Model Output Discussion - New Year and Beyond

[bluearmy]

06z eps tend to slightly stronger block and slightly more push se of the jet ……..………..

and the gfs 06z finally manages to reverse strat flow at the top axross the pole - displaced 

Edited January 1, 2023 by bluearmy

[minus10]

11 minutes ago, northwestsnow said:

 

Horrid 06 GEFS.

 

...fair enough...certainly in the reliable not good and also lot of spread in fi but just noticed op and control getting cooler in last third or run...no ?

 

 

 

[BlueHedgehog074]

1 hour ago, mushymanrob said:

Id suggest that Polar Maritime incursions are likely to increase after next weekend as the mean upper trough drifts to our Northeast. And note the 528 DAM contour touches Northern Scotland throughout these runs, a Northwesterly between systems would see that extend further South at times.   To me, this smacks of early 1984 when a run of PM air produced a lot of temporary snow from showers mainly for the North and West. Some very large accumulations over parts of the northwest were realised. Overall, these charts to me suggest a very mobile, unsettled spell becoming colder unsettled.
 

I see where you’re coming from mushy - the upper flow on that 8 to 14 day chart for the UK turning more from the North-West direction, which does give the impression of increasing influence of chillier conditions from Polar Maritime flows. So certainly a chance for a more wintry flavour to the weather, especially for North and Western parts. 

Admittedly, I probably wouldn’t have paid much attention to the fact that the 528 Dam contour line sat close/over the Northern part of Scotland on the runs. Have to bear something like that in mind next time when looking at the charts.

Edited January 1, 2023 by DiagonalRedLine
Corrections

[Catacol]

HNY everyone - festive season pretty much over...time to return to "normal" (whatever that is...) 

It has been a grim 2 weeks for cold hunters. I have checked into a few charts and data sources over the Xmas period and frankly if it could go wrong - it has gone wrong. Pacific forcing arrived as expected and it has prevented the slide towards a Nina dominated atmosphere. AAM has pushed back up into positive territory

and the GWO orbit started to rise once again, avoiding a slide into flat, Nina territory.

We have even ended up in the fabled ground of MJO phase 7 as many suspected might happen despite the usual crappy MJO model forecasts.

This was probably about as big a jump back up of AAM in a positive pacific context as we could expect. Looks pretty good! We are even looking at a scenario which sees the North Pacific High replaced by some quite long last low pressure....a good precursor for strat forcing

But just take a look - as though we need to - at pressure over Europe. I posted JMA monthly charts that saw this draining away. EC charts showed it draining away. And here we are with the Euro High firmly embedded. It has forced the jet stream further north so that only the Highlands are now seeing what - at one stage - some of us thought much of the UK could see during this current period. Go to the outer reaches of useful EPS modelling and not much change. Euro High in charge. 

It is indeed grim. CC modelling of global patterns over the next 80 years or so sees the growth of the Euro High as a core feature. The fact that we are seeing it so much already, as early as 2022/23, is depressing. Germany breaking temperature records....we had our 40 degree summer just gone. Both courtesy of this growing anomaly. As the world warms the regional implications of this Euro feature are going to become quite profound I suspect.

Where does this leave UK winter? Searching for a SSW. I don't see any way out of a westerly pattern now without a SSW. Really substantial amplification might possibly do it but remembering the failure of the GP +4SD "torpedo" years ago I am not sure modern climate patterns produce the same kind of response as was the case 30-40 years ago, at least in Europe where we have a semi permanent high anomaly bedded in to our south.

A proper SSW - like 2018 - would do it. In such circumstances downwelling impacts of vortex collapse overcome tropospheric forcing and these scenarios are the ones that really significant winter cold will rely on going forward. To have any chance of this in our current winter we could do with seeing high pressure reemerge over Scandy or the Urals as we had in November to pair up with low pressure over the Aleutians which is modelled. As more than one poster noted a month ago - it would have been much better for our winter overall if the Scandy High in early December hadn't retrogressed so swiftly to Greenland. Much better for stratospheric forcing. Right now only half of this pairing is in place - the Aleutian Low. It is forecast to produce quite a significant wave 1 stretch of the vortex and there is a chance going forward of a displacement warming....but a wave 2 split would be much better for us. Note the current 3D modelling of the vortex in 10 days' time - stretch is quite clear and visible.

So - forget the first half of January. I would almost suggest everyone take a week away from the models, maybe even 10 days, and come back and see if any change is in the offing. Pray that the Euro High ridges towards the Urals in the meantime.

