Model Output Discussion - Into Winter

[PiscesStar]

2 hours ago, BartyHater said:

Like many in here I'm really not sure how next week will pan out, but if nothing else we have some interest on day 1 of winter, rather than having to wait for day 90.

Clearly the constant battle between air masses for supremacy is what meteorology is all about, but what fascinates the vast majority of us in here are the ongoing winter battles, which in recent years the Atlantic army has been far to strong and significantly better organised than its foe....currently however things seem to be different, not least because the block army has spent much of late Autumn fortifying its position and building up its strength for what lies ahead - meaning this winter we have a ringside seat on what looks set to be a much fairer, much closer contest. 

T-91 Let battle begin! 

Looks like the south East loses out which is pants  

[booferking]

6 minutes ago, Kasim Awan said:

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.

It's a pretty extensive frosty morning across 2 continents.

[josh-weather]

To be fair it doesn't have to go all the way across the continent to end the cold spell in the UK!

[That ECM]

I think there’s some confusion in the thread. I don’t think anyone is suggesting a frost in Oxford can stop a low. What some of us are suggesting is that the output is suggesting that the progression of the lows is being over done . Hope that makes sense and hasn’t added more confusion.

Edited December 1, 2023 by That ECM

[booferking]

There's a serious signal late on the gefs 6z for scandi height rises biggest I've seen yet.

https://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=300

[LRD]

24 minutes ago, Kasim Awan said:

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.

Sounds like how my bladder feels after a few beers

Interesting debate on the cold air thing. I was never convinced that it was difficult to remove until the other day when the Met Office mentioned it. And, let's face it, they know more than me. I get that there is cold air and then there is cold air and it all depends on precise conditions

Ensembles are still indicating the last 2 GFS ops are overdoing warm(er) 850s into Scandi

But for Blighty good old wind and rain looks to return. Standard stuff

Edited December 1, 2023 by LRD

[tight isobar]

3 minutes ago, booferking said:

There's a serious signal late on the gefs 6z for scandi height rises biggest I've seen yet.

https://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=300

Big- signal. We gain on this

[johnholmes]

Meteorology is 3 dimensional not one dimensional; I was making a 3 dimensional comment.

[Met4Cast]

I think some have to accept that the cold isn’t going to last forever and no amount of wishing or hoping is going to make a difference

The first few lows disrupt & slide through the weekend & early next week bringing a snow risk on the northern flank. Exactly where these track remains uncertain. 

The blocking & forcing on these lows is weakening into next week & we will see milder (or less cold) air moving across the UK by mid-late next week, it’s possible we might get an extra day or two if models are underestimating the strength of blocking but that’s about it. 

Returning momentum into the Atlantic has already been set in progress. What happens week 2 however is of interest, a south shifted jet + steep thermal gradient could produce some deep lows. 

We need to watch Scandinavia, slight trend to blow away the cold but seems less likely currently, still a risk we could tap into it occasionally.

p.s watch for Scandi highs. 

Edited December 1, 2023 by Met4Cast

[tight isobar]

Singular snap gefs 6z geopots @ 500 that blocking is becoming both steadfast/ extensive. The run for the desired alignment .. is triggered

[johnholmes]

On Tuesday ( 28/11) NOAA 8-14 is much the same as the previous one so a broad westerly is to be expected within that time frame; meridional still on the 6-10

Friday 1 December - Another look at NOAA and ECMWF

NOAA 6-10 has no signal for blocking over the last 3 days or so and its 8-14 chart continues this. However the contour values arriving over the UK  are about/a bit below average so although less cold than now, not mild by any means. A similar temperature level from the ECMWF output for a similar period to NOAA 6-10 day. The overall 500 mb pattern on both outputs is broadly westerly, a touch north of west at times. On the NOAA 6-10 and 8-14 you can see that the usual major trough around ne Canada is nothing like as deep as we usually see around the start of winter. The trough off western USA/Canada shows on the 6-10 but not really on the 8-14. So we see a generally westerly 500 MB flow over much of the chart extending into Europe with no signal for any marked European trough.

This all suggests to me that whilst deep cold is unlikely in the 6-14 day period, neither is any really mild air, other than perhaps now and then for the far south of the UK. Snow probably confined to high ground from the Peak District north but on lower ground at times further north. Beyond 14 days then that is not for these charts.

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

[Purga]

Certainly no clear cut road to mild zonality

[BartyHater]

12 minutes ago, Met4Cast said:

I think some have to accept that the cold isn’t going to last forever and no amount of wishing or hoping is going to make a difference

The first few lows disrupt & slide through the weekend & early next week bringing a snow risk on the northern flank. Exactly where these track remains uncertain. 

The blocking & forcing on these lows is weakening into next week & we will see milder (or less cold) air moving across the UK by mid-late next week, it’s possible we might get an extra day or two if models are underestimating the strength of blocking but that’s about it. 

Returning momentum into the Atlantic has already been set in progress. What happens week 2 however is of interest, a south shifted jet + steep thermal gradient could produce some deep lows. 

We need to watch Scandinavia, slight trend to blow away the cold but seems less likely currently, still a risk we could tap into it occasionally.

p.s watch for Scandi highs. 

Agree entirely with this....No UK winter has or ever will be a 3 month freeze up, it's all about once a mild pattern sets ups, how quickly can we get back to cold.

The answer to that question across many recent winters has been gauged in months rather than days or weeks, in some cases almost 3 complete months, this season feels different - whether

or not it proves to be of course remains to be seen.

[Met4Cast]

It’s good to finally see the ECM & GFS picking up on this current amplified MJO pulse. The BOM model has done rather well with this. 

A slow (and weakening) transition through phase 8 seems likely which is an early indication for a more sustained period of high latitude blocking. 

