Model Output Discussions 12z 01/06/2017

[Captain Shortwave]

Perhaps we need to be looking in the nearer timeframes for some interest as midweek is starting to look very interesting.

The GFS has quietly come into agreement with the ECM for a brief warm up midweek with the 16C isotherm pushing into the south with the chance of thundery downpours pushing across the southern half of the UK during Wednesday night and Thursday. Mid twenties possible on Wednesday, possibly higher if the high can get a little further north as there is some serious heat building to our south at the start of the week.

[Singularity]

The retraction west of the ridge is really bugging me - it's not part of the script for the month when going by historical precedent. It ties in with the big drop in GLAAM being advertised by  GEFS and it seems this must be present to some extent in the ECM guidance now as well. 

Looking at global convective coverage, I can see what looks to be a tropical cyclone near to the Bay of Bengal - perhaps this is a factor in the models depicting a La Nina-like pattern shift. Question is then how legitimate the level of response is. I expect GFS/GEFS to be over-the-top as usual so those runs showing a mean Scandi trough edging west toward us to produce a lot of trashy weather aren't causing me concern at this stage... but it could well be that we see a 'gentle northerly' type regime as per the ECM 00z days 9-10 which would result in mean temps quite a bit lower than the majority of long-range guidance was suggesting back at the end of May (mostly due to cool nights).

I'm not sure though; we've been here before with the models depicting an undesirable pattern shift only for a Euro ridge to find its way into the equation after all, so at the moment I am inclined not to take the output all that seriously beyond a few day's range. After all there's that shallow low from Europe to be resolved, which as usual GFS is keen to lift out swiftly NE while the other models would rather let it stew over the continent with little direct impact on us.

Why can't it just be a simple outcome for a change? 

[bluearmy]

15 minutes ago, Singularity said:

The retraction west of the ridge is really bugging me - it's not part of the script for the month when going by historical precedent. It ties in with the big drop in GLAAM being advertised by  GEFS and it seems this must be present to some extent in the ECM guidance now as well. 

Looking at global convective coverage, I can see what looks to be a tropical cyclone near to the Bay of Bengal - perhaps this is a factor in the models depicting a La Nina-like pattern shift. Question is then how legitimate the level of response is. I expect GFS/GEFS to be over-the-top as usual so those runs showing a mean Scandi trough edging west toward us to produce a lot of trashy weather aren't causing me concern at this stage... but it could well be that we see a 'gentle northerly' type regime as per the ECM 00z days 9-10 which would result in mean temps quite a bit lower than the majority of long-range guidance was suggesting back at the end of May (mostly due to cool nights).

I'm not sure though; we've been here before with the models depicting an undesirable pattern shift only for a Euro ridge to find its way into the equation after all, so at the moment I am inclined not to take the output all that seriously beyond a few day's range. After all there's that shallow low from Europe to be resolved, which as usual GFS is keen to lift out swiftly NE while the other models would rather let it stew over the continent with little direct impact on us.

Why can't it just be a simple outcome for a change? 

Extended ecm ens continue to advertise s scuero upper ridge rather than trough. Also trend towards Atlantic upper trough edging close to nw Europe. I don't see a retrogression of the heights/scandi upper trough although the surface features could ebb and flow around pulsing Azores/euro ridge and Atlantic systems running sw/ne or w/e as they are currently or seems likely thurs/fri.  Generally fine outlook though always south biased 

[I remember Atlantic 252]

mini heat spike for Wednesday, reminds me of last 2 summers, with heat spike midweek, will have to pay for it though, Thursday looking a washout

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=6&code=0&mode=0

[Frosty.]

41 minutes ago, Singularity said:

Why can't it just be a simple outcome for a change? 

Could it be because we live on a little island called the uk next to the Atlantic ocean..just a thought 

Edited June 10, 2017 by Frosty.

[Singularity]

50 minutes ago, bluearmy said:

Extended ecm ens continue to advertise s scuero upper ridge rather than trough. Also trend towards Atlantic upper trough edging close to nw Europe. I don't see a retrogression of the heights/scandi upper trough although the surface features could ebb and flow around pulsing Azores/euro ridge and Atlantic systems running sw/ne or w/e as they are currently or seems likely thurs/fri.  Generally fine outlook though always south biased 

Thanks for that encouraging information BA, one day I will pay for access to the extended EC ens again - probably ready for it to dangle many carrots next winter 

Edited June 10, 2017 by Singularity

[Frosty.]

