Model Output Discussion - Into Winter

[Empire Of Snow]

4 minutes ago, That ECM said:

“Put down” or some suggested a differing opinion?

My opinion is that the output is underestimating the cold in that it is moving it away to quickly. I May well be wrong and if so hey ho. 
 

 

Which cold do you mean, surface or the cold pool in the NE? Surface cold, especially prolonged one, can play its part with systems like the potential one this Sunday. On the other hand even a strong -20 850hpa cold pool can be eradicated quickly by Atlantic systems. 

[Kasim Awan]

Just now, Jackski4 said:

I can’t believe you’re all having such a disagreement when Santa Claus is literally on his way to town!

 

To add my two pennies worth in, I do think there could be a flip this afternoon, heaven knows why but it seems the overnight runs always leave a sour mood in here in the mornings. 

I'd call it around a 10-15% chance of such flip, and it wont be because of a self perceived bias notion.

[sorepaw1]

When you get a 1056mb Siberian High , and a 1045mb Scandinavian High trying to merge isn't that the time to abruptly sit up and watch.

Interesting times ahead. 

[Jackski4]

1 minute ago, Kasim Awan said:

I'd call it around a 10-15% chance of such flip, and it wont be because of a self perceived bias notion.

I’m gonna go for a 17% chance just so I look more knowledgeable than you if it happens

[Kasim Awan]

4 minutes ago, Empire Of Snow said:

Which cold do you mean, surface or the cold pool in the NE? Surface cold, especially prolonged one, can play its part with systems like the potential one this Sunday. On the other hand even a strong -20 850hpa cold pool can be eradicated quickly by Atlantic systems. 

I am referring to the confusing notion that surface cold can holdback a powerful low pressure system. Ofcourse surface cold will pay a part in snow, if it was mild at the surface tomorrow night would be rain due to unsupporting temperatures aloft. Freezing rain looks an issue where the aloft warm layer is too expansive, it looks to creep above freezing for parts of the Midlands. North of here uppers are that bit colder allowing for less of a warm layer aloft and an all snow conducive system.

Edited December 1, 2023 by Kasim Awan

[tight isobar]

The start of the finish of the vortex!! Whatta starting point

[Mike Poole]

Just now, Kasim Awan said:

It seems there is a lot of false hope in here. There is no way that surface cold can stop such forcing associated with a low like this. We will come back in 7 days time and see whether that -8C recorded yesterday was able to change southwesterlies to easterlies. If this backtracks, it wont be due to a surface inversion, it will be due to a medium range factor such as stratosphere AAM MJO or a large scale mid to upper level pressure system. Model inaccuracies related to overdoing temperatures during a breakdown are only temporary and surface based.

That may well be true, Kasim.  But a ‘low like this’ probably isn’t going to happen.  My view is the model has got this wrong earlier which is why it has got itself into this position, and that the solution should be more modest, disrupted lows as the jet tracks to the south.  

[Kasim Awan]

Just now, Mike Poole said:

That may well be true, Kasim.  But a ‘low like this’ probably isn’t going to happen.  My view is the model has got this wrong earlier which is why it has got itself into this position, and that the solution should be more modest, disrupted lows as the jet tracks to the south.  

I disagree, I can't see full model backtracking of such a powerful jet stream. Though it is possible, if it happens it will be due to models overestimating the jet stream and not underestimating the influence of surface cold.

[Snowman.]

Mean 6z vs 0z

  

 

The wrap around heights to the north is very apparent, as the atlantic hits the block east it is throwing a ridge ahead, while that is likely to draw southerly winds it may lead to height building to the NE.

As this continues you can see heights to the NE "winning" out and the trough becomes more negatively aligned.

Not far off an Easterly at this moment. If I was to hedge a conservative bet, below is looking like where we could end up. Almost a stalemate nice block NE but not far enough west. 

Now if we are lucky we need to see a ridge at around 120 mark we need see a vertically aligned trough building a ridge ahead of it.

 is what we are after

 horror show.

 

There are some absolute peaches in the ensembles, but rides or dies on how much amplficiation we can get earlier on.

Edited December 1, 2023 by Snowman.

[Mike Poole]

Just now, Kasim Awan said:

I disagree, I can't see full model backtracking of such a powerful jet stream. Though it is possible, if it happens it will be due to models overestimating the jet stream and not underestimating the influence of surface cold.

Quite possibly.  I think some model runs are definitely overestimating the jet stream, and that might be because the model hasn’t quite got the heights right near Greenland, rather than the downstream cold pool.

[warrenb]

Do remember once in the 80's when a low was supposed to blow away the cold, it snowed all day, then pushed back west and the freeze continued for about another week. But this is very rare and suspect with AGW things have changed. The Jet is firing up, the writing has been on the wall for several days, please lets stick to forecasting and not hopecasting.

