Model Output Discussion 1200 hrs 30/09/14

[knocker]

Last evenings anomalies are in broad agreement. All have a weakish HP western Atlantic and northern Europe with the western edge of the latter influencing the UK with the main feature a trough mid Atlantic. The jet is meridional of moderate strength with some difference of opinion between the GFS and ECM as to the orientation. Thus on the surface there doesn't appear to be much change from the current pattern of a low pressure dominant Atlantic giving periods of rain interspersed with transitory fine spells and around average temps for the UK.

 

 

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY MONDAY OCTOBER 6TH 2014.

 

NEXT UPDATE TUESDAY OCTOBER 7TH 08:00

 

THE CURRENT GENERAL SITUATION. An active trough will cross steadily East over the UK today with an unstable and showery WSW airflow following on behind across England and Wales.

 

MODELS-2 WEEK HEADLINE  All areas look like being unsettled and windy with rain at times in cool conditions. Possibly a little drier and less cool in places later.

 

THE JET STREAM ENSEMBLE FORECAST The Jet Stream remains focused across the Atlantic to be over or to the South of the UK keeping all parts in the cool and unsettled trough like structure for the next week or so. After a brief lull in this early next week the flow re-strengthens strongly across Central UK tiwards the end of the period.

 

GFS The GFS operational today offers a very unsettled and changeable period of weather over the next two weeks. This week's deep and slow moving Low gradually clears away NE next weekend leaving a slack and unstable flow from the West across the UK for a time before more Low pressure delivers more rainfall next week, gradually transferring more towards Northern and Western parts with gales as by the end of the run a deep Low pressure crosses East just to the North of the UK.

 

THE GFS ENSEMBLES. The GFS Ensembles are supportive of the operational in Week 1 with better improvements shown towards the South and East for a time next week as pressure builds temporarily from the South and East. This is then replaced by more Low pressure again moving into the UK from the West to end the run with a return to wind and rain at times for all in blustery West or SW winds.

 

UKMO UKMO this morning keeps a Low pressure belt stretching from the UK to Scandinavia next weekend with further rain at times especially over the South. It will feel cool too though wind strengths will of become less strong by then.

 

THE FAX CHARTS  The Fax Charts continue a very disturbed and complex synoptic pattern all revolving around a deep Low just to the West of the UK by midweek. A series of troughs will affect the South most with heavy showers and more prolonged rainfall at times, some heavy. By the start of next weekend the Low is shown to begin to fill and drift slowly away NE.

 

GEM The GEM operational today looks very Autumnal with little cessation of Low pressure close to or over the UK bringing repeated periods of rain and showers in sometimes cool conditions lasting throughout the next 10 days as the Jet Stream remains further South than normal.

 

NAVGEM NAVGEM gradually takes the deep Low of this week gradually NE by next weekend with winds decreasing away and leaving drier and brighter conditions with a few showers at the weekend as pressure steadily rises. 

 

ECM The ECM operational shows a muted improvement at the weekend as the current deep low pressure zone finally fills and moves away NE. It isn't long though before more Low pressure moves in towards the NW with troughs sweeping East across the UK with more wind and rain for all at times next week.

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS No real change from the previous trends of recent runs is shown today.

 

MY THOUGHTS  The thoughts of the models this morning seem generally supportive of the now more Autumnal type weather pattern under Atlantic Low pressure now continuing largely unchallenged over the next few weeks. There are as always exceptions to this general pattern and it looks like early next week may see a period of rather better weather towards the South and East for a time as pressure builds towards the South and East of the UK. This is by no means a guarantee and is generally chased away anyway by more unsettled and windy weather by the end of next week from those models that show such an improvement. Rainfall amounts will be varied but could be large locally as active troughs pass through or any local heavy showers occur this week. Winds will sometimes be strong especially midweek and perhaps again later next week but a quieter period looks very likely over next weekend. Temperatures though of course lower than of late may end up close to average overall with the coolest conditions within the areas of persistent rain and the warmest weather towards the SE later this week and perhaps again for a time next week though probably tempered by a strong SW breeze then. Fog and frosts will be generally restricted by often too much cloud and breeze so shouldn't be  a major issue through the period. So all in all a typical changeable Autumn period of weather to come for all areas but away from the local wind gusts and downpours I can see nothing particularly noteworthy or disruptive on a nationwide level over the period.

[IDO]

Close to average rainfall for the E/SE for the next 8 days on the GFS: 

 

The west looks like taking the brunt of fronts. Around average (or just above) temps for most on the Eastern/SE areas: 

 

ECM trying to bring some warmer uppers at D8-10: 

 

The CET is still +1.8c so October looking like it may maintain that milder than average pattern.

