Model output discussion 9th April onwards

[Methuselah]

13 minutes ago, MATTWOLVES said:

Ok guys as your well aware I'm probably the Worlds best cold chaser! I know what it's like to see many cold snaps set up,before failing! I can't understand the frustration with the current output! Yes its mixed with temps,average at best...But please remind yourself that it's still mid May,and this current situation will have know barring on how Summer proper will pan out! 

I've been saying for some time that it's going to be the final part of May before we see improvements coming along,and nothing I've seen as changed my take on that! The hints from GFS ens further sown the line show this,and also Exeter giving strong hints of a more settled outlook towards late month.

And folks this new Indian varient of covid is of much more concern than the current poor weather outlook is.

Let's hope and prey we all get through this in one piece! The weather will sort itself out im sure off.

Keep well and enjoy the showers

 

You're back!

[Cheshire Freeze]

2 hours ago, Backtrack said:

Dropped a Tweet to Aidan McGivern earlier (Met forecaster). He tells me they are seeing signs of higher pressure dominance towards the beginning of June in the longer range models. 
 

 

Issue is, every time we see hints of Azores ridging, as it gets closer the HP ends up further N than was initially anticipated. I mentioned this a few weeks back.

It will warm up eventually though, it has to. 

[Frosty.]

3 hours ago, Earthshine said:

Where is the Azores High?!

In the Azores?  

[damianslaw]

Good post from Tamara above. Suggests we may see a change as we move into June courtesy of rising AAM, this having the effect of pushing the long wave atlantic trough further eastwards, allowing for mid atlantic ridge develop to move across the UK and then importantly to our east with the jetstream tracking further to the north.

Seasonal wavelengths as we move into June tend to see the jetstream pushed further north away from a more southerly position during the Spring.. the summer base state tends to bed in around the Solstice, important to keep an eye on developments through first half of June rather than second half of May for an indication of likely direction of travel for the remainder of the summer as a whole. Examples of switches in state happened in 1995 and 2013 with much improved conditions by the latter part of June. May have to be more patient this year than a number of recent ones for our first dose of sustained warm settled weather.. but hopefully once arrives it will be a recurrent theme through the rest of the summer rather than a couple of 3 day plume events interspersed with westerly wetness.

[minus10]

Difference between Gfs6z and 12z at 219 is fairly substantial.

Is it possible that the low pressure being much further east on the 12zrun could prevent the high linking up with the Greenland high causing an Atlantic ridge and thus following NEs on the 6z? (or wishful thinking?) Still to be decided......

[Frosty.]

I’m getting out the bunting, there’s a warm day on the Gfs 12z op!  .and it hasn’t even finished yet!..oh my.....there could be more joy ahead..19c..66f..I’m so much excited..not..I may move to Portugal to get away from good old Blighty’s crap climate!  ?!  

 

Edited May 15, 2021 by Jon Snow

[thestixx]

2 hours ago, Tamara said:

Many of the worst summers have seen collapsing momentum budgets within the atmosphere coinciding with these seasonal wavelength switches. This Spring/Summer switch suggests rather more the opposite trend

This sentence is music to my ears. 

 

Thanks once again for an enjoyable and insightful post. Hope you have a safe and enjoyable journey sunwards

[Frosty.]

The Gfs 12z op didn’t really improve..that’s it..I’ve had enough..I’m moving to Portugal..oops that’s Friday..I don’t care, I’m still going!!!!.   

Edited May 15, 2021 by Jon Snow

[Guest]

Desperate times when you look at the GFS 12z and think ‘Yep I’ll take that compared to some of the complete and utter drivel seen in the last 24hrs’ 

looked less bad, hopefully not a milder outlier

[minus10]

36 minutes ago, minus10 said:

Difference between Gfs6z and 12z at 219 is fairly substantial.

Is it possible that the low pressure being much further east on the 12zrun could prevent the high linking up with the Greenland high causing an Atlantic ridge and thus following NEs on the 6z? (or wishful thinking?) Still to be decided......

