Model Output Discussion - Into Winter

[Rob 79812010]

Quite a number of the ensembles hint at average to slightly below temps toeard mid month. Given the great start to Dec I'm grateful that we appear not to be going into a full on tropical spell which is sometimes the case. Dec likely below average at mid point of month then who knows after that

[Battleground Snow]

1 minute ago, TSNWK said:

Ooooooo the south east pretty please 

Turns to rain after about 6 hours, but better than nothing haha

[Ali1977]

I have a feeling some big snow events could happen down south into Monday

[steveinsussex]

Just now, Ali1977 said:

I have a feeling some big snow events could happen down south into Monday

Yes but where is down south to you?! Earlier south was the midlands

[Harveyslugger]

2 minutes ago, Ali1977 said:

I have a feeling some big snow events could happen down south into Monday

You are at a good elevation too goodluck

[northwestsnow]

Monster siberian high

[Kasim Awan]

47 minutes ago, johnholmes said:

The difficulty of milder air pushing dense cold air away is not myth it is meteorological fact. Was pre model days and still is. No one has found a way of solving this so far. How many days for deep cold to affect the milder air coming in, how dense the cold air both at the surface and the bottom 3-5,ooo ft. The direction in which a low approaches, some seem less likely to advance than from slightly different directions. It makes trying to forecast the arrival of genuinely mild air still almost as difficult as it was pre computer models.

 

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.

[Ali1977]

10 minutes ago, steveinsussex said:

Yes but where is down south to you?! Earlier south was the midlands

Sorry yeah, I’m initially from Cumbria so still class anyway south of Manchester as south I guess the midland is in with a best chance - Arpege shows this well 

That’s not a typical winter chart - hopefully we can move on from this cold spell straight into another fruitful chase ️️ 

Edited December 1, 2023 by Ali1977

[Empire Of Snow]

20 minutes ago, Rob 79812010 said:

Just silly isn't it

It's not just silly, it's on the verge of illegality and against the principles of journalism. 

Sorry for the off-topic but it's outrageous how these "journalists" are getting away with everything. 

[Derecho]

The problem with the output this morning is that an area of low pressure between Norway and Greenland changes the orientation of the high further NE.

The intense cold doesn't reach Scandi and is more confined to western Russia.

The mild air then has a free ticket to push through Scandi later in the run.

Poor output sadly.

[Kentish Snowman in Yorks]

1 minute ago, Derecho said:

The problem with the output this morning is that an area of low pressure between Norway and Greenland changes the orientation of the high further NE.

The intense cold doesn't reach Scandi and is more confined to western Russia.

The mild air then has a free ticket to push through Scandi later in the run.

Poor output sadly.

Yeah but is it right?  The actual weather might have other ideas?  Intriguing output to keep us on the edge of our seats at least.

Fully expecting another swing back to extended cold on this afternoons runs as I just cannot see that cold over Scandi being shifted so easily...

[MATTWOLVES 3]

4 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.

Come on Kasim..If all these multi million pound computers made it so easy we would simply not need to bother coming on here numerous times a day to check the direction of travel,as the models would have the pattern nailed all the time. Yet in reality we see long range forecasts bite the dust yearly,and several day forecasts sometimes miles out!

Yes your qualified and your good at it...but remember Jon H is as old school as they come. He was probably drawing charts when I was in my nappies.. And I always say you can't beat the old guard of Weather forecasters.

[Kasim Awan]

Times have changed since the 1970s, computer models worth the GDP of Kenya are likely to know that cold air is denser than warm air, and a result factor it in.

[BartyHater]

22 minutes ago, IDO said:

The problem with the 06z is that although the block to the east is holding firm, it is too far east, so we do not benefit, and the UK is stuck in no man's land for days on end:

A west-based UK trough isn't a good block. Just one run, and hopefully, GFS is still underestimating the block to the east.

 

 

Indeed, would far rather see everything pushing through rather than the UK becoming the kind of frontal graveyard we've seen in recent winter - that can lead to some big rain totals

[northwestsnow]

GFS 6z is trying to link up Atlantic heights to the Siberian high..

[Kasim Awan]

Just now, MATTWOLVES 3 said:

Come on Kasim..If all these multi million pound computers made it so easy we would simply not need to bother coming on here numerous times a day to check the direction of travel,as the models would have the pattern nailed all the time. Yet in reality we see long range forecasts bite the dust yearly,and several day forecasts sometimes miles out!

