Model Output Discussions 12z 03/05/2016

[knocker]

The ecm has the front tracking NE on Friday so generally effecting the west and north. Temps slightly above average in England. The next system arrives Saturday night bringing showery rain to the north and west but quite possibly to the rest of England in the westerly wind. Temps still just above average. The unsettled theme continues with the next system arriving on Wednesday but temps still not too bad.

[Frosty.]

14 minutes ago, knocker said:

The unsettled theme continues with the next system arriving on Wednesday but temps still not too bad.

According to the GEFS 00z mean, it doesn't look unsettled at all in the south of the uk for the next 10 days with plenty of Azores ridging bringing a good deal of fine and warm weather, a few bands of showery rain spreading from the west but predominantly fine further south.

[northwestsnow]

Yes ecm looks in the main very dry for the vast majority after tomorrow acc to the 00z operational, so i'm really not sure i would even attach the word unsettled to that run at all?

Obviously the better the further south you are but in the main a very pleasant run imho.

Sorry should have added that only applies to monday morning (reliable timeframe), The longer term perhaps more influence from the trough..

Edited July 19, 2016 by northwestsnow

[Frosty.]

26 minutes ago, knocker said:

The unsettled theme continues with the next system arriving on Wednesday but temps still not too bad.

I agree with northwestsnow, the word unsettled does not apply to southern uk, a few changeable interludes sure but a lot of fine warm weather too! :- )

[Gordon Webb]

Well I for one will be glad to see the back of this heat 2 days is more than enough for me and a decline back down to pleasant low to mid twenties will suit me fine

[northwestsnow]

2 minutes ago, Gordon Webb said:

Well I for one will be glad to see the back of this heat 2 days is more than enough for me and a decline back down to pleasant low to mid twenties will suit me fine

Me too, might be a bit too hot today lol, mid twenties is fine for me

FWIW the south should look forward to a decent spell of summer weather stretching into next weekend acc to ecm 00z and acc to the BBC weather app mid 20's and sunny spells all the way through next weekend, lucky buggers

Edited July 19, 2016 by northwestsnow

[knocker]

12 minutes ago, Karl. said:

I agree with northwestsnow, the word unsettled does not apply to southern uk, a few changeable interludes sure but a lot of fine warm weather too! :- )

I will make three points here. Firstly it would better if you quoted what I wrote in full and not just a snippet like so

Quote

The next ten days according to the GFS. Generally unsettled with frontal systems arriving Friday ad Sunday and a small low next week. These will impact the west and north west rather more than the SE Temps generally around average but leaning towards a NW/SE divide but becoming below average at the end of the period.

Secondly I was attempting a general overall comment and not concentrating on the SE alone.

Thirdly running through the 6 hourly charts of the ecm run if that doesn't qualify as unsettled then I'm the Dalai Lama. Unsettled doesn't necessarily translate to grot but just a very moblle scenario.

I very much get the impression that you and one or two others are deliberately attempting to nit pick. I say attempting advisedly.

 

Edited July 19, 2016 by knocker

[northwestsnow]

5 minutes ago, knocker said:

I will make three points here. Firstly it would better if you quoted what I wrote in full and not just a snippet like so

Secondly I was attempting a general overall comment and not concentrating on the SE alone.

Thirdly running through the 6 hourly charts of the ecm run if that doesn't qualify as unsettled then I'm the Dalai Lama. Unsettled doesn't necessarily translate to grot but just a very moblle scenario.

Why but I very much get the impression that you and one or two others are deliberately attempting to nit pick. I say attempting advisedly.

 

No nit picking from me knocks, i just checked out the ecm precip charts and it looks very very dry for the vast majority out to monday morning so was curious about the 'unsettled theme continuing ' comment, nothing wrong with a bit of debate

Perhaps there is a bit of confusion about the wording unsettled to me suggests wet and windy, maybe im wrong, anyway, off out the garden for some refreshments for me , enjoy the day

Edited July 19, 2016 by northwestsnow

[Gordon Webb]

What I'm finding interesting this time round is that the breakdown of what it is is affecting more N and W areas whilst the southern half of the UK whilst not immune from any adverse weather is not the focus normally in breakdown like this storms march from South to North right through England then weakening when approaching Scotland this time Wales NW England NI and Scotland seems the focus while more southern get less relatively speaking that is

can someone explain why it's different this time , I know it's probably a simple explanation so if someone knows I'd appreciate it

Edited July 19, 2016 by Gordon Webb

[Frosty.]

I find the word unsettled to be misleading as far as southern uk is concerned for the next 10 days, the Azores ridge builds across the south from the weekend and well into next week according to the GEFS 00z mean. I'm only describing what the charts are showing, nothing more, nothing less.

[knocker]

20 minutes ago, northwestsnow said:

No nit picking from me knocks, i just checked out the ecm precip charts and it looks very very dry for the vast majority out to monday morning so was curious about the 'unsettled theme continuing ' comment, nothing wrong with a bit of debate

I'm not disagreeing that the south will remain fairly dry for this week but the north and west will be effected by a front Friday thanks to the low pressure to the north west but from Sunday onwards pretty unsettled for all with a secondary low forming and tracking NE into the North Sea. My point is it's quite mobile pattern but yes there is a N/S split until the weekend but overall best described as unsettled. Just MO of course.

 

Edited July 19, 2016 by knocker

[northwestsnow]

Just now, knocker said:

I'm not disagreeing that the south will remain fairly dry for this week but the north and west will be effected by a front Friday thanks to the low pressure to the north west but from Sunday onwards pretty unsettled for all with a secondary low forming and tracking NE into the North Sea. My point is it's quite mobile pattern but yes there is a N/S split until the weekend but overall best described as unsettled. Just MO of course.

No probs knocks, nothing wrong with debate , as ever the proof will be in the pudding, you may well be correct..:)

[knocker]

1 minute ago, northwestsnow said:

No probs knocks, nothing wrong with debate , as ever the proof will be in the pudding, you may well be correct..:)

Whoa, I'm not suggesting this will verify.

[Fourty Point Three Degrees]

Well fingers crossed the azores will build much further North than the 00z is showing, this time last week the gfs for today was only showing mid 20's for the South and look how it evolved.

[Gael_Force]

3 hours ago, northwestsnow said:

No nit picking from me knocks, i just checked out the ecm precip charts and it looks very very dry for the vast majority out to monday morning so was curious about the 'unsettled theme continuing ' comment, nothing wrong with a bit of debate

Perhaps there is a bit of confusion about the wording unsettled to me suggests wet and windy, maybe im wrong, anyway, off out the garden for some refreshments for me , enjoy the day

Hi, do you have a link to the precip charts for ECM, please?

Edited July 19, 2016 by Gael_Force
A thanks to NWS

[stodge]

Morning all

Well, yes, the overall theme hasn't changed too much. After the current heat snap passes, there's the extended Azores HP ridge which keeps the south in particular but not exclusively dry, settled and warm rather than hot with the prevailing westerly wind keeping the heat well to the south. Nice normal summer fare, nothing spectacular or extraordinary, just what you'd expect. 

The story then (from the GFS 00Z OP) is the slow erosion of that ridge from the NW during next week

Just hanging on to the end of the week in the south but already pressure dropping further north and into early August the theme of a more unsettled outlook with the jet returning south remains very much the form horse.

ECM offers something a little different breaking the ride down more quickly but keeping the Azores HP closer:

GEM on the other hand keeps the ridge stronger and longer and would be the one for fine weather fans:

As ever, more runs are needed...

[northwestsnow]

20 minutes ago, Gael_Force said:

Hi, do you have a link to the precip charts for ECM, please?

Hi G- they are on the icelandic metoffice site, you have to look for Atlantic ocean forecasts and you will see precip temp etc,

[knocker]

No significant change in the overall pattern with the ecm and GFS anomalies this morning.or last night's NOAA

 

[mb018538]

Yep knocker, that trough parked in its now spiritual home just next to the UK, with above average heights in Greenland as expected. Incidentally, the 6z has the 10-12c 850 isotherm never really leaving the SE corner (out to day 8), hanging on grimly for dear life. The NW, especially Scotland and Northern Ireland turns much cooler and unsettled. Classic summer NW/SE dividing line stuff.

