Model output discussion - Closing in on Christmas

[alexisj9]

3 hours ago, That ECM said:

T144 all 3. Enough difference here to say beyond is JFF.

It's all to do with how the low phases, as you can see here, the phasing happened earlier and has made a stronger low on the ECM, and that changes the pattern.

[mushymanrob]

Well this must add weight to the gradual evolution of something cold... not there yet but if this evolution continues (as compared to previous charts which i dont have) then a proper cold spell is certainly realistic.

Pressure is rising over Southern greenland and theres a positive pressure anomaly connecting that to the main high over Northern Siberia. Mean upper trough to our East... all we need now is for those green contour lines to open up/shift South of the UK, and a winters spell reminiscent of the mid 80's is surely on the cards.

 

[Skullzrulerz]

Where's the ICON too?

[chris55]

ECM 850s (northern England) we can clearly see how the Det and control are both ramping up that Low giving the uptick in temps, while the main ensemble cluster keeps things cooling, more like GFS.
 

[credit Matt Hugo twitter]

The modelling of this Low is crucial. Hopefully it just fizzles out lol. 

[pureasthedriven]

32 minutes ago, tight isobar said:

Depending on ya views/-what occalation you prefer..and singular members for orbit!!. Is always a million miles from 1/to the other interpretation..     gage the mjo.. then revert to geopotential 500,s.. and compare within the time given @december late...   the orbit stamped.. can be 1 member converting...   in simple terms.. look at geopotential heights... then take the madden oscillations, as background noise..!!!! All imo ... but worthy..   @classic blocking.. and potential..@ pun intended

If I read you right TI, 500s as the main course, MJO as the red wine gravy? 

[alexisj9]

2 hours ago, frosty ground said:

A failure  in modelling at day 10?

 

 

No the crucial time now looks to be 144, in the 6z it be 138.

[Captain Shortwave]

Still looks decent for a plunge of colder air around Christmas. Still a lot of questions in regards to both potency and longevity. However there is a complication in the form of an area of low pressure that exits of the US in a day or so time.

Shown here on the UKMO at day 6

 

The low up to day 6 has not really engaged the strong northern arm of the jet stream. A question is will it interact or won’t it? If it does the low should track quickly through the U.K. However it may not and as such will remain slow moving and track south of the U.K. This system will likely create a question in regards to the timing of the cold exiting the Arctic, and also how far south it can push.

 

[TSNWK]

1 minute ago, alexisj9 said:

No the crucial time now looks to be 144, in the 6z it be 138.

Welcome your views if you can then at 138. I and suspect others struggle with access to meteocile the day.

Whooper of 6z is rolling..

[frosty ground]

5 minutes ago, alexisj9 said:

No the crucial time now looks to be 144, in the 6z it be 138.

Can you expand on that?

[tight isobar]

Phasing of the waves . Are perhaps a bonus going forward.. with trough and drop.. and azhp enconter.. can only go 1 way.. if the 6z has this to palm...

[chris55]

Atlantic low looks to be separating on the 6z should stop it ramping up and pushing north

[tight isobar]

And that’s on now all ejection.. via crucial time frames...  

[johnholmes]

I don't normally do daily 500 mb ipdates but for once!

Tue 15 th

Ec-gfs and ec has dropped the ridge upwind of the uk so a fairly flat w’ly now; gfs much as mon

Noaa has really gone for meridional flow just upwind of the uk; the flow in the far west shows a slight increase in the ridging and a rather deeper trough west of this

Noaa is not often the wrong model out of the 3. Not sure what ec is doing, gfs keeps its chart from Monday in most aspects, particularly near the uk. So I’d go for  a flow n of w into the uk with 6-7 days from now, about 40% as of this morning!

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

[alexisj9]

13 minutes ago, frosty ground said:

Can you expand on that?

The low in this run leaving the United States looks to have not fully phased, and is separating off, so it should stay south, and should be a good run. We'll see of course.

[chris55]

I’m in micro analysing mood lol

Comparing GFS 6z 144 with ECM 144

Clearly 6z quite different with the low disrupted/less developed. Much better.