We all look at the operationals as if they are the only source of information. Each of these organisations run a full ensemble suite, and every video I see from the METO I see they always say they go mostly with the ENS. I look at the OP but it is the ensembles I try to get the information from.

Edited December 1, 2023 by warrenb

[Aiden2012]

I personally think we’re all clutching straws here, not seeing much change now but what do I know

[Kasim Awan]

1 minute ago, warrenb said:

Do remember once in the 80's when a low was supposed to blow away the cold, it snowed all day, then pushed back west and the freeze continued for about another week. But this is very rare and suspect with AGW things have changed. The Jet is firing up, the writing has been on the wall for several days, please lets stick to forecasting and not hopecasting.

This would be due to models not accurately resolving pressure level interactions, not surface temperatures. It may appear that it is the former being underestimated as the backtrack results in colder temperatures. The fact that computer modelling was a fair bit less accurate back then made that more likely aswell.

[CoventryWeather]

Weren't Mondays low like 2-3 days ago right over the top of the UK? Elsewise, I agree with others here, feel the lows will slide - models have been underdoing the cold and extent of wedges to the north. Not being biased, it's a solution that I and many feel is the most likely. 

[johncam]

High is too far east , therefore we will get stuck with fronts and lows grinding to a halt over us , if that happens could be a lot of rain. Hope they have it wrong.  

[TSNWK]

12 minutes ago, tight isobar said:

The start of the finish of the vortex!! Whatta starting point

Really.. looks like a raging vortex precisely where we don't want it

[LRD]

12 minutes ago, tight isobar said:

The start of the finish of the vortex!! Whatta starting point

What am I not seeing here? Because my take from that is that the vortex looks to be settling over Greenland and looks pretty strong if a little disorganised

[That ECM]

[Kasim Awan]

1 minute ago, johncam said:

High is too far east , therefore we will get stuck with fronts and lows grinding to a halt over us , if that happens could be a lot of rain. Hope they have it wrong.  

I think they are correct. The first low Monday / Tuesday slides, snow risk with that, but it leaves a ridge to our West / over the UK which will likely bind with the Azores high, producing a perfect high pressure system for strong WAA into the UK later next week, resulting in a clean, strong south westerly air flow and minimal potential for disruption east by that stage.

[booferking]

49 minutes ago, Kasim Awan said:

You have misunderstood my post, I said cold air itself just the fact of it being cold being able to completely change an outcome when it is already modelled is not very likely. I have a formal qualification and meteorological interests myself so I am well aware that cold air is dense but this would not simply be overlooked by a 5 trillion pound computer.

Maybe time to get a job in the metoffice rewrite the rule books and recalibrate them 5 trillion pound computers

Main while the control has other ideas.

 

Edited December 1, 2023 by booferking

[tight isobar]

6 minutes ago, LRD said:

What am I not seeing here? Because my take from that is that the vortex looks to be settling over Greenland and looks pretty strong if a little disorganised

Indeed it does but by then - here there will be reverberated fluxes into the layers.. and with given waa notions that Canadian mother lobe will be draining dramatically, perhaps.. the dynamics are both good- And possibly very fruitful.. And have big aid- on rises at- And around the Scandinavian geographical.

Edited December 1, 2023 by tight isobar

[Kasim Awan]

1 minute ago, booferking said:

Maybe time to get a job in the metoffice rewrite the rule books and recalibrate them 5 trillion pound computers

They'll laugh in my face when I say a frosty morning can overpower a 250mph low pressure system holding 100 billion trillion tonnes of water.

[Matty88]

16 minutes ago, Kasim Awan said:

I disagree, I can't see full model backtracking of such a powerful jet stream. Though it is possible, if it happens it will be due to models overestimating the jet stream and not underestimating the influence of surface cold.

I think more to the point its the position of the jet - not the strength, that will be causing a wobbly or two. South shifted yes, potentially a disrupted path which has even a small chance of firing up heights and leading to an easterly. The models feel to me like they are back-tracking on shifting the European cold block and this may even grow as we head into next week. On the flip side - yes it may all collapse and mild air intrusion wipes out the cold. 

Interesting times ahead and model watching! 

[topo]

GFS ensembles show a completely different picture 

GFS operational almost an outlier with few members in the same path, while the vast majority is below the mean..

A bit similar with ECM 

So who wins? Ensembles or operational runs? I guess we will found out soon, but interesting that we see similar behaviour in both models

[knocker]

Put simply the ecm next week has intense trough development in the Atlantic driven by a strong jet which at the same time amplifies the Euro ridge which  effectively mixes out the colder air in the west, including the UK, and isolates the colder air to the east.

 

Edited December 1, 2023 by knocker