Model Output Discussion 26/10 2012 >

[SMU]

Well not on this run, close no cigar, but a massive step west in the pattern, look for strong changes towards Scandi heights in the next 36 hours-

S

Edited November 3, 2012 by Steve Murr

[Weather-history]

+168 on ECM12Z is the beginning of an interesting set up to say the least!

Is it? Doesn't look particularly out of the ordinary.

[Gibby]

Good evening. Here is the Saturday evening look at the 12zs from GFS, UKMO and ECM.

All models support the Current Low pressure plus a secondary feature to the East of the main centre over Southern Britain tomorrow. Southern areas would likely see a period of rain under very chilly conditions with some wet snow possible on higher hills as it moves away East late tomorrow. Further North a more showery cyclonic airflow will persist but equally chilly. By Monday the Low pressures pull away East allowing a ridge of high pressure to collapse across Britain during Tuesday. So Monday will see the last of the cool and showery days for a while with the emphasis of showers shifting to Northern and Eastern coasts through the day. Tuesday sees drier conditions for all in a brisk NW flow.

GFS then shows a trough cross East on Thursday with a spell of rain for most. This is quickly followed by a depression to the NW taking hold of the UK weather with further rain spreading West to East over Friday and next weekend with the parent Low slipping SE over Britain. Temperatures after recovering somewhat would fall back again over next weekend. By Sunday things turn distinctly chilly as a Northerly flow develops as the Low slips away SE. there wuld be wintry sshowers for many Northern and Western areas with some more prolonged rain or sleet in the South. In FI tonight after a brief frosty ridge early in week 2 the weather would slide downhill once more as the pattern of before repeats itself with SE moving depressions continuing the cold incursions from the North several times over the period of FI with the risk of some snowfall in the North at times. there would still be a few brief milder interludes in the South ahead of the depressions.

The GFS Ensembles show a lot of changeable weather from the members of the ensemble pack tonight. There is quite a lot of wide variability in temperatures shown as spaghetti in the graph from day to day indicative of fronts passing through from the West and NW and it's this that keeps the mean for the run near to average. The chances are that all areas will continue to feel a chill at times over the next couple of weeks with these readings as well as rainfall occurring quite regularly.

Interestingly, both the operational and Control run take a trip below 0C towards the end of the run.

The Jet Stream shows the Southern arm currently blowing strongly West to East over France weakening and moving away South in the coming days. The Northern arm then takes control as it ridges North through the Atlantic and returns SE just to the West of Britain later next week.

UKMO for noon on Friday shows Low pressure South of Iceland with a series of troughs approaching the UK from the West with a SW flow bringing emporarily milder conditions with rain spreading across the UK from the West in the following hours.

ECM holds the Low pressure slightly further West at 144hrs hence a slower evolution in bringing the rain in from the West though it does show milder conditions too at that time point. Later in its run as this morning it prefers to keep a flatter flow holding Low pressure North of the UK with fronts crossing East in rather strong winds. Temperatures would be no better than normal generally and still rather chilly in the North behind the cold front that crosses East a week Monday. The run closes with a deep Low east of Iceland and a West or WSW flow over the UK with troughs bringing spells of rain in near normal temperatures.

In Summary the weather pattern for the next two weeks is quite up in the air at the moment. GFS prefers to keep heights fairly high over Greenland with several incursions of cold Northerly air occurs behind the passage of SE moving depressions. ECM keeps pressure higher to the South and East as well as over the Med which holds Low pressure North of the UK with pressure having fallen over Greenland. The net result is a changeable weather pattern when we will all see some rain. the question is will we have cold rain and hill snow as per GFS or normal Autumnal type rain in milder Westerly winds. The jury is out..

Edited November 3, 2012 by Gibby

[SnowBorder]

Personally, I think this run illustrates that the building blocks are in place for a potential cold spelI; i feel it's going to be a fascinating time to watch the model runs during November / early / mid winter as the tell tale signs are clearly in favour for a wintry set up. Almost reminiscent of 2010, although not quite as clear / severe. Certainly a completely different set up to this time last year. Time will tell. Tick tock!!

