Model output discussion 14/04/18

[Dominic Carey]

I’m a bit confused that there’s still no solid agreement for the the beginning  part of next week but also pleased to see heat potentially returning middle of next week

Edited June 26, 2018 by Dominic Carey

[mushymanrob]

2 hours ago, johnholmes said:

Not time to post links to anomaly charts but all three I use now have some kind of troughing in the UK area rather than ridging, that is 6-10 day period from now. This has been a rather uneven transition from the ridging set up.

surely though, its only shallow troughing, and no real return to serious troughing with gales and heavy rain, id have thought the pressure is still on the +ive side of neutral , so some unsettled weather but a lot of fine mainly dry conditions?

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

[shaky]

Interesting gfs 06z!!biscay low slightly further south and west and pulls in a drier flow off the continent for sunday and into monday with south east winds!!result is more hot and sunny weather and not as unsettled on sunday either!!apart from a light band of showery rain midday sunday pushing north across england it looks like a pretty good day either side!!saturday looks pretty darn good on this run!

[Fourty Point Three Degrees]

As some were saying a few weeks ago every classic summer has its unsettled breaks. 2003 and 2006 both had their heatwaves put on hold for some unsettled blips.

Edited June 26, 2018 by 38.5*C

[mb018538]

Exactly, bit of perspective needed! Every great summer in the UK has had some unsettled blips...for all we know we could be back here towards the middle of July in a similar set up with more heat.

[Man With Beard]

The progressive ECM op run with its deeper trough by the UK was in the smallest cluster between D5 and D7, with the other clusters maintaining better heights locally:

    

though we are nearing the point where op runs should be ahead of ensemble members more consistently.

Beyond D7 still messy, and very much dependent on whether heights can build successfully to our NE - ensembles that do so are much keener on keeping the Atlantic at bay longer term.

[Methuselah]

2 hours ago, summer blizzard said:

Although it would stay warm to hot for some time it would appear that a marked downgrade has occurred overnight with both the Euro and GFS backing yesterday mornings solution of a thundery low moving north and then letting the Atlantic move through. Day 5 is when this process all begins to occur. 

 

We're obviously going to be exposed to umpteen upgrades/downgrades between now and whenever/if ever the weather/model-output materialises...?

Whenever I used to witter on about what I might have or what might happen (whenever) my mother always told me that 'tomorrow never comes.' I suppose that same logic applies equally to next week?

Edited June 26, 2018 by Ed Stone

[mushymanrob]

2 hours ago, 38.5*C said:

As some were saying a few weeks ago every classic summer has its unsettled breaks. 2003 and 2006 both had their heatwaves put on hold for some unsettled blips.

yes they did, as long ago as 75, and 76. it was never 3 months of continuous heat, in fact i believe the longest continuous run of heat (25c+ ) here was in 1995 at 11 days, although there might have been more in '76 i dont know.

[Methuselah]

6 minutes ago, mushymanrob said:

yes they did, as long ago as 75, and 76. it was never 3 months of continuous heat, in fact i believe the longest continuous run of heat (25c+ ) here was in 1995 at 11 days, although there might have been more in '76 i dont know.

16 successive days at 32C or higher in June-July 1976, I believe?

[Flash bang flash bang etc]

 

2 hours ago, 38.5*C said:

As some were saying a few weeks ago every classic summer has its unsettled breaks. 2003 and 2006 both had their heatwaves put on hold for some unsettled blips.

 

The blips are often my favourite bits

?⛈

Edited June 26, 2018 by Flash bang flash bang etc
Quoted the wrong post

[mushymanrob]

2 hours ago, Ed Stone said:

16 successive days at 32C or higher in June-July 1976, I believe?

no i mean in one locality, not nationally.

but if you mean one locality, fair enough !

 

 

Edited June 26, 2018 by mushymanrob

[Methuselah]

8 minutes ago, mushymanrob said:

no i mean in one locality, not nationally.

but if you mean one locality, fair enough !

 

 

In which case, either way, we are most definitely both posting in the wrong thread...