Edited January 1, 2023 by Catacol

[Catacol]

One little extra post. An area I am trying to improve my understanding is in regards to East Asian Mountain Torque events. In very blunt laymen's terms these occur when vertical wave activity is produced from warm air bouncing off the Himalayas and spearing up into the stratosphere. These ideally need to force that warmth more in a polar direction rather than towards the Equator. I get a bit vague as to the tropospheric shape of patterns to induce polar rather than equatorial wave flux so have to lean on the flux models for this. At the same time the action of the high pressure sweeping across the mountains acts to slow down the rotation of the earth ever so slightly and produce a consequent increase in atmospheric momentum. This is what a "spike" in AAM created by mountain torque means.

These +EAMT events happen when a high pressure cell sweeps across the Himalayas in a NW to SE direction. Not only does this increase wave flux but it also provides a significant boost to the Pacific jet - sometimes posted by Met experts in the form of a "jet extension" in the pacific. This extension is a factor that produces another round of pacific driven amplified wave activity downstream, certainly to the US but hopefully also through to the Atlantic sector (at least until the Euro High puts up the wall!)

ECM modelling of Asia is interesting today. Note the strong high pressure to the NW with a fairly deep trough sinking down the eastern flank

Roll that on a few days and the high pressure has moved ESE, interacting with the mountains.

By Saturday it has passed mostly to the East.

Now - lots of caveats to this, not least the open admission that this is very much an amateur understanding of something that is undoubtedly complex. But if people are looking at straws to clutch away from longer term impacts of an SSW then I would suggest the second half of January might see the reignition of an amplified pattern that might - might - do something to try and shift that Euro anomaly.  

Edited January 1, 2023 by Catacol

[Rain All Night]

34 minutes ago, Catacol said:

HNY everyone - festive season pretty much over...time to return to "normal" (whatever that is...) 

It has been a grim 2 weeks for cold hunters. I have checked into a few charts and data sources over the Xmas period and frankly if it could go wrong - it has gone wrong. Pacific forcing arrived as expected and it has prevented the slide towards a Nina dominated atmosphere. AAM has pushed back up into positive territory

and the GWO orbit started to rise once again, avoiding a slide into flat, Nina territory.

We have even ended up in the fabled ground of MJO phase 7 as many suspected might happen despite the usual crappy MJO model forecasts.

This was probably about as big a jump back up of AAM in a positive pacific context as we could expect. Looks pretty good! We are even looking at a scenario which sees the North Pacific High replaced by some quite long last low pressure....a good precursor for strat forcing

But just take a look - as though we need to - at pressure over Europe. I posted JMA monthly charts that saw this draining away. EC charts showed it draining away. And here we are with the Euro High firmly embedded. It has forced the jet stream further north so that only the Highlands are now seeing what - at one stage - some of us thought much of the UK could see during this current period. Go to the outer reaches of useful EPS modelling and not much change. Euro High in charge. 

It is indeed grim. CC modelling of global patterns over the next 80 years or so sees the growth of the Euro High as a core feature. The fact that we are seeing it so much already, as early as 2022/23, is depressing. Germany breaking temperature records....we had our 40 degree summer just gone. Both courtesy of this growing anomaly. As the world warms the regional implications of this Euro feature are going to become quite profound I suspect.

Where does this leave UK winter? Searching for a SSW. I don't see any way out of a westerly pattern now without a SSW. Really substantial amplification might possibly do it but remembering the failure of the GP +4SD "torpedo" years ago I am not sure modern climate patterns produce the same kind of response as was the case 30-40 years ago, at least in Europe where we have a semi permanent high anomaly bedded in to our south.

A proper SSW - like 2018 - would do it. In such circumstances downwelling impacts of vortex collapse overcome tropospheric forcing and these scenarios are the ones that really significant winter cold will rely on going forward. To have any chance of this in our current winter we could do with seeing high pressure reemerge over Scandy or the Urals as we had in November to pair up with low pressure over the Aleutians which is modelled. As more than one poster noted a month ago - it would have been much better for our winter overall if the Scandy High in early December hadn't retrogressed so swiftly to Greenland. Much better for stratospheric forcing. Right now only half of this pairing is in place - the Aleutian Low. It is forecast to produce quite a significant wave 1 stretch of the vortex and there is a chance going forward of a displacement warming....but a wave 2 split would be much better for us. Note the current 3D modelling of the vortex in 10 days' time - stretch is quite clear and visible.

