Winter Model Discussion 12Z 22/1/13 onwards.

[cooling climate]

Since Nick is an expert, it's hard to argue too much with his view on things but yes, there are signs of change already appearing as you and teits have said and they should continue to grow and grow in the next 7-10 days.

Except of course when you do not agree with what he is saying lol.Plenty of indicators as I said and have been

saying for several days at least now,not least the ongoing strat warming. As I posted in the strat thread

yesterday apart from the initial quick response to the SSW there is at least three weeks of strat warming

yet to work its way down through the layers to the troposphere and we look to be in a very favorable

location for where the blocking sets up.

Plus over 75% of the 06z ens show a much more amplified pattern building as we get towards the end of

the first week of Feb onwards. The 12z hopefully will show an even stronger trend and this will continue

as we go through the week.

[SMU]

I think some are raising the expectation to high at this early juncture- The models - especially the GFS is showing some 'tentative' cold signs way out in past 192-

However the biggest problem will be getting heights to retrograde all the way from the atlantic then circumnavigate greenland & towards Svalbard-

In the last 10 years we have perhaps seen that type of scenario 1 / maybe 2 times- late feb 2005 springs to mind.

High risk synoptics- big rewards if they come off, but varification very low in the modelling arena in the last decade..

the ECM 15 ENS mean has dropped slightly below average at the tail end & the control goes cold- reasons to be upbeat- but we need to be firmly realistic.....

S

Edited January 27, 2013 by Steve Murr

[nick sussex]

I wonder whether the UK can squeeze a snow event next weekend.

It could be rain turning to snow as that low clears into the continent, much depends on how much cold air can be tapped into from the ne.

Still disagreements as to the detail for the end of the week but certainly something to look out for in future outputs.

Edited January 27, 2013 by nick sussex

[Catacol]

OK - where are we now? Well for the first time in a few days or more we have a very interesting stand off between GFS and ECM in terms of NH modelling and particularly the energy within the vortex. ECM is stubbornly sticking to a Canadian vortex centre right out to day 10, with consequent strong atlantic energy and a flattening of any ridges that try to form. 192h here shows the deep cold under vortex energy over the E USA and Canada:

and by 240h the centre of energy is still very clearly in that Canadian sector. For certain the vortex has enjoyed Canadian wintering this season!

However GFS is taking a different route now. At 192 similar to ECM in terms of vortex positioning but note very different arctic heights profile, a full 30mb different to ECM.

From there GFS has the energy splitting with a considerable amount spinning towards the Scandinavian side, and suddenly it is game on with a split vortex pattern, strong arctic heights and Europe in the firing line for some deep cold:

As the energy splits, height rises over Greenland become reality.

So ECM or GFS? GEM sides with ECM at 10 days:

JMA at 192 (as far as it goes) is loaded with potential as arctic heights are closer to the GFS call and a spit from here is very obviously possible:

ECM ensembles are still saying no to severe cold with the north perhaps seeing some interesting conditions but the south in the back pocket of the azores high:

CPC automated charts from yesterday say increasingly yes with a more meridional look:

Basically we have a split signal here, with evidence suggesting a shift in the region 4/5/6/7 Feb but still considerable doubt over the modelling of arctic heights and particularly the location of Canadian energy. Back in December people need to remember that it went pear shaped and vortex energy left in the atlantic put paid to cold for a good long time. However this time around I think at worst we will see a delay of the transition of a few days, maybe around 9/10 Feb. Funnily enough that is exactly where RJS put it...

Should be a fascinating few days of model watching coming up in the midst of a dull week.

Edited January 27, 2013 by Catacol_Highlander

[Polar Maritime]

I tend to lean towards the CPC chart's for trends, while following JH over the past year they seem to be a very solid model to use.

He should be back from his skiing holiday soon, i look forward to his analysis.

Edited January 27, 2013 by Polar Maritime

[Timmytour]

Strongly disagree with this.

If you look at the overall trend of the ensembles i.e GEFS/ECM rather than just a few operationals then you will see a clear signal towards a sustained cold spell developing around the dates I said earlier.

I think we are about two weeks off the return of "real winter" which is about what we were when the signs of the recent cold spell came up. i remember you picking out the date of 14th Jan out a couple of days into the New Year which turned out to be remarkably accurate......even if you did have a couple of subsequent doubts about whether it would arrive at all!

This time i think you have it wrong....i think it will arrive a couple of days earlier! I think the first thursday of February will see its onset

[Frosty.]

