Model Output Discussion 12z 18/10/2012

[snow drift]

Lol, by its nature, a discussion forum is pretty organic, if people are discussing the models a lot its going to be because they want to based on what the models are showing, that's all!

Its also fair to say that as a discussion there always will be opposing viewpoints and differing interpretations of things..

Agreed and some great posts, if you look at what people are explaining, a lot can be learnt. Two different ideas from steve and phil. Both plausible, both well explained and much to be gained from reading and studying the posts.

Anyway moving on, the latest ECM run you can see the cold air flooding from the north East. T168 shows this beautifully. It also shows the block. Will it turn out like this? Not sure as much time between then and now but interesting times ahead I feel.

[Liam J]

Northerly still there on the 00z ECM - The air being mixed out so the really cold uppers (sub -6c or lower) never quite make it to the UK apart from Scotland - Good news for the ski resorts looking at the current charts, although the finer detail can be pieced together nearer the time, i.e the potency etc.

Still settled & pleasantly mild to start next week - something to look forward to perhaps before we slide back down to average/cooler temps.

Edited October 19, 2012 by Liam J

[Methuselah]

A definite chance of a cold shot on or around the 27th (see appropriate 12Z chart, as i cannot copy it here)...

[TonyH]

Well -5c uppers to the south for a few days.

[Gibby]

Good morning. Here's my look at the 00zs from GFS, UKMO and ECM.

All models are quite close together on events for the next 4-5 days with just small but subtle differences between them. In general the pattern is for a slack South or SE airflow over the UK now that the Low pressure of recent days has filled up. A trough lies stubbornly close to SE England bringing outbreaks of rain to the SE today. Elsewhere there will be some brighter spells in relatively mild conditions. Tomorrow will see the trough move further away East so that most people enjoy a dry and bright day in sunny spells and just the odd shower. Sunday too looks less wet in the south than previously thought as the Low moving North from Europe is delayed and weaker. This though means Monday will now be rather cloudy and misty with patchy rain in places while Tuesday becomes dry, rather mild with a few showers in the SW in the still basic slack South or SE flow.

GFS then shows a strengthening wind backing towards the East as High pressure over Greenland ridges strongly SE over Britain. A cold Arctic flow is moving South over the Northern North Sea and Scandinavia. The effect of this will be to lower UK temperatures away steadily through the middle and end days of next week By the weekend much of the UK will be on the cold side of normal with frosts developing overnight and some wintry showers developing in Northern and Eastern areas of Scotland and NE England by Saturday and extending to other Eastern areas by Monday as Low pressure moves South down the North Sea. Towards the end of FI a High pressure ridge crosses East cutting off the Northerly feed but delivering some really hard frosts and fog patches overnight. Late in FI a push of Atlantic Low pressure moves in with a spell of upland snow for Northern areas before it turns to rain. Unsettled and rainy conditions develop then to conclude the run.

The GFS Ensembles show support growing for a cold surge from the North in a week or so time. Thereafter any recovery looks tentative with some members keeping rather cold conditions until the end of the run though Northern locations do show the long term mean 850's being surpassed by the end of the run. Rainfall amounts are small now until the end of the run probably indicative of colder high pressure hanging on over the South.

The Jet Stream continues to begin the process of breaking up and becoming ill defined over the coming 4-5 days. In a week or so time the flow splits into two with a Northern arm running East well to the North while a weaker Southern arm flows to the South of the UK, over Spain.

UKMO for midnight on Thursday shows High pressure over Eastern Greenland and Low pressure over Northern Scandinavia and to the SW of Britain. A cold Arctic surge is shown moving South over the Norwegian Sea. A High pressure ridge from the Greenland High covers the UK in steadily cooling conditions and mostly dry weather.

ECM shows a similar theme with a cooling weather pattern over the latter stages of next week. High pressure slides SE towards SW Britain keeping the coldest air away to the East. Nevertheless, the weather would be rather chillier than normal and a few showers in the NE could be of a wintry flavour over the hills. Frost could be likely at night but fog will probably be less likely as winds look too brisk. The day 10 chart shows the chance of a renewed surge in the days that follow after a trough crosses SE from Scotland.

In Summary there is now a definite signal of an attack from the North in a week or so. What form it will take is open for debate and the favoured option in my opinion would be an ECM type solution when High pressure slides SE over Britain delivering cold weather with frost and fog. If the High pressure ridge's axis is more to the West of Britain though some places could see an early taste of winter if the Northerly takes hold proper. It's going to be interesting model watching over the coming days as various options between the models are shown. The winter rollercoaster begins.

