Model output discussion - winter proper underway

[feb1991blizzard]

1 minute ago, bluearmy said:

The 18z takes the central USA plains temps to numbers which could be a record low ??.uppers of -30c into  n Kansas/Missouri !!!!

And record breaking +ve surface pressure anomalies.

[tight isobar]

8 minutes ago, bluearmy said:

The 18z takes the central USA plains temps to numbers which could be a record low ??.uppers of -30c into  n Kansas/Missouri !!!!

Some stagering cold spilling in at US.

catching the eye is the sourcing of air that we unusualy have no note of...

A very different' quite crazy set up if things continue on this track....

Some quite crazy modeling...

But all good.

Edited December 18, 2017 by tight isobar
Missed snapshot post.

[Snowy L]

We had the 2nd (and successful) attempt at Aleutian ridging to get to the North Pole starting at around t230 with the 12z. Hopefully it looks like it is starting at t210 on the 18z.

[comet]

28 minutes ago, bluearmy said:

Looking at the latest Beeb 10 pm forecast, seems they expect the trough to get to the east and a lee northerly to come down later next week. MOGREPS must be on this page - need to revisit the eps clusters ..........

That would be my interpretation of where we are headed as well. Glad I'm not alone.

[knocker]

31 minutes ago, tight isobar said:

Indeed...given current aspects..

7-into p/8 mjo would likely be the safe-cracker....

Anyway...ops are trying hard to pick the signal....

And its looking mouth-watering into the new yr!!!...

Edit: possibly.

Also

[ACCOUNT DELETED]

9 minutes ago, bluearmy said:

The 18z takes the central USA plains temps to numbers which could be a record low ??.uppers of -30c into  n Kansas/Missouri !!!!

That's not good news for us then because it seems like (during recent years anyway) that we can't have it very cold and snowy on both sides of the pond at the same time. Everytime USA had heavy snow and freezing temperatures we had storms and quite a lot of them too some years.......... so disappointing to see this 

[feb1991blizzard]

Last 2 GFS FI op runs a decent match for EPS ext mean (D12-13ish)

[feb1991blizzard]

1 minute ago, ShortWaveHell said:

Slicing the vortex in two ?

Yes although 2 points of note are - obviously the eps mean doesn't slice it in two but the high anoms in the required place suggesting a decent cluster would do so, also the 18z GFS is further East than 12z with the ridge more Russia.

[Daniel*]

8 minutes ago, Draig Goch said:

That's not good news for us then because it seems like (during recent years anyway) that we can't have it very cold and snowy on both sides of the pond at the same time. Everytime USA had heavy snow and freezing temperatures we had storms and quite a lot of them too some years.......... so disappointing to see this 

What the central planes sees, is of no relevance to here. V cold arctic air spilling out eastern seaboard is, not what we want to see this reinvigorates the jet stream and the thermal gradient causes rapid cyclogenesis, so deep lows barrel their way towards us, this is a large reason why the outlook is looking pretty unsettled. 

[feb1991blizzard]

Just now, ShortWaveHell said:

How many concecutive gfs FL runs have done this , think Iv counted the last 4 , the slicing I mean 

 

Not sure - we need the pattern further west though, I like the end of the GFS run - first time for few days of genuine hints of an Easterly in GFS FI.

[Daniel*]

The Boxing Day storm is even deeper on GFS 18z sub 945mb a powerful storm definitely appears possible on this date I’ve lost count how many times it’s been modelled by GFS.

[Paul_1978]

1 hour ago, damianslaw said:

 

 

With the forecast pattern, I suspect this thread will be quiet in the days leading up to christmas, but my hunch is this is not a long-lasting trend for the rest of the winter, lots more twists and sudden changes ahead.

I think with charts like this getting turned out it could be quite busy!

[Daniel*]

Holy smokes GFS 18z is mind blowingly cold for CONUS -35C 850hPa temps for South Dakota hopefully I’ve got my states right, seems the most extreme cold since Jan 2014? 

No surprise we’ll be seeing ‘energy’ coming our way.

[bobbydog]

well this is an idea of how we might arrive at the blocking scenario we're looking for-

and it still appears wind will feature heavily on boxing day-

so go easy on the brussels sprouts....

[MildCarlilse]

It is becoming ever more certain that a deep low will make it's presence felt around Boxing day,give or take 12 hrs either way.Looks also like being part of the pattern changer but for now,finally the mild air forecasted for Sunday is now seeping south over Scotland.

[JBMWeatherForever]

Potent northerly looking increasingly likely now for just after the Christmas period. Potentially stormy too with Blizzards for Scotland ! Not a white christmas day, but soon after could be, especially for more northern parts. 

[northwestsnow]

16 minutes ago, JBMWeatherForever said:

Potent northerly looking increasingly likely now for just after the Christmas period. Potentially stormy too with Blizzards for Scotland ! Not a white christmas day, but soon after could be, especially for more northern parts. 

