Model Output Discussion - Into Summer 2020.

[Leo97t]

ECM is different to the UKMO GFS. I wouldn't take it seriously I think its been almost as awful as the gfs recently. 

[Methuselah]

11 minutes ago, Scorcher said:

Are we looking at the same charts? 'Awful' is not a word I would use to describe that run.

It's not what we want to see in an ideal world but at least there is warmer air in place next week- better than this cool rubbish we've endured this week.

There will be day to day variations so most of us will have some dry periods next week, and where the sun emerges it will be warm.

I couldn't agree more, @Scorcher: I work outside, so I'd love to be able to pull weeds, from soil that's not like concrete...And, as it's almost certainly going to be on the warm side too (that is what all the models are suggesting, isn't it?) crawling through wet mud won't be a problem, either. Bring it on!

[Guest]

49 minutes ago, Tamara said:

 

The fall-back of pessimism and what can go wrong will go wrong is a very simple option any of us could choose, but it isn't scientific.  The first caption from a previous post on Monday is a reminder of realistic expectations and cuts through the very easy option of trying to be wise after the event  

NWP has duly evolved down the path of juxtaposing the divergence of those two signals as suggested in that post the other day. It makes comparing and contrasting the blends of solutions being advertised a very precarious process. On that basis there is little value or constructive purpose, as ever, demonising one model or another - there have been leads in ECM modelling that have deviated at times, as much as the GFS operational. No numerical model is (ever) bullet proof and that extends to the UKMO et al as well.' Furthermore, guidance from ensemble and cluster data can also be culpable - it is possible to have good agreement for a wrong solution as much as sometimes a less favoured solution can gain support with time. It is the diagnostic that matters and which ultimately decides and in that sense it doesn't matter which model is proved "correct".

My own position is, as always, less interested in the computer model "hugging" and more interested in seeing how they resolve the diagnostic. This is a process that takes longer than 6/12/24 hours on an intra day basis but too often evolves over a few days at a time. Since the highlighted post was made on Monday, they have indeed started to "see" the fork(s) in the road according to the wind-flow momentum budget and the truth, as anticipated, remains very finely balanced.

Global atmospheric angular momentum since the end of last week has slipped into slightly negative territory and wholly consistent with the change of weather as discussed in detail for some time

it is worth looking at some other diagnostic proxies.  Irrespective of lower angular momentum, one of the leading atmospheric proxies, the Southern Oscillation index, which gives a guide as to pressure differential across the Pacific, remains very neutral and no uptick in sustained positive indices to suggest fast and progressive coupling of La Nina in the atmosphere. There is not the kind of negative PDO signal upstream suggested to "lock in" a retrogressed pattern. Nonetheless, it is becoming clear that something of an upstream switch is occurring that looks like it might make it more difficult to achieve downstream ridging with the sort of ease that was demonstrated during the Spring

 

 

 

Furthermore however, the QBO continues erratic progress and only very weakly negative easterly - and continues to show little enthusiasm for rapid down-welling of easterly phase such as happened in a summer like 2007,..and deepen such attempted coupling and stratospherically induce an unstable tropopause layer (higher latitude blocking). In that sense, the suggestion of a more traditional westerly pattern in the further outlook is not necessarily a bad thing in terms of the Azores High relationship with lower heights towards Greenland. However, any retracted Azores ridge is not going to lead to classic warm summer weather, albeit relatively better than polar blocking and southerly tracking lows.

QBO Jan to May 2020:  Jan  -2.51 Feb  -3.20  Mar -4.36  Apr  -5.03  May  -4.86  . Very weak and erratic at present.

The pattern is re-set as suggested some 10 days back. However, the full re-set to Scandinavian High and the trough backed comfortably west was achievable under the May (higher angular momentum) wavelength. A further switch into early summer wavelength and less forward momentum in the atmosphere to assist downstream ridging is proving to make this more difficult to achieve in June.  A resurgence of the Azores ridge across the UK in the extended period is subject to a rise in angular momentum tendency and the GWO re-orbiting accordingly back to (rising tendency) Phase 4.

This remains quite possible but again, subject to change not just based on the uncertain fulcrum of the medium term, but also to the susceptibility of keeping Azores ridging held back and pressure lower downstream if momentum stays flat and the GWO doesn't arrive back at Phase 4.

That particular question is beyond the first corner. The fence for sitting on is moi But objectively, that seems intuitive at present. .

