Model Output Discussion - Into Winter

[BartyHater]

The return of barbecues synoptic later next week suggests to me the models are probably overreacting to the mild signal and as a result we'll probably see them revert to something more credible in the coming days. That said there's no denying the return of the Atlantic, but the Scandi cold block clearly isn't going to capitulate in the same way our blocks often do - so my guess (for what its worth)  is after 4-5 day of mild weather, temps will return to near or a little below normal of the back of increasing cold zonality, as systems get edged increasingly farther south by the persistent Scandi block.

Edited November 29, 2023 by BartyHater

[sheikhy]

27 minutes ago, TSNWK said:

Save on the bills....

Yeh gfs tried mate but to no avail!shame really man!!!on to the next spell now i guess!!

[TSNWK]

Just now, sheikhy said:

Yeh gfs tried mate but to no avail!shame really man!!!on to the next spell now i guess!!

Yep.. brush ourselves down.  Maybe a day or two away from models and hopefully go again.. 

[tight isobar]

Expect to see even more fruitful Synoptics going into December- fairly soon there is a northern hem/ vortex distruption format to be beholden

[ANYWEATHER]

39 minutes ago, Bricriu said:

Our - Meteorological service- Met Eireann in its long range forecast is saying it will be mild and unsettled  for the rest of December. The only crumb of comfort for me is the EC46 didn't  go for this cold  spell and it can often flip in fi. I just hope we are not going to be stuck under slow moving systems for weeks on end due to heights to the North East.  We had enough rain over the last six weeks.

I could live with that if the high then migrated  north or north eastwards a few days later.  I know I am straw clutching 

I would imagine ,given that it's Ireland that's the easiest default long range forecast there is !

[adrianh]

The GFS reverts to it's standard default setting towards the end of its run with pumped up lows swirling round the Atlantic for days on end. With the current northern hemisphere profile, this seems unlikely but things will become more clear towards the weekend - if nothing else, its been nice to have the rain ease off for a while.

[booferking]

Plenty of blocking options on the eps 192hr think the ops are being to progressive.

Meteociel - Panel ECMWF/CEP

WWW.METEOCIEL.FR

 

Edited November 29, 2023 by booferking

[DIS1970]

May see a flake or two, won't need a shovel though.

[MattStoke]

3 minutes ago, DIS1970 said:

May see a flake or two, won't need a shovel though.

Some might. Not that GFS snow accumulation charts are to be trusted.

[LRD]

Short ensembles show that the 6z op was a very warm run. But the trend is clearly up, 850s-wise, next week. With the polar profile throughout the entire run, any mild spell might not last too long

 

[Dundeeguy]

Models underestimated amount of snow showers/ precip peppering from North Sea today… sign of things to come?
 

Nothing forecasted here all day from met office but currently snow showers on and off for past 30 mins leaving a light dusting. Don’t lose hope guys! 

Edited November 29, 2023 by Dundeeguy

[Met4Cast]

Looks like my expectation for an unsettled start to December is going to come to fruition after all, just with a bonus cold spell before hand. 

Quite a few turn their noses up at background drivers/teleconnections in this thread, I suspect due to a lack of understanding them but I think that’s a shame, they are an incredibly useful tool and add a lot of context to NWP outputs. 

 

The MJO continues it’s progression eastwards is a rather amplified state, this wave has been a little faster than modelled and is expected to reach the central Pacific sometime around mid December, meanwhile we should see overall GLAAM rising via frictional & mountain torque processes thanks to this MJO wave with WWB’s returning. 

i.e I don’t expect we’ll see an Atlantic onslaught for weeks on end, it’s very possible we see a switch to more blocked/colder conditions over the Christmas period > into early January. 

[Ali1977]

Don’t discount something much colder in the medium term, the GEFS ENS are really going for a scandy high by day 9, even the mean

[PiscesStar]

Are we talking no snow or a little for a few places. I'm confused  

[That ECM]

2 minutes ago, PiscesStar said:

Are we talking no snow or a little for a few places. I'm confused  

Go in the regionals. There’s some lucky members posting pictures of snow.

[LRD]

3 minutes ago, Ali1977 said:

Don’t discount something much colder in the medium term, the GEFS ENS are really going for a scandy high by day 9, even the mean

Even at the end of the very mild op run there were hints in deepest FI of a Scandi high wanting to form. 

[MATTWOLVES 3]

I think Nick..aka blue mentioned those eps trending positive for the Atlantic to hit the buffers before it gets chance to get going earlier.

Just had a little study of the 0z ecm ens and as you can see we have good support for more blocking episodes,and plenty which put the strat under constant pressure....and plenty that never have the PV gaining much strength and settling down in the wrong places at all.

From the met today for here...a cold weekend with sharp frosts and risk of snow flurries..what's not to like before we can possibly set ourselves up for a much better event later.

In the meantime enjoy the cold if it's your thing and perhaps keep an eye on any elderly neighbours..Trust me I know that some of them sit in the cold all day as they can't afford the heating! 

