Model Output Discussion - cold spell to end Autumn

[N/A]

18 minutes ago, Draig Goch said:

Much colder 850mb temperature range in the GFS 6z, here in Porthcawl (near Swansea) South Wales with a max of 8C to a minimum of -10C and the snow risk appearing again (albeit <20%) but unfortunately this isn't expected to happen until a week's time.

Yes, this is a pattern repeated across the coast of South Wales as the GFS 6z shows for Pembroke and also Swansea  

Shall we start getting really excited yet, or do you think we'll have another kick in the teeth by the time next week comes?  

[weirpig]

In reply to Blues  post  Were should we in peoples opinion post ensembles from?.  I post Birmingham a  because its near here  and B  because its the centre of the universe.  i mean England     shall we all have one specific area were we post them from?.

Edited December 1, 2017 by weirpig

[ACCOUNT DELETED]

8 minutes ago, nick sussex said:

Just caught up with the GFS 06hrs run which upgrades the cold potential by keeping the PV further to the nw which is in line with what you'd expect from a neg AO and positive PNA pattern.

I think whats particularly interesting is the high developing to the ne which will act as a break on where low pressure can track from upstream.

High pressure there will force the jet to divert more se, if you're a coldie then this could help keep the UK on the cold side , then you look to the nw the upstream PV will reinvigorate the jet with a large temp difference as that cold hits the Atlantic.

Now we often think of mobility as a west east flow with not much on offer but in this instance the jet will track further south than normal and be diverted se close to the UK.

In these situations if you keep the cold low pressure can deliver snow on the east/ne flank of that.

I've done a crayon job to show what to keep an eye on in future runs. The area to keep an eye on is that circled red, as long as you maintain decent heights there this will keep your snow options open, you can also see the displaced Azores high as long as that remains displaced and you keep lowish heights over central Europe you're in the game.

 

In terms of what type of low might drop se, preferably you want a weakish feature,  as that's more likely to slide se favourably and not remove any embedded cold ahead of it.

It might be if we get lucky that high pressure to the ne will develop further.

Before we get too excited though we need to get over the initial hurdle of clearing a low se of the UK with ridge building in from the nw. That's within the T168hrs timeframe.

 

I'm not being funny or anything but you say a "displaced Azores high" but aren't those islands under that high the Azores? I'm confused as I thought that was an actual Azores high that's showing? 

[deeptread]

35 minutes ago, Frosty. said:

Amazing 6z full of wintry reloads and the jet digging well south..sidney looks worried!

Reminiscing?

Talking of burying nuts...I was remembering a similar quite innocuous synopsis 36 years ago today (1st December 1981)...startlingly similar charts!

1/12/2017

1/12/1981

7/12/1981

9/12/1981

[bluearmy]

14 minutes ago, weirpig said:

In reply to Blues  post  Were should we in peoples opinion post ensembles from?.  I post Birmingham a  because its near here  and B  because its the centre of the universe.  i mean England     shall we all have one specific area were we post them from?.

I think brum is a good call but not for the second reason you state .......

a few Scandinavian blocks now showing on the week 2 gefs 

[Ali1977]

So a little blip in cold possibilities and now we are back on the hunt, it's great model watching. The tweet from Ian F makes for good reading quoted earlier, let's hope we start seeing some SSW too and get an epic January 

[Glacier Point]

a little premature with those Scandinavian blocks Nick given the likely influence of the mid Atlantic ridge ? Deeper into December and January, hmm, different story.

[Methuselah]

28 minutes ago, weirpig said:

In reply to Blues  post  Were should we in peoples opinion post ensembles from?.  I post Birmingham a  because its near here  and B  because its the centre of the universe.  i mean England     shall we all have one specific area were we post them from?.

I say post them from wherever you want, WP...it's surely down to us should we not bother to read the legend?

Edited December 1, 2017 by Ed Stone
Oops!

