Model output discussion - into Christmas

[bluearmy]

16 minutes ago, Catacol said:

Which perhaps is a lead in to a debate on mean v cluster. I have come to think that means are somewhat misleading in that they don’t pay anything like enough attention to lower atmospheric flows. The cluster charts provide a better window into probability and also a slightly more useful way of trying to predict surface conditions, though as Knocker has said today they are a long way from being the key tap hat unlocks that door.

Anyway I agree - winter nirvana is not showing yet on NWP and it may fade before establishing a resilient block in the right area but there is enough evidence showing an upcoming change to tweak interest.

Clusters are an easier way of viewing spreads .... we don’t see ext eps spreads so the Icelandic clusters are valuable 

 I cant see much logic in viewing one without the other - and the Icelandic clusters are, by their nature, delivered with a chunk of salt 

[Jordan S]

Afternoon.

Just going to focus some more on the very wet conditions expected especially for South Wales and southern parts of England through tonight until the middle of Friday with some drier interludes at times but prodominantly wet. 

A quick look at the very strong perhaps damaging gusts of wind possible this evening for especially Western parts of Ireland northern Ireland courtesy of a vigorous low developing to the west of the main frontal system bringing gusts possibly as high as 70-80mph for the far west of Ireland, northern Ireland and more generally 50-60mph but perhaps over 80mph along the Northwest coast of Ireland later today as this storm moves away to the north for the Irish sea gusts of 60mph or so is possible later with 40-50mph more generally for Western regions but its the rain that is the likely trouble maker for the uk for Ireland its the wind. 

Arpege.. 

Here's the Gfs on three main bouts of heavy rain that will push into southern areas throughout the period.. 

Tonight.. 

Tomorrow afternoon.. 

Friday morning.. 

These interspersed with some drier spells but a lot of light-moderate rainfall persisting for England and Wales especially for the far south. 

Now here's the Arpege.. 

6pm..

Midnight tonight.. 

4am..

8am..

1pm..

3pm..

5pm..

1pm..

3am Friday.. 

8am..

Some higher ground exposed to the southerly wind could see as much as 80-100mm south Wales dartmoor look favoured for that elsewhere widely 30-60mm likely for England and Wales locally a little more for the far south of England this is altogether from the rain tonight and into mid Friday so some flooding likely in a few places these rainfall amounts are significant without the saturated ground its only going to worsen any problems.. 

Edited December 18, 2019 by jordan smith

[E17boy]

Afternoon all

The mood in here seems to have gone a bit downbeat. The weather  Will do what he has to. No matter how frustrated we get it will never change for us, all we can do is sit back patently and just wait and see how the next few days of modelling unfolds we have unfortunately no other choice.

This is the last one from me today, in my heart I think back to 9 years ago on this date it was a Saturday and a good part of the south including Lindon got hammered with snow. If only that memory lane could be reality again December 2010 will never be forgotton.

With that wish you all a great afternoon and let's keep heads up

all the best regards

[Methuselah]

24 minutes ago, bluearmy said:

Clusters are an easier way of viewing spreads .... we don’t see ext eps spreads so the Icelandic clusters are valuable 

 I cant see much logic in viewing one without the other - and the Icelandic clusters are, by their nature, delivered with a chunk of salt 

Hi BA.

I think I'd prefer it if clusters were presented as a Venn diagram as (to my ancient eyes, anyway!) when shown separately, they seem to minimise the presence of any overlap...? The mean, on the other hand, appears to imply overlap where none might exist...?

I think it must be an 'age thing' though, as you youngsters seem to cope okay!

Edited December 18, 2019 by Ed Stone

[Ali1977]

Weak Scandy high showing here on Xmas eve and jet angled NW-SE!!

 

but not on the GFS Op ,  heights nearer Svalbard and jet through mid Europe.

