Model Output Discussion - moving into Winter

[Catacol]

12 minutes ago, CreweCold said:

We do run the risk of the trop PV running rampant if we don’t get the blocks in the right places. As I’ve said previously, the strat and trop will try to couple week 2. Any spoiler LPs or shortwaves could actually lead to a pattern collapse…we’d have to be REALLY unlucky for that.

Not seeing much evidence of coupling yet - unless you have access to something I don't. Losing the Berlin charts is irritating - but the anomaly charts on weatheriscool suggest the trop is yet to be impacted by a strengthening strat

At day 10 the trop vortex and lower strat are weak north of 60

Not much wrong with the lower strat forecast at 10 days either - not a bad setup to allow cold air to back west as December progresses

 

 

 

[Allseasons-Si]

1 minute ago, blizzard81 said:

So similar to ecm mean. 

Similar yes but better heights into Greenland on the ECM mean here at day ten.

but the gefs mean is still OK,just not as good as the 12z.

anyway,...the interest lies beyond this so lets see how the rest of the 18z gefs and mean pan out.

[Met4Cast]

Yikes.. 

Pretty sizeable shift in the ensembles there. The problem we've had for days now is still there, a complete lack of access to cold air despite the blocking. 

[Cold Winter Night]

Tonight's runs have made me a bit more cautious about the extended period TBH.
Downgrade is far too big a word, but I've seen the introduction of some clusters and options that I'd rather not see.

Comparing the EPS 12z De Bilt plume with yesterday's illustrates this point.
- Up to December 4: Decent, seasonal, milder options have disappeared.
- December 6-10 (216h-360h): Not liking the milder routes creeping in, including HRES and Control. The clusters suggest a Greenland High that moves too far Northwest, with the trough ending up too far West, and De Bilt in a S/SW/W flow.

It's far out, no really big swings, nothing to really worry about, but let's keep our feet on the ground.
Those mean charts look superb indeed, but the quick and sudden move to Greenland High anomalies should halt tomorrow.
No overshoot into N-Canada please.

[*Stormforce~beka*]

21 minutes ago, johncam said:

The problem is any real cold is getting pushed further and further back 

Not like we have EVER Seen this happen before ...!!! Didn't we all learn from last year?!! I'm not even going to look at the charts properly until the end of next week.

[Cheshire Freeze]

4 minutes ago, Catacol said:

Not seeing much evidence of coupling yet - unless you have access to something I don't. Losing the Berlin charts is irritating - but the anomaly charts on weatheriscool suggest the trop is yet to be impacted by a strengthening strat

At day 10 the trop vortex and lower strat are weak north of 60

Not much wrong with the lower strat forecast at 10 days either - not a bad setup to allow cold air to back west as December progresses

 

 

 

It never shows up in those charts until near to or after it happens. I learned that back in 2016. Everyone was saying there was no sign of coupling then bam, almost overnight we know what happened…

I can tell just by looking (from experience) the charts where the strat is downwelling.

Edited November 26, 2022 by CreweCold

[terrier]

24 minutes ago, johncam said:

The problem is any real cold is getting pushed further and further back 

It’s not about been pushed back. Look at the trend. We are heading colder and the building blocks are there for something much more potent further down the line. We are in a much better position than we have been in recent years. Certainly beats mild westerly winds and Atlantic dross. The polar vortex at the moment is like boxer on the ropes. Just a case of the final knock out punch. 

[Rain All Night]

51 minutes ago, lorenzo said:

Not at all and it's a great call out. Parallel is on the other side of the envelope, given the prior trends and clusters a rebound to the chart below would represent quite a coup. Ens will be worth a look. 

What is that chart on the right?

[Bristawl Si]

31 minutes ago, johncam said:

The problem is any real cold is getting pushed further and further back 

Was it ever forecast to reach its 'preferred' destination?

[blizzard81]

Feels like some are over analysing this evening. Looking for unlikely pitfalls. 

[Catacol]

25 minutes ago, CreweCold said:

It never shows up in those charts until near to or after it happens. I learned that back in 2016. Everyone was saying there was no sign of coupling then bam, almost overnight we know what happened…

I can tell just by looking (from experience) the charts where the strat is downwelling.

