Model Output Discussion - moving into Winter

[Community Team]

A new thread for discussing the model output. 

Please keep it to the just discussing the models in here. For general chat, moans and ramps, the current thread is the Autumn one, with the winter one starting on December 1st:

https://community.netweather.tv/topic/97423-autumn-2022-moans-ramps-chat/?do=getNewComment

For Winter forecasts and discussion around that please head over this thread:

https://community.netweather.tv/topic/97982-winter-2022-23-forecasts-and-discussions/?do=getNewComment

To access the models, you'll find links to the main ones in the green bar beneath this post, you can also head over to the charts and data homepage here:

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As ever please keep it friendly and respectful in this thread. As with any other part of the community, if we can keep with these principles, it'll be a better place to spend time for everyone. 

Be kind -- Stay on topic -- Share your knowledge -- Be polite -- Be honest -- Be tolerant -- Be family-friendly
 

[bluearmy]

@jules - I don’t see your comments as being pessimistic- I see them as being very relevant. Until we get the extended modelling with less spread then we have many places that we could end up. Of course your location and ours being so different does mean that one of us could be much happier than the other if this trends to be a little more knife edge than we’d hope to see  …..

[Methuselah]

Seems like as good a time as any for posting the latest GEFS temp. ensembles:

    

It's still a bit touch-and-go with snow potential, but it could be worse! 

Edited November 26, 2022 by Paul
I've not actually edited your post Ed, I'm just testing the messaging system!

[MATTWOLVES 3]

Had to laugh this morning folks...I've noticed as we countdown to a potential colder snap in around 10 or so days time,which in fairness is gathering support amongst those ensembles...quite a few of you were getting concerned about uppers and dew points not being good enough! seriously let's get the cold in first then worry about if the uppers are up too the task! It's very early days and any protracted spell of cold sypnotics will quickly bring in cold enough uppers.

Some lovely lovely ensembles again...im not cherry picking but just showing up a few as there are a wide range of them and I don't wanna bog the thread down by posting them all.

The cold chase is now in full effect...you have my blessing to get serious

Edited November 26, 2022 by MATTWOLVES

[phil nw.]

Something we don't see very often.

Two separated vortex's with independent jet stream flows.

This is inevitably sending cold air into mid latitudes.

Some good points being made though about so many paths this could follow.Bearing in mind it is early in the season so the upper temperatures are still cooling.

If the pattern remains as ensemble guidance suggests then as we go further into December we should start to those 850 hPa coming down further.

It's a case now of seeing if the blocking aligns in our favour.It will be some days yet before we get some certainty on this I think.

Looking at the trend for the main block to head towards Greenland we would be very unlucky not to see a decent cold spell from this.

Whatever happens though there's plenty to interest us going forward.

[tesaro]

A precursor to a SSW possibly later into Dec. Would be typical of our luck that it takes a Month to get a proper cold flow established, only for the whole thing to be shuffled up with a QRSSW.

Still, it’s nice to have a Ticket in the British Winter draw even if it does turn out to be a duffer

[sheikhy]

Ecm 06z same as earlier 00z run for 90 hours so good news there!!!✌

[Kirkcaldy Weather]

Your welcome

OK this will likely turn into a loonnggg Post

Jan 1987 is a really good pattern to enquire about for a number of reasons, not sure if I was aware of that spell but let's analyze...

It links nicely with the post I done about negatively tilted troughing from January 2013

Overall pattern *note I'm not talking about the coldpool that was present in 87 but the low stalling and dropping south and block in a not too dissimilar position matches up with the 0Z Icon  

 

Also I mentioned in a post the isobars we often look to be within when it's a Scandi block which often gets the easterly locked in 

heres a good comparison with February 2018 

 

And we can add Jan 1987 to the elite list of 510 dam getting to the UK

And call it fate but here's the January 1987 setup

Block through Scandi with lows to its south...  GEM 00z mean

 

GEFS 06z mean 

Followed by the expansion to a Greenland block 

GEM 

GEFS 

ECM joins the Scandinavian > Greenland brigade 

GEM 00z  

GFS 06z 

GFS p 00z 

GFS P 6z 

 

 

If anyone hasn't fallen off their chair yet I'm sure these will accomplish it

More mean charts for me to put in a keepsake folder 

 

December 1995 

528 dam 

December 2000 too

Note that the 510 dam was relatively close by at times on each of those occasions 

[geordiekev]

Aaah, the Grail of Greenland, however we all know 11 days is way too much time for changes as Christmas '21 taught us, HP can retrogress too far North sometimes, so feet firmly on ground. I recall last December GFS continuously forecasting required cut off lows, 6+ days out for other models having none of them, ending in dry benign periods bar the storms

[ITSY]

First foray into the season for me - work & football have kept me at arms length but it's now too interesting to stay quiet. I don't have much to add beyond the general optimism that's been shared. That being said, us seasoned folk know that if there's a way for it to go wrong it will so we need to keep grounded. There seem to be two challenges to look out for as this pattern develops - first is the uppers once the cold is established (and as others have said, getting the cold pattern in place is what is most important in the short term), the second is ensuring the emerging Azores low signal doesn't drag the medium term pattern into a west-based -NAO. That's hit us hard a few times I recall. My instinct is that if this materialises the first 'wave' will be a relatively benign Easterly-type event that pegs back temperatures a bit towards or just below average (and will annoy people in here), but which sets up a broader pattern that is much more conducive to prolonged cold and snowy weather. As always, patience is a virtue in this game. Luckily for you guys, I'm off to Israel or a week at the start of December which, knowing my weather luck, will probably seal the deal for you all! 