[feb1991blizzard]

6 minutes ago, Ali1977 said:

So a little blip in cold possibilities and now we are back on the hunt, it's great model watching. The tweet from Ian F makes for good reading quoted earlier, let's hope we start seeing some SSW too and get an epic January 

I cant see that for a long while, the strat charts are just about as dyer as you can get.

[karlos1983]

14 minutes ago, Glacier Point said:

a little premature with those Scandinavian blocks Nick given the likely influence of the mid Atlantic ridge ? Deeper into December and January, hmm, different story.

 

[Devonshire]

11 minutes ago, feb1991blizzard said:

I cant see that for a long while, the strat charts are just about as dyer as you can get.

I disagree - these gentlemen are far more dyer than ANY strat charts you will ever see:

[bluearmy]

13 minutes ago, feb1991blizzard said:

I cant see that for a long while, the strat charts are just about as dyer as you can get.

they are ?

 

19 minutes ago, Glacier Point said:

a little premature with those Scandinavian blocks Nick given the likely influence of the mid Atlantic ridge ? Deeper into December and January, hmm, different story.

you seem pretty convinced on this one stewart. I noted the latest eps generally flattened the ridging again and with the jet continuing to feed se into the upper euro mean trough a height rise to our ne cant be discounted by mid month ???

[Frosty.]

It looks like following a more benign and milder spell from this weekend to around next midweek, it is then expected to become much more unsettled with low pressure becoming dominant bringing wet and windy spells interspersed with cold, brighter and showery conditions with wintry showers and night frosts. It seems likely that snow will feature at times, especially on hills and further north so we should all see at least some cold, wintry weather and just generally short-lived milder interludes with the jet digging further south at times..always a chance with this set-up that a more potent wintry spell could pop up too.

[A.J]

48 minutes ago, weirpig said:

In reply to Blues  post  Were should we in peoples opinion post ensembles from?.  I post Birmingham a  because its near here  and B  because its the centre of the universe.  i mean England     shall we all have one specific area were we post them from?.

I wouldn't use the ensembles in Birmingham.....You'd come back 5 mins later to find some brummy has pinched them...lol

some concise updates from the two Nicks, & GP this morning giving glimmers of hope that after a couple of less cold days this weekend the omens look promising for another blast of cold and potenitally snowy weather for a good swathe of the UK...I'll drink to that 

[feb1991blizzard]

1 minute ago, bluearmy said:

they are ?

 

 

Well the height at which an SSW is measured the vortex is slap bang in the middle of the pole, (I stated a while age that this would happen in Dec) with no warming right out to D16, there is a slight stretching of the vortex at 50hps but temps look to me that this wont lead to anything and thus we will be looking up top for a warming, not sure if the MJO / mountain torque charts are any good or forecasted to do anything in next month or so?

Another miserable GFS failure wrt to the strat.

[bluearmy]

3 minutes ago, feb1991blizzard said:

Well the height at which an SSW is measured the vortex is slap bang in the middle of the pole, (I stated a while age that this would happen in Dec) with no warming right out to D16, there is a slight stretching of the vortex at 50hps but temps look to me that this wont lead to anything and thus we will be looking up top for a warming, not sure if the MJO / mountain torque charts are any good or forecasted to do anything in next month or so?

Another miserable GFS failure wrt to the strat.

If gfs is a fail up in the strat then look at ecm instead

 

[feb1991blizzard]

2 minutes ago, bluearmy said:

If gfs is a fail up in the strat then look at ecm instead

 

but that will soon reform and propagate downwards rendering Christmas zonal surely? don't you think.

[carinthian]

This latest chart from GEFS has put our resort of significant snow alert for weekend 9/10 th December. Further discussion with portal service providers talk of a increased chance of Scandinavian block to form by possible as early as Mid month with Western Europe in the firing line of a battle zone. Asked for further clarification ( sign of strengthening cold block to the NE ). All sounds good to me if goes to plan.  

