Model Output Discussion - 31/8/14 Onwards.

[Captain Shortwave]

Out of all the models, the GEM looks really out of kilter 

Even at day 6, the Atlantic jet is far weaker than the other models, hence a more amplified split flow. I would probably call this a rogue run for now, I would put the odds at 50:50 to whether the Atlantic properly gets in next week.

[phil nw.]

GFS/ECM 12z Op runs for next week look in better agreement with the Atlantic pattern.

GFS around day 7 has moved the jet further north than the 00z run and close to what the last 2 ECM runs have shown.

On this basis the more unsettled conditions hold further north with a flatter looking high close to the south gamely hanging in there for a while longer.

 

 

CPC forecasters are still expressing low confidence though in the week 2 wave pattern because of the lack of recent run to run consistency from their outputs.

Part of their report below

 

"FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: MUCH BELOW AVERAGE, 1 OUT OF 5,
DUE TO HIGH SPREAD AMONG TODAY'S ENSEMBLE MEMBERS AND POOR CONTINUITY BETWEEN
TODAY'S AND YESTERDAY'S FORECAST TOOLS 

 

A glance at the NH pattern at T168hrs by the GEF stamps show the uncertainties with the jet pattern.

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=168

 

A more volatile period for modelling i suppose with the change over of the seasonal wave patterns as the PV starts to cool and expand,gradually extending it's influence further south over the coming weeks.

 

Probably safe to say that the trend to the westerlies continues for next week but it may well be a gradual process starting further north with high pressure keeping things reasonably dry for the south for a few more days at least.

[knocker]

The anomalies are in broad agreement for next week with a swathe of low pressure lying to the north but the ECM puts more emphasis on the Azores high which broadly speaking has the surface high pushing closer to the UK. The jet doesn't really support the high progressing further although looking further ahead with the ECM anomaly this is contradicted so as of the moment  it's by no means certain how big a role the Atlantic will play but I'm inclined to agree with Phil that the south could well remain reasonable dry,

Edited September 17, 2014 by knocker

[johnholmes]

 

 

A more volatile period for modelling i suppose with the change over of the seasonal wave patterns as the PV starts to cool and expand,gradually extending it's influence further south over the coming weeks.

 

 

 

very true comment there phil. The anomaly charts are often at 6's and 7's in this spell, without any complication from any tropical storm/hurricane. A similar thing occurs most times as we go from winter to summer with the polar set up.

This makes predicting beyond day 5 much of the time more fraught than usual, and that for the upper air pattern never mind the much more complex surface pattern.

[BlueHedgehog074]

Thanks DRL

Anytime, Frosty.

Not really much else to add regarding the models, but a quick flick through the GFS, the ECMWF, and the UKMO, does confirm that the blocking High Pressure over (and to the North-East) of the UK will become under threat from vigorous Low Pressure systems out to our West next week. The risk of Atlantic Lows crashing back through means we will loose the slack North-Easterly/Easterly/South-Easterly airflow the UK will have had this week with some sort of Westerly flow returning. Certainly looks as though Southern areas may never be too far away from High Pressure to the South and South-West and could stay quite dry, while Northern areas could be more vulnerable to disturbed weather from the Atlantic Lows. Perhaps still enough room for the increased mobility in the pattern next week to alter somewhat, such as how far North the Atlantic Lows could track and/or whether some noticeable amplification could arise from the flatter, Westerly, pattern (I suppose providing the Jet-stream doesn't constantly become too straight and powerful, even though it does look as though the Jet will power-up towards us next week).

Also still the risk of some thundery and showery weather from that Low to our South-West for Southern areas for the next few days according to the GFS 18Z Precipitation charts. The CAPE/Lifted Index values continue to look quite reasonable, too.

An example for Friday afternoon (still liable to change):

[IDO]

GEM is similar to the 12z with holding the Atlantic at bay still by D10.

 

D7:  D10: 

 

The GFS op continues yesterday's back track with regard to the Atlantic train, with higher pressure over most of the UK through to D16 apart from a short wave trough around D7:

 

 D10:   D16: 

 

The control is not dissimilar. It is fair to say that the GEFS remain scattered with regard to how far the Atlantic encroaches south on D7. The London pressure graph:

 

 

The NOAA 8-14 day hints at the core lower heights around Iceland that could lead to a N/S split re the westerly flow: 

 

D13 GEFS mean leaning that way:  D10 ECM mean 12z: 

 

Though both the hi res GFS runs suggest a more amplified pattern:   

 

The ECM at D7:   D8: 

 

D9:   D10: 

 

As the AO has been suggesting a positive spike around D7 as a wave of lower pressure spills east from the NW. It looks like it will give a couple of days of wet weather but its north/south boundary remains fluid. Then looking like higher pressure returns to the south and possibly the north. The improvements continue.

