Model output discussion - 1st December onwards

[SMU]

Luke warm now from the GFS as we see more undercutting ...

just a bit more please.... 

This is so nearly an epic chart-

 

 

[Iceberg]

A classic set up from gfs at t144-168 reliable time frame as well, sweet, clean and direct with superb Atlantic energy direction.

 

Edited December 27, 2015 by Iceberg

[radiohead]

Definitely an improvement since yesterday for cold potential down the line on this run. 

[northwestsnow]

Oh the momentum is moving in the right direction imho, im starting to get that feeling this block is going nowhere fast, models starting to sniff an undercut  

[bluearmy]

Perhaps too much attention in the detail.  Over the past few days we have seen the models coming around to the undercut idea and the euro high has retrogressed to become Azores high and sunk South at the same time. Whilst knocker shows the mean trough to be nw/se through the UK, one shouldn't forget that this is a mean and allows for a euro trough to our se being re enforced by sliders. and that doesn't require anything other than just below average uppers at this time of year to deliver frontal snowfall as the wind backs se off the continent.  We don't need deeply cold uppers to bring really wintry conditions if the pattern falls right. In my eyes, we are drifting in that direction. Add to that the general trend of the extended eps to raise heights across the polar fileld and the nwp currently bringing some Xmas cheer to coldies. 

 

Incidentally, GEFS, ECM, GEM ens all have -AO/ -NAO combination into week 2. The NAO not as low as the AO which is still a decent result given the upstream vortex strength. 

Edited December 27, 2015 by bluearmy

[northwestsnow]

Just now, bluearmy said:

Perhaps too much attention in the detail.  Over the past few days we have seen the models coming around to the undercut idea and the euro high has retrogressed to become Azores high and sunk South at the same time. Whilst knocker shows the mean trough to be nw/se through the UK, one shouldn't forget that this is a mean and allows for a euro trough to our se being re enforced by sliders. and that doesn't require anything other than just below average uppers at this time of year to deliver frontal snowfall as the wind backs se off the continent.  We don't need deeply cold uppers to bring really wintry conditions if the pattern falls right. In my eyes, we are drifting in that direction. Add to that the general trend of the extended eps to raise heights across the polar fileld and the nwp currently bringing some Xmas cheer to coldies. 

Agreed blue we are moving in the right direction, undercutting is todays buzzword methinks.

[Ice Day]

Some decent energy going under at 204hrs.

And unlike last year, there's some very cold air to tap into.  

As has being said, there is a momentum shift this morning towards cold, but we've all been here before.  This is a complex set up so lots that can go wrong.

Edited December 27, 2015 by Ice Day

[Snowman.]

Reluctant to slide

Plus where no entering low-res so it could attempt to push the whole thing under that's going to be fun to watch.

Edited December 27, 2015 by SN0WM4N

[london and south east kent]

That cold blob is close east and south east uk

[Polar Maritime]

Not much to add other than it's been a very interesting few days model watching as they toy with background signals, And this morning the chances look much stronger for wintry conditions to reach the UK into the new year. Still lots to be resolved over the coming days reg detail, But the big picture is certainly looking promising as the jet sinks South dragging in colder air at last. 

Edited December 27, 2015 by Polar Maritime

[KyleHenry]

One point of note from GFS and GFS(P) is that from 108 hours onwards the ridging shows a constant 1050 mb.

 

Edited December 27, 2015 by KyleHenry
Same chart

[nick sussex]

The GFS 06hrs run a step in the right direction.

Latest MJO forecast smoothed out so as to remove Kelvin wave interference:

This is somewhat different to the normal dynamical model forecasts, the faster progression into phase 6 shown by them is likely to be Kelvin waves rather than the MJO itself.

In terms of the GFS 06hrs run a bit more trough disruption and it would be an excellent run but at least positive signs.

 

[shaky]

Gfs control follows the op run with an undercut and cold air further west into the uk!!!the beast from the east is slowly awakening!!:0

[knocker]

What a scenario!! You have the upper trough running down the N. Sea to southern Spain with the jet zipping around it's western flank and the HP ridging north from SE Europe. Just ripe for a low to nip down the trough and stall to the SE bringing an easterly snowfest to England. Really doesn't bear thinking about.

