Model Output Discussion - Into Summer 2020.

[sheikhy]

Icon 06z does NOT follow the ukmo!!goes with ecm and gfs instead!!

[northwestsnow]

Still no confidence in next week...

GEM does pull the trough down as per UKMO but clears it south and we  do see the warm coninental airmass advertised by EC and GFS ..

The issue here is its a more complicated route so ideally EC will be correct, although the suite suggests the det is a bit of an outlier.

I would never personally go against UKMO so with that in mind i will sit on the fence, GFS 6Z while not a defining  moment might offer a clue as to which model is correct.

[samadamsuk]

34 minutes ago, chapmanslade said:

Yes and two days ago we were going to be 'locked in' to a cool damp period extending to most of June ! (Not posted by you I hasten to add)

If ever there was a reason to stop jumping on individual runs at 10 days this is it !

What if we are still 'locked in' for a dire month and it is just that the current runs don't show it unanimously? Surely then this comment is doing the same thing in reverse???  This isn't the long range positivity management forum it's the model output discussion - with a lot of discussion on each single modem run.

 

Things on a knife edge with the big hitters diverging right now! More runs needed as ever : 

[sheikhy]

Going to say right now the gfs 06z is not even close to the ukmo at 96 hours!!!no trough dropping at all!!

[MATTWOLVES 3]

UKMO maybe  a slight concern but it's only out to day 6,things could improve pretty quickly beyond that... One of 2 things will happen today.. UKMO and GEM will jump on board with ECM.. or the ECM will jump ship to the UKMO.. we may have a clearer answer come the 12s..but the EURO model looks top draw I must say. 

Ignore the beach picture we certainly don't want social distancing measures flouted like that..

Edited June 5, 2020 by MATT☀️

[sheikhy]

Gfs you beaaaaautyyyyy!!!!sticks tiwo fingers up at ukmo!!!high builds in perfectly!!beware of sudden change in 12zs though!!gfs has a habit of doing this!!

[northwestsnow]

8 minutes ago, sheikhy said:

Going to say right now the gfs 06z is not even close to the ukmo at 96 hours!!!no trough dropping at all!!

GFS says no to UKMO....

A small nod in the direction of EC but seasoned model watchers will be wary until UKMO model is onboard...

[I remember Atlantic 252]

1 minute ago, sheikhy said:

Gfs you beaaaaautyyyyy!!!!sticks tiwo fingers up at ukmo!!!high builds in perfectly!!beware of sudden change in 12zs though!!gfs has a habit of doing this!!

yes until UKMO on board, happened before I think, EC and GFS been wrong over ukmo

[Djdazzle]

1 minute ago, I remember Atlantic 252 said:

yes until UKMO on board, happened before I think, EC and GFS been wrong over ukmo

I have a little more confidence in that GFS was broadly supported by its ensembles.

But I want to see the UKMO 12z before I get my hopes up. Something has to give!

[LRD]

Hello chalk

I'd like to introduce you to cheese

Although, away from the UK and Iceland there are actually a lot of similarities!

And, as said before, even with that UKMO 144 chart, it's headed SW so we'll end up warm and, possibly, thundery by 192 hours anyway

Edited June 5, 2020 by LRD

[MATTWOLVES 3]

It's turned out nice again Mother..

[Leo97t]

Charts are looking very winterish synoptically- dare I say jan 1987 with a long feed from the east - glad the air is a little warmer this time!

[MATTWOLVES 3]

It's almost a similar set up to where we started in the memorable Summer of 95...

[MikeC53]

Excellent 06z out to day 9

[mb018538]

Excellent post from Simon Lee talking about the potential pattern change next week.

[Djdazzle]

1 minute ago, mb018538 said:

Excellent post from Simon Lee talking about the potential pattern change next week.

From what I can understand, this seems like good news!

[chapmanslade]

56 minutes ago, samadamsuk said:

What if we are still 'locked in' for a dire month and it is just that the current runs don't show it unanimously? Surely then this comment is doing the same thing in reverse???  This isn't the long range positivity management forum it's the model output discussion - with a lot of discussion on each single modem run.

 

Things on a knife edge with the big hitters diverging right now! More runs needed as ever : 

Exactly my point. It is futile getting hung up on 10 day individual charts even if they all agree as more often than not they will change. By all means quote them but folks on here shouldn't use that information as a 'weather forecast' level of certainty at that range and then get mystified when they get ridiculed. 

[Scorcher]

Certain posters are conspicuous by their absence this morning...what happened to all the posts about a 'dire' outlook and this pattern being 'locked in?'

Those of us who have been part of this forum for a long time have seen it all before!

Even the very good summers have periods like this at some stage- and invariably people exaggerate about how summer is over. Some are actually summer lovers who are just very pessimistic and others are coldies who enjoy speculating about northern blocking during summer etc.

I don't know about others on here but I have a very good feeling about this summer- the persistence of high pressure has been something to behold. Something tells me we could be on the brink of something special.