An amplified phase 4/5/6 will increase +FT & +MT rising the AAM quite sharply, not to mention put increasing pressure on an already weak stratosphere vortex, I’d not be surprised to see an increasing signal for an SSW sometime in early January. 

In terms of the background forcing this winter is showing more promise than any winter since 2009/2010 for me. 

[That ECM]

If I was living north of Swindon I’d be looking at tomorrow evening/Sunday morning with interest.

[Stabilo19]

6 minutes ago, Purga said:

Certainly no clear cut road to mild zonality

Agreed, the 0Z GEFS mean barely goes above 30 yr average and spends 75% of the time below it up to 17th Dec.

It might be less cold than now but it's still looking chilly & seasonal for the foreseeable..

[bluearmy]

35 minutes ago, Kasim Awan said:

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.

I assume that what many are looking at is the huge mass of frigid air building over scrussia - this can deflect the jet on a more se trajectory. We would expect that the eps with 137 vertical levels a would resolve this better than the gefs. But it’s all connected and if we do see a scandi high establish and split the flow just west of the U.K. then it will likely be due to several factors and not just the cold mass of dense air to our ne assisting in holding the current majority west to east modelled pattern further west. 
 

housekeeping - ec 06z a bit further north with the cold air sun am and also with the Mon am snow on the northern edge of the runner 

[Kasim Awan]

Just now, bluearmy said:

I assume that what many are looking at is the huge mass of frigid air building over scrussia - this can deflect the jet on a more se trajectory. We would expect that the eps with 137 vertical levels a would resolve this better than the gefs. But it’s all connected and if we do see a scandi high establish and split the flow just west of the U.K. then it will likely be due to several factors and not just the cold mass of dense air to our ne assisting in holding the current majority west to east modelled pattern further west. 
 

housekeeping - ec 06z a bit further north with the cold air sun am and also with the Mon am snow on the northern edge of the runner 

Yes that is true, inherently because the jet is weaker as it reaches Russia and the surface cold is stronger on a scale of thousands due to the effect of surface snow aswell, that we don't have. So the effect is amplified hugely. 

[bluearmy]

8 minutes ago, Met4Cast said:

It’s good to finally see the ECM & GFS picking up on this current amplified MJO pulse. The BOM model has done rather well with this. 

A slow (and weakening) transition through phase 8 seems likely which is an early indication for a more sustained period of high latitude blocking. 

An amplified phase 4/5/6 will increase +FT & +MT rising the AAM quite sharply, not to mention put increasing pressure on an already weak stratosphere vortex, I’d not be surprised to see an increasing signal for an SSW sometime in early January. 

In terms of the background forcing this winter is showing more promise than any winter since 2009/2010 for me. 

The likely stand off between the Atlantic and the Siberian block coupled with repetitive Aleutian lows will drive trop waves into the strat which an already weakened spv may find hard to cope with. Should certainly ensure a weakened spv continues through much of December after a short recovery towards average next week.  

[MATTWOLVES 3]

1 hour ago, 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.

I think Kas the real talking point on here the last few days as been whether the fact the cold block can hold out from the Atlantic push.If that cold air locks in place we are in a better position moving forward. I don't think many or any really thought a several day cold surface pool would be enough to stop an Atlantic push.

Your pointing out there's a lot of false hope in here...yet how many times in the last few days have you changed your mind and forecast? One minute you've said it's looking good for the cold to hold on....the next its not looking good at all. Then we are looking well placed for snow events,for a few hours later to state its not set up properly for snow events due too the nature of the sypnotics!

I'm not having a dig at you cause your obviously very well educated, but to say many in here have false Hope is kind of pot kettle and black.

 

 

 

 

 

Edited December 1, 2023 by MATTWOLVES 3

[Paul]

There's no doubt that if the cold had the same will to to stick around as some have when it comes to having the last word in any debate in here, then it'll hang on uninterrupted until May. Can we maybe move on from 'cold block' gate now, please?

[LRD]

19 minutes ago, DIS1970 said:

Saw this junk a couple of days ago, nearly pi**ed myself, said 80" of snow would fall - from the Daily Mail.

Look at all the other cobblers the Mail publishes too. And people are caught hook, line and sinker with it

MOGREPS with a much more solid looking signal for mild to win out this time next week. Similar looking signal in other places too... even in Aberdeen. Might not last long as some of the teleconnection-savvy folk on here are saying but it's there

Edited December 1, 2023 by LRD

[Catacol]

1 hour 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'm no physicist....but there are plenty of known model issues.

Model Biases and Verification

WWW.WPC.NCEP.NOAA.GOV

Note this line on UKMET - "Has problems with shallow cold air."

I suspect this problem is more complex than you are making out, and there is always a role for observation. Observationally, as John has much experience of, cold blocks give ground slower than modelled. Many have noted this over many years without any clear sense that a slider slides, or a system rebounds, because the jet itself is overmodelled each time. As with everything - a complex relationship.

Edited December 1, 2023 by Catacol

[Jacob]

NAVGEM keeping us in colder air

Edit: There's also deeper cold in Scandinavia 

Edited December 1, 2023 by Jacob

[Severe Siberian icy blast]

11 minutes ago, LRD said:

Look at all the other cobblers the Mail publishes too. And people are caught hook, line and sinker with it

MOGREPS with a much more solid looking signal for mild to win out this time next week. Similar looking signal in other places too... even in Aberdeen. Might not last long as some of the teleconnection-savvy folk on here are saying but it's there

You think that's a coherent signal for milder air? Disagree, its a flat line until the 7th for Aberdeen and then a 75/25%  in favor or mild for now but it's as week away and you can see some of the members keep it freezing.