We do have a trend towards greater coherence between the layers even if the lower strat is currently remaining clear of downwelling wind speed increases - but I'm not seeing that as a concern. In 5 days quite a clear disconnect

High pressure anomaly up to 30hpa with anomaly lowered above that - resulting in forecasted increases in vortex at 10hpa

....but the coupling evident out at 240h is really only a reflection of the trop-led strong building of heights driving straight up and through to 5hpa. Coherence through the layers, but the high pressure spanner preventing uptick in wind speeds. With decent eddy flux up over Asia - maintaining wave 1 impacts for the longer term - all I see here is a potential tendency to open the doors to colder air arriving in Europe mid month provided heights over SE Europe can drain away.

Jules would have us believe that this never happens anymore - and we know sub tropical high pressure is getting more and more stubborn as the years roll by - but the longer we keep the ridge to the north, and especially if it doesnt retrogress too far west, the more likely a Romanian positive anomaly will fade. This, of course, is all built on the foundation of GFS forecasting, hardly the most reliable thing to lean on - though the EPS is also fairly consistent in seeing this significant trop built high pressure to our NE. I wish it wasn't so quick to retrogress - it possibly lowers our chances of more sustained positive cold patterns into January - but Que Sera.

If you have mastered the skill of looking at a 10hpa or 30hpa or 50hpa contour map and know just by looking at it when and where strat impacts will downwell regardless of other model data then I'd get emailing the MetO fast. You'll make an absolute fortune...

Edited November 27, 2022 by Catacol

[Don]

11 minutes ago, blizzard81 said:

Feels like some are over analysing this evening. Looking for unlikely pitfalls. 

You really can't blame them after past experience and this is Britain!!

[blizzard81]

6 minutes ago, Don said:

You really can't blame them after past experience and this is Britain!!

I'm with you mate but if the signs are there in good fold, we should be rejoicing

[Cheshire Freeze]

I'm waiting to see the morning's runs before I pass anymore comment.

Hopefully the GFS products have had a slight wobble this 18z.

I'm off work Monday so I should be able to put more of a shift in on here tomorrow night.

Edited November 27, 2022 by CreweCold

[Mucka]

The orientation and timing of the Atlantic low at day 6/7 will be key as to whether we can get a quicker progression to a Greenland high and cold. 

As always the Atlantic need to be blocked off from sneaking through under the Southern tip of Greenland and preventing proper regression.

Two examples from GFS ensembles.

 

YES

 

NO

 

One doesn't guarantee cold and the other mild and there could be other attempts if blocking persists but it is a big part of the puzzle.

[blizzard81]

Just now, CreweCold said:

I'm waiting to see the morning's runs before I pass anymore comment.

Hopefully the GFS products have had a slight wobble this 18z.

ECM and UKMO cemented it today. Cmon... The GFS 18z is crud at the best of times. I would have been more worried this evening if it had showed wintry nirvana. 

[Cheshire Freeze]

24 minutes ago, Catacol said:

We do have a trend towards greater coherence between the layers even if the lower strat is currently remaining clear of downwelling wind speed increases - but I'm not seeing that as a concern. In 5 days quite a clear disconnect

High pressure anomaly up to 30hpa with anomaly lowered above that - resulting in forecasted increases in vortex at 10hpa

....but the coupling evident out at 240h is really only a reflection of the trop-led strong building of heights driving straight up and through to 5hpa. Coherence through the layers, but the high pressure spanner preventing uptick in wind speeds. With decent eddy flux up over Asia - maintaining wave 1 impacts for the longer term - all I see here is a potential tendency to open the doors to colder air arriving in Europe mid month provided heights over SE Europe can drain away.

Jules would have us believe that this never happens anymore - and we know sub tropical high pressure is getting more and more stubborn as the years roll by - but the longer we keep the ridge to the north, and especially if it doesnt retrogress too far west, the more likely a Romanian positive anomaly will fade. This, of course, is all built on the foundation of GFS forecasting, hardly the most reliable thing to lean on - though the EPS is also fairly consistent in seeing this significant trop built high pressure to our NE. I wish it wasn't so quick to retrogress - it possibly lowers our chances of more sustained positive cold patterns into January - but Que Sera.

