Model output discussion - winter proper underway

[Frosty.]

5 minutes ago, Broadmayne blizzard said:

I think I prefered the old Frosty too. lol.

 

In a nutshell, I prefer the new rebooted version of frosty but of course I'm biast..i think the next week or so will be largely mild or indeed very mild at times..don't think anyone is disputing that?..beyond the week ahead confidence drops significantly, as per normal.

Edited December 16, 2017 by Frosty.

[comet]

22 minutes ago, The PIT said:

Well after a few weeks of interesting weather it looks like in for a spell of boring nothing type of weather with mild temperatures and grey laden skies. Bonus if we get any sun next week. Deep lala land does show a bit more interesting weather. GFS with it's normal deep lows blowing the uk away while the ECM doesn't go quite so extreme as it doesn't so far out but at least we do have some transient cooler slots with may produce some wintry weather. Hopefully we will get more application and different types of weather everyone will find interesting. However the emphasis is on the mild side of things.

It has been a great start to the season with several weeks of very entertaining model output and just recently the coldest and wintriest spell of weather for many in the UK unfortunately the timing could not be worse heading towards Christmas to see a pattern change to much more mobile and milder conditions. Hopefully strat forcing will see a return to much more interesting weather and model watching post Christmas into the new year. A fair number of the 06z gefs show what could be around the corner so not all doom and gloom.

[I remember Atlantic 252]

12 minutes ago, Frosty. said:

In a nutshell, I prefer the new rebooted version of frosty but of course I'm biast..i think the next week or so will be largely mild or indeed very mild at times..don't think anyone is disputing that?..beyond the week ahead confidence drops significantly, as per normal.

cool, Frosty, 'ramp' dry weather, today here is absolute washout, worst since child of Nadine, Sept 2012, 'ramp' dry charts!

[Cleeve Hill]

Healthy looking Alaska ridge heading to the pole. Whats the chances for that moving towards Greenland ? The vortex splits nicely on this image to say it could happen. 

[Daniel*]

I never added the annotations but shows how the first half of Decembers has been characterised by cold northerly winds quite impressive really, unfortunately the second half isn’t looking as rosy. 

 

Edited December 16, 2017 by Daniel*

[nick sussex]

I think its best to look at the incremental changes in the nearer timeframe than accepting FI as gospel. The main PV on todays GFS 06hrs run is about 500 miles further to the nw at T168hrs compared to yesterdays run to T192hrs.

More amplitude upstream today than yesterday which suggests the models are slowly increasing that.

Not saying people will be sledging on Christmas Day but that's still 9 days out and I'd wait to see whether this increase in amplication continues.

We're not in a stable pattern, the longwave pattern is set to change and that's not the time to be drawing concrete conclusions.

Normally I'm one of the first to become rather melodramatic in here so lets chill and see what happens over the next few runs.

Edited December 16, 2017 by nick sussex

[northwestsnow]

1 minute ago, nick sussex said:

I think its best to look at the incremental changes in the nearer timeframe than accepting FI as gospel. The main PV on todays 06hrs is about 500 miles further to the nw at T168hrs compared to yesterdays run to T192hrs.

More amplitude upstream today than yesterday which suggests the models are slowly increasing that.

Not saying people will be sledging on Christmas Day but that's still 9 days out and I'd wait to see whether this increase in amplication continues.

We're not in a stable pattern, the longwave pattern is set to change and that's not the time to be drawing concrete conclusions.

Normally I'm one of the first to become rather melodramatic in here so lets chill and see what happens over the next few runs.

I might stump you there Nick

Anyway, all jest aside i think you are spot on as usual.

Bets way i could describe the NWP is fluid- its quite a dynamic set up and it is evolving- meto still keen to suggest the jet digging south towards the end of Dec- i'm a bit disappointed in the 6z GEFS but hey ho.

