Model output discussion 11/12/21

[Lukesluckybunch]

hmm the ECM op was at lowest end,the mean is a lot milder

[LRD]

Just now, Lukesluckybunch said:

its not awful and crucially the mean stays below zero.also quite a few cold members there

Compared to the last few days, it's dross. that mean line was near -5 on Tuesday IIRC. The main cluster is now above 0 for Xmas. It might be better further north but, down south, there's no sugar-coating it I'm afraid

It might flip back later today. Who knows?

[MattStoke]

3 minutes ago, LRD said:

Sorry everyone but I just can't see the GFS and its ensembles being so wrong. This is an awful graph (for cold) compared to Tuesday and even yesterday

ECM looks great, of course but it's probably wrong

I'm not being a WUM or a mood-hoover. I'll be positive when it warrants but I won't be if it doesn't. I'm not writing this off yet. 12z runs and the ECM46 might tell us more. But it's not looking good

The GFS and it’s ensembles have been wrong numerous times before. That’s not to say it’ll definitely be wrong this time. Just that it’s not definitely right! Entire model suites can and do change in one way or another.

[markw2680]

As lovely as ecm is I’d say fi starts around 144/168 hrs latest so anything after that is just not really worth taking much notice of, I know it’s what we all want to see but it will chop and change 100% so for now we need to take with a pinch of salt to avoid that possible disappointment 

[Lukesluckybunch]

1 minute ago, LRD said:

Compared to the last few days, it's dross. that mean line was near -5 on Tuesday IIRC. The main cluster is now above 0 for Xmas. It might be better further north but, down south, there's no sugar-coating it I'm afraid

It might flip back later today. Who knows?

yes still too far out really for xmas,lets hope 9days long time

[LRD]

It's not an outlier (until the very end) but the ECM op is a pretty cold run in comparison to the suite

This is ebbing away I reckon. As I say let's see the 12z runs and EC46 later tonight

 

[Lukesluckybunch]

3 minutes ago, Lukesluckybunch said:

hmm the ECM op was at lowest end,the mean is a lot milder

one glimmer of hope is that the mean line continues to fall at the end

[Notty]

3 minutes ago, Lukesluckybunch said:

its not awful and crucially the mean stays below zero.also quite a few cold members there

It also shows a lot of uncertainty after T+96 which is a little concerning. Interesting model watching few days coming up.

[Mark Smithy]

Well, the ECM is as astonishing as you will ever see.

The transition at around T168 still looks scarily fragile but the end result is simply gobsmacking.

 

[Kasim Awan]

1 minute ago, LRD said:

It's not an outlier (until the very end) but the ECM op is a pretty cold run in comparison to the suite

This is ebbing away I reckon. As I say let's see the 12z runs and EC46 later tonight

 

Sorry but how can it possibly be ebbing away when 24 hours ago the ecm had us on the brink of mild south westerlies over Xmas? 

[northwestsnow]

17 minutes ago, lassie23 said:

Is it a boom or a bust, some think others think all very confusing

It's high stakes.

Truth is nobody knows. 

And I'm not sure the models do either .

Youd have to back EC in tandem with the ec 46 ..

And what an ec 46 later !!

Edited December 16, 2021 by northwestsnow

[Mark Smithy]

27 minutes ago, Kasim Awan said:

Valid worries being indicated but I say head up, snow gang, excellent output this morning. Gfs being alone in being progressive is perhaps a good thing, indicates that the model is struggling which is symptomatic of a fast paced -Nao evolution.

Indeed and as I mentioned earlier, the GFS really struggles with height rises to our north. A Svalbard High is so rare that the progressive American model never seems to pick it up.

ECM isn't on its own. GEM also has a Svalbard High.

[Jason M]

At long range ECM has an awful lot of history with easterlies. GFS can spin up huge lows whereas ECM over amplifies and tends to show a lot of easterly options. It’s nice to see charts like that being shown on Christmas Day but I’m very skeptical. 

[Kasim Awan]

3 minutes ago, Jason M said:

At long range ECM has an awful lot of history with easterlies. GFS can spin up huge lows whereas ECM over amplifies and tends to show a lot of easterly options. It’s nice to see charts like that being shown on Christmas Day but I’m very skeptical. 

I agree it might be ott. GEM atm seems a more realistic middle ground with a weak easterly flow, baltic & snow flurries over xmas. Also bear in mind GEM seems to be better dealing with the complexity right now as it was the 1st to indicate the more pronounced easterly. 

Edited December 16, 2021 by Kasim Awan

[northwestsnow]

1 minute ago, Jason M said:

At long range ECM has an awful lot of history with easterlies. GFS can spin up huge lows whereas ECM over amplifies and tends to show a lot of easterly options. It’s nice to see charts like that being shown on Christmas Day but I’m very skeptical. 

Very sensible.

Of course some of us get a bit carried away but I suppose it's all part of the fun .

But at the back of our minds disappointment always looms ...

[Updated_Weather]

Good sign (not an outlier) even if 00z was near the bottom.. it only means one thing folks! More runs needed!