[sheikhy]

3 minutes ago, Djdazzle said:

From what I can understand, this seems like good news!

Seema like brilliant news mate!!!gfs is never ending high pressure lol!

[mb018538]

 

Make of that what you will!

[Tamara]

A lot of concern about the UKMO it seems.

Perhaps it is forgotten that this southward cut-off low solution was what was advertised by the ECM and GFS earlier this week and at the time it was provoking a lot of interest rather than concern! Three days is a long time on this thread!

An edited extract below from the previous post earlier in the week at the time the sinking trough was advertised  cuts through a lot of the NWP discussion detail and agitating about whether the trough sinks ahead of the amplification ridge and then the ridge overspreads the sinking trough, or whether the ridge amplifies ahead of the Icelandic trough.

But once the immediate change (and some of the worst weather) is out of the way that is where it starts to get interesting in my opinion. This retrogressive phase up to mid month is intriguing and could well end up re-setting the Atlantic trough as the ridging mechanisms back so far west that trough disruption occurs proportionately to our west .- but as stated, it could well be that the pattern retrogresses so far it re-sets the pattern to the point where momentum starts to return from upstream and a downstream Western European ridge is re-instated later in the month. That is an extended watching brief of course and will require further diagnostic data to emerge to fully back it up

The relevant conclusion is that either solution ultimately should lead to the pattern backing west and increasing signs of re-setting the trough in the Atlantic. The (welcome) difference is that is looking to happen quite a bit faster than envisaged earlier this week. It had seemed such a sequence would occur after mid month, rather than (hopefully) shortly before it

A "Western European" ridge or "North European" Scandinavian ridge are the same ballpark results.

Increasing signs now that momentum will start to rise at the pivotal point the retrogressive phase concludes.

 

Furthermore, there remains little sign of easterly zonal wind descent within the stratosphere to the troposphere c/o any strengthening e/QBO to adopt any high latitude Atlantic/Greenland blocking response which would force an omnipresent trough across mid latitudes. Note the difference here between amplified mid latitude ridges and ridges which are forged within the arctic and extend to mid latitudes. What we are seeing advertised is a summer tropospheric pattern where there is no polar night jet vortex and where ridges of sub tropical nature can extend considerably poleward. The net associated effect is that warm air advection is carried quite some way poleward. 

As long as the polar profile remains in a stable position, at least for the foreseeable future, then the first third of the summer, at least, could see some very reasonable summer weather and whilst not completely settled, there is certainly thundery potential in that warm humid air backing west . There is now a very reasonable possibility of this coming off and many will be very happy with a tropical aspect to the atmosphere

Its worth looking at the 365 day global atmospheric angular momentum plot and see similar trends to momentum tendency as of the start of June 2019

.

Back then we saw a warm first couple of days give way to a cool and unsettled phase before Atlantic ridging phased with increasing heat across mainland Europe and provided quite a cocktail of synoptic interest later in the month. There are at least some obvious similarities this June. As long as off-equator heat content in the tropics can keep driving the development of ridges to the extra tropics, and angular momentum doesn't fall too far as exacerbated by any uptick in e/QBO influence, then every reason to back that first third of summer possibility.

 

On 03/06/2020 at 23:46, CreweCold said:

There is a relatively strong correlation between solar min summers and troughing situated over or close to the UK. It's why I was quite bullish about such a scenario back in Feb/March and why I touched on it in a post the other day. Between 2007-2010 we saw summers where slack LP often got 'stuck' over the UK for a length of time. Though it's pertinent to point out, whole summer seasons weren't written off. August 2007 was decent, for example (in an otherwise poor summer).

This is an example of where" x=y" attempts at pattern match correlation cannot be fitted to one particular given pattern.  For example, one has to look at the strength of the relationship between the tropical and polar stratosphere via the QBO phasing if any undertaking of interpretation of solar activity is to be engaged. As just one variation in terms of phase relationship, a  pronounced w/QBO regime under low solar conditions in summer will tend to adjust a longwave trough generally to the west of the UK and with high pressure to the east. Summer 2006 was a very good example of this.  A very different interpretation and result to the number of washout summers suggested in the 2007-2012 years.

This might help answer a recent (very good) question about any developing La Nina this summer and how it may impact the season: Similar to the solar activity discussion with ENSO - there is no one size fits all correlation to the base state. One has to look at the precise relationship that the atmosphere adopts to the ENSO base state, and not just the base state per se - ocean and atmosphere can adopt an a-typical relationship towards one another instead of being tightly coupled.

This bridges nicely to this brand new post

  

15 minutes ago, MATT said:

It's almost a similar set up to where we started in the memorable Summer of 95...