Well, at least the 12z  has prevented that direct northerly. 

Hopefully this can be a trend to bring some more summer like weather......

[I remember Atlantic 252]

UKMO v GFS for Thursday! I'm team UKMO! but will it be right?

[Cheshire Freeze]

1 hour ago, damianslaw said:

Good post from Tamara above. Suggests we may see a change as we move into June courtesy of rising AAM, this having the effect of pushing the long wave atlantic trough further eastwards, allowing for mid atlantic ridge develop to move across the UK and then importantly to our east with the jetstream tracking further to the north.

Seasonal wavelengths as we move into June tend to see the jetstream pushed further north away from a more southerly position during the Spring.. the summer base state tends to bed in around the Solstice, important to keep an eye on developments through first half of June rather than second half of May for an indication of likely direction of travel for the remainder of the summer as a whole. Examples of switches in state happened in 1995 and 2013 with much improved conditions by the latter part of June. May have to be more patient this year than a number of recent ones for our first dose of sustained warm settled weather.. but hopefully once arrives it will be a recurrent theme through the rest of the summer rather than a couple of 3 day plume events interspersed with westerly wetness.

I’ll be shocked if we see HP to our E for any significant amount of time this summer. Pretty much every long range model places a mean HP anomaly just to our west. 
 

Also important to remember that any rising AAM signature is no guarantee of HP settling over or to the E of the UK (which is where heat lovers would want it).

Remember, 2007 was a highly amplified/buckled jet pattern...it didn’t improve until the jet flattened later in summer (towards August)...when AAM went negative?

We’re best off waiting to see where we are come early June. If we’ve settled down then early summer could be useable and decent. If things are still unsettled then I think we could be looking at a cool, wettish summer overall. 

Edited May 15, 2021 by CreweCold

[Frosty.]

The GEFS 12z mean continues to improve longer term...how many times have I said that?..I’ve lost count!...anyway..maybe one of these perturbations will be our lucky number?!...roll on summer..yes, let’s not forget, it’s still very much spring for another....  16 days.!!

 

 

[Djdazzle]

44 minutes ago, CreweCold said:

I’ll be shocked if we see HP to our E for any significant amount of time this summer. Pretty much every long range model places a mean HP anomaly just to our west. 
 

Also important to remember that any rising AAM signature is no guarantee of HP settling over or to the E of the UK (which is where heat lovers would want it).

Remember, 2007 was a highly amplified/buckled jet pattern...it didn’t improve until the jet flattened later in summer (towards August)...when AAM went negative?

We’re best off waiting to see where we are come early June. If we’ve settled down then early summer could be useable and decent. If things are still unsettled then I think we could be looking at a cool, wettish summer overall. 

I’d be more shocked If the LRF’a are actually correct! They may be correct, but an average to warm summer is just as likely as a cool unsettled one.

And even if we do end up with that, you wouldn’t bet against a few hot / very hot spells.

[Tamara]

24 minutes ago, CreweCold said:

I’ll be shocked if we see HP to our E for any significant amount of time this summer. Pretty much every long range model places a mean HP anomaly just to our west. 
 

Also important to remember that any rising AAM signature is no guarantee of HP settling over or to the E of the UK (which is where heat lovers would want it).

Remember, 2007 was a highly amplified/buckled jet pattern...it didn’t improve until the jet flattened later in summer (towards August)...when AAM went negative?

We’re best off waiting to see where we are come early June. If we’ve settled down then early summer could be useable and decent. If things are still unsettled then I think we could be looking at a cool, wettish summer overall. 

Boa noite

A few things:

There is no prediction in that post for sustained ridging over or to the east of the UK/NW Europe for the summer as a whole - indeed that post was not a  definitive actual forecast at all. Merely an assessment of probabilities that balance the reasonable chances of a mid latitude pattern against any pattern dominated by unstable polar profile and supressed jetstream. The latter being a combination that is perpetuated  by a low angular momentum regime allied to easterly QBO phasing.

