Model Output Discussion - Christmas week and beyond

[Cymro]

Watch the GFS 12 upgrade further and then do a complete flip on the 00hrs only for the UKMO and ECM to come onboard. Almost certainly going head to head this week for a dramatic somewhat turbulent ride! 

Here’s my personal favourite for 850 hPa temps

[Met4Cast]

My post yesterday about any cold later in December more likely than not to be transient:

GFS 06z: lol

Such a stark difference between the 00z and 06z it's almost laughable. The EPS has absolutely no interest in anything that amplified so for now I suspect we're seeing the 16.3v amplification bias at play. There's nothing to drive that level of amplification.

[Frostbite1980]

As I thought the op is very much at the bottom of the ens up to 192 and unless I am reading them wrong there are a fair few warmer options than the 0z. What makes me laugh is some of the ens have a lovely GL high and once again we are stuck in SWerlies. 

[Mucka]

GFS 06z/00z mean comparison 192h.  (hopefully it doesn't auto update)

If this is the correct movement of travel in FI then it is definitely the right direction for cold fans

Edited December 19, 2022 by Mucka

[nick sussex]

Putting aside post day ten I am a little intrigued by the ECM day 8 upstream.

It does temporarily re-amplify the pattern and there is an opportunity at that point down stream to get a ridge ne .

My thinking here is if we can get a better ridge on day 8 further north then the energy day 9 could head se and the jet downstream could cut back south then sw to support the ridge heading ne .

[steveinsussex]

When do the GFS Ens appear?

[bluearmy]

Def a growing trend for ridging into greeny around day 7/8  to stick around on the gefs but that op most likely taken a wrong fork around day 6/7. The 06z  gefs in general look to be less enthused at the op route at the day 7/9 timescale  

onto the 12z’s 

 

[Frigid]

Many colder options now on the table.. OP and Control following the trend

Looking good

[bluearmy]

A pretty decent mean griceland ridge by day 10. If we can cut the apron strings to the euro ridge then we would really be in business 

incidentally, heading cold post Xmas is becoming a strongly agree direction of travel but the likely consequence for the U.K. is a cold surface high. the upper temp graphs will not differentiate between cold surface highs and cold ‘easterly’ flows  where the euro ridge and low to our sw are not interfering in a negative way 

Do weather online still do a gefs cluster ??

Edited December 19, 2022 by bluearmy

[minus10]

6z gfes so far

downward trend ...op and control with support..mean held back a little by higher ens although few in number...frigid just beat me to it..

[ITSY]

1 minute ago, Frigid said:

Many colder options now on the table.. OP and Control following the trend

Looking good

Trending colder but the Op certainly at the low end of the pack. My gut says the GFS will end up with egg on its face - both because the reload cycle is so rare and the background signals are so uninspiring in the medium-long term - but then again, that's what I thought over the summer when it first started pumping out 42c in London. Two weeks later I was walking across the Heath watching fires break across the SE in 40+ heat. So never say never...

[ItNeverSnowsInWindsor]

Decent snow row for post Xmas on the 0z run.

Lets see if the 6z run improves on that!

5 minutes ago, ITSY said:

Trending colder but the Op certainly at the low end of the pack. My gut says the GFS will end up with egg on its face - both because the reload cycle is so rare and the background signals are so uninspiring in the medium-long term - but then again, that's what I thought over the summer when it first started pumping out 42c in London. Two weeks later I was walking across the Heath watching fires break across the SE in 40+ heat. So never say never...

I wonder when the GFS will start showing temperatures below -20c over Scotland. 
 

And below -10c more widely across England.

[That ECM]

Saves hunting through the gefs for the “right” chart eh?

[minus10]

Yes...crazy 6z run for cold from gfs..

Jff..noted that four times the minus 10 line pays the uk a visit during the run....

...however i think the op has definately lost the plot towards the end of the month...hasnt it??

..how low does it want to go??

[Frostbite1980]

2 minutes ago, minus10 said:

Yes...crazy 6z run for cold from gfs..

Jff..noted that four times the minus 10 line pays the uk a visit during the run....

...however i think the op has definately lost the plot towards the end of the month...hasnt it??

..how low does it want to go??

Only a 15 degree 850 difference between the control and op at the end 

[Frostbite1980]

Can I ask a question please? I know that the op run is at a higher resolution but heard the control isnt, so why do we always refer to the op and control in agreement, when we might as well say the op and perb 25 are in agreement? Genuine question

[Drifter]

1 minute ago, Frostbite1980 said:

Can I ask a question please? I know that the op run is at a higher resolution but heard the control isnt, so why do we always refer to the op and control in agreement, when we might as well say the op and perb 25 are in agreement? Genuine question

I believe the control uses the same starting data as the op. The other ens use slight tweaks to starting conditions. 
Happy to be corrected. 

[Rain All Night]

28 minutes ago, bluearmy said:

Do weather online still do a gefs cluster ??