[Snow and storms]

weather warnings for rain on sunday starting early hours by Met office up to 40mm locally. Looks like it will be a bit of now casting because it is down to a secondary low spawning from the main one

that has been hanging around near Ireland for last couple of days. http://www.metoffice.gov.uk/public/weather/warnings/

60mph gusts forecast by 9am alogn the coast, I don't take much notice of these lately as Met office has been really poor on wind gusts recently.

Could be an interesting one to watch, as this secondary low was forecast to be a beast a few days ago . Worth keeping an eye on.

[Fujita Pearson Scale]

Good evening Snow & Storms,

I'm watching this one closely, certainly has the potential to cause some flooding and wind damage across the SE & EA.

Wonder if the GFS 18z will upgrade/deepen this little low spawning off the main Polar Vortex.......

FPS

[Gael_Force]

The NMM have deepened it a bit on the noon run - nasty little feature.

[SMU]

Evening All-

We are entering a period of high model uncertainty & large scale corrections westwards in the outputs-

This is a typical signal when the models are trying to resolve a block to the east. In These situations I dont really have a strong preference to one particular model, however the GFS is generally always to far east & the 18z & 06z are almost worthless - with these runs always moving to an overunning pattern post 180- with no undercut.

Heres a typical example of the GFS moving all jet energy into the northern flank & forcing the whole pattern to overun any blocking to the east-

http://modeles.meteo...nh-0-216.png?18

http://modeles.meteo...nh-0-228.png?18

http://modeles.meteo...nh-0-240.png?18

http://modeles.meteo...nh-0-252.png?18

http://modeles.meteo...nh-0-264.png?18

http://modeles.meteo...nh-0-276.png?18

http://modeles.meteo...nh-0-288.png?18

Note the GFS is sweeping that blocking away by having the energy piled up on the NW flank.

As we go through the runs over the next 48 / 72 hours expect some wild swings in FI from the GFS, but after this period the models should have a grip on what pressure build there will be over Scandi.-

The touted Northerly may develop or it may be forced back West as the low pressure gets split & energy heads down to the canaries...!!!

I guess the bit that needs to be highlighted is its still november & the continent wont be mega cold- we are at that tipping point where a gentle continental flow wont be very cold or mild, so will just feel slightly cooler than seasonal- all the while the CET ticking along generally below average.

I think we have all been spoilt by some recent synoptics & events happening in some recent years in the early part of the season-

Its the 3rd of November & expectations shouldnt be to high at this stage- Winter still isnt going to switch on all of a sudden, its a slow burner for the next 10- 20 days.

I for one am very satisfied that the mean zonal wind is being broken down to a negative anomaly, & the storm track is highly amplified.

as result of that the departure from the Norm is sitting around 1-2c, as a result pro rata come december we should be forecasting a CET of around 2.5-3c...

Exciting times, just patience required- the PV isnt suddenly going to explode into life- there is a lot feedback in the troposphere this season that seems to be propergating upwards - acting as some form of compensator against the ever cooling stratosphere.-

Anyway-

Expect further changes west over night- all for the good.-

S

Edited November 3, 2012 by Steve Murr

[Snowman.]

Evening All-

We are entering a period of high model uncertainty & large scale corrections westwards in the outputs-

This is a typical signal when the models are trying to resolve a block to the east. In These situations I dont really have a strong preference to one particular model, however the GFS is generally always to far east & the 18z & 06z are almost worthless - with these runs always moving to an overunning pattern post 180- with no undercut.

Heres a typical example of the GFS moving all jet energy into the northern flank & forcing the whole pattern to overun any blocking to the east-

http://modeles.meteo...nh-0-216.png?18

http://modeles.meteo...nh-0-228.png?18

http://modeles.meteo...nh-0-240.png?18

http://modeles.meteo...nh-0-252.png?18

http://modeles.meteo...nh-0-264.png?18

http://modeles.meteo...nh-0-276.png?18

http://modeles.meteo...nh-0-288.png?18

Note the GFS is sweeping that blocking away by having the energy piled up on the NW flank.

As we go through the runs over the next 48 / 72 hours expect some wild swings in FI from the GFS, but after this period the models should have a grip on what pressure build there will be over Scandi.-

The touted Northerly may develop or it may be forced back West as the low pressure gets split & energy heads down to the canaries...!!!

