Model output discussion - Closing in on Christmas

[TSNWK]

14 minutes ago, northwestsnow said:

Amongst the excitement I took a look at ukmo 144 , and it looks worryingly similar to GFS 00z..

Hmmmmmmm..

What you do that for  

[frosty ground]

6 minutes ago, Snowfish2 said:

But if the gfs 06z upgrades... Then What? 

Then the ECM downgrades....... Then what?

Welcome to the ride that is model watching.

 

[johnholmes]

Not done a full analysis on the 500 mb anomaly charts but 2 out of 3, including NOAA, suggest the upper flow is going to change from flattish westerly to a more meridional flow sometime between, I would estimate, day 5 to day 8/9; the UK on the forward side of ridging with troughing to the east.

ECMWF/GFS DAY 8-10 MEAN 500MB HEIGHT COMPARISON

MP1.MET.PSU.EDU

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

 

[tight isobar]

Gfs 6z .. going well on energy basing... this looking good

[Sky Full]

Not too sure how much more of this I can take......   Arrrgh!  Winters over!  Weyhey!  There’s gonna be a snow fest!   Oh no!  Winters over again, I’m out!  Hooray - I’m back!  It’s gonna be a white Xmas after all!   But more caution is needed!  But there’s still a lot to play for!   

Bless my poor heart.  If I get through the next ten days it’ll be a result.  “Well don’t look at this thread, then” some of you might say.  Come off it.  That would be like not watching the sky to see if I can spot Santa and his reindeer.  Not a realistic suggestion, is it?

Anyway, the models are still flipping around at this stage and this is the level of divergence they are showing as early as +144hr

500s at +144 hr (22 December):

UKMO  

ECM     

GFS      

GEM.   

[Skullzrulerz]

7 minutes ago, johnholmes said:

Not done a full analysis on the 500 mb anomaly charts but 2 out of 3, including NOAA, suggest the upper flow is going to change from flattish westerly to a more meridional flow sometime between, I would estimate, day 5 to day 8/9; the UK on the forward side of ridging with troughing to the east.

ECMWF/GFS DAY 8-10 MEAN 500MB HEIGHT COMPARISON

MP1.MET.PSU.EDU

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

 

I would honestly take the GFS in terms of high pressure around the Atlantic and Southern Greenland! Though I think it more of a halfway house between ECM 

[sheikhy]

Gfs 06z going very well!!!low further south and sliding again!!did not expect this at all!!

[Kirkcaldy Weather]

2 hours ago, Daniel* said:

it’s worth recognising the far north expected to turn colder few days earlier only from day 6 the crappy GFS agrees as well. It’s not that distant for some.

I would say that Inverness or even Shetland is better referred to as far north but those temperatures look nice from a close to home POV  

5 hours ago, SLEETY said:

Gfs proving its utterly pointless after t144 hours with all this wild swings in its ouput every 6 hours of the day

Sounds just like this thread

[TSNWK]

Looks better to me at 168 with shapers heights into Greenland and more heights to our far north which might give. the Atlantic ridge something to grip onto when it starts to fall over....scandi high maybe ? 
 

[Downburst]

GFS running 4 times a day does give it a chance to correct input between runs, ECM can't do that as frequently, although is a different model and takes more effort to run. But AFAIK the 06z doesn't run with the full data input the other GFS runs get. I don't have stats on the accuracy of the 06z itself, but it does help to see although both GFS and ECM are improving at 5 days out, the ECM is still ahead of the GFS. Hope this helps folks set context

In terms of the 00z ECM, certainly excellent charts for 24th and 25th, very lucky if this comes off as it will be seasonal, and that flow will have some instability in it, so some might get a wintry shower

[Vikos]

17 minutes ago, Downburst said:

GFS running 4 times a day does give it a chance to correct input between runs, ECM can't do that as frequently, although is a different model and takes more effort to run. But AFAIK the 06z doesn't run with the full data input the other GFS runs get. I don't have stats on the accuracy of the 06z itself, but it does help to see although both GFS and ECM are improving at 5 days out, the ECM is still ahead of the GFS. Hope this helps folks set context

 

You are right, 06z and 18z of GFS is mostly missing some airplane data and stuff, so actually there is no sense in comparing 06z to 12z and 18z to 00z. But I doubt somebody will ever learn this. Synoptics always compare within 24h, means 00z to 00z, 12z to 12z and so on...

 

A Comparison of Forecast Skills among GFS Four Cycles in the Past Ten Years --

WWW.YUMPU.COM

---

A Comparison of Forecast Skills among GFS Four Cycles in the Past Ten Years

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwitu6-sptLtAhUKvRQKHdvLCiUQFjAJegQICxAC&url=https%3A%2F%2Fwww.natgasweather.com%2Fwp-content%2Fuploads%2FLive_HDD_CDD_Data_FAQ.pdf&usg=AOvVaw0oSoc0nO9FNKsBnvulOtQL

Edited December 16, 2020 by Vikos

[frosty ground]

Possible Scandi High on this run.

