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

[There's a storm a coming]

In summary today, I think we've all,agreed and admitted to ourselves that the cold spell showed a few days ago is well and truly gone, and we won't be led down that "garden path" again. However the ECM and the UKMO are now looking for the next trends while the GFS has found one and its running with it........all the way back up the garden path

lets see what tomorrow brings

tasac

[Hotspur62]

Sorry -Just realised i quoted 12z GFS on previous post.18Z GFS doesnt show quite the same pressure over Greenland!!

[Singularity]

In the 18z you can really see how the background forcing toward a retracted ridge and Euro trough remains and so inertia is toward it once smaller scale setbacks stop getting in the way. We ought to see a break in such undesirable features at some point, but how soon? I wish I could say!

Encouraging to see so much cold air on tap even when disturbances are coming predominantly from the NW.

[john mac]

One thing that can be said is that the cold air is fairly close by which should help us further down the line.

[stodge]

The first main difference between the 12z and 18z occurs here at T+192:

Here's the GFS 12Z at T+204:

The 18Z OP  models a much more intense LP moving NE out of Newfoundland. This delays the retrogression of the HP in the short term but does us a favour in the longer term as it punches much more strongly into Europe and creates a much stronger trough so it's the old story of pain now vs more pain later (or something like that).

The key is to watch the "race" between the emerging storm systems and the emerging HP cells, If there is sufficient "gap" between the storms, the HP can build a stronger mid-Atlantic ridge. If not, the storm crashes through and flattens everything.

The other area for people to follow is the PV - in my view, FI is consistently over-progressive in breaking down the PV from the Greenland area and sending it west, east or wherever,. We need to see the PV displaced or split within hi-res and modelled consistently across all models before we can get too excited.

18Z OP tonight is nice to look at and has plenty of the "P" word but that's all for now. If tonight's T+324 chart is there at T+48 - well, fire up the ramps...

[TEITS]

12 minutes ago, There's a storm a coming said:

In summary today, I think we've all,agreed and admitted to ourselves that the cold spell showed a few days ago is well and truly gone, and we won't be led down that "garden path" again. However the ECM and the UKMO are now looking for the next trends while the GFS has found one and its running with it........all the way back up the garden path

lets see what tomorrow brings

tasac

Im sure some haven't learn't the lessons.

Still I see various charts being posted i.e NAO/AO forecast, GEFS means. All of these mean sod all unless all the operational models sing from the same hymn sheet at a sensible timeframe i.e upto +144.

Personally I feel the sheer amount of available data actually does nothing more than confuse and provide straws to clutch onto. Just imagine if the only data we had access to was the ECM/GFS/UKMO operationals that only showed upto +168. Fair enough we would have less to discuss but it would prove to be less stressful.

[bluearmy]

Clear where the modelling wants to get to but remaining unconvincing about whether it actually gets there. we will just as likely be looking at another scenario where the Atlantic ridge hangs back too far and the cold plunge is to our east again. 

as an example, the 18z anomolies keep the Atlantic further east than the 12z by T228 (move towards eps) but back the low anomoly a bit further west too. 

I know which movement is likely to verify!

[Purga]

31 minutes ago, Steve Murr said:

Ha - the most unlikely chart ever goes to the 18z

You're not visiting Belfast on that day are you Steve?

[Purga]

21 minutes ago, TEITS said:

Im sure some haven't learn't the lessons.

Still I see various charts being posted i.e NAO/AO forecast, GEFS means. All of these mean sod all unless all the operational models sing from the same hymn sheet at a sensible timeframe i.e upto +144.

Personally I feel the sheer amount of available data actually does nothing more than confuse and provide straws to clutch onto. Just imagine if the only data we had access to was the ECM/GFS/UKMO operationals that only showed upto +168. Fair enough we would have less to discuss but it would prove to be less stressful.

In fact the many available charts you refer to use the same basic data as the operationals - it's just different ways of representing aspects of that same data so one may as well just look at the big 3 NWP models and be done with it!

I guess it just helps oil the forum discussions to see representations of same thing from different viewpoints.

Edited January 1, 2017 by Purga

[feb1991blizzard]

3 minutes ago, bluearmy said:

Clear where the modelling wants to get to but remaining unconvincing about whether it actually gets there. we will just as likely be looking at another scenario where the Atlantic ridge hangs back too far and the cold plunge is to our east again. 

as an example, the 18z anomolies keep the Atlantic further east than the 12z by T228 (move towards eps) but back the low anomoly a bit further west too. 

I know which movement is likely to verify!

Exactly!!!   _  A good ending to GEFS suite coming up here but the ECM eps have trended against us after a good 0z run.

[karlos1983]

ECM ens not as good as they've been lately but still main clustering is not what I would call mild.

oh and for the avoidance of doubt, even though these get posted on here twice daily, these are 2m temps not 850's. Seemed pretty obvious to me 

Edited January 2, 2017 by karlos1983

[chris55]

Don't you just love a typical last minute shortwave drama scuppering our mild set up  

 

[Badgers01]

2 minutes ago, chris55 said:

Don't you just love a typical last minute shortwave drama scuppering our mild set up  

 

trigger low incoming ?

 

[chris55]

That's perb 6 on the ens

total outlier, but yes that little low over Sweden/Denmark triggers the cold to be advected our way.

jff 

 

Edited January 2, 2017 by chris55

[Cheshire Freeze]

24 minutes ago, chris55 said:

That's perb 6 on the ens

total outlier, but yes that little low over Sweden/Denmark triggers the cold to be advected our way.

jff 

 

Now if that was other way round and was to scupper the cold, it'd be nailed on to verify. Sounds like a joke but I'm serious!