 

No real change this morning, typical Autumnal week ahead, for most nothing worse or better than average. Front moving quickly through today followed by brighter weather. Then a showery day (Tuesday) before another front clears east Wednesday, Thursday looks the driest and warmest. Still some uncertainty for the LP on Saturday but the trend is for this to downplay for E/SE.

 

Still lots of chopping and changing in FI.

 

 

 

 

[knocker]

The contrasting 850 temp anomalies across North America today.

 

[phil nw.]

The more typical Autumnal Atlantic weather has now set in and does indeed look like the ongoing set up for the next 2 weeks at least.

A look at 3 ECM mean images for today,day 5 and 10 below show the cooling of the upper atmosphere over the Arctic with much lower heights modelled as we go further into the month.

 

 

so changeable conditions off the Atlantic for all.

Bands of rain and showers interspersed with some drier brighter interludes.Temperatures never far from normal but certainly a different cooler feel especially in the rain and wind.

[knocker]

Just to clarify Phil are you connecting the cooling of the upper atmosphere of the Arctic to unstable conditions in the Atlantic?

[phil nw.]

Just to clarify Phil are you connecting the cooling of the upper atmosphere of the Arctic to unstable conditions in the Atlantic?

Just illustrating through the modelling that the Polar Vortex-yes that phrase-is now becoming organised as expected now we  are into mid-Autumn Knocker.

Consequence is a more active jet which of course is  the mobile Atlantic pattern we are now entering.

[knocker]

Just illustrating through the modelling that the Polar Vortex-yes that phrase-is now becoming organised as expected now we  are into mid-Autumn Knocker.

Consequence is a more active jet which of course is  the mobile Atlantic pattern we are now entering.

 

Thanks Phil, I assumed that's what you meant.Certainly not modelling a typical zonal jet at the moment tho'

 

Oh and I came across this yesterday I mean to say.....................

 

I mean, shall we call it the Polar Vortex ?..https://twitter.com/hashtag/Whatever?src=hash

Edited October 6, 2014 by knocker

[IDO]

There is no sign of anything cold from the GEFS at the moment with the uppers looking well above average for the south compared to seasonal average:

 

 

With the Pacific Typhoon, seen at T192:  Really pumping up the Pacific ridge this should keep a meridional flow for much of October. At T252 the wave from this mid-latitude disruption is affecting most of the NH:

 

 

Its where the UK falls in that big picture and that is where the models are currently struggling. The GEFS at T300 (here) show a 33:33:33 split as to whether the UK is under a ridge, trough or something in between (i.e. take your pick). Cannot see at the moment the UK heading into a text book zonal flow and if this comes it may be November time which is worrying for early Winter. Saying that CFS still has November in a more amplified flow and its not till December that it goes zonal, which ties in with last week's UKMO winter update:

 

CFS Nov  CFS Dec:  

 

In the short term an organised cluster of potentially heavy showers heading in from the W/NW: 

 

Possibility tonight and tomorrow for those to be gusty and thundery.

 

 

[carinthian]

I have noticed today the UKMO latest 15/30 day forecast now includes temperatures to be above average later in the period. This falls in with our latest forecast ( Eastern Alps ) for the same period which indicates a 60 % chance of well above average , which is a high confidence level. So reading the latest forecast, I think after the current changeable circulation with-in NW  Europe area, high pressure will settle down again with a probable Southerly component to the wind flow.

C

[IDO]

Just to highlight the uncertainty in the models at the moment due to the Pacific ridge, the 12z GFS now keeps a slack pattern all the way till D12, with weak heights to the north, so the difference between 0z and 12z at D10:

 

  And GEM at D10: 

 

T300 and we are on this run favoured by the meridional pattern:   & D15: 

 

Autumn on hold on this run. All likely to change by tonight again, but still the chance of less unsettled conditions for month's end, and that would tie in with the CFS MJO.

 

 

 

Edited October 6, 2014 by i'm dreaming of...

[ANYWEATHER]

Lots of unsettled weather to come with a real October fest of weather. Looking out to the unreliable timeframe of Day 10 gfs and ecm differ greatly. Gfs on a Scandi high. ecm on the Atlantic train.....    

[nick sussex]

Evening all

 

My first venture into the model discussion  since my summer sabbatical. Just a few words re the model disagreements between the ECM and GFS, essentially we're seeing a divergence of opinion upstream in the USA and Canada which will have an impact on the pattern in Europe.

 

Much depends on the trough set up over there and how quickly any ridge breaks down over the eastern USA. At this stage I'd edge towards the GFS/UKMO solutions at T144hrs, you'll see that they treat the pattern to the ne similarly, low heights there at that stage where as the ECM develops high pressure with weak lows to the sw of the UK.