Maybe not scientific and but having watched the models for nearly 20years and I know when to spot a potential pattern that despite what everything else says. I love the weather and I love seeing, feeling, observing it (although I do completely detest our climate) Working 14hr days for a life sucking bank I don't have time to learn and bring myself to anywhere near the ability and knowledge you clearly have but I really wish you wouldn't use all that ability to then jibe or poke at people who don't have the knowledge you do, which you do at times, its not cool. If it wasn't for that I would enjoy reading your posts even more than I do. 

[Guest]

Analysis of ECM this morning is not good viewing, again temps in my neck of the woods don't reach 20C through the entire run. UKMO looks as though it could get a little stormy on day 6 and GFS again appears to be the most optimistic of the gang in the short term however its ensemble pack has embarrassingly back-tracked from the settled/warm spell to something distinctly more beige!

[mb018538]

 

ECM op didn’t look great at face value - and looks worse in the ensembles. Too unsettled again. The mean is actually fairly decent at day 9/10, so it’ll be interesting to see the clusters later on.

[Guest]

1 hour ago, Leo97t said:

ECM is different to the UKMO GFS. I wouldn't take it seriously I think its been almost as awful as the gfs recently. 

It's a big outlier, too.

[northwestsnow]

Thanks for the update Tamara..

Im sure i speak for the vast majority in here by saying your extensive updates on the background drivers etc are thoroughly appreciated.

[chapmanslade]

1 hour ago, Leo97t said:

ECM is different to the UKMO GFS. I wouldn't take it seriously I think its been almost as awful as the gfs recently. 

Is there any chance this sort of post could be given a miss by all forum members? It is pointless bashing mathematical models as 'awful' or 'rubbish'. They are what they are and we have had maybe 20 posts in the last 2 or 3 days that have said a similar thing about every model - so in effect they are all rubbish so why bother looking at any of them and go back to the seaweed. 

The ECM run splits from the ensemble members / mean at day 7. What on earth is anybody expecting from a weather model at this time and resolution ? As has been posted earlier this morning verification stats have not changed significantly so there is no story - it is life as normal. 

Edited June 11, 2020 by chapmanslade

[Leo97t]

2 minutes ago, chapmanslade said:

Is there any chance this sort of post could be given a miss by all forum members? It is pointless bashing mathematical models as 'awful' or 'rubbish'. They are what they are and we have had maybe 20 posts in the last 2 or 3 days that have said a similar thing about every model - so in effect they are all rubbish so why bother looking at any of them and go back to the seaweed. 

The ECM run splits from the ensemble members / mean at day 7. What on earth is anybody expecting from a weather model at this time and resolution ? As has been posted earlier this morning verification stats have not changed significantly so there is no story - it is life as normal. 

You're incorrect. 

The model is different from the UKMO and GFS within 100 hours. Given the UKMO has been far and away the most accurate recently and even the GFS is agreeing with it I find my post apt. The ECM op is not supported by its ensemble. I think its entirely reasonable too dismiss it - and I don't think its fair to dismiss a post you don't agree with in such fashion!

I expect the mean has got the Azores high nosing back in around day 9 nailed however - watching the 10 day trend from the met supports this - unsure of how strongly this will occur but finally somewhat of a normal pattern

[Snowy L]

1 hour ago, Scorcher said:

Are we looking at the same charts? 'Awful' is not a word I would use to describe that run.

It's not what we want to see in an ideal world but at least there is warmer air in place next week- better than this cool rubbish we've endured this week.

There will be day to day variations so most of us will have some dry periods next week, and where the sun emerges it will be warm.

That ECM is horrific, the low stays on top of us until merging with the Atlantic to set up a neverending sliding jet. What is this desperation where we are meant to be grateful just to see rain and 20C instead of rain and 15C? Thankfully it is a bad outlier in terms of pressure.

[Mark Us]

I dont think ECM is that much of an outlier. Ensemble for western-netherlands, which would be quite the same for the UK I guess...

 

[sheikhy]

Well nothing for me to really say about gfs this morning except i been banging on about how useless the model is and its just proved it again this morning!!if it cant get a forecast right at just 2 or 3 days out then in my opinion the model needs to be pulled back as harsh as it sounds!!every now and then for the models to be wrong is normal but for it to happen a lot like the gfs and at very short range then you know that model needs to be worked on seriously!!anyway ecm continues to look same as 12z yesterday and ukmo looks the same as well!!no wash out but nothing like the really dry sunny weather that was forecast the other day!!

[Tamara]

1 hour ago, Alderc said:

Maybe not scientific and but having watched the models for nearly 20years and I know when to spot a potential pattern that despite what everything else says. I love the weather and I love seeing, feeling, observing it (although I do completely detest our climate) Working 14hr days for a life sucking bank I don't have time to learn and bring myself to anywhere near the ability and knowledge you clearly have but I really wish you wouldn't use all that ability to then jibe or poke at people who don't have the knowledge you do, which you do at times, its not cool. If it wasn't for that I would enjoy reading your posts even more than I do. 