[Kasim Awan]

A good 5-10cm likely tomorrow afternoon in inland parts of South Devon, particularly Dartmoor. A chance of a covering in parts of south Somerset / Dorset aswell. Little on the coast.

[MATTWOLVES 3]

31 minutes ago, Met4Cast said:

Looks like my expectation for an unsettled start to December is going to come to fruition after all, just with a bonus cold spell before hand. 

Quite a few turn their noses up at background drivers/teleconnections in this thread, I suspect due to a lack of understanding them but I think that’s a shame, they are an incredibly useful tool and add a lot of context to NWP outputs. 

 

The MJO continues it’s progression eastwards is a rather amplified state, this wave has been a little faster than modelled and is expected to reach the central Pacific sometime around mid December, meanwhile we should see overall GLAAM rising via frictional & mountain torque processes thanks to this MJO wave with WWB’s returning. 

i.e I don’t expect we’ll see an Atlantic onslaught for weeks on end, it’s very possible we see a switch to more blocked/colder conditions over the Christmas period > into early January. 

There maybe some that dismiss the drivers as a joke,but I think many on here (me included) are happy to learn about them. You pointed out that Blocking was not possible due to know forcing behind it..but changes on a micro scale altered that logic. Not having a go at you over it as making 100% accurate weather predictions is nigh on impossible.

Sometimes the drivers can fail due to other little nuisances rearing there heads...but they do remain a solid pointer to where we may be heading weeks down the line..But some need to keep in mind that MJO moving into phase 7/8 will not guarantee a cold and blocked outcome...a strong PV in the wrong place can rule this out as we've seen many times before. And keep in mind if the teleconnections are barking up the wrong tree,then NWP is most likely going to be barking up the wrong tree also.

But yeh they are a very important tool and perhaps the few that decide to dismiss them purely refuse too learn by them...or really understand them.

Edited November 29, 2023 by MATTWOLVES 3

[booferking]

21 minutes ago, MATTWOLVES 3 said:

There maybe some that dismiss the drivers as a joke,but I think many on here (me include) are happy to learn about them. You pointed out that Blocking was not possible due to know forcing behind it..but changes on a micro scale altered that logic. Not having a go at you over it as making 100% accurate weather predictions in nigh on impossible.

Sometimes the drivers can fail due to other little nuisances rearing there heads...bit they do remain a solid pointer to where we may be heading weeks down the line..But some need to keep in mind that MJO moving into phase 7/8 will not guarantee a cold and blocked outcome...a strong PV in the wrong place can rule this out as we've seen many times before. And kee in mind if the teleconnections are barking up the wrong tree,then NWP is most likely going to be barking up the wrong tree also.

But yeh they are a very important tool and perhaps the few that decide to dismiss them purely refuse too learn by them...or really understand them.

This is my point also its for the broader scale of Northern hemisphere and won't pick up micro scale blocking the Atlantic could become active which is very likely but the vortex is weak and so is the jet stream plus running south throw up a small ridge north of us and we end up on cold side of the jet prolong the cold spell.

Edited November 29, 2023 by booferking

[minus10]

Yes...looking for those reds to intensify as per gfs6z fi....

 

 

[Tamara]

29 minutes ago, Met4Cast said:

Looks like my expectation for an unsettled start to December is going to come to fruition after all, just with a bonus cold spell before hand. 

Quite a few turn their noses up at background drivers/teleconnections in this thread, I suspect due to a lack of understanding them but I think that’s a shame, they are an incredibly useful tool and add a lot of context to NWP outputs. 

 

The MJO continues it’s progression eastwards is a rather amplified state, this wave has been a little faster than modelled and is expected to reach the central Pacific sometime around mid December, meanwhile we should see overall GLAAM rising via frictional & mountain torque processes thanks to this MJO wave with WWB’s returning. 

i.e I don’t expect we’ll see an Atlantic onslaught for weeks on end, it’s very possible we see a switch to more blocked/colder conditions over the Christmas period > into early January. 

As you might expect, I agree completely with the sentiments you make. Irrespective of my own weather preferences, the diagnostic processes are simply used to try to identify the most likely pattern probabilities. It is self defeating to to try to fit the data provided to a desired outcome though that will inevitably conflict in a thread like this which is heavily skewed in the peak seasons of summer, and most particularly winter, to a definitive weather type.

As per recent posts, I would only add to your analysis that considerable doubts continue about the return of the upstream momentum in respect of distribution into the sub tropical jet & how much energy, possibly, finds its way under the cold blocking over NE Europe. Across all main models in NWP there are a plethora of different solutions, some of which try to undercut the blocking.

For my own locality in Portugal, the watch is for a possible atmospheric river situation from midweek next week as warm moist sub tropical air arrives as part of the upstream momentum heading downstream. There is a lot of doubt about how the boundary of this returning tropical maritime airmass interplays with polar air at latitudes further north in Europe and high impact weather event potential clearly exists.

The situation is a little more nuanced than the return of the MJO into the Pacific. The existing complex inertia differential between the polar field and the mid latitudes here in the Atlantic & Europe is set to create some roadblocks a little before then. The question is where, and what then happens afterwards as jet eddies propagate through the extra tropics and poleward to a polar vortex which has already started its traditional seasonal stay in a weakened state.