The explanation and differences between the regimes were explained in detail and should not leave much ambiguity. Angular momentum collapsed on cue in early summer 2007 allied to rapidly increasing QBO feedbacks assisting downwelling of blocking mechanisms into the troposphere at higher latitudes.  Current indications suggest the opposite trends in the atmosphere for the start of summer and no descent into a significant La Nina event, such as happened in 2007, to drive such a pattern further forward. Rather, the atmosphere is being led by an adjustment a little further eastwards in tropical convergence which should aid a rossby wave pattern that allows sufficient eastward ridging of the Azores high to provide some settled warm summer spells for NW Europe.

An unsettled start to June would mean nothing at all for the greater summer either. Its all about the direction of travel of these wind-flow budgets and how they respond to seasonal wavelengths. Its not anything black and white in terms of x+y =.

This is unlikely to be any typical El Nino led summer pattern where the Azores high actually plays a lesser part, and ridges across Europe and Scandinavia fully dominate and set against thundery trough interplay to the west, but  more a half way house position that is simply aided by convective convergence in the tropics being far enough east to discourage Nina-esque dominant Atlantic blocking and downstream trough. However, once again to balance that out, when talking about seasonal probabilistic, it certainly doesn't rule out plume scenarios either and it would be quite surprising if these didn't crop up at some stage. Especially, as the previous post intimates, if we see active tropical convergence trying to push into the Pacific through the greater part of the summer

At the most 'optimistic' end of the scale, a summer such as 1995 after all benefitted from an eastward displaced convection standing wave arrangement in the tropics within the context of the legacy of a weak La Nina regime. Though this summer may indeed struggle to reach those sorts of levels - at least for NW Europe. However, as stated, this is all about probabilities at range, and not about definitive predictions whether they are, or are not, driven by preference biases.

Obrigada. Cumprimentos.

 

 

[Frosty.]

I’m going to be diplomatic about the ECM 12z operational.. ..it’s nothing like as cold as yesterday evenings run, and eventually the trough gets squeezed from all sides and shrinks away to almost nothing by day 10 with pressure slowly rising..thank god it’s still spring and we are not eating into the meteorological summer! ...on a more serious note, this late spring is no laughing matter, it’s pathetic..hopefully June will bring a BIG change..for the better!  

 

 

[Frosty.]

Am I the last man standing? ..anyway, tonight’s ECM 12z ensemble mean eventually improves towards late May, becoming quite ridgy from the Azores and temperatures don’t seem as though they would be too bad either (longer term)!...hopefully the change in season will bring a change in the weather, it often happens that way!  

Edited May 15, 2021 by Jon Snow

[ICE COLD]

Friday could be pretty stormy for late May

[Don]

7 hours ago, Backtrack said:

Dropped a Tweet to Aidan McGivern earlier (Met forecaster). He tells me they are seeing signs of higher pressure dominance towards the beginning of June in the longer range models. 
 

 

Problem is the potential for higher pressure is continuing to be pushed back, i.e. at the start of May we were looking at mid month and now we are half way through, we are looking towards the start of June.  We typically see this in winter with cold/snowy synoptics being pushed back.  We are clearly in a cooler pattern currently, but the question is, how long will this last?  However, far too early to give up on summer at this point and as I said earlier, I'm sure the coming summer will have its moments for heat lovers, even if not sustained!

[Britneyfan]

We will deffo get some above average days over summer, even this month I’ve had a few days above average so just depends how hot it can get

[Man With Beard]

2 hours ago, Tamara said:

Boa noite

A few things:

There is no prediction in that post for sustained ridging over or to the east of the UK/NW Europe for the summer as a whole - indeed that post was not a  definitive actual forecast at all. Merely an assessment of probabilities that balance the reasonable chances of a mid latitude pattern against any pattern dominated by unstable polar profile and supressed jetstream. The latter being a combination that is perpetuated  by a low angular momentum regime allied to easterly QBO phasing.

