Model output discussion - 1st December onwards

[knocker]

1 minute ago, bluearmy said:

Yes knocks, we may get a frost!

Indeed, although not in the Royal Duchy.

[radiohead]

Stunning GFS output this evening. I don't believe it for a second but it's certainly entertaining to see.

Within the more realistic time-frame, it does appear that eastern Europe could well be heading for a significant cold spell in the days ahead. 

[kumquat]

Even if all we get out of this hogwash is that (Eastern) Europe takes some cold then that is a positive step for the New Year.

Happy Christmas Netweather folks.

 

[swilliam]

Whilst the 18Z has been fun to look at I think that it is all it is likely to be. Looking at the ensembles whilst there is quite a bit of support for the overall pattern there is is none for the extreme evolution of the OP so it likely to be an outlier. Most of them lift the cold pool out before reaching the UK. Not to say it won't happen like that though.

[forecaster]

Most EC ensemble members have the block dead or too far east by 8th January. Nothing too exciting on the EC ensemble except a colder spell around New Years, though the det is on the cold side of the ensemble members in that regard.

EC clusters most of its members around New Year in the "Positive NAO" camp, only about 20% in the "Blocked" regime, and even they die following that time period. 

[Cheshire Freeze]

2 minutes ago, radiohead said:

 

Within the more realistic time-frame, it does appear that eastern Europe could well be heading for a significant cold spell in the days ahead. 

Which, if you saw the long range modelling, was not meant to happen.....

Just goes to show.

[JP1972]

Missing data lads ....

[DAVID SNOW]

40 minutes ago, knocker said:

Rather depends on how you define remarkable but in my book some places 37F above the 1981-2010 average just about covers it.

On the warm side agreed, Knocks , Merry Christmas ,

[booferking]

2 minutes ago, JP1972 said:

Missing data lads ....

Missing data you might be right, but  just because its showing an bitter easterly lets just wait and see in the morning and  Merry Christmas to you all.

[East_England_Stormchaser91]

Just nearly spat out my prosecco looking at the 18z! My word! 

Think the pub run has had a few too many of them too! This is literally my Xmas present.

Anyway, merry Christmas to all, have a good one!

[kumquat]

The heart of the push of WAA is seeded right here, right now. The 965mb storm over Baffin. Combined with other drivers this could be our sanctuary. This isn't FI. This is now. This is where the mathematical equations take us. Plenty of reason to be positive.

[Mucka]

Massive outlier as expected but you never know, I mean I thought Santa wasn't real once!

 

[Cheshire Freeze]

2 minutes ago, kumquat said:

 

The heart of the push of WAA is seeded right here, right now. The 965mb storm over Baffin. Combined with other drivers this could be our sanctuary. This isn't FI. This is now. This is where the mathematical equations take us. Plenty of reason to be positive.

I've just read a comment on another forum which I agree with. With the amount of WAA it's more a case of when and not if. There have been several classic winter periods that have been preceded by such WAA events. However, this is the UK weather we're talking about and usually if it can go wrong, it will go wrong!

[forecaster]

4 minutes ago, kumquat said:

 

The heart of the push of WAA is seeded right here, right now. The 965mb storm over Baffin. Combined with other drivers this could be our sanctuary. This isn't FI. This is now. This is where the mathematical equations take us. Plenty of reason to be positive.

 

Likely a huge area for error propagation, which the equations don't explicitly handle. That's what the ensembles are for. This is why neither the GEFS nor EC Ens are very excited by this at all:

 

http://www.weatheronline.co.nz/cgi-bin/expertcharts?LANG=nz&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cslp&HH=228&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

[Allseasons-Si]

Well what a fantasic day of model watching,but we will see if this continues in the next few days,what i will say is that we either get the easterly or nw-se tracking jet,win-win scenario

the 18z at 300hrs(if it comes off) which it won't,could be a north sea snow making machine just like 2010

all aboard the Siberian express,next stop,the uk,hopefully,we deserve it.

HAPPY XMAS everyone

[Glacier Point]

Aside of the op gfs froth, I make that the last 9 gefs means to end up at a negative AO, themed on an extension of the Alaskan ridge poleward towards the Kara Sea ridge.

The ridge over Alaska looks reasonably assured given model consistency and assumed Western Hemisphere tropical forcing. The Kara / Siberian ridge isn't as assured, but has definitely gained some traction in terms of longevity and strength. It also fits the idea that the for the first time this winter we get an injection of warm air into an area of unsually warm seas / surface temps.

so musing a little, cyclonic signal for NW Europe, good fit for upstream ridge and some reasonably grounds for thinking the ridge to our NE is a player, that places us on tenterhooks. The 18z gfs whilst probably a bit progressive, may be revealing the route map to cold. Block to the NE deflecting the flow increasingly south and east, advancing westwards over time towards Greenland forcing the AO more strongly negative. Lots of uncertainty, not least because for me this is a touch premature (better confidence if tip his were second half of January). Key here is the block to the NE. Any weakness in that, and a more south westerly flow would be able to exploit. Worth also noting that there is some scope for retrogression and for Western Europe to remain under a sw flow in this current regime.