[chrisbell-nottheweatherman]

12 hours ago, fergieweather said:

No, it's because 12z ENS clusters, MOGREPS and GloSea5 prefer that (ultimately zonal) outcome. The NW flow signal actually appears more compellingly into late Jan (in eg latest EC Monthly). There remains scant support in 12z EC-ENS for any 'full-on' easterly, but as noted in my previous posts, that doesn't discount it. So, until such supporting evidence dominates (or at least becomes a noteworthy minority signal), then we have to run with consensus. Bear in mind GFS has shown very marked inter-run oscillations for a while, and in any event, is never followed as a 'trusted' guide post-T+144 because (unlike EC or MOGREPS, or GloSea5 for that matter) it's not a bespoke medium range tool. Yes: it *may* be right this time re easterly Op runs of late, but that's shaky ground to base a public forecast upon. What happens aloft stratospherically may be another matter.

The next few days look far more eye-catching in any case, forecast-wise. Given events already today, frankly whatever unfolds early Jan can happily sit on the back-burner for now....!!

Thanks indeed Ian - much appreciated, and I find it instructive that you've now added that the Met Office don't take GFS too literally past T+144 to your previous comments regarding ensemble means being limited in their instructive capability without taking clustering into account.  To clarify, I wasn't referring to an easterly, which I never thought would happen within the next fortnight anyway, but rather a veering of mean flow to the west or WNW as opposed to this south-westerly/SSWerly flow we've had so much of at late.

[phil nw.]

25 minutes ago, Polar Maritime said:

Not much to add other than it's been a very interesting few days model watching as they toy with background signals, And this morning the chances look much stronger for wintry conditions to reach the UK into the new year. Still lots to be resolved over the coming days reg detail, But the big picture is certainly looking promising as the jet sinks South dragging in colder air at last. 

This is now becoming a definite trend PM.

A look at the 00z gefs ht anomaly forecasts in 3 day blocks from the NW xtra area show the Atlantic troughing starting to extend se in the first week of January as the block becomes more influencial.

see as time goes on how the +ve height anomalies spread across to the north.

These are of course only anomalies against climate and the surface detail will likely vary so we still need to see where exactly the path of any lows will be as they run in against those heights.As Captain S said earlier we have to get lucky and hope that they run far enough south so that we advect easterly cold to the north of the lows.

Some encouragement too from the surface temperature anomaly charts for Europe again 3 day blocks.

plenty of cold creeping across the continent from the east and very close to the UK.Finally a look at Aberdeen and Warks expected average 2mt temperatures.

 so a downward trend to something colder looks likely but the pattern is still on the change so i think plenty of scope for something Wintery to develop as the vortex continues to show signs of weakening.

[nick sussex]

I think at the moment there are two complications in terms of advecting the coldest air westwards. The direction of the lower heights associated with that deep cold which runs westwards. This is why the orientation of the high is so important, the high needs to be maintained running more ne/sw and as far west as possible. Those lower heights will try to edge more nw on the western flank of the high.

The trough disruption of course is the make or break because without that the pattern gets edged eastwards.

I think at the moment regardless of the Met Office lack of interest this IMO is the best chance all winter to get some wintry weather more UK wide.

The block to the ne has actually increased in strength and with the background MJO the stars might align favourably, these types of set ups though are the most complicated for NWP to handle and for those fellow old timers in here like myself we have been here many times before.

I'd urge some caution even if the outputs upgrade the potential, until we're within T96hrs things could still go pearshaped .

[gottolovethisweather]

1 hour ago, Polar Maritime said:

And this morning the chances look much stronger for wintry conditions to reach the UK into the new year.

Yes PM, something is a-changing up above us in the H500 pattern and for several days now, I have not once failed to believe that something better for coldies is on its way at the turn of the year. Obviously, at first a drier pattern would be nice to see and then we can worry about the specific surface details as we move on through time. Some runs drop the deepest cold patterns, some runs drop the Easterly signal, nothing new there.

