Model Output Discussion - The Run In To Christmas

[damianslaw]

Models continue to show all sorts of scenarios - most notably ECM today - its a very odd run, I'll go as far as to say, discard it.

 

I'm taking a break from model watching for a couple of days, hopefully on return we will see a bit more consistency. My own view is for a colder trend next week rather than the atlantic crashing in.

[IDO]

The latest update from the Met via BBC for the 6-10 day period ignores the ECM op. It sends a LP system towards the UK, uncertainty re track, with disruptive winds and rain (poss snow):

http://www.bbc.co.uk/weather/features/30556460?ns_mchannel=social&ns_campaign=bbc_weather&ns_source=twitter&ns_linkname=news_central

Much in line with the mean output, backed by the ensembles with respect to the deepening low.

[johnholmes]

Comments on latest NOAA and general comments following on from that for the Christmas period

 

6-10 from far w of chart and trough ridge along with -/+ve suggestions looks about same as last issue-canadian trough is looking about the same, re position/intensity-ridge/+ve heights and the +ve heights remains around 370dm + which is certainly a significant +ve height anomaly and it coincides with the ridge-this as before causes the 500mb flow to move towards the uk with a direction well n of west, with still quite a rounded trough over the uk along with some SLIGHT extension into Europe but NOT much.

Height over far s of uk=remains a touch over 546dm

The 8-14 and it looks pretty similar to me in all aspects to the last issue; possibly the slightest extension s of the uk trough, height far s of uk=546dm/touch above much as 6-10 so the pattern looks likely to be as shown on both these over the 6-15 day time scale.

For ski fans (like myself, we could do with the extension s of the trough into the uk to bring snow in decent quantities to lower levels than many resorts have had for a week maybe longer!

For the UK, remembering these are mean charts over the period given then the probability of sharper extensions is present. Small, relatively, upper troughs are best left to the synoptic models at shorter time scales.

Perhaps we can take a look at the 2 major synoptic outputs, maybe 3 if we use the UK model?

For some obscure reason folk want to know weeks in advance what it will do on the 25^th of this month, never any other month and some do get worked up when the models cannot do this, be it 240h or 96h out but never raise a murmur on 25^th of any other month. Scientifically this is totally illogical but never mind.

Link to NOAA output

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

For details on how this and EC-GFS were summed up from this morning please see the post with links in the technical thread. It is NOT technical.

A link to see how the EC and GFS models at 00 and 12z have coped with this from 240h down to today is below.

The GFS 12z version from 240h and it has some similarities, at least not showing any flow from the SW. The 00z a little more consistency on most runs, again no SW flows shown

ECMWF 12z and 00z perhaps not quite the consistency of either GFS runs?

Anyway I will leave it to the reader to make their own mind up.

What I am trying to illustrate is that, to me if not you the reader, the anomaly charts have been more consistent than the synoptic charts in predicting this substantial build of pressure in the southern Greenland area for a number of days. Once the +ve heights began to show substantial numbers east of the Canadian trough, this partly the cause of the trough moving west, then the pattern they show for 6-14/15 days ahead looked fairly clear.

This build of heights and surface pressure below it is the cause of the lows/depressions running east not NE if you look at the Fax chart, link below

http://www.weathercharts.org/ukmomslp.htm#t0

If you look at their raw data below the Fax charts out, currently, to 25 December note how the 552dm line is pushed south with colder upper air pulling in behind it. Also the transfer south of the surface trough to cover most northern areas by Christmas Day. Still held up as it often is by the ‘lee’ low that often develops in Arctic flows over Iceland. This will not change much until/IF the upper flow turns north of west over the UK as the trough then extends into Europe. At the moment there is no sign of that happening.

Will it happen, sorry do not know. The next further out link I use is the MJO and that is currently and predicted to be in a very low orbit. This usually means that the weather patterns over the UK are likely to be much as they are for some time to come. How long? Again I do not know but the MJO change to a relatively reasonable orbit may signal a change. Again to what I have no idea. Perhaps the other links we read in the OPI or Stratosphere thread may give us more guidance there.

