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Model Output Discussion 29th December - Into mid-Winter.

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There is a middle ground whereby the outcome is more amplified than GFS but less than ecm/ukmo?  I also thought that there were more GEFS members keen to amplify the ridge further north than I saw on the 06z suite around day 7/8.

the NCEP discussion isn't great to read and many are assuming that ECM will backtrack. The eps this morning were already saying that the op solution was overdone but ukmo 12z raised expectations again. 

I'm afraid we can trust the ops post day 6/7 but the differences are well ahead of that. it's rare that either model proves to be correct with a disagreement like this. Likelihood is that One will quicken and one will slow down. Question remains is whether that completely removes the possibility of getting the ridge far neigh north to advect deep cold as far as the uk. 

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Well my money's still on the UKM/ECM combo every time over the GFS, so providing the ECM sticks with its morning pattern then I expect to see the GFS gradually backtrack over the next 24 hours. If the ECM switches to GFS I'll be surprised but then it is the UK and when it comes to cold how many times have we seen the model predicting mild win out vs. the other way round? Our ability to snatch defeat from the jaws of victory is second to none.

Edited by Gustywind

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2 minutes ago, bluearmy said:

There is a middle ground whereby the outcome is more amplified than GFS but less than ecm/ukmo?  I also thought that there were more GEFS members keen to amplify the ridge further north than I saw on the 06z suite around day 7/8.

the NCEP discussion isn't great to read and many are assuming that ECM will backtrack. The eps this morning were already saying that the op solution was overdone but ukmo 12z raised expectations again. 

I'm afraid we can trust the ops post day 6/7 but the differences are well ahead of that. it's rare that either model proves to be correct with a disagreement like this. Likelihood is that One will quicken and one will slow down. Question remains is whether that completely removes the possibility of getting the ridge far neigh north to advect deep cold as far as the uk. 

Indeed. And that all lends itself to an eventual mid-latitude high. Again...

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Day 5 verification for the past 30 days shows that the vast majority of the time the ECM beats the GFS. But not all the time. There were a few times in the past 30 days where the GFS performed better than the ECM on Day 5. Could this be another one of those times?

ecmwf_gfs_nh_f120_recent.png

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there is a few gefs perbs that bring a snowy breakdown but nothing like the ukmo . Bring on the ecm 

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Some fairly remarkable temp anomalies forecast by the GEFs for N. America with the cold trough warm ridge

gefs_z500a_noram_53.pnggefs_t850a_noram_53.png

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9 minutes ago, LRD said:

:rofl:

GFS better than UKMO? You're a funny guy. GFS may win this battle but it'd be an isolated victory

tbh given the fine lines to get any easterly in this situation id give it a very low chance .gfs does over play and flatten tjings out more than ecm generally but imo id expect a middle ground solution on the ecm with any continued cold going south of the uk.hope to be proven wrong 

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1 minute ago, radiohead said:

Day 5 verification for the past 30 days shows that the vast majority of the time the ECM beats the GFS. But not all the time. There were a few times in the past 30 days where the GFS performed better than the ECM on Day 5. Could this be another one of those times?

ecmwf_gfs_nh_f120_recent.png

Please no! I'm actually quite surprised that NCEP backed the GFS in that short term discussion, given some of the criticism of it in some of the State forecasts over its handling of the US pattern during the last week. Anyway all will be revealed shortly, even if the ECM sticks to its guns we'll have to wait till tomorrow before knowing whether the GFS is properly onboard or whether the Euros have had their biggest failure in years.

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That NCEP update fills me with dread..it will be so so typical if the GFS is right...why why why must there always be problems like this getting cold and snow in the UK. 

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Incredible winter wonderland here Greece ! I hope you can get this Arctic weather this week but northern jet so strong, GFS probably correct sadly !

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GFSvEuros-56to84hr-MajorDiffs-8thJan12z.

Using the ARPEGE on the right each time at +60 and +84 hours, with GFS on the left, this is a visual illustration as to how differently the low from the Pacific is handled by the models on each side of the fence.

The red circles show where GFS has the feature in each case so you can see how ARPEGE differs. The red arrows on the +84 show resultant progression of LP (red arrow, then dark red arrow) and the green arrow HP. Note how the interaction of the Pacific shortwave with the Canadian trough also leaves it in a position where it can support the mid-Atlantic ridge not only holding ground but building to higher latitude, even if only slightly.

ARPEGE actually has a shortwave split off the Canadian trough on the SW tip of Greenland, but retains the ridge signal in the mid-Atlantic behind. GEM is along these lines but then has a vicious push from the west that undoes all the good work.

A tense 15-20 minutes coming up and to be honest even if ECM sticks to its guns, that'll only set us up for further tension as the 18z rolls out.

A saving grace is that we have a properly wintry setup agreed upon for Thu-Fri and this is all about whether we can extend the cold at least through the weekend.

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2 minutes ago, chicken soup said:

That NCEP update fills me with dread..it will be so so typical if the GFS is right...why why why must there always be problems like this getting cold and snow in the UK.

I'm beginning to wish I hadn't posted it now! lol There is still a further update to include their thoughts after the ECM so don't take that NCEP discussion as the final word. And we do have the latest State forecasts which come out aswell. Just because NCEP like the GFS doesn't mean its the correct solution and as I mentioned previously the GFS has not had a good week over the USA.

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When the models show differing solutions my rule of thumb is to back the one which shows the least cold solution and at least 9 times out of 10 you will be right!

Having said that the probable outcome will be a middle ground and to be honest if we can get two or three days of cold and maybe some snow I'll take it.

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The ECM could easily follow the GFS or the UKM but it could be all different by the morning. 

A northwesterly spell is likely to happen Thursday onwards leading to snow for large ares of the country especially the further north and west you are. That bit looks nailed on. I don't see an easterly but I do see several days of high dominated settled weather with plenty of sunshine with temps suppressed more so the further south and east you are.

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It has to be said that nobody on earth can realistically expect to know which way things are going to go when a shortwave feature is involved like it is in the current 3-4 day range. 

If ever you've found yourself wondering just how serious 'internal variability' - that which cannot be anticipated without knowing absolutely everything about the state of the atmosphere and having zero errors in understanding and computing - can be for derailing forecasting efforts, well this now is the best example I've ever seen! :bomb:

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14 minutes ago, chicken soup said:

That NCEP update fills me with dread..it will be so so typical if the GFS is right...why why why must there always be problems like this getting cold and snow in the UK. 

We spend most of the time reading why we should ignore the GFS so don't worry to much!

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ECH1-72.GIF?08-0

Well, the low from the Pacific side of the Arctic certainly seems keen to dance with the Canadian one on this run!

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At 72 hours on ECM it already looks like following the UKMO, if it does it's actually quite frustrating knowing that there is a good chance it is wrong 

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At first glance on NH view, ECM at T96 looks like halfway between GFS and UKMO?

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UKMO and ECM looking very similar but just to the left of Greenland the ECM looks not quite as good and slightly GFS like and the PV in American on the ECM doesn't look great!!

IMG_3967.PNG

IMG_3968.PNG

Edited by Ali1977

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3 minutes ago, radiohead said:

At first glance on NH view, ECM at T96 looks like halfway between GFS and UKMO?

Its the 24 hr steps that make it look that way. The evolution so far looks similar to this mornings run. The energy should still head ne rather than se into the Atlantic at T120hrs.

Edited by nick sussex

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