Model Output Discussion - Into 2024

[Scott Ingham]

6 minutes ago, feb1991blizzard said:

back

29th jan > last chart

hmmmmm…… this is becoming madness!

[Scott Ingham]

1 minute ago, northwestsnow said:

EC 46 !!!!!

BLOCKING GALORE

Shuffling high lat blocking……Greenland/Iceland/Scandi/Iceland/Greenland…. Surely not a re run of a 63?!?! That feels unrealistic just typing it but lots of it seems logical when I think about it! I’ll take a 2 week spell tbh!

[northwestsnow]

[Mike Poole]

4 minutes ago, northwestsnow said:

This is very promising, and does I think suggest members flirting with a shuffling high latitude block.  Remember that these were run with 0z data, and the 0z clusters were uncertain after day 10.  I’d be really interested to see tomorrow’s 46 output if the 0z EPS tomorrow are anything like today’s 12z ones. 

Also, a new cluster (just a few, but it wasn't there yesterday) hinting at an SSW in 2-3 weeks time!

Edited January 2 by Mike Poole

[Bullseye]

Eyes on that cluster of near 0 zonal winds for around two weeks time especially when compared to only 48 hours ago. 

Looks to also be some momentum on further blocking into final week of month leading into February - would further support seasonal models thinking last few months. 

 

Edited January 2 by Bullseye
Got me days and week mixed up!

[The Enforcer]

GEFS 12z P29 is painting an alternative Day 10 picture:

Hopefully, this option won't gain traction in the 30 or so runs before Day 5 is reached.

Edited January 2 by The Enforcer

[Redwood]

GFS 12z looks good? I haven’t posted in a long time but I think we could be going down the right path this time 

[AO-]

P20 is just perfect. Check it out. I picked day 12 as an example.

[nick sussex]

The ECM has been truly awful over the last few days.

Wrong at day 5 and now it’s decided to have the worst medium term solution.

As much as there might be a retrogression signal it’s not a done deal and there’s a lot of runs to get through before it comes into the more reliable timeframe .

 

[sebastiaan1973]

45 minutes ago, Singularity said:

Important to view the Sun-Tue ‘might be’ easterly as independent from the -NAO driven one being signalled for mid-month.

By comparison it’s a lot more fragile, so to speak, due to it depending on precisely how the high shapes up and orientates. Still feasible that it could do so in a manner that allows a decent cut-back of low 850s across S UK; we may as well pick options out of a hat regarding such a highly sensitive detail.

As far as I can deduce, the subsequent retrogression signal is connected to a combo of the minor SSW and lagged response to MJO phase 3 coupled with AAM not falling very low due to El Niño.

At this lead time the signals from those will dominate how the modelling behaves so yes, as always, well run the ‘finer details gauntlet’ nearer the time - but it’ll take a more substantial spanner in the works to totally derail it, compared to this coming Sun-Tue.

You mean phase 1 of the MJO?

[geordiekev]

33 minutes ago, MATTWOLVES 3 said:

Boom boom boom let me hear say wayo...wayo! I say boom boom boom the cold is coming....coming...

Once again simply sterling.  Me and the dog have loved this roll out...never mind the op, the ens are amazing.

Breath easily you lot....

Seriously folks I need an horlix and an early night...I think me eyes are going as well..was a real struggle seeing the full graphics on those ens.. First ya hair goes then ya eyes...then ya bloody faculties...loved every minute of it though! Always a pleasure though.

Some absolute in there. Nice splits too 

[summer blizzard]

I'll admit that my hopes were raised last night by the Euro but I'll remind you all of two days ago when I said that arguably the biggest combined impact on any downwelling zonal wind weakness and progression of the tropical convection is likely to be around the 20th. What we are seeing now is more the lagged impact of MJO movement during December. 

Moral of the story, we may need two or three bites from a UK high cherry but the medium term signal is likely to get better rather than worse as the month progresses. 

To keep a bit more on topic, I think the Euro is a good shout.

[AO-]

33 minutes ago, AO- said:

P20 is just perfect. Check it out. I picked day 12 as an example.

T850 -20. Just unbelievable. 

 

I couldn't not share this with you. Enjoy. This is a very nice opportunity to see some severe cold.

[fromey]

1 minute ago, AO- said:

T850 -20. Just unbelievable. 

 

I couldn't not share this with you. Enjoy. This is a very nice opportunity to see some severe cold.