I am sorry you think that. No expert in my case - just an ordinary member trying to apply some balance whilst at the same time also trying to delve a bit deeper into the science. Which isn't always an easy thing to do. Mistakes however, are the best way to learn.. Irrespective of assumed knowledge, everyone makes mistakes. This is a good thing, and is rewarding for the next time. 

It is true though in my opinion that it can be helpful to step back from reactive judgements stemming from responses to NWP at face value - and instead let answers to questions evolve in their own time.  This is a good way to starting to understand the (apparent) curveballs that occur with NWP output.- and in turn leads to greater evenness in the nature of response.

That is intended as a helpful suggestion, albeit as constructive criticism, but in no way undermines the contribution of anyone

Back to the modelling itself, and more especially the diagnostic process (as I keep referring to it)

The deterministic tropical convection forecasts are steeping the convection signal in the Indian Ocean.

Calculated tendency of angular momentum refers to an aggregate of torque responses within the atmospheric circulation. Wind-flow torques are created by the turning force applied to the jet stream due to deflections in wind-flow speed and trajectory within the atmospheric circulation. These can decelerate (negative torque) or accelerate (positive torque) wind-flow according to where they occur in the tropics and extra tropics. The diagnostic plot shows considerably tanking negative torque inertia propagating from the tropics to extra tropics - as manifested towards the active convective signal across the Indian Ocean and the suppression of convection across the Equatorial Pacific Ocean

 

The tropical signal rooted in the Indian Ocean will continue to promote easterly (negative) inertia across the Pacific with the standing wave relocated further upstream in the tropics - and this in turn re-configures (retrogresses) the amplified rossby wave response further downstream. In both summer 2018 and 2019,  momentum actually fell during June and this is not uncommon as linked to the Indian monsoon season which typically begins around this time .

What matters is how the Walker cell behaves as interpreted as differential between the low and high frequency tropical signals. Both those summers also saw a convection convergence signal within the Pacific which interfered with the low angular momentum forcing within the atmosphere and assisted greater eastward ridging of the downstream sub tropical (Azores) ridge - most especially of course in 2018 which saw a steady progression from a weak La Nina to warm neutral ENSO by July.  Last summer saw a warm neutral/very weak El Nino dovetail with a w/QBO and both these neutralised the a-typical (to El Nino) low angular momentum trend and effects of the very dynamic final warming of the stratosphere in late Spring 2019 which had developed a high latitude blocking response this time last year - but was largely overcome by late June.

Last summer angular momentum trend here as identified on the 365 day plot:

 

The takeaway from all this is that falling momentum during early summer on its own per se, does not automatically imply "summer is over" each and every time. However, it does require some a-typical tropical>extra tropical proxies to be present, to alter the traditional summer La Nina low angular momentum response which blighted summers such as 2007, 2011 and also the second half of summer 2017. Just as a few examples.

 

Edited June 11, 2020 by Tamara

[Methuselah]

7 minutes ago, Azazel said:

Lol I see any ‘warmer’ temps are being constantly pushed back now. Weeks on weeks of punishment weather to come. What a vile little climate we have. 

Well, unless today's models come up with an altogether 'new' solution (possible, given the current problematic synopsis) the warm-up process is already underway; and, by Saturday, parts of the country will be seeing temps widely in the low to mid twenties?

At least that's what the models have been indicating, since at least last weekend...And barely more than a single run has suggested anything other than a spell of warmish, thundery weather...

I wish that, for once, the usual suspects would desist from their constant griping. Or, at least, post it into the appropriate thread...?

[MATTWOLVES 3]

43 minutes ago, chapmanslade said:

Is there any chance this sort of post could be given a miss by all forum members? It is pointless bashing mathematical models as 'awful' or 'rubbish'. They are what they are and we have had maybe 20 posts in the last 2 or 3 days that have said a similar thing about every model - so in effect they are all rubbish so why bother looking at any of them and go back to the seaweed. 

The ECM run splits from the ensemble members / mean at day 7. What on earth is anybody expecting from a weather model at this time and resolution ? As has been posted earlier this morning verification stats have not changed significantly so there is no story - it is life as normal. 

