Model Output Discussion - Early Summer and Beyond

[Blessed Weather]

Hi all. I've just moved several off topic posts over to the Spring 2022 Chat thread. As the title implies, this thread is for model output discussion. Plenty of other threads are available for general and local weather discussions. Thank you.

[summer blizzard]

I always get suspicious when we see zero comments but it's not a shock having seen the modelling today.

While the Euro does maintain a more balanced/average type pattern, the GFS goes full -AAM by day 7 onwards.

 

[Guest]

 

15 minutes ago, summer blizzard said:

I always get suspicious when we see zero comments but it's not a shock having seen the modelling today.

While the Euro does maintain a more balanced/average type pattern, the GFS goes full -AAM by day 7 onwards.

 

GFS has persistently been trending more unsettled for the last week heading into the final tercile of the month and slippery slope forecast in the ensembles. Not surprising especially when there’s a double bank holiday added into the mix in early June. 
 

Edited May 14, 2022 by Alderc

[kieranweatherfan]

And now the 06z gfs run shows a much warmer picture, in fact it’s almost completely different to last nights run! And a bit of an extension to the warmth this week, weds and Thursday in the south east potentially mid to high twenties 

[Snowy L]

I've seen this story play out too many times in winters and now it's happening in summer too:

1. Everything seems to be pointing to a block over the UK/east of the UK

2. A mystery factor isn't detected on the models until less than 5 days away which ramps up the Atlantic and destroys/waters down the block.

All I'm saying is the Atlantic is clearly stronger than the models would have you believe at days 6 onwards, so I wouldn't get hopes up about high pressure over the UK bringing wall to wall sun.

 

[Scorcher]

15 minutes ago, Snowy L said:

All I'm saying is the Atlantic is clearly stronger than the models would have you believe at days 6 onwards, so I wouldn't get hopes up about high pressure over the UK bringing wall to wall sun.

 

I don't agree with this- I don't think a 'strong Atlantic' is the reason for the changes we've seen to this upcoming spell.

It's not as though low pressure systems are going to come crashing through the UK in the next few days or that there is a train of Atlantic lows heading our way.

In this case the issue is simply the high being less robust and ending up slightly further east than the models initially showed.

Not exactly a raging Atlantic IMO.

[Snowy L]

 

2 minutes ago, Scorcher said:

I don't agree with this- I don't think a 'strong Atlantic' is the reason for the changes we've seen to this upcoming spell.

It's not as though low pressure systems are going to come crashing through the UK in the next few days or that there is a train of Atlantic lows heading our way.

In this case the issue is simply the high being less robust and ending up slightly further east than the models initially showed.

Not exactly a raging Atlantic IMO.

I'm not saying it's raging, it's simply stronger than the models try to portray in the medium term and it's strong enough to sink any pressure builds to our south and east.

Edited May 14, 2022 by Snowy L

[Scorcher]

2 minutes ago, Snowy L said:

 

I'm not saying it's raging, it's simply stronger than the models try to portray in the medium term and it's strong enough to sink any pressure builds to our south and east.

It's not strong at all though- it doesn't break through the block to the east even later next week.

[Methuselah]

30 minutes ago, Snowy L said:

All I'm saying is the Atlantic is clearly stronger than the models would have you believe at days 6 onwards, so I wouldn't get hopes up about high pressure over the UK bringing wall to wall sun.

How can you possibly know that: it hasn't even happened yet?

[Snowy L]

2 minutes ago, Ed Stone said:

How can you possibly know that: it hasn't even happened yet?

It's happened twice in the last few weeks and countless times this winter.

[Methuselah]

8 minutes ago, Snowy L said:

It's happened twice in the last few weeks and countless times this winter.

So, you don't know, then: you are just assuming it'll happen again because it's happened before?

[Snowy L]

54 minutes ago, Ed Stone said:

So, you don't know, then: you are just assuming it'll happen again because it's happened before?

Can you calm it down please? Yes I am assuming it will happen again because it has been a recurring pattern for a while now.

[Frosty.]

There’s lots to like about the Gfs 6z operational!…is it perfect?.. …nope, not by a long chalk!!! .. ..but it’s still jolly decent considering it’s still spring!!!!!!…the Gfs doesn’t quite reach summer……yet!  

 

Edited May 14, 2022 by jon snow

[Methuselah]

31 minutes ago, Snowy L said:

Can you calm it down please? Yes I am assuming it will happen again because it has been a recurring pattern for a while now.

[Frosty.]

I’m certainly no expert.. ..but I could swear the longer term ECMWF 0z ensemble mean looks kind of Azores ridgy?!.. ….it’s always risky / dangerous ️  for an amateur to try and give a professional opinion! …oh well..too late now innit.. pffffft!

 

 

 

Edited May 14, 2022 by jon snow

[Frosty.]

According to mystic Meg.. …I mean the CFS 0z.!!!!    …most of July May turn out nae so bad! ..hiccup…    

 

 

Edited May 14, 2022 by jon snow

[Methuselah]

26 minutes ago, jon snow said:

According to mystic Meg.. …I mean the CFS 0z.!!!!    …most of July May turn out nae so bad! ..hiccup…   

 

 

Where has all the 'nailed on' northern blocking gone!