So - forget the first half of January. I would almost suggest everyone take a week away from the models, maybe even 10 days, and come back and see if any change is in the offing. Pray that the Euro High ridges towards the Urals in the meantime.

What is meant by "wave 1" and "wave 2"? I've seen Eagle Eye mention these frequently also

[nick sussex]

The ICON seems just as unreliable as the GFS at the moment given its wild swings .

The latest run is a world away from the 00 hrs .

[Gowon]

3 minutes ago, nick sussex said:

The ICON seems just as unreliable as the GFS at the moment given its wild swings .

The latest run is a world away from the 00 hrs .

Yeah, I think it's that little shortwave near Norway which stops us going cold 

[nick sussex]

1 minute ago, Gowon said:

Yeah, I think it's that little shortwave near Norway which stops us going cold 

Yes it’s a real mess to the north of the UK and the models seem to be unsure as to when and where that phases with the upstream trough .

The ECM absorbs that shortwave but the Scandi high is just too weak given it’s just a surface feature and lacks the punch of a proper high to force more trough disruption.

[Frosty.]

Happy New Year all..just looked at the GEFS 6z and I gorra say there’s a fair modicum.. ..of cold zonal potential in there!..of course I would love / adore a raging Easterly…but at least some cold would be better than constant mild mush ?…am I right.. or ….. hey at least bungle agrees!    

Edited January 1, 2023 by Frosty.

[Don]

2 minutes ago, Frosty. said:

Happy New Year all..just looked at the GEFS 6z and I gorra say there’s a fair modicum.. ..of cold zonal potential in there!..of course I would love / adore a raging Easterly…but at least some cold would be better than constant mild mush ?…am I right.. or ….. hey at least bungle agrees!    

Yes if cold zonal comes off?!!

[nick sussex]

Regardless of some early differences between the GFS,GEM and UKMO it looks pretty clear that the Scandi high is boxing in the wrong division .

Against a weaker attack it might have stood a chance but gets its marching orders pretty quick .

 

[Guest]

Well, having just received an energy bill of £800 for December which has almost given me heart failure, it's probably a good thing that the Atlantic looks like it will stop the cold block to the east, but it's close at one point at 126hrs on the GFS.  Models do seem in good agreement though that the Atlantic will retain its influence over our part of the world moving forwards.

[Don]

7 minutes ago, nick sussex said:

Regardless of some early differences between the GFS,GEM and UKMO it looks pretty clear that the Scandi high is boxing in the wrong division .

Against a weaker attack it might have stood a chance but gets its marching orders pretty quick .

 

Wasn't a Scandi high always very much an outside chance influencing the UK though?

[Catacol]

1 hour ago, RainAllNight said:

What is meant by "wave 1" and "wave 2"? I've seen Eagle Eye mention these frequently also

Wave 1 = a single pocket of warmth pressing on the vortex from 1 side. Wave 2 = 2 pockets of warmth acting on the vortex at the same time from different sides of the vortex. Think of an air balloon pinched between your fingers.

Generally a wave 2 warming that causes a vortex reversal is the most destructive and - as in 2018 - can have the most dramatic tropospheric impacts. A wave 1 reversal can essentially be a displacement that pushes the vortex off its perch but often the direction of this displacement pushes it over towards Greenland. Wave 1 SSW therefore probably less attractive in general for the UK.

The 2018 wave 2 destruction of the vortex is a great one to study. The precursor pattern in the troposphere was very evident in mid January. 4 week lag to the warning and then those amazing tropospheric charts as the impact downwelled which produced a reverse flow all the way from Siberia to Canada. Extraordinary. For several weeks the most exciting weather watching of my life, the only negative being that it happened 3-4 weeks too late in the season.

Edited January 1, 2023 by Catacol

[nick sussex]

1 minute ago, Don said:

Wasn't a Scandi high always very much an outside chance influencing the UK though?

An outside chance especially as it’s a faux high .

Remember all the debate about faux cold with those inversion scenarios well here we have just a surface feature .

You might  get away with those when you’re not dealing with such a strong push of low pressure fueled by the deep vorticity dropping south from Greenland .

A separate shortwave ejected se and separated from that vorticity wouldn’t have packed such a punch .

Frustrating to see all that deep cold parked to the ne but plus ca change ! 

This is  Ripley , last survivor of the Nostromo,  signing off !

Time to worry when I start wheeling out the film references! 

 

[nick sussex]

This is Ripley signing back in !

The post day ten GFS looks a pretty standard response to the MJO moving into the more favourable phases .

The limpet Euro slug tends to get pulled west and north .