[mulzy]

3 minutes ago, Downburst said:

GFS running 4 times a day does give it a chance to correct input between runs, ECM can't do that as frequently, although is a different model and takes more effort to run. But AFAIK the 06z doesn't run with the full data input the other GFS runs get. I don't have stats on the accuracy of the 06z itself, but it does help to see although both GFS and ECM are improving at 5 days out, the ECM is still ahead of the GFS. Hope this helps folks set context

In terms of the 00z ECM, certainly excellent charts for 24th and 25th, very lucky if this comes off as it will be seasonal, and that flow will have some instability in it, so some might get a wintry shower

Not sure about the 6z running with significantly less data.  Additionally, Last time I looked there is very little difference on the verification of the various GFS cycles.

[tight isobar]

Gwan then.. nice evolution... and reflective of many recent runs..

[Man With Beard]

2 hours ago, Climate Man said:

Happy to settle for bright and frosty. We are then in the hands of where the high pressure ends up post Christmas and that, nobody knows.

Yes I think a white Christmas of the frost variety is a very good bet!

The GFS 06Z is perhaps the best bet for a white Christmas in the east and a slightly longer cold spell - I don't think the Atlantic ridge will hold, but if some heights could get trapped to the north it may force trough disruption and a trough underneath, as well as a trough moving from Europe back to the UK underneath a weakened block. I wouldn't say it's the favourite but it's a very viable option.

Edited December 16, 2020 by Man With Beard

[mushymanrob]

28 minutes ago, johnholmes said:

Not done a full analysis on the 500 mb anomaly charts but 2 out of 3, including NOAA, suggest the upper flow is going to change from flattish westerly to a more meridional flow sometime between, I would estimate, day 5 to day 8/9; the UK on the forward side of ridging with troughing to the east.

ECMWF/GFS DAY 8-10 MEAN 500MB HEIGHT COMPARISON

MP1.MET.PSU.EDU

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

 

IMHO the NOAA charts have slid towards an unsettled cold spell for the period they cover. Chances of marginal snowfall of some description (but not a full blown blizzard) mainly over higher ground.

They do though suggest amplification of the building Greenland high, and with positive height anomalies in the Arctic, personally id have thought there is an increased chance of something properly cold/snowy evolving at some point. A January similar to 1985 sort of pattern, springs to mind, and that had several minor snow events (here in derby at least).

[bumpydogz]

There's an area of precipitation on the 06 that crosses Wales / Central Southern England on Christmas Eve. Looks just the right side of marginal.

Edited December 16, 2020 by bumpydogz

[Thunder and Lightning]

 <-- 6z 0z--> 

6z GFS encouraging, with the low bringing wintry showers during Christmas. However the ridge looks like it is abount to get broken down as low pressure moves in, similar to last GFS run, just not as soon.

 

 

Edited December 16, 2020 by Thunder and Lightning

[I remember Atlantic 252]

Wishbone northerly, central areas dry, snow showers down east coast, rain/sleet west coast

[TSNWK]

Better than 00z looks like the attempts of a Scandi fall just short this time.. just too much pressure from the north west and the lower heights in Europe a little too far away to the east to help us this time..

could have been a lot worse...

 

Edited December 16, 2020 by TSNWK

[Matt H]

A million times better than the 00z run.

[Thunder and Lightning]

3 minutes ago, Thunder and Lightning said:

 <-- 6z 0z--> 

6z GFS encouraging, with the low bringing wintry showers during Christmas. However the ridge looks like it is abount to get broken down as low pressure moves in, similar to last GFS run, just not as soon.

 

 

In this run it does look like the ridge will be broken down, but it doesn't look like it would be with anything mild. Upper air patterns is relatively calm so hopefully nothing too mild would be driven towards the UK

[snowblind]

1 minute ago, mushymanrob said:

IMHO the NOAA charts have slid towards an unsettled cold spell for the period they cover. Chances of marginal snowfall of some description (but not a full blown blizzard) mainly over higher ground.

They do though suggest amplification of the building Greenland high, and with positive height anomalies in the Arctic, personally id have thought there is an increased chance of something properly cold/snowy evolving at some point. A January similar to 1985 sort of pattern, springs to mind, and that had several minor snow events (here in derby at least).

Jan 85 had a 12 day very cold spell with tempertaures sub-zero for much of that time. Also a decent 10 to 15cm snowfall - where I was in Essex anyway.

[sheikhy]

Fantastic 06z up to 240 hours!!cold frosty and snow in places!!best thing about this run it all starts a bit earlier between 96 and 120 hours!

[tight isobar]

To emphasise!! Looking at upper level temps.. at these stages are fraught!! And can/will change.. even dramatically.. and with the jet by now -and indeed sometime b4 we’ll on the missing list . it’s a top place to sit just now . 

Edited December 16, 2020 by tight isobar