Model Output Discussion 29th December - Into mid-Winter.

[Weathizard]

GFS and UKMO look fairly similar to me at first glance at t120, more energy going over the top on the GFS but broadly similar

[bradymk]

The GFS still much flatter and not as good as the euros but every run it's becoming more amplified and slowly creeping towards the other outputs.

One difference every run that you can notice is that if you look at that low that crosses the south on Saturday on the GFS, on previous runs, the precipitation from it went south west to north east through the whole of the UK almost. Now on the 12z the precipitation "slides" down along parts of south western UK only.

[booferking]

5 minutes ago, Weathizard said:

GFS and UKMO look fairly similar to me at first glance at t120, more energy going over the top on the GFS but broadly similar

Big difference look at the russian high right through siberia and ukmo also has us in a gentle NW Flow still cold gfs is not.

The 144 even more stark

Edited January 9, 2017 by booferking

[phil nw.]

9 minutes ago, Mucka said:

Also UKMO GFS comparison at 96h. UKMO has a Northerly driving throught he heart of France. GFS has a Northwesterly through Germany!

Hope GFS is being rubbish and I would have to back UKMO at this range.

A good illustration that with a  a little more ridging as on the UKMO we see a sharper Arctic plunge.Not a bad start of the evening- even on the flatter GFS we see -4 uppers across the UK by T48hrs with -6 approaching from the north west.

[winterof79]

Improving heights

 12z

 06z

[Weathizard]

Just now, booferking said:

Big difference look at the russian high right through siberia and ukmo also has us in a gentle NW Flow still cold gfs is not.

Still ends up in a broadly similar place at t144 though to my eye, high pressure ridging over us again!

[beng]

http://www.meteociel.fr/modeles/ukmo2.php?nh=1&ech=144&carte=1021

 

I like the UKMO 144 chart - bit of trough disruption to our West - 168h might develop a decent cold block to the East - maybe not enough amplitude for a proper Easterly though.

[Mucka]

10 minutes ago, phil nw. said:

A good illustration that with a  a little more ridging as on the UKMO we see a sharper Arctic plunge.Not a bad start of the evening- even on the flatter GFS we see -4 uppers across the UK by T48hrs with -6 approaching from the north west.

Yeah quite a stark difference illustrated by the trough and agree it is a good start with UKMO much better than this mornings run IMO. 

I thought UKMO 12z would show better amplification than it does from T96 because of it but Atlantic forcing is very strong 120/144, 

If it had been a little less progressive through that stage we would of seen the low between Iceland and Greenland at 96h on a more Southerly trajectory and further West which would also have helped amplify upstream - there was potential for a really stunning 144 so I hope it is on the right track.

Edited January 9, 2017 by Mucka

[Man With Beard]

Can't post chart at the moment but GEM at T120 (Saturday) is worth looking at - it has that diving low in cold air, and a N/E wrap around as it exits the SE corner.

Well surely it has as good a chance of being right as the rest of them, such is the disagreement!

I think it's going to produce a proper Scandi High, too! (EDIT: OK, not quite, darn Azores High spoiled that one!)

Edited January 9, 2017 by Man With Beard

[winterof79]

2 minutes ago, Man With Beard said:

Can't post chart at the moment but GEM at T120 (Saturday) is worth looking at - it has that diving low in cold air, and a N/E wrap around as it exits the SE corner.

Well surely it has as good a chance of being right as the rest of them, such is the disagreement!

 Was just looking at it myself

Edited January 9, 2017 by winterof79

[phil nw.]

10 minutes ago, Mucka said:

Yeah quite a stark difference illustrated by the trough and agree it is a good start that UKMO is much better than this mornings run IMO. 

I thought UKMO 12z would show better amplification than it does from T96 because of it but Atlantic forcing is very strong 120/144, 

If it had been a little less progressive through that stage we would of seen the low between Iceland and Greenland at 96h on a more Southerly trajectory and further West which would also have helped amplify upstream - there was potential for a really stunning 144 so I hope it is on the right track.

Yes the following Azores ridge still seems destined to head our way which in fairness has been one consistent trend.

I am just keeping an eye to the east those Russian heights are certainly pummeling the vortex on that side but as yet not heading this way.

I think the best we can hope for after the northerly is to retain some surface cold near the high for now.

Edited January 9, 2017 by phil nw.

[Summer Sun]

GFS and UKMO are not too far apart at t144

[Ravelin]

3 minutes ago, Man With Beard said:

Can't post chart at the moment but GEM at T120 (Saturday) is worth looking at - it has that diving low in cold air, and a N/E wrap around as it exits the SE corner.

Well surely it has as good a chance of being right as the rest of them, such is the disagreement!

I think it's going to produce a proper Scandi High, too!

Here you go...

 

[Nick F]

12 minutes ago, beng said:

http://www.meteociel.fr/modeles/ukmo2.php?nh=1&ech=144&carte=1021

 

I like the UKMO 144 chart - bit of trough disruption to our West - 168h might develop a decent cold block to the East - maybe not enough amplitude for a proper Easterly though.

Can't see any trough disruption to the west myself? The trough looks too positively tilted for disruption. Looks like the ridge over the UK may nose further east like GFS though.

Seems to be a general theme for the GFS over last several runs and UKMO over last few runs for the Azores high to ridge in after the cold NWly later this week, and for many parts to become dry and cool and frosty at night, while the NW is prone to a milder SWly flow with Atlantic fronts bringing rain.

The Azores high ridging NE is no good for getting a Scandi high and easterly when there's so much jet energy piling NE between Iceland and Scotland anyway.

00z ECM was trending down a similar route, so perhaps finally we will have some agreement this evening in the medium range unless 12z ECM wants to make more of high pressure to the NE.

