Model output discussion - Christmas approaches

[Battleground Snow]

Slept through the ECM and gfs 06z after a few too many Xmas shandies, knew it was going to be action packed with 200+ posts to catch up on.

Mjo updates, and the GFS is starting to concede to the ECM, albeit still quite different,

I'm trying to recall a period where it has been in phase 7 for so long.

Feb 18 it was very amplified, but went through phase 7 and 8 very quickly, and resulted in eastlerlies flying way out into the Atlantic. We have decent amplitude right now, which is probably why the models are stuggling to resolve the strength of the block, as seen by the small variations from run to run. Like others have said longer time is 7 is great for destroying up the trop vortex and eventually the strat vortex.

I see the American pros on twitter almost urging the MJO to get to phase 8, as it sets them up for a very cold pattern with a west based -NAO, they seem to be talking about late January for this too happen. 

The east Pacific really is quite cold, you would think this will interfere with the MJO once it gets into 8.

Lastly the AO really tanks on some runs, the recovery of this will maybe dictate how long we remain in the cold game for

 

Edited December 18, 2021 by Battleground Snow

[Duane S.]

There does seem to be even more complexities and nuances involved in this evolving set up than usual. Notwithstanding it is hardly ever bleeding straight forward getting a fairly uk wide cold and snowy period !

MJO looks absolutely fab for us still. @Battleground Snow has pretty much added everything I was just going to about it, including the ‘problem’ with the 2018 very high amplitude P7 event, which retrogressed our high N and W at warp speed! Amazing few days but over quite quick.

For me, I’m just looking at improved ridging southwards from our old retrogressed high. That aspect has improved over the past 24 hours, but a further minor tweak will just add a bit of insurance and stack the dice for a more prolonged spell.

[kold weather]

Wonderful 06z GFS, the ensembles are decent as well, but obviously with the huge caveat that it wouldn't take much of a shift in either placement or orientation to turn a possibly snowy pattern into a flooding pattern.

[Scott Ingham]

5 hours ago, Kasim Awan said:

I can see it going further south yet tbh could end up a channel low & we draw in streamers off north sea instead.

its certainly heading in the direction we discussed a couple of days ago! 

itd funny to see the mood go up and down on indiviual runs!

[MATTWOLVES 3]

2 hours ago, Ed Stone said:

Ah, yes. The Avatar of Dorian Grey?!

Are you saying for every sin I commit the image in my photo becomes more and more horrid Pete! At least you said Dorain grey..and not 50 shades of.....

Some cracking ensembles from the 6z...only gonna post a few...but wow you've got to say the vortex looks along way from home and out of sorts big time.

It's just splendid to see such and encouraging Northern Hemisphere at this time of the year...surely to god this is one of those winters that should deliver in a bigger way than normal.

Know dramas for the 12s folks get ya shopping done and keep ya missus happy...ya don't want an Xmas of moaning  

[Kasim Awan]

20 minutes ago, Scott Ingham said:

its certainly heading in the direction we discussed a couple of days ago! 

itd funny to see the mood go up and down on indiviual runs!

I can see fluctuations in latitude on runs within a day period whilst each day overall trends south.

Edited December 18, 2021 by Kasim Awan

[Lukesluckybunch]

1 minute ago, Kasim Awan said:

I can see fluctuations in latitude between daily runs whilst each day overall trends south.

hello kasim, yes agree with you,excited for 12z have feeling they gonna be great!

[Kasim Awan]

1 minute ago, Lukesluckybunch said:

hello kasim, yes agree with you,excited for 12z have feeling they gonna be great!

We're still far from 100% imo, still 70% ish..

[Lukesluckybunch]

1 minute ago, Kasim Awan said:

We're still far from 100% imo, still 70% ish..

im asking for 2 things cold bought forward a bit,and that southwards correction.on the 6z i mentioned about the lows merging around northern ireland scotland,ideally we want them combining to the south of the country towards france a quicker route to the cold and far cleaner.a big ask i know

[Kasim Awan]

4 hours ago, sheikhy said:

Better head out for a run before the 06z comes out!!be back in 45 mins!!!