 

A timely post Matt on the subject of a-typical forcing aspect in mind related to any Nina signal

A summer like 1995 with a weak La Nina base state for example exhibited a tropical signal often routed through convection convergence zone in the Pacific which effectively produces a more El Nino type atmospheric response- hence the predominance of anomalous downstream summer ridges rather than a controlling La Nina-esque Atlantic ridge as seen under mid summer coupled ocean>atmosphere low angular momentum conditions.  ENSO neutral especially can produce all variants of seasons - depending precisely on what the relationship is between atmosphere and ocean. So it is not possible to attempt to make prediction from the ENSO base state taken in isolation per se without looking at how the atmosphere co-operates with it (or not as the case may be)

These examples are not exhaustive, but it serves to show that each season should be taken on its own merits and whilst it can be useful to match up given drivers present in a certain season and look at other years where such combinations were present, it is necessary to look at a whole raft of proxy data to see if and where a-typical relationships may lie - as a means to avoid x=y assumptions. It is a rationale I try to follow with up to fortnightly ahead summaries, but it is just one of a few good reasons to not attempt seasonal forecasting !

9 minutes ago, mb018538 said:

Excellent post from Simon Lee talking about the potential pattern change next week.

Yes - that is a good technical explanation of the tropical >extra tropical processes mentioned often in these posts and how propagation of these "rossby wave packets" carve out anticyclones as momentum fluxes between the tropics and extra tropics. It is these forward momentum fluxes which halt the influence of the retrogressive  Atlantic ridge and re-instate the downstream ridge.

 

 

Edited June 5, 2020 by Tamara

[Man With Beard]

This is getting slightly painful watching now. I can see the charts screaming with potential for a long warm, main settled spell with thundery interruptions, and the trend is definitely that way, but I can also see the trap door to getting stuck under a deluge of rain!!

The latest clusters do not help to ease my tension. Taking the D6, D8 and D10 charts

    

you can see that at D6, a lot of runs take some sort of inclement weather through the UK, but generally as a transient event, as by D8 most charts have the trough clear of the UK, and the Scandi ridge is directing weather towards us from a warm source. All except pesky cluster 2! This one traps the trough far too close to the UK, and poses the risk of being stuck under cloud and rain, with less chance to inject warm air. At 30% of the solutions, it cannot be ignored. Cluster 1, however, gets a negative tilt to it, and allows warm continental air to get in. 

So while signs for a mid-month warm-up (and I wouldn't rule out the word "heatwave") are increasing, we are definitely not there yet!!

@Scorcher and @Tamara, in agreement with you, there's the opportunity for a really classic summer month once the next few days are out of the way, the dice seems loaded, can we avoid the booby traps? 

Edited June 5, 2020 by Man With Beard

[MikeC53]

Thanks MWB, a 10% chance of things going wrong for the UK usually materialises so 30% is near banker for belly up !

[johnholmes]

58 minutes ago, sheikhy said:

Gfs you beaaaaautyyyyy!!!!sticks tiwo fingers up at ukmo!!!high builds in perfectly!!beware of sudden change in 12zs though!!gfs has a habit of doing this!!

I think perhaps you put too much in one run which seems to fit what you would like. I'm not digging at you just trying to get an enthusiastic weather watcher to look at all options first. There is something developing, beyond T+72-96, I am unsure exactly how it may play out. Perhaps you should have a read of a couple of posts further down that may help you see the wider picture, or even read my post about the changes in the 500 mb anomaly charts for the 8 days and beyond, perhaps from day 6?

 

try MWB and T, then dj and mb. They all, in their own ways, suggest how things may be about to change.

It is great watching the models and trying ourselves to decide which is most likely to be nearer the mark. Don't be afraid to ask questions either.

An interesting time, IF the models mentioned by the various posters turns out to be correct. Watching a fairly major change of wavelengths alter the UK weather.

 

By the way Simon Lee is a Phd student at Reading Uni Met department studying the Troppause and associated matters. So worth reading things he may post.

Edited June 5, 2020 by johnholmes

[LRD]

21 minutes ago, Man With Beard said:

This is getting slightly painful watching now. I can see the charts screaming with potential for a long warm, main settled spell with thundery interruptions, and the trend is definitely that way, but I can also see the trap door to getting stuck under a deluge of rain!!

The latest clusters do not help to ease my tension. Taking the D6, D8 and D10 charts

    

you can see that at D6, a lot of runs take some sort of inclement weather through the UK, but generally as a transient event, as by D8 most charts have the trough clear of the UK, and the Scandi ridge is directing weather towards us from a warm source. All except pesky cluster 2! This one traps the trough far too close to the UK, and poses the risk of being stuck under cloud and rain, with less chance to inject warm air. At 30% of the solutions, it cannot be ignored. Cluster 1, however, gets a negative tilt to it, and allows warm continental air to get in. 

So while signs for a mid-month warm-up (and I wouldn't rule out the word "heatwave") are increasing, we are definitely not there yet!!

@Scorcher and @Tamara, in agreement with you, there's the opportunity for a really classic summer month once the next few days are out of the way, the dice seems loaded, can we avoid the booby traps? 

Are they anomaly (anomalous from the norm) charts? If so, with relatively high pressure normal for the UK at this time of year, even cluster 2 on Day 8 might not be a disaster as it could indicate a slack low with warm air still getting in the mix? Or am I reading that wrong?