I guess the bit that needs to be highlighted is its still november & the continent wont be mega cold- we are at that tipping point where a gentle continental flow wont be very cold or mild, so will just feel slightly cooler than seasonal- all the while the CET ticking along generally below average.

I think we have all been spoilt by some recent synoptics & events happening in some recent years in the early part of the season-

Its the 3rd of November & expectations shouldnt be to high at this stage- Winter still isnt going to switch on all of a sudden, its a slow burner for the next 10- 20 days.

I for one am very satisfied that the mean zonal wind is being broken down to a negative anomaly, & the storm track is highly amplified.

as result of that the departure from the Norm is sitting around 1-2c, as a result pro rata come december we should be forecasting a CET of around 2.5-3c...

Exciting times, just patience required- the PV isnt suddenly going to explode into life- there is a lot feedback in the troposphere this season that seems to be propergating upwards - acting as some form of compensator against the ever cooling stratosphere.-

Anyway-

Expect further changes west over night- all for the good.-

S

I know this is a long way off but the 18z GFS has the PV pushed east over Canada allowing heights to rise over Greenland yet again.

So far off in weather terms but still hope is hope. Looking at the NAO forecast the Atlantic is still pretty much dead might rise to positive before going into the the negatives. Shame that I cant say that about the AO any reason why this is?

[bluearmy]

the gefs are pretty amplified (still) at day 14. There are various camps re where the ridges/troughs will be but apart from the kamkathka/Aleutian region, there seems to be a trend towards Greenland and/or ne scandi. Steve's post yesterday evening has fair representation in the morning op runs and I suspect the gefs are struggling even more with this retrogressive signal. What remains signficant is that the pattern is still amplified at day 14 with little appetite to expand the p/v to any large or organised extent.

[Gibby]

Good morning. Here is the morning look at the 00zs from GFS, UKMO and ECM for today Sunday November 4th 2012.

All models show a complex Low pressure system covering Southern Britain moving away East over the next 48 hours. All of Britain will see cold or rather cold conditions through today and tomorrow with heavy showers and some longer spells of rain today in the SE. Some snow could fall on higher ground in the North and for a while today on the South. By Tuesday a weak ridge will cut off the cold supply giving a drier and brighter day after the chance of frost on Monday. By midweek a West or NW flow takes hold bringing milder temperatures, a lot of cloud and some rain, principally for the North on Wednesday but elsewhere too on Thursday as a trough crosses from the West. By Friday another brief ridge crosses East with a drier spell in tow before deepening Low pressure out to the NW strengthens a SW wind and brings Atlantic fronts towards the North and West later in the day.

GFS disrupts the trough next Friday and the weekend sending it's strength SE so that the weekend the UK is covered in a North-South elongated Low pressure system with cloud and rain never far away from any one place. Temperatures would fall back somewhat from their late weekday levels with a little snow returning to Northern hills for a time. As we move into and through FI the trend is for a couple of dry and perhaps frosty days before renewed Low pressure from the NW brings a return to wind, rain and showers. This time though the Low looks like staying out to the NW sending troughs across Britain followed by showery Westerly winds. Temperatures would be nearer to normal with any snowfall reserved to the highest Scottish mountains in the showery airflows.

The GFS Ensembles show a very unsettled spell of weather through the next few weeks. A zonal pattern looks to be a favoured option as rainfall is spread about over the period of the run with uppers trending if anything rather above normal indicating temperatures between 8-12C at the surface by day. The operational on average was on the cool side of the pack later.

The Jet Stream shows the Southern arm weakening and subsiding over the coming days with the Northern arm ridging through the Atlantic and turning SE close to Western Britain later this coming week.

UKMO for midnight on Friday shows a deep Low pressure South of Iceland with a SSW flow over Britain ahead of a trough advancing in from the West. Eastern areas will probably dry at this point but the West would see rain moving in on a strengthening breeze. Relatively mild.

ECM shows a similar pattern with the pattern maintained through the latter stages of its run with low pressure near the UK or just to the NW with troughs swinging East in the SW flow carrying rain and strong winds at times to all areas in near normal temperatures.

In Summary the weather over the next two weeks is going to remain very changeable with rain or showers at times. With winds mostly cyclonic or from A Westerly point it will never be particualrly cold with just brief flirtations perhaps to rather colder conditions with showers mixed with more traditional late Autumn Atlantic unsettledness of wind and rain.