[Tamara]

Much has already been said of the 5 to 10 day period in terms of the phasing of the Iberian trough with an Atlantic breakdown. As others have rightly indicated, morning operational output attributed mostly to the ECM suggest this might well be the most progressive solution and tonights follow-up output will be not long coming to see if this is repeated. But, just for now, as well as the indications as discussed from the clusters, the graphical ensemble for London suggests the operational was one of the coolest solutions into next week and more especially significant probably, amongst the very wettest of all

 

But this type of progression is an aspect of the models playing on the seasonal wavelength long-wave evolution with regard to the Atlantic ridge that prevails under low angular momentum conditions and how the upstream pattern increasingly favours withdrawl of the eastward extension of this ridge to the west of the UK heading into the heart of summer under such a regime. As pressure falls downstream then its not hard to see how a trough fills the void. Pretty much every post made since mid May has tried to anticipate such an eventual evolution in these conditions and put forward the pros and cons of the alternative pathways. Ridge/ trough, or trough/ ridge?

Also as previously suggested might be the case, the time is now arriving for any notion that such an sustained? (big question mark here) evolution is to be forthcoming, is to be strongly tested - because evidence keeps stacking up to the contrary and some NWP bluff might well be called in the week or two ahead.

Some wider spectrum data with comments and conclusions :

 

 

 

Consensus firming up further on trend towards fledgling El Nino within a timeframe that is coming closer and closer, the SOI is consistently on the -ve side of neutral,

https://www.longpaddock.qld.gov.au/soi/

...and there is yet another oceanic kelvin wave in progress across the Pacific upwelling warm sub waters to assist SST warming across all ENSO zones in the coming few weeks.

Indeed the Nino 3.4 region, boxed as above at the top of the page, is now at its highest value (+0.4C) since July 19 2017 - and which is a timely statistic as it represents when trades winds were rapidly increasing as the Pacific ENSO zones were cooling, La Nina was establishing a greater grip on the atmospheric circulation and a brief plume around the 18th/19th July was a last gasp before the summer went rapidly downhill heading into August. That is, if we except a very short, but nonetheless very pleasant and welcome summer-like spell (mostly for the SE) at the August Bank holiday. Particularly welcome at the time because a chilly and increasingly wet autumn beckoned almost immediately September started.

But its especially timely now. Bearing in mind the knee jerk frailties of this thread at any time of year, its worth anticipating ahead how any apparent upcoming breakdown scenario from next week is destined likely to be reacted to in terms of pessimistic extrapolations for remaining large chunks of the summer.

Keep in mind the swathe of broad-scale signals listed above, and then see that there is currently representing a substantially increased disconnect of at least  -2SD low angular momentum (essentially still an emphatic La Nina signal at face value).

 

 

If this summer is really a carbon copy of summer 2017 then one might indeed extrapolate that the ridge extension from the Azores High is set to evaporate, as dictated by seasonal wavelength changes under -ve GLAAM - and the rest of the summer is to be swamped from upstream by persistent trade winds, an amplified Pacific and a downstream Atlantic ridge , suppressed Jetstream and UK trough

The beauty of this weeks synoptic through the grace of Atlantic ridge extension underpinned by an Iberian heat trough, might further exacerbate the sort of angst described from some quarters.

Yet, peeping above the NWP 6hr roundabout navel-gaze, and with that ocean/atmosphere unstable disconnect in mind, something has to give. All those broad-scale intra seasonal signals can't be wrong can they?

Its not the actual ocean base state that has particular importance here, but to carry on the good point that @Singularity was making yesterday, its the very correct implication that a significant rally in atmospheric angular momentum is imperative to happen as a vital piece of jigsaw to achieving the ocean/atmospheric coupling that makes the move towards a base El Nino state possible. 

Such necessity is founded on where the atmospheric circulation is currently - in terms of atmospheric angular momentum and where the pattern would indeed almost certainly head downhill through July *if AAM stays where it is now*.

Rallies in AAM tendency, especially the more significant and robust they are, imply very warm/hot spells in the heart of summer as much as they trigger cold spells in winter. The lead-up to the Feb 2018 SSW being a classic case of intense tropical poleward momentum (leading to a temporary reversion of the La Nina standing wave that month) - and the rest is history as they say.

The current suppression of AAM is linked to tropical convection being entrenched in the Western Hemisphere at present. It will be this, that will be programming increases of easterly (Nina-like) trade winds and in turn risk flipping NWP to a less desirable pattern

 

 

But it cannot stay there forever, especially bearing in mind the contrary oceanic signals happening in the Pacific. I will be keeping a very close eye on the tropical/extra tropical cycle as we head through the first half of July for events in the Pacific triggering a significant westerly wind burst and a surge in AAM that would shake-up the synoptic pattern from any attempts to descend into cool British summer wetness.  .

