The hunt for cold - Model discussion (late November)

[Snowman.]

Wouldn't be surprised if we saw Scandi height rises on this run.

Never the less that's two GFS runs trying to build something to the west and slow the Atlantic down, let's hope it's onto something..

Edited December 12, 2018 by Snowman.

[Paul_1978]

1 hour ago, johnholmes said:

Beyond this week then I can see little within a 14-15 day time frame that would suggest any major change to the predicted upper air pattern in that time is a non starter.

All 3 major 500 mb anomaly charts are on the same page you might say, and this has been a feature over several days. TheEC and GFS have now and then suggested the high level blocking to extend west towards Greenland but still with the strong flow over the Atlantic. NOAA has not shown any of this. As you can see in the links below they are all 3 of the same mind, indeed the 8-14 NOAA carries on with this.

To my non specialist eyes the MJO (GFS version) suggests nothing beyond that to suggest any marked change. So the surface weather over the next 2 weeks, after the end of this week, looks unsettled, quite windy at times. The upper air is sourced from a fairly cold area (NE Canada) so much of the time should see most of the country in Polar type air not Tropical, but obviously with pretty deep and fast moving lows there will be variations. But no signal I can see for anything other than transient deepish cold air.

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

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

To be honest I think everyone is cool with that. We are all looking at post-SSW territory now in the "hunt for cold".

[Paul]

This is the current snow accumulation map from the Netwx-MR model for Saturday.

And the prec type animation looking pretty interesting too. All subject to change of course, as this is a tricky one to call. 

 

[Guest]

3 minutes ago, Paul said:

This is the current snow accumulation map from the Netwx-MR model for Saturday.

And the prec type animation looking pretty interesting too. All subject to change of course, as this is a tricky one to call. 

 

Looks good to me. still time for change at this stage tho

[frosty ground]

12 minutes ago, Snowman. said:

Wouldn't be surprised if we saw Scandi height rises on this run.

Never the less that's two GFS runs trying to build something to the west and slow the Atlantic down, let's hope it's onto something..

I would like the pattern to back west a bit so we can get a real nw/se flow on that jet

[northwestsnow]

3 minutes ago, frosty ground said:

I would like the pattern to back west a bit so we can get a real nw/se flow on that jet

TBH  i would take 6z for christmas .. HP ridging in and keeping us cold ..

[shaky]

That scandi high is further west for 1pm friday on gfs 06z compared to last nights 12z for same time!!uppers colder aswell!!yes it wont make much of a difference in the end but could.increse snow chances for a few saturday

[bluearmy]

51 minutes ago, Sweatyman said:

Not a nice read

 

41 minutes ago, swfc said:

Moring John.Im not familiar with the 500mb charts but are they subject to quick changes in the atmosphere ie whats been touted ete on the run up to xmas- new year .tia

The 500 mb charts don’t change too often - especially those derived from extended ens mean data 

the charts posted by JH look to be around 65/35 the favoured route but the clusters continue to throw up ridges ahead of the Atlantic trough across us and just to our east ........ I doubt very much that we will see a simple zonal period with systems crashing into the uk - a couple weeks ago when we had this situation with John referencing these charts and saying he saw nothing in the next fortnight, I had a pretty good idea that we would see a scandi ridge ........ this time I don’t have a pretty good idea what we will see but what I don’t see an east Atlantic trough with the uk stuck on the milder side for the whole period. (As the mean charts do). 

[Snowman.]

7 minutes ago, frosty ground said:

I would like the pattern to back west a bit so we can get a real nw/se flow on that jet

Would only need a few adjustments to make it much more interesting however it offers something largely different to the ECM. So how much can you believe in it.

[johnholmes]

48 minutes ago, swfc said:

Moring John.Im not familiar with the 500mb charts but are they subject to quick changes in the atmosphere ie whats been touted ete on the run up to xmas- new year .tia

No they are 'mean' charts so are usually much more stable. They need using with great care and to remember they are for 500 mb leaving the tricky bottom 18,000 ft of the atmosphere with all its humidity still to be resolved. But with care they are very useful.

[johnholmes]

5 minutes ago, bluearmy said:

 

The 500 mb charts don’t change too often - especially those derived from extended ens mean data 

the charts posted by JH look to be around 65/35 the favoured route but the clusters continue to throw up ridges ahead of the Atlantic trough across us and just to our east ........ I doubt very much that we will see a simple zonal period with systems crashing into the uk - a couple weeks ago when we had this situation with John referencing these charts and saying he saw nothing in the next fortnight, I had a pretty good idea that we would see a scandi ridge ........ this time I don’t have a pretty good idea what we will see but what I don’t see an east Atlantic trough with the uk stuck on the milder side for the whole period. (As the mean charts do). 

