate that clown ).

The GFS seems to be determined to find a way to deliver and be popular in here . 

Don’t go into the light until that’s safe and other models are there to guide you home !

 

Ukmo was isolated and not v good for this week for quite a few runs 

I don’t think any model can be relied upon at the moment 

[northwestsnow]

Need the lows incoming at day 4 onwards to get a move on ,absolutely dont want them stalling to our west ,ala UKMO.

That just inflates the Euro trash High.( from hell).

[MJB]

Snow moving south JFF 

[Tim Bland]

Either the 06z or 12z GFS will do thank you weather gods , I’m not fussy One thing they both have in common in FI is the PV is shoved well to the East allowing lots of potential into January

[ITSY]

The GFS Control says yes to its sibling's Griceland heights. The intrigue continues. It must be said that if GFS has this one then it's one of its better winter performances for sure - which, together with its summer accomplishments, would be noteworthy indeed! 

[Cloud 10]

Miles into FI,but a cracking run from GFS with crazy height anomalies around Canada (Canadian warming inc.?) and plenty of cold funneling down towards the UK.

 

[goosey007]

6 minutes ago, ITSY said:

The GFS Control says yes to its sibling's Griceland heights. The intrigue continues. It must be said that if GFS has this one then it's one of its better winter performances for sure - which, together with its summer accomplishments, would be noteworthy indeed! 

Yes if GFS pulls this off i think we will have a new King anoited in this Forum at least !  But if it comes up short not sure many will forgive it and be banised to the cannon fodder models land a la navgem......the stakes are high!!!

Edited December 19, 2022 by goosey007

[BLAST FROM THE PAST]

That’s two and counting .   Loving the uncertainty of the models….but looking at the developing pattern for me the uncertainty is only in the detail. ……and I’ll call UKMO as not being in the right place (however, it would be good to have it on board!!!!!!).  The timing is right for me around Xmas or Boxing Day, just one of the factors why I think GFS is far from being outlandish.

 

BFTP 

Edited December 19, 2022 by BLAST FROM THE PAST

[Ali1977]

That looks like a great mean at T192 - what a great GFS op too - im late to the party 

[ITSY]

This is essentially the conundrum.

The left of this frame is an emerging signal for an Icelandic block across the latest GEFS suite. This would *ordinarily* be associated with much colder weather.

The right of this frame is a clear signal for strong heights across the European mainland across the same suite. This ordinary would bring warmer/mild southerlies and SWlies.

What we're left with is a standoff involving mean North/North Easterly signals for the northern third of the country, and mean southerly signals for the southern third of the country. In between this - the middle third of the British isles - is the golden zone for boundary/frontal snowfall. 

For the short-term (aka Xmas-NY period), the question is simply which of these two blocks wins out. We need the low pressure off Iberia/Biscay to travel into and trigger lower heights into Europe if we're to bring the cold boundary south. Alternatively we need a trigger low in the North Sea to do the same thing. 

It's a really interesting setup though and not one I've seen played out before! 

EDIT: The control shows this perfectly as a battle of the blocks (see the one to our NW over Iceland and the one to our SE over central Europe. In this particular scenario most of England is mild but it doesn't take much reconfiguring to turn it all white. It's a tightrope...

 

Edited December 19, 2022 by ITSY

[Snowmadsam]

1 minute ago, ITSY said:

This is essentially the conundrum.

The left of this frame is an emerging signal for an Icelandic block across the latest GEFS suite. This would *ordinarily* be associated with much colder weather.

The right of this frame is a clear signal for strong heights across the European mainland across the same suite. This ordinary would bring warmer/mild southerlies and SWlies.

What we're left with is a standoff involving mean North/North Easterly signals for the northern third of the country, and mean southerly signals for the southern third of the country. In between this - the middle third of the British isles - is the golden zone for boundary/frontal snowfall. 

For the short-term (aka Xmas-NY period), the question is simply which of these two blocks wins out. We need the low pressure off Iberia/Biscay to travel into and trigger lower heights into Europe if we're to bring the cold boundary south. Alternatively we need a trigger low in the North Sea to do the same thing. 

It's a really interesting setup though and not one I've seen played out before! 

As @MattH said last night, this is an airmass clash, but likewise - I haven't seen a fight quite like this before!! 

Whilst the EC will be important, I'm not expecting a resolution for a while. I'm happy to be proven wrong however. In either a cold or mild way. 

[Rob 79812010]

The latest met update and net weather monthly very encouraging! BBC are stalling their latest monthly. Makes sense given the difficulties the models are facing! Do feel the models are moving to a cold spell (yes, not just a snap)! Dec could well end up with an average in the 2's or dare I say it maybe even the 1,s! Am loving every minute!