Edited July 19, 2016 by mb018538

[knocker]

4 hours ago, Gordon Webb said:

What I'm finding interesting this time round is that the breakdown of what it is is affecting more N and W areas whilst the southern half of the UK whilst not immune from any adverse weather is not the focus normally in breakdown like this storms march from South to North right through England then weakening when approaching Scotland this time Wales NW England NI and Scotland seems the focus while more southern get less relatively speaking that is

can someone explain why it's different this time , I know it's probably a simple explanation so if someone knows I'd appreciate it

Put simply GW the cold front approaching from the west is introducing colder air into the mix with some quite lively results. Not forgetting that the warm air has advected north into Scotland.This doesn't effect the SE.

Edited July 19, 2016 by knocker

[Frosty.]

4 hours ago, knocker said:

I will make three points here. Firstly it would better if you quoted what I wrote in full and not just a snippet like so

Secondly I was attempting a general overall comment and not concentrating on the SE alone.

Thirdly running through the 6 hourly charts of the ecm run if that doesn't qualify as unsettled then I'm the Dalai Lama. Unsettled doesn't necessarily translate to grot but just a very moblle scenario.

I very much get the impression that you and one or two others are deliberately attempting to nit pick. I say attempting advisedly.

 

Changeable would have been a better word to describe the outlook, unsettled implies trough domination or Atlantic lows sweeping across the uk but I'm seeing some Azores ridging influencing at least the south of the uk at times through the next 10 days..so a lot of fine warm weather too.

[mb018538]

Even the 06z GFS shows afternoon maximum temperatures today of 30c....pretty laughable really when we've already passed 32c!

[Frosty.]

Looking at the GEFS 6z mean shows the Azores ridge building in across the south of the uk from this weekend and well into next week and following a short lived relatively cooler / fresher blip on thurs/fri, temps rise into the mid 20's celsius across the south once again with a lot of fine weather further south, not completely settled in the south but never worse than changeable, however, the north / northwest of the uk looks more unsettled but still with some fine and pleasantly warm spells too.

 

Edited July 19, 2016 by Karl.

[Frosty.]

Before I'm accused of cherry picking, I should point out it was my hot perturbations in the last few weeks, the ones that were derided in certain quarters that have led to the current spanish plume with 31 / 35 celsius temps.. anyway, I have found some decent GEFS 6z perturbations for next week which show the Azores high ridging across the uk. I should point out there are some troughy ones as well for the sake of balance but the way I see it,  this weekend and next week should contain at least some fine and warm weather, especially in the south but not exclusively..as most of you know, my glass is half full so let's hope for a continuation of summer weather post plume.

[Tamara]

Todays heat marks an appropriate opportunity to put an otherwise unremarkable summer so far into context.

The legacy of departed El Nino to start summer has seen last gasps of active tropical activity which have prevented, so far, total global atmospheric angular momentum (GLAAM) falling too far, for too long.  This has actually prevented the summer to the half way point being worse than it has.

A steadily establishing low angular momentum base state frameworks persistent upstream amplification of the Pacific jet and we have seen the continued establishment (started some weeks back) of a strong North Pacific ridge and downstream alignment sequence of troughs and ridges, one of which is the increased profile of the mean Atlantic/Azores ridge.  

The chart below with the double dip plunges in atmospheric angular momentum tendency (AAM) during early June and early July represent the cyclical symmetry of two book-ended surges of easterly winds added across the Northern Hemisphere at the aborted demise of the active tropical convection cycles (mentioned at the start of the post), once arriving at the Western Pacific that have been seen since the start of summer

The peak in the middle of the chart for July represents the atmospheric circulation response to the active eastward progressing tropical phasing prior to decay  - the scrubbing out of easterlies across the NH with a burst of westerlies and a re-boosting of AAM tendency.

The positive consequence of a modest recovery of AAM is the spinning up of a Rossby wave train propagating downstream and helping inflate ridging from the main Azores High towards our part of Europe and hence the series of attempted and discontinuous (!)  improvements seen in the UK weather pattern over the last few weeks that have culminated in this weeks eventual success.

The importance of the troughs though in that AAM tendency chart is the manifested attempts of the atmospheric circulation to establish a more and more defined La Nina base state at the completion of each tropical cycle.  The late June/early July peak needs to be seen in a context of the turning tide discussed in previous updates - we are not likely to see further recoveries of this scale as a La Nina base state sets more and more in stone.

