Model Output Discussion - Deeper into Autumn

[Methuselah]

Today's GEFS temperature ensembles... all aboard the Mist & Drizzle train? And, just look at all those maxes between 5 and 8C? You always know when you're on to a winner!

     

[bluearmy]

24 minutes ago, feb1991blizzard said:

@bluearmy run to run variance chart won't look too great on GEFS 6z to 12z - especially where we could do without - Iberia.

Yes feb we’ve lost some euro low heights later week 2 which means less caa which means less cold across nw europe - geps not nearly as far on the change but it has drifted less cold at that timescale. Hopefully just a blip and far enough away not to be overly concerned ..

[Kasim Awan]

1 minute ago, Notty said:

Where is @That ECM ? Hopefully we won’t be led up the garden path again . This ECM has support from the other models

He's being reincarnated 

[terrier]

And who remembers that ECM back in the day. Exciting but whatever you do guys and girls don’t tell your family.

[Notty]

1 minute ago, terrier said:

And who remembers that ECM back in the day. Exciting but whatever you do guys and girls don’t tell your family.

It is etched on my brain

[Kirkcaldy Weather]

 

1 hour ago, MattH said:

Getting a Scandinavian block to then retogress to Greenland is something that only dreams (or December 2010)

Ask and you shall receive Matt

Anyone else doing this for the ECM  

 

[Cheshire Freeze]

Note that by D10 there is pressure being exerted on the block by the strengthening TPV to the N of it...We need to make sure that we retain sufficient heights to the E of us so that the SPV can be further strained. We don't need the pattern collapsing SW too soon.

I suspect that's where the dodgier ensembles are coming from in FI

Edited November 24, 2022 by CreweCold

[KTtom]

Sod it! 

Gfs P30 384 chart... no issues with uppers here ...

 

 

Edited November 24, 2022 by KTtom

[Cold Winter Night]

3 minutes ago, bluearmy said:

Yes feb we’ve lost some euro low heights later week 2 which means less caa which means less cold across nw europe - geps not nearly as far on the change but it has drifted less cold at that timescale. Hopefully just a blip and far enough away not to be overly concerned ..

EC 12z at 168-240h would fit right in with that picture.

It looks fantastic on the chart, the Scandi High is massive, and it is situated at the right latitude. There is an Easterly flow from the continent, with colder T850's.
However, what is lacking, is those Low heights over Europe. No "draft horse" as we in Holland would call such a Low generating CAA, preferably over Iberia and Northern Italy.

[Cheshire Freeze]

Just now, KTtom said:

Sod it! 

Gfs P30 384 chart... no issuesnwith uppers here ...

 

 

That is holy grail territory-

You've got the Greenland HP AND blocking to the NE remaining in situ. Pretty much 62/63 territory.

[Decemberof2010]

I just have to post the Hemisphere view of p30. Totally bonkers. There’s a few decent others, but none as crazy as that one. 
 

[Iceman2606]

Coldies watching the weather models through this week like:

[John88B]

2 minutes ago, CreweCold said:

That is holy grail territory-

You've got the Greenland HP AND blocking to the NE remaining in situ. Pretty much 62/63 territory.

Quick question. Is that what is called an omega block?

[Cheshire Freeze]

Just now, John88B said:

Quick question. Is that what is called an omega block?

Yes, big block bookended by troughs

[mountsbaysnow]

Hi guys as a complete novice, but a long time follower... Are we in a better position than this time last year. 

 

[Bald Eagle]

1 minute ago, mountsbaysnow said:

Hi guys as a complete novice, but a long time follower... Are we in a better position than this time last year. 

 

Noone mentions last year 

[Polar Maritime]

Models are looking very promising indeed for cold wintry weather into December. With such a disturbed PV this early in the season it's something we haven't seen for a good 12 years or so... 

This isn't a ramp by the way

Edited November 24, 2022 by Polar Maritime

[mountsbaysnow]

1 minute ago, Bald Eagle said:

Noone mentions last year 

I hear you  

[That ECM]

8 minutes ago, mountsbaysnow said:

Hi guys as a complete novice, but a long time follower... Are we in a better position than this time last year. 

 

Hi, yes we are for sure. Lots of blocking potential whereas last year at this time there was none. Of course this is going into winter and not winter as whole. It’s an interesting start to the season for sure. You should ask output related questions it helps learning. Everything I have learnt has been through this awesome site.

Edited November 24, 2022 by That ECM

[tight isobar]

A worthy snapshot all on it own... winters coming people

[Frosty.]

I’m not a greedy coldie.. …I would very happily  settle for any of these GEFS 12z perturbations…especially P30! …isn’t it great that the majority (coldies)  on here apparently  have something to look forward to.. for a change?!