[LRD]

15 minutes ago, Ali1977 said:

That looks like a great mean at T192 - what a great GFS op too - im late to the party 

That looks better than the 850s graph. GFS ens up to the 27th

The mean is nowhere near as good as for the same day on the 6z. Don't mean to be a mood hoover as this place is great when cold is on the cards in the winter. I hope the op is right but this has thrown a bit of a spanner in the works

It's really 50-50. Either the GH wins or the Euro High wins. Doesn't seem to be much middle ground. I have a feeling that either tomorrow or Wednesday will see a big swing to either mild or cold

UKMO hasn't been great for a few runs and the MOGREPS ensembles look good north of B'ham but not so much south of the 2nd city. Cause for optimism but not too much confidence

The big positive is the Met Office update

Edited December 19, 2022 by LRD

[Stuie]

A bit like a scandi high, a med high, a greenland high and an icelandic high...

[northwestsnow]

It's clear from GEFS the suite there are a good few members draining heights from SEurope..

[Harsh Climate]

Gfs is a dream run for most of scotland.

If only these lows were 100/200 miles further south from 23rd.

I guess northern england got lucky with this set-up a couple years ago (An 8" fall and 10" fall of snow) so can't complain..  

 

[phil nw.]

Quite an interesting turn of events with the possibility of an Atlantic ridge becoming a Greenland high.

A few runs ago we were relying on wedges to get some cold south.

We still have the villain Iberian ridge to overcome but perhaps the stronger heights further north will tip the balance eventually.

Meanwhile the wavering boundary over the UK is likely to create some snow interest over the coming days.

The move to mild or cold is equally possible and it's easy to see why we are seeing so much uncertainty and wide spreads in the ensembles.

Fascinating stuff.

 

[Kirkcaldy Weather]

Expanding a bit more on this from my previous post 

'So the three biggest focus points for Christmas will be 

Pacific > Arctic Blocking 

USA snowstorm development 

Atlantic troughing / low... negatively tilted, below AVG temps likely sinking south'

What a beaut of a chart 2 days before Christmas

Also a really neat example of a cut off low

You can see here the elongated troughing 

 

But watch how the low starts to separate and becomes a cut off low moving south west (not a very common synoptic development in winter) 

gfs... cold locking in 

When snowfall causes issues for Russians you know we're not dealing with typical winter conditions 

[I remember Atlantic 252]

Wow! for fun of course deepest FI, but perfectly placed for me

 

[carinthian]

UKMO extended seems to want to go tropical as does ICON.  GFS on its own at the moment. However, Met Office think it will be Mid -week before getting resolved . Time running out ! Big call from GFS  if it times the next cold spell correct !

C

[Eagle Eye]

Well, the strong water vapor transport horizontally sourced from the Atlantic should bring cold, dry air on the back edge of it. Considering this is Winter and the long sourced Atmospheric River(AR) and despite the large moisture stream, how much moisture rich it'll be by the time it reaches here is difficult to tell. According to the models it transitions most of the moisture fairly well though. The cold and relatively dry air packet should connect to the back edge of the AR but notice that a little bit of the AR will extend back into the colder air and something like that in an AR if the air is cold enough could potentially dump a lot of snow somewhere.

Note that the AR seems to come in waves that each act like their own little AR with the first one here, the first AR and WAA packet of air. Hence we see the south getting a little bit warmer than average at initial AR landing time ()although the Midlands and further North can still be cold with the AR predicted to move further South each run. Also, the air is quite cold in the first place so WAA will only mix that out sightly and it doesn't look too strong.

Then we see the WAA move further West as the zonal packet associated(ish) with the AR also moves further West and hence the cold, dry air sources itself towards us and there's a decent elongation of the AR into Scotland. In this situation, we could see a lot of snow dumped in Scotland and maybe the North if it looked like this closer to time.

Edited December 19, 2022 by Eagle Eye

[minus10]

Well, i have to say...jff...thats some northerly ..

..just look at the source...

However as to evidence how tricky this setup is going forward..the gfes 12z are all over the place after christmas day..

op on a sine wave fall while many ens going the other way...

I would think the core of the nwp computers will need extra cooling at this rate....

 

 

 

 

[nick sussex]

The ECM at day 4 is modelling low pressure to the sw quite differently to the GFS and UKMO.

Edited December 19, 2022 by nick sussex

[northwestsnow]

Just now, nick sussex said:

The ECM at day 4 is modelling low pressure to the sw quite differently to the GFS and UKMOm.

Need the lows to scoot through sharpish..

[Guest]

Differences at 72 hrs

GFS: 

ECMWF: 

UKMO: