Model Output Discussion - Christmas and New Year

[Battleground Snow]

Ecm mean 00z v 12z at 240

Still blocked, at what latitude will be revealed in the coming days

Is excellent compared to recent years for sure.

 

 

 

 

[northwestsnow]

The mean is brilliant...!!

 

[Howie]

The jet stream is in North Africa, crazy

[Methuselah]

5 minutes ago, Kasim Awan said:

The 12z output remains highly blocked and cold going forward, and whilst not at the level the gfs had a few days ago, is still enough for cold& snowy conditions. Plus an inversion is highly likely to develop reducing upper requirements for surface cold. So those bfte charts are not the end all.

 

Absolutely agree with you, Kasim; we could be in for the best/longest spell of wintry weather for quite a few years -- at least since 2013. Only time will tell?

[ICE COLD]

Yep mean is excellent. The graph for 850s it good too the only way is down still . And it was an outlier at the end on temps

Edited December 25, 2020 by ICE COLD

[Skullzrulerz]

It's clear to say that compared to the last few days today's model viewing for terms of cold and especially Greenland and to a extent Atlantic Heights have been watered downed, downgraded there's no other way around it that it has gone to great to ok in just a day especially 

Looking back a few days ago we have seen charts that assemble so much blocking around Greenland that it had a black hole in the charts because it was so strong and we also had Atlantic Heights that were robust 

Now we don't have as much in terms of heights and it's only to keep things together for a few days to a week 

Yet again we are now on the hunt for any cold spell is 10 days away if not longer especially if you want large parts of England to get snowfall 

It is somewhat upsetting that some people seem to belittle if not insult or be rude to other people's who are just clearly giving a opinion of how the models are trending 

Thankfully we do have "background signals" next month will should help but by no means guaranteed bring in any colder if not very cold air 

 

[Kasim Awan]

Just now, General Cluster said:

Absolutely agree with you, Kasim; we could be in for the best/longest spell of wintry weather for quite a few years -- at least since 2013. Only time will tell?

Only time will tell. It certainly has potential.

[sheikhy]

1 minute ago, ICE COLD said:

Yep mean is excellent. The graph for 850s it good too the only way is down still . And it was an outlier at the end on temps

I called it earlier ice!!!it just didnt seem right between 168 and 192 hours in regards to that low coming out of northeast usa!!!overall a perfect evening for cold weather lovers!!!

[Griff]

9 minutes ago, ICE COLD said:

Yep mean is excellent. The graph for 850s it good too the only way is down still . And it was an outlier at the end on temps

I'm really starting to appreciate the value of these charts. Thank you. 

Even aware of my own confirmation bias, if I see an op run I 'desire' I rate it highly, whilst immediately tell myself to bin any discouraging synoptics. But these speak louder than words.

 

Edit: just an observation but it seems to me that in part some of the disagreement here on future outlook is based on expectations. 

Those expecting Ski Sunday (yeah I'm old, is it still a thing?) see downgrades, whilst other expecting marginal wintry precipitation, without any sure things (850s around -4, slack flow etc) see things steady as they go. 

Edited December 25, 2020 by Griff

[northwestsnow]

If the det was an outlier by day 9 or 10 that suggests we either, 

A bring in an easterly feed.

B Develop a UK cold pool...

 

[AmershamMike]

1 hour ago, Reversal said:

Big steps in the wrong direction across all runs of all models today. Outlook consistently becoming flatter.

Haaaappy Xmas one and all!

[Methuselah]

I just remembered what I forgot to post a couple of days' back when Uppersgate was in full flow... I'll always remember when, in January 1963, heavy rain (accompanied the smallest of snow crystals) fell -- and froze onto the window panes -- when the 2m temperature was around -6C... I was so angry, I was punching the windows!

Sorry guys, it's taken me 57 years to get that one 'off my chest'!

[MATTWOLVES 3]

3 minutes ago, Kasim Awan said:

Only time will tell. It certainly has potential.

Thanks Kasim...we have some excellent posters on here,and I've not got the time to go through the list,as I would take up an whole page with the names alone...I've only just noticed your a new poster...and wow,your top notch mate...your summary and analysis are excellent.. and its all done in a very level headed and good mannered way..

Now I've said that..I expect a Christmas card next year.. only joking.

Has NWS points out,its a rather cracking ECM mean..God...I love you guys

[SMU]

ECM mean day 10 very good with the surface Easterly & very very cold.

[northwestsnow]

Just now, Steve Murr said:

ECM mean day 10 very good with the surface Easterly & very very cold.

Snow-covered terrain what you reckon Steve?

-10 possible, zero solar input,low dews...

[Kasim Awan]

17 minutes ago, northwestsnow said:

Love this post..

So very true...

Next week is going to be very cold at the surface despite the mediocre uppers...

