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Model output discussion 14/04/18

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Just to add to the good news tonight. Given which it seems unusually quiet in here.  Here's the last four CFS runs for June, Z500 anomalies, 0z first:

cfs-3-6-2018.png?00

cfs-3-6-2018.png?18

cfs-3-6-2018.png?12

cfs-3-6-2018.png?06

Taken with the GloSea5 charts posted earlier, I think we can say 'Roll on summer!' 

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Well on the 18z ICON at the end of the (short) run,there's some  kind of Great Crested Jet Stream Demon creature by T 120, here:

icon-5-120.png?14-18

But it won't deprive us of our high pressure and start of summer:

icon-0-120.png?14-18

Edited by Mike Poole
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These charts at the moment could make a grown man cry

167E0A61-097A-487F-936F-98D9B3231270.jpeg

2042587E-0269-4212-AA9E-6FA66221B9C8.jpeg

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Fantastic ECM run this morning - increasingly settled, dry and warm as high pressure builds.

ECH1-216.GIF?15-12

The sight (nearly) everyone wants to see during the summer....low pressure all over the north pole. Stay there please!

We should exercise some caution. A few days ago the ECM was showing a massive polar high for this Saturday:

ECH1-240.GIF?12

ECH1-96.GIF?00

That isn't going to verify. Keep those eyes peeled.

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Just now, mb018538 said:

Fantastic ECM run this morning - increasingly settled, 

The GFS was excellent too. High pressure dominating from start to finish.

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The GEM keeps the high going next week but others develop a low which gets stuck across the SW/S and that could spoil our walking holiday somewhat around the coast of southwest Wales. However they all seem to agree on it staying much milder than recent weeks with the GFS showing 14-17C there throughout each day despite some rain 

Edited by Jonathan Rhodri Roberts

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On ‎08‎/‎05‎/‎2018 at 09:41, carinthian said:

Nice to see many parts enjoying the high temps across Blighty yesterday. Highest temps seem to have been along an axis , say from Dorset to Yorkshire.  Our medium term charts continue to show, yes, a cold pool development early next week over parts of mainland Europe. A moderate snowfall at elevation in some Alpine regions (we have been issued a warning ). Looks southern Britain could be in the influence of a continental cyclonic flow by 144t/168t, maybe mixed with a warmer air mass from the east. Northern Britain  getting the best of any sunshine and nice temps. Certainly, interesting Spring weather this season with some extremes, especially across Britain.

C

Just refer to this post sent a week ago. Snowfall forecast spot on. Snow settling this morning at 1800m just above the village. Temp presently 2c on balcony. Horrrible. Trip to sunny Blighty now defo back on the cards . Will start looking for flights this morning. Our forecast team seem to back a strong Scandinavian high in the medium forecast period ( along UKMO ) latest model charts , which I think will be good for most of the British Isles, especially west and north and maybe not so good for parts of continental Europe with SE England on the periphery . Try and get some photos of the snow later but just to much low cloud in the village at the moment to venture out..

C

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Really starting to look like we'll do well out of a combination of enhanced subtropical ridging (last, but remarkably strong breath of La Nina influence?) and anomalously high heights across Scandinavia that appear tied to a combination of MJO forcing, the Arctic sea ice pattern and some particularly well-established blocking that can fend off the sluggish Atlantic.

Typically, such a pattern will be tested by early June as the thermal gradient between the continent and N. Atlantic increases further, giving the jet a bit more oomph. Sometimes, though, that stronger jet just gets sent north of the ridging and can actually reinforce it further - but the question then becomes how far north the ridge is when that happens, as it takes on a flatter, west-east orientation. Recent GFS runs have been exploring outcomes that keep the ridging unusually far north, with interesting results as heat to the east wafts across. For what it's worth, I expect the 2 m temps these runs show are likely being underestimated by a number of degrees.

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48 minutes ago, Singularity said:

Really starting to look like we'll do well out of a combination of enhanced subtropical ridging (last, but remarkably strong breath of La Nina influence?) and anomalously high heights across Scandinavia that appear tied to a combination of MJO forcing, the Arctic sea ice pattern and some particularly well-established blocking that can fend off the sluggish Atlantic.

Typically, such a pattern will be tested by early June as the thermal gradient between the continent and N. Atlantic increases further, giving the jet a bit more oomph. Sometimes, though, that stronger jet just gets sent north of the ridging and can actually reinforce it further - but the question then becomes how far north the ridge is when that happens, as it takes on a flatter, west-east orientation. Recent GFS runs have been exploring outcomes that keep the ridging unusually far north, with interesting results as heat to the east wafts across. For what it's worth, I expect the 2 m temps these runs show are likely being underestimated by a number of degrees.

