Model output discussion - Closing in on Christmas

[Alexis]

8 minutes ago, chris55 said:

Foehn effect in full flow over the mountains of Norway. Look how the 850s rise on the north west side with no apparent source.
 

Interesting to see

Reminds me of Christmas Day 2004. Heavy snow showers packing into NW England...

[Daniel*]

25 minutes ago, terrier said:

So what a we take from the gfs06z output. Well it’s certainly taken a step towards the ecm this morning no doubt about that. Are we going to see a half way house here as we usually do in this situation. The thing that is looking like could happen is we end up with west based -nao which is no use to us. It seems we are back to looking at the 10day charts once again. I’m not so sure we’re we go from here. I’d expect the gfs to keep taking baby steps towards the euros this evening. You certainly wouldn’t bet against the Ukmo and ecm model at such a short range it would take a brave sole. 

Enlighten me terrier? It hasn’t budged at all. 

[Tim Bland]

Slightly less cold set of ensembles with the op on the cold side. Still no ice days / beasts from the east (bar 1) but we are still in the game for snow, especially if thickness is low. Interesting signal for Xmas eve into Xmas day....

[terrier]

21 minutes ago, Daniel* said:

Enlighten me terrier? It hasn’t budged at all. 

I wasn’t talking about the far reaches of fantasy island. I’m talking about earlier in the you can see it moving towards the ecm early doors in the run. The ukmo and ecm this morning aren’t great. But I guess people will still bury there head in the sand because it doesn’t fit there cold agenda. I’m sorry but they is too much hope casting and some are setting themselves up for a huge disappointment I feel. All the talk yesterday of another dec 2010 we’re pie in the sky. Sorry for the rant but the ecm and ukmo aren’t great but I guess the gfs will be our saviour in some eyes. 

[BlueHedgehog074]

22 minutes ago, danm said:

Great post. To expect each and every run leading up to a cold spell to be flawless and to not expect some downgrades as well as upgrades along the way is unreasonable. It doesn’t mean this cold spell is nailed on by any means, but we sometimes forget the rollercoaster model runs we’ve been on for previous cold spells. 

Some good points made. I think it’s good when the charts aren’t always showing a cold and snowy heaven for the UK (or what ever your desired weather types are), especially in FI, as there’s always the likelihood of these charts getting swiped away from us when getting into much more reliable time frame. Only exceptions would be if there was strong support for these charts, good ensemble backing, good background signals and they are in tune with the anomaly charts. Then the chances of these sort of charts coming off are higher. Though this still clearly wouldn’t prevent the operational models having a wobble between run to run.

Can be the case that models, such as the GFS, picks up a cold pattern in FI, gets rid of it, then picks it back up again in the nearer term. Been some points made here in the past that models seem to struggle when a big pattern change is afoot as they try to work it all out. Which then makes them particularly prone to their wild swings between run to run.

I think a big lie-down would be needed if every chart was always fantastic. All that exhaustion from walking along numerous garden paths, lol  Just a few times those garden paths can lead to something that becomes reality

[Guest]

A cold snap verses cold spell all depends on the energy being swept up the eastern side of Greenland. If that energy is sharp and clean it supports a robust high pressure in the atlantic. I think we are in for more cold modelling over the coming days before this is settled yet...better than last nights 18z too....

[Guest]

GFS is king in my eyes, taking into account it has more outputs and longer forecasts you can gauge more useful information from them all this side of the pay barrier.

I expect the ECM to move more towards the GFS this time round due to the consistency.

[BARRY]

3 minutes ago, DCee said:

A cold snap verses cold spell all depends on the energy being swept up the eastern side of Greenland. If that energy is sharp and clean it supports a robust high pressure in the atlantic. I think we are in for more cold modelling over the coming days before this is settled yet...better than last nights 18z too....

Interesting times to come, so lets enjoy all that the models have to produce

[Frosty.]

Oh my, Shirley another thread is imminent?..but..before that,...there is Shirley some cold potential?....wow..hey coldies, there’s a chance..there’s a chance according too the GEFS 6z!!!

 

Edited December 19, 2020 by Jon Snow

[Matt H]

20 minutes ago, DCee said:

GFS is king in my eyes, taking into account it has more outputs and longer forecasts you can gauge more useful information from them all this side of the pay barrier.