[tinybill]

morning all just looked into fantasy world looking good for cold lovers if it comes off !!!

http://www.meteociel.fr/modeles/gefs_cartes.php?code=16&ech=192&carte=&mode=0

Edited November 4, 2012 by tinybill

[Radiating Dendrite]

Charts tiny bill?????????????????????????????????

[IDO]

In the reliable GFS 0z has trough, ridge and trough for the next ten days. Average temps, bit of wind and rain with some more settled interludes (more so for the south).

I was expecting the latter stages of FI to flatten out with a more HP centric output but the GEFS Control and Op run are outliers, members tending to maintain the ridging, where as the main runs have another extended trough:

http://cdn.nwstatic....prmslLondon.png

However the scatter from members, from T120:

http://cdn.nwstatic..../t850London.png

Suggests smaller details yet to be defined, yet confidence high in the next ten days for a continuation of this unsettled Autumn spell.

The PV remains ragged at the end of FI, though less so than through the run:

http://cdn.nwstatic....384/npsh500.png

Even the Op run's FI, though looking promising, is on the wrong PV axis to get any of the 850hPa's cold uppers:

http://cdn.nwstatic..../h850t850eu.png

Obviously in Jan/Feb different story, but currently sustained cold/wintry weather not showing consistently on the GFS runs, despite the obvious potential. ECMWF, also pattern wise, very similar to GFS next 10 days.

Interesting current weather in SW:

fergieweather

Wow! "@MrGSchuster: @fergieweather Coleford, Somerset. #snowday http://t.co/1uLXx4W9"

04/11/2012 08:20

Edited November 4, 2012 by i'm dreaming of...

[bluearmy]

the 00z ens tell their own story. ECM at day 10 seems keenish on the ridging ne of scandi whilst naefs is not and by day 16 its greeny ridge and scandi trough.

Edited November 4, 2012 by bluearmy

[sebastiaan1973]

Please take a look at the individual members at 168h. 6 Clusters. http://www.ecmwf.int/samples/d/getchart/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2012110400!!chart.pdf

[bluearmy]

Please take a look at the individual members at 168h. 6 Clusters. http://www.ecmwf.int/samples/d/getchart/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2012110400!!chart.pdf

Clear from those why the day 10 ECM ens mean develops the scandi blocking. That link reminds me that nick s has sunk back into his non winter malaise again after briefly sticking his head above the parapet.

[Frosty.]

The latest models (ens mean) show an improving picture in the week ahead with pressure rising slowly and temps also rising back to average and even trending towards mild in the south and southeast later in the week so a drier and milder trend for the southern half of the uk in the next 5 days. Further north, for Scotland and N.Ireland it looks like remaining generally unsettled although temps also rising to around average, by next weekend it looks like all areas will be unsettled, cooler and cyclonic again with widespread showers and chilly nights. The further outlook shows the polar front jet remaining to the south of the BI with the uk in a mainly W'ly flow, sometimes just south of west and occasionally north of west, the airmass of polar origins so showers would be wintry on hills and overnight frosts would be expected, there are signs on the gfs 00z ens mean for pressure to rise generally towards the south and east with a more benign pattern after mid month but with overnight fog and slight frosts but pleasant sunshine where the fog clears, but northern and western britain possibly continuing more unsettled with low pressure to the north and west persisting.

[phil nw.]

Yes at T168hrs the outputs have a go at ridging towards Scandi. but the forcing from the west overcomes it.There were some members on yesterday`s 12Z on both models going for that.

Naef`s and ECM mean at day 10 more or less keep s the trough over us with those heights further east and out in the nw atlantic

http://www.meteociel...&map=1&runpara=

http://www.meteociel.fr/modeles/ecmwf.php?ech=240&mode=1&map=1&type=1

I can`t see any real evidence for a change to the current pattern for the next 10 days or so.

Edited November 4, 2012 by phil n.warks.

[BLAST FROM THE PAST]

If I could cherry pick a run it would be the 06z. Massive block to the east, trough backed west, v mild southerly flow in about 2 weeks time but the pattern not flat. Generally though yesterdays overnights that brought a quite flat pattern seem isolated, however, we are talking 2 weeks ahead here and so so much can happen by then.