This is where those temps are coming from.

todays lows in Finland 

[AO-]

2 minutes ago, fromey said:

This is where those temps are coming from.

todays lows in Finland 

Except this is now and my chart is at day 15. But I'm confident we will see some very low temperatures in Europe later on. Not just Scandinavia anymore. Nice start of the year.

[northwestsnow]

Incon 18z looks " splitty " at 120..

[WYorksWeather]

Just comparing 12z to 00z. Only very subtle changes in the short range, probably a very slight moderation of the 850s around the 8th - mean up from -6C to around -5C. Not enough to be worrying about really.

What I also thought might be instructive is to take a look at an example very mild and very cold run, to see how we might get to either scenario. I'll get the disappointing scenario out of the range first.

ECM P25 - High and Dry

This run turns into a complete disappointment - starts promising enough, but by mid-month we're back to absurdly mild conditions, double digit 850s and widespread temperatures into the mid-teens.

Through day 6, surprisingly similar to P14 below, with a UK high. Crucially though, the centre is a bit further south, over Scotland and/or Northern England.

At day 8, still cold at the surface under a temperature inversion, but the high is too far south to give us an easterly.

At day 10, the high is losing its grip.

By day 12, a gap has opened up between the Greenland high and the Scandinavian high, and the Atlantic blasts through once again.

Then, by day 14, it goes the whole hog, and brings in a ridiculously mild south-westerly airflow (very warm SSTs over the Azores).

ECM P14 - Winter Wonderland

This ensemble run ends very cold indeed - overnight lows at -5C and lower towards the end, several consecutive ice days, widespread snow chances.

At day 4, the high begins to pump northwards.

By day 6, the high links up and becomes a broad area setup across Iceland, the UK, and western Scandinavia, with the centre over the Northern Isles.

At day 8, a low passes through the channel (possibly enough for a snow event in the south?).

It gets better, and by day 10 the high retrogresses NW, becoming an absolutely stonking Greenland high!

At day 12, the high pressure continues to retreat west, but this allows low pressure to mix into upper air down in the -10C range, probably a massive snowmaker for much of the country.

At day 14, more of the same, with small areas of low pressure continuing to bring the risk of snow.

Summary

So, we can see that even comparing 'best' to 'worst' ensembles, there's a fair consensus over the next week or so - cold and frosty.

Beyond that, a worst-case is that a gap opens up, with part of the UK high sinking south-eastwards. This would then allow the Atlantic to resume targeting the UK, and on an exceptionally mild SW-NE alignment eventually.

The best case relies on the UK high holding firm, and then as it retreats towards Greenland, it allows a bitterly cold easterly in behind it, with lots of low pressure, which in frigid air would give very high snow chances.

Edited January 2 by WYorksWeather

[northwestsnow]

18z v 12z

[Ali1977]

2 minutes ago, northwestsnow said:

18z v 12z

Yeah the PV looks a bit more feeble around NE Greenland , with more WAA heading towards the pole from Alaska too

[Guest]

3 minutes ago, WYorksWeather said:

Just comparing 12z to 00z. Only very subtle changes in the short range, probably a very slight moderation of the 850s around the 8th - mean up from -6C to around -5C. Not enough to be worrying about really.

What I also thought might be instructive is to take a look at an example very mild and very cold run, to see how we might get to either scenario. I'll get the disappointing scenario out of the range first.

ECM P25 - High and Dry

This run turns into a complete disappointment - starts promising enough, but by mid-month we're back to absurdly mild conditions, double digit 850s and widespread temperatures into the mid-teens.

Through day 6, surprisingly similar to P14 below, with a UK high. Crucially though, the centre is a bit further south, over Scotland and/or Northern England.

At day 8, still cold at the surface under a temperature inversion, but the high is too far south to give us an easterly.

At day 10, the high is losing its grip.

By day 12, a gap has opened up between the Greenland high and the Scandinavian high, and the Atlantic blasts through once again.

Then, by day 14, it goes the whole hog, and brings in a ridiculously mild south-westerly airflow (very warm SSTs over the Azores).

ECM P14 - Winter Wonderland

This ensemble run ends very cold indeed - overnight lows at -5C and lower towards the end, several consecutive ice days, widespread snow chances.

At day 4, the high begins to pump northwards.

By day 6, the high links up and becomes a broad area setup across Iceland, the UK, and western Scandinavia, with the centre over the Northern Isles.