A bit of snow-cover and clear skies will see temps plummet , Scotland in particular could see some double digit minima, IMO..

Cold for most (-1 to 4C) very cold for a select few (-2 to 1C) i.e. high ground, snow cover & fog

Some moderation from North sea

[bluearmy]

In respect of the greeny heights at day 10, a look at the clusters is revealing. There is a 25% option which has lower heights squeezing the upper ridge south at day 11. The  70% option is wow .......the op is in the 20% cluster at day 10. 

 

Edited December 25, 2020 by bluearmy

[stodge]

Evening all 

First, thanks to @phil nw. for this help yesterday evening with my contribution. 

Second, I hope everyone has had or is having (if further west) a wonderful Christmas.

The weather of course doesn't tale a break - it's been a quiet, calm and mainly fine day here in lowland East London but with Bella on the horizon, all that is going to change as we consider 850s, 925s, dew points and the like while waiting for the snow to fall.

Moving on toward year end and earliest 2021, what can we expect?

12Z GEM: T+120 takes us to Wednesday and Bella remains as an LP in the North Sea just off the Danish west coast with a NNW'ly flow for much of the British Isles. The coldest air is, as you might expect, over southern and western parts at this time. By T+180 or the early hours of Saturday 2nd, not much has changed - the LP has moved slightly west back toward the Scottish coast. Heights remain over Greenland and ridging south into the mid-Atlantic. A new Atlantic LP is to the west of the Azores and I wonder if we will see some phasing with the trough over the British Isles and North-West Europe. -4 850s over most of the British Isles by this time.  Well, not quite - by T+240, the LP has moved ENE and deepened toward Biscay while the residual trough remains over the British Isles. Milder air is approaching from the south but the cold airmass remains over the British isles for now.

12Z GFS OP -  a good start for cold fans from GEM with at least 7 days of cold conditions setting in. On then to GFS which broke the cold spell down in far FI last evening. By T+120, a different orientation than on GEM but the net effect for the British Isles is much the same with a cold NNW'ly airflow and perhaps a secondary feature forming to the east coast of Iceland. 850s show colder air encroaching from the NW. By T+180, the secondary feature has developed and moved south across the British Isles leaving a shallow but complex trough across the British Isles.  The 850s continue to look cold and it's secondary features like that which can bring heavier snowfall at quite short notice. From there, the evolution becomes more complex. The main LP heads south and deepens as it engages warmer air to the south and forms a new LP off Portugal. A residual LP remains in the southern North Sea with a new Atlantic feature developing to the west of Iceland. I'm not sure where this is going at T+240 although it stays cold over the British Isles. The Icelandic LP heads SE into north-west Europe though the residual energy over Iberia prevents a more southerly track. By T+312, there's an ENE'ly flow over the British Isles but throughout the airmass stays cold. From there. the evolution becomes messy but essentially it's a stand off between a very cold airmass to the east and milder conditions to the west. An LP slides down the North Sea but the onus looks to be on milder conditions. 

12Z ECM - well, GFS was a confusing and messy offering tonight. It ended with -12 850s over the North Sea and positive uppers over Ireland and an old-fashioned stand off. ECM looked to be investigating the west-based negative NAO at T+240 last evening. The T+120 looks very similar to the GEM as you might expect but makes more of the developing LP to the west of Iceland.  However, that comes to nothing and the emphasis is on rising pressure in the Atlantic but well north supported by an LP to the south-west of the Azores. This leaves a weak NE'ly flow over the British Isles. -4 50s over much of the British Isles by T+192 and -8 850s moving into Scotland. The evolution from there to T+240 is complex - a new LP forms around Iceland in a lobe of very cold air with LP moving SE across to the north of Scotland into Scandinavia. Pressure remains low over southern Europe with HP dominant in the Atlantic. Signs of something a little milder by the end of the run.

12Z GFS Parallel - as it's now a 4-run-a -day merchant, I'll add a couple of charts from this offering as well. The T+120 has the core of the LP further east into Scandinavia than other models but keeps a N'ly airflow over the British Isles. By T+240 heights jhve developed to the north and the jet is pushed north leaving a complex trough straddling southern Britain and an E'ly airflow for northern parts. Moving on, the cold theme continues until one LP slows and deepens in mid-Atlantic throwing the ridge in front of it up over north-west Europe and dragging the jet back north. It's only at the far end of FI the milder airmass moves in after 10-12 days of cold conditions.

Looking elsewhere, 12Z Control is cold for much of the run. Both the OP and Control keep the PV under pressure at 10 HPA - Control has a split in far FI but OP doesn't quite manage it though the PV remains distressed.