If you have mastered the skill of looking at a 10hpa or 30hpa or 50hpa contour map and know just by looking at it when and where strat impacts will downwell regardless of other model data then I'd get emailing the MetO fast. You'll make an absolute fortune...

Obviously I didn't mean I can tell the precise location of downwelling, just where there is downwelling in general.

Remember 2016? I think I was the first one to call that a bust as soon as that Greenland HP was shown not to hold (I took a load of flak for saying it too). I explicitly remember saying that there would be a swift coupling after that, despite what those plots were showing. Guess what happened...

I refer back to what I've been saying the past few days. I'd much rather see some heights hold to our E in order to keep the vortex on its toes and give us an insurance of a SSW. The beauty of that block to our E or NE is that even if the two vortices try to couple, it will just cause damage to the strat. A Greenland HP offers us no insurance, and if it fails then the pattern flattens hella quickly after it does.

Edited November 27, 2022 by CreweCold

[steveinsussex]

32 minutes ago, blizzard81 said:

Feels like some are over analysing this evening. Looking for unlikely pitfalls. 

The pro’s are not seeing anything in the models to indicate any level of cold other than normal chillier winter type weather. I think many in here are getting carried away.

[sukayuonsensnow]

21 minutes ago, steveinsussex said:

The pro’s are not seeing anything in the models to indicate any level of cold other than normal chillier winter type weather. I think many in here are getting carried away.

Yup agreed. What I don't expect to see in the first 10 days of December is any kind of very cold snowy spell, and if anyone has been following the long range forecasts this should have been at the back of everyone's minds.

Cloud, temperatures mid single figures (4-8c), in a chilly-but-not-especially cold E/NE wind is what I am expecting, maybe with coastal rain showers in the east. 

Towards mid December is uncertain at this stage, so FI should be treated as FI as a range of outcomes are possible. Probably a drier outlook than recently, and nothing especially mild. 

[Kirkcaldy Weather]

Still perfectly fine from my POV, 18z GEFS mean looks more impressive than previous suites 

 

[John88B]

3 hours ago, steveinsussex said:

The pro’s are not seeing anything in the models to indicate any level of cold other than normal chillier winter type weather. I think many in here are getting carried away.

Just some chilly seasonal weather would do me just fine through December and the run up to Christmas with the hope of it leading to something even colder. It looks perfectly feasible to me.

[Dave Kightley]

UKMO very good... GFS better then 18z not but not great upto 200 with less cold air pumped up from the South west.. zzz so not really a cold spell in South to this point.. UKMO very much better run

GFS turning into a nightmare.. pass on it.. really poor run loses heights... Leave in the south... Won't be seeing a cold spell on that run .

 

Edited November 27, 2022 by Dave Kightley

[Rayth]

15 minutes ago, Dave Kightley said:

UKMO very good... GFS better then 18z not but not great upto 200 with less cold air pumped up from the South west.. zzz so not really a cold spell in South to this point.. UKMO very much better run

GFS turning into a nightmare.. pass on it.. really poor run loses heights... Leave in the south... Won't be seeing a cold spell on that run .

 

Yep , but the para is better for Greenland blocking but the HP from rising around Italy blocks the cold feed

All up for grabs in the extended 

 

 

[Dave Kightley]

16 minutes ago, Rayth said:

Yep , but the para is better for Greenland blocking but the HP from rising around Italy blocks the cold feed

All up for grabs in the extended 

 

 

I would say we need the pattern further south on GFS .. to the point there really isn't a cold spell for south on that run as the battleground of SW and E is to far N.. to the point it could avoid give northern blocking a cold air mass.. such a lemon run for the south really

Edited November 27, 2022 by Dave Kightley

[Kasim Awan]

5 hours ago, blizzard81 said:

Feels like some are over analysing this evening. Looking for unlikely pitfalls. 

The initial easterly was never going to produce any meaningful cold so over analysing surface conditions and synoptics for it is a waste of time. Attention should be on establishing a strong blocking regeime & any further cold pushes from the NE.