 

Finally how active is this incursion of colder air likely to be? That can only come from shorter time scale guidance using the synoptic models. Judging by the quite strong indication from UK Met, they are fairly convinced it is going to quite marked in one or more parameters, be it wind, rain or snow.

 

If things look to be changing I will post again over the next few days. Some look like having snow on the ground or falling over the Christmas period. Stay tuned as no doubt on here we will be treated to all manner of ups and downs before Christmas Day and after.

[snowice]

Models continue to show all sorts of scenarios - most notably ECM today - its a very odd run, I'll go as far as to say, discard it.

 

I'm taking a break from model watching for a couple of days, hopefully on return we will see a bit more consistency. My own view is for a colder trend next week rather than the atlantic crashing in.

You will hide behind the sofa but I bet you will have a peek this model business is Addictive?

[nick sussex]

It's always more nerve wracking when essentially one change can lead to a domino effect and that's essentially where we're at this evening.

 

Essentially here its what happens near the Azores between T144 and T168hrs that will dictate events after Christmas, we don't really need to be casting our eye well into FI.

 

I don't think theres much middle ground here because as the block edges east out of Canada it will force a shortwave se from Iceland this is agreed across the outputs.

 

If this phases with shortwave energy to the sw then you end up with the cold piling sw into the mid Atlantic, then it will take several days at least to get the cold in and that's if the upstream pattern is still favourable.

 

If the now to be named Satan Low to the sw ejects one of its spawn ene and this separates cleanly from said Satan Low then this gives enough time for the block to nose se and cut off any further spawnings!

 

The SOSS Spawn Of Satan Shortwave then phases with the shortwave heading se from Iceland but crucially the block is already sufficiently east to edge the pattern further east and se and crucially has cut off SL from SOSS.

 

For a less theatrical view on this see page 42 where this gets a less Hamlet type view and a more coherent post not emotionally traumatized by tonights series of events!!!.

Edited December 19, 2014 by nick sussex

[Geordiesnow]

Got to say, its not until the GFS FI output where you see a Northerly occurs and we know this run at a lower resolution past 192 hours and any potent cold shot has not come forward by much at all it seems. It also seems initially develops a west based NAO and we a mild SW'ly, not quite how the ECM sees it but too me, there is some trends which suggest the ECM should not be ignored as much as it is on here. 

 

I also like to point out, at 168 hours on both 12Z runs, they look quite similar too me.... I think the ECM model has been more consistent in my eyes in what it think will happen and I think the GFS has trended towards the ECM pre 192 hours.

[Frosty.]

I think most of us knew there had to be something fishy about the ecm op run and the mean has put things into a truer perspective which is more in line with latest met office thoughts..i.e...it's going to turn wintry and stay wintry for a good while. :-)

[Mucka]

Personally I am not too happy with ECM ensemble mean charts. They are not awful my any means and normally I would take them but they do provide some support for the Op with the shortwave to the NE being held back allowing a greater risk of it phasing with low pressure to the SW. I expect the postage stamps are a mix of that sliding SE and phasing later a la GFS or taking a more Southerly route  and so possibly phasing earlier giving a longer spell (If still short lived) of unsettled westerly based weather (though still with cold possibilities thereafter)

 

It is a combo of the shortwave to the NW being slower and the closed low/shortwave to the SW being faster/further NE  that are allowing the phasing rather than the closed low to the SW misbehaving. ECM/UKMO/GFS comparison 144h

 

 

UKMO is more in line with GFS and would likely not have the phasing too far West like ECM so ECM is still out on its own somewhat as far as cross model support goes but it does have some support within the ensembles for the general synoptic looking at the mean.

 

 

So I can't dismiss the ECM Op as easily as some (re low to SW further NE and phasing with shortwave to NW) but I still feel it is the unlikeliest solution.

This part of the drama at least may be resolved by tomorrow evening, we just need ECM to drop this Westerly based solution.