Absolutely dream charts as a summer lover.  Would you say this current Azores/Scandinavian high link up pattern is reminiscent of (dare I say it) '76?

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As others are pointing out, that Azores High / Scandi High linking has once again taken hold in the models, and the EC clusters at D10 are no different: those oranges/reds to the NE and SW  indicating the positive anomalies:

ec-ens_nat_z500scenarios_2018051500_240.

The control cluster looks pretty awesome for spring half-term (D15), and the other two aren't shabby either:

ec-ens_nat_z500scenarios_2018051500_360.

The question will remain then - will there be enough energy in the Atlantic to drive between them? Most of the last four weeks has been a cateoric "no" but the potential remains. So I wouldn't say a hot end of May is set in stone just yet. But the balance is in that favour right at the moment.

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Met longer range and charts going for the usual fare well into June.Generally very good summery weather down here in south with the odd thunderstorm.

Unsettled midlands northwards with the usual rainy spells and average temperatures.

Could it be yet another bust summer midlands northwards? Very possible imo.

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39 minutes ago, Wimbledon88 said:

Met longer range and charts going for the usual fare well into June.Generally very good summery weather down here in south with the odd thunderstorm.

Unsettled midlands northwards with the usual rainy spells and average temperatures.

Could it be yet another bust summer midlands northwards? Very possible imo.

and London as had great summers in the last few years? :)

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Just popped in to say how much I 💘 the Ecm 00z, especially towards the end!🌞🙂

168_mslp500.png

192_mslp500.png

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216_mslp500.png

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240_mslp500.png

240_thickuk.png

240_thick.png

240_mslp850uk.png

240_mslp500_arc.png

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With charts like these I wont be surprised if May comes off as one for the books regarding sunshine hours. Still looking very dry and pleasant, ECM 00z could certainly deliver the first 30C of the year over the BHW if it comes off :D 

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1 hour ago, Tamara said:

Hi - yes, some very relevant points made :)

A favourite period of the year for me with the long hours of daylight. Autumnal weather set in comparatively early in September last year (no summer extension on this occasion) so the recurrent warm spells arriving following a cold and wet first half of the Spring have been especially welcome in my opinion with natural hopes of plenty more to come in the many weeks ahead of us.

These warm spells are a good point to begin the starting analysis. Why have they happened, and why is it important that the factors behind them sustain to allow seasonal wavelengths to augment them, rather than increasingly detract from them as happened last summer for example?

The tropics have been active in respect of MJO convection for several months. Everyone knows of the spectacular tropical cycle which helped engineer the SSW in February - but what has happened since.

This is a layered profile of the atmosphere from top to bottom for the opening months of 2018 - which tells the story well. The classic down-welling series of the negative zonal anomalies evident from the stratosphere to the tropopause layers as triggered by the massive SSW - a series of higher latitude easterlies which persisted into the first half of April. Rather accounting for the weather type seen through the first half of the Spring with a supressed Jetstream and persistent -AO/-NAO pattern

time_pres_HGT_ANOM_ALL_NH_2018.png

A change quite suddenly appeared in the middle of April with the polar field switching +ve in tandem with the Atlantic profile to +NAO.

If we take a look at the trends of total and relative atmospheric angular momentum we can see a pattern reflective of the changes across the polar field and the tropospheric pattern.   Seasonal wavelength changes heading into Spring in tandem with falling atmospheric angular momentum following the SSW locked in the longwave pattern to -AO/-NAO

gltotaam.sig.90day.gif.gltend.sig.90day.gif

 

However, during this time with the tropics remaining active, a series of +AAM anomalies propagated poleward over time in accordance with this activity and c/o co-operation in the extra-tropics in the form of repeated +ve mountain torques over Asia creating a jet extension across the Pacific and adding westerly winds to the global atmospheric circulation. (Notice also the corresponding peak in +AAM tendency in the plot above in the second half of April along with the recovery in GLAAM reflecting those additions of westerly winds).

gltaum.90day.gif

These westerlies aided a recovery in atmospheric angular momentum tendency and the poleward +AAM wave train eddies manifested anti-cyclonic wave breaking with anomalous mid latitude ridges bubbling up downstream which have assisted the jet stream north and warm air advection patterns replacing the dominant cold air advection and troughing of the supressed jet stream -veAAM/SSW legacy.