Is this what you are looking for?

https://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=nhem&MODELL=gefs&MODELLTYP=2&BASE=202212190000&VAR=cz50&HH=384&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

 

[Lukesluckybunch]

The gfs op,yes was something a outlier..but the mean is a improvement 850's staying comfortably below 0

[Cold Winter Night]

Well, we all know GFS 6z is never wrong at Day 10, right?

Although GFS takes it to the extreme, it does have support from GEFS, and, contrary to what some are saying, from the EPS as well, including the EPS Control.

EPS Clusters 2, 4 and 6 go along with the Scandi/Iceland amplification that GFS has shown for a number of runs in a now.
Those clusters represent almost half the EPS.

To illustrate this, compared to the GFS 6z above, these two EPS members are not far off height-wise in the NE Atlantic.

However, the De Bilt plume does not show much in the way of cold on the surface yet, but continues with average temperatures, in contrast to this mild week.
There is also that little fella dropping below -15c at 2m, stretching the y-axis. If anyone is still wondering what is meant with the word 'outlier,' well, here you go!

[Catacol]

So - farewell to our cold spell. Warm, wet and windy here this morning...and always (for me) a sad feeling when the ice and frost depart. I would also say "snow" except I didn't see a flake and so that particular gloomy emotion I am spared!

While the waning of the pattern has brought in a milder snap there is plenty to consider going forward. I nailed multiple flags onto my "cold in the last third" pole a while back and that is going to prove incorrect. Timing is always the killer and the timing is off. However, the direction of travel is still the same. ECM for tomorrow:

Note the signficant and deep trough coming out of East Asia that is pumping up the Alaskan ridge and forcing it up towards the pole. This is the second amplification sector of the month underway - but about 5 or 6 days later than I thought it would happen. Que Sera.

By Xmas Eve the peak/trough shape is well established:

Note now momentum carrying through to the atlantic sector with a signal just appearing for heights to rise again over Greenland. For me ECM then loses the plot a bit - picking things up on Boxing Day with GEM we can clearly see that Greenland High being pushed up

Now....the big question as we approach the final stages of the month is whether this bout of amplification is enough to deliver a proper high latitude ridge, or whether the sub tropical high pressure belt in the Atlantic, and through to Europe, wins the day and prevents the southerly tracking jet that we were glad to see in the previous first amplification period of winter.

NWP ceases to be much use in these scenarios when we get up and over 144h (sometimes less) and human head scratching enters the fray. And this is where it gets really complex. I posted a really interesting 4 wave hemispheric anomaly chart not many days ago - take a look at this one now:

If anything it has become even more mind bending - starting to look more like a starfish than a standard hemispheric weather pattern and quite honestly picking the specifics out of this is nigh on impossible. The current ensemble trend is for the Alaskan ridge to fade away towards Asia quite quickly so that by the 27th the EPS looks like this:

Frustration perhaps for our Amis across the pond as low pressure heads back into the Aleutians and Alaska - no bad thing for Strat watchers overall though as this should signal the beginning of another round of strat attacks from the trop. Note also the signal for the Euro/Ural High building back in and edging north.

What to make of all this? Well - there's the trick. For me the runs and the ensembles are all showing signs of trying to resolve the strange starfish pattern back towards something more 'normal' but I'm not sure this is a normal winter. I'm looking at an MJO that is now bedding in at reasonable strength and moving in the western Pacific

and this will help promote more amplification as we approach New Year just when we need it to sustain the pattern. Mountain Torques have hit the bottom of another trough but from here there is only one direction they can go - and note that in East Asia we have not seen much of a retraction of pacific jet strength in recent days.

Overall AAM is slipping into negative territory and so we are creeping towards a context that says we ought to see a flatter second half of winter especially if the strat downwells - BUT we are on the cusp of a hemipsheric pattern that will put more stress on the strat and we have the MJO right were we need it next CPC expert discussion later today eagerly awaited.

Genuinely - I dont know. If this Nino-esque amplification pattern and current phase kicking off now gets enough punch to it then I could see us back in a cold airstream as we approach New Year. Or....if it doesnt quite have the penetration, and climatological bias towards strong sub tropical high pressure in a Nina pattern gets sufficient hold of things then we could be in average temperatures and looking at a very average UK shape with the north in cool cyclonic weather with the south a little more likely to see high pressure influence kick in.

But despite all this uncertainty I'm not ready to throw the towel in quite yet regarding a Scandy High. Signs of it in the ensemble forecasts at range...and if that monster alaskan ridge does decide to drift to Asia and take pressure off the trough sitting over Scandy at the moment then height rises there to me are quite possible.

So - I'd just sit back and enjoy the ride. I predict wild swings in Op runs - see GFS 06z on one end of the envelope and don't be surprised to see future runs of all models swing wildly in the coming days. Sod's Law and the usual UK climate picture would suggest that the coldest options wont appear and then we will be left desperately hunting for a SSW to do something in the second half of the season - but this is not a winter that has a usual look to it. All things possible....

 

Edited December 19, 2022 by Catacol

[Vikos]

13 minutes ago, Catacol said:

So - farewell to our cold spell. Warm, wet and windy here this morning...and always (for me) a sad feeling when the ice and frost depart. I would also say "snow" except I didn't see a flake and so that particular gloomy emotion I am spared!

