Winter Model Discussion Thread 12Z onwards 5/1/13

[AWD]

http://www.wetterzentrale.de/pics/Rtavn2401.png

10 days away and firmly FI but consecutive GFS runs have built HP over the vicinity of the UK and lowered heights over Greenland, progressing to the deep purples shown above.

Doesn't last though;

Probably just a "reload phase" as the PV settles into a new home.

All FI and not worth much at all currently. By then, if we are taking the GFS at face value, a good portion of the country would have seen decent snowfall anyway.

So if the GFS is the worst output, then it sounds like we are being rather spoilt to me?

[-uksnow-]

GEFS mean continues the backtrack and splits the energy:

0z:

6z:

Looking more and more like this has been a GFS wobble, though we still can't take anything for granted for a few more days

SK

Presume you mean backtrack away from its wobble rather than away from the cold and towards the 'milder' side of the runs?

[UV-RAY]

I much prefer the ECM'S road to riches, the GFs although it brings cold air in looks a very messy affair with the potential for things to go the way of the pear. Still it makes exciting viewing on mild drab Sunday morning.

Edited January 6, 2013 by Sceptical Inquirer

[bobbydog]

http://www.wetterzen...s/Rtavn2401.png

10 days away and firmly FI but consecutive GFS runs have built HP over the vicinity of the UK and lowered heights over Greenland, progressing to the deep purples shown above.

but ian, that chart is at +240 aka FI. it leads to this at +348-

your theory is not really too worrying is it.....

Edited January 6, 2013 by bobbydog

[MR EXTREMES]

oh yeah gfs i could swear that lastnights and yesterday mornings model runs were all very different oh and todays.

ian the cold is on its way im not intrested in the pv because background signals dont support this.

and lets not listen to what the expert forecasters........

[snowking]

Presume you mean backtrack away from its wobble rather than away from the cold and towards the 'milder' side of the runs?

Yep in the hi-res section, that energy across the pole is now becoming increasingly split into the two distinct vortices (which was suggested up until 12z yesterday when it suddenly decided to join the two PV lobes), and so this is looking like a slow backtrack towards better longer term potential once again.

No guarantees it will stay that way, but better signs

SK

[Robbie Garrett]

GfS in November 2010 did the same exact thing! I'm not worried till we get 4 days from an event. That's generally when the MetOffice come on board with cold spells in the short term.

Apparently next weekend will be unsettled, odds on as the UKMO and the 13th the date I said 3 days ago to be the pattern change gets into the reliable timeframe I suspect an update to snow showers or complete snowfest...

Fog from high pressure over the UK is a precursor for cold weather along with it being routinely mild. Guess what it is in the South East? Foggy and slightly mild.

Another thing, what we are seeing is not a result of the stratosphere but other background signals. Correct me if I'm wrong but a SSW event takes 2-3 weeks to filter down...

Yes Ian....but from where?

There is no support from other modelling at this present time, not from the stratosphere above it, not from the projected MJO phasing, and not even (in terms of the 0z) from its own ensembles!

Completely understand that taking the models at face value its not impressive, but you have to ask where such a solution is coming from

SK

[snowking]

GfS in November 2010 did the same exact thing! I'm not worried till we get 4 days from an event. That's generally when the MetOffice come on board with cold spells in the short term.

Apparently next weekend will be unsettled, odds on as the UKMO and the 13th the date I said 3 days ago to be the pattern change gets into the reliable timeframe I suspect an update to snow showers or complete snowfest...

Fog from high pressure over the UK is a precursor for cold weather along with it being routinely mild. Guess what it is in the South East? Foggy and slightly mild.

Another thing, what we are seeing is not a result of the stratosphere but other background signals. Correct me if I'm wrong but a SSW event takes 2-3 weeks to filter down...

Hi Robbie

The effects from the stratosphere have no set lag time associated with them. It all depends on how quickly we see the effects downwell into the troposphere, and a whole array of factors help to determine this (zonal wind budget in the troposphere, QBO, EP Flux, Wave Activity etc.). An SSW can initiate an instant response in the troposphere, but equally sometimes it takes a few weeks before we see anything. In this instance it seems that we get some sort of instant response with a weakening and split of the Polar Vortex in the next 10 days or so

SK

[Blizzardof82]

Would I be right in saying the models are not factoring in the SSW at this point as it only starts today?

[ANYWEATHER]

Pieces of the jigsaw are now coming togeather, to early to say exactly how cold and how long it will last, the devil will be in the detail, and the eyes to dot and the teas to cross still, but a drastic temperature drop looks very likely later this week.

[AWD]

http://www.wetterzentrale.de/pics/Rtavn2401.png

10 days away and firmly FI but consecutive GFS runs have built HP over the vicinity of the UK and lowered heights over Greenland, progressing to the deep purples shown above.

Although on the flip side of the coin, there's a post in the Strat thread that would support this scenario somewhat, albeit less progressive;

So, conclusion. It's way in FI so who knows!

Plenty of interesting Wintery potential before this timeframe anyway.

Edited January 6, 2013 by AWD

[IDO]

True we will have all kind of charts in FI popping, its best not get too hung up on them until they are within the reliable timeframe then we can expect mild incursions and blocking break downs!

I think Ian is right with the synoptics, in that that piece of PV off W. Greenland is what maybe preventing the GFS in following the ECM to a quick GH:

GFS at T168: ECM: Weaker PV in Greenland on ECM.

