Model output discussion - Closing in on Christmas

[Chesil View]

Interestingly despite it being a very wintry op run. The op is not the coldest run in the ensemble grouping.

[Froze were the Days]

2 minutes ago, Tim Bland said:

Op was a mild outlier for Xmas (see list for London) a very cold set of ensembles long term!

Chilly not very cold...if we get to that point.

[Mapantz]

4 minutes ago, Broadmayne blizzard said:

Interestingly despite it being a very wintry op run. The op is not the coldest run in the ensemble grouping.

It doesn't look particularly wintry to my eyes? Scotland and NI high ground, very much so. Elsewhere, nope.

[Tim Bland]

10 minutes ago, Froze were the Days said:

Chilly not very cold...if we get to that point.

Most people would have given their right arm for ensembles like that for Christmas week these past few years! Average Dew point temp in London at midday on 30th is just 0.5. That’s very close to snow territory...in the south!

 I know a lot can go wrong but we certainly have a fist full of tickets for the snowy lottery !! Watch the ECM show a toppler and I’ll be launching my toys in and hour

Edited December 16, 2020 by Tim Bland

[Froze were the Days]

1 minute ago, Tim Bland said:

Wow who peed on your chips today?

That really hurts...I like my chips 'crisp ent light brown' (to coin a Dad's Army quote). It's me being an eternal veteran to the failings of GFS FI, one I suppose will eventually verify.

[Cheshire Freeze]

4 minutes ago, Tim Bland said:

Most people would have given their right arm for ensembles like that for Christmas week these past few years! I know a lot can go wrong but we certainly have a fist full of tickets for the snowy lottery !! Watch the ECM show a toppler and I’ll be launching my toys in and hour

This is an impressive mean at D15

[Catacol]

1 hour ago, That ECM said:

Coldies in Algeria and Tunisia are watching this run and shouting Boom Baby

It’s going to be tricky to plot a path for a wave breaking high - strat forecasts today would encourage me to go for a Greenland rather than Scandinavian ridge - but if this is the end product come the 29th I won’t be unhappy at all. Ultimately for me it’s an all in thing - a bit of frost and marginal conditions and a 2cm dusting is good but not the pot of gold. It will always be the true pot of gold = -10 uppers off the continent, Atlantic undercut or possibly -10 uppers from a sharp trough as per Dec 2010....and in the modern climate I really think we need substantial vortex disruption to achieve it. Back in the 80s and beyond conditions could develop without this vortex-melting context - but not anymore.

This chart would signal more wave 2 forcing acting upon an already distressed vortex. Embed that Ural High for a while and we could see a genuine split SSW approx 2 weeks after this kind of pattern. Shred the vortex by mid January, and then wait for the fall out at the end of the month - the sweetest spot for seasonal frigid patterns. I still think as I have from the off that any SSW will probably come a bit later - final third of January....and then we can scan the horizon for another Beast.

In the end everything at the moment is good. Get this mobile week out the way and then the horizon will be extremely interesting. We’ve missed a couple of early season chances for cold, but this is a season that appears to be set fair for interest throughout. What is absent at the moment is any signal for sustained zonality. If the SSW doesn’t come to pass then February may yet produce it - but for now lots to keep weather watchers and cold hunters engaged. 

[Mike Poole]

ECM T144, highlighting an area of large uncertainty:

GFS and UKMO for comparison:

ECM seems looser, more amplified, in that area than GFS, but UKMO more amplified still.  Of course, we don’t know what happens post T144 on UKMO.  

[LeonH18]

These charts could show an early sign of an arctic northernly if further 12z models show signs of it coming down south rather than south-west and could being snow with good further runs of models...

This is my first post on this thread

 

 

Edited December 16, 2020 by LeonH18

[That ECM]

7 minutes ago, Catacol said:

It’s going to be tricky to plot a path for a wave breaking high - strat forecasts today would encourage me to go for a Greenland rather than Scandinavian ridge - but if this is the end product come the 29th I won’t be unhappy at all. Ultimately for me it’s an all in thing - a bit of frost and marginal conditions and a 2cm dusting is good but not the pot of gold. It will always be the true pot of gold = -10 uppers off the continent, Atlantic undercut or possibly -10 uppers from a sharp trough as per Dec 2010....and in the modern climate I really think we need substantial vortex disruption to achieve it. Back in the 80s and beyond conditions could develop without this vortex-melting context - but not anymore.

This chart would signal more wave 2 forcing acting upon an already distressed vortex. Embed that Ural High for a while and we could see a genuine split SSW approx 2 weeks after this kind of pattern. Shred the vortex by mid January, and then wait for the fall out at the end of the month - the sweetest spot for seasonal frigid patterns. I still think as I have from the off that any SSW will probably come a bit later - final third of January....and then we can scan the horizon for another Beast.

In the end everything at the moment is good. Get this mobile week out the way and then the horizon will be extremely interesting. We’ve missed a couple of early season chances for cold, but this is a season that appears to be set fair for interest throughout. What is absent at the moment is any signal for sustained zonality. If the SSW doesn’t come to pass then February may yet produce it - but for now lots to keep weather watchers and cold hunters engaged. 

Great post and interesting read. The great winters of the past, was there an ssw event prior for the majority or is this not known? I agree with your point about needing them to get something special in today’s world, as sad as that is. I also understand it’s not a given that cold for us always follows but increases the chances. TIA. Happy for anyone else to answer also. 

[LRD]

On to the ensemble spaghetti for the GFS 12z. Looks pretty cold

Edited December 16, 2020 by Blessed Weather

[frosty ground]

the ECM 168 chart look very wintry for Scotland Modesto for high ground Blizzards even 

[Vikos]

Lets hope, that Canada doesn't gain anymore cold air

 

  Yesterdays 12z--->

[swfc]

Have to say so far ec looks akin to the gfs 12z on the nhp? Early days and all subject to change in the morning 

[mountain shadow]

ECM looking poor at t+192 with the pattern swiftly collapsing East.

Hopefully an outlier.

 

 

Edited December 16, 2020 by mountain shadow

[Howie]

Is the high pressure collapsing?

[Ali1977]

T192 at -6c uppers into central England. Pretty potent and I imagine -6c uppers will cover the whole of the U.K. by T216 (Xmas day) , which would mean any showers would be on the wintery side at-least. Short lived cold snap on this run though.

Edited December 16, 2020 by Ali1977

[johnholmes]

Just a view of how to try and link synoptic charts to the 500 mb anomaly charts for a, pssibly' more balanced view of what the models are trying to show?

 

 

charts for wed dec 16 2020 anomaly and synoptic.doc

[Weathizard]

DISRUPT!!

[Zak M]

This ECM run is looking pretty good to my eyes - except if you live in the west!

   

Edited December 16, 2020 by Zak M

[TSNWK]

Falling over into scandi.. was expecting worse.. will take it.

 

[Ali1977]

-5/6c 850s for everyone on Xmas day, not great but also not lashing down with rain and wind - semi festive if not white!! 

[Skullzrulerz]

A bit confused here with some saying it's bad and some saying it's good in regards to the ECM run?

I still think we are going to get a halfway house between the two 

[ICE COLD]

People will moan but it’s a decent run . All within the wide envelope as @bluearmywould say

[swfc]

Small margins keeping that low pressure/PV up the west coast of greenland. 6z better ridging on ec in Atlantic. No disaster just a point