Model output discussion 14/04/18

[Frosty.]

10 minutes ago, I remember Atlantic 252 said:

change from easterly breezes at least

Yeah we're really making progress, the Ecm 12z day 10 shows a NEly!

Sorry can't post the chart..probably just as well really

[I remember Atlantic 252]

8 minutes ago, Frosty. said:

Yeah we're really making progress, the Ecm 12z day 10 shows a NEly!

Sorry can't post the chart..probably just as well really

ay, but noticed EC very rarely happens after 192 or so, pure FI

[mb018538]

That end of ecm run is so bad, and so different from anything else you just think it can’t possibly be right!

[Mike Poole]

The ECM ensemble mean does not support the op run, here at T240:

I think we need a little patience as we ride out this upcoming unsettled spell, the ridge from the Azores will come I think, setting up a great UK summer.  Meanwhile, I'm carrying on watching the models .

 

[Man With Beard]

56 minutes ago, Frosty. said:

Yeah we're really making progress, the Ecm 12z day 10 shows a NEly!

Sorry can't post the chart..probably just as well really

Not much support from previous cluster sets. Wouldn't take the ECM 12Z latter stages too seriously at the moment. 

[Stozzy]

Decent week coming up for the east coast . Temps in upper teens . Glad the most of uk has had decent weather but here it's been crap 

[mb018538]

Not a great deal to shout about this morning. It appears the second low coming across the pond later in the week will be more of a player than previously thought, and is preventing the high ridging in for now. We will just have to sit on our hands a while until things quieten down again.

[Neilsouth]

10 hours ago, Stozzy said:

Decent week coming up for the east coast . Temps in upper teens . Glad the most of uk has had decent weather but here it's been crap 

Agreed crap here too, all the way back through the supposed " Warmest May on Record "

[Djdazzle]

Poor runs this morning. Worrying that ECM has turned out two very poor runs in a row now. Ok it’s not quite as bad as last night, it’s still a rotten run for summer fans.

Edited June 10, 2018 by Djdazzle

[MP-R]

Rainfall still looking quite low for the south and east though given similar pressure readings to what we have now. Much more of an unsettled spell to come across the north. Could be quite muggy in the south with a lot of warm air getting caught in the flow a week today.

[Matthew.]

I’m sure someone a couple weeks back posted that trades would surge and with a lag effect around middle of June but then looked like easing off so expect the expected really. Maybe things should improve last week of June by what I saw back then

[Scorcher]

19 minutes ago, Djdazzle said:

Poor runs this morning. Worrying that ECM has turned out two very poor runs in a row now. Ok it’s not quite as bad as last night, it’s still a rotten run for summer fans.

Slight exaggeration, yes not great compared to the last few weeks but a lot of very decent conditions on offer for many until after midweek at least..

It doesn't look to me like the low is going to be ploughing straight through the UK, with areas further south possibly remaining quite dry. We have certainly seen worse situations in the UK in summers gone by.

[northwestsnow]

EC mean again looks a bit better than the op by day 9/10.

So all to play for longer term, would like to see a more optimistic operational over the next few days..

[Polar Maritime]

Jet certainly ramping up from Thursday into wk2 off the Atlantic from the GFS, The North bearing the brunt of the worst as usual. So an unsettled period of mobile weather coming up from the West after what has been a very calm warm and settled start to Summer for the majority.

[Frosty.]

12 minutes ago, northwestsnow said:

EC mean again looks a bit better than the op by day 9/10.

 

Indeed it does, better ridging towards the southwest, low further north.

[johnholmes]

Whatever the various 2x or 4x synoptic outputs may be showing in the past 24 hours or so, none of the 3 500 mb anomaly charts show anything other than a fairly mobile westerly, quite strong, with the upper trough pretty much over the UK. So less warm for those areas that have had such values over the past week or two, fairly changeable for the next 2 weeks or so. Better for the east coast resorts for sure. Overall better the further SE one lives as is usually the case with this type of flow.