Edited December 19, 2014 by Mucka

[terrier]

I think most of us knew there had to be something fishy about the ecm op run and the mean has put things into a truer perspective which is more in line with latest met office thoughts..i.e...it's going to turn wintry and stay wintry for a good while. :-)

sorry but how can you say it going to stay wintry for a good while. Nothing is set in stone yet regarding this cold spell it's still in realms of fi. And to say it's here for a while just seems abit premature frosty. Yes I like cold and snow but I also know the models could flip towards the ECM or we could end up with those shortwaves scuppering everything. Seen cold spells disappear at t48 never mind t300

[bluearmy]

Something to look for (which seems illogical, given the way the euro heights have become stronger as the modelling has ticked down) is the analogs on CPC show low height anomolys to our south, as early as day 8. Of course analogs aren't the here and now but as someone posted earlier - 'I ain't never seen a chart like that !'

[A.J]

It's always more nerve wracking when essentially one change can lead to a domino effect and that's essentially where we're at this evening.

 

Essentially here its what happens near the Azores between T144 and T168hrs that will dictate events after Christmas, we don't really need to be casting our eye well into FI.

 

I don't think theres much middle ground here because as the block edges east out of Canada it will force a shortwave se from Iceland this is agreed across the outputs.

 

If this phases with shortwave energy to the sw then you end up with the cold piling sw into the mid Atlantic, then it will take several days at least to get the cold in and that's if the upstream pattern is still favourable.

 

If the now to be named Satan Low to the sw ejects one of its spawn ene and this separates cleanly from said Satan Low then this gives enough time for the block to nose se and cut off any further spawnings!

 

The SOSS Spawn Of Satan Shortwave then phases with the shortwave heading se from Iceland but crucially the block is already sufficiently east to edge the pattern further east and se and crucially has cut off SL from SOSS.

 

For a less theatrical view on this see page 42 where this gets a less Hamlet type view and a more coherent post not emotionally traumatized by tonights series of events!!!.

have you been on the sherry tonight Nick?  :smiliz39:

 

I get the gist of your post, but holy smokes, it's got more twists and plots and melodrama than a Guy Ritchie gangsta movie.....lol

 

As you said though, many twists and turns to come, and no doubt with the GFS P offline this weekend, they'll be some very anxious model watchers in here this weekend

[damianslaw]

Reading into the Met Office for period Christmas into new year and it suggests to me they are forecasting strong heights to the NW and the jet taking a southerly course throwing up frontal activity from the SW this engaging with colder air to the north - hence a battleground set up places to the north of the polar front jet likely to see some significant snow. The 'low pressure' from the west post Christmas likely to track on a direct course over the country become slow moving and head SE, to the north and west of it - snow likely.

[Frosty.]

I know nothing is set in stone but I've noticed any breakdown to the upcoming cold pattern has been pushed well back into the depths of FI. Throughout all this build up I have stayed positive and see no reason why a wintry outlook won't fall into place..after the total garbage we had last winter I feel we are now in a relative position of strength as we look towards Christmas and the new year.

[Cloud 10]

Well,the GFS P is AWOL for the weekend now,so its down to the good old trusty vanilla pub run

to deliver the goods.(whatever they may be)

[Eugene]

I know nothing is set in stone but I've noticed any breakdown to the upcoming cold pattern has been pushed well back into the depths of FI. Throughout all this build up I have stayed positive and see no reason why a wintry outlook won't fall into place..after the total garbage we had last winter I feel we are now in a relative position of strength as we look towards Christmas and the new year.

 

Guess you forgot to look at the reliable timeframe then :smiliz19:

[Geordiesnow]

Even already there are small but potentially significant difference in how the GFS is modelling that trigger low pressure system so how can you put faith in a northerly shot in the lower resolution of the run is beyond me. 

 

Its a messy horrible pattern unfortunately and in terms of details then we got some days to wait for that, nevermind knowing whether we will get a significant cold shot or not. 