Hope Feb is right with his suggestion of a scandy high into Jan - although i'm still of the opinion we should be looking in the north Atlantic towards the end of December..

 

[nick sussex]

Heres a comparison of yesterdays GFS 06hrs run and todays, so T192 and T168 hrs:

You can see flat as a pancacke upstream, the PV more organised.

Then today:

You can see the main PV pulled further nw, a bit more amplitude upstream, you can also see heights rising ne of Svalbard.

So that's the trend in one day. I'm not saying it will continue just that its a bit premature to be throwing the towel in just jet.

PS like your new term Feb Iceweigan! Great stuff!

 

 

Edited December 16, 2017 by nick sussex

[feb1991blizzard]

2 minutes ago, northwestsnow said:

I

Hope Feb is right with his suggestion of a scandy high into Jan - although i'm still of the opinion we should be looking in the north Atlantic towards the end of December..

 

BTW I'm not saying its a cert but looking at the Pacific ridge on the NWP, I cant see it holding the PV segment far enough West for a proper Greeny height rise but with the amplification that's likely, the only place the jet looks like it will go is south of uk, thus carving a ridge, the furtherest west I see it being is an Iceweigan ridge which would be great, this ties in with analogues built by gp and loads of others. What I am saying is I cant see any proper cold spell during xmas/

[bobbydog]

10 minutes ago, nick sussex said:

I think its best to look at the incremental changes in the nearer timeframe than accepting FI as gospel. The main PV on todays GFS 06hrs run is about 500 miles further to the nw at T168hrs compared to yesterdays run to T192hrs.

More amplitude upstream today than yesterday which suggests the models are slowly increasing that.

Not saying people will be sledging on Christmas Day but that's still 9 days out and I'd wait to see whether this increase in amplication continues.

We're not in a stable pattern, the longwave pattern is set to change and that's not the time to be drawing concrete conclusions.

Normally I'm one of the first to become rather melodramatic in here so lets chill and see what happens over the next few runs.

i agree nick. if you look at the panel gefs at just 120hrs, there are noticeable differences. by 192hrs the differences are huge. the outcome is far from settled, even in the medium term. at this stage, even christmas is still within the scope for change to something colder.

[Chesil View]

Just now, feb1991blizzard said:

BTW I'm not saying its a cert but looking at the Pacific ridge on the NWP, I cant see it holding the PV segment far enough West for a proper Greeny height rise but with the amplification that's likely, the only place the jet looks like it will go is south of uk, thus carving a ridge, the furtherest west I see it being is an Iceweigan ridge which would be great, this ties in with analogues built by gp and loads of others. What I am saying is I cant see any proper cold spell during xmas/

Loving the term Iceweigan ridge feb. I'm all for one of those.

[Weathizard]

27 minutes ago, nick sussex said:

Heres a comparison of yesterdays GFS 06hrs run and todays, so T192 and T168 hrs:

You can see flat as a pancacke upstream, the PV more organised.

Then today:

You can see the main PV pulled further nw, a bit more amplitude upstream, you can also see heights rising ne of Svalbard.

So that's the trend in one day. I'm not saying it will continue just that its a bit premature to be throwing the towel in just jet.

PS like your new term Feb Iceweigan! Great stuff!

 

 

Good post. But my gripe is even with all the forcing we currently have on the vortex it's not showing much sign of moving fro its current locale. It's pretty difficult to get  cold spell in the UK with the vortex there, and there's pretty much zilch in the ensembles.

Edited December 16, 2017 by Weathizard

[karlos1983]

Following slidergate I decided to take a bit of a break, but still kept an eye on the Models and been in and out of here a few times. 

The Models are painting a bit of a mild picture in the more reliable, but mid/long term they don’t have a clue. 

The ensemble show that quite neicely

After around D5 it starts to get a bit messy, we could quite conceivably be seeing 2m temps of 12-14c or 2-5c and longer term even more spread.