 

[Tamara]

I'm not going to try to put too many links in this post based on the current technical difficulties, but hopefully the above image, and those below, present themselves using the image link uploader.

Its a wind anomaly profile across the tropics clearly showing up the present picture. Two distinct bands of westerly wind bursts evidenced by the deeper orange colours (with the swathe of easterly trade winds in the middle)

One: a presently unfolding convectively coupled kelvin wave east of the dateline (see Hurricane Alletta!) and mentioned in a post a few days back helping to ease the easterly trade winds

and two:

MJO related activity to the west of the dateline that has had the trade winds ahead of it. 

Both, are assisting the upwelling of warmer sub waters in the Pacific and of late have been underpinning angular momentum and sustaining the ridging pattern. This type of activity is an encouraging trend further away from the remaining vestiges of La Nina which still nag away in the atmospheric circulation despite the changing ocean signals. It *should* in theory bode better for prospects than the downward slope that summer 2017 took (when the La Nina amplified Pacific signal took hold - and influence in our own back yard of the Azores High was increasingly lost).

In the present term its the case, which should always apply anyway with any given synoptic, of not taking each and every NWP operational output at face value and waiting on the trough to suddenly lift out before the more unsettled (expected) phase has begun

Instead, letting this latest upcoming passage play out in terms of the MJO finishing its cycle and returning to the I/O which implies an imminent fall back in atmospheric angular momentum and is fully reflective of the much advertised upper westerly phase. 

What matters most for prospects further on, is seeing where angular momentum sits in terms of floor limit at this "low-end" phase of the tropical/extra tropical cycle.

This will bear witness over the coming couple of weeks (remember at this time of typing the most obviously unsettled westerly phase for the greater part of the country is still towards the end of next week) and on that basis a fully fledged downstream ridge for the UK is unlikely, in my opinion, to return within the coming two weeks - though it could well be that southern parts of the UK see a little influence from the Azores High ridge to the south-west from time to time in the warmer air advection sequences of the mobile pattern.

Whilst probably wettest further north and west, low cloud and drizzle (this time on south westerly winds) could still be an issue further south especially for windward coasts and hills. At least the east coast look to be beneficiaries this time, with the north sea effect reversed, and stand the best chance of some warm sunshine.

The important thing for summer prospects beyond this period is that the AAM floor limit continues to be higher than that of April, and then higher still than that of May. According to Spring seasonal wavelength patterns, this type of lower angular momentum atmospheric phasing is much more forgiving than summer seasonal wavelengths would be.

The Global Wind Oscillation spider graph tells the story to date with steadily recovering orbits over the Spring reflecting GLAAM ending the season back close to average. There is a technical issue also with WDT plots not updating since June 4, but that is recent enough for these purposes:

Self evidently the second half of the Spring, post the effects of the February SSW, took on a benign profile with tropical forcing and extra tropical co-operation conducive to supporting mid latitude ridging programmes that were especially kind to the North West of the UK - much deservedly for that part of the world

However (assuming for one moment and not predicting!) the atmosphere were to now get "stuck" and unable to progress further and break away properly from the vestiges and lag of 2 years of La Nina influence - this would imply ever increasing emphasis on the ridge/trough arrangement backing west (with the Jetstream suppressed from its better summer position) the more we progress through June, but more especially arrive at July.

*If* there is anything that nags away wanting very much to be proved wrong, it is this which remains the test to be overcome and represents the lingering remaining suspicion of what "could go wrong".

In this scenario, much like last nights ECM 12z operational (NB: purely for illustration purposes and clearly not to be taken at face value) this means the ridge retracted in the Atlantic, and the trough over UK, much of the rest of Western Europe and Scandinavia. The type of pattern that blights the poorest summers.

Evidence, on balance, as per this and previous posts suggests this year that there is greater antidote to a La Nina-like slump linking up with the fragile arctic ice state to spoil yet another summer overall. Obviously though the actions speak louder than any suggested words, however attempted to be best reasoned of course.