I disagree blue, they do not show mild as a mean indeed as I think I commented they show 500 mb air sourced from NE Canada thus more Pm than Tm is how I see it?

Edited December 12, 2018 by johnholmes

[bluearmy]

1 minute ago, johnholmes said:

I disagree blue, they do not show mild as a mean indeed as I think I commented they show 500 mb air sourced from NE Canada thus more Pm than Tm is how I see it?

agree John but I did say ‘milder side’ and given the lack of deep cold air off the northeastern seaboard, I don’t see that air to be likely to be anything other than average/mild when it translates to surface temps here 

[Purga]

GFS Parallel will of course verify for Christmas day

[Met4Cast]

32 minutes ago, Paul said:

This is the current snow accumulation map from the Netwx-MR model for Saturday.

And the prec type animation looking pretty interesting too. All subject to change of course, as this is a tricky one to call. 

 

How well does the NetWx-MR model typically fair when compared with the likes of APERGE/HIRLAM/EURO4? Is the run based off of something like the GFS or is it it's own model entirely? 

Cheers

[Yarmy]

Para going for it again:

[ITSY]

Another FV3 run, another build of Icelandic heights...

[Spah1]

More than happy to see the FV3 toying with heights up to Greenland again. 

[feb1991blizzard]

GFS operational stratosphere charts are looking very good again, very interesting if somewhat bizarre, looks like there's a split signature from bottom up, that moderates in the upper mid strat but then another one right at the very top.

Edited December 12, 2018 by feb1991blizzard

[Tim Bland]

More Christmas cheer from the Para

[Tim Bland]

Its encouraging that the evolution is similar on 00z and 06z runs from the para so it is consistent...let’s just hope it’s not consistently wrong!  

[Singularity]

Putting aside the bizarrely flat ECM 00z, the next major window for added amplification to make a big difference starts at a week's range when we see ridges reaching poleward in the N. Atlantic and perhaps across Alaska too. There's plenty of reason to expect the modelling to increase these ridges and, in tandem, sharpen up the troughs - most notably the one currently being projected to take 'bowling ball' form next week. The UKMO 12z of last night showed us what a sharper version of the trough looks like (but allow for some variation in how far east it is).

Longer-term I think we're seeing the ugly child of Nina-like bias and the journeying of the displaced vortex past the N. Atlantic sector in recent GFS runs, but it's really interesting that FV3 appears much more willing to consider other outcomes; perhaps the bias has been at least partially removed?

Even GFS is making notable moves though - just look at the 06z compared to 00z for +168. A big jump up in Atlantic-Iceland ridging (albeit from near-zero!) and down in the latitude of the trough giving us bother. The model that Carinthian gives us insight on seems on the right sort of track to me with that trough continuing to sink down into Europe and heights rising NW/N of the UK. GFS 06z had a brief go at that before the usual steamrollering on the commence of lower-res (240 hours +).

[Man With Beard]

Can't quite get this idea of heights to the NW 20th-24th Dec to take off ... yet. Looked encouraging last night, but a bit more on the fence this morning:

Clusters 1 and 2 looking rather flat there, with a tendency to deeper lows closer to the UK (wet/windy).

It's a bit up and down at the moment. I'm happy to wait a bit longer.

[Met4Cast]

1 minute ago, Man With Beard said:

Can't quite get this idea of heights to the NW 20th-24th Dec to take off ... yet. Looked encouraging last night, but a bit more on the fence this morning:

Clusters 1 and 2 looking rather flat there, with a tendency to deeper lows closer to the UK (wet/windy).

It's a bit up and down at the moment. I'm happy to wait a bit longer.

For me, as long as we're still seeing some support for heights in the Atlantic towards the period you mention, I'm happy - Will likely take a few days for models to begin running with the expected signal. GFS(P) seems to have picked it up quite well based on the latest 2 runs, ensembles likely to be a little fickle at first so I'm not completely surprised to see the EPS back away slightly compared with last nights run.

I suspect the output for 20th-24th December by the weekend will be looking far less Atlantic dominated by the weekend

[Jonathan Rhodri Roberts]

1 hour ago, weirpig said:

Latest Arpege  similar to its 0z run   Saturday Morning the front turning to snow as it hits Wales.  Not going to ba alot i would have thought  but still nice to see

We're doing a charity walk up Pen y Fan, Brecon on Saturday and now the forecast for the summit is snow (some heavy around midday) throughout the day until early evening when it changes back to rain. Meanwhile 'just down the road' parts of coastal South Wales could reach a balmy 13-14C by Saturday afternoon! Crazy weather

Edited December 12, 2018 by Jonathan Rhodri Roberts

[ALL ABOARD]

13 hours ago, Mike Poole said: