Model output discussion - 5th December 2016 - Into Winter we go

[Bristawl Si]

33 minutes ago, Summer Sun said:

 

Those updates that Matt posts seem to have changed everyday for the last week. I know he is just quoting from a source so not dissing him but just saying. Should that source be looked upon as reliable?

Edited December 13, 2016 by Bristle boy

[SMU]

11 minutes ago, Bristle boy said:

Those updates that Matt posts seem to have changed everyday for the last week. I know he is just quoting from a source so not dissing him but just saying. Should that source be looked upon as reliable?

Depends if you want a forecast or someone relaying the outputs...

The problem with twitter is that theres not much room for a decent long winded post so its just a short & sweet summary...

S

[booferking]

24 minutes ago, Steve Murr said:

Evening All- 

So x2 days off since the last post, however I may as well copy & paste what I wrote then on the last update- 

No change expected till post Christmas now im afraid

So with that in mind all the reference points are all the same - perhaps slightly enhanced ie...

Vortex- becoming even stronger - zonal wind heading up to a mean of about 50-52M/S

- the important context here is at the same time of 2015 the zonal wind speed was only 2-3 M/S faster so essentially in around 5-6 days time we are in the same mire as last winter...

* the only difference is that the core of the vortex is displaced just slightly NW ( relative to the UK ) V where it was last year-

* Southern Scandi heights get the boost across from the UK at the weekend with core central thickness increasing from 560 DAM to ~ 574 - which makes it a very stable feature

* The reverse flow over Iberia all the way back to Eastern Europe *MAY* get some re-inforcement late next week highlighted by the JMA-

so essentially the status quo of the 2 main players with the low heights over Iberia > Italy a sub plot in the main story line-

In terms of of the Uk the finer detail of the mid term & onto Xmas still remains illusive however with the anomalies mooching about in the same places -its all got a bit of +1 about it, a bit like watching a programme then watching it again..

I would say the 'potential' shown towards xmas in the shape of possible change in the atlantic has taken a step back in the last 24-48 in favour of more of the same ( no atlantic retrogression or amplification ) however it could re-emerge with just 12 days to the big day-

Will it be seasonal- well I think we might just scrape 'normality' in the form of faux cold from the SE but being such a fine line im inclined to think it might be faux 'faux' cold- ie not quite as cold as it could have been-

 

lastly- not mych silver lining - especially in the form of the context around Jan as at first glance it appears to be much the same- however zonal wind peak looks to be projected @ day 10 with moderation post that- & CFS continues to project a SSW in the new year - ( early Jan ) - with the usual 10 day propergation windows...

Not particularly great tonight but thats how it is....

S

Great to hear a realist review especially from a pro on here that i hold with high regard tells it how it is...

[Dennis]

it has potential last days of dec 2016 PV split watching

[damianslaw]

2 hours ago, nick sussex said:

For newbies who might be confused with some of tonights comments. Just think of it this way, PV dark purples to the north trying to sink the high, that low pressure you can see in the Med is doing its best to stop that from happening.

In these situations something has to give, eventually one wins out, you either get the PV winning out or you'll see it slowly weaken or at least edge west , in that case you'll see some trough disruption with some energy heading se and in effect giving that low pressure a top up. At this point the high after being battered and bruised picks itself up and starts to ridge north again.

For this reason whenever you see a chart in winter which has low pressure in the northern Med then this is a big help, its very difficult for milder conditions to get in with that there and it can often deliver cold to the UK.

For those that have followed the thread over recent days you'll see I've been less than enthused by the outputs however because of that low pressure in the Med I'm willing to wait and see where we go from here. The PV may win out but theres a chance it won't.

Good post, yes we have opposing forces with the UK stuck in the middle somewhat, the block to the east, against quite a strong PV to our NW, its unclear how things may pan out, but lowering heights over the med, as you say will not make it an easy ride for the atlantic to steamroller in, trough disruption could occur, or the jet is forced on a very NE path ushering in cold continental air on a light SE/E feed. Not sure what to make of it all. Interesting to see very cold uppers digging into north mid atlantic behind the fronts - so if we did see the atlantic breaking through, we could see some potent cold PM air behind, sub 522 dam air very close to western UK shores shown in some of the outputs.

If the block can hold the atlantic back early next week - when we really do see it getting up to fourth gear, then prospects longer term of it holding it bay through into christmas will be significant, but we have a number of days to go yet..

[Singularity]

I think it speaks volumes that even some seriously intense Atlantic troughs are unable to shove their way right into the UK during the ECM 12z, thanks to those Mediterranean lows that were quite recently being overlooked by the models - but only in the sense that if some upstream amplification can then be forced via tropical convection, the ridge is there to exploit the opportunity pretty much as soon as an Atlantic trough digs south.

ECM ens. remain least keen on the Pacific tropical activity we need, so little wonder that they show a cyclonic signal breaking through days 11-12. GEFS are more keen, but not as much as two days ago, hence we see less of a cyclonic signal but also not as much of a blocking signal as there once was.

Seems like the best case 'reasonably achievable' scenario for the big day is a trough digging south sometime 22nd-24th and then taking on a negative tilt whereby the Atlantic jet heads well south into Europe to lower heights S/SE of the UK and advect some chilly air our way. To get anything 'properly cold' would be a major long shot; the low dropping through Scandinavia ata around +144 would have to exhibit some westward movement while the Atlantic trough peaking around +168 would have to be a fair bit sharper (angle of isobars east flank more like S-N than SW-NE). Or maybe there's something like the 12z UKMO but that seems to be a real wildcard this evening.

So yeah. Most likely 'seasonal' is as good as we can sensibly home for on 25th. Better than a lot of years it has to be said!

[Derbyshire Snow]

First post this winter as i have seen nothing as yet to get really excited about for snow/cold lovers, and i am afraid to me it looks more of the same for a considerable time yet

Our main problem to overcome as last year seems to be  the jet stream again, even though not as strong or persistent but still enough to push troughs and depressions across the atlantic and stop any western regression of the heights that are over over Eastern Europe and  Russia, hence the very cold air stays put only making occasional teasing westward movement.

In my opinion there are two ways for very cold to hit our shores and that either  would be a breakdown  in this jet stream or significant southward movement of it to allow heights to develop over North Atlantic and join forces with extending high pressure from our East   OR  a complete breakthrough of the atlantic and through British Isles and pushing away  the Northern European high completely, leaving us with low heights over the continent and a build of a high over Greenland and north Atlantic. In both these scenarios we with luck would get our really cold snowy weather  from the north or east.

However after saying that there are still more optimistic signs than the rubbish winter of last year, and meaningful severe weather usually never starts until after Christmas, so lets enjoy Christmas and bring it on after. Even though it doesnt look promising now much can change in 2 weeks time.

Love reading all the comments on here and even after 60 years i never get tired of trying to comprehend the British weather, its never really  boring

Edited December 13, 2016 by Derbyshire Snow

[bluearmy]

12z para of no interest to coldies - again

[nick sussex]

The PV from hell desperately trying to demolish the block but its not going down without a fight. The block is better orientated this time and the colder air further west. We really want to see that colder air develop the Genoa Low but its not that far fetched to think we might see more trough disruption closer to the time. At this range do the outputs have the jet modelled correctly?

 

[Timmytour]

Oh the models I've seen are frightful
But the background signal's delightful
There's always ten days to go
Till it snows, till snows till it snows

[Kentish Snowman in Yorks]

21 minutes ago, Timmytour said:

Oh the models I've seen are frightful
But the background signal's delightful
There's always ten days to go
Till it snows, till snows till it snows

When they finally see the light

The 850s are too warm

But there's still ten days to go

Till it snows till it snows till it snows

 

Altogether now!.....

 

Sorry mods!  

Edited December 13, 2016 by Kentish Snowman

[Spah1]

4 minutes ago, Kentish Snowman said:

When they finally see the light

The 850s are to warm

But there's still ten days to go

Till it snows till it snows till it snows

 

Altogether now!.....

 

Sorry mods!  

too warm

[Guest]

All hope of snow is dying

Steve Murr has started crying

but there's still ten days to go

Till it snows till it snows till it snows

[Scandinavian High.]

