Model Output Discussion - The Start Of Winter

[Eugene]

Increasing trend today for -NAO to set up, albeit we will still not benefit if it's west based. This has been a repeating scenario in the GEFS.

I really hate these set ups! Lots of water to pass under the bridge before we get to this though....

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=384&mode=0

 

 

Yes Jason that trend on many GFS OP runs lately is a west based -NAO setup.

 

I'm like johnholmes very cautious over anything cold more than brief PM NW'lys until much more evidence at a much more reliable timeframe.

[A.J]

 

..........I'm dreaming of a .........

green christmas??

 

[Man With Beard]

A little model related aside - whether it happens as shown or not, is anyone else impressed with the GFS in FI at the moment? A few years ago, you could get 4 massively different outcomes a day at T300+. But since the 18Z last night, it has shown an extremely similar pattern in this time period, if you look at most of the op, parallel and control runs - and the west-based -NAO is not the most common of weather patterns, so isn't just defaulting to something obvious. This is good for us - a clear trend to follow, not pulling balls out of a hat as it once was!

[Mucka]

GFS ensembles churning out and big differences even at day 6 among members.

 

 

Looks like Shannon entropy may be getting a mention again next week? 

Edited December 14, 2014 by Mucka

[Polar Maritime]

The GFSP continues to show some sorts of pattern change towards the New year, With the PV becoming very disturbed and erratic. Giving the possibility of some very cold weather if everything falls into place, A very interesting period coming up for Model watching as they play around with the mixed signals, Expect lots of different but 'interesting' evolutions over the coming days.

 

  

Edited December 14, 2014 by Polar Maritime

[MR EXTREMES]

I'd be very cautious of a Arctic blast around Christmas the likelihood of it missing the uk and involving Scandinavia is a strong possibility.

If it's still there by mid or next weekend then perhaps !.

Interesting part is the modelling of Greenland heights although looks likely in some form it still has a lot of work to do.

It certainly looks likely would like to see the ecm onboard but this model seems a bit scatty since November although in the world of weather and models anything could happen be nice to see a full house.

The signals or signs are still there I'd rather wait for a few days to see the consistency of every model.

But looks as though john h anomaly charts might start showing some signs soon.

I'd punt for 50/50 chances now of the winter grinch packing it's bags for Mexico.

El Niño winter it was in 09/10 not sure what enso state was in the winter of 63 interesting stuff popping out in the models ukmo looks pretty in line with the gfs as well.

[Banbury]

green christmas??

 

viewimage (7).png

Always more likely to get a white Easter than Xmas, so Green would be no surprise to anyone

[phil nw.]

I don't,think we should be concerned re a west based -nao yet.

The pattern is not primed for sustained Artic blocking in the next 2 weeks, although we still should see enough cold air coming this way from the modeled amplification in the jet.

GFSp showing that a Scandi.trough and transient Atlantic ridging will do a decent job of some Arctic incursions in week 2.

Edited December 14, 2014 by phil nw.

[Harsh Climate]

For me the signals are certainly there for colder weather to move into eastern europe/ western russia late this year and for the PV to split with height rises towards greenland.  This colder weather could then reach our shores..The key thing is though will any block be far enough east (not a west based NAO) and can we get lows from the atlantic cutting far enough south to allow a proper continental feed (Im assuming that's what everyone wants in terms of getting a good sustained cold spell ; ) .)

 

Look at the GFS 12z @+384h for example:

 

 

If we were to get to this stage, we need that low/troughing (just to the south west of the UK) to just cut a little further south east into central europe then the beast from the east would be unleashed.Another thing to look out for would be for height rises to develop over scandinavia, which I'm shure would then link up with high pressure over greenland. With what looks to be a weakening of the jet stream and PV, this second route would also be a good possibility.

 

So all in all I don't think we can ask for much more at this stage, let's get a chart like the one posted coming into fruition then I think the only foreseable outlook is COLD/BLOCKED with an increasing risk of SNOW

Edited December 14, 2014 by Harsh Climate

[bluearmy]

I think that boat sailed a while back. The push from the US of heights comes in two packets and they slide between the jet to the south and lower heights to the north:

 

You are assuming that the gfs in week 2 is correct. I suspect it will be too fast with its current solution and come verification, a more amplified solution upstream will occur. that would allow a smoother transition of the Azores high to s Greenland region. we shall see.

[bobbydog]

You are assuming that the gfs in week 2 is correct. I suspect it will be too fast with its current solution and come verification, a more amplified solution upstream will occur. that would allow a smoother transition of the Azores high to s Greenland region. we shall see.

correct me if i'm wrong but doesn't the GFS usually have a tendency to flatten greenland ridges in FI?

[bluearmy]

correct me if i'm wrong but doesn't the GFS usually have a tendency to flatten greenland ridges in FI?

It has a tendency to flatten in general because it has a tendency to be quick (which doesn't allow amplification to establish). the week 2 gefs all over the place. the only low spread being the west Iberian ridge. not great but the fact that there is a general lack of agreement between many members tells me that perhaps the suite needs to be allowed to settle ??? As ever, removing high heights in the wrong places for the uk to receive cold will be the problem.