Well it's a lovely day in the south and south-east today with plenty of sunshine and temperatures around 23-24c 74f. Looking at the Ecm 00z ensemble mean shows a generally summery outlook with Azores high influence, especially for the south with predominantly warm / very warm conditions with some dry and sunny weather but also a risk of thundery showers and high humidity at times from the near continent..looking further ahead, above average temps are still indicated with a good chance of very warm / hot spells..could be worse!

Edited June 10, 2017 by Frosty.

[bluearmy]

 

A good old illustration of where the clustering agains that mean exists Karl.  Reveals where the upper troughing is most likely to run against the ridging. 

[DTHFCJ]

12 minutes ago, bluearmy said:

 

A good old illustration of where the clustering agains that mean exists Karl.  Reveals where the upper troughing is most likely to run against the ridging. 

Any chance that sequence can go a bit faster

back to these again as they are the only ones i seem to be able to post.....

 

looks very nice indeed.........plenty of very warm runs.

[mb018538]

Not an overly exciting 12z thus far, a real effort to get any high pressure in, and it now looks as though it's going to get pulled West and leave us in a yucky northerly airflow after. Better enjoy what decent stuff does turn up, as it may be a fleeting visit.

[Frosty.]

7 minutes ago, mb018538 said:

Not an overly exciting 12z thus far, a real effort to get any high pressure in, and it now looks as though it's going to get pulled West and leave us in a yucky northerly airflow after. Better enjoy what decent stuff does turn up, as it may be a fleeting visit.

I must be looking at a different Gfs 12z to you..the week ahead shows plenty of high pressure and warmth, especially further south..the high then does pull west for a time before drifting east into the uk during low res.

[I remember Atlantic 252]

2 minutes ago, Frosty. said:

I must be looking at a different Gfs 12z to you..the week ahead shows plenty of high pressure and warmth, especially further south..the high then does pull west for a time before drifting east into the uk during low res.

Well, Monday 19th is vile! 14° max, will feel raw in the northerly winds, and no doubt wet here, as showers stream through the Cheshire Gap

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=216&mode=0

[Frosty.]

Just now, I remember Atlantic 252 said:

Well, Monday 19th is vile! 14° max, will feel raw in the northerly winds, and no doubt wet here, as showers stream through the Cheshire Gap

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=216&mode=0

It looks much better for most of next week though but some prefer to gloss over that.

[I remember Atlantic 252]

2 minutes ago, Frosty. said:

It looks much better for most of next week though but some prefer to gloss over that.

yes, mini plume still there for Wednesday, just cannot help looking ahead

[weatherguru14]

4 minutes ago, I remember Atlantic 252 said:

yes, mini plume still there for Wednesday, just cannot help looking ahead

Looking ahead you serious?? take more than  5 days ahead serious..The models struggle to get anything right after that.. As its been shown over and over again..

[Fourty Point Three Degrees]

5 minutes ago, weatherguru14 said:

Looking ahead you serious?? take more than  5 days ahead serious..The models struggle to get anything right after that.. As its been shown over and over again..

Its a vile run, Wednesday/Thursday looks the best before HP drifts out west leaving a N'ly and then the run ends with Greenland blocking sending a 992mb crap fest over us. Long way off yet.

 

 

[weatherguru14]

21 minutes ago, 40*C said:

Its a vile run, Wednesday/Thursday looks the best before HP drifts out west leaving a N'ly and then the run ends with Greenland blocking sending a 992mb crap fest over us. Long way off yet.

 

 

haha thats the  26th of  June  16 Days away.. I

[mushymanrob]

the noaa anomaly charts dont currently suggest the retrogressing high. maybe they will shift tonight, maybe not.

but we have been here before with a much vaunted anticyclonic spell being picked up, then dropped or modified by the ops, before being re-instated . so ill not worry too much about a retrogressing ridge until the anomaly charts go for it.

[Captain Shortwave]

There retrogression of the high comes about from a strong jetstreak upstream which quickly removes the Atlantic trough and cuts off and area of low heights towards the Azores, the question is is this process being too quick and hence we see the trough sustained for long and allows the ridge to push further north east and instead of seeing this.

We see this....

GFS turns cool but fairly dry, the GEM develops heatwave conditions as the powerful high drifts east and a lot of hot air trapped beneath it allowed to push northwards with temperatures by the end of the run pushing easily into the low thirties. 

GEFs favour the GFS op at the moment

      

Developing an Scandi trough, too be honest one of those cool but dry and quite cloudy set up as the stability is too high to allow much convection so sunny mornings/evenings but a lot of cloud during the middle of the day. Still a long way to go yet and we we still see some warm/very warm weather midweek with the risk of thundery showers breaking out.

