Model Output Discussion - 1st August 00z---------->

[Frosty.]

Nice influx of heat later next week across the south of the uk from the Ecm 12z with temperatures potentially into the low 30's celsius further s/e on Thursday but with increasing humidity an increasing chance of T-Storms being sparked, thereafter temps drift back down into the low 20's celsius but the week ahead looks good by late summer standards, especially across the SE where it's set to become very warm or hot for a time.

[summer blizzard]

Both the Euro and GFS attempt to try rebuild pressure by day 10 after loosely breaking down. Nothing spectacular temperature wise though.

[Singularity]

Back to the Models please. If your post is missing it's here https://forum.netweather.tv/topic/82655-model-banter-moans-and-ramps-springsummer-2015/page-71#entry3243685

 

Thanks, PM.

 

Thanks, that explains one of mine... 

 

- - - - - - - 

 

 

Anyway, looking at the ECM 12z operational for Thursday 13th, it has an exceptionally deep and intense storm system just southwest of Iceland (see image below), which being so extreme does give cause to question the extent to which the trough is able to nudge the Scandi High to the east over the following few days.

 

A weaker trough is likely to make at least a little less progress - in the spirit of the GFS 12z operational output.

 

 

Despite their differences, both of those two models have substantially shifted the balance of power from the Atlantic trough near/over Iceland to the Scandi High, when compared to their output 12 or 24 hours ago.

 

 

It seems that the broad-scale signals for mid-August are changing in important ways. The venture of the MJO into phase 6 may be having some effect (http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ALL_emean_phase_full.gif) but I actually (rightly or otherwise...) see an adjustment upward in the expected atmospheric angular momentum as a more significant player:

 

 

...as I have heard it said that this encourages troughs near the UK to trend further west with time, though the means by which that takes place is something I've yet to get my head around (but posts by the likes of Tamara have assisted greatly over the past year or so). 

Edited August 9, 2015 by Singularity

[Man With Beard]

Big pattern change coming if NOAA is to be believed (and it has some support from longer range ops today, too) - Euro heights take a beating around next weekend. Euro heatwave coming to an end?

[johnholmes]

NOAA 6-10 and 8-14 have been fairly consistent with this happening for several days so it is odds on it occurring. It has been a very slow process but the consistency has been there. I suspect it may take the full 10-15 days before away from the western edges of Europe it extends well into mainland Europe.

links below

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

no GFS

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

[Singularity]

The 18z GFS operational takes the deported heat as far north as Svalbard (much diluted by then of course):

 

 

This is largely down to the Atlantic trough jumping back south again when compared with the 12z. Seems that its behaviour is anyone's guess at the moment.

[mushymanrob]

Big pattern change coming if NOAA is to be believed (and it has some support from longer range ops today, too) - Euro heights take a beating around next weekend. Euro heatwave coming to an end?

 

hi

not sure i understand what you mean here... i cant see a big pattern change, all i can see is a large northern/scandinavia high, a strong azores high, and a mean upper trough to our northwest. this pattern has been in place about a week now and doesnt look like changing, if the 8-14 day chart is anything like accurate.

 

to me it suggests a slight westard pressure build and pressure not as low over the uk as the 6-10 day mean suggests

something not a million miles away from this chart (current gfs 00z for day 11, central to the 8-14 day chart), is likely?

until then, we appear to be repeating this summers general pattern, ridging off the azores high bringing temporary pleasant condition before that collapses allowing spoiling frontal systems to bring breezy, cloudy, and wet conditions across the uk. rain amounts never seem to great though and the dry, hard ground doesnt look like becoming soggy just yet. unless of course that nasty little area of low pressure that develops over biscay later in the week delivers a lot of heavy thundery rain.

for once its looking better in the northwest then it does the southeast!

 

[Gibby]

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 08:00 ON SUNDAY AUG 9TH 2015

 

THE CURRENT GENERAL SITUATION. A moist SW flow covers the UK today as weakening fronts move SE over the UK. Another front will move NE over Southern areas tonight followed by a fresher westerly airflow later tomorrow.

