Model Output Discussion - Christmas week and beyond

[Bricriu]

12 minutes ago, blizzard81 said:

No chance. I'm personally loving this. Very complex and intruiging. Compulsive model viewing and the enjoyment is so much more when we have this fab forum to share and discuss it all. 

Not sure if that's good news or bad news lol. I really don't rate that model. 

It's a fantastic model. Just for tonight it is verifying better than all other models. Watch all the other models fall in line with it tomorrow:) if only!

[blizzard81]

10 minutes ago, Don said:

As I said in the run up to the cold spell, when the outlook is looking poor, it improves if I take a break from model watching, so see ya later!! 

That's extreme superstition

[Don]

2 minutes ago, blizzard81 said:

That's extreme superstition

It is but I'm willing to give it a go!! 

[blizzard81]

1 minute ago, Don said:

It is but I'm willing to give it a go!! 

I take my hat off to ya!

[snowbob]

1 hour ago, BLAST FROM THE PAST said:

If anyone thinks the 18z is not good for cold….take your Xmas day snow/cold glasses off and see what ‘might’ be coming……I think it is

 

BFTP

 

 

Probably a stupid question

but if the p.v is that far away ie over Russia 

surely eventually that has to work it’s way back this way and hopefully develop a stinking easterly for the U.K. 

or am I miles off

Edited December 19, 2022 by snowbob

[alexisj9]

44 minutes ago, booferking said:

Gfs slowing losing heights run by run early on this time tomorrow it will be inline with rest of models, just can't  be trusted the mean trending the wrong way also.

Welcome to the clown   show all will be revealed tomorrow in the next episode of gfs the calamity.

The second frame doesn't make sense, more plausible would be the highs joining, with the low sw. I mean, the low at that stage had already stalled and moved Sw, how does it suddenly wake up and move through the highs 

Edited December 19, 2022 by alexisj9

[Rain All Night]

EC46 alongside the GEFS and CFS to look for cross-model agreement. Not difficult to begin with of course. We can expect a mild week for the south, and a chillier week for the north.

Week two maybe chilly for all if we get the favoured ridge to our west.

Perhaps goodbye Euro heights from week three, just don't tell the CFS? Scandi high options starting to proliferate from here on.

Ridges in other interesting locations also available... EPS control run in a cluster with low heights over Europe...

Now what is this... seems like quite a few signals in common at such a distant timeframe?!

CFS not wholly disagreeing with that high latitude blocking signal still present by week 6, not willing to cooperate on those low heights over Europe though.

Scandi high members the most common through much of the run:

I hope I've done an alright job with this!

Edited December 20, 2022 by RainAllNight

[Woldsedge]

Just look how quickly a north sound battleground set up in 1978. Christmas was wet and mild but gradually day by day the cold nudged south ending up with a channel low and a classic snowstorm across the southern half of the UK. Frigid air as well. Similarities to the set up we have at the moment perhaps?

[Rain All Night]

7 minutes ago, Louthweather said:

Just look how quickly a north sound battleground set up in 1978. Christmas was wet and mild but gradually day by day the cold nudged south ending up with a channel low and a classic snowstorm across the southern half of the UK. Frigid air as well. Similarities to the set up we have at the moment perhaps?

FullSizeRender.MOV

Is it just me or is the colder air pushing south there even without the surface flow moving in that direction..?

[Woldsedge]

4 minutes ago, RainAllNight said:

Is it just me or is the colder air pushing south there even without the surface flow moving in that direction..?

Yes. It was a long and slow process over many days and the forecasters didn’t know which way it was going to go re mild or bitter. Slowly the cold gradually nudged south. 

[LetItSnow!]

1 hour ago, MJB said:

Massive potential and can't grumble with these surely?

 

The great thing about that would be the vortex piling to our northeast which could lock things in... if it occured. There's no forcing over America whatsoever. Needs some tweaks but the Xmas/NY period looks very interesting! Screw Christmas when longer term cold could be at hand.

[Allseasons-Si]

Just to put this up quickly as it's getting late...

i don't think this Architect knows where to put the front door,...north or south?

i mean,...predict the next seven days if you can,...good luck

I'd say the north favours more snow than the south at the moment but i could not call what is going to happen in the xmas week.

so more...