Edited December 16, 2021 by Updated_Weather

[ICE COLD]

@bluearmy what’s the ens extended showing . Clusters etc please

[LRD]

1 minute ago, Kasim Awan said:

Sorry but how can it possibly be ebbing away when 24 hours ago the ecm had us on the brink of mild south westerlies over Xmas? 

It's ebbing away because:

1) Yesterday, the trend to bring in the Atlantic started. On a southerly track at first but has trended north since

2) The ECM op is the pick of the runs and it's such a fragile set up to get us there. The whole pattern could change very easily on that run. And it's at the cold end of the 850s suite with milder solutions obviously in there

3) If the GFS op was a warm outlier compared to its ensembles, I'd be far more convinced. The fact that its ensembles have moved with the op is significant. As much as people dismiss the GFS on here it is a decent model and I can't see it and its ensembles being that wrong

As I say, I'm not writing this off yet. Just feel it's slipping away and needs a good 12z suite and EC46 to bring things the other way. I write this hoping I'm wrong by the way. I'm not looking to wind up or bring people down. Just saying it as I see it and how I feel this is going to go. Please feel free, if things flip back (and cold verifies), to remind me of this post. I'll be very happy to eat humble pie! 

[Kasim Awan]

Just now, Updated_Weather said:

Can you give us a bit more context please mate?

[LRD]

1 minute ago, Updated_Weather said:

Control follows op (if I've read that right). That's more encouraging

[Updated_Weather]

On 16/12/2021 at 08:09, LRD said:

Control follows op (if I've read that right). That's more encouraging

Yep

[karyo]

The clear difference with the ECM is that the Atlantic lows manage to enter the Med which helps push the cold westwards. The other major models are not so keenm on this. For example, the GFS only shows a shallower low crossing Iberia but then it fizzles out. 

It has been very difficult so far to push the jet stream over the Med (in fact the last few winters have been dominated by high pressure) and I am not sure whether it can be achieved that easily this time. Also, increasing solar activity may sadly work against us with this.

[northwestsnow]

3 minutes ago, Kasim Awan said:

Can you give us a bit more context please mate?

They're cold.

[Wingman Blue]

18 hours ago, Kasim Awan said:

Hi, it's not possible to draw a conclusion, however it is possible to draw a spread of probabilities through a few potential outcomes. The chance of each outcome verifying is reliant on certain synoptic events which are specified to the outcome. This means, assigning realistic probabilities requires careful attention not to the model output post 200h (•200h is the key time frame atm), but the upstream.state, tilt and magnitude of amplification expected in the earlier time ranges (120 to 180h). 

The current uncertainty which is giving us a split in model outcomes is associated with how optimal any trough disruption is between Iberia and central Europe at around 200h. Currently, around 40% of the output suggests the northern high will be too weak, Iberian heights too strong and therefore a lack of connection which results in a continuation of high pressure through Xmas, temps close to normal. The rest of the output successfully ignites an easterly due to optimal trough disruption & linking. Within that remaining 60%, it's a 5050 split between a bfte scenario, blizzards, and something more tame - i.e. uppers to -6 and wet snow in an easterly flow. The colder option relies on a slightly stronger block to the north. Still, that is what the models are showing, rather than what I am thinking.

Now, time for a few probabilities based on applying logic and interpretation to the output (spread of probabilities given below is purely based on applying some logic to these above scenarios, thereby logically modifying the model generated probabilities).

Middleground (median) - this method is useful because it balances all synoptic drivers to a neutral state. This method presumes a moderate strength high and weakly amply acceptable trough disruption (Iberia). This logic would place us under a weal frigid easterly flow over Xmas with an abundance of snowfall opportunities. The problem with this method is that it neglects the potential for greater impacts from other synoptic drivers i.e. the ones discussed above. Nonetheless, it is valid so it receives a 45% risk tag.

The other two probabilities are between 1) a switch back to high pressure centralized across northern Scotland with a weak easterly flow across SE England - light snow flurries, cold & frosty elsewhere. This has lost some support, however knowing the potential for a switch back & potential the models could be overestimating break down of the high - 20%.

And 2) a more northerly tracking jet - whilst maintaining an easterly flow. This would likely give feet of snow to northern hills, whilst maintaining intermittent milder spells in the south - 15%. A variation of this option would be more restrictive with snowfall to Scotland - milder sectors dominate in the south - 15%.

There are a few others too, such as a UK high, but these are becoming more negligable (5%). It's not possible to say which outcome will verify (yet), we need to close watch the following: lowering heights around Iberia and any resurgence in heights around Iceland by 200h, as this could sway the pendulum between the options above. Also notice that the probability of wintry spell is higher in my prognosis than in the model output? This is because models could be over doing the milder push post 200h due to biases.

It's rare to have such brilliant potential this time of year.

Wow! Many thanks for such a lucid and succinct reply, Kasim.

A great explanation of our present state, I think.

[knocker]

2 minutes ago, ICE COLD said:

@bluearmy what’s the ens extended showing . Clusters etc please

Not ba but in line with my earlier comments vis the importance of the energy distribution, the 192-240 clusters reflect this. In other words stoill considerable doubt over the detail for the Xmas period