 

http://www.wetterzentrale.de/pics/Rtavn001.gif 

 

MODELS-2 WEEK HEADLINE Remaining rather changeable with some rain at times. Some dry and at times warm, humid conditions are likely for all areas as well.

 

THE GFS JET STREAM FORECAST The GFS Jet Stream Forecast shows the flow moving NE across Britain over the next few days moving SE and weakening.The main arm of the flow then dives SE towards Spain later this week with the UK lying under a trough. This pattern changes only slowly in Week 2 with what flow there is continuing to reside further South than is ideal for good weather across the UK.

 

http://www.netweather.tv/index.cgi?action=jetstream 

 

GFS OPERATIONAL The GFS Operational Run today shows the SW or west flow of the next few days weakening away by midweek as pressure builds across Central areas midweek. A thundery Low pressure area is then shown to feed north from France and amalgamates with Low pressure from the NW by the weekend with the whole complex system lifting North out of Britain next weekend. So after a some rain at first Central regions dry up midweek before thundery showers in warm and humid weather affect the South. Later in the week bith thundery weather in the South and Low pressure fronts from the NW give an unsettled and cooler spell for all before the North see a fine settled period in the second week, at least for a time before a rerun of week 1 looks likely as thundery low pressure moves up once more from the South

 

http://www.wetterzentrale.de/pics/Rtavn1441.gif

 

http://www.wetterzentrale.de/pics/Rtavn3841.gif 

 

THE GFS CONTROL The GFS Control Run is quite similar in structure but is less bullish about the influence from both thundery low pressure from the South and the NW later this week with generally slacker conditions giving rise to less outbreaks of rain and more in the way of benign weather types right out to the end of the run.

 

THE GFS CLUSTERS(14 Days) The GFS Clusters this morning for 14 days show quite an even split between fine conditions under a ridge especially over Southern Britain in two weeks time and an equal split in members who prefer more unsettled weather under Low pressure close to Northern Britain

 

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=372&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

 

UKMO UKMO today shows a ridge of High pressure developing across Central Britain midweek with thundery low pressure moving up from the South. Then later in the week pressure falls from the NW too ending the run in a complex Low pressure zone near to South-east and NW Britain bringing cooler air to all with thundery rain at times next weekend.

 

http://www.wetterzentrale.de/pics/Rukm1441.gif 

 

THE FAX CHARTS The Fax Charts this morning show a wrath of fronts crossing east and SE across Britain over the next 48 hours followed by a simplification by midweek as pressure builds across central areas and thundery Low pressure brings further fronts North into Southern Britain at the end of the week in warm and humid Easterly winds.

 

http://www.weathercharts.org/ukmomslp.htm#t120.

 

GEM GEM today follows a similar route to the rest edging thundery rain up into the South later this week as the current SW flow weakens over the coming days and pressure builds briefly across Central Britain. Thereafter Low pressure from both the SE and NW combine to bring a spell of more unsettled and cooler conditions as winds settle Westerly from next weekend.

 

http://www.wetterzentrale.de/pics/Rgem2401.gif 

 

NAVGEM NAVGEM keeps the axis of low pressure further to the east than the rest with the same ridge as other output shows midweek lying across Central areas. With the axis further to the East less effect with regard to thundery rain or rain from the NW looks likely with drier weather and more sporadic showers likely for a time later this week before a North/South split develops again by the end of next weekend with most rain by then in the North and West

 

http://www.wetterzentrale.de/pics/Rnvg1681.gif.

 

ECM ECM this morning shows the thundery Low further to the West over France than NAVGEM with the resultant weather being more thundery over the South from midweek edging North. As pressure becomes slack and eventually High to the NE many northern areas will see the best of the conditions later in the period with some warm sunshine and mainly dry conditions. Southern and especially SW areas of the UK later will always lie at risk of further thundery conditions especially late in the period as pressure falls over the SW approaches.