...NEEDED.

[Eagle Eye]

Seeing as this thread's quiet now (and I have definitely not been writing this for 3 hours, talking to Olivia and all that, distractions you know)...

The Atmospheric River(AR) event that takes place across the North Atlantic over the next few days looks to happen I'm two phases (or may two separate AR's). First of note is the first wave rapidly approaching Iberia associated with that long elongation of water transport that moves up and dumps Iberia with a lot of precipitation. It's the back of these that are of note to me though because they are relatively cool and moist compared to the first part of the AR (although that still has the moisture) and as I like to call it now, the loopback feed if timed right can mix in with the colder air coming down from the North(ish) as well and bring potentially a lot of snow to Northern and Scottish areas. Potentially further south depending on how the loopback eventually evolves. Beyond that wee that second wave forming through the mid Atlantic feed and we can see that on the precipitation totals fairly strong just off the coast of Florida and we may want to see how that evolves as well.

I think it's pretty clear that the Eastern wandering divergent velocity means that from the initial stages and the fact that it seems to be moving quite quickly, the MJO looks to be more progressive and maybe amplified than previously forecasts (like I thought it would, not to brag just a lucky guess)from a few days ago. Suggesting better timing with phase 5/6/7 going into January so we may some renewed downstream blocking around Greenland or Scandinavia depending on how the wave train evolves. Hence the whole EC46keeping the -VE AO pattern in hold. It's a possibility before I think the pattern should collapse by mid January but it depends on how we see the AAM and MJO eventually evolve what happens before that. We may never see the unstable inertia pattern collapse of course but I just find that highly unlikely.

The MJO follows on from the VP and is slightly better than the previous runs although it's still only phase 4 that we see as the most amplified. A good trend emerging to amplify phases 4-6/7 further on the forecasts (especially 5,6 and 7) but I think we still want that little extra kick. It's a good background signal to have and better than phases 2 and 3. Phases 6 and 7 having higher support of a -VE NAO in composites and all that stuff.

It's clear that the zonal wind has recovered and is going to recover further over the area of 180-120W and so the East Asian Jet Extension (EAJE) is fully into place with a possible energy scattering event that may help us or hinder us down the line. This may see a more zonal favoured longer-term or it could also distribute energy and work with the MJO to form another blocking going into January week 1/2 timeframe as my MJO notes also said, certainly interesting long-term and not just a definite zonal forecast. It could also set up a mid-term Californian AR which doesn't have much effects downstream in my experience but I haven't experienced many knowingly to be fair.

The upper troposphere meridional wind also supporting that shorter term Greenland blocking potential (45W) considering the weaker zonal wind but until it actually comes to pass we can't count out the fact that the other models may be correct in that it doesn't form quite so quickly/quite so well so we'll just have to see what happens with this.

Onto the GWO and it's clearly not as amplified into a +VE state than most of November but looking at the forecast there might be a slight rebound associated with a +VE mountain torque over the coming days and if they are more amplified than the GFS forecasts we may see a return to a slight +VE state compared to the slight -VE state we seem to be in right now. At this amplification it doesn't really matter though and instead other background signals look to be the main forecasting tools going forward. Clearly the ocean-atmospheric connect still not properly showing itself and so the MJO is likely to have a fairly large effect so be on the lookout for phases 6 and 7 especially until the AAM becomes amplified either way. Then continue to look for those phases still but with varying degrees of desperation for those phases .

So what do some of these words and phrases actually mean:

I've picked out a few with some of my or others explanations from before

My explanations:

"

Unstable inertia - Inertia is when it keeps it's existing state unless acted upon by another object. Hence unstable inertia is the transfer of energy is between it's existing state and the 'disturbance'.

This is a very basic view at both though and unstable inertia involves a lot more than that.

-VE just means negative (hence, +VE means positive)

Some basics on Atmospheric Angular Momentum (AAM)

A few shortened words as well:

AMB - Angular Momentum Budget  

AAM - Atmospheric Angular Momentum 

MT(mountain torque) 

GWT(gravity wave torque) 

FT(frictional torque) 

If AMB increases in the atmosphere it must have been transferred from another source since AMB is always conserved. The sources for AMB are from the Earth, the Oceans and the Atmosphere. 