[Alex]

I wonder what the verification stats are for the Met model because maybe it's me but I think it's done a poor job this year with trends etc, one major error was the August southeast heatwave!

Moving onto the models and I think the ECM has got into a bit of a mess on the 00z it strengthens heights over Greenland then the high starts slipping southeast again?

[Radiating Dendrite]

The interesting thing for me is not the cold shot, but more the fact that it looks like we start November with a very weak polar vortex!

[Frosty.]

The Gfs 00z ens mean is slowly trending in the right direction as far as a possible Northerly is concerned, the high to the north over iceland does begin to pull further west towards greenland with a deep trough heading south into norway, we do eventually get a northerly component but high pressure soon regains full control, eventually slipping into a euro high position for a while before slowly drifting away southeast with unsettled weather from the atlantic towards the end of FI. so there is general model agreement that next week will be mild or very mild with light winds and with overnight fog but pleasant sunshine once the fog clears, then towards the end of next week it may start to turn colder from the north as the main high drifts west. The gfs 00z op run eventually brings an arctic surge southwards but it's getting pushed further back, the reliable timeframe is becoming very mild and anticyclonic.

Edited October 19, 2012 by Frosty039

[BLAST FROM THE PAST]

ECM, GFS and UKMO.......amazing what 24hrs can do. These runs will do nicely with GHP and trough over Scandi the consensus with some pretty chilly weather to come......right on cue

BFTP

[AWD]

ECM, GFS and UKMO.......amazing what 24hrs can do. These runs will do nicely with GHP and trough over Scandi the consensus with some pretty chilly weather to come......right on cue

BFTP

Find some way of cementing the pattern in for the next 4 months and all will be happy.

There looks like being quite a rapid switch around of temperatures over the continent within the next week or so. Very warm air gets pulled up from Africa in association with the trough to the SW bringing widespread warm temperatures over mainland Europe before the HP heads to Greenland bringing very cold temps to mainland Europe.

This time of year is known for these dramatic temperature gradients as the residual summer warmth hangs on in Southern Europe the same time as the cold airbase increase to the north if Europe.

Interesting to note is how vast and widespread the cold air rapidly becomes over Europe though, with early season snowfall now likely over much of northern & Eastern Europe.

Edited October 19, 2012 by AWD

[Gavin Hannah]

Love my gut feelings haha!

[legritter]

Another interesting day coming up .atleast in the outlook there are signs of some cold getting bottled up in upper latitudes . im going to leave it untill later modell runs before getting too excited ,but if that 528 Dam line does make it south of say Midlands by the end of next week or so, i think things on here will get mighty interesting ,and IF it hangs around with warm sea temperatures and still a little Kick in the sun ,it wont be ARCTIC meltdown but Net weather Meltdown . cheers

[Gavin Hannah]

Love my gut feelings haha!

[johnholmes]

Picking up on the summary from Gibby.

All 3 major synoptic models show a pretty similar pattern at T+144, that is high pressure NW of the UK and low pressure over northern Scandinavia. By 192 hours and the two models continue to be similar to one another. Both look as if the coldest air is going east of the UK. If you look at the current T+120 Fax chart then the low, shown about mid way between Svalbard and Iceland, the probable ‘trigger’ as some call it, is too far north to allow deep cold air into the UK as it moves east. For that to occur the low should be in the Iceland area tending to move ESE.

Still if the models are correct the temperature change through next week will be a talking point. With falls of about 10C over most areas of the country by Friday.

This pattern is receiving growing support from the 500mb anomaly charts. Yesterday it was 2 against 1 for this pattern. Now both ECMWF and GFS show this idea, see link below, whilst the NOAA version still favours a less dramatic idea, an upper ridge but with the trough much further east than the other two show.

I suspect this is a 2-3 day cold shot.

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

[knocker]

I wonder what the verification stats are for the Met model because maybe it's me but I think it's done a poor job this year with trends etc, one major error was the August southeast heatwave!

Have you not got the cart before the horse. Should you not of checked the verification stats before making the statement?

[UV-RAY]

Have you not got the cart before the horse. Should you not of checked the verification stats before making the statement?

He's asking a question and giving his opinion, is this no longer allowed on here?