There is no snow in the air yet but I  do think gfs looks ok going forward we  have lower pressure in  Southern Europe and the westerly flow hitting a brick wall to north and east of uk be patient the cold and snow will come . Well hope so.

Edited December 13, 2016 by abbie123

[Woollymummy]

(next verse:)

"My guess is it's highly likely,

It won't snow before February,

Let's just hope it'll trend negatively,

NAO, NAO, NAO"

[joggs]

7 minutes ago, abbie123 said:

There is no snow in the air yet but I  do think gfs looks ok going forward we  have lower pressure in  Southern Europe and the westerly flow hitting a brick wall to north and east of uk be patient the cold and snow will come . Well hope so.

Tbh I can just see the intense low just spinning nne, ne. We need more negative tilt further sw tbh.

Gonna take a while for cold.

Edited December 13, 2016 by joggs

[Frosty.]

Snow on Christmas day for the Scottish mountains..boom!

[Chris K]

GFS 18z operational continues the theme really of High pressure either too far East or pulsing up from the Azores and stretching back into Europe again. There is a tendency to try to bring in more unsettled weather closer from the W/NW later in the run towards Xmas.

A blocked pattern it certainly has been, but it just hasn't worked out for the UK whatsoever yet apart from our cold snap late November. I'm probably not the only one getting a bit tired now of mostly grey skies day in day out with occasional fragments of rain. I know flooding is not what anyone wants, but quite frankly I would prefer a more unsettled flow from the W/NW because at least then we often get PM air as fronts move through and more sunny skies than this. My interest in weather is tested by these "grey" blocked patterns, because I like variety of weather at the surface. (although those with more interest in actual modelling of weather may find it more intriguing to understand the factors that are causing it)

Still hoping for more interest towards the New Year, but really that is just hope right now.

Edited December 13, 2016 by Chris K

[Derbyshire Snow]

but when all hope we think has gone

tomorrows pub run goes off on one

and there is still ten days to go

till it snows till it snows till it snows

 

couldnt resist  forgive me

[feb1991blizzard]

The 18z GEFS have trended very zonal by the look of things to me although I haven't delved too deep, I have only picked out a few and looked at the mean.

Edited December 13, 2016 by feb1991blizzard

[Frosty.]

It was the only bit of interest the 18z had to offer..The Scottish ski industry will be praying for this 

[swilliam]

11 minutes ago, feb1991blizzard said:

The 18z GEFS have trended very zonal by the look of things to me although I haven't delved to deep, I have only picked out a few and looked at the mean.

Maybe in the medium term but not really in the longer term

 

There are some very nice ones but much more variability though with a big swathe of yellows at or slightly higher than our latitudes.

Problem is it keeps staying at the +300 mark so nothing definite or you could say is trend. However it does show what is possible and if the majority showed raging zonality then we could be sure that would happen so this preferable.

 

 

Edited December 13, 2016 by swilliam

[Man With Beard]

6 minutes ago, feb1991blizzard said:

The 18z GEFS have trended very zonal by the look of things to me although I haven't delved too deep, I have only picked out a few and looked at the mean.

You're spot on there. The ensembles started the day with promise for the easterly and have gradually backed off.

Well have you ever seen such a stuck pattern. The Atlantic is to strong to let the block in. The block is too strong to let the Atlantic in. It's a complete stalemate. On the 18Z, even after a period where it seems the Atlantic is getting the upper hand, back comes the block later on. Oh the frustration! Cold runs are so close, you can smell them at times but just forever out of reach. 

Net result are winds between SW and SE for the most part.

Well one side or the other has to give at one point, but we aren't in a position to judge just yet.

[mulzy]

As per normal the GEFS following the ECM eps into a more zonal outlook (the GEFS generally about a day behind in smelling the coffee). Why people put their faith in the GFS and GEFS, God only knows.

 

I'm hoping today is the nadir and that things get better from a NWP perspective going forward.  Tell will tell as ever...

[Allseasons-Si]

And the Booker prize goes to pert's 14

a good easterly flow of snow flurries

and the pv smashed to bits

second prize goes to pert's 20

 

 

Edited December 13, 2016 by Allseasons-si