Edited November 26, 2022 by ITSY

[Cold Winter Night]

I looked at the EPS 0z plume for De Bilt, and compared it to yesterday's 0z, like for like:

It's interesting that of the 4 visible scenarios I posted about last night , scenario A has disappeared.
The milder options, where the High did not make it quite far enough West for an Easterly flow are mostly gone now, lowering the mean in Holland from December 1-4. Nothing exceptional, but at least seasonal.
The other scenarios remain.

The building of a Scandinavian block, and the early beginnings of retrogression, from Positive Blocking (BLO+) towards a Negative NAO is clearly visible up til Day 8 on the regime chart.

I personally think the retrogression will happen, but my areas of concern from a cold perspective are (1) about heights remaining in Eastern Europe, resulting in a more Southeasterly sourced flow, and (2) about a fast paced retrogression, without Canadian vortex pushback, resulting in a Greenland High that ends up too far Northwest and placing Holland, and possibly the UK too, in the Southwesterly flow of an Arctic trough descending into the Atlantic.
Coldies loathe the vortex to the Northwest, but we also need it to keep Greenland or Scandi Highs in place and feed them with WAA, pretty much all famous cold spells are evidence for that.

With the earliest potential onset of truly cold developments still at the very back end of the 10 Day output, patience and restraint will remain precious virtues in this place.

[sheikhy]

And just as i said earlier ecm looks the odd one out the icon 12z comes out and pushes the scandi high west again and moves to ecm at 102 hours!!!!!

[Paul]

Looking quickly at the London ECM ensemble from the 00z. The heatmap gives a pretty clear indication that the colder options grow as we get into December. But, the spread, even within the 90th percentile (which should discount the outliers on each end of the scale), shows the uncertainty that persists.

 

Then, throw in all the other models and it's a similar picture - a colder trend looks likely, but how cold is not even close to being clear. 

[Ali1977]

Day 7 and the ICONs latest run looks more blocky to our north. 

[northwestsnow]

ICON has changed its tune

6z 168

12z

[Kirkcaldy Weather]

12z icon ...Blocking more dominant 

0z  12z 

0z   12z 

Edited November 26, 2022 by Kirkcaldy Weather

[January Snowstorm]

The Icon, as the case with a lot of models shows a very blocked and very messy evolution this evening. It's getting clearer that the first attack is not going to be cold enough but that retrogession could finally bring some proper cold. Anything worthwhile remains 10 days plus, BUT consistency on better aligned block is showing on every run!

[TSNWK]

Just now, Kirkcaldy Weather said:

12z icon ...Blocking more dominant 

0z  12z 

0z   12z 

Another run showing the low pressure of the iberian coast.. wafting up milder air into the mix...

I guess that's where the jet is heading and stalling..... so although we could do without it.. I'm not how without introducing pressure on the blocking from the jet.

[ITSY]

Icon is a move in the right direction. For those newbies watching and participating in this early season fun, I'd say that essentially anything within the next week and slightly beyond should be looked at as building blocks, getting the pieces of the puzzle into place...

[Kirkcaldy Weather]

4 minutes ago, TSNWK said:

Another run showing the low pressure of the iberian coast.. wafting up milder air into the mix...

I guess that's where the jet is heading and stalling..... so although we could do without it.. I'm not how without introducing pressure on the blocking from the jet.

Ain't nothing mild there, nice cold buildup to the east and that mega cold to the north

[nick sussex]

Good blocking but low heights over Iberia aren’t good for advecting deeper  colder uppers into the UK .

On the surface though it will be colder ( the infamous faux cold )  but we do need to see a retrogression signal strengthen and low drop south over Scandi.

The overall pattern though with the main PV shunted far to the  north and not limpeting itself to western Greenland is always a welcome sight for coldies .

So fasten your seat belts coldies and enjoy the ride and I suspect there will be some interesting outputs over the next week .

[sheikhy]

Gfs op further west at 96 hours!!!been doin that for a few days!!!!

[Mike Poole]

Apparently, today’s the day.

I thought it would have happened earlier, to be honest, given the modelled pattern, but no, it was today.

Someone had to go and tout the possibility of a ‘west-based negative NAO’.  Of all the winter model watch jargon, this is the one I hate the most!  The ‘oh so nearly’, the ‘defeat from the jaws of victory’, this joyless phrase should be expunged from the netweather dictionary…

I don’t think there is any reason for such negativity, in my experience, such an outcome does occur, but not from the position we are now in with such a huge signal for blocking.  

GFS 12z rolling, I’m interested in firming up or not, the strong signal from this morning for destination Greenland in 2 weeks, I’d be ok with this, but wonder if a block hedging bets between Greenland and Scandi as we were yesterday would be a slightly better position…let’s see…
 

[Day 10]

2 minutes ago, Mike Poole said:

Someone had to go and tout the possibility of a ‘west-based negative NAO’.  Of all the winter model watch jargon, this is the one I hate the most!  The ‘oh so nearly’, the ‘defeat from the jaws of victory’, this joyless phrase should be expunged from the netweather dictionary…

I don’t think there is any reason for such negativity, in my experience, such an outcome does occur, but not from the position we are now in with such a huge signal for blocking.  

[tight isobar]

Great sister lobe  seperation once again reasonably early stages.. And that Pacific ridge “could NOT be better placed in sync.. it’s something that certainly scuppered last Decembers possible dripping/ cold NW Europe : uk outbreak !!.. we are in good hands - the vortex looks in an impossible position- going forward 

Edited November 26, 2022 by tight isobar