 

Remembering here that a deeper more amplified troughing set up over the central USA will effect the amplitude of the eastern USA ridge which subsequently effects any troughing to the west of the UK. You can see the differences in terms of amplitude if you compare especially the 192 hrs timeframes:

 

ECM

 

 

GFS

 

 

 

 

 

 

 

[knocker]

Evening all

 

 

Remembering here that a deeper more amplified troughing set up over the central USA will effect the amplitude of the eastern USA ridge which subsequently effects any troughing to the west of the UK. You can see the differences in terms of amplitude if you compare especially the 192 hrs timeframes:

 

ECM

 

ECH1-192.gif

 

GFS

 

gfsnh-0-192.png

 

I think I see what you are saying Nick. No ridge eastern seaboard on the GEFS? I'm not sure how it affects the troughing apart from probably a more zonal jet and thus more mobile troughing?

Edited October 6, 2014 by knocker

[nick sussex]

I think I see what you are saying Nick. No ridge eastern seaboard on the GEFS? I'm not sure how it affects the troughing apart from probably a more zonal jet and thus more mobile troughing?

The troughing in the USA downstream effects the sharpness of the trough near the UK and also the progression of the pattern.

 

The debate really is will the UK end up with the limpet trough over it or will this retrogress with high pressure to the east.

[knocker]

The troughing in the USA downstream effects the sharpness of the trough near the UK and also the progression of the pattern.

 

The debate really is will the UK end up with the limpet trough over it or will this retrogress with high pressure to the east.

 

Yes I agree there as the HP to the east has been hovering, shall we say, for two or three days now. The ECM in particular has been trying to push it further west.

[IDO]

Last night's ECM op was not really reflective of it's mean, op:   mean: 

 

That mean very much in line with the GFS trend to build heights near the UK, and I expect today's ECM runs to move in that direction. The GFS op after D10 is again going with this improvement:

 

D11:    D16: 

 

The control is a variation on this theme. This is a consistent signal in the Long Range models that any Autumnal Atlantic weather would be short lived. Though GEM continues to throw out op runs that suggest a very wet UK, like today:

 

D10 GEM:   However last nights T300 mean suggests a very strong anomaly in line with the GFS HP: 

 

 D10 GEM mean:   So really the GEM op looks like it reflects a smaller cluster.

 

The GEFS are moving very slowly towards the hi res output but it still remains uncertain: 

 

NOAA 8-14 Day still heading towards the Atlantic trough and the E/SE UK  looking more settled (though low confidence):  

 

For the South tomorrows rainfall looks like the last main event for week 1, as the core of the low retreats NE: 

 

There is likely to be some local downpours from any showers in the coming week, but they will be hit and miss. The flip flopping re the potential developing LP for the weekend looks like it has been resolved and it is no longer on the main models (GFS, ECM & UKMO). Temp wise we are under a slack upper flow with the upper temps around or just below average so that may be reflected on the surface.

 

 

 

 

[bluearmy]

Looks as though the odds on us returning towards a nw/se split with Atlantic trough and euro ridge are shortening.

There is clearly some continuity issues run to run re upstream as nick has alluded.

Good to see the mean pv setting up shop nw of Siberia. The gem op NH profile day 10 a thing of promise for winter pattern matching!

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY TUESDAY OCTOBER 7TH 2014.

 

NEXT UPDATE WEDNESDAY OCTOBER 8TH 08:00

 

THE CURRENT GENERAL SITUATION. An unstable West or SW flow covers the UK with a deep Low approaching Western Britain tomorrow.

 

MODELS-2 WEEK HEADLINE  All areas look like being unsettled and windy with rain at times in cool conditions. Possibly becoming dry and quieter across the UK later.

 

THE JET STREAM ENSEMBLE FORECAST The Jet Stream currently lying across Northern France continues to be maintained to the South of the UK for the next 5-7 days. It then shows signs of disrupting somewhat and splitting with a Northern arm becoming the dominant part andheading to a position North of the UK in week 2 while a much weaker Southern arm lies across North Africa at the end of the run.

 

GFS The GFS operational today offers two distinctly different weeks of weather to come with week 1 dominated by a deep low moving slowly NE over Ireland over the next 48 hours to lie as a slow moving feature close to Northern Scotland and filling slowly by the coming weekend. Pressure then gently rises from the SE as a mild SW flow develops for a time with some more rain in the North and West. By midweek pressure has risen strongly everywhere with a large Autumn anticyclone lying over the UK later next week with fine days and mist and fog at night and morning for many. A SE flow then develops across the South to end the run but dry weather would probably prevail.

 

THE GFS ENSEMBLES. The GFS Ensembles are very supportive of it's operational this morning even in the further reaches of the run with a large UK based High pressure returning fine conditions for all by midway through Week 2 possiby with extensive overnight and morning mists and fogs in the very light winds.

 

UKMO UKMO this morning shows our deep Low currently moving NE over the coming days over Ireland and Scotland to lie as a slow moving and filling feature near Northern Scotland at the start of next week. Winds will fall light but the weak Westerly airflow will remain unstable and very supportive of further heavy showers or outbreaks of rain in places across the UK.