Think the modes are in a state of flux, which usually makes for interesting viewing! Bring on the fun and games! Could be a fun few days ahead. 

[Daniel*]

42 minutes ago, Weathizard said:

Good post. But my gripe is even with all the forcing we currently have on the vortex it's not showing much sign of moving fro its current locale. It's pretty difficult to get  cold spell in the UK with the vortex there, and there's pretty much zilch in the ensembles.

That’s why we’re looking north east it isn’t detrimental. Severe cold of Feb 1991 a good example.

[ACCOUNT DELETED]

Swansea GEFS 6z table show a strong high pressure by the 21st but 1047mb on one run, I honestly can't see it being that high lol nevertheless it's very likely we are heading for a calm and hopefully dry period just as long as we can avoid the constant days of drizzle / fog, that often was the case back in Autumn when high pressure developed and we had to wait until a low to arrive which took up to a week, but unbelievably it brought a few dry, sunny and very mild days once the initial front went through!! 

Edited December 16, 2017 by Draig Goch

[comet]

ah gfs finally beginning to smell the coffee with the extra amplification into the Arctic from Alaska (pacific side) should be a much better FI we will see.

[Johnp]

Vortex slightly further West on this run and we at least get a frosty start to Xmas day.

Also more signs of the Pacific ridge than on the 6z.

[feb1991blizzard]

Here comes the digging atlantic trough.

[Singularity]

 

Yes... the Pacific ridge is picked up a bit better on this run although it still has some work do to in this respect.

This brings the run closer to keeping the vortex lobes separate in the 8-10 day range but it's unlikely that a scenario can be reached in which low heights don't transfer across at all from Canada. Instead, the process to look out for is the ridging from the Pacific side interfering with the Canadian lobe, triggering a collapse with some low heights escaping toward Scandi or Europe while the rest gets held back in the western N. Atlantic or across N. America (former more likely this time around, due to the shifted tropical forcing location and intensity compared to those of the past fortnight).

GFS, being GFS, will likely have a hard time capturing this interference and collapse, but to be fair to it, other models often struggle as well in such situations - just look at the 00z ECM for example. Not that a wholesale transfer of a deep trough can be ruled out, of course - it's just that the outcome I've suggested seems more plausible to me at this stage. I could well be wrong on this (I'm only human, after all...).

Into lower-res and GFS is also making a mess of the Arctic profile... again, which is probably down at least in part to the low-GLAAM bias that becomes most evident when the GWO is cycling around with GLAAM spending a little time in what is expected to be only weakly negative GLAAM, but is nearly always modelled by GEFS/GFS to be more negative.

Let's see if it can recover the situation at least up there as per the 06z - that it did so on that run was a good sign I believe that the tropical forcing mechanism has a good chance of coming through at some point in the next few weeks (most likely next two weeks).

[daz_4]

Nah, just another downgrade. Cold air is too far east.

2 days ago 

Today 

Another disappointing run.

[swfc]

8 minutes ago, feb1991blizzard said:

Here comes the digging atlantic trough.

The high over Europe is to far south to be pushed north feb

[beng]

Longer range GFS is complete nonsense with a relative heatwave heading to Moscow. Experience says there's zero chance that's going to happen, not like that anyway.

Edited December 16, 2017 by beng

[northwestsnow]

8 minutes ago, feb1991blizzard said:

Here comes the digging atlantic trough.

I honestly dont think this scandy high is happening feb..

The block is going to be of no benefit for the UK its consistently being progged way too far east resulting in us getting an absolute soaking- no thanks!

[feb1991blizzard]

^^

Yes dyer run that.

[nick sussex]

The GFS continues to add more amplification upstream. Its not a given that the low will bomb to the west and it did try to disrupt before being powered up by the PV lobe over Canada.

Remember here if more amplification is added its likely the low to the west wont act the same as it could be separated  or take longer to deepen.

My advice stick to see if these early changes continue because there could be a tipping point.