 

http://www.wetterzentrale.de/pics/Recm2401.gif

 

ECM 10 DAY MEAN The ECM 10 Day Mean Chart  from last evening maintains the general theme of Low pressure to the NW and High to the SW maintaining a slack Westerly feed across the UK with the best conditions likely to be towards the South outside of any thundery outbreaks in any warmth fed up from Europe

 

http://www.wetterzentrale.de/pics/Reem2401.gif 

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The models trend changeable today with various options between the models desiring a return to Atlantic airflow domination in the long term.

 

31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKMO & ECM The Verification Statistics of GFS, UKMO and ECM. This morning's verification statistics show ECM leading the way at 3 days with 95.9 pts followed by UKMO at 95.4 pts and GFS at 94.6 pts. At 5 days ECM is stll king at 86.0 pts followed by GFS at 84.2 and UKMO at 84.1 pts. Then at 8 Days ECM still leads at 58.1 pts over GFS's 54.1 pts. Finally at Day 10 ECM leads GFS at 40.0 pts to 33.2 pts from GFS.

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day3_PMSL_MSL_G2NHX.png 

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day5_PMSL_MSL_G2NHX.png

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day8_PMSL_MSL_G2NHX.png

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day10_PMSL_MSL_G2NHX.prig

 

MY THOUGHTS There is some coming together of the output this morning, certainly within the first week although with small synoptic differences still present from some output could have radical effects n local differences in weather at the surface. In general this week looks quite warm and humid especially at first and again from midweek in the South. early rain in the South should give way to brighter and fresher weather over Tuesday and Wednesday as ridge builds across Central Britain. Pressure will then fall across France and it looks increasingly like it could turn quite thundery across Southern Britain from midweek. In addition the ridge across Central regions where it could be quite a dry week will be superseded by Low pressure from both the SE and NW next weekend probably forming a Low complex near to our shores with a cooler and unsettled phase next weekend. This is where the togetherness in the models fall apart as a variety of options are shown then ranging from a return to a North/South split in conditions to a generally more unsettled period as Low pressure close to the North return westerly winds and rain at times for many. However, I strongly believe that Week 2 belongs in never never land at the moment and until the fine detail of the latter stages of this week are sorted Week 2 could go one of many ways at the moment. However, looking at what looks more certain this week many places will end up warm and humid but unless the sun breaks up a lot of the predicted large cloud amounts high temperatures will be very localised and when thundery rain comes along later in the week in the South some redress of balance in rainfall amounts between north and South looks likely. All in all then a typical August week to come with something for everybody but never overly cool or wet.

 

Next update from 09:00 Monday Aug 10th 2015

[bluearmy]

The troughing into Western Europe and well into the med is a big change. the ECM op first to pick up on the drive of lower heights in a se direction from the Atlantic trough. it's been a hot dry 8 weeks in Iberia and the western med. all change!

[knocker]

Well just to add the ECM anomaly picked it up two days ago.

Chart weatherbell

Edited August 9, 2015 by knocker

[Man With Beard]

Mushy - please see Bluearmy/Knocker's posts, this is exactly what I meant.

I still wonder if there are further developments to come with this surface low to the south midweek - seems to be even further east on GFS this morning - small changes in positioning and intensity will make for huge local variations. I still think it may not even develop at all and stay south until the incoming trough in the Atlantic sweeps it up on Friday or Saturday. I wonder if Wales / NW England will see the best of the weather from midweek, if not the highest temperatures?

Further ahead, GFS yet again keen on repeating the pattern of developing small troughs to our south. Could be a warm and stormy (thunder variety) two weeks

[Frosty.]

There is a lot of fine and warm late summer weather on the Gfs 6z but there is also some humid thundery conditions, especially through the second half of the week further south when it's set to become very warm / sultry across the south of the UK, heavy rain in the south sweeps northwards into scotland by the end of the working week. Looking further ahead, the 6z shows high pressure in the ascendancy with nice warm temps comfortably into the mid 70's F and largely fine and sunny conditions but becoming more unsettled across northern UK later.