That delays the blocking, and doesn't allow that initial easterly to take hold. On 06z run the energy from the PV pushes cold uppers from the NW, which holds back the NE'ly. This delays the inevitable retrogress west of the Scandi high, as shown on the 06z later in FI. Earlier runs (from GFS) had that PV piece influencing the UK situation well into FI, so at least it is a step in the right direction. Further erosion of that Greenland PV would draw GFS closer to the ECM solution.

GFS 0z

Edited January 6, 2013 by i'm dreaming of...

[MR EXTREMES]

i know its fi but alantic totally blocked low heights to our east heights to our west and north.

ecm same time frame yes fi but yummy.

i bet by t240hrs like the ecm and gem this would have the ingredents to futher blocked pattern and cold.

nogaps at t144 but i bet this to will show the right ingredents towards a spell of cold weather this is not a cold snap this is a cold spell.

and theres no reason to say the ukmo wont join the party the cold is coming across the board pv well im sure if these models show this then pv means nothing right now and with futher pv disruption u can bet a bottom dollar this is no cold snap.

the only reasons why i dont go deep into detail is because theres no point it will change even if its only small changes but this dont take away whats coming 3 days or more the models have been confident in showing blocked cold setup in one form or another.

[Methuselah]

and lets not listen to what the expert forecasters........

True. And don't be fooled by authoritative-sounding conjecture by folks who should know better...Because, outwith about 7 days' into the future, it's nearly all conjecture?

[IDO]

GFS short ensembles. Look at the scatter at D3/4 onwards:

Highlights the low confidence in the GFS model going forward. Thats what makes ECM output even more striking and why I am hesitant to back it, yet.

Edited January 6, 2013 by i'm dreaming of...

[fergieweather]

UKMO will continue, rightly, with cautious phraseology re potential outcomes of cold spell for now. Currently lean towards EC solution but as of 00z, MOGREPS not aboard (more mobile by d10 after retaining ridging). Next 2 days will be critical in terms of how public forecasts are tilted/emphasised thereafter.

[cooling climate]

I must admit not being to phased about the lack of heights to the north in the

6-10 day time frame from the GFS model.The ECM is closer at keeping with

what is happening higher up and does not make a meal out of transfering a

small piece of energy across the pole and therefore makes much more sense.

We could be on the cusb of a very long and protracted cold (very cold) wintry

spell for the UK and Europe.Two days ago I posted in the ramp and go nuts

thread that I believe we could very well see a negative CET temperature from

the middle of January to the middle of February which I believe is very possible.

Must admit l love the 36h plus snow storm that the 06z throws up in la la land

would definitely need a snow plough rather than a shovel for that one lol.

[bradymk]

UKMO will continue, rightly, with cautious phraseology re potential outcomes of cold spell for now. Currently lean towards EC solution but as of 00z, MOGREPS not aboard (more mobile by d10 after retaining ridging). Next 2 days will be critical in terms of how public forecasts are tilted/emphasised thereafter.

Yes still a lot of uncertainty although turning cooler looks quite certain now but how cool and for how long is as ever making it hard to forecast. Interesting about MOGREPS, is this the first run it has done that or has it not been on board at all regarding cold? Thanks Edited January 6, 2013 by bradythemole

[fergieweather]

Ps raw UKMO doesn't represent significantly modified version being used in 4-5 d publIc forecasts. Important to stress this.

[john mac]

I think we need to keep our feet on the ground. It's not nailed on yet and after December we would be foolish to take things at face value this far out. Remember what Ian ferguson said with regards to there being many changes in the models.

[snowking]

GFS short ensembles. Look at the scatter at D3/4 onwards:

Highlights the low confidence in the GFS model going forward. Thats what makes ECM output even more striking and why I am hesitant to back it, yet.

Or, of course, we could look at the very good agreement in the short range ensembles for a significant cool off of 850's

graphe_ens3.php

And 2m temps:

graphe_ens4.php

Two sides to every story.

And then at Reykjavik :

Fairly decent agreement (relative to usual SLP ensembles) for a rise in pressure into Iceland in the next 7 days

SK

[IDO]

The ECM op much closer to the ens mean than last night, so reasonable confidence:

Last night:

[Ian Brown]

UKMO will continue, rightly, with cautious phraseology re potential outcomes of cold spell for now. Currently lean towards EC solution but as of 00z, MOGREPS not aboard (more mobile by d10 after retaining ridging). Next 2 days will be critical in terms of how public forecasts are tilted/emphasised thereafter.

Thanks Ian, we can take it that the MOGREPS supports the way the GFS is handling the Greenland situation, and then bringing back the Atlantic by around day 10 ?

[Frosty.]

The Gfs 06z run shows the chaos being caused by the onset of sudden stratospheric warming, with a much colder spell developing towards the end of the week, then a relaxation in the cold before an even more potent blast from the east arrives, this is just the beginning, the models are in a state of chaos as they try to get to grips with a really epic pattern change to cold and very cold to help banish the memories of the rubbish we have endured in recent weeks. I think a freeze is on the way with severe frosts and snow. i would also like to mention the Ecm 00z, a very good trend for cold with easterlies and northerlies and high pressure retrogression to greenland, it's all looking very promising for coldies in my opinion.

[AWD]

Or, of course, we could look at the very good agreement in the short range ensembles for a significant cool off of 850's

graphe_ens3.php

And 2m temps:

graphe_ens4.php

SK

Much better ensemble suite. Majority of runs now inbetween -5c & -10c 850hpa temps for the high res part of the run.

2m temperatures looking decidedly cold too.