While the waning of the pattern has brought in a milder snap there is plenty to consider going forward. I nailed multiple flags onto my "cold in the last third" pole a while back and that is going to prove incorrect. Timing is always the killer and the timing is off. However, the direction of travel is still the same. ECM for tomorrow:

Note the signficant and deep trough coming out of East Asia that is pumping up the Alaskan ridge and forcing it up towards the pole. This is the second amplification sector of the month underway - but about 5 or 6 days later than I thought it would happen. Que Sera.

By Xmas Eve the peak/trough shape is well established:

Note now momentum carrying through to the atlantic sector with a signal just appearing for heights to rise again over Greenland. For me ECM then loses the plot a bit - picking things up on Boxing Day with GEM we can clearly see that Greenland High being pushed up

Now....the big question as we approach the final stages of the month is whether this bout of amplification is enough to deliver a proper high latitude ridge, or whether the sub tropical high pressure belt in the Atlantic, and through to Europe, wins the day and prevents the southerly tracking jet that we were glad to see in the previous first amplification period of winter.

NWP ceases to be much use in these scenarios when we get up and over 144h (sometimes less) and human head scratching enters the fray. And this is where it gets really complex. I posted a really interesting 4 wave hemispheric anomaly chart not many days ago - take a look at this one now:

If anything it has become even more mind bending - starting to look more like a starfish than a standard hemispheric weather pattern and quite honestly picking the specifics out of this is nigh on impossible. The current ensemble trend is for the Alaskan ridge to fade away towards Asia quite quickly so that by the 27th the EPS looks like this:

Frustration perhaps for our Amis across the pond as low pressure heads back into the Aleutians and Alaska - no bad thing for Strat watchers overall though as this should signal the beginning of another round of strat attacks from the trop. Note also the signal for the Euro/Ural High building back in and edging north.

What to make of all this? Well - there's the trick. For me the runs and the ensembles are all showing signs of trying to resolve the strange starfish pattern back towards something more 'normal' but I'm not sure this is a normal winter. I'm looking at an MJO that is now bedding in at reasonable strength and moving in the western Pacific

and this will help promote more amplification as we approach New Year just when we need it to sustain the pattern. Mountain Torques have hit the bottom of another trough but from here there is only one direction they can go - and note that in East Asia we have not seen much of a retraction of pacific jet strength in recent days.

Overall AAM is slipping into negative territory and so we are creeping towards a context that says we ought to see a flatter second half of winter especially if the strat downwells - BUT we are on the cusp of a hemipsheric pattern that will put more stress on the strat and we have the MJO right were we need it next CPC expert discussion later today eagerly awaited.

Genuinely - I dont know. If this Nino-esque amplification pattern and current phase kicking off now gets enough punch to it then I could see us back in a cold airstream as we approach New Year. Or....if it doesnt quite have the penetration, and climatological bias towards strong sub tropical high pressure in a Nina pattern gets sufficient hold of things then we could be in average temperatures and looking at a very average UK shape with the north in cool cyclonic weather with the south a little more likely to see high pressure influence kick in.

But despite all this uncertainty I'm not ready to throw the towel in quite yet regarding a Scandy High. Signs of it in the ensemble forecasts at range...and if that monster alaskan ridge does decide to drift to Asia and take pressure off the trough sitting over Scandy at the moment then height rises there to me are quite possible.

So - I'd just sit back and enjoy the ride. I predict wild swings in Op runs - see GFS 06z on one end of the envelope and don't be surprised to see future runs of all models swing wildly in the coming days. Sod's Law and the usual UK climate picture would suggest that the coldest options wont appear and then we will be left desperately hunting for a SSW to do something in the second half of the season - but this is not a winter that has a usual look to it. All things possible....

 

I am stunned about your effort! Thanks so much for that, that kind of posts make me come here as a foreign…

thank you x3!!!

[ItNeverSnowsInWindsor]

It doesn’t look conclusive at all for the post Xmas period with the op firmly amongst the coldest members.

[Captain Shortwave]

A lot of  model runs to get through, but this is encouraging for early week 2.

Winds likely to come from the north for a time with settled conditions developing after a more unsettled period that could include Christmas itself. The high is most likely to drift east and sink into Europe as seen later on.

 

So a window for wintry showers because another spell of chilly and frosty conditions. It does look like we will see an Atlantic trough approach so potential blocking is going to come from high pressure building to the east. If we are lucky then an evolution towards new year of a Scandi high is plausible, but considered unlikely at this point.

The ECM is generally flatter and as such offers a briefer chillier period before we get a more north/south split that is milder than the GEFs.

   
 

So at the moment for wanting cold we want the GFS to be on the right track as this offers better short term and medium term potential.

[bluearmy]

Final observation on the gfs 06z is that gfs would be reasonably well trusted in the Atlantic but not really over Scandinavia 

hence, even if gfs 12z runs with the same solution to our west, we would need to see either gem or ec pick it up and evolve it to our northeast