Conclusion: - another strong evening of output for cold weather fans. The initial passage of Bella over the weekend will usher in a chill N'ly early next week which remains in situ (or veers NE) for a few day into 2021. GFS tries to break down the cold spell in far FI but little or no evidence of west-based negative NAO tonight with the onus moving from Greenland or mid-Atlantic heights to polar or Scandinavian heights as we move into January. Nothing terribly mild, nothing zonal and the PV a bit player at best and coming under further pressure. All in all, plenty of interesting weather and synoptics to keep the discussion going in the coming days.

[PiscesStar]

5 minutes ago, bluearmy said:

In respect of the greeny heights at day 10, a look at the clusters is revealing. There is a 25% option which has lower heights squeezing the upper ridge south. The  70% option is wow .......the op is in the 20% cluster 

 

In layman's terms please??? Also, are we expecting upgrades in this evenings GFS run? 

[Kasim Awan]

11 minutes ago, bluearmy said:

In respect of the greeny heights at day 10, a look at the clusters is revealing. There is a 25% option which has lower heights squeezing the upper ridge south at day 11. The  70% option is wow .......the op is in the 20% cluster at day 10. 

 

You know things are looking decent when even the minority option is good

Edited December 25, 2020 by Kasim Awan

[Griff]

15 minutes ago, MATTWOLVES said:

Thanks Kasim...we have some excellent posters on here,and I've not got the time to go through the list,as I would take up an whole page with the names alone...I've only just noticed your a new poster...and wow,your top notch mate...your summary and analysis are excellent.. and its all done in a very level headed and good mannered way..

Now I've said that..I expect a Christmas card next year.. only joking.

Has NWS points out,its a rather cracking ECM mean..God...I love you guys

Same @Kasim Awan and @Scott Ingham

I've noticed when a new member posts occasionally you can cut the air here with a knife, no disrespect, but all groups have norms, cliques and gladly here, often cohesion. 

It can sometimes take a while for the group to adjust that's all, but it's normal. All the better for change! 

I'm old enough to remember when @sheikhy was spelt differently and had several more digits after his posts count... Unlike @sheikhy who's old enough to forget his password and login details...

Learning so much, feeling really positive and looking forward to the new year, thanks all! 

? 

Eidt: quick confession I always without fail read @Allseasons-si as Allison, and in my mind she's cute but clever

Edited December 25, 2020 by Griff

[Matt H]

33 minutes ago, bluearmy said:

In respect of the greeny heights at day 10, a look at the clusters is revealing. There is a 25% option which has lower heights squeezing the upper ridge south at day 11. The  70% option is wow .......the op is in the 20% cluster at day 10. 

 

Fantastic news, goes to show that there’s no point getting upset over one less favourable evolution in the extended range of a single operational run.

Edited December 25, 2020 by Frosty Winter

[Methuselah]

18 minutes ago, Kasim Awan said:

Cold for most (-1 to 4C) very cold for a select few (-2 to 1C) i.e. high ground, snow cover & fog

Some moderation from North sea

Aye mate... and to add some weight to what you say, here are the GEFS ensembles for Suffolk:

    

Hardly a heatwave!

[Mike Poole]

29 minutes ago, Snowfish2 said:

In layman's terms please??? Also, are we expecting upgrades in this evenings GFS run? 

This cluster chart (which has only just come out for us laymen!) is what @bluearmy was talking about, T192-T240 with 3 clusters:

The majority cluster and the third one has Greenland ridge or high.  The ECM op was in the second one which looks a bit meh.  All but the 3rd cluster T192 have a red border - Atlantic block.

Christmas Day - feels more like Groundhog Day!  Never thought I would be sitting here commenting on the 12s just like every other day, hope this pandemic nightmare ends early next year.  I did my family FaceTime in the morning, on my own now so now it’s just like any other day since March.  Plenty of beer in though!  .  But maybe there is hope, it did at least snow on Groundhog Day!

Edited December 25, 2020 by Mike Poole

[Kasim Awan]

Thanks both for the comments. I'm mostly a snow event geek however I also take time to view model output and trends and compared to some others on here I have a lot to learn too. It can take a while for newbies to grasp this concept. It is key though to properly interpret the data and avoid sudden reactions. The overall trend is strongly swayed towards a highly amplified pattern with an Arctic blast signwave (repitition). There will be deviations because ultimately all layers of meteorology takes on situational uncertainty. E.g. in radar watching, showers can change direction, crop up where unexpected.. This is reflected in model output too almost as a law of meteorology. Now imagine a very complex shower pattern, forecast weeks out.. I'd rather focus on the larger picture (shower direction, timing & main areas) as opposed to micro details. In a similar way I would also prefer to stick to "larger picture" pressure & temperature trends. However, logic and understanding should be applied i.e. this shower pattern usually does x y z, as can also be applied to longer term forecasting.

This is the best meteorology can offer and is why the pros stick to the trends and logic rather than micro details for both showers & the long term forecast.