Yes your qualified and your good at it...but remember Jon H is as old school as they come. He was probably drawing charts when I was in my nappies.. And I always say you can't beat the old guard of Weather forecasters.

All I'm referring to is that in this context the cold surface layer is unlikely to be able to throw off the models indication of a strong breakdown. I was put down for supporting the GFS's idea of this cold spell and also put down for saying this flow will (early on) be void of much snow. Although the latter still has time to change, I can't see the high resolution NWP not factoring in cold layer in surface pressure patterns.

[Midlands Ice Age]

1 minute ago, Kasim Awan said:

Times have changed since the 1970s, computer models worth the GDP of Kenya are likely to know that cold air is denser than warm air, and a result factor it in.

I totally agree with Mat here Kasim.

You can have the whole computing power of the world hooked up to this.

But the output is only as good as the assumptions (and their correctness) built into the model.

MIA  

[Derecho]

3 minutes ago, Kentish Snowman in Yorks said:

Yeah but is it right?  The actual weather might have other ideas?  Intriguing output to keep us on the edge of our seats at least.

Fully expecting another swing back to extended cold on this afternoons runs as I just cannot see that cold over Scandi being shifted so easily...

Well it's in an area that may not have a great number of observations so that troublesome little feature is by no means nailed on. The low could just quickly fizzle out and a Scandi high could be allowed to build.

A few GFS ensemble members show this but no operationals yet in what is a tightening window for change. 

[Kasim Awan]

3 minutes ago, MATTWOLVES 3 said:

Come on Kasim..If all these multi million pound computers made it so easy we would simply not need to bother coming on here numerous times a day to check the direction of travel,as the models would have the pattern nailed all the time. Yet in reality we see long range forecasts bite the dust yearly,and several day forecasts sometimes miles out!

Yes your qualified and your good at it...but remember Jon H is as old school as they come. He was probably drawing charts when I was in my nappies.. And I always say you can't beat the old guard of Weather forecasters.

Models can be wrong / may delay the cold but it wont be due to underestimating surface cold, more so due to a more medium range factor such as higher strength 500mb blocking than modelled or a change in a background signal.

[That ECM]

1 minute ago, Kasim Awan said:

All I'm referring to is that in this context the cold surface layer is unlikely to be able to throw off the models indication of a strong breakdown. I was put down for supporting the GFS's idea of this cold spell and also put down for saying this flow will (early on) be void of much snow. Although the latter still has time to change, I can't see the high resolution NWP not factoring in cold layer in surface pressure patterns.

“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. 
 

 

[Battleground Snow]

You Can see how close the link up is on the gefs,

As we approach t0, I'd expect the lows to make less progress.

 

[Kasim Awan]

4 minutes ago, Midlands Ice Age said:

I totally agree with Mat here Kasim.

You can have the whole computing power of the world hooked up to this.

But the output is only as good as the assumptions (and their correctness) built into the model.

MIA  

I agree with that, but disagree with the outdated ascertion that surface cold can completely change an outlook which is in part governed by upper level patterns, not some frost pocket in Oxfordshire.

Just now, 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. 
 

 

Once a big low sweeps in a little bit of localized cold is not going to make any difference. If the pattern was more delicate there may have been an argument, but from the charts indicated, upper level flows absolutely trump any surface influence.

[That ECM]

5 minutes ago, Kasim Awan said:

I agree with that, but disagree with the outdated ascertion that surface cold can completely change an outlook which is in part governed by upper level patterns, not some frost pocket in Oxfordshire.

Once a big low sweeps in a little bit of localized cold is not going to make any difference. If the pattern was more delicate there may have been an argument, but from the charts indicated, upper level flows absolutely trump any surface influence.

We await to see if they sweep in.

[Jackski4]

2 minutes ago, Kasim Awan said:

I agree with that, but disagree with the outdated ascertion that surface cold can completely change an outlook which is in part governed by upper level patterns, not some frost pocket in Oxfordshire.

Once a big low sweeps in a little bit of localized cold is not going to make any difference. If the pattern was more delicate there may have been an argument, but from the charts indicated, upper level flows absolutely trump any surface influence.

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. 

[Kasim Awan]

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.