Beyond the initial confidence gained from early understanding of the atmospheric circulation template for the summer (and therefore being able to call the strength of the mean Atlantic ridge as a major seasonal influence) the much harder problem has been trying to establish how far south/ north the downstream jet might behave through the season. Various posts have dealt in some detail with this difficulty of trying to anticipate the expected strength and orientation aspects of the dominance of the Atlantic ridge and how it might influence our weather this summer.

As we know this ridge has been involved in a major 'will it, won't it?' ritual dance with the long wave trough - with the UK being the sandwich between the trough to the NW and the ridge to the SW.

Despite the frustrating pattern rut, for the reasons explained above, we have in truth seen restricted westward retrogression of the mean Atlantic ridge (so far) from sustaining the most unsettled conditions and associated cooler polar maritime sequences of weather we have seen for longer than has been the case.

The benefits of feedback legacy of the active tropical cycles seen during June, and now July, have illustrated the importance of the lag effects of tropical/extra tropical intra seasonal phenomena in influencing seasonal weather patterns.

I remember stressing these lagged effects in an update some weeks backs and how they might influence the overall default summer pattern.

The result has been that the mean default ridge/trough pattern has managed to attain at least a modest amount of both eastward and pole-ward sub tropical ridging displacement (towards Europe).  The recent transitory spike in angular momentum as a result of that tropical forcing feedback has allowed enough amplification in this ridging for a surge of warm air advection from the heat plains of southern Europe

Happily this significant warm air advection has been more than expected 10 days back.

So, what next?

Based on where the atmospheric circulation is at and most likely trends, the Azores/Atlantic ridge and interplay with the trough are set to continue to dominate the UK fortunes probably for the rest of the summer.

AAM tendency as we see in the ^^ chart, is now sharply down again.

This fully advertises further feedback to strengthening the upstream amplified Pacific pattern as discussed in the first part of this post. The question remains, as ever, where the next floor in GLAAM lies.  

The problem we face now is that there is less and less forcing mechanism available of the type available so far this summer to prevent angular momentum falling further than it has. We cannot obviously rule out further hot snaps/spells, but it certainly doesn't help make them more likely. Such an outcome would make it hard to see a repeat of the type of eastward and  poleward ridging of the Azores High we have been seeing recently. A further decisive fall in AAM will add extra retrogressive pull on the Azores/Atlantic ridge with the result of a leaking away of pressure over the UK and Europe where a vacuum is left.

The continued additions of easterly winds to the atmospheric circulation, and crucially with less and less westerlies available to counter them in the absence of further amplitudinal eastward moving tropical convection as discussed in this post, imply further downward  the likelihood that the Global Wind Oscillation (GWO) will not repeat any further orbit towards Phase 4/5 during the rest of this summer such as quite recently - and spend more and more time in Phases 1,2,3.

It is therefore also precisely why, impressive as it is, the current Euro heat ridge is so very transitory. 

For heat ridges to prevail, the GWO would need to be attracted towards the Nino-like phases - and be heading from (recent) Phase 4 to Phase 5/6/7 instead of back to Phases 1,2,3 

With some feedback inertia left over from the July tropical convective cycle, it is just about possible we will see one further attempt to build pressure from the SW to follow what looks a slow evolution during the rest of July towards yet another likely cooler and unsettled spell, maybe more especially into the new month.

However, as stated, the next tropical cycle does not show signs of the type of amplitude and eastward progress seen during the earlier summer to propagate Rossby waves downstream to NW Europe and provide further heat surges as we have with us currently.

The previous MJO cycle sharp demise on arrival towards the West Pacific is clearly shown in the current model forecasts. The next cycle, as discussed, looks weak and unlikely to progress as far as that. Very much a signal of increasing Nina-esque atmospheric circulation

The summer outlook continues the changeable theme.  In the shorter/medium term there is no shortage of heat remaining across mainland Europe - and the initial retrogression of the upper High to our west may still leave a sluggish pattern for a while with residual warmth keeping the more unsettled interludes seasonal enough - but more especially the further south and east one is.  There are enough suggestions within current NWP to accommodate this.

A risk though that as the amplified Pacific feedbacks feed more and more downstream, that a more widespread and much cooler polar maritime influence may arrive with an upper trough taking up residence just to our NE along with a retrogressed amplified ridge in the central/ western Atlantic raising heights towards southern Greenland.