Arpege for Wednesday

Not too shabby if you ask me if that came off. Also looking at the ECM coming out, it has a much better solution to the mornings run with a much broader Atlantic trough at day 6/7.

Edited June 10, 2017 by Captain Shortwave

[A Frayed Knot]

22 minutes ago, Captain Shortwave said:

There retrogression of the high comes about from a strong jetstreak upstream which quickly removes the Atlantic trough and cuts off and area of low heights towards the Azores, the question is is this process being too quick and hence we see the trough sustained for long and allows the ridge to push further north east and instead of seeing this.

We see this....

GFS turns cool but fairly dry, the GEM develops heatwave conditions as the powerful high drifts east and a lot of hot air trapped beneath it allowed to push northwards with temperatures by the end of the run pushing easily into the low thirties. 

GEFs favour the GFS op at the moment

      

Developing an Scandi trough, too be honest one of those cool but dry and quite cloudy set up as the stability is too high to allow much convection so sunny mornings/evenings but a lot of cloud during the middle of the day. Still a long way to go yet and we we still see some warm/very warm weather midweek with the risk of thundery showers breaking out.

Arpege for Wednesday

Not too shabby if you ask me if that came off. Also looking at the ECM coming out, it has a much better solution to the mornings run with a much broader Atlantic trough at day 6/7.

Look at them Temps in France getting up to 44c Blimey ' Talk about schorchio .

Edit : 46 Gulp

Edited June 10, 2017 by A Frayed Knot
rephrase

[I remember Atlantic 252]

8 minutes ago, A Frayed Knot said:

Look at them Temps in France getting up to 44c Blimey ' Talk about schorchio .

Edit : 46 Gulp

46 is the numbers on the graph

[Frosty.]

19 minutes ago, I remember Atlantic 252 said:

46 is the numbers on the graph

35-36c 96f is scorchio enough for me

[Tamara]

There have been some strange observations made today, as too often occurs in this thread whatever the time of year, and largely based on the usual knee-jerk response to longer term suggested NWP.

A favourite mantra of mine is it is the net collective signals (from the tropics and extra-tropics) that lead the models, not the models that lead the signals - the latter belief of which is how posts appear to be slanted by some on here.

Its the net balance outcome of these signals at any given time (which is in constant natural flux) that determines the push and pull of the jet stream and which in turn determines the circumglobal positions of troughs and ridges. We cannot always trust the models to read these signals correctly, and often enough they slam on the brakes into reverse when they realise something else is going on.

As posted the other day, a transitory signal from the tropics is adding a modest amount of easterly winds to a global atmospheric circulation that has a decent total amount of westerly inertia in it (relative to the restrictions of an ENSO neutral signal)

That total 'westerlyness' of the atmosphere is registered in total atmospheric angular momentum which heading through the first week of June has been running close to +1SD set well against a similar longer term trend of neutral/weakly +ve AAM.

.

Clearly from that there is more westerly inertia in the atmosphere than easterly - and it is the westerly inertia that promotes warm downstream European ridges - regardless of whether these are always able to extend their influence over the whole of the UK except in the most classic summers for any extended time.

The models (especially the GFS with its I/O tropical bias) will be, and have been shown to be already,  prone for being too progressive with any attempts to scrub westerlies from the atmospheric circulation and hence break down heights over Europe at the expense of heights to the W and NW.

In context, we are some way away from the position of another a summer such as 2011 which had emerged from a strong La Nina event and struggled (and failed) to shake off the shackles of this atmospheric imprint despite the ENSO base state moving away from La Nina during that summer.

GLAAM continued to register up to -2SD throughout summer 2011

As a result of this, the summer that year saw tropical forcing concentrated throughout in the Indian Ocean, due to the La Nina footprint. The upshot of an Indian Ocean tropical forcing signal is to decelerate the Pacific jet and amplify the pattern further upstream from the Pacific with the result that the longwave pattern will accordingly adjust retrogressively.  In this way the downstream sequence of ridges and troughs evolves into an Atlantic ridge and downstream trough in our sector of the NH. No surprise the summer of 2011 was AWOL of any warm air advection summer downstream ridges and the default was the Pacific and Atlantic ridge and Scandinavian and/or /UK trough. Plenty of illustrations from the archives of that summer, but these few are typical enough.

 

Despite this weeks UK hiccup, the late Spring and early Summer period has already displayed far more inclination to pump up warm European based mid latitude ridges than was seen in the whole of that summer. IMBY perspective distorts this true perception.

In the present, total relative atmospheric angular momentum is down, as a response to the I/O signal.  It is this which the models are reading in terms of the medium term shifts.