One major aspect in affecting AAM are torques. A torque is the rotational force in the atmosphere.  

The 3 main torques affecting the atmosphere are: 

Mountain torque (MT) - The turning force applied with the effect of pressure systems on mountains. 

Frictional torque (FT) - Boundary layer dynamics. 

Gravity wave torque (GWT) - Subgrid (local) torque, upward movement and downward movement to do with the buoyancy. 

If there is a net westerly surface wind, the atmosphere speeds up the Earth's rotation and transfers angular momentum to the earth and so there is a net decrease in AAM. The reverse happens with a net easterly wind

Global MT anomalies are constructed by sypnotic waves that scatter energy across Asia and North America. These sypnotic waves trap the SLP anomaly and push them towards the south. Driven south and east of mountains. Sypnotic wave centres amplify aloft.

"

 

Away from my definitions now

 

Madden-Julian Oscillation (MJO) (Met Office) - 

"The Madden-Julian Oscillation is characterised by an eastward spread of large regions of enhanced and suppressed tropical rainfall, mainly observed over the Indian and Pacific Ocean."

 

MJO phases (Met Office) -

"When the MJO is in its active phase over Indonesia and the West Pacific, it tends to drive a negative North Atlantic Oscillation (NAO) 2 to 3 weeks later.

A positive NAO index tends to be preceded by phase 3 and 4 of the MJO, which brings milder and wetter weather across the UK.

A negative NAO index tends to be preceded by phase 6 and 7, which influences a ‘blocked’ weather pattern and is often associated with colder and drier weather across the UK.

The timescale of the MJO having an influence on North Atlantic weather regimes is usually 10 to 12 days."

 

North Atlantic Oscillation (NAO) (Met Office) - 

"Positive NAO phase -

Winds from the west dominate, bringing with them warm air, while the position of the jet stream enables stronger and more frequent storms to travel across the Atlantic

Negative NAO phase -

Winds from the east and north-east are more frequent, bringing with them cold air, while the adjusted position of the jet stream leads to weaker and less frequent storms."

 

Artic Oscillation(AO) (Climate Prediction Centre) -

"The daily AO index is constructed by projecting the daily (00Z) 1000mb height anomalies poleward of 20°N onto the loading pattern of the AO. "

The loading pattern is just the normal pattern for the time of year to put it basically.

 

Atmospheric River (I say AR) (NOAA) -

"Atmospheric rivers are relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics. These columns of vapor move with the weather, carrying an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. When the atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow."

 

Global Wind Oscillation (GWO) (a NOAA paper on it by Klaus Weickmann and Edward Berry) - https://psl.noaa.gov/map/clim/wb08_final.pdf

 

Anyway, back to my thoughts for the future...

So pretty much my thoughts for now are that it's a possibility that's on the cards that we could see a fairly substantial Greenland blocking going into later this week and onwards associated with some sort of zonal wave train but beyond that there is so much more difference. This one should bring cold somewhere in Great Britain even if the Greenland blocking doesn't form and if it does it could connect up with an Atmospheric River to dump a lot of snowfall somewhere depending on the timing I think eventually we could see another renewed Greenland blocking as long as we keep the pattern away from a large zonal state (which I think would have to mainly be powered by the AAM dipping quite deeply -VE after connecting with the La Nina base state) sometime in early(ish) January.

So a fair few cold chances long-term and mid term I would think and compared to recent years we take that. There needs be some caution not thrown into the wind as we simply don't really know how energy scattering events will happen in the future if their related torque events haven't happened yet and so wave trains that bring us into a zonal pattern cannot be ruled out. As well as that the -VE NAO isn't a guarantee of cold to be long lasting and it could be west based as a basic example.

The EAJE could also connect up with the PNA(Pacific/North American Pattern, another pattern that doesn't directly affect us but I think it's an alright indicator of possible colder air when it's amplified away from neutral but it depends on the pattern) and sort of hijack our weather as well, I think it's a possibility that over time if it keeps being over extended we could see it's downstream effects 'phase out' the Atlantic -VE zonal repeating pattern. Though it can still interact with the MJO fairly well in my opinion to just about distribute the energy right as long as timing is done well which seems to be getting better run by run with a more progressive and amplified MJO phase 6/7 pattern possibly taking effect.