[Geordiesnow]

1 hour ago, There's a storm a coming said:

In summary today, I think we've all,agreed and admitted to ourselves that the cold spell showed a few days ago is well and truly gone, and we won't be led down that "garden path" again. However the ECM and the UKMO are now looking for the next trends while the GFS has found one and its running with it........all the way back up the garden path

lets see what tomorrow brings

tasac

Well to be fair, any easterly risk has been in FI and the models still got the idea of an easterly but unfortunately for us, its slipping into Eastern Europe instead of us, looks quite close but yet so far.

Will be some cold air for the UK but we are right on the outer edge of it and with pressure high, there will be very limited to no shower activity so cold and frosty until milder air topples in by the end of the week.

[Mucka]

Interesting 00z for cold fans incoming?

Looks like a fairly potent Northerly brewing.

Edit 1

Nice polar heights, Atlantic ridge building and trough digging deep into heart of Europe - bank!

Edit 2,

Day 10 PV has disintegrated and pressure continues to rise to our N and NE as we sit under a cold snowy trough.

Anyone fancy being suckered by again?

 

Well enjoy the fantasy while it is there because it will likely disappear by the 06z

One thing I am keeping an eye on though is those projected height rises to our NE extending into the Arctic in FI, so long as that signal builds then so should our chances of cold from NE/E increase after any Northerly.

 

Edited January 2, 2017 by Mucka

[Luke Attwood]

15 hours ago, chris55 said:

delete

That is about the last 3 gfs runs now,have shown cold for next week.let's hope its not wrong again!

 

 

[Seasonality]

Cold snowy weather to chase in FI again.

[Luke Attwood]

20 minutes ago, Seasonality said:

Cold snowy weather to chase in FI again.

But the cold is here far earlier then 360 hours, although it doesn't look very cold.

Edited January 2, 2017 by Luke Attwood

[Seasonality]

4 minutes ago, Luke Attwood said:

But the cold is here far earlier then 360 hours, although it doesn't look very cold.

Yep. North westerly by 10 Jan for UK. Nice looking charts 300 plus too which would produce the goods for many here. 

[Luke Attwood]

5 minutes ago, Seasonality said:

Yep. North westerly by 10 Jan for UK. Nice looking charts 300 plus too which would produce the goods for many here. 

Agreed.most of the UK would see temps of 4-6c next week so cold but not the very cold category.

[Jason M]

No changes this morning. Short term looks poor and the last rogue GEFS ptrb that brought early cold has dropped away this morning. Still plenty of good charts in amongst the GEFS but all out beyond day 10 as usual. Looking through the individual ptrbs I got the sense that they were overall a bit more mobile than earlier sets so maybe just a hint of a return to a normal zonal type set up mid month? Certainly not an overwhelming signal but just a suspicion. Regardless of that though the good stuff is simply not moving through the timescales so in my book the FI easterly / full on northerly remains a false signal.

Wouldn't rule out a standard fare weak northerly / nwersterly but certainly no signs of anything noteworthy IMHO. 

[knocker]

The GEFS overall upper pattern this morning shows little change yesterday evening so basically the det run this morning is the latest interpretation of the internal movement within this pattern so there shouldn't be any major surprises.

The cold front has now cleared the south so all of the UK is now in the colder air as high pressure moves in. So some cold nights on the cards this week with quite heavy ground frosts and possible some fog.

The high pressure and dry weather remains influential for all of the week including the weekend with most of the upstream energy running around to the north of the HP. The exception to this being Friday where fronts manage to push their way SE mainly effecting the north with a little rain before petering out as it moves south

So on to next week and quite an impressive attack from the trough tracking east then SE over the UK ( note the energy feed to our old friend the upper low to the south which helps facilitate the next surge of the HP in the western Atlantic which on this occasion also greatly helps  the trough disturbance in the east). On the surface this constitutes some very unsettled weather by the middle of next week, very windy, copious amounts of rain and quite deep low 976mb in the North Sea. One doesn't bet the bank on this verify given the fluidity of the evolution and thus the inter run variations

Edited January 2, 2017 by knocker

[IDO]

Good symmetry within the last few days from the GFS suite for an overall pattern change. 

The Pacific Ridge ejecting one or two blocks of HP in the Polar region which disrupts the PV flow from NE Canada to Siberia (timing circa D9). The Pacific Ridge then collapses and the PV begins to reorganise at the end of FI.

Of course how this scenario plays out is anybodies guess viz placement of any trough developing from the weak HLB'ing.

It is clear that this is likely to send colder air to mid-latitudes so the background will likely be colder than average.

The OP & Control currently build a UK trough from a chunk of lower heights broken off from the PV travels. They are both the most promising in that regard with a few cluster supporting same. The 500hPa temps confirm that there is a way to go before this bandwagon will start rolling:

  

The D10 Atlantic NH profile looks consistent^^^ But after that the GEFS scatter within the backdrop of variations in those wedges of heights in the high latitude flow.

The spread at D10 and D12:

We can see that D10 good agreement, though UK less so, more to do with timing IMO. But two days later spread increases. 

The D16 mean uppers are impressive for the UK with low spread relative to such a pattern:

We are in the Twilight Zone at the moment, awaiting the GFS to get a grip of post D10 developments.

ECM moving towards the GFS pattern of a trough replacing the Euro heights but is slower, but big differences re Polar heights, enabling the PV to be more robust . Respective D10 op charts:

So major variations, that I suspect are duplicated inter model. A period of waiting till the entropy is resolved.

Pre-D9 just average fare, though predominantly dry under the UK high, and probably feeling colder than the temps suggest.