[legritter]

There is a lot of fine and warm late summer weather on the Gfs 6z but there is also some humid thundery conditions, especially through the second half of the week further south when it's set to become very warm / sultry across the south of the UK, heavy rain in the south sweeps northwards into scotland by the end of the working week. Looking further ahead, the 6z shows high pressure in the ascendancy with nice warm temps comfortably into the mid 70's F and largely fine and sunny conditions but becoming more unsettled across northern UK later.

Just about to post a similar post ,so yes warm air becoming established with usual weather i e thundery spells ,then more of our usual 2015 summery weather .

if all of us can get something a little more generally dry and warmer weather to finish our summer apart from places further north it could turn out not to bad ,cheers gang .

[Tamara]

In the context of discussions in recent days about El Nino, AAM and anomalous amplified troughs and ridges then looking back at my posts attempting to document progress through the summer I think this one was quite pivotal.

 

https://forum.netweather.tv/topic/83255-model-output-discussion-1st-june-2015-12z/?view=findpost&p=3221175

 

The Atlantic sector pattern at this time suggested to go the favourable route for the continental heat courtesy of ridging over Europe to extend over greater parts of the UK. What happened as we know was different.

 

The reasoning is quite straightforward when broken down into simple English. It also should help illustrate why there is never any direct 100% correlation between macro ocean/atmosphere states and resultant synoptic patterns. It furthermore illustrates another good reason why the Global Wind Oscillation is such a useful guide in terms of interpreting where and when these variations may occur

 

Lastly, but perhaps more importantly, such tools as valuable as they are, will always give very good guidance to macro patterns but cannot provide specific micro detail forecasts for the UK (as one very small fragment of the NH) and for that matter other boundary fringe areas where the jet stream, next to a large ocean such as the Atlantic will always determine those precise specifics in terms of placement of pressure systems - and dictate the consequential fortunes of whether one is north, south or directly under the Jetstream.

 

This complex scenario conundrum fully epitomises a summer like 2015 for the UK and the position it holds at a geographical crossroads for weather types. The UK has been the precise crossroads of fortunes for Europe as a whole this season.

 

It was (relatively) more straightforward in the Spring with a decoupled atmospheric negative GWO/AAM state to the El Nino ocean state which kept the UK and much of Europe homogenously cool. But the second half of June into the start of July saw what had been coming for some time - decisive coupling of the atmosphere to the ocean state through intense tropical convective forcing through the Pacific and a breakthrough in upwards tendency in AAM after months in a depressed La Nina-esque state. 

 

This breakthrough state however was more potent than envisaged - and involved a record MJO Phase 7 amplification with deep convection imprint on the atmosphere in the passage of the convective wave through the Pacific. It was actually too much of a of a good thing for the UK because although it assisted blocking, it has, largely, put the blocking in the wrong place (for warm and dry summer weather fans)

 

This is where the relevance of eastward and northward propagating Rossby wave influence lies, as talked about in previous posts, in determining large scale global patterns which subsequently transcend the macro pattern to the more micro one - depending, globally, often where tropical convection is based around the ring of tropics.

 

In very simplistic terms (it is more complex than this!) for the purposes of the Atlantic sector, and Europe (but most especially the UK next to a large ocean) the further west the tropical convection forcing is based, the less poleward momentum transport there is to our closer higher latitudes. In very crude terms to keep it (very) simple, for summer fortunes a position based around the maritimes is most beneficial for wave activity to pump up anticyclones from the sub tropics to mid latitudes (i.e ridging from the Azores edged east to influence the UK and NW Europe).