 

THE FAX CHARTS  The Fax Charts show Low pressure to the West and SW with a complex array of troughs gradually transferring NE over the coming 4-5 days with the main centre lying close to the far North at the weekend as a much weaker feature as pressure rises slowly from the South.

 

GEM The GEM operational today is dismissive of the GFS sequence of events as it goes the other way next week in suggesting a gradual return to deep UK based Low pressure with wind, rain and showers in abundance for all after a brief lull at the weekend.

 

NAVGEM NAVGEM does look a little more like GFS as it shows a gentle rise of pressure from the South next week as deep Low pressure slips deeper into the Atlantic and lies further Wet away from us pushing a milder SW flow up across the UK next week with rain probably more rstricted towards the North and West with time as higher pressure lies to the SE. 

 

ECM The ECM operational shows a more integrated push towards the UK of deep Atlantic Low pressure next week with a deep centre lying not far to the NW of Ireland by midweek next week with a strong SW flow carrying troughs NE across the UK with wind and rain for all in temperatures recovering somewhat from current levels.

 

NOTABLE TREND CHANGES FROM PREVIOUS RUNS GFS and to a lesser degree NAVGEM have turned more towards High pressure based weather pattern commencing next week but as yet this is not supported by the other output.

 

MY THOUGHTS  Some interesting switches in output this morning mostly from the American viewpoint as GFS has gone all out in switching from an unsettled and windy period next week to High pressure sat across the UK bringing fine and potentially foggy weather night and morning with quiet and bright days. It is well supported within it's own ensembles but less so from the other output. While the theory that leads to this happening is shown by other models too their thoughts gear towards the Atlantic being much stronger through week 2 than GFS shows with the net result that the milder and High pressure based surge shown is much more muted and while the South and East might benefit from less rain than elsewhere with warmer winds from the SW the North and West will probably see quite a bit of wind and rain as High pressure shown by most other European and the Canadian model output remains over the continental side of Europe. We must not discount the possibility of the output of GFS verifying especially since it has support from it's own ensemble pack but until this extends in a greater way to the other models it is subject to change over the coming runs and days. So my own thoughts this morning are to go with the majority this morning in saying that it looks like there will be more wind and rain next week following that of this week and although the emphasis of this will probably shift more towards the North and West if the GEM theory is right we will all be under attack from gales or in places severe gales and heavy rain later next week. However, I think that the ECM version this morning may be nearer the mark come the time.

[Polar Maritime]

The ECMWF is certainly showing a much stronger Atlantic driven pattern compared to the GFS into week 2.. With stronger Heights pushing up into America instead of the Atlantic as BA & Nick have alluded, Driving the Jet South and aiding to push Low Pressure across the UK. The good news is the PV isn't wanting to set-up camp over Greenland, And continues disrupted. Excellent Model watching with seeing the changes in the Northern Hemisphere at this time of year, And a stark difference to last.. 

 

 

Edited October 7, 2014 by Polar Maritime

[IDO]

Again this morning's GEM op has little support amongst it's ensembles. At D10 the op:  Mean: 

 

The ECM mean also hinting at the Atlantic trough with the jet running very close to the NW/W UK:  

 

The D10 mean from the GEFS 06z: 

 

So the means are singing from the same hymn sheet. The GFS 06z op is again HP dominated from D10 to D16: 

 

 

 

More ensemble members being dragged up by the op and control, though the hi-res still the most positive with  regard to a more robust high:

 

 

The GEM mean at D15 are split 50:50 as to whether the UK is under higher or lower pressure: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=1&mode=1&ech=360

 

October according to GFS may not be too bad if the trend continues...

[johnholmes]

I think the senior man at Exeter has had a 'funny turn'. I would love to be a fly on the wall at the Met O College as the instructor explains how come has has so many troughs on one chart over the UK, 5 I think it is. Looking at the IR satellite pass over the UK from Dundee Uni it would be a diffcult job to justify his Fax chart!

links

Fax

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

IR Sat picc

http://www.sat.dundee.ac.uk/abin/piccygridhtml/avhrr/2014/10/7/1250/ch5.jpg

 

I tell a lie there are SIX!

[Captain Shortwave]

The models continue to suggest an Atlantic trough/Euro high combo for week 2

After a brief cooler and wetter spell it could be the case that the theme of this Autumn will be restored with drier than average weather combined with above average temperatures. In fact from tomorrow temperatures will be back in the high teens in the south anyway.

The ops are backed up by the ensembles

Edited October 7, 2014 by Captain shortwave

[Paul]

Nick's latest synoptic analysis is online

 

http://www.netweather.tv/index.cgi?action=news;storyid=6206;sess=

[summer blizzard]

Bit of a stretch to call 1015mb settled. Does seem as though it won't be as bad as first appeared though.