[Stormyking]

Hmm I dont really know what to think to be honest, see the GFS normal and GFS P went through a dodgy little patch the last few days, and have decided to go back to more colder and better heights again over Greenland, where as the ECM was the one showing better signs for colder weather the last few days when the both GFS looked dodgy for a time. Now all of a sudden, they have swapped round and its now the ECM that doesn't want to come back on board with colder weather. Admittedly in my eyes the ECM does look the most strange and not as plausible as the others, but I can't discard it as easy as some others, due to the fact of the GFS norm and P had been like recent days.

 

However personally I reckon it will be more of a colder and drier theme over more Southern areas, but better risk of snow over Northern and Eastern areas just after Christmas, but we shall see, this is just my opinion from ive been seeing this last week. Lets see what the GFS 18z shows this evening.

 

Come on Pub run please be drunk!     

Edited December 19, 2014 by Stormyking

[Barry12]

It's mad Friday so I thought I'd do something mad and take a look at next week according to the GFS 12z...

 

Monday

 

 

• Mild for England and Wales
• Average for Scotland and Northern Ireland
• Mostly dry

 

Tuesday

 

 

• Mild for England and Wales
• Average for Scotalnd
• Wet for most of us

 

Wednesday

 

 

• Average temperatures for England and Wales
• Below average for Scotland
• Mostly dry

 

Christmas Day

 

 

 

• Average for England and Wales
• Below average for Scotland
• Dry for most

 

Boxing day

 

 

• Below average for the whole of the UK
• Snow for NW England and NW Scotland

 

 

So basically it will be mild until Wednesday/Christmas eve before colder air moves in, parts of NW Scotland and NW England could see some snow even to lower levels...based on the Met Office outlook I expect the post boxing day period to trend colder with snow to lower levels in the North, and I expect the ECM to be far better tomorrow.

[Met4Cast]

18z has already shifted the pattern further West.. this isn't a good sign

[Frosty.]

Guess you forgot to look at the reliable timeframe then :smiliz19:

Lol no I just glossed over the pre Xmas period because it's nothing to write home about as Michael fish used to say on tv..later next week is when things kick off so to speak..it's exciting times ahead IMO

[blizzard81]

Hmm I dont really know what to think to be honest, see the GFS normal and GFS P went through a dodgy little patch the last few days, and have decided to go back to more colder and better heights again over Greenland, where as the ECM was the one showing better signs for colder weather the last few days when the both GFS looked dodgy for a time. Now all of a sudden, they have swapped round and its now the ECM that doesn't want to come back on board with colder weather. Admittedly in my eyes the ECM does look the most strange and not as plausible as the others, but I can't discard it as easy as some others, due to the fact of the GFS norm and P had been like recent days.

 

However personally I reckon it will be more of a colder and drier theme over more Southern areas, but better risk of snow over Northern and Eastern areas just after Christmas, but we shall see, this is just my opinion from ive been seeing this last week. Lets see what the GFS 18z shows this evening.

 

Come on Pub run please be drunk!     

If you are referring to the operational runs, the ECM has not been interested in cold synoptics these last few days. It was the GFS P

that was dancing to the drumbeat of cold and forecasting quite a potent northerly for Xmas for many runs on the trot. It has well and truly been left with egg on it's face and I for one will be giving it a wide bearth when it returns from yet another hiatus on Monday.

Edited December 19, 2014 by blizzard81

[karlos1983]

18z has already shifted the pattern further West.. this isn't a good sign

Looks identical to me out to 120

[Banbury]

http://modeles.meteociel.fr/modeles/gfs/runs/2014121918/gfsnh-0-120.png?18

 

Virtually identical , not really sure how we can judge its doomed from this point onwards ????

[DAVID SNOW]

18z has already shifted the pattern further West.. this isn't a good sign

 

To and fro it shall go and where it stops no body knows.....

[Matty M]

Yes GFS looking a bit more ECMWF like, however it really is too early to judge, the EC operational was very different, I would not expect the 18z to go quite that far, will be interested in its evolution.