But no model says this that i can see?

18Z offers a brief 12-18 hour north westerly and i'm not sure EC even shows that..

[northwestsnow]

well after viewing all the NWP i must say that week ahead forecast from D.Brett has me utterly confused!

He shows the low to our west around christmas day move into the north sea (off E Scotland) and cold northerly winds...

Something doesn't add up here.. surely he will have seen all the model data before going on air!?

[snowray]

Well its certainly trending colder after Christmas on the 18z.

Birmingham ensemble:

[A Frayed Knot]

2 hours ago, Daniel* said:

The Boxing Day storm is even deeper on GFS 18z sub 945mb a powerful storm definitely appears possible on this date I’ve lost count how many times it’s been modelled by GFS.

At least SANTA emptied his sack the day before ' God bless him x

[Captain Shortwave]

      

The UKMO/GFS and GEM this morning

A major ridge over the Pacific which seems to have been upgraded in its northward push over the past few days, the major risk during the Christmas/New Year period seems to be the possibility that the entirety of the tropospheric vortex could end up on the Atlantic side hence giving the sense of Zonality even if the polar vortex has been heavily compacted compared to its usual presence across the Arctic.

With this at day 6, I wouldn't discount anything as we approach the new year as modeling what happens to this ridge (The possiblity of a cut off Arctic high looks likely) is going to be very unpredictable. I guess the phrase cautious optimism is the right thing to use here. The UKMO seems to offer the most optimistic outcome for the UK with the ridge piecing right through the north pole whilst the other two see the ridge attacked from the west.

Edited December 19, 2017 by Captain Shortwave

[knocker]

Today

With high pressure centred to the south a generally quiet day with light winds and any early morning fog in places will clear most quite quickly, but with a weak front hanging around some areas will turn cloudy with intermittent light rain.

Later as a cold front approaches more persistent rain will push into western Scotland and track south east overnight and through Wednesday, with clearer weather behind whilst most of England and Wales will remain cloudy and quite mild with temps a little above average.

So on to this morning's gfs. During Thursday and Friday the UK remains under the influence of the high pressure centred to the SW/S thus a generally benign couple of days with most places remaining cloudy with temps around normal or a tad above. But by 12 Saturday the trop. vortex lobe has dropped south over central North America under pressure from the Alaskan ridge and the very strong jet running around it and across the Atlantic is beginning to suppress the high over the UK.and a front is orientated from Scotland to the west of Ireland.

Over the next 36 hours the high pressure stands firm to the south under pressure from the east bound energy resulting in a a fairly strong and warm (relatively) south westerly flow over most of the UK with temps maybe touching 13C. Whilst at the same time a wave develops on the slow moving front and deepens and tracks north east to be 989mb over Stornoway by 00 Monday with the front now orientated down the west coast of Ireland/

During Xmas Day it all gets very complicated with a deep and complex upper trough over the eastern Atlantic initiating explosive cyclogenesis as the aforementioned low 'bombs' as it continues to track north east whilst another deep depression approaches from the west. All of this would portend a very wet and windy Xmas Day

By late Tuesday the next deep depression duly arrives to the NW bringing more rain and gales but this is best left here as I'm sure the detail of all of this will be subject to much revision although a very unsettled period is certainly the percentage play at the moment.

 

Edited December 19, 2017 by knocker

[chris55]

ECM quite different from GFS at 168.

GFS overlooking the depth of the troughs perhaps.

ECM

GFS

 

[Ali1977]

Definitely some attempts on various models to get the Alaskan ridge up into the Arctic and create some kind of Arctic high. In some scenarios I'm sure this would end up great for the UK but at the minute there's just too much PV around NE Canada help the block pop out of the Arctic into the Atlantic or around Southern Greenland. As long as we have some kind of Arctic high though, there's a chance that this may be to our advantage in the longer term.  To me, any meaningful cold this side of New Year is off the cards, beyond that is obviously way to early to guess but an unsettled/blustery start to Jan is what the METO are plugging for on their long range - standard Winter stuff for now!!

[knocker]

Predictable the ecm is not copying the complex, apocalyptic, scenario of the gfs next weekend and after although it is also very unsettled and very windy at times

It does have a trailing front impacting western Scotland by 12 Saturday and then tracks a shallow frontal wave ENE overt the next 24 hours to impact the same area by 12 Sunday whilst the rest of the UK is under a brisk, quite moist westerly airstream.

By midday on Xmas Day the front and another developing wave are over Ireland with the surface wind backing south west. By midnight the wave and front with associated rain have pushed east over the UK

By 12 Tuesday the wave has continued to deepen as it tracks north east and another deep depression is approaches the south west. All of this under the auspices of a complex upper low that covers the eastern Atlantic and the UK