The thermal Eddy's 'retracting' due to the loss of AAM doesn't seem to have happened as quickly as I had initially thought a week or so ago (possibly longer). This is shown in a propped up -VE AO phase and so supports the fact that a loss of AAM does not necessarily mean that northern blocking has to go if you can hold the Eddy's in place with little events and if the loss of AAM is fairly minimal then the 'retreat' does not really seem to happen. This has sort of helped my mind thinking things through as to my post this fine morning. We could see these Eddy's 'retract' quite quickly but I don't see much sign of that unless a quick Strat-Trop downwards connecting forcing the Trop to go largely zonal but I think the models initially over-did that and now are trying to bring it back down. As seen by the connect only slightly adding to the +VE zonal forcing on the Troposphere compared to what I've seen on previous runs. This sort of "Saving" us potentially, for now though.

Edited December 20, 2022 by Eagle Eye

[Ali1977]

Everything is a little further east up to T84 , the storm in the USA, the WAA up into Greenland and the northerly towards the U.K. Hoping this is a good thing

The cold seems to be coming for the U.K. quicker that’s for sure. 

Edited December 20, 2022 by Ali1977

[Ali1977]

3 minutes ago, Ali1977 said:

Everything is a little further east up to T84 , the storm in the USA, the WAA up into Greenland and the northerly towards the U.K. Hoping this is a good thing

The cold seems to be coming for the U.K. quicker that’s for sure. 

T108, northerly on Xmas eve 

Edited December 20, 2022 by Ali1977

[Ali1977]

Ahh, UKMO still vastly diff at T120 Greeny heights so different at such short time frame 

[Kasim Awan]

1 minute ago, Ali1977 said:

Ahh, UKMO still vastly diff at T120 Greeny heights so different at such short time frame 

Big improvement this morning Allison.

[Battleground Snow]

2 minutes ago, Ali1977 said:

Ahh, UKMO still vastly diff at T120 Greeny heights so different at such short time frame 

Still a huge improvement at 144, good start today!

Edited December 20, 2022 by Battleground Snow

[Ali1977]

2 minutes ago, Kasim Awan said:

Big improvement this morning Allison.

It’s Alistair but I’ll take this for Xmas day

 

Better looking UKMO and the Greeny heights are better at T144 which could come in handy later on 

Edited December 20, 2022 by Ali1977

[Kasim Awan]

17 minutes ago, Ali1977 said:

It’s Alistair but I’ll take this for Xmas day

UKMO and ICON definitely shifted in the right direction too

Definite December 2020 vibes

Edited December 20, 2022 by Kasim Awan

[Ali1977]

Back to sleep I think, the GEM and GFS don’t really scream merry Xmas to me this morning!! Possibly the GFS might be better towards new year but no support on the Greeny high this morning neither 

[Georgina]

14 minutes ago, Ali1977 said:

It’s Alistair but I’ll take this for Xmas day

Morning Allison 

do you have a link to these charts please ? 
 

 

Edited December 20, 2022 by Georgina

[Kasim Awan]

1 minute ago, Georgina said:

Morning Allison 

do you have a link to these charts please ? 
 

 

Think shes gone offline - heres a link

WWW.METEOCIEL.FR

---

Météociel propose le modèle GFS à maille moyenne (0.25 degrés) jusqu'à 240h. Cartes de prévision des précipitations, des orages, de la neige, du vent, des températures à tous les...

 

Edited December 20, 2022 by Kasim Awan

[Mucka]

 

GEM looking like yesterdays GFS in FI synoptic, shame the GFS 00z doesn't repeat the cold but an Icelandic shortwave spoiler does for it which might not be there next run

GFS may well get there in the end but making a real meal of it. French accent, "Three days later..."

shortwave hell, it never ends.

 

Then again set up one of these trains running into cold air and we get a snow fest. (yeah I know) 

Still an outside chance of snow on Xmas day but otherwise little cold about in the run up to the New Year on this mornings output.

Beyond that we will have to hope GFS and now GEM are on to something with retaining some Atlantic heights and forming an Iceland/Greenland high but UKMO doesn't look like it is interested. (Yet)

That looks like our last shot at cold this year.

Edited December 20, 2022 by Mucka

[That ECM]

T138 gefs.