High pressure in the Atlantic and/or blocking at higher latitudes and a downstream trough c/o southerly tracking jet seem much more counter intuitive than the progression of last summer which took this sort of route. Rather instead, any breakdown leading to the increasing spectre as time goes by of a trough re-setting/stalling to the west of us and high pressure over and to the east.

As ever of course Mother Nature and the weather has the last word, but I can't see unsettled interludes being anything more than short-lived this summer

 

 

[Methuselah]

Just one Q please, Tamara: Do you have any idea of how long it would take the developing El Nino signal to overwhelm the inertia contained within the overall ocean-atmosphere system? Does the burgeoning Nino have sufficient momentum to force a major pattern-change, this side of Autumn, do you think? I do struggle with teleconnections!

[I remember Atlantic 252]

UKMO swelters the UK for opening day, could be very humid too

[Dominic Carey]

8 minutes ago, I remember Atlantic 252 said:

UKMO swelters the UK for opening day, could be very humid too

Wow amazing!!

[Craig84]

12z UKMO is looking much more like it. We keep more separation of the Iberian low and Atlantic trough.

This keeps pressure higher through the uk and look at the very warm 850’s being pumped north. GFS doesn’t agree tho, let’s see what the ECM has to say about it. 

[TJS1998Tom]

Seems like the chance of a thundery breakdown of some sort is increasing with the 12z

[Man With Beard]

Still quite astonishing differences for that troublesome Iberian low!!

As it's getting close, maybe it's now worth a guess - I guess the GFS is overdoing the low (which is what it tends to do), and the UKMO is under doing it (which is also what it tends to do).

Therefore, can we speculate that the truth is somewhere in the middle - thundery weather reaching the SW earlier than UKMO so Sunday or Monday (hot in the E + N), but not reaching the whole of the UK till later than GFS, so Tuesday or Wednesday?? 

[Craig84]

12z ECM siding with the UKMO at 120!

 

 

[shaky]

52 minutes ago, Man With Beard said:

Still quite astonishing differences for that troublesome Iberian low!!

As it's getting close, maybe it's now worth a guess - I guess the GFS is overdoing the low (which is what it tends to do), and the UKMO is under doing it (which is also what it tends to do).

Therefore, can we speculate that the truth is somewhere in the middle - thundery weather reaching the SW earlier than UKMO so Sunday or Monday (hot in the E + N), but not reaching the whole of the UK till later than GFS, so Tuesday or Wednesday?? 

You cant make this up lol!!ecm has gone further south again with the biscay low and for england and wales its another hot and sunny day on sunday!!ukmo maybe on the money here!!wiked stuff!!and what a chart at 144 hours!!hot for england and wales again!!biscay low west of portugal lol!madness!!

Edited June 26, 2018 by shaky

[Singularity]

Or maybe not given the 12z ECM @Man With Beard... the fascinating uncertainty grows even larger! 

I wasn’t expecting such an outcome from ECM at first, but then I had a look at the 12z ARPEGE and saw that it was heading along similar lines to UKMO and that started me wondering.

It’s now west of N Atlantic v east of N Atlantic, as GEM is similar to GFS.

 

Now here’s a thing longer-term; despite the similarity at the weekend to GFS, GEM manages a good move toward the Atlantic trough, Euro-UK ridge pattern as the following week progresses. 

Which is to say, the weekend uncertainties are independent of the ‘how long changeable for’ question for next week.

 

To be honest, even the notion of more than ‘peripheral’ influence from troughs is coming under fire with today’s trend. Probably still enough to bring some useful rain across 1-3 days, but with temperatures staying on the warm side, perhaps even very warm in any sunnier interludes.

Edited June 26, 2018 by Singularity

[Man With Beard]

Agreed @shaky @Singularity! What's also interesting is how the Atlantic hasn't properly got in even by next Wednesday, it's stalled on contact with the ridge to the east!

A possible ten day heatwave, then? 

[Dominic Carey]

Wow what a amazing chart from ECM

[northwestsnow]

Yes EC is a good run for those wanting more warmth.

Much less involvement of the trough to the south on the 12z- looks like there might be a few more twists and turns but i feel after viewing the UKMO the chances of the warm weather lasting through the weekend have increased.