Model Output Discussion - The Run In To Christmas

[Banbury]

Just looked at the gfs 06z run and that's a awful run for coldies. Think the ECM will be bang on the money. Yes it's been throwing out different output past t144 but we see that other models are moving towards the ECM solution. Also just read cohens update on the strat thread. And it's grim reading for a ssw. Now looking like late jan. I'm starting to wonder after all the background signals looking favourable if the mets lrf winter forecast will be spot on.

Why are people taking the Ops as gospel, look at the ENS an you will see it is very much on the mild side. So how do you come to the conclusion it will be bang on the money????

[Banbury]

Excellent analysis there John. Completely based on facts and entirely objective.

Agreed, excellent post

[Frosty.]

It's really pleasing to know we are in for a cold, bright and frosty Christmas day and Boxing day this year with widespread frost early and late, so at least it will feel Christmassy instead of the blow torch mild swly mush we had for the last few years, and there will be a few snow showers around, mainly across the northeast. It then becomes very disturbed with gales, heavy rain and even sleet and wet snow during next weekend followed by further frontal rain and colder incursions, a real seesaw outlook.

[Iceaxecrampon]

About as good as it gets - and this is a week off.

 

 

Nice Northerly Jet.

 

 

Cumbria 30% to 40% ppn for 1200ft (Latrigg at Keswick for example)

 

 

ian

 

 

 

[Banbury]

About as good as it gets - and this is a week off.

 

h500slp.png

 

Nice Northerly Jet.

 

hgt300.png

 

Cumbria 30% to 40% ppn for 1200ft (Latrigg at Keswick for example)

 

uksnowrisk.png

 

ian

If you take the GFSP this really IS as good as it gets

http://modeles.meteociel.fr/modeles/gfsp/runs/2014122006/gfsnh-0-174.png?6

[swfc]

Maybe a bit of a simplistic view from me but given the volatility of the mo over the last 72 hours ete isnt there a chance things can swing back to a much more blocked and very cold scenario over the xmas period -new year?Even 48 hours seems a lifetime atm regarding the positioning of the ridging in the atlantic with the shortwaves coming and going also.Maybe as tamara said uncertainty maybe a prelude to a major change and the models are more confused than the members on here!!!Intersting none the less be it traumatic for a few of the forum members

[bluearmy]

Maybe a bit of a simplistic view from me but given the volatility of the mo over the last 72 hours ete isnt there a chance things can swing back to a much more blocked and very cold scenario over the xmas period -new year?Even 48 hours seems a lifetime atm regarding the positioning of the ridging in the atlantic with the shortwaves coming and going also.Maybe as tamara said uncertainty maybe a prelude to a major change and the models are more confused than the members on here!!!Intersting none the less be it traumatic for a few of the forum members

Absolutely - the ecm ens hold the Atlantic anomoly for a good few days (London ens reflect this to an extent though there will be cold high pressure scenarios in there ).

It depends how amplified things become upstream to hold the Atlantic ridge with some WAA

[IDO]

Maybe a bit of a simplistic view from me but given the volatility of the mo over the last 72 hours ete isnt there a chance things can swing back to a much more blocked and very cold scenario over the xmas period -new year?Even 48 hours seems a lifetime atm regarding the positioning of the ridging in the atlantic with the shortwaves coming and going also.Maybe as tamara said uncertainty maybe a prelude to a major change and the models are more confused than the members on here!!!Intersting none the less be it traumatic for a few of the forum members

 

Up to around D6 there is good support from the ECM mean for the likely pattern:

 

 

So strong confidence for Christmas Day UK & Boxing Day HP. However at D7 the Normalised Standard deviation goes from good confidence to lots of uncertainty:

 

 

That is when the daughter LP system splits from the core Atlantic LP. As others have said this movement is key to week 2 developments. Though even if the GFS is right it still looks possible for the colder flow to develop later as ECM shows. In fact longer term it is difficult to know which solution will be best?

[Snowman.]

Up to around D6 there is good support from the ECM mean for the likely pattern:

 

get_legacy_plot-web248-20141220083926-15414-1343.gif

 

So strong confidence for Christmas Day UK & Boxing Day HP. However at D7 the Normalised Standard deviation goes from good confidence to lots of uncertainty:

 

get_legacy_plot-web249-20141220083928-28078-1320.gif

 

That is when the daughter LP system splits from the core Atlantic LP. As others have said this movement is key to week 2 developments. Though even if the GFS is right it still looks possible for the colder flow to develop later as ECM shows. In fact longer term it is difficult to know which solution will be best?

 

GFS is very flat but I think that's just the 6z run.

 

The Para keeps the amplified theme going and matches that of Tamara's and many others thoughts.

 

The ECM delays the initial shot but still keeps the ridge along with amplification.

 

 

The para and the ECM are by far better than that of the 6z GFS run.

[Thundery wintry showers]

NOAA's 8-14 day outlook looks promising if it's a fairly sustained northerly flow you're after:

http://www.cpc.ncep.noaa.gov/products/predictions/814day/814day.03.gif

 

The height anomalies on that chart point towards a mid-Atlantic high rather than a Greenland high, so if that comes off we're probably looking at some northerly blasts interspersed with milder west to north-westerlies.  The models show strong support for this scenario post-Christmas, but whether it will be snowy or not is still hard to pin down- it will depend mainly on how far north our air masses during the northerly blasts originate from, with low pressure around Iceland likely to cut off the coldest air periodically.