I expect the ECM to move more towards the GFS this time round due to the consistency.

I admire your confidence, trusting the GFS is like jumping off a cliff and hoping that you’ll land unharmed.

[mulzy]

All I want for Xmas is.....

...perturbation 26 from the 6z GEFS!

I have been a really good boy this year Santa (promise!)

Edited December 19, 2020 by mulzy

[phil nw.]

The outputs still very much supporting continuing Atlantic ridging.

Just flicking through the charts the ridging ebbs and flows and re-enforces every 3 or 4 days.

gefs 06z

ECM does the same thing within it's 10 day charts.

So we have a quasi-stationary Atlantic wave ushering the Greenland trough se across or just east of our location. 

We can see and appreciate how modeling will come up with variations on the exact pattern as they work out timings and strength of the ridging as it battles against the vortex which in turn wants to move across the north.

The overall pattern is still primed for ongoing colder conditions with this wavering jet and it looks like with this re-enforcing of the Atlantic ridging from time to time we will see further injections of polar air from the north west.

The London ens graph continues to extend the surface cold 

The little uptick just after Christmas likely due to the ridge being flattened somewhat  as we import a more westerly flow before the next build up.

 

 

Edited December 19, 2020 by phil nw.

[Zak M]

7 minutes ago, mulzy said:

All I want for Xmas is.....

...perturbation 26 from the 6z GEFS!

I have been a really good boy this year Santa (promise!)

For those wondering what P26 shows..

         

[Kirkcaldy Weather]

I want to start off by saying this isn’t a bragging type of post that’s not in my nature in the slightest which hopefully many on here know anyway

around two weeks on and good to see that the run up to Christmas (and indeed beyond) is of interest for something more seasonal, latest fax chart for 23rd  528 dam and colder air over nearly all the UK also a few troughs in the flow maybe chance of some wintry showers which the short range models will be best to keep a look out for that, and going into Christmas Eve still chilly 

For any new members the upcoming pattern is all about the ridges and troughs which I have tried to show roughly with the red line the ridges and black the trough  the main focus point at the minute gets a bit more complex with a few things going on, could be the linking of the higher pressure in the Atlantic with the higher pressure roughly from Siberia into the Arctic  whenever we are talking about patterns that could result in colder conditions for us there is always some flipping between the models as changes downstream even slight can make a big difference to the outcome upstream in this case downstream being USA probably focused on activity in the NE around Christmas with forecasters trying to pinpoint where the next cold blast will be positioned there. I wouldn’t get too stressed about each difference on every run that’s perfectly normal I mentioned before I don’t think I can remember us getting into a cold spell in a straightforward fashion with every model in agreement all the way down to +0hr, the big positive from what I’m seeing is just how different the patterns are behaving to what we would normally expect at this time of winter (Atlantic sourced, wind rain etc) things continue to look really conducive for higher pressure and blocking then add in the strat outlook and personally I’m starting to get a little bit excited  

And the increase of that eastern block is again looking impressive still somewhere around 1060/1065 hpa but some runs pop that up to 1070hpa  

 

[Duane S.]

12 minutes ago, mulzy said:

All I want for Xmas is.....

...perturbation 26 from the 6z GEFS!

I have been a really good boy this year Santa (promise!)

Ironically that run would cause record number of toys to be expelled from prams along the way, as the second ridging doesn’t occur as it gets flattened and turns into a UK MLB. What happens instead next is a Jan’87 style link up with the Arctic high. High risk once in a generation scenario that one.

Edited December 19, 2020 by s4lancia

[Kasim Awan]

In the possible event that low pressure parks up across the UK w/o a surface easterly flow, large snow totals could still develop. Heights here are extremely low, winds light, perfect recipie for prolonged shortwave snow.

Take for example March 2016 which saw 12" here at 300m and 4" at 100m.

Uppers of -4 (first two images)

Compare this to the potential scenario ahead, which in dynamics is almost a carbon copy, uppers a bit cooler and nights longer, great recipie going on here.

It's worth noting that the gfs / ecm ens have a mean pressure over the UK of ~ 1015mb at 216h, so this solution is becoming marginalized.  EC op is the most realistic solution so far, imho, and seems to fairly reflect all factors at the synoptic level. 

 

[Frosty.]