GFS

 

ECM
 

 

[mountain shadow]

25 minutes ago, mushymanrob said:

Well this must add weight to the gradual evolution of something cold... not there yet but if this evolution continues (as compared to previous charts which i dont have) then a proper cold spell is certainly realistic.

Pressure is rising over Southern greenland and theres a positive pressure anomaly connecting that to the main high over Northern Siberia. Mean upper trough to our East... all we need now is for those green contour lines to open up/shift South of the UK, and a winters spell reminiscent of the mid 80's is surely on the cards.

 

Whilst on the face of it, this looks decent, it is not necessarily mean we will get proper cold.

There is a weakness between the two centres of higher heights (Black line) and the jet may flow between them with low pressure moving into the Atlantic as a result.

The red line shows how the jet may run and we could actually get less cold air pulled in as  a result.

 

[sheikhy]

Much much better 06z gfs!!low sliding inviting the cold spell in from the north!!way better than the ecm!!seems ecm was a big outlier between 144 and 192 hours so thats good news!!

[tight isobar]

Tri-vortex ??   Coming up.. 

[Man With Beard]

Studying the ECM individual ensembles this morning, there's considerable disagreement in the D9-D10 period, far too much to close in on even the general evolution. Yes, plenty of snow potential members remain with robust heights to the W or NW, but equally as many members that throw any trough across the Atlantic and the ridge falls as soon as it rises.

I note there's quite a few new posters this year, so it's worth underscoring what many of us "long-termers" have seen over many years - Out of all the many ways the NWP leads up the garden path, the North-Atlantic ridge is the most notorious of all. In at least 50% of cases, the models (especially the ECM) will have a tentative ridge showing when at D7-D10, but will then out of nowhere pluck another trough out of Canada when we get within D5-D6, and the pattern gets flattered, and potent northerlies get reduced to NW hill snow and one night of frost for everyone else.

My personal key thing to look for is a 1030mb high on the mean chart of the GEFS and ECM, which stays that strong for at least 24 hours, and which is centred W, WNW or NW, but not WSW or SW. If that happens, I'll call it as early as D8. If it doesn't, I'd hold on until D5 in case the spoiler low emerges from Canada.

[blizzard81]

14 minutes ago, sheikhy said:

Much much better 06z gfs!!low sliding inviting the cold spell in from the north!!way better than the ecm!!seems ecm was a big outlier between 144 and 192 hours so thats good news!!

Trouble is I personally would never bet against an ecm op when it goes against the ens grain when showing something less favourable for cold. Especially when it is backed up by the control. A nervy day or 2 ahead for those who wish for more than a short lived cold snap. 

[chris55]

Lovely crisp Christmas morning on 6z. Could be some snow flurries about as well.

[PiscesStar]

29 minutes ago, chris55 said:

I’m in micro analysing mood lol

Comparing GFS 6z 144 with ECM 144

Clearly 6z quite different with the low disrupted/less developed. Much better.

GFS

 

ECM
 

 

Care to take a punt on a white Christmas? 

[chris55]

Boxing Day the same, very festive and crisp

[IDO]

The ecm op this morning was puzzling as it never really convinced with any forcing to Greenland and in fact killed off the Greenland High altogether:

  mean ecm d10: 

It railed against its mean. However, the gfs was also progressive with erasing heights there, so it was maybe more than a blip. The 06z has continued this change though less progressive with the Atlantic and at d10:

...more of a split flow rather than the tPV chunk sweeping through as on the 0z? It is as if the models have had a eureka moment in spotting the next stage and are figuring it out? Hence the entropy. Needless to say, if this is the way forward we want more undercutting of the Greenland wedge to at least dig the jet NW>SE to keep the cold locked in, as the Atlantic ridge does not look a standing feature?

[chris55]

1 minute ago, Snowfish2 said:

Care to take a punt on a white Christmas? 

Looks possible. Odds higher than some years where a clear zonal pattern is locked in. 
The development of this Low is going to give the models some trouble I would think, so things far from certain (as always lol.)