If the PV displaces towards Baffin in response to the strat warming routes to cold from there would generally come from the ne .

Edited January 1, 2023 by nick sussex

[knocker]

1 hour ago, RainAllNight said:

What is meant by "wave 1" and "wave 2"? I've seen Eagle Eye mention these frequently also

Evolution of Warming

During the prewarming stage an intense polar night jet stream with strong vertical wind shear will appear. At this time a blocking situation develops in the troposphere. There is amplification of wave numbers 1 and 2 occuring in the upper troposphere and lower stratosphere. There are two types (Type A and Type B) of wave amplification which takes place during the prewarming period. In Type A, intensification of wave number 2 occurs about 2 weeks prior to the onset of the major warming. This is closely followed by an increase in the amplitude of wave number 1 with a subsequent weakening of wave number 2. During this time, wave number 1 reaches a peak about 1 week prior to the warming. In Type B warming, wave number 1 maintains a large amplitude for a long period. Type A is the most frequently occurring type of stratospheric warming.

An important character of sudden warming is its downward propagation from 45 km into the lower stratosphere. This feature is not zonal in character, but hasnonzonal structure, with a planetary wave tilting westward with height. In the middle latitudes, warming in the stratosphere (40 km) is followed by cooling in the mesosphere (65 km). Simultaneously, the opposite occurs in low latitudes, with stratospheric cooling and mesospheric warming, but the magnitude of the changes in the lower latitudes is one order less compared to that noted in higher latitudes.

Source _ Stratosphere Troposphere Interactions.  K. Mohanakumar

Further to this

The numbers are the "wavenumber". This means that in a given belt of latitude, a wave with wavenumber 1 will have one peak and one trough around the entire world. This is called wave 1. Likewise, a wave with wavenumber 2 ("Wave 2") has two peaks and two troughs as you go around the globe within this latitude belt. And so on. As you can probably see, as you increase the wavenumber, you are cramming more waves in as you go around the world. So the distance between each peak and each trough gets less. This is another way of expressing the relationship between wavenumber and wavelength. Wavenumber is essentially the inverse of wavelength.

Edited January 1, 2023 by knocker

[MATTWOLVES 3]

You know what I think? The harder you chase something in life...the more elusive it becomes! So I think we should all keep with the model watching and the posting,but we should frankly not give a dam whether it comes off or not. Its nearly always the case that the least you want something to happen,the more likely it is too happen.

Do I detect the first signs of a scandy ridge? Look at the PV...Congratulations Misses Vortex its a STRETCH!

2023....COME ON LETS BE HAVING YA.

Whey hey...the iberian Heights have left the building.

Edited January 1, 2023 by MATTWOLVES

[Tim Bland]

Not a particularly cold one but it’s an easterly of sorts …

[ICE COLD]

Near enough a split on the gfs 12z . All in all not a bad FI . 

[Derecho]

12z nothing to write home about in our part of the world but the cold air I've been keen to see over Scandi can throw a surprise if it doesn't budge. P9 on the GFS shows a scenario where cold to our east starts having a serious influence on our part of the world.

Wishful thinking but we can hope.

[Eagle Eye]

Upper Stratosphere displacement towards Greenland vs far upper Stratosphere/near Stratopause level displacement towards the North Pacific.

A +60°C difference between the two levels over Europe
Vs
A -15°C drop over areas of the North Pacific.

Vs what it's apparently supposed to look like. (Just what came up when I searched it up) 

So according to the GFS (outdated run), looks like we'll get the biggest abnormal thermal transfer between 10hPa and 1hPa levels at the end of the second week of January but at this range it's still too far out to put numbers to it. Still looks to me like a Wave-1 displacement that doesn't reverse the strat just yet but as long as we can have the Baroclinic Tilt then transfer of heat will be abnormal and the displacement of the Strat should keep weakening it in bouts and the formation of a secondary Wave split may happen . Still a few members showing increasing Wave-2 strength at the end of the run so I'll continue to keep an eye on how this evolves.

P.S If you're interested in Wavenumbers and I mention them but don't explain them in my posts a lot, both @Catacol and @knocker made better explanations than I could ever make further up..

[Don]

1 hour ago, nick sussex said:

The limpet Euro slug tends to get pulled west and north .

That limpet Euro slug seems so stubborn and looks to be sign of things to come.  Yesterday the models were showing signs of it moving in the medium term, which increased the chances of some colder zonality at least?!

Edited January 1, 2023 by Don

[lassie23]

What we need is the introduction of another weather model