Active tropical forcing and greater cyclonic activity over the Pacific; plus the on-going kelvin wave also helping to upwell warmer waters and spread them across the ENSO zones; and the Indian Ocean Dipole (IOD) and Southern Oscillation Index (SOI) within neutral boundaries rather than reflecting La Nina forcing should all help to continue to contain easterly trade winds. In this way, limit the falls in angular momentum. Indeed, the glass half full approach has evidence enough to hold a supposition of an increasingly higher relative state of atmospheric momentum the longer summer progresses.

In synoptic terms, this latter scenario translates to increasing emphasis on rossby wave development rather differently focussed to, for example, the 2017 trend. Consolidating instead a steady evolution towards a main upper trough displaced to our west and a downstream ridge close to us and rest of NW Europe, the jet stream kept further to our north, and regular supplies of warm air advection and just transitory surface troughs bringing thundery rinse and repeat intermissions and some extra summer flavour.

But lets see off the flies in the ointment first

Edited June 10, 2018 by Tamara

[Gordon Webb]

2 hours ago, Tamara said:

But lets see off the flies in the ointment first

I'll wait and see

The flies I have in my house seem determined to survive well beyond what I want them too

lets hope the flies in the ointment Tamara was referring too are a little less resillent

Edited June 10, 2018 by Polar Maritime

[Frosty.]

My thoughts on the Gfs 6z operational are that it's less bad, there's actually plenty of high pressure / ridging at times further south with most of the unsettled weather targeting  NW britain and there is some very warm weather at times further s / se..cooler further northwest.

Edited June 10, 2018 by Frosty.

[MP-R]

Fascinating as always Tamara! I think I made sense of most of it haha. Is the suggestion that a lingering La Niña could scupper decent summer conditions as much as a developing one, or would declining La Niña to neutral exhibit improving conditions as the summer wares on?

[Fourty Point Three Degrees]

Im not prepared to write off summer just yet over a few poor ECM runs.     

[johnholmes]

43 minutes ago, MP-R said:

Fascinating as always Tamara! I think I made sense of most of it haha. Is the suggestion that a lingering La Niña could scupper decent summer conditions as much as a developing one, or would declining La Niña to neutral exhibit improving conditions as the summer wares on?

The majority of models in the IRI/CPC plume predict ENSO-neutral to continue at least through the Northern Hemisphere summer 2018 (Fig. 6). As the fall and winter approaches, many models indicate an increasing chance for El Niño.

This from NOAA CPC

[049balt]

Thanks Tamara. Keep us updated.

[Singularity]

 

A confusing state of affairs; has the current MJO cycle already terminated, or is it still ongoing?

The former supports the more changeable theme of recent GFS and ECM runs before potential recovery to generally finer weather by the final week of the month.

The latter, which appears to be driven by residual atmospheric anomalies, raises questions over how much Nina-like forcing actually manifests, offering the possibility of Nino-like interference which would help to keep some ridges in play across southern parts now and then - so still changeable, but with longer breathers in between the low pressure systems.

 

Or at least, that's how it comes across to me; I don't have quite the reliability of interpretation of these charts that Tamara has.

Beyond that range, the situation remains as she describes; in the balance, with encouraging observations but not yet enough consistent longer-term modelling to be confident that this will translate to a good outcome as we head toward July. See - it's not just winter that can place us on the edges of our seats! 

[Frosty.]

Looking at the GEFS 12z mean, it doesn't look to me as though the south would be affected much by this upcoming atlantic weather later in the week ahead, most of the unsettled weather looks to be across n / nw uk, particularly n.ireland and w / n scotland and then following this more changeable / unsettled blip the azores high ridges NE into the uk from early in week 2 bringing increasingly fine and warmer weather, at least across most of england and wales..so, this run shows more of a north / south split with southern uk seeing plenty of decent (warm / very warm) weather, especially through late june.