At day 8, a low passes through the channel (possibly enough for a snow event in the south?).

It gets better, and by day 10 the high retrogresses NW, becoming an absolutely stonking Greenland high!

At day 12, the high pressure continues to retreat west, but this allows low pressure to mix into upper air down in the -10C range, probably a massive snowmaker for much of the country.

At day 14, more of the same, with small areas of low pressure continuing to bring the risk of snow.

Summary

So, we can see that even comparing 'best' to 'worst' ensembles, there's a fair consensus over the next week or so - cold and frosty.

Beyond that, a worst-case is that a gap opens up, with part of the UK high sinking south-eastwards. This would then allow the Atlantic to resume targeting the UK, and on an exceptionally mild SW-NE alignment eventually.

The best case relies on the UK high holding firm, and then as it retreats towards Greenland, it allows a bitterly cold easterly in behind it, with lots of low pressure, which in frigid air would give very high snow chances.

Great Post. And there are quite a few members going the milder route....

[Duane S.]

 

However…This shows a quicker return to average than the last couple of days.

Personally, I’d prefer to see us miss an SSW but maintain weak westerlies through January (and hopefully beyond). I think with this current ENSO/IDO/QBO combo, we will reap the rewards.

Then factor in the wave breaking from recent momentum spike, this sees us through favourably to maybe 3rd week of Jan. An Atlantic incursion likely after that (may be a VERY good thing that mind), then favourable MJO to then kick in late month to set up a memorable February.

Simples. What could possibly go wrong

[Catacol]

While celebrations abound - this is significant perhaps. Frictional torque already on the turn, looking like its drift into negative territory has bottomed out:

Similarly the crash in momentum has possibly also bottomed out:

Overall GLAAM has not dived too much, though it will go down a bit further from here

and the extended EPS showing this for mid month over China

I'm seeing the potential here for another +EAMT event (to be honest Eric Webb spotted it first....)

In plain speak? The higher we can keep the base GLAAM state the better our chances of maintaining amplification with the jet pushed south, and even when the MJO enters phases less helpful in terms of wave position if amplification is sustained then our block gets trapped. Will bounce around - Tamara and Scott have flagged it as a possibility already - and then when AAM increases once again in line with a +EAMT event mid month (hopefully with the MJO pushing through the maritimes once again) we get a resurgence of the blocking signal just where we want it. If the block has ended up in a less favourable slot as the MJO sits in the IO (and that is an if and not a when) then this serves to bring it back where we want it.

The chances of extended cold are always slim, but the picture this paints is plausible and it could certainly happen. These teleconnective signals do not always stay in the trench as hoped for - sometimes Vadar and his two wingmen swoop down and shoot them back out - but right know we are in the trench and the exhaust port is not a million miles away. By this time next week we will have a good sense of where the block is going on the second pulse helped by vortex weakening or even splitting, and how these signals may be lining up.

It's all good.....so very very good....

PS - a little addendum while I think of it. Those that remember the amplification event of Dec 2010 will know that we all felt the timeline was finite. The signals were lining up to flatten out the pattern and following that spell we had a winter pretty much to forget afterwards. Not so this time. I do not know whether the amplification on the horizon will give us anything close to what happened then, but I do know that the signals are lining up in quite an opposite frame to those back in 2010. Dont forget the seasonals also saw a very blocked March....

 

Edited January 2 by Catacol

[WYorksWeather]

8 minutes ago, DCee said:

Great Post. And there are quite a few members going the milder route....

There are mild options beyond day 10, but still too much scatter to be sure which will win out. I think the models will struggle with mid-month until the UK high has actually formed, and we know where it is positioned. Small differences in the positioning will affect whether we see prolonged cold with multiple reloads and attempts at snow, or whether we see a gap open up which the Atlantic can blast through.

I wouldn't try to forecast anything beyond day 10, so I'd say high confidence in cold and frosty conditions prevailing in the short to medium term, but after that is anyone's guess.

[Eagle Eye]

Possibility of blocking through to Feb according to the EC46, background drivers also support this to an extent. Mainly the timing of fallings and rises in AAM being quick enough for built-up momentum to remain over our side of the Northern Hemisphere even when AAM is low. 

[Lukesluckybunch]

18z looks a better run for me..the angle of the ridge is better..also notice the finger of very cold uppers over the North sea!