[Catacol]

1 hour ago, Met4Cast said:

Looks like my expectation for an unsettled start to December is going to come to fruition after all, just with a bonus cold spell before hand. 

Quite a few turn their noses up at background drivers/teleconnections in this thread, I suspect due to a lack of understanding them but I think that’s a shame, they are an incredibly useful tool and add a lot of context to NWP outputs. 

 

The MJO continues it’s progression eastwards is a rather amplified state, this wave has been a little faster than modelled and is expected to reach the central Pacific sometime around mid December, meanwhile we should see overall GLAAM rising via frictional & mountain torque processes thanks to this MJO wave with WWB’s returning. 

i.e I don’t expect we’ll see an Atlantic onslaught for weeks on end, it’s very possible we see a switch to more blocked/colder conditions over the Christmas period > into early January. 

and for this reason 2 points to make:

1. Enjoy what is here now. It will last about a week in total, bring frost and blue skies at times (glorious here today! - though I'm stuck indoors  ) and is a great start to the season.

2. This spell arrived because of an MJO passage through 7/8/1 on the back of a rising AAM context and a canadian warming helped along by a Nino-style north pacific low in place. It has probably been helped by atlantic SSTs. Those same drivers have faded as AAM has fallen, MJO gone back into 2/3/4 and - hey presto - the pattern flattens a bit. These patterns are not created by "shortwaves" south of Greenland or spoilers in the North Sea. They are driven by large scale developments that originate in the Pacific. And just as the pattern arrived and now is set to decline in response to those drivers, a blocking pattern is likely to reemerge in the second half of the month (or perhaps final third) as those drivers switch back to a more favourable combination. This is the waxing and waning of a pattern that is standard stuff.

I probably won't post again for a week or so as I am not expecting to see anything change all that much. But by the end of next week, once the cold has faded and we are all wondering what happens next, I think we might see some good runs start to appear in the outer edges of NWP. Chase II will be on! My head will come back up.

Final thoughts. I note that there is still a NW/SE slant to the jet projected next week. The trough that will gather over us will be a fairly cold one as residual blocking hangs on over Greenland. So - wetter and average but not often mild. And I think the cold over Scandy will hold. Assuming this happens, we will have an excellent context for the next round of amplification. 3 weeks further into the season, more entrenched cold to tap into. And this is before we start to consider the state of the Strat Vortex - signs continue to emerge that the pressure on it will create a slowdown, maybe a significant slow down, and that would be another great context looking further into Jan and Feb.

If folk want to continue to scan charts every day while the next 7-10 days plays out, go find those charts that show the state of the Pacific and watch out for a high amplitude MJO wave. On that - all hail the mighty Australian Met. Their BOMM model remains staunch in the belief that the next wave is going to be a strong one (other models currently less certain....)

[Bricriu]

1 hour ago, Met4Cast said:

Looks like my expectation for an unsettled start to December is going to come to fruition after all, just with a bonus cold spell before hand. 

Quite a few turn their noses up at background drivers/teleconnections in this thread, I suspect due to a lack of understanding them but I think that’s a shame, they are an incredibly useful tool and add a lot of context to NWP outputs. 

 

The MJO continues it’s progression eastwards is a rather amplified state, this wave has been a little faster than modelled and is expected to reach the central Pacific sometime around mid December, meanwhile we should see overall GLAAM rising via frictional & mountain torque processes thanks to this MJO wave with WWB’s returning. 

i.e I don’t expect we’ll see an Atlantic onslaught for weeks on end, it’s very possible we see a switch to more blocked/colder conditions over the Christmas period > into early January. 

Just a thought on this, given background drivers are always in a state of flux, it would seem that on very rare occasions  the background signals can be overridden. Look at the winter of 1962/63, I presume the MJO and AAM weren't  conducive to blocking through that extremely long lasting  spell,but the intense blocking must have overriden them. Perhaps if we had an omega block this time with the cold well entrenched the same thing might have happened this time. I take your point though that they generally have a huge bearing on what type of weather we are likely to have .

[Blessed Weather]

30 minutes ago, Bricriu said:

Just a thought on this, given background drivers are always in a state of flux, it would seem that on very rare occasions  the background signals can be overridden. Look at the winter of 1962/63, I presume the MJO and AAM weren't  conducive to blocking through that extremely long lasting  spell,but the intense blocking must have overriden them. Perhaps if we had an omega block this time with the cold well entrenched the same thing might have happened this time. I take your point though that they generally have a huge bearing on what type of weather we are likely to have .

A Canadian Warming of the stratosphere in January and February 1963 played a big part in making that winter very special. Such warmings don't always have such an impact (some have very little impact) but this type of warming puts pressure on the SPV and can weaken, displace and lead to a full blown SSW.

Source: The Mid-Winter 1963 Stratospheric Warming and Circulation Change

The current warming expected to rumble on for a couple of weeks yet; here's the geopotential height and temperature anomaly at T384 14th Dec from this morning's GFS 06z.