Model Output Discussion: 12Z (02/12/12) And On...

[Skeggy Winter Storm]

A much better 6z from the gfs relative to the 00z beyond T+240..there is still a dodgy period with the high just to the northwest of the uk but unlike the 00z, there is a pivotal moment and we have a stronger pulse of cold cyclonic energy from the east/northeast which pushes the high further west and then northwest towards iceland/greenland and we are into a very cold ENEly unstable flow with snow showers galore pushing in from the north sea with temps struggling to rise above freezing and persistent frosts. For this week, the pattern remains broadly the same as the 00z with lows diving southeast across the uk and with cold arctic air digging south in their wake with wintry showers of hail, sleet and snow together with widespread frosts but also some less cold intervals with rain rather than wintry ppn. Today however is the mildest day of this week and indeed probably the next few weeks with 9-11c in the south and southwest but colder again by tomorrow at 6 to 8c, colder air pushing south through tomorrow with wintry showers into the far north and spreading south, into wednesday, snow showers for the north and east, especially coastal areas, fine and frosty elsewhere, the frost probably not really lifting and a very frosty night on wed night, thursday slowly turning a bit less cold as another low pushes southeast with rain, sleet and hill snow, then friday looks a degree or so colder with a strong n'ly and rain clearing south followed by wintry showers, the weekend starts that bit less cold again with low pressure over the uk and with rain and showers, wintry on hills, turning colder through sunday as the low pushes further east allowing another surge of arctic air south with showers turning more to snow, next week very cold nely winds, perhaps more settled to the north and west but frosty with a few wintry showers to n/e coasts, more frequent wintry showers to eastern and southeast counties of england bordering the north sea, feeling bitter. There are signs of the atlantic trying to push in later in FI but that's a long way off and the block may ultimately keep milder air away.

Do you think il get wintery showers in my neck of the woods soon the models show some cold air at times here on lincs coast

[Glacier Point]

06z GEFS H5 mean anomaly for day 10 showing us a realy strong -NAO signature.

The really striking thing for me is the lowering of heights across both the Pacific and the Atlantic in the middle latitudes, as well as low heights across much of Asia. That is a classic sign of an El Nino type atmospheric base state and should maintain us in a predominately GWO phase 5-6-7-8 type pattern, which focusses the main core of +ve height anomalies over the Northern Atlantic and southern Greenland.

The next challenge for NWP is what happens to the severed part of the PV over NE Siberia / far NW Pacific (could well help to sustain low heights in the Pacific) and how the pv migrates from Canada back to Siberia in the extended range.

That tees us up perfectly for late December, switching the focus from Greenland / Iceland towards Scandinavia for blocking as we really see a strong Siberian High develop in the coming weeks.

It's getting really hard now to make the case for anything approaching average in the longer range and we need to see massive structural changes now for us to avoid what is coming in January. The ECM seasonal already looks bust, and forecasts predicated on a January thaw type scenario should be aware of the more El Nino type tendency in the atmosphere right now, these being more often than not being associated with colder than average Januarys (remember 2009/10).

Edited December 3, 2012 by Glacier Point

[Frosty.]

Do you think il get wintery showers in my neck of the woods soon the models show some cold air at times here on lincs coast

Yes I think wednesday is looking good for snow showers and max temps of only 2 or 3c.

[EML Network]

I keep seeing the phrase "NWP" mentioned , can someone tell me what it refers to ?

[Suburban Streamer]

I keep seeing the phrase "NWP" mentioned , can someone tell me what it refers to ?

the models. Numerical Weather Prediction

[swfc]

06z GEFS H5 mean anomaly for day 10 showing us a realy strong -NAO signature.

The really striking thing for me is the lowering of heights across both the Pacific and the Atlantic in the middle latitudes, as well as low heights across much of Asia. That is a classic sign of an El Nino type atmospheric base state and should maintain us in a predominately GWO phase 5-6-7-8 type pattern, which focusses the main core of +ve height anomalies over the Northern Atlantic and southern Greenland.

The next challenge for NWP is what happens to the severed part of the PV over NE Siberia / far NW Pacific (could well help to sustain low heights in the Pacific) and how the pv migrates from Canada back to Siberia in the extended range.