Edited September 18, 2014 by i'm dreaming of...

[Frosty.]

It's clear that the Gfs 00z op run is trying to plunge the uk into a full blown much cooler, windier and unsettled outlook but high pressure keeps fighting back, even when the odds seem against it, however, this run would represent the most autumnal weather since..Errr August and the atlantic really goes through the gears, really cranking up but mainly targeting the north, high pressure tries to gain a foothold across the south on a few occasions, the first half of next week looks pleasant with high pressure but chilly nights with single digits celsius minima and early october looks pleasantly warm and settled with HP in control but there does look like being a big swing towards cool and unsettled weather later next week onwards..we should all notice a BIG difference towards the end of next week.

 

oops, charts are all over the place..sorry guys

Edited September 18, 2014 by Frosty.

[Summer Sun]

UKMO this morning shows winds gradually shifting round to north westerlies

 

Monday starts with high pressure over the UK with temperatures still very respectable for the time of year although not as high in the south as we've seen of late and will do so for the next couple of days

 

 

Into Tuesday and pressure begins to fall an increasing risk of some rain in the north but the south should remain mostly dry. No 850's available but I suggest temperatures will be falling slightly 

 

 

By Wednesday we have north westerly winds so cooler for all, however high pressure remains very strong to the south west so it may not be long till settled weather moved back in

 

Edited September 18, 2014 by Summer Sun

[knocker]

The ECM 5 day anomaly this morning has a persistent HP area North America and central Atlantic. The jet is thus in almost a meridional set up with the low pressure in the colder air. On the surface this tends to negate any major ingress by the Atlantic with most of the UK still feeling the benefit of the HP.

[knocker]

The ECM ens in general supports the ops although at this range, being a bit of a knife edge situation, I wouldn't bet the bank on it. Further out it's going for a more zonal pattern.

Edited September 18, 2014 by knocker

[shaky]

The ECM ens in general supports the ops although at this range, being a bit of a knife edge situation, I wouldn't bet the bank on it. Further out it's going for a more zonal pattern.

to be fair knocker this supposed breakdown is getting pushed back by the day!!!and also if it does happen it looks it wont be anything major rainfall wise and pressure might rise again straight after!!!unless things change am afraid this dry weather aint ending anytime soon!!

[Frosty.]

The Gfs 06z op run is much more unsettled than the 00z, no middle ground with this run, high pressure hardly gets a look in and apart from early next week when we have pleasant conditions but with chilly nights,  only appears again as a transient feature at the very end of low res. This run is showing the north atlantic (northern arm of the jet) firing up and firing depressions our way from later next week as heights fall significantly to the NW, the first low, a vigorous looking feature, close to the southern tip of greenland swings southeast towards the uk and is then followed by another and then another, so it's trending cooler, windier and wetter, especially the further north you are from around the middle of next week onwards - proper autumn weather is on the way.

Edited September 18, 2014 by Frosty.

[Polar Maritime]

Yes Karl, The GFS so far has been pretty good at handling this pattern change, With the 25/26th onwards continuing to look very Autumnal indeed. Small changes to the Low N/S a few hundred miles could make all the difference. 

 

Edited September 18, 2014 by Polar Maritime

[phil nw.]

A post discussing Winter prospects has been moved to the correct thread here

https://forum.netweather.tv/topic/81288-early-winter-hopes-and-chat/

As we have that dedicated thread we can concentrate on the next 2-3 weeks in here.☺

[IDO]

Yes Karl, The GFS so far has been pretty good at handling this pattern change, With the 25/26th onwards continuing to look very Autumnal indeed. Small changes to the Low N/S a few hundred miles could make all the difference. 

 

 

 

The 06z GFS OP is an outlier and I would not take too much notice. It is predicting 2m temp highs on a couple of days in London of 12-13c in week 2:

 

 

Not saying a longer spell of zonal weather is unlikely as it is about 50% on the ensembles (06z) for washout territory. The 06z mean is no where near as unsettled:

 

D8:   D12:  D16: 

 

It is more in line with this mornings 0z run of a few days of wetter weather around D7 then improving via N/S split.

[Andy Bown]

Can I ask something in relation to the below quote, how can anyone say a model has handled a pattern change well when it hasn't happened? Surely that can only be stated once we get to a week today?

Yes Karl, The GFS so far has been pretty good at handling this pattern change, With the 25/26th onwards continuing to look very Autumnal indeed. Small changes to the Low N/S a few hundred miles could make all the difference. 

[Polar Maritime]

Can I ask something in relation to the below quote, how can anyone say a model has handled a pattern change well when it hasn't happened? Surely that can only be stated once we get to a week today?