 

The wider view of things indicate the synoptic patterns are set to change across Europe (at last!) come mid to late next week and the Atlantic for once (at least for a few days) will struggle to push its fronts Eastwards over us. Watch Tuesday's low and look where that goes, up towards the North Pole? Tuesday through Thursday could be very wet out West unfortunately, which is one to watch. Thereafter other forecast surface developments seem to increasingly head towards France or Spain, which means the Jet is having a tendency to dive South. Baby steps, but hopefully some joyous news for once, for those desperately needing a change to our current set up. 

 

Edited December 27, 2015 by gottolovethisweather

[Catacol]

3 hours ago, IDO said:

 

The MJO signal is now weakening with most models (COD after D7)

 

You're gonna have to back that one up - because of the 13 forecasts available only the Canadian model comes close to a COD forecast.... and it takes to day 10. The others are variable, but most of a decent strength. 

[Polar Maritime]

8 minutes ago, phil nw. said:

This is now becoming a definite trend PM. So a downward trend to something colder looks likely but the pattern is still on the change so i think plenty of scope for something Wintery to develop as the vortex continues to show signs of weakening.

Very much agree Phil, Indeed, And important as you say with "the pattern still on the change" is for members not to get to hung up on detail per in-trim run. The big picture looks promising/interesting as we move into January.

Edited December 27, 2015 by Polar Maritime

[chrisbell-nottheweatherman]

34 minutes ago, nick sussex said:

The GFS 06hrs run a step in the right direction.

Latest MJO forecast smoothed out so as to remove Kelvin wave interference:

This is somewhat different to the normal dynamical model forecasts, the faster progression into phase 6 shown by them is likely to be Kelvin waves rather than the MJO itself.

In terms of the GFS 06hrs run a bit more trough disruption and it would be an excellent run but at least positive signs.

 

Hi Nick, as mentioned above, IDO on the previous page of this thread mentioned the MJO entering the COD post-D7.  Any sign of that (obviously not in the CFS ouput you posted, but elsewhere)?

Edited December 27, 2015 by chrisbell-nottheweatherman

[Shuga ice]

One week of mild mush before turning very much colder from the east.  There looks to be good snow opportunities for many parts of the UK.  The met office need a bit more time before announcing this but based on the cold solutions that are building momentum, I expect colder weather in their forecasts by the end of the week.

[IDO]

12 minutes ago, Catacol said:

You're gonna have to back that one up - because of the 13 forecasts available only the Canadian model comes close to a COD forecast.... and it takes to day 10. The others are variable, but most of a decent strength. 

Just a sense of trend, the signal is hinting at the COD after D7:

JMANUKME:NCPE:

JMAN:ECM mean

 

 

 

Edited December 27, 2015 by IDO

[nick sussex]

Just now, chrisbell-nottheweatherman said:

As mentioned above, IDO on the previous page of this thread mentioned the MJO entering the COD post-D7.  Any sign of that( obviously not in the CFS ouput you posted, but elsewhere)?

The amplitude of the MJO varies depending what model you look at, theres good agreement to get that into phase 7 but the issue is the strength of it.

The NCEP MJO expert however suggested the signal should remain robust for the next two weeks in his update last Tuesday. In terms of the smoothed out version that was designed after research into how to separate out the Kelvin wave aspect of the MJO, its a complicated formula, the research suggests the normal dynamical forecasts include too much of the Kelvin wave .

Because this moves more quickly this could explain why theres the differences between the smoothed out version versus the normal models.

The MJO isn't an exact science and theres still arguments amongst scientists( whats new!) However my view is that the NWP is currently catching up to the real MJO versus the Kelvin wave.

This is why I've been a bit more optimistic over the last few days because essentially there was room for upgrades.

We'll see over the next few days whether we can continue to see that Russian block strengthen and whether that trough disruption is more favourable.

 

[bluearmy]

Parallel ECM op doesn't get the proper cold west towards nw Europe.  It's not on the same page as the op

re iterate that within the upcoming broad setup, to get snowfall, we don't need the deep cold this far west if we get sliders.