That tees us up perfectly for late December, switching the focus from Greenland / Iceland towards Scandinavia for blocking as we really see a strong Siberian High develop in the coming weeks.

It's getting really hard now to make the case for anything approaching average in the longer range and we need to see massive structural changes now for us to avoid what is coming in January. The ECM seasonal already looks bust, and forecasts predicated on a January thaw type scenario should be aware of the more El Nino type tendency in the atmosphere right now, these being more often than not being associated with colder than average Januarys (remember 2009/10).

hi GP.Just a quick one.What do you mean by structural changes?sorry for my ignorance lol

[bluearmy]

too early to go down that road but, looking at the meto 30 dayer and extended ens output also made me think re the ecm seasonal. does anyone know when it last made a half decent job of a winter forecast?

[Glacier Point]

Basically across the NH, we would need to see a more Nina type signal arising. That would be a net removal of westerly winds across 20-30N in the first instance (currently we are adding large westerly wind totals here), and a general signal for the polar vortex to stabilise and organise itself around the North Pole (currently in tatters and nowhere near the Pole).

We would also need to see the MJO and general tropical activity work its way to phase 3-4 in the far western Pacific and Indian Ocean. Currently anything but, tendinging to be more scattered across the equator which is often associated with a -NAO pattern.

[lorenzo]

Great update GP, Thanks, Yes the ECM seasonal is definitely a bust

Heading out so cannot post up the few charts I have saved, but this is one to savour at only 216 hrs from the GFS op run, interesting to see things at this angle compared to hemispheric, really get a sense of the blocking up to our North. Strong anomaly as per the GEFS.

[Glacier Point]

too early to go down that road but, looking at the meto 30 dayer and extended ens output also made me think re the ecm seasonal. does anyone know when it last made a half decent job of a winter forecast?

I saw the ECM seasonal prediction for the AO Nick. It was gunning very positive AO throughout.

[london-snow]

GP if you do find a minuite would you mind breaking your post down to those less knowledgeable?

[Man With Beard]

Sorry on mobile so can't post link - but looking at GFS snow cover charts for Europe after T144, the whole of central and eastern Europe looks certain to be under snow cover - meaning any feed from the east next week will even more potent for cold than 850s might suggest, I would have thought?

[TEITS]

GP if you do find a minuite would you mind breaking your post down to those less knowledgeable?

Means our fuel bills will cost a fortune this year, Nick Sussex will move back to the UK, Steve M will be having kittens, Ian Brown will be in hiding. Also it will be cold.

[nick sussex]

Very difficult to say today which model has called the upstream pattern correctly.

After the ECM/UKMO one would have expected some movement from the GFS 06hrs run given the timeframes involved.

For the eastern USA todays model diagnostic discussion at NOAA preferred a blended solution of the ECM/UKMO upto 12hrs on Thursday.

So for the moment that probably looks like the slightly favoured solution, having looked at the ECM ensemble maps at 168hrs it is however the more riskier way forward and some of those members show why.

Of course if things go to plan theres no need to worry , the ECM looks very good later but later is the operative word here, neither the ECM/UKMO have jumped the first hurdle at 144hrs.

So we'll just have to wait and see this evening which route its going to be.

These are the ECM ensemble maps at 168hrs:

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2012120300!!/

Easy to pick out which ones would appear if the ECM and UKMO go wrong past 144hrs, I'm now going to go away and take a happy pill because I'm being far too pessimistic and of course things always go right with colder synoptics into the UK!!!

Edited December 3, 2012 by nick sussex

[carinthian]

Thursday/Friday's low needs keeping an eye on, it deepens as it passes NE Scotland and continues SE across the N Sea. 06z GFS showing 50-60 mph gusts across northern and central Britain and coupled with cold air wrapping into the circulation from the N and NE - could be some atrocious conditions over the hills of N and NE Britain.

Another deep low follows from the NW over the weekend and follows a similar track on Sunday bringing a risk of gales and blizzards over higher ground of the north.

Then behind the weekend's low, some differences over the amplification in the PFJ upstream over the Atlantic - 06z GFS has sufficient amplification still for a decent Atlantic ridge towards Iceland, the Euros, however, more progressive with that trough moving east from new Foundland - so we don't get the same height rise needed.