The GFS picked the pattern change up last week, And has stuck with it, While the other Models have played catch up. So imo the GFS has/is handling the predicted pattern change "well", I will add "so far" to avoid confusion.

 

The 06z GFS OP is an outlier and I would not take too much notice.

Yes I'm Dream, As i said a few hundred miles N/S can make all the difference. But the general theme is still there, I tend to only really look at  0z & 12z runs in detail, With more usable input from them which is handy as i'm usually to busy mid-day.

Edited September 18, 2014 by Polar Maritime

[Frosty.]

 

 

Yes I'm Dream, As i said a few hundred miles N/S can make all the difference. But the general theme is still there, I tend to only really look at  0z & 12z runs in detail, With more usable input from them which is handy as i'm usually to busy mid-day.

Exactly, it's all up for grabs, could become very unsettled or something more middle of the road. IMO the more unsettled 6z is probably quite accurate as far as the north and west of the uk is concerned, wet and windy spells the further NW you are, however, the south and east, especially the southeast could continue to be influenced by high pressure and warmer, fine conditions. In the meantime, an increasing risk of thundery showers across southern uk until the end of saturday, then fine and pleasant from sunday until at least midweek, the north and west turning unsettled with heavy spells of rain either midweek or soon after.

[knocker]

The GFS picked the pattern change up last week, And has stuck with it, While the other Models have played catch up. So imo the GFS has/is handling the predicted pattern change "well", I will add "so far" to avoid confusion.

 

Yes I'm Dream, As i said a few hundred miles N/S can make all the difference. But the general theme is still there, I tend to only really look at  0z & 12z runs in detail, With more usable input from them which is handy as i'm usually to busy mid-day.

 

To be honest PM I haven't seen the ECM attempting catch up . And the NOAA 6-10 last night didn't appear to be either. Of course that could change at 12z.

Edited September 18, 2014 by knocker

[Frosty.]

Anyway, whichever model has this pattern change nailed gfs / ecm / gem / ukmo etc., the met office are going for a very unsettled spell for the NW with gales and spells of heavy rain interspersed with sunshine and showers and rather drier and warmer for the SE with just a few showers.. nw / se split.

[Polar Maritime]

A cooler run from the GFS this evening, With Frosts possible for the spine of the UK. And some very unsettled weather for the Midlands North. High Pressure does try and push back further into the run, But again it looks to only be a transient affair. With a 2nd push from the Atlantic not far behind.

 

Edited September 18, 2014 by Polar Maritime

[Frosty.]

A very cool blast for the north on the Gfs 12z op run although the run overall is less unsettled than the 6z, more like the 0z and early october shows warm and anticyclonic benign conditions with low 20's celsius for the south of the uk.  This run once again shows northern areas and more specifically scotland bearing the brunt of the unsettled, windy and cooler conditions.. the run ends on a high note..literally, so maybe an indian summer in early / mid october.

[IDO]

^^^ Hi PM.

 

Save from T150 to T180, where the North catches a glancing blow from a transient low it is HP all the way:

 

 

 

D9:   D12:  D14: 

 

Most of the coming week is also settled HP dominated.

 

GEM for the third run in a row builds HP to the east/NE,

 

eg D8:   D10 still holding more settled for SE: 

 

Of course things can change but I would say the current momentum is for the Atlantic to not impact too badly, especially the south. We do get the odd outlier like the 06z and the GEFS are not discounting the jet slipping further south, but the hi-res are trending for a continuation of more settled weather.

 

The latest JMA for week 3-4 is not going with a zonal flow with no distinct anomaly for the UK: 

 

The NAO also continuing to hint at a short positive phase:  

 

Still a few more runs needed before we can enjoy further dry weather.

[Frosty.]

I don't think for a minute that high pressure will dominate the outlook, to me it looks like the further north / north western areas will have a very unsettled spell with gales and heavy rain at times, yes the south & east (SE) currently looks the place to be for fine and warm weather and I take a lot of notice of the met office updates and they indicate unsettled weather taking over more and more of the north and west beyond middle of next week, so for the SE there may not be a noticeable pattern change but the NW will feel it.

[IDO]

I don't think for a minute that high pressure will dominate the outlook, to me it looks like the further north / north western areas will have a very unsettled spell with gales and heavy rain at times, yes the south & east (SE) currently looks the place to be for fine and warm weather and I take a lot of notice of the met office updates and they indicate unsettled weather taking over more and more of the north and west beyond middle of next week, so for the SE there may not be a noticeable pattern change but the NW will feel it.

 

Would not argue with that, as the UKMO has a lot more information to hand that we aren't privy to. But bearing in mind what the models were suggesting a couple of days ago us southerners will not be complaining of recent developments

 

GEFS D8 mean:  

Edited September 18, 2014 by i'm dreaming of...