Another way of looking at the attempted ocean/atmosphere steer away from La Nina type forcing is the -ve trending of the Southern Oscillation Index (SOI) downwards from persistent +ve numbers in March (signifying a Nina-ish tendency) to much more neutral figures in the last few weeks

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

So, we have continued to reap the benefits of the lagged effects of these westerly additions through the much better surface conditions (overall) in this second half of Spring - the periodicity (timeline recurrence) of the MJO has shown its influence in this respect of large contribution towards determining longer range weather patterns, and the possibility of using these intra seasonal phenomena for assisting longer range prediction.

This overview of the seasonal evolution since the end of the winter, provides us with clues as to trends to look for ahead as another summer rapidly approaches. We also have the La Nina legacy hanging over us in terms of how things evolved from this time last year, which after all also provided some early season warmth and sunshine before, ultimately going downhill by mid summer as easterly trade winds surged repeatedly and retrogressed the fine warm anticyclonic early pattern into an Atlantic height and downstream UK trough anomaly.

The standing wave pattern of La Nina which has dominated everything for the last 2 yrs, (despite a few notable "destructively acting" disconnects of relatively higher AAM such as in February this yr leading up to the SSW) really needs to be unshackled over the coming 4 to 6 weeks to ensure that a reasonable chance that the jet stream shift seen since mid April and the presently highly enjoyable fine weather continues.

As of the here and now, we see westerlies being scrubbed from the atmospheric circulation as easterly trade winds increase in response to kelvin wave activity in the I/O

These easterlies propagating across the Pacific and with both total and relative tendency of atmospheric angular momentum snapping backwards. The Global Wind Oscillation, which is a plot depiction of total wind-flows in the tropics and extra tropics, has largely been orbiting between Phases 0/4 ( signal for downstream mid latitude ridging) since mid April and is falling back into La Nina territory Phases 1/2 in reflection of the tropical signal rooted in the Western Hemisphere

gwo_40d.gif

At the moment, being still in Spring, the significance of easterlies being added upstream amplifying the Pacific pattern and decelerating the jet downstream remains a benign enough one ( @Singularity analysis is very good here). :)

However, (assuming for just one moment the atmospheric circulation remains close to where we are at present in light of latest drop backwards) seasonal wavelength changes heading into the summer which is fast approaching increasingly suggest a retrogressive pull of the long wave pattern with the spectre of that Atlantic ridge and downstream trough returning if the ocean/atmosphere relationship cannot fully break down the legacy of the La Nina standing wave.

This (in this scenario) would mean that despite the ENSO regime "technically" returning more neutral in association with many forecasted expectations - there would still be a -ve adjustment/disconnect to the atmosphere which inclines the AAM budget within the atmosphere being pre-disposed towards greater easterly wind-flow inertia and hence high pressure in both the Pacific and Atlantic - rather than a longwave more Nino-ish pattern of, the reverse profile, of Pacific and Atlantic troughs and respective downstream ridges.

The trough in our locale under summer type +AAM/El Nino type forcing being repeatedly focussed/re-set to our west in the Atlantic and the ridges over Western Europe and Scandinavia.

There is of course every possibility that this latter hoped for scenario prevails to underpin some of the promising seasonal modelling indications. 

If we take a look at the above copied GWO spider graph of the on-going low AAM phase of the tropical/extra tropical cycle , the Phase 1,2 orbit of the GWO is thus discernibly shallower than that of 6 weeks back. This reflects the overall grip that La Nina has relaxed on the atmosphere - though clearly not yet gone completely.

Its important that we see a willingness of persisting MJO tropical activity supporting further bounces in +ve AAM anomaly wave trains, but more important still an eastward shift of the locale of this tropical activity from the Western Hemisphere

gefsbc_aam_fcst_current.png

 

Such an eastward shift in the location of tropical activity seeking cooperation from the extra tropics in form of more +ve torque mechanisms adding further westerly winds to the atmosphere to prevent the sort of deja vu of a La Nina type summer and instead keep building downstream ridges and reinforcing the trough in the Atlantic (and not the UK and Europe).  This type of persisting +AAM anomaly trade between tropics and extra tropics would see the GWO orbit more sustainably keeping away from the La Nina Phases 1,2 and 3.

The present atmospheric profile, as shown at the start of this post, is conducive to a +AO profile, which even with a de-coupled -NAO would clearly be very good for warm/plume advection - though its still early in this respect and there is time for things to change if a persisting lower angular momentum regime in tandem with eQBO gained ascendency and increases heights across the pole and encourages blocking in the North Atlantic and supressed temperatures as the tropospheric pattern retrogresses.