The explanation and differences between the regimes were explained in detail and should not leave much ambiguity. Angular momentum collapsed on cue in early summer 2007 allied to rapidly increasing QBO feedbacks assisting downwelling of blocking mechanisms into the troposphere at higher latitudes.  Current indications suggest the opposite trends in the atmosphere for the start of summer and no descent into a significant La Nina event, such as happened in 2007, to drive such a pattern further forward. Rather, the atmosphere is being led by an adjustment a little further eastwards in tropical convergence which should aid a rossby wave pattern that allows sufficient eastward ridging of the Azores high to provide some settled warm summer spells for NW Europe.

An unsettled start to June would mean nothing at all for the greater summer either. Its all about the direction of travel of these wind-flow budgets and how they respond to seasonal wavelengths. Its not anything black and white in terms of x+y =.

This is unlikely to be any typical El Nino led summer pattern where the Azores high actually plays a lesser part, and ridges across Europe and Scandinavia fully dominate and set against thundery trough interplay to the west, but  more a half way house position that is simply aided by convective convergence in the tropics being far enough east to discourage Nina-esque dominant Atlantic blocking and downstream trough. However, once again to balance that out, when talking about seasonal probabilistic, it certainly doesn't rule out plume scenarios either and it would be quite surprising if these didn't crop up at some stage. Especially, as the previous post intimates, if we see active tropical convergence trying to push into the Pacific through the greater part of the summer

At the most 'optimistic' end of the scale, a summer such as 1995 after all benefitted from an eastward displaced convection standing wave arrangement in the tropics within the context of the legacy of a weak La Nina regime. Though this summer may indeed struggle to reach those sorts of levels - at least for NW Europe. However, as stated, this is all about probabilities at range, and not about definitive predictions whether they are, or are not, driven by preference biases.

Obrigada. Cumprimentos.

 

 

Gosto muito de esta previsao. Obrigado. It's good to have some hope that there is even the possibility of an upturn in weather fortunes! My fear is it will take so long to materialise that we end up with little time to exploit it. Ridges are still getting drawn to the NW, but if we can lose the north sea trough anomaly then eventually we'll be in business.

[Cheshire Freeze]

2 hours ago, Djdazzle said:

I’d be more shocked If the LRF’a are actually correct! They may be correct, but an average to warm summer is just as likely as a cool unsettled one.

And even if we do end up with that, you wouldn’t bet against a few hot / very hot spells.

We'll have some useable periods this summer- that I'm pretty certain off. I don't actually think it'll be all that wet either. I do believe proper heat will be in short supply though on a widespread or sustained basis. If I was to put my money on a predominant pattern it would be one which interchanges between drier and warmer and cooler and wetter; little deviation towards the extremes.

As ever, we'll see.

[Mike Poole]

Well I disagree with @CreweCold, no surprise there as it is summer we’re talking about.  I think there is the prospect of quite a significant shift to heat, but not for a few weeks, I’m going on the GloSea5 outer quintiles plot, showing quite a few members developing favourable heights for that, ridging from the Azores there:

Meantime, the JMA T264 seems to be showing the way…

But I’m not seriously expecting many charts like this in the reliable for a couple of weeks yet, to be honest.

[Guest]

23 minutes ago, Britneyfan said:

We will deffo get some above average days over summer, even this month I’ve had a few days above average so just depends how hot it can get

Depends on where you are, we’ve not within 1c of average yet this month. But yes given we are supposedly in a warming climate and we’ve onlY managed average on about 7 or 8 of the last 44days I think we’ll hopefully gets lots of at least average days in the next 16weeks.

[Don]

8 minutes ago, CreweCold said:

We'll have some useable periods this summer- that I'm pretty certain off. I don't actually think it'll be all that wet either. I do believe proper heat will be in short supply though on a widespread or sustained basis. If I was to put my money on a predominant pattern it would be one which interchanges between drier and warmer and cooler and wetter; little deviation towards the extremes.

As ever, we'll see.

And that's exactly what I hope this summer will deliver.  Those insufferable Spanish plumes we had to endure during the last couple of summers can do one!