Are we here for snaw?...well.. are we?...anyway, there is some snaw potential in the GEFS 6z..among other output!!!

[northwestsnow]

7 minutes ago, Kasim Awan said:

In the possible event that low pressure parks up across the UK w/o a surface easterly flow, large snow totals could still develop. Heights here are extremely low, winds light, perfect recipie for prolonged shortwave snow.

Take for example March 2016 which saw 12" here at 300m and 4" at 100m.

Uppers of -4 (first two images)

Compare this to the potential scenario ahead, which in dynamics is almost a carbon copy, uppers a bit cooler and nights longer, great recipie going on here.

It's worth noting that the gfs / ecm ens have a mean pressure over the UK of ~ 1015mb at 216h, so this solution is becoming marginalized.  EC op is the most realistic solution so far, imho, and seems to fairly reflect all factors at the synoptic level. 

 

Nice Post Kasim..

[Vikos]

Some fresh EC 00z Clusters

+72h

+120h already 3 scenarios

 

+168h

+216h

+240h

+348h

 

Some +240h anomalies and

Edited December 19, 2020 by Vikos

[MATTWOLVES 3]

40 minutes ago, Jon Snow said:

Oh my, Shirley another thread is imminent?..but..before that,...there is Shirley some cold potential?....wow..hey coldies, there’s a chance..there’s a chance according too the GEFS 6z!!!

 

Plenty of interest in colder conditions moving forward...im pretty surprised many keep saying its destined to fail...ie...all at 10 day for instance..well look at last year fi didn't even exist then did it,not even at long range were cold charts appearing. And to my knowledge we have some well respected weather guys who think our chances of cold look better this year...Jon Hammond for one.

I'm not really sure our Doctor Spok is gonna help us though mate...he's on the starship Enterprise above the atmosphere,or on another planet...fat lot of good he's gonna do...

[northwestsnow]

I haven't posted much because I feel GFS is leading us up the garden path again.

I'm glad Christmas will be dry and cold, but I suspect things will flatten out a lot more than GFS is suggesting in the Atlantic...

Dont like coming across half empty hence hence the slow down in posts...

We will see, I'm hoping for a GFS 6z scenario but its a 25% shot at best for me.

Strat events might deliver after New year anyway   I feel Glosea has this wrong with its +NAO setup.

 

Edited December 19, 2020 by northwestsnow

[Kasim Awan]

Now we have a trend of good Day 10 charts, rather than just the isolated one, which is what we have been dealing with all winter. Plus, the current northerly (23rd) albeit weak has been modelled well out and verified rather well. No reason why a secondary emerging trend can't either.

Edited December 19, 2020 by Mapantz

[Jason M]

29 minutes ago, Zak M said:

For those wondering what P26 shows..

         

Yep, that definitively IS a cold chart!! Those kind of 850s at this time of year would be ice days all round. A proper pipe freezing easterly. For absolute perfection I'd be wanting air pressure to be lower though as probably a fairly dry easterly albeit I suspect that would happen naturally over the following days. Obviously its just an ensemble 15 days away that will have close to zero chance of happening but fun to look at nonetheless. 

Given that the Meto declare an emergency for a couple of days of below average temps, they would have fun with that!!

Edited December 19, 2020 by Jason M

[Frosty.]

1 hour ago, Tim Bland said:

Slightly less cold set of ensembles with the op on the cold side. Still no ice days / beasts from the east (bar 1) but we are still in the game for snow, especially if thickness is low. Interesting signal for Xmas eve into Xmas day....

Awesome, keeping it real, I have no issue with that..good job..

[Frosty.]

25 minutes ago, MATTWOLVES said:

Plenty of interest in colder conditions moving forward...im pretty surprised many keep saying its destined to fail...ie...all at 10 day for instance..well look at last year fi didn't even exist then did it,not even at long range were cold charts appearing. And to my knowledge we have some well respected weather guys who think our chances of cold look better this year...Jon Hammond for one.

I'm not really sure our Doctor Spok is gonna help us though mate...he's on the starship Enterprise above the atmosphere,or on another planet...fat lot of good he's gonna do...

Hey Matt, you are already a netweather legend..couldn’t agree with you more!..I think the models look a lot better from a cold perspective than this time last year.,(obviously)!!!..and the year before..and the year before that..etc..etc..good job mate.. I think this looks better..lol