 

[bluearmy]

3 minutes ago, feb1991blizzard said:

but that will soon reform and propagate downwards rendering Christmas zonal surely? don't you think.

not sure of anything at the moment! so much wave activity from the NH amplified pattern to head up into the strat that I don't really buy a sudden strengthening of the vortex with a quickish downwelling into the trop. 

one thing that seems to have been missed in fergies tweet this morning was his mention of neg NAO second half dec.  for us that matters !!

[Geordiesnow]

The potential for a rather deep low has upgraded in my eyes although more runs are definately needed though. For snow lovers, ideally a much shallower system is needed as there be much less mixing of the air  masses. One to watch either way but it would be nice to get either strong winds or heavy snow after this tedious milder spell that will soon be here.

 

 

[feb1991blizzard]

2 minutes ago, bluearmy said:

not sure of anything at the moment! so much wave activity from the NH amplified pattern to head up into the strat that I don't really buy a sudden strengthening of the vortex with a quickish downwelling into the trop. 

one thing that seems to have been missed in fergies tweet this morning was his mention of neg NAO second half dec.  for us that matters !!

Sorry I never seen his tweet - but the thing I don't get is if we are getting tweets like that, why are the met still saying mild and wet for rest of winter after December, if we are still at this vortexual standpoint in late Dec then I can only see a well below average winter overall and the moderate nina analogues just don't allow for that, it would be a history maker.

[Frosty.]

15 minutes ago, Geordiesnow said:

after this tedious milder spell that will soon be here.

 

 

I agree it will be extremely tedious but hopefully fairly short-lived with action packed and at times wintry weather from later next week onwards. something to look forward to during the mild benign tedium!

[damianslaw]

Overall pattern remains the same, despite the upcoming milder more settled spell, the main force is the position and strength of heights over the North Pole and the weakened disturbed position of the PV, no change in there structure expected for the foreseeable, hence we will continue to see a very amplified atlantic flow, with a deep longwave trough digging down through east USA/east Canada, with shortwave energy spawning off it getting carried along by a split Jetstream and hence by later next week, another bout of cold polar maritime air invading the UK from the NW. Any trough/frontal features aligned NW-SE, and crucially dropping down into central Europe - this is key as it puts a brake on heights ridging from the azores into central/southern europe to any great extent; thus the azores high will remain displaced.

All the while there are signs that heights may rise to our NE aided by the lowering of heights over central Europe, propped up by the strong arctic heights and ever present Siberian heights.

An evolution ripe for a sustained bout of polar/arctic maritime airstreams, slider low and frontal feature territory, anyone on the north/east side of these features would be highly at risk from snow.

GFS this morning is showing such a pattern, UKMO not far off delivering a path towards this set up.

The key to a return to wintry conditions like this week, will depend on the strength and depth of shortwave activity from the parent trough over eastern USA seaboard, and more importantly, how much warm air advection this feature may bring up the western side of Greenland, a sharper deeper trough would be far more conducive to locking in a colder outlook here.

An interesting synoptical evolution - different to the usual zonal westerly fest we are far more often likely to see in early-mid December.

[karyo]

26 minutes ago, feb1991blizzard said:

Sorry I never seen his tweet - but the thing I don't get is if we are getting tweets like that, why are the met still saying mild and wet for rest of winter after December, if we are still at this vortexual standpoint in late Dec then I can only see a well below average winter overall and the moderate nina analogues just don't allow for that, it would be a history maker.

The latest plume of model enso conditions has la nina peaking at -0.8 which is weak la nina.

CFS has a valua of -1 but it has been more enthusiastic with its predictions throughout.

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

[karlos1983]

4 minutes ago, karyo said:

The latest plume of model enso conditions has la nina peaking at -0.8 which is weak la nina.

CFS has a valua of -1 but it has been more enthusiastic with its predictions throughout.

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

So primed for influence of the MJO then if it moves into a favourable phase..?

Edited December 1, 2017 by karlos1983