Edited December 18, 2019 by Ali1977

[Dennis]

Jetstream far south at Xmas week

[MR EXTREMES]

gem and jma have some pretty impressive cold pool to our east in lala land.

all subject to change.

but have feeling late december january could provide something wintry for eastern southeastern uk.

gfs throwing just about everything including the tiniest hurricane sweeping across the south of the uk.

as dennis has suggested jet stream even further south on the chart shown.

[Kirkcaldy Weather]

Just as I was beginning to think that people in here were starting to have a glass half full approach yesterday / last night and suddenly one less cold run and its back to square one with the negativity.  

Some points I will throw out there.

As I have mentioned before how many times over the years have the models handled higher pressure / blocking higher pressure (during winter) well especially out in FI? - Very rarely (one occasion that springs to mind was the GFS performance before the 2010 cold spell which given the time frame was good going but very much an exception since then)

Just out of interest given we are now 7 days from Christmas lets see how close the models are from 7 days out ( I will revisit with the actual chart for comparison after Christmas) 

GFS  CPTEC  NCMRWF  FIM  

 NASA/GEOS5  NAVGEM  GEM  ICON/DWD    

JMA  Many differences between them but key areas to me look to be Atlantic / UK and possibly most interesting the differences / struggles with the higher pressure toward Russia / Siberia.

As I said yesterday the key thing will be trying to pinpoint the timeframe for the possible higher pressure development, some firming up that it will be after Christmas possibly some time around 28th December?     

Lets see what this afternoons/ evening runs show but still very much an interesting outlook from my POV 

[Dennis]

Latest AO setup- this should show some on the chats 

[Mike Poole]

Well ICON 12z was a bit slow to the party initially in the run, but right at the end has ramped up the WAA towards the Greenland area at T180:

Ridge building...but that's the end of the run.  Good start to the afternoon set...

Edited December 18, 2019 by Mike Poole

[Dorsetbred]

It's great to see a DEGREE of confidence in the downstream weather, and the possible change to the current conditions. The current models are aligning in some way, but you can rest assured that according to a greater knowledge already has previously predicted.

1st Week January Mild and wet (Inline with models as cooler air arrives)

2nd & 3rd Week Cold and considerable snowfall

4th Week Mild & wet

The models are hinting at the above. The greater knowledge,  what is it ? "Old Moore's Alamanac"!

So lets see how we go people, model versus the greater knowledge...

[Mike Poole]

11 minutes ago, Dorsetbred said:

It's great to see a DEGREE of confidence in the downstream weather, and the possible change to the current conditions. The current models are aligning in some way, but you can rest assured that according to a greater knowledge already has previously predicted.

1st Week January Mild and wet (Inline with models as cooler air arrives)

2nd & 3rd Week Cold and considerable snowfall

4th Week Mild & wet

The models are hinting at the above. The greater knowledge,  what is it ? "Old Moore's Alamanac"!

So lets see how we go people, model versus the greater knowledge...

Well that's cleared that up!  What is your point exactly?

Anyway, GFS and UKMO early doors T96:

UKMO looking slightly more amplified of the two, not a surprise I guess, let's see where it goes...

Edited December 18, 2019 by Mike Poole

[Mucka]

GFS

Needs more shortwaves. 

Edited December 18, 2019 by Mucka

[Mike Poole]

Just a quick comparison of UKMO, ICON and GFS at T144:

UKMO has the greatest amplification upstream, ICON the most downstream, and GFS is rather unclear! I think a trend towards amplification is there but the models are handling it differently...and in UK neck of the woods could make all the difference....plenty to watch over the next few days, I think.

Edited December 18, 2019 by Mike Poole

[Mucka]

1 minute ago, Mike Poole said:

Just a quick comparison of UKMO, ICON and GFS at T144:

UKMO has the greatest amplification upstream, ICON the most downstream, and GFS is rather unclear! I think a trend towards amplification is there but the models are handling it differently...and in UK neck of the woods could make all the difference....plenty to watch over the next few days, I think.

 

I think the biggest take from that is that 3 models have quite different ideas by 120 on how things pan out which means we have little chance of forecasting beyond that, especially out to the time where any blocking could take hold.