Going to be an interesting week or so model watching I feel.

Edited December 25, 2015 by Glacier Point

[Cheshire Freeze]

1 minute ago, forecaster said:

 

Likely a huge area for error propagation, which the equations don't explicitly handle. That's what the ensembles are for. This is why neither the GEFS nor EC Ens are very excited by this at all:

 

http://www.weatheronline.co.nz/cgi-bin/expertcharts?LANG=nz&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cslp&HH=228&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

On the flip side, are the ensembles any more likely to pick up the correct solution than the op? I dislike ensembles with a passion, I've seen too many flips, too many flops and I get the impression that sometimes rather than 1 op run getting the wrong idea, you get a whole suite full of the wrong idea. Just my opinion though!

[kumquat]

Quote

Likely a huge area for error propagation,

In which case my point stands. Ensembles galore might be taking the wrong paths.

[Cheshire Freeze]

2 minutes ago, Glacier Point said:

Aside of the op gfs froth, I make that the last 9 gefs means to end up at a negative AO, themed on an extension of the Alaskan ridge poleward towards the Kara Sea ridge.

The ridge over Alaska looks reasonably assured given model consistency and assumed Western Hemisphere tropical forcing. The Kara / Siberian ridge isn't as assured, but has definitely gained some traction in terms of longevity and strength. It also fits the idea that the for the first time this winter we get an injection of warm air into an area of unsually warm seas / surface temps.

so musing a little, cyclonic signal for NW Europe, good fit for upstream ridge and some reasonably grounds for thinking the ridge to our NE is a player, that places us on tenterhooks. The 18z gfs whilst probably a bit progressive, may be revealing the route map to cold. Block to the NE deflecting the flow increasingly south and east, advancing westwards over time towards Greenland forcing the AO more strongly negative. Lots of uncertainty, not least because for me this is a touch premature (better confidence if tip his were second half of January). Key here is the block to the NE. Any weakness in that, and a more south westerly flow would be able to exploit.

Going to be an interesting week or so model watching I feel.

GP, have to agree. It's premature but it's good to see. I can also tell from this what your expectations are for mid Jan onwards...and they aint warm. Obviously you're restricted now as to how explicit you can be with your thoughts but that's as clear a hint as you'll see from you about where you expect us to be in 3 weeks time!

[forecaster]

5 minutes ago, CreweCold said:

On the flip side, are the ensembles any more likely to pick up the correct solution than the op? I dislike ensembles with a passion, I've seen too many flips, too many flops and I get the impression that sometimes rather than 1 op run getting the wrong idea, you get a whole suite full of the wrong idea. Just my opinion though!

 

Not an individual ensemble member, no. You would always expect an ens member to be worse than it's op. Their power lies in considering them as a family. The idea is that they represent initial uncertainty in the atmosphere well enough to also forecast future uncertainty. Doesn't work quite that well in reality* but they aren't bad.

Deterministics flip and flop much more frequently than ensembles.

*ensembles are usually underdispersive which means they never quite capture or forecast the full extent of uncertainty in the atmosphere. But they do a better job at uncertainty than deterministics. I heard 100-200 members would be needed realistically - which is beyond even the ECMWF right now!

[Geordiesnow]

As Crewecold says, if you get WAA heading into the Arctic then no doubt you will get the cold coming out of the Arctic into the more middle latitudes which increases the cold potential for the UK for sure. 

Of course its not as simple as that as this evening's ECM shows but whilst blocking is there, the chances for cold to occur will remain. 

I don't expect the 18Z FI to be repeated at this stage and I think any output which don't look like the UKMO and have any blocking sinking will be a good run in my book even if they don't show any cold near us because the potential will be there and all cold charts on here will do is rip people's hair out and raise expectation. 

[kumquat]

I agree Geordie and however we look at it, WAA going up towards the Pole, building surface pressure and pushing colder air south into mid-latitudes has got to be welcomed.

[Rocheydub]

You're all wrong... Tonight the GFS got its flight data from Santa's sleigh! It's just magiced up the NWP to give us all a happy Christmas!

And so I wish you all a very merry Christmas!

[kumquat]

I am missing Data.

 

[Duane S.]

As per my post of a few days ago, it is simply all down to the potential vertical WAA surge up into the pole, a decent injection such as recent forecast charts have been showing cannot occur without consequence for mid latitude areas. Even if we have to endure further toasty conditions in the process and see the cold flood down way to our East, the odds for a cold spell occuring here soon after would shorten massively. A repeat of Jan 1987 should not come as the biggest surprise should it happen (unlikely still but there remains the potential with this set up)

To my mind the MJO looks to be the main player here and with most models seeing no real let up in the ppn as it drives through the Pacific, January looks to be starting on a very interesting note indeed.

As others have quite rightly said, the Ens as a whole are as prone to flipping as the op, which naturally somewhat negates their usefulness! Not always of course, but often enough...