Model output discussion - cold spell approaching?

[lorenzo]

4 minutes ago, sheikhy said:

Aaahh the good old pub run!!only to bring us back down in the morning!!

Yes, normally but now we are on the cusp of the models beginning to get a handle on huge dynamics brought around by the SSW. These are throw the cards up in the air ( warmly) events...

This shows the variation in temperature vs previous means and we can see clearly where we are currently vs projected disruption, the 06z GFS also delivered an AO cranking in at -6SD, totally agree the Pub Run is fun and games, this time it is probably on the envelope of what could coherently lie ahead.. Initial chaos may smooth towards Friday and things become clearer. 

Models just are not up for dealing with these dynamics and this is why patience is required, there is no golden x =y in strat warming events, there are some clues of good connection to trop. impacts as I see it from tweets by Hannah Attard ( further coupling exists)  and Amy Butler ( where does the vortex energy split), this is probably the best week of model watching anyone can examine for many a year. What we do know is that this is a significant SSW and the effects / artefacts will be felt for some time.

This for me is the watch point - the nuances in the break 5 days - literally every model has varying degrees on how it sees this, manifests lows, manifests phasing etc.

That aside and longer term we do have our old winter wild card the MJO waiting in the wings to enter stage right and continue to reshuffle the deck.

 

[ICE COLD]

Admittedly way out in FI now but what a run from the 18z just gets colder and colder . No one will be moaning if we get these uppers ( well only if you don’t like cold )

[Jason M]

Fantastic pub run. By 300 hours it’s just frigid. Those -8 uppers would sure feel different to last week. I’d imagine super low dew points, very low theta values. Basically it’s a good old fashioned boom run. Nice to see a real cold run rather than one that just looks cold.

[rug]

2 minutes ago, feb1991blizzard said:

Another terrible run on the wrong side of marginal!!

And by the way Devon gets 6 inches of snow.

Hallelujah!!!!!!!!!!!!!!!!!

[sheikhy]

1 minute ago, ICE COLD said:

Admittedly way out in FI now but what a run from the 18z just gets colder and colder . No one will be moaning if we get these uppers ( well only if you don’t like cold )

Remember when you were posting these charts in feb 2018!!!maaan the pinks and purples that were coming in from the east

[Mike Poole]

4 minutes ago, Gadje said:

The thing to me from that is the Atlantic is done.

It definitely is, but it leaves us at the mercy of summer style systems if there is nothing driving the weather, so we do need either a Greenland or Scandi block to dictate...that is what all this is about, with all the uncertainty about, will a block take, and hold, and in the case of Greenland, not too far west!!!!!!

Edited January 12, 2021 by Mike Poole

[Ice Day]

Well, whilst the GFSP was pretty awful early on, it has gone on to produce this at day 11 - the majority of the PV once again moved away from it's normal winter home.  This would potentially produce something decent for the UK a day or so later.  

We're seeing really chaotic charts once again, FI firmly at day 4/5, everything else is for entertainment only (and it's certainly is entertaining)

 

[Allseasons-Si]

The parra gets there in the end but a slower evolution...

[Kentspur]

5 minutes ago, feb1991blizzard said:

Another terrible run on the wrong side of marginal!!

And by the way Devon gets 6 inches of snow.

Sure is considering about half the population of the UK (or more) live in the white patches

[Mike Poole]

1 minute ago, Allseasons-si said:

The parra gets there in the end but a slower evolution...

All roads lead to Rome, when a SSW is calling the shots.  We just don’t yet quite know what Rome means for our tiny island nation.  

[bluearmy]

18 minutes ago, Griff said:

PS

Do check out the tweet thread, PV Denis reckons a split will occur... 

See you tomorrow! 

Yes, it splits for a few days and then the remnants head back east and join back together. .....and remember it’s Denis ......

[Speedbird]

3 minutes ago, Jason M said:

Fantastic pub run. By 300 hours it’s just frigid. Those -8 uppers would sure feel different to last week. I’d imagine super low dew points, very low theta values. Basically it’s a good old fashioned boom run. Nice to see a real cold run rather than one that just looks cold.

Anything falling from the sky will be guaranteed to be white - or if you're in the south east, ice pellets

[ICE COLD]

4 minutes ago, sheikhy said:

Remember when you were posting these charts in feb 2018!!!maaan the pinks and purples that were coming in from the east

There be on there way in the next few weeks mate

[Allseasons-Si]

Good set of ops today,i am happy,same tomorrow 

night guys.

[Gadje]

4 minutes ago, Kentspur said:

Sure is considering about half the population of the UK (or more) live in the white patches

The majority of whom would prefer a mild dry winter.

[Allseasons-Si]

A last note,...the gfs continues cold to the end.

[bluearmy]

The para will be great late on too - we keep seeing that more pronounced second arctic ridge punched in from the pacific side late week 2.  

[Ice Day]

16 minutes ago, Frosty Winter said:

Another fantastic GEFS 18z ensemble mean at t174. Slowly starting to count down the days now...

Hi FW - that's the mean from the 12z.  This is the 18z - not quite as good with the high pushing up to Greenland, but still more than acceptable.

[andymusic]

latest harmonie for thursday

[Purga]

Right at the end we have the tantalising prospect of disrupting troughs approaching a deeply entrenched & huge dense cold air mass over Europe / us.

A 1947 type scenario for February? The stuff of dreams!

Pub run with knobs on!

[weirpig]

Just now, andymusic said:

latest harmonie for thursday

That i believe is a notable shift since its last run 

[Mucka]

Poor GFS 18z with only marginal ice days of between 0C and -4C

We need -5C by day and -10C by night to have a chance of snow.

It would feel quite balmy in the South in a slack flow.

[Gadje]

It has been a great winter weather watching so far. I think it might get better.

[andy989]

It's mad how this place all comes together as friends when the cold shows, all the bickering melts away like a crack den with everyone getting their intravenous fix. I love it (here not crack). 

[Ice Day]

4 minutes ago, bluearmy said:

The para will be great late on too - we keep seeing that more pronounced second arctic ridge punched in from the pacific side late week 2.  

You're not wrong Blue.  It's gone absolutely bonkers late on

That lot can't miss us..... surely???