I don't see anything wrong with people speculating which may be right or what the outcome may be but I think we are back to our old favourite Shannon entropy and all the ambiguity that comes with it.

[Ali1977]

6 minutes ago, Mike Poole said:

Just a quick comparison of UKMO, ICON and GFS at T144:

UKMO has the greatest amplification upstream, ICON the most downstream, and GFS is rather unclear! I think a trend towards amplification is there but the models are handling it differently...and in UK neck of the woods could make all the difference....plenty to watch over the next few days, I think.

This high at T204 looks nice though.

[frosty ground]

1 minute ago, Ali1977 said:

This high at T204 looks nice though.

Just a  shame the Jet is pointing everything in the wrong direction.


Had we managed to get some cold air in before this southerly tracking jet we could be looking at a very different picture 

[Mucka]

3 minutes ago, frosty ground said:

Just a  shame the Jet is pointing everything in the wrong direction.


Had we managed to get some cold air in before this southerly tracking jet we could be looking at a very different picture 

That's savage. Jet blasting through Southern Europe and we still can't get cold! 

[weatherguy]

There's no need to get too hung up on run-run variances when the interesting stuff isn't anywhere near the reliable - I understand it and definitely partake when for instance the trigger for an approaching cold spell is within 144h, but it's unnecessary in our current position!

The "less cold" 6z GFS in my eyes continued the promising theme of an FI assault on the PV:

That there, though in extreme FI, shows an astonishing three-pronged shredding of the PV.  In isolation, meaningless, but given the trend I would suggest that the models are certainly picking up on some sort of signal.  Don't look at the exact positioning of such highs or associated uppers hitting the UK; the trend is what is important and, if we get this PV shredding into a more reliable timeframe, then we can start looking into the specifics.  

All eyes on the 12z coming out now, we shall see if this trend continues...

And I'm left with egg on my face it seems  We'll see in due course whether or not this is an outlier however. 

Edited December 18, 2019 by weatherguy

[Selliso]

I'm looking forward to the next "Dec 2010", and the next 24" snow drifts like Feb 2018 too, but have to remain realistic that they are very rare beasts indeed. 

It's blind confidence time. A bit of scatter at t120, giving "low-ish confidence" is, to me, still a reason to believe!

Hope I'm not the only one that thinks these highs and lows are all part of the gig! UK weather can produce a surprise or two despite unfavourable modelling. 

Yes, the trends haven't been good for coldies. Yes, I'm clutching at straws. Yes, I'd have more chance of winning the lottery than seeing those snowflakes on 23rd Dec! 

No sign of SSW just yet to add fuel to the coldie fire. And PV seems to have its act together.

ECMWF anomaly analysis certainly drains the confidence without something significant to shift the pattern.

Seasonally, I look to Feb/March for colder indicators. Otherwise, I hope for a more average winter overall, with a least a couple of shots at snowy interest away from upland northern Britain.

Edited December 18, 2019 by Selliso

[Mike Poole]

GEM seems to be going very much with UKMO T144, in fact even more so with the ridge, GEM left:

Of course as the GEM goes on to T240, we get an idea how the UKMO would progress too...

Edit, GEM T180, potential for WAA I think this might be a good run:

Edited December 18, 2019 by Mike Poole

[daz_4]

Well, GFS OP serves up pretty mild new year's eve for Europe. Over to GEFS if there is something more interesting but today's runs are very underwhelming to say the least.

[Glacier Point]

GFS op advertising the direction of travel for the New Year given current thinking..

[Mike Poole]

GEFS thumbnails at T276:

Recurrent theme, no organised trop vortex, and again high heights incursions in and around our region looking more likely than elsewhere, nothing firmed up on at all though on what the eventual pattern might be.  

[Kirkcaldy Weather]

Plenty of interest in the GEFS        

and this one for fun... A 1060mb Russian / Siberian high joining forces with higher pressure across Scandi