I note that Exeter now less vague on a potential cold period come January being anti cyclonic in nature.

[SMU]

evening all -

Its a busy time for me but I expect to be enjoying posting again soon - to many xmas meals!!!!

Tonight sees the ECM not only coming into the range of the key festive period but also the outskirts of our much anticipated pattern change-

We should start to see the potential high pressure zones starting to develop - namely the atlantic ridge & -EPO ridge

Fingers crossed ( im especially keen for this transition as its a key part of the winter forecast )

Regards

S

[IDO]

You are assuming that the gfs in week 2 is correct. I suspect it will be too fast with its current solution and come verification, a more amplified solution upstream will occur. that would allow a smoother transition of the Azores high to s Greenland region. we shall see.

 

 

At the moment the GEFS suggest it is more likely that it will be less amplified, than more, but as the hi-res runs are pointing the way of a transient Greenland ridge around week 4 of December I was working on them. The more amplified pattern is likely in week 1 of January as the Alaskan Ridge drives the pattern, assuming the trend continues, IMO. 

[bobbydog]

It has a tendency to flatten in general because it has a tendency to be quick (which doesn't allow amplification to establish). the week 2 gefs all over the place. the only low spread being the west Iberian ridge. not great but the fact that there is a general lack of agreement between many members tells me that perhaps the suite needs to be allowed to settle ??? As ever, removing high heights in the wrong places for the uk to receive cold will be the problem.

I note that Exeter now less vague on a potential cold period come January being anti cyclonic in nature.

in which case, the fact that it is modelling a greenland ridge with some consistency and not squashing it at the earliest opportunity, must mean it is picking up a strong signal it cant ignore. as you say (if it continues to appear on the GFS) it should become more amplified as we move nearer to the reliable timeframe

[lorenzo]

Couple of posts edited there due to a misunderstanding. Back to the ECM 12z...

[Snowman.]

in which case, the fact that it is modelling a greenland ridge with some consistency and not squashing it at the earliest opportunity, must mean it is picking up a strong signal it cant ignore. as you say (if it continues to appear on the GFS) it should become more amplified as we move nearer to the reliable timeframe

 

How the recent coldshot was forecast I believe?

 

Forecast

 

 

What happened.

 

 

Obviously can't go for all times but as ever with amplification of an atlantic ridge we can never put too much faith in that far out. And it shows how the GFS likes to push energy through we usually see the best examples during a cold spell where it over plays the atlantic and underplays the heights.

Edited December 14, 2014 by SN0WM4N

[stewfox]

How the recent coldshot was forecast I believe?

 

Forecast

 

 

What happened.

 

 

Obviously can't go for all times but as ever with amplification of an atlantic ridge we can never put too much faith in that far out. And it shows how the GFS likes to push energy through we usually see the best examples during a cold spell where it over plays the atlantic and underplays the heights.

 

One is for the forecast for 11th (done 3rd) the other actual what happened on 12th ? You would need to compare the 12th

[Snowman.]

One is for the forecast for 11th (done 3rd) the other actual what happened on 12th ? You would need to compare the 12th

 

Look the east.

 

The trough is already spilling over the high.

 

For your sake here is the chart to the closest time frame. If anything it proves the statement even more.

 

 

ECM wasn't close but it didn't send in the azores high and everything ride over the top.

 

Edited December 14, 2014 by SN0WM4N

[Eugene]

Look the east.

 

The trough is already spilling over the high.

 

For your sake here is the chart to the closest time frame. If anything it proves the statement even more.

 

 

 

Thanks, gives me some hope for December 22nd/23rd with very similar charts to the one above.

[Snowman.]

ECM is a horror show.

 

 

The GFSses 

 

 

Differences as early as 144 with the way hough the US trough is handled and the atlanitc energy

Edited December 14, 2014 by SN0WM4N

[karyo]

ECM is a horror show.

 

 

The GFSses 

 

Agreed! It really brings memories of the terrible winters of the early 2000's with that inflates Azores high moving into central and southern Europe.

[Buxton Codge]

12z ECM is not the best to be honest with high pressure just to close to the UK. Hopefully an outlier

 

http://www.wetterzentrale.de/pics/Recm2402.gif

[blizzard81]

Agreed! It really brings memories of the terrible winters of the early 2000's with that inflates Azores high moving into central and southern Europe.

I must admit my optimism has waned as the day has progressed. The over riding trend as the day has gone on is for that persistent high over Iberia to grow in strength. I remember many a winter when all the dream synoptics are in place only for everything to be scuppered by the beast from the south.

[karyo]

I must admit my optimism has waned as the day has progressed. The over riding trend as the day has gone on is for that persistent high over Iberia to grow in strength. I remember many a winter when all the dream synoptics are in place only for everything to be scuppered by the beast from the south.

Sadly that's the trend that we have in front of us for the reliable timeframe. I was focusing on next weekend in case a little more amplification could give us a better northwesterly shot but that's gone downhill too.