 

However, stronger tropical convection forcing further east through the Pacific, with the MJO into Phase 7/8 will see augmented Rossby wave activity to higher latitudes in our sector. This raises pressure over the pole (hence the predominant -AO profile through the heart of this summer) and also upstream increases the sub tropical jet stream with the result that ridging downstream in the Atlantic sector is supressed and flattened and the main downstream warm/hot anticylonic amplification occurs further downstream over central/eastern Europe

 

So there is not necessarily any one size fits all synoptic pattern to any given ENSO state, let alone El Nino. We also have to take into account seasonal wavelengths - and these can be provided through the guidance of GWO composites (adjusted to the appropriate 3 seasonal months)

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/composites/JFM/hgt500_1.png

 

The upper air anomaly charts will give good appropriate guidance for the short medium terms, but they will be influenced increasingly by the direction of travel of the greater atmospheric circulation pattern - and this is where the GWO can be especially helpful

 

+AAM is associated with westerly wind bursts across the tropics and sub tropics which are very characteristic of an El Nino coupled ocean/atmospheric circulation regime. However, regional area variations over oceans and continents will affect how synoptic patterns distribute themselves over much wider areas further away from the original forcing source.

 

Essentially the stone and ripple effect on the pond

 

It has been an active season for Pacific storms this summer. Such Pacific storms involve the creation of strong frictional stress signals and are superimposed onto existing AAM signals as determined by the background flow.

 

So, strong eastward and northward propagation of wave activity from the tropical convective forcing boundary, which pumps up anticyclones at determined latitudes, and augment troughs at others, are further complicated by the net frictional "sink" source of more 'local' Typhoon activity and also are part of overall GLAMM budget (beyond just the westerly wind transport momentum of the atmosphere) in line with the Pacific El Nino state.

 

The combined effects of these large scale frictional effects on the AAM budget are very likely linked with jet stream signals at upper tropopause level, but they also must be connected with the lower boundary where extreme torques act to either remove or add AAM. The basic principle of constant flux and Mother Nature not allowing a vacuum clearly underlined here. These are basic principles of AAM  - and thus also must be principles of basic physics

 

So, a lot of combined ocean forcing in play which affects the overall AAM budget and the trajectory of the jet stream upstream from us. But frictional torques have land based effects as well in the form of Mountain torques. Jet streams plough into high mountain ranges and provide another source of Rossby wave activity that affects the jet stream ribbon and also part determines the placement of troughs and ridges around the globe. 

 

The GWO orbited amplified Phase 4/5 in late June in response to the MJO picking up forcing amplitude significantly through from the Maritimes onwards through the Pacific. The response to this was mid latitude wave activity momentum transport that created the Sceuro ridge and the hot plume at the end of June/early July.

 

Phase 4 into 5 signifies the engagement of an + East Asian Mountain Torque (EAMT)  ,

.

What happened thereafter is that the MJO continued to gain amplitude onward through the Pacific and this increased wave activity in our sector further poleward and created heights to our north (with the AO taking a dive accordingly). At the same time, the effect upstream of the Asian torque was to accelerate the Pacific Jetstream downstream from it, further accelerating the rossby wave action of poleward higher latitude AAM transport (to increase arctic blocking) and add strength to the sub tropical jet stream across the US and downstream to our Atlantic sector.

 

The Global Wind Oscillation reflecting this by moving from Phase 5/6 through high amplitude Phase 7/8 as we went through July.

 

The flattened pattern through active STJ and amplified heights to our north pushed the end June/early July mid latitude hot ridge amplification south and east into Europe. This manifested in the cooler and more widespreadly changeable pattern of the second half of July - more especially the last week.

 

So to try and put all this recent synoptic history together, +AAM is favourable for blocking patterns per se as we can see through the poleward rossby wave action it brings. But from documenting the events of July what we also can see is that the degree of amplification and wave activity, and where the subsequent amplification(s) occur which will determine who, and where, is affected by the troughs and ridges - and which side of the jet stream they lie on.

 

In our case, a strong westerly jet in summer with blocking in the wrong place (for summer) over the pole is not going to assist the advection of heat to our south - with the main ridge kept too far away from us to our east and south. 

 

The argument therefore is that El Nino can be best for very amplified MJO spikes in the Pacific in winter - when heights to the north and a southerly tracking jet stream are much more popular for obvious reasons. On the other side of the coin, tropical convection forcing too far the other side of the globe over the Indian Ocean will assist the development of tropical ridges northwards - but it will also serve to retrogress those ridges well to our west so that we are on the 'cool' side of mid latitude anticyclones with a propensity for troughs to drop into the space (the UK especially)

 

A typical -AAM type synoptic chart from the Spring - with the retracted Azores High and the strong upper Canadian trough flooding the Atlantic with cool air

 

http://modeles.meteociel.fr/modeles/gfs/archives/gfsnh-2015052800-0-6.png.

