Model output discussion - winter proper underway

[Daniel*]

9 minutes ago, mulzy said:

Ban me for posting an ICON chart if you must but this is close to a very good chart.

I think I read something the ICON is respected by some I may however be mixing it up with another model. That is very close to being very snowy indeed, goes to show how NWP can quickly evolve.

[Duane S.]

As the GEFS roll out, the theme of an increasingly southerly jet and low heights into Central Europe continues. Some interesting permutations in this lot

[northwestsnow]

3 minutes ago, s4lancia said:

As the GEFS roll out, the theme of an increasingly southerly jet and low heights into Central Europe continues. Some interesting permutations in this lot

sounds promising

[danthetan]

On 19/12/2017 at 14:48, danthetan said:

Why people are focusing on charts way out in the ontha and not in the semi reliable time frame 144hr is beyond me. The Alaskan ridge surging into the pole on the last few runs is going to play havoc within the models not worth looking past that timeframe.  

Refering back to my post yesterday regarding the model volatility and alaskan ridge taking todays 12Z UKMO it seems to be advertising with the idea of building heights towards Greenland which sends the jet south and low pressure systems with it this keeping us in colder air. Taking the GFS 12Z  you notice the deep low pressure systems are much less apparent compared with a few days ago, but is less keen on building heights into Greenland. We shall have to wait and see if this becomes the trend.

[northwestsnow]

16 minutes ago, Longtimelurker said:

Wouldn't the cold air be coming down from the North rather than via Scandinavia in this set up? Looks like its coming from the direct North to me but I'm just a noob

Yes im a noob too- without one of the 0's

Anyway- there is some very cold air building over northern scandy on ukmo 144-

The problem is the strong jet streak coming across the Atlantic- we need every bit of helpwe can muster from the ridge which has nosed into Greeny-

We are not going to stop the Lows coming across the Atlantic- we need them to be as far south as possible -

METOFFICE expect the lows to be too far north to give much wintry weather for the UK as it stands,.

But we are still 7 days away so much can change, hopefully for the better- so i can wheel out my favourite icons -and 

[Ali1977]

5 minutes ago, northwestsnow said:

sounds promising

Doesn't look promising by day 10 unfortunately!! Jet steams through. 

[Seasonality]

1 minute ago, Ali1977 said:

Doesn't look promising by day 10 unfortunately!! Jet steams through. 

Well, on the plus side if even day 5 isn't decided yet then day 10 counts as deepest darkest FI.

[feb1991blizzard]

11 minutes ago, s4lancia said:

As the GEFS roll out, the theme of an increasingly southerly jet and low heights into Central Europe continues. Some interesting permutations in this lot

HMM - yes some PM and some runners but a lot of zonal runs, the only one by 270 hrs that looks exceptional is P9

[northwestsnow]

GEM 168

Snow event somewhere i would suggest?

 

[Daniel*]

3 minutes ago, northwestsnow said:

sounds promising

I thought you wrote off up to mid/late January in the moan thread.  

CC did in November however with December good old CFS good bit of reverse psychology. I for one never write anything of you never truly know what may be round the corner. 

GEFS are definitely trending colder, obviously colder further north - the changeover day appears to be on the big day itself.

[Cheshire Freeze]

1 minute ago, Ali1977 said:

Doesn't look promising by day 10 unfortunately!! Jet steams through. 

Ridging from the Pacific side is rarely enough to stop the zonal flow across our side of the hemisphere. Really need a 2 or 3 wave attack on the trop vortex to give us any meaningful chance at seeing anything interesting...which is why I was trying to preach how important maintaining the N Atlantic amplification is/was to retaining a highly disorganised trop vortex. 

Trying to stop the mean zonal flow from here on in is going to be like trying to stop a river current with a pebble. I've said from the outset that a SSW was needed this year after the trop led pattern peters out and I've seen nothing to change my thoughts.

[northwestsnow]

I don't think the 12Z GEFS are showing the jet steaming through at all?

The op was pretty much a mild outlier by the 29th -

Still scope for a wintry spell between the 26- 31st from where im sitting- moreso further north..

[nick sussex]

4 minutes ago, CreweCold said:

Ridging from the Pacific side is rarely enough to stop the zonal flow across our side of the hemisphere. Really need a 2 or 3 wave attack on the trop vortex to give us any meaningful chance at seeing anything interesting...which is why I was trying to preach how important maintaining the N Atlantic amplification is/was to retaining a highly disorganised trop vortex.