But relative AAM is the response to the fluid flux of tropical and extra tropical signals at any given time and not necessarily an indicator of future sustained trends.

Hence why caution needs to be taken in terms of extrapolating suggested hemisphere shifts in NWP into any long term trend. In this way, any NWP suggestion of the appearance of a retrogressed Atlantic ridge (and potential downstream trough) has to be judged in perspective as a snapshot in time against the background state of this summer rather than any semi permanent sea change. 

That also means it has to be viewed within the parameters that the atmospheric circulation will allow in terms of ebb and flow of atmospheric angular momentum.  The atmosphere can disconnect from the ocean ENSO default signal to a point as happened in 2011 in terms of the continuation of a defacto Nina signal, but boundaries always exist according to how much both westerlies and easterlies can be added to global wind-flows (the Jetstream) c/o tropical forcing into the extra tropics at any given time.

This year, despite any trend towards a definitive El Nino seeming less likely in the foreseeable future that seemed possible not too long back (and which would help boost summer prospects more towards sustained heat) those boundaries are still set some way higher than they were in the likes of 2011.

I would continue to view any deviation from the default signal of Atlantic trough and downstream European ridge as an interruption to the status quo rather than any sea change (if it happens at all). The GEFS is almost certainly exaggerating the allowable bandwidth to a low angular momentum state (c/o Indian Ocean forcing) and therefore its modelling (and any other modelling which suggests the same far flung 2011 style La Nina summer pattern) should be taken with a large truck-load of salt.

The ridge may ebb and flow east and west, and this will effect how the trough interplays with it, but as stated in the previous post the other day, any sustained switch to a displaced Atlantic ridge and a cool trough is counter intuitive on the basis of evidence available.

So no change in overall thinking of before and, for what little it is worth, on the basis of the perspective offered here, a decent enough summer pattern should prevail, in my opinion, even if it isn't the sustained Mediterranean classic many hope for - and will likely stay as a changeable mix of warm/very warm settled spells punctuated by trough/ridge re-loads which see the jet stream dip south briefly before further re-set. Such a pattern will always favour the south more than the north. Nothing IMBY in stating that - its just the way this type of pattern accords with position and latitude of geographical land-mass.

Nothwithstanding varying north/south perceptions which are understandable to some degree, there is still far too much glass half empty in here, or disproportional face value judgement and extrapolation of NWP, as per usual.

As illustrated, it could be a lot lot worse and there is set to be some days of very good summer weather to enjoy.

 

Edited June 10, 2017 by Tamara

[Singularity]

Many thanks for that Tamara. It explains in great detail what I have only had time to apply in the form of suggestions that the longer-term GFS/GEFS is likely too far west with the ridge. Meanwhile ECM and the EC ens appear to be much less prone to this sort of misjudgment - less prone, but not immune.

Given the above, I am very interested in the fact that ECM is not all that different on day 7 to GEM, and only goes away from the hot weather scenario as a result of further amplifying the pattern such that the ridge extends north rather than locking into place.

 

The day 9-10 GEM charts deserve to be posted out of admiration of what's just about possible if all manner of things fall into place;

 

It requires the right balance of LP areas making it across to the east of the UK and staying west of the UK, such that the ridge does not venture away from us. 

 

These I am posting for the sheer fun of it . I daresay GEM is on course for a maximum near 34*C somewhere in the SE on Tuesday 20th. 

Not that where ECM goes is without its merits;

 

Western areas would fare nicely out  of that, eastern areas less so - though the anomalous warmth that have been widespread in the North Sea so far this month would help to mitigate the ability of low cloud to advance inland.

With the blocking to the NE standing in stark contrast to GFS' blocking to the west, the difference in model bias could hardly be better illustrated.

 

Now as much as I'd like to, I can't go ignoring the UKMO 12z, unfortunately;

 

This is extremely progressive but it occurs as a result of there being no new trough moving in to interact with the pre-existing one in the mid-Atlantic on day 5. All other models have this feature developing so UKMO really stands out with the lack of such an outcome. Even so. it serves as a reminder that even at 5 days range major changes remain possible.

In fact it's 4 days at the moment given that GFS still has the shallow Iberian low moving much closer to our shores than the other models do. More runs needed!

[Captain Shortwave]

Clear differences appearing between the GFS and ECM suites now

      

The Euro ridge remains intact out to day 10 though how far north its influence goes is up for debate, a stark difference to the ridge retrogressing strongly to our west as per the GEFs.

So ECM going for settled and warm or more changeable but still warm whilst the GEFs go for dry in the west and cool and possibly showery in the east in the longer term.