 

 

Edited November 24, 2022 by jon snow

[damianslaw]

ECM unlike GFS holding much firmer with the strength of heights building to the east, these fending off the atlantic more quickly and pulling in a cold pool of air by next weekend, sub 528 dam air, then sub 522 dam air, cold enough for wintry precipitation - but too far out to say whether any will be associated with the flow. The warm SST's North Sea may generate some instability.

GFS continues to do a roller coaster ride, its been all over the shop last 24 hrs, but importantly maintains strong heights to the east and a generally weak atlantic, a slower burner to colder, but that seems the eventual destination.

[Notty]

5 minutes ago, damianslaw said:

ECM unlike GFS holding much firmer with the strength of heights building to the east, these fending off the atlantic more quickly and pulling in a cold pool of air by next weekend, sub 528 dam air, then sub 522 dam air, cold enough for wintry precipitation - but too far out to say whether any will be associated with the flow. The warm SST's North Sea may generate some instability.

GFS continues to do a roller coaster ride, its been all over the shop last 24 hrs, but importantly maintains strong heights to the east and a generally weak atlantic, a slower burner to colder, but that seems the eventual destination.

I’m buckled up on that ride. Downhill to the GFS 18z or are we still climbing to the top . The only thing I want for Xmas is snow on Xmas Eve (never happened in my 60 years). Here’s hoping  

Edited November 24, 2022 by Notty
Spelling

[Eagle Eye]

2 hours ago, Liam Burge said:

Don't lose hope. It's not even December yet and the models are already showing great potential for cold and maybe even snow. This blocking scenario is almost nailed on, it's just the position of the high and how that influences our weather to unravel now!

Agreed

Beware : Quite a long post coming up:

I also think we need to be a bit cautious when we talk about the -NAO as the nailed on 100% cold that its sometimes discussed as.

You've got to give time for the cold pool to develop on the Eastern side of the Greenland high otherwise its essentially useless just might be associated with a brief cold pattern.

Luckily we do have the time on our side as the AAM stays relatively stable and Nino-esque.

The GWO is moving towards a phase where over the next week or so when we'll likely lose Atmospheric frictional torque and the AAM goes down . Beyond that we should enter phases of postive friction torque then southward momentum and circumglobal troughs as the AAM increases again so a brief dip then back to normal. You should also refer that there is still a lag correlation with this (not sure how long it is sorry) so keep that in note.

Note that the forecast is slightly out of date.

What does this all mean though?

The main way to lose or gain Atmospheric Angular Momentum (AAM) is by the imparting of frictional or mountain torque to or from the earth or the oceans.

Frictional torque is the rotational force imparted on the atmosphere by the friction of the surface.

Mountain torque is the torque acted by having different pressure systems on either side of a mountain.

The main way of gaining AAM is by having frictional torque and mountain torque (sort of) move from the surface to the atmosphere imparting eastward momentum into the atmosphere, weakening the relative wind. It is also associated with a Nino-esque AAM when the AAM anomaly is above 0.

What does this do though?

Weakening the relative wind increases the wave oscillations from the tropics and so we get the large scale WAA and blocking perhaps towards Greenland. Greenland blocking is where you get -VE (negative) NAO that has been discussed at length before.

Whereas weakening AAM decreases the oscillations and when the AAM anomaly is below 0 it's Nina-esque. What this does is decrease the strength of oscillating tropical waves and that promotes a +VE (positive) NAO pattern and a flatter and stronger relative wind and so the Atlantic is more dominant.

Positive Friction torque?

Where the friction torque is coming from the earth to the atmosphere and so the AAM increases. 

Why is southwards momentum transport between the equator and 30N seen as a good thing when surely it dampens the wave amplification?

Since a steady state atmosphere is assumed, southwards momentum results in the equal and opposite reaction in the other direction and so there is also northwards momentum transport. Interestingly, the same sort of principal but on a more dynamical basis works in Convective modes (am I getting boring yet ) so I may end up researching into that another time.

What about circumglobal troughs?

Couldn't find much but it sounds like it's talking about where the troughs on the other side are more of a dominant force than the peaks.

So after these next 1 or 2 blocking and therefore -NAO opportunities, mid to late December is also looking interesting based on recent GWO forecasts which can change but I don't think dramatically enough to keep up the interest.

Note that I wrote a lot of this twice after accidentally deleting most of what I'd already written so I may have missed out an important paragraph or two and my brain is starting to hurt so if you do ask questions I may not reply till tomorrow. 

Generally a decent chance of a -NAO, maybe even a few but that doesn't guarantee proper cold but with the time we've got it does increase the chance of proper cold compared to a more rushed pattern than what we have now.

[Mike Poole]

Clusters T192-T240:

26/51 follow the op.

Edited November 24, 2022 by Mike Poole