Even though the flow is mild, the actual pattern screams of potential and IMO is a beauty. That trough to our west will make no inroads East and I would see a SE and E wind developing from there further down the line. This remember is just conjecture and is to show potential

a] for my 'mild' flip

b] for potential cold set up to be in place instead

Much rather have a mild flow like that than one with 1000s of miles of SW'Lies.

BFTP

Edited November 4, 2012 by BLAST FROM THE PAST

[Methuselah]

This what you mean, Fred?

http://nwstatic.co.uk/viewimage.pbx?type=gfs;date=20121104;time=06;ext=384;file=h850t850eu;sess=396a9c647294b9940d399b877ab22038;

Has potential...

[cold snap]

If I could cherry pick a run it would be the 06z. Massive block to the east, trough backed west, v mild southerly flow in about 2 weeks time but the pattern not flat. Generally though yesterdays overnights that brought a quite flat pattern seem isolated, however, we are talking 2 weeks ahead here and so so much can happen by then.

BFTP

yes and in ties in with the ecm at day 10 ,think next steps now are to look east,impresive scandi high.cold making inroads into europe in the later frames of the 6z for sure.slighly more incouraging output this morning.

[BLAST FROM THE PAST]

This what you mean, Fred?

http://nwstatic.co.u...399b877ab22038;

Has potential...

Thats the one....just added to my post

BFTP

[lorenzo]

Interesting to see the Russian High on the charts, will ensure complete chaos continues in the modelling. That feature really does mix things up.

A reminder of last winter where we had an absolute beast of a high over there and everything that went it's way either hit a brick wall or bounced back at us. Wonder if the snowcover effects are pulling through on the models now?

Here's a reminder of it's capabilities from the Easterly week in February earlier this year..

[SMU]

Morning All-

Model birth of a continental push.............

The pendulum swing towards pressure to the east developing is now well on its way- perhaps peter snow should present the GFS!

We are not quite there yet I feel with more movement to come-

he we see 4 days of the 12z GFS-

Nov 1 @ 228HR -High pressure wave flattened by the jet ( where have we heard that before ), no real profound blocking all the way to the east

http://modeles.meteo...12-0-228.png?12

Nov 2 @ 204HR- still no real blocking to our direct east, travel far enough though out to around romania etc & that small high of 1030 MB is there-

http://modeles.meteo...12-0-204.png?12

Nov 3 @ 180HR- Now we have a 1025 MB high further NW - still centred SE of finland, but nosing west & backing the pattern up over the UK

http://modeles.meteo...12-0-180.png?12

Nov 4 @ 162 ( << todays 06z- todays 12z for 156 is the one to add later) Centre of the high over southern finland & heigher heights extending west

http://modeles.meteo...snh-0-162.png?6

If we take the GFS from the same 06z run at 144-

http://modeles.meteo...snh-0-144.png?6

& Compare it with the UKMO ( EXCELLENT RUN- VERY COLD EUROPE DEVLOPING AT THE SURFACE)

http://www.meteociel...44-21.GIF?04-06

You will see the UK met office precludes strong Southerlies over the UK at ~ 150 HR with a developing Scandi highj pressure towards 168-

I expect that evolution of allignment over scandi to further develop over todays 12z Suites-

With instead of the UK seeing warm Southerlies I think they will be squeezed to chilly SE winds.

Maybe not a lot of undercutting to start, but as pressure builds in the mid term then day 8-15 become interesting...

NOTE the ECM control run at 2.5c MAX for de bilt-

http://www.knmi.nl/e...agse/index.html

It is my opinion that the stratospheric cooling is manifesting into the AO signature a little - which is forcing the polar element of AO index to return to a more normalised index, however this isnt propergating down to the mid lattitudes- especially 50/60N - where the wavelengths are still good & condusive to blocking patterns..

As mentioned last night, the 'general' theme of below normal departures continues & will do 'overall' for probably 80% of Novemeber- so the CET forecast topline of expectation should be

~ -0.5c below the norm-

The bottom line very much depends on the next 10-15 days in terms of how much retrogression we get out of the east- fun to watch & nothing from the SW zone expected any time soon-

great to see the snow in the SW this morning....

s

Edited November 4, 2012 by Steve Murr