However, there is still the underlying signal for blocking to the N and NE, it's just what route do we take to get there. The easy route or the painful route?

Hi Nick,

We have just received our resort forecast for the next 10 days. They have sent us a storm warning about the one you mention. Here on Friday night / Saturday morning, blizzard conditions with wind chill on the mountain of -26C. Just in time for the start of the new season that weekend !

C

[SnowBallz]

What's coming in January?

Coincides with the next movement of the 60-day tropical wave cycle. Stewart touched on the effect of the timing of this, bearing relevance to whether January would be just below average, or well below average. The inference I'm inclined to take - mindful of the context - is that the timing would be conducive to the latter.

Or, he might just be talking about post-Christmas blues

[Bristawl Si]

What's coming in January?

1979 revisited...maybe.....hopefully!

Edited December 3, 2012 by Bristle boy

[Glacier Point]

Purely speculative at this stage. However, the inference being that the teleconnectors (AO and NAO) are being modelled at strongly negative values in the next 10-16 days. The timing of the next tropical wave (suggested in the winter forecast at mid Jan, maybe a week either side of that), should excite these already negative tendencies and drive us into a hemispheric deeply negative -AO/-NAO pattern [v. cold].

[kold weather]

Some great runs this morning. I never did believe the 2nd coming of the PV, instead whaty has happened is the models have slowly downgraded that features strength and this has allowed an ever increasing blocking signal in the Atlantic/Scandinavia to form.

The 06z GFS evolution looks reasonable enough, as does the 00z ECM. It may take a little while to really up the snow chances, but the short-medium term is going to be building that cold and cooling down the waters around us so we wipe out ant marginality down the line, as we saw in December 2010 having colder conditions around us helps big time.

I personally think, very cold 2-3rd week December, followed by relaxation/attack from SW for Xmas period, followed by another cold plunge early Jan...timing is similar IMO to 78-79 though.

Edited December 3, 2012 by kold weather

[Frosty.]

Very good news from the latest GEFS mean and the ECM 00z ens mean to reinforce what ian and gp have said this morning, a very cold blocked outlook appears to be highly likely by early next week, initially via a Northerly blast early next week which slowly blows itself out but we become entrenched in a very cold outlook with arctic and continental arctic influences, as it's the mean, something more severe could easily pop up during the period from the start of next week through to the run up to christmas, no realistic signal that the atlantic will break through in the next 2½ weeks +.

[swfc]

Coincides with the next movement of the 60-day tropical wave cycle. Stewart touched on the effect of the timing of this, bearing relevance to whether January would be just below average, or well below average. The inference I'm inclined to take - mindful of the context - is that the timing would be conducive to the latter.

Or, he might just be talking about post-Christmas blues

Be a good call that i think.im struggling to see past 96-120 hrs!!!

[Severe Siberian icy blast]

Means our fuel bills will cost a fortune this year, Nick Sussex will move back to the UK, Steve M will be having kittens, Ian Brown will be in hiding. Also it will be cold.

Haha that's class, well done !! And as for us collides , lots of sleepless nights , nagging wives , square eyes , lots of drink , and a trip to B&Q for a wooden sledge !!

[pipsta]

Hi guys, im not a regular poster on here and certainly not in the models thread so here goes with a quick question which im sure most of you can answer. Alot of you mention convection over the sea/rivers caused buy the cold uppers, will the saturation of the land be taken into consideration from the models from a PPN point of view? There alot of swollen rivers and flooded land at the moment surely this will enhance convection amounts as the cold uppers pass over our island. Do the models look for this?

[Buzzit]

Hi All

Just like to point out the slightly different treatment of events on the 5th December according to todays GFS and NAE

6z

[Jayces]

Purely speculative at this stage. However, the inference being that the teleconnectors (AO and NAO) are being modelled at strongly negative values in the next 10-16 days. The timing of the next tropical wave (suggested in the winter forecast at mid Jan, maybe a week either side of that), should excite these already negative tendencies and drive us into a hemispheric deeply negative -AO/-NAO pattern [v. cold].

Thanks GP, I understood all of that in bold but that is all I needed to know ;-)