The Sheikhy 10z run -

[bluearmy]

Although it wouldn’t really mean a great deal, it would be nice to see Ukmo day 4/5 strengthen the ridge ahead of the trough and therefore disrupt it somewhat days 5/6 (and to absorb that shortwave into the scandi trough) 

would be a decent day to have all the ops on the same page for wed through Friday at least. (Assuming that’s good for a widespread white Xmas !) 

Edited December 18, 2021 by bluearmy

[geordiekev]

ECM snow depth charts whilst over egged don't look too bad for midnight on Boxing Day & the following day. A lot of focus on the big day, when in reality many will be travelling to families and with kids off school any hit after Christmas Day will be enjoyed just the same once they're bored of raft of toys

[Stu_London]

A nice 06z operational to look showing a prolonged cold spell pretty much nationwide from the 27th.

This could be brought forward a bit if the low slides a bit more. On the flip side still nearly half of the ensembles do not make anything of the cold spell at all. 

Starting with today's 12Z suite we are in for 48 hours of a rollercoaster. I would expect the pattern to resolved by Monday, with any individual features to firm up later in the week. 

So - where's your money?

I would go: -

25% decent (4 days plus) cold spell with most or all of uk included.

40% some sort of regional event with perhaps the south missing out

35% diddly squat.

 

[Nick B]

2 hours ago, Kasim Awan said:

Yes, but I would like to see more concrete research on the causal relationship between hadley cell expansion and uk winter synoptics such as the rate of failed initiation of cold with varying intensities of Hadley cell.

You'd be able to collate data on number of cold episodes. Our gut would tell us the expanded Hadley cell has been a strong factor. However, a 'failed initiation' from what point in time and from what kind of starting point? The various models are simply calculating from a starting point of right now and forecasting out to a future event which hasn't yet occurred, so what has initiated? Also, models have received numerous upgrades (usually but perhaps not always improvements

[Nick B]

Just now, Nick B said:

You'd be able to collate data on number of cold episodes. Our gut would tell us the expanded Hadley cell has been a strong factor. However, a 'failed initiation' from what point in time and from what kind of starting point? The various models are simply calculating from a starting point of right now and forecasting out to a future event which hasn't yet occurred, so what has initiated? Also, models have received numerous upgrades (usually but perhaps not always improvements) so we don't have a constant tool against which to measure the variance of outcomes over time. Could be problematic from that point of view.

 

[Jason M]

1 minute ago, Stu_London said:

A nice 06z operational to look showing a prolonged cold spell pretty much nationwide from the 27th.

This could be brought forward a bit if the low slides a bit more. On the flip side still nearly half of the ensembles do not make anything of the cold spell at all. 

Starting with today's 12Z suite we are in for 48 hours of a rollercoaster. I would expect the pattern to resolved by Monday, with any individual features to firm up later in the week. 

So - where's your money?

I would go: -

25% decent (4 days plus) cold spell with most or all of uk included.

40% some sort of regional event with perhaps the south missing out

35% diddly squat.

 

A fair assessment in my view. For us I reckon its nothing but rain and watching reports from elsewhere of snow falling. Recent years have not been good to us in the SE as Kent and Essex in particular have missed out on almost every occasion. I think its a case of assume the worst and be happy if it works out better.

[Lukesluckybunch]

ICON rolling out now

[Rush2019]

1 hour ago, nick sussex said:

The government is fully behind the GFS 06 hrs run as it could stop households mixing ! Snow induced lockdown !

Yes, nationwide ice-olation. LOL

[swfc]

1 minute ago, Rush2112 said:

Yes, nationwide ice-olation. LOL

[Ali1977]

Early at T60 but the block is better and more rounded - Atlantic delayed too - should aid the slider 

Edited December 18, 2021 by Ali1977

[Lukesluckybunch]

slight shift north at 90 on ICON

[Ali1977]

Just now, Lukesluckybunch said:

slight shift north at 90 on ICON

It’s not north, it’s just coming in slower I think 

[Paul]

With the main 12z's about to roll, I'm going to lock this one to start a fresh thread (and slightly changed thread layout). The new one is here:

 

Edited December 18, 2021 by Paul