Trying to stop the mean zonal flow from here on in is going to be like trying to stop a river current with a pebble. I've said from the outset that a SSW was needed this year after the trop led pattern peters out and I've seen nothing to change my thoughts.

We've got a large pebble!

We're not trying to stop it but divert it further south. Its impossible to avoid the Atlantic pushing a lot of energy east which fits in well with the lagged MJO phase 7 response but the track of that into the UK is still uncertain could be very wet or very white.

Given the huge changes since the weekend then its clear the models are not to be trusted post T168hrs until they settle down.

I think its best to keep an open mind for a few more runs.

[Cheshire Freeze]

1 minute ago, nick sussex said:

We've got a large pebble!

We're not trying to stop it but divert it further south. Its impossible to avoid the Atlantic pushing a lot of energy east which fits in well with the lagged MJO phase 7 response but the track of that into the UK is still uncertain could be very wet or very white.

Given the huge changes since the weekend then its clear the models are not to be trusted post T168hrs until they settle down.

I think its best to keep an open mind for a few more runs.

Well as long as we don't see something like this crop up in the operationals then we at least have a chance of seeing some falling snow

[Glacier Point]

So, tropical forcing has gone really quiet of late, and the pattern throughout November has ended (for how long?).

-ve velocity potential anomalies across 150E abruptly ending and the MJO heading through phases 1-2.

That's a sure signal for dropping angular momentum, and a GWO Phase 2 evolution for the New Year period.

Composite for this and GEFS days 12-15 look exceptionally good matches (unfortunately for those of a cold disposition):

So a mild, wet and windy start to the year looks a reasonably good call, and the longer range GEFS can be supported with confidence.

I'm not totally sold on this being it for the forseeable. The late October - November tropical state was too sustained for it to be a passing phase and I suspect we may pick this up again. The MJO rising through the West Pacific would be a crucial thing here in allowing more of the trough to slide under that ridge to the east and a bit more amplification in the Atlantic. The lack of any cold air to our east noted however.

[nick sussex]

Not to be picky GP but the composite would be colder than the GEFS with the jet track further south and lower heights further into Europe.

Given the jet track is still subject to revision this far out isn't it impossible to know at this stage whether the UK might still at times remain on the polar side of the jet.

 

[ArHu3]

@Glacier Point mjo forecasts from ecmwf and GEFS look very different, GEFS takes it to  amplitude phases 8 and 1  ecmwf takes it to phases 1 and 2 in or close to the circle of death. So which model is right, probably ecm ?

[Duane S.]

3 minutes ago, ArHu3 said:

@Glacier Point mjo forecasts from ecmwf and GEFS look very different, GEFS takes it to  amplitude phases 8 and 1  ecmwf takes it to phases 1 and 2 in or close to the circle of death. So which model is right, probably ecm ?

But all towards the Indian Ocean (albeit via quite different routes). Quite a hike back to the Pacific from there as always, but we'll see.

[tight isobar]

This snapshop paints a very big picture!..

Mjo/and forcing of momentum, looks imo already over-riden,..

The operationals are/have been the most consist-and mark'ed..

Gefsecm tenplates and support have imo been as worthy of old 70's ballon data!???

And given the quite strange/disturbed state of the polar regions/regions...

I'd take guide over the raw op's atm over any other defining factors/data.

My opinion obviously...

But a factual/worthy one.

[Duane S.]

EC not backing down. Punching heights even further into the Arctic circle on the 12z

[Bruegelian]

It would be super funky if we could 'steal' the Alaskan ridge from US/Canada, over the top of the world and into Greenland!

[comet]

2 hours ago, Weathizard said:

Hmmmm... arctic high much stronger on this run. Seems to be getting stronger every run

It comes as no surprise, have been banging this drum for several days now and hopefully we will either see better ridging in the Atlantic in coming days or the Arctic high forcing energy further and further south, If and its a big if things went our way we could see some very wintry charts developing in the days ahead. But one step at a time.

[bluearmy]

The new ec op day 7 looks very much like yesterday mornings day 10 on upper pattern

i love an evolution that accelerates by 36 hours, especially a cold one ! 

[Chesil View]

Typical no sooner do I post about GP saying to look for hieght rises to our north /northeast  for the new year from around the 21st and GP posts to say mother nature has moved the goalposts. Ah well its only the weather.

Edited December 20, 2017 by Broadmayne blizzard

[northwestsnow]

Well GFS is certainly offering more wintry potential than EC tonight!!