[Frosty.]

Looking further ahead..oh, who am I kidding, I’m so much excited about spaceman winning the Eurovision Song Contest that I have completely overlooked the cfs 0z regarding august!.. and currently it looks decent…fingers crossed the cfs is as good as it thinks it is!!!!!  ..yes, he does look a bit like Thor!…hmmmmm 

 

Edited May 14, 2022 by jon snow

[Methuselah]

30 minutes ago, jon snow said:

Looking further ahead..oh, who am I kidding, I’m so much excited about spaceman winning the Eurovision Song Contest that I have completely overlooked the cfs 0z regarding august!.. and currently it looks decent…fingers crossed the cfs is as good as it thinks it is!!!!!  ..yes, he does look a bit like Thor!…hmmmmm 

 

Do not adjust your set!

 

[Eagle Eye]

37 minutes ago, jon snow said:

Looking further ahead..oh, who am I kidding, I’m so much excited about spaceman winning the Eurovision Song Contest that I have completely overlooked the cfs 0z regarding august!.. and currently it looks decent…fingers crossed the cfs is as good as it thinks it is!!!!!  ..yes, he does look a bit like Thor!…hmmmmm 

l

That first chart looks like a good troughing setup, I'll take one of these each week for the whole summer

[Frosty.]

I gorra say, there’s a lorra lorra things to like about the Gfs 12z operational next week in terms of warmth, especially across the sarf east corner.. !…it’s still spring remember.. we had no winter.. but yes, I can confirm…we’ve had a spring!!!!   

 

Edited May 14, 2022 by jon snow

[kieranweatherfan]

Yes some really decent spring temps shown by models for next week! Well above average could be touching 27° at times 

[Frosty.]

Shameless cherry picking here, the GEFS 12z has some potential on the cusp of the meteorological summer!!…if you don’t like it.. sue me! .. I particularly like that P29 plume!… ⛈…

 

[Frosty.]

Looking. at the ECMWF 12z operational, there’s plenty of warmth at times, especially towards the SE!…it’s not a settled outlook but for sure, there is some settled weather, especially later, again concentrated further s / se but there is some heavy showers / thunderstorms in the forecast during the days / nights ahead, again, with emphasis further s / se…at least it has a summery vibe about it..again, mainly further s / se…you can see where I’m going with this can’t you? …wish I lived in the SE! ⛈

 

 

[Singularity]

10 hours ago, summer blizzard said:

I always get suspicious when we see zero comments but it's not a shock having seen the modelling today.

While the Euro does maintain a more balanced/average type pattern, the GFS goes full -AAM by day 7 onwards.

 

As I said before, this isn't what -AAM directly corresponds to in late spring and early summer. An unsettled UK outcome with -AAM depends on there being at least a weakly negative NAO setup in play. Without that, the Azores High tends to extend at least a little way across the UK.

While I tend not to take its predictions very seriously, GFS actually predicts slightly +AAM through to 20th.

http://www.atmos.albany.edu/student/ventrice/real_time/AAM.png

AAM has indeed climbed impressively in recent times, taking us out of what had been a well entrenched -AAM regime so far this spring. This change is evident in the Azores High being greatly diminished in the week ahead. Instead there's a broad low to our west that reaches quite far south, which is more of a Nino-like setup under a neutral or positive NAO.

With the oceanic La Nina going from strength to strength, AAM is bound to tumble away again sooner or later. Then, the sNAO (summer NAO) state will be crucial for what happens in June. Most seasonal models are banking on ocean-atmosphere feedbacks over the N. Atlantic sustaining a +sNAO and forcing the re-inflated Azores High to extend well to the ENE or NE, resulting in an anomalously warm/hot and dry June for a large part of Europe, including southern UK. That's what happened in 2018 when AAM cascaded during the 2nd half of June.

Should the feedback cycle instead break down, the Azores High will be more inclined to focus further west (which as demonstrated in June 2010, can be half decent in early summer, albeit mainly for southern parts of the UK, if you can tolerate chilly starts to the day) or, if the sNAO flips negative, northwest (June  2007 style). We've seen GFS display its usual enthusiasm for such a switch-flip in the later stages of a few recent runs but given how often we've seen a +sNAO self-reinforce in recent years, it seems the lowest likelihood outcome at this stage (versus neutral or positive sNAO).

As the summer goes on, a +sNAO tends to force the Azores high to extend more E than ENE or NE, making a changeable westerly pattern more likely by August. In 2018 that shift occurred unusually late, during the 2nd half of Aug, perhaps owing to the exceptional strength of the +sNAO setup that season.

This is why, very broadly, La Nina summers tend to slide gradually downhill (or climb uphill if you like it cool & unsettled) over time.

An El Nino summer tends more settled instead, but while the early summer tends to be more unsettled, that's often with setups like we're now looking at next week, so plenty of warmth can occur and of course there's a lot of scope thunderstorms. Hence an El Nino is preferred for the summer season by the majority of the weather community. La Nina ones can be impressively hot and dry when the NAO is positive, but some find that a bit boring.