[blizzard81]

I think we all need a pre Xmas Saturday night special from the models tonight. This season has so far been

very frustrating and at times tiresome for the coldies. Today has been very downbeat with the big exception

of Tamara and a few others so please, please, please 12z models hear our cries :smiliz19:

[IDO]

Interestingly the ECM height bias is significant even at D5, both runs, particularly the 12z: 

 

Clearly the ECM (also GFS to blame) are misreading the signal for (strength of) heights over Greenland. That is not good for verification of an amplified pattern! But maybe a symptom of the synoptics, and worth noting for future similar patterns.

Edited December 20, 2014 by i'm dreaming of...

[Earth Wind and Snow]

just a question for some of the more knowledgeable on here - I noticed on another site that the waters in the atlantic stretching from the gulf stream towards Ireland and UK are much colder than normal - do the models factor this in or will this have any effect on our weather? would these colder waters be of help if a cold spell develops for lowland snow or would this actually be a driver?

 

I see Tamara, John Holmes and others have given excellent detailed analysis on how things may pan out, however I do not see these much colder than normal sea temperatures stretching from the gulf stream being mentioned as a factor?

 

thanks in advance

 

EWS 

[Rocheydub]

just a question for some of the more knowledgeable on here - I noticed on another site that the waters in the atlantic stretching from the gulf stream towards Ireland and UK are much colder than normal - do the models factor this in or will this have any effect on our weather? would these colder waters be of help if a cold spell develops for lowland snow or would this actually be a driver?

 

I see Tamara, John Holmes and others have given excellent detailed analysis on how things may pan out, however I do not see these much colder than normal sea temperatures stretching from the gulf stream being mentioned as a factor?

 

thanks in advance

 

EWS

Hi

Can you post a link to this please? As far as I was aware, our local sst's were at a warmer anomaly by a couple of degrees...

[Eskimo]

Is it me or is the GFS taking forever to come out. 25 minutes in and it's only up to 48h.

[blizzard81]

just a question for some of the more knowledgeable on here - I noticed on another site that the waters in the atlantic stretching from the gulf stream towards Ireland and UK are much colder than normal - do the models factor this in or will this have any effect on our weather? would these colder waters be of help if a cold spell develops for lowland snow or would this actually be a driver?

 

I see Tamara, John Holmes and others have given excellent detailed analysis on how things may pan out, however I do not see these much colder than normal sea temperatures stretching from the gulf stream being mentioned as a factor?

 

thanks in advance

 

EWS 

I know the sst's are very important and they are an integral part in the factoring of the met office seasonal outlook. All I know is

that warmer waters to the immediate east and south of Greenland aid blocking in this vicinity.

[swfc]

12 z looks to be pretty similar to the 6z so far so no upgrade or improvement as such.Cool xmas eve so far so all not a bad day for getting about.Still struggling to understand how the amplification in the atlantic has disipated so much but hey what do i know??

[Backtrack]

12Z looking worse already, quicker to introduce mild air from the SW thanks to the Azores High...

[Winter Cold]

UKMO is no good, back in SW winds by lunch time Boxing day. Poor so far:

 

 

GFS(P) agrees:

 

[terrier]

12z bringing in milder weather. Think the gfs is starting to backtrack towards the ECM solution now. So for all the stick ECM has had over last few days. It once again shows why it's the top model in the verification stats.

[10 Days Away]

......and the above 2 posts #1281 #1282 is why I have no clue as to what's going on.

 

(Not a knock on you two above but more an obs on how difficult it is to read the situation  )

Edited December 20, 2014 by TN26

[Captain Shortwave]

TO be honest the output just confuses me more. FOr example on Christmas eve, the GFS (P) brings a shallow low across the UK which results in a very mild day for England and Wales

Whilst the other two

Have cleared the cold front south already. 

That Atlantic low is causing issues still 

 

Regarding the UKMO/GFS(P) runs, note at day 6 they both have cut off the Atlantic low, the system has to clear south eastwards and usher in colder air.

Hey presto

UKMO will follow the same route. We might not get much longevity but it offers a chance of some interesting weather, firstly from rain and strong winds but maybe snow later.

Whilst differ, the GFS op turns out pretty decently, as long as the low clears south east, then unless it doesn't engage the cold polar air then we should get a northerly.

Edited December 20, 2014 by Captain shortwave

[Backtrack]

GFSP out to 150 much better

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=54&code=code&mode=0&mode3h=&runpara=1&carte=1&runpara=1

 

That model is either broken, or onto something. It's consistency is amazing. I can't see that being right though, despite it's trend, too many other models now going against it.

[shaky]

And there was me about to say to my eyes the 12z runs look better compared to the 00z runs but hey i guess am wrong!!

[Winter Cold]

......and the above 2 posts #1281 #1282 is why I have no clue as to what's going on.

 

(Not a knock on you two above but more an obs on how difficult it is to read the situation  )

 

Its very confusing situation indeed! You can see though from the charts I included in my post that we are in SW winds on the 26th.

 

My post was just regarding the Christmas period because as the run is further on now, its still bringing through a strong low and its bringing in very cold air as it clears. That has been showing quite a few times now. Could be back edge snow as it moves through on the 27th