 

Somewhere ' in between' could be simplistically argued best to get the right amount of poleward propagation to inflate anticyclones in the 'right place for warmth in summer - i.e over or just to the east of the UK and NW Europe - but not too much poleward AAM so that (in summer) the heights occur over the pole instead, depress the Jetstream and flatten the pattern.

 

These descriptions have been deliberately over simplified for purposes of explanation. There is, as ever, more to it than this and we can look towards the effects on rossby wave activity through the tropical zone wind QBO phase state (we are transitioning from -QBO to +QBO) as well as the obvious effects on jet stream amplification through arctic sea patterns and subdued solar forcings - but the large scale atmospheric circulation, as described, is plenty reason in itself for the divided boundary that has been the UK this summer - between the heat to the SE of the UK and the cooler moist atlantic to our west and NW.

 

Looking ahead - current NWP modelling suggests the upper trough linking into Europe and eroding the heat is a replica response to the GWO re-tracing Phases 7/8/0.

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png

 

 

However, with MJO forcing much more repressed in the Pacific than July, returning westwards at low amplitude, and not expected to play much significant part synoptically - then a further widespread longer lasting breakdown beyond the current warmer more settled spell such as seen in July is less likely.

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ECMF_phase_51m_small.gif

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/NCPE_phase_21m_small.gif

 

Some attempts at raising heights over the pole again, but neutral/positive AO mainly prevailing. A further SE/NW spilt probably re-commencing with the base ocean/atmosphere state keeping control.

 

With this in mind, worth again also taking into account GEFS  -AMM tropical forcing forecast bias. 

 

This re-spin cycle probably seeing out the summer. Those in Europe shouldn't expect any pause in their remarkable heat wave to last especially long. At the other end of the scale, more potential cool and changeable/unsettled frustration to the NW.

 

But that is beyond the coming week which although still features rain/showers somewhere in the UK on various days, should also provide something better for most at some time

 

 

[Skullzrulerz]

Today's Wxmpas show a almost N/S of Temperature once again with the warmest temperature in the south east.

​​

 

Also To add Gavin's thoughts on the "BCC" model for this rest of august (which at best is changeable) and a peek into winter.  

 

Edited August 9, 2015 by Skulltheruler

[knocker]

All this talk of regime change obviously doesn't apply to the the GEFS and the ext ECM anomalies or the the EC32 for that matter unless the withdrawal of the upper trough to a weakened position around Iceland. creating a more zonal flow around the Azores ridge but keeping the Scandinavian ridge, counts. Albeit weakening the latter around day fifteen. Not an unfamiliar scenario. Could be quite a neat trick by extending the upper trough south, establishing lowish pressure in western Europe, and then cutting it off at the pass.Do I spot a moveable latitudinal transition between the cold and warm air commonly known as a N/S split?

 

http://www.tropicaltidbits.com/

Edited August 9, 2015 by knocker

[mushymanrob]

Mushy - please see Bluearmy/Knocker's posts, this is exactly what I meant.

 

 

i see , cheers..

but wouldnt the 8-14 dayer suggest the troughing over western europe is less intense then what the 6-10 day chart shows?

[Frosty.]

It's really encouraging to see the gfs is sticking with a change to warm anticyclonic conditions during w/c 17th August with high pressure building in to bring a week of settled and warm / very warm weather to most of the UK, I hope this trend continues to firm up, great charts for week 2 on the Gfs 12z.

Edited August 9, 2015 by Frosty.

[johnholmes]

i see , cheers..

but wouldnt the 8-14 dayer suggest the troughing over western europe is less intense then what the 6-10 day chart shows?