30mb zonally averaged winds at the equator. -ve QBO phase in italics and April figure in bold.

2017   14.92   14.78   14.35   13.88    8.01   -3.18  -10.48  -14.42  -15.28  -16.79  -17.20  -18.12
2018  -19.02  -19.37  -19.77 
-21.41

http://www.esrl.noaa.gov/psd/data/correlation/qbo.data

Aside from any La Nina disconnect considerations as part of any downside analysis, should we evolve on the upside towards a more El Nino type circulation or even a weak Modoki El Nino state during the later summer and then further on into the autumn (i.e the eastern most Pacific zone remains relatively cool and convergence winds in both the eastern and western Equatorial Pacific focus a tropical convection signal as well as help upwell warming sub waters in the Central Pacific) then there are examples such as 1990, 1994 and 2004 to draw on.

These years have all displayed the virtuous cycle nature of repeated downstream ridging at least at some stage in the heart of those summers in our locale - and bringing very warm/hot conditions (and with the exception of 1990) a fair amount of thundery activity (c/o temporary trough intrusion overspreading and destabilising the heat) for the weather enthusiast who likes some added interest to blue skies and hot sunshine as well

Lets hope that this early season promise leads on to more, and not less, for a change :)

 

 

...You make me proud to live in Hastings. exceptional post as always!

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12z UKMO keeps the high with us into next week it doesn't look like it will be going anytime soon

UKMOPEU12_72_1.thumb.png.66b61fcb4560e4f39310714171aa3aca.pngUKMOPEU12_96_1.thumb.png.5ee2db7b71b4291ce69efecf56d7cbe1.pngUKMOPEU12_120_1.thumb.png.df12d816f8ae1ec360792439eca6e303.pngUKMOPEU12_144_1.thumb.png.32f40c971febd7696b5830d6768ab8d2.png

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Fantastic early summer chart for you guys. That's what I call a super block from the Azores to the far corner of NE Europe and Blighty is right in the middle for once. 28c in Stockholm today with a surface flow off the Baltic, that's impressive  for Mid -May up there. 

C

UKMOPEU12_144_1.png.2cf7e71486baaad0fb6a3752536aa8dc.png

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Fantastic as always Tamara! Very informative and as much scope for a good summer as not it would seem. 

A friendly reminder to everyone, please don't feel the need to quote her entire post. It's a real pain when reading from a phone!

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Here's the first half of the GFS 12z, high pressure never wandering far from the UK and continuing the generally fine and warm weather:

tempresult_bdg8.gif

Later more of the same, here T300:

gfs-0-300.png?12

Sets us up nice for summer.

And thanks for that fantastic post @Tamara

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Things do seem a bit different this year after the SSW....I can’t pretend to know one percent of what @Tamara does, but love reading the posts. I can just about make out that we have a better shot at a decent summer this year with everything stirred up since the SSW. Let’s play eh waiting game....but things look ok for now.

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4 hours ago, Frosty. said:

Just popped in to say how much I 💘 the Ecm 00z, especially towards the end!🌞🙂

168_mslp500.png

192_mslp500.png

192_thickuk.png

216_mslp500.png

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240_mslp500.png

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240_mslp500_arc.png

I loved the Ecm 00z and I'm also loving 💘 the GEFS 12z mean too which is going the same way as the 6z with a scandi / azores high link up and a prolonged spell of very summery weather nationwide!🙂🌞🌞🌞

Edited by Frosty.
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GEFs

gens-21-1-144.png   gens-21-1-192.png   gens-21-1-240.png

Not the most unusual pattern for late Spring where winds from the east could dominate over a large part of the country with high pressure solidly in place to our north east, this puts western areas in the firing line for the best weather when the high pressure asserts full control whilst the east is always at risk of cooler and cloudier conditions. To be honest the extended ranage looks like more of the same, perhaps the high retrogressing towards the UK during week 2.

At the moment I don't see any major heat, but it does look warm in the sunnier spots with mid/perhaps high twenties possible in the west at times.

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2 hours ago, LightningLover said:

...You make me proud to live in Hastings. exceptional post as always!

Why did you have to quote Tamara's (excellent) long post eh but add nothing to it?.....I scrolled through with bated breath only to hear a ping on my phone with the dreaded notification from o2 to say that I've gone over my data allowance thanks to you, and my next bill will have far too many zero's....thanks a bunch .....I'll fetch me coat ...... 🤣

 

nice model outputs so far today, a settled spell in the offing for many parts, with temps hovering around the 70F mark for my locale......lovely!

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