[SMU]

UKMO is the coldest run this morning with the cold shot angled as best as can be towards the UK

http://www.meteociel.fr/ukmo/runs/2012101900/UN144-21.GIF?19-07

over the last month the UKMO has been pipped into first place by ECM

http://www.emc.ncep.noaa.gov/gmb/STATS/html/acz5.html

However its been out in front since 5 or so days-

interesting the gem is up there & it should now be considered as the big 4 not 3

S

[Nick F]

00z GFS operational was certainly at the colder end of its ens members for UK locations at the end of next week, though certainly has some support.

Though given the cold vortex that may deliver the cold blast to parts of the northern Europe next week moves across across nern Greenland, where there is much less data, before heading towards Norway, there is greater margin of error for modelling developments up here. So by no means certain yet where the vortex will end up and where the cold air goes.

In the shorter time frame, mesoscale differences between models for Sunday's weather - 00z UKMO GM and ECMWF have much of the UK dry and fine, but 00z GFS brought rain north across England and Wales. 06z GFS has now backed off with rain just for the SE corner.

Edited October 19, 2012 by Nick F

[SMU]

GFS06 Z coming more towards the UKMO pattern-

Now we are at 132 the overall chance of significant change is beginning to receed & now we are homing in on angle of attack etc-

http://modeles.meteociel.fr/modeles/gfs/runs/2012101906/gfsnh-0-132.png?6

any further west & Im sure someone will trawl out the Dec 62 charts....

S

[Frosty.]

UKMO is the coldest run this morning with the cold shot angled as best as can be towards the UK

http://www.meteociel...44-21.GIF?19-07

over the last month the UKMO has been pipped into first place by ECM

http://www.emc.ncep..../html/acz5.html

However its been out in front since 5 or so days-

interesting the gem is up there & it should now be considered as the big 4 not 3

S

if the ukmo keeps this up, the tv forecasters may start dropping subtle hints about the cold plunge but for now, all they are saying is very mild and settled next week with overnight fog.

[Liam J]

We could be looking at the first low level snowfalls of the season over the northern half of the UK in around a week, perhaps even down to sea level for a time for the far north of Scotland. I'm off work next week so I may just get myself up to the highlands for a few nights nothing set in stone as yet - So I'll hold off booking atm until the risk of an output change becomes less...

Edited October 19, 2012 by Liam J

[Nick F]

00z ECM ensemble mean vs deterministic charts for next Friday and next weekend. IMO remaining dry but after a very mild start to the week in the south turning colder from the north thus bringing the risk of overnight frosts end of week and over that weekend.:

MSLP Fri 26th -Sun 28th

T850 Fri 26th - Sun 28th

Edited October 19, 2012 by Nick F

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2012101906/gfsnh-0-240.png?6

Last one from me on the wild 06z- Obviously with the usual disclaimers-

The above chart is a record breaking one- Its EXTREME, not maybe for surface temp over the UK, but for the extreme index of the teleconnections that we monitor daily-

You have a classic 4 wave pattern with the 2 major waves stationary over the East pacific & greenland-

As a result you have a record breaking

+ PNA pattern, -NAO Pattern & -AO pattern- ( estimates of the AO ~ -5 NAO ~ -3/-4)

You dont get charts or the 'chance' of these extremes very often, however since 2008 we have been shattering extreme index records each winter...

As each day passes & we shuffle towards winter as long as the strat plays ball then my optimism of a winter up there in the echelons of 62/63 78/79 takes an uptick like one of those old blue peter totalisers......

S

[Iceaxecrampon]

http://modeles.meteo...snh-0-240.png?6

Last one from me on the wild 06z- Obviously with the usual disclaimers-

The above chart is a record breaking one- Its EXTREME, not maybe for surface temp over the UK, but for the extreme index of the teleconnections that we monitor daily-

You have a classic 4 wave pattern with the 2 major waves stationary over the East pacific & greenland-

As a result you have a record breaking

+ PNA pattern, -NAO Pattern & -AO pattern- ( estimates of the AO ~ -5 NAO ~ -3/-4)

You dont get charts or the 'chance' of these extremes very often, however since 2008 we have been shattering extreme index records each winter...

As each day passes & we shuffle towards winter as long as the strat plays ball then my optimism of a winter up there in the echelons of 62/63 78/79 takes an uptick like one of those old blue peter totalisers......

S

Big words Steve and courage for sticking the neck out even at minus 10 days off. Looks like an early dusting for the tops of the NW fells - earliest I can recall.

All looks shortlived as the HP pushes in all too easy but hopefully a start of winter to remember.

Ian

[SMU]

Cheers

I would say that the longivity of the cold may not be as straight forward as you thing- 1/2 days - hum im not so sure- probably longer 5-10

S