Edited January 9, 2017 by Nick F

[johnholmes]

2 hours ago, GrrClark said:

 

My apologies if being misleading in my post.

I do appreciate that there are models within the forecasting suite that do have sufficient resolution to factor in local scale features, but my understanding was that the hemispheric modelling at day 5 is not run at a resolution that would consider that.

Always happy to be corrected.

Best I actually quote for the information of everyone from the UK Met O web site, this link explains things

http://www.metoffice.gov.uk/research/modelling-systems/unified-model

[Snowman.]

8 minutes ago, Man With Beard said:

Can't post chart at the moment but GEM at T120 (Saturday) is worth looking at - it has that diving low in cold air, and a N/E wrap around as it exits the SE corner.

Well surely it has as good a chance of being right as the rest of them, such is the disagreement!

 

The 850s are a bit warmer because of the GEM bias but -6 pretty widely I would assume, defo cold enough to snow especially at night.

 

 

 

 

 

[knocker]

5 minutes ago, Nick F said:

Can't see any trough disruption to the west myself? Looks like the ridge over the UK may nose further east like GFS though.

Seems to be a general theme for the GFS over last several runs and UKMO over last few runs for the Azores high to ridge in after the cold NWly later this week, and for many parts to become dry and cool and frosty at night, while the NW is prone to a milder SWly flow with Atlantic fronts bringing rain.

The Azores high ridging NE is no good for getting a Scandi high and easterly when there's so much jet energy piling NE between Iceland and Scotland anyway.

00z ECM was trending down a similar route, so perhaps finally we will have some agreement this evening in the medium range unless 12z ECM wants to make more of high pressure to the NE.

I think that a pretty fair assessment and would just like to add the position of the surface high is quite important regarding surface wind and possible min temps.

Edited January 9, 2017 by knocker

[feb1991blizzard]

3 minutes ago, johnholmes said:

Best I actually quote for the information of everyone from the UK Met O web site, this link explains things

http://www.metoffice.gov.uk/research/modelling-systems/unified-model

I was reading a page similar to this the other week on the UKMO site and couldn't find the MOGREPS 15d model, no wonder - its retired, surprised that they haven't replaced it, being that they don't rate the GEFS you would think they would want something for comparison to the ECMWF extended eps because I'm lead to believe the EC46 is the same data from eps rolled forward in time or pergaps I have this wrong?  Maybe they rate the GLOSEA5 as a mid range model as well.

[IDO]

Beginning to look like D6 plus is settling down. Best way to look at it is via the NH; the three 12z models at T144:

We know the PV has been mobile all year so we know it is unlikely to set up shop at the above locale. So what will happen? With strong forcing from US heights the PV is going to get pushed east, I don't see how that can be avoided. That will be the next phase, the PV moving across to our north with another Azores wave pushing SW to NE. All three charts hint at this, they are all synoptically now on the same page. Of course micro-differences and timing issues aside may mean a big difference as to snow potential in this 2-3 day window, but it looks like another heights -v- PV fight. Bearing in mind these have been numerous over the last 6-8 weeks, if the pattern is maintained, then a high close to the UK/Euro, slowly sinking and then a zonal period as the PV energy eases over the top; maybe the zonal a bit longer than before due to the more organised PV?

[Kieran]

12z GFS showing potential for snow showers to move south-eastwards into the Midlands. If this trend continues I think many more of us could see some wintry showers on Thursday and into Friday.

Edited January 9, 2017 by Kieran

[Eskimo]

5 minutes ago, Kieran said:

12z GFS showing potential for snow showers to move south-eastwards into the Midlands. If this trend continues I think many more of us could see some wintry showers on Thursday and into Friday.

Being in Birmingham this week, I'm hoping they can penetrate far enough into the west Midlands. The upper air wind speeds look fairly strong as we progress through Thursday.

[Summer Sun]

Not to be taken as a given of course as snow could fall just about anywhere later this week this is the peak of the snow accumulation on this run from GFS

Yesterday for comparison

Both charts up to Saturday 13:00

[JeffC]

4 minutes ago, Summer Sun said:

Not to be taken as a given of course as snow could fall just about anywhere later this week this is the peak of the snow accumulation on this run from GFS

Yesterday for comparison

Both charts up to Saturday 13:00

touch of a downgrade that...

 

[MattTarrant]

5 minutes ago, Summer Sun said:

Not to be taken as a given of course as snow could fall just about anywhere later this week this is the peak of the snow accumulation on this run from GFS

Yesterday for comparison

Both charts up to Saturday 13:00

Very true, though if you consider the Met Office Yellow warning of snow that stretches into the South West suggests that 2-5 cm of snow could fall even at lower levels.  The above charts suggest otherwise, i would go with the Met office(UKMO). 

Plus the GFS has a more North Westerly component to it which hinders snow potential in the south west, UKMO more Northerly. 

Edited January 9, 2017 by MattTarrant

[Gibby]

For my part I think there will be a lessening of the cold later in the weekend as the High pressure moves in cutting off the north flow. I don't see it setting up a mild SW'ly though. More likely is a build of High pressure back and up across the UK early next week perhaps preceded by a runaway disturbance moving SE along a warm front with an attendant band of rain and snow with the South and East maintaining a cold feel afterwards with light winds eventually from maybe a SE point or at least 'faux' cold in calm anticyclonic type conditions. This might be harder to achieve for our northern contingent as SW winds have a greater chance of getting a hold up there at least for a time. Remember the continent is very cold and any ingress of mild air is going to have a fight on it's hands to battle the heavy weight of cold air over there as there looks to be no driving forcing Low pressure from the Atlantic accompanying any mild air at the weekend or start to next week. I expect the ECM run to show something along the lines I've mentioned here in an hour or so. I concede though that it is unlikely to show any noteworthy Easterly but we can only hope.