In all honesty mate you have a good point.. I said yesterday it's completely wrong to keep singling out how bad all these models are, especially GFS.. I've made a little humour of it myself, but not to the agree some have. FRUSTRATION is the clear word here, if these models were showing what we experienced in Spring, folk would be dancing on the ceilings, because they are not.... Folks are climbing the walls! I'm very surprised by some of the attitudes considering our record breaking Spring.. The awesome 2018 summer, and even the 3 or 4 plume events last year. I really can't see all the drama at so early in the season.. Unsettled spells happen.. But they don't last forever. If certain posters are going to say they detest this climate, then they are not ever going to be happy with the output they see. It is what it is.. We get all weather types, and we always will, move us 1,000 further South to the equator then I'm sure you will get the conditions you crave. 

Still waiting for rain here.. Not a drop yesterday, even though the forecast stated a fair bit. Looking at the models this morning, nothing looks eye popping, but neither does it look terrible. It could be the final 3rd before things improve, it could be early July, but I'm sure it will arrive. Its probably best we don't wish our lives away waiting for anything.. Life's to short. 

[Methuselah]

And Saturday's chart looks characteristically dire! Why does it always rain on meeee? 

    

If ye cannae beat 'em, join 'em!

[Uncle_Barty]

30 minutes ago, Tamara said:

 

The tropical signal rooted in the Indian Ocean will continue to promote easterly (negative) inertia across the Pacific with the standing wave relocated further upstream in the tropics - and this in turn re-configures (retrogresses) the amplified rossby wave response further downstream. In both summer 2018 and 2019,  momentum actually fell during June and this is not uncommon as linked to the Indian monsoon season which typically begins around this time .

 

 

Thank you, Tamara.

The part I' ve highlighted.. is that at least a contributary factor behind what many refer to the "June return of the westerlies" that often blights part of early summer?

[Leo97t]

Despite the poor subtopics this weekend - surface conditions are actually looking really strong partuclary further east - I am looking forward to 24C and sunshine and showers on Sat/Sun

[joggs]

4 hours ago, Tamara said:

 

Can't thankyou enough for your inputs Tamara.

Very insightful and far more often than not,not far off the mark.

Edited June 11, 2020 by Polar Maritime
Reduce quote.

[MP-R]

20 minutes ago, Uncle_Barty said:

Thank you, Tamara.

The part I' ve highlighted.. is that at least a contributary factor behind what many refer to the "June return of the westerlies" that often blights part of early summer?

This return of the westerlies is not exclusive to June. It can be applied to any time of the year when a non-westerly period has lasted for several weeks and the Atlantic returns. In fact, June is not a good month to link these two as this very fall in momentum has turned the tables the other way and we are getting easterlies.

There’s about as much consistency in the ‘June monsoon’ (terrible label) and April showers.

Back to the models, and I’m seeing very mid/late August type synoptics ie warm and at least showers if not wet at times. Not quite the UK high that I associate with June and has contributed to it being my sunniest month of the year on average.

[Methuselah]

Rather complicated, at T+144; it looks like everything's ground to a halt? Has the AAM subsided so much that the Azores HP has migrated so-far away to the west, that warm, continental air, to our east, is acting like a some sort of quasi-block? But, whatever's really happening (@Tamara, help!) it's quite definitely not the case, that all the NWPMs have suddenly turned to sheet!

    

PS: I bet that, by the time I post this, things'll have moved on. Such is life!

 

[B87]

7 minutes ago, MP-R said:

There’s about as much consistency in the ‘June monsoon’ (terrible label) and April showers.

Back to the models, and I’m seeing very mid/late August type synoptics ie warm and at least showers if not wet at times. Not quite the UK high that I associate with June and has contributed to it being my sunniest month of the year on average.

'April showers' is a phrase that always confuses me. March is typically a more showery month, April tends to be dry and stable most of the time.

July is my sunniest month by hours, August by percentage (though August has been duller than April on average since 2006).

Next week plus looks pleasantly warm here, temps of 21-26c, no heat but not cold and wet either.

Edited June 11, 2020 by B87

[mb018538]

Not much to say about the 6z other than it’s an unsettled rain fest.

ECM ensembles still show the potential for some better days around next weekend with a weak ridge just about keeping things quiet for a time.

[Methuselah]

Not a bad GFS 06Z IMO: rain, sun and temps at or slightly above normal. And, even a chance of a long-fetch SW'erly (hardly the rarest of UK weather-patterns) developing, later on. What's not to like?

    

Make grass green again!

[Downburst]

Looks like a window for the upper low to fill next weekend. 6z shows this, I know this is not the most reliable source or particular run, but if you look at next Thursday, the Low is out west creating a trough suppressing Azure Ridging, but the end of the weekend a brief retreat and opportunity for Ridging, before the next wave. We shall see. that Scandi High is taking up all the High Pressure Budget for this part of the Hemisphere, the whole north Hemisphere can't be High Pressure, all balances out. Need to move on please.