 

That is a feature of any 8-14 in about 8 cases out of 10. The 'meaning' seems to show a less deep trough or intense high and lower values of both + and -ve heights. What one is looking for in the 8-14 is, either a marked change from the 6-10, rare that happens but it does now and then, or, a continuation of the 6-10 overall pattern, including moving troughs and riges if the wave length is the right length.

[Singularity]

The MJO is currently hanging around at  relatively low amplitude in phase 6... the placement is very good for warmth to occur this time of year (based on the composites at http://www.americanwx.com/raleighwx/MJO/MJO.html), and although the amplitude is low, we are seeing suggestions in the model output of high pressure to our E/NE which does tie in nicely with the phase 6 composite for amplitudes greater than 1.0:

 

 

 

Incidentally phase 7 in July has a similar appearance, as does phase 8 in June. Shifting by 1 phase each month... coincidence? 

 

Anyway, it will be interesting to see how soon the MJO leaves its current state, as it's spent the past 24 hours drifting in the opposite direction to what the models predicted would be the case. If it lingers for much longer, we could perhaps see high pressure to our E/NE proving increasingly stubborn in the model output.

 

 

Shorter term, we already have a lot of uncertainty to contend with thanks to the anticipated low pressure over NW Europe. For example, while GFS has the system pushing in late Wednesday and crossing England on Friday, UKMO delays the arrival by at least one day and then moves it to our SE on Saturday, managing to do little more than introduce some instability to the atmosphere overhead.

 

This by and large looks to be a consequence of low pressure near Iceland being held back further west by UKMO, the difference notable as early as Thursday. Having said that, GFS' 00z operational run had the low in a similar place to UKMO's 12z, yet the European low still pushed north(east) sooner. Perhaps it simply reflects differences in the model physics. In such situations, we often see GFS and GEM in one camp and ECM and UKMO in the other. The GEM 12z operational is similar to GFS so that's half of the equation in place... let's see what ECM comes up with later this evening.

 

 

Considering the GEFS ensembles with respect to the GFS and UKMO operational runs, the spread of outcomes (see below - showing the range of 500mb heights across the ensemble suite) regarding the European low is not particularly large on Friday, just about encompassing the UKMO operational along with the GFS.

By Saturday it has become much, much larger... unusually so for less than a week ahead. Clearly the advance of the Atlantic trough is a long way from sorted out:

 

 

 

By the way, if I could do with explaining anything in my posts further, please don't hesitate to ask - I'm still getting used to sharing my analysis in this way 

[knocker]

The GEFS anomalies tonight are a continuation of it's recent theme. Taking the trough down through NW Europe to the MED. by Saturday. But after that slowly withdrawing it towards Iceland allowing the Azores ridge to gain influence once more by Weds.. thus after a period of unsettled weather a return to more pleasant settled conditions. How far north is still open to conjecture. The 11-15 does continue the settled weather to include Scotland.

http://www.tropicaltidbits.com/

 

[knocker]

I think NOAA is moving in the direction of the GEFs and relaxing the upper trough and allowing more influence from the Azores and slightly veering the upper flow. Which can only be good news for those living further north.

Edited August 9, 2015 by knocker

[mushymanrob]

That is a feature of any 8-14 in about 8 cases out of 10. The 'meaning' seems to show a less deep trough or intense high and lower values of both + and -ve heights. What one is looking for in the 8-14 is, either a marked change from the 6-10, rare that happens but it does now and then, or, a continuation of the 6-10 overall pattern, including moving troughs and riges if the wave length is the right length.

I suspected the 8-14 day would be rather uncommittal, and not be the chart to pick up on anything major as its obviously a mean in fi.

Insaying that, todays 8-14 chart seems at long last to support some sort of pressure rise over the uk, which if verifies could lead to the first nationwide settled spell of the summer?

[Frosty.]

The GEFS 12z mean shows increasing Azores high influence for most of the UK looking beyond the week ahead which I think is good news.

[mushymanrob]

The GEFS 12z mean shows increasing Azores high influence for most of the UK looking beyond the week ahead which I think is good news.

Tbh mate, its been doing that all summer and so far has failed to deliver......