I think some are raising the expectation to high at this early juncture- The models - especially the GFS is showing some 'tentative' cold signs way out in past 192-

However the biggest problem will be getting heights to retrograde all the way from the atlantic then circumnavigate greenland & towards Svalbard-

In the last 10 years we have perhaps seen that type of scenario 1 / maybe 2 times- late feb 2005 springs to mind.

High risk synoptics- big rewards if they come off, but varification very low in the modelling arena in the last decade..

the ECM 15 ENS mean has dropped slightly below average at the tail end & the control goes cold- reasons to be upbeat- but we need to be firmly realistic.....

S

Yes but since there is another downwelling phase from the recent SSW, we are right to be optimistic of another model implosion coming out of the blue in the next few weeks, and even without that implosion, the overall trend is heading in the right direction, albeit slowly but since the last cold spell has only just ended, impatience is probably taking hold at the moment, a mild blip and then trending cooler and colder few days at the end of the week with snow showers in the far north and wintry showers pushing south with a few frosty nights, if the ecm and gfs 00z verify, and they should be close to the mark at this range.

[Methuselah]

Let us not forget that, back in mid-December, there was 'cross-model agreement' (call it what you will!) that 'real winter' was a mere 5-days' off...In other words, if I - or anyone-else, for that matter - could consistently predict Britain's weather, I - or anyone-else - would be head of the Met Office, by now...

If there's one thing I learned, from a decade on NW, it's that there are always 'signs', 'indications' - or what-have-you - of impending Snowmageddon...Even if it is only grebes!

Let's keep our heads level, for now, eh??

[phil nw.]

I think Steve M is right about being realistic wrt to deep cold at this early stage.Colder yes after the next few days as the jet tilts more NW-SE.

The ens mean Hts anomals. are promising from days 10-15 for a euro trough and retrogressing Azores High postitioning further west with time and some ridging north as are the CPC 8-14 day forecasts.

http://176.31.229.22...-0-0-240.png?12

http://www.cpc.ncep....y/814day.03.gif

There are suggestions from the GFS ens day15 ht anomls of a pattern something like the forecasted Feb. MJO Phase 8

http://www.cpc.ncep....clivar_wh.shtml

which is this

similar to later some GEF`s outputs.

We are looking into week 3 of the outputs if we are to see this though so early days yet but certainly signs of continued vortex fragmentation and the retreating Canadian energy in the medium term are all positive signs.

[Panayiotis]

Another beauty of an ensemble at 240hrs. This was yesterdays ensemble (18z) at 240hrs (left) and todays 06z ensemble at 240hrs (right).

Great upgrade! Lets see what the 12z has in store for this period in 2 hours time...

[Summer Sun]

The first of the afternoons 12z's is out

No change really an unsettled and wet week temperatures should peak on Tuesday for all

Also worth noting Alex deakin on the BBC weather for the week ahead said a suggestion and thats all it is that is may turn colder next weekend as the isobars head north

Edited January 27, 2013 by Gavin.

[Summer Sun]

By Friday the Atlantic is starting to get blocked off

Its a slow process but its getting there

Edited January 27, 2013 by Gavin.

[Panayiotis]

This is looking good! Atr 126hrs we have a channel low, but it wont act as a normal channel low bringing in a easterly as we have another low over Norway/Sweden which counter acts the easterly, but by this low being more south it will bring the northerly winds more south as it passes therefore colder uppers reach the south..

And at 138hrs we have -5/6C uppers covering the whole of Britain..

Edited January 27, 2013 by Panayiotis

[Dibdabbers]

Hi all, Is there a consensus on here as to which charts and runs are the most reliable. I'm trying to get to grips with them and it would be useful to know what everyone thinks...

[-uksnow-]

Hi all, Is there a consensus on here as to which charts and runs are the most reliable. I'm trying to get to grips with them and it would be useful to know what everyone thinks...

The ECM, GFS + UKMO are regarding the highest (in that order I think), models such as the JMA and GEM Come after those three - any other models are mostly regarded as joke models such as the Australian BOM.

[Tim Bland]

I wonder whether the UK can squeeze a snow event next weekend.

It could be rain turning to snow as that low clears into the continent, much depends on how much cold air can be tapped into from the ne.

Still disagreements as to the detail for the end of the week but certainly something to look out for in future outputs.

Snow possible in the south Sat morning, shown up on a few runs now http://www.meteociel.fr/modeles/gfse_cartes.php?ech=138&code=0&mode=2

[cooling climate]

Out to t174 and the Atlantic high starting to respond to the heights building over the Arctic.

Could be a peach of a run in FI.

[Panayiotis]

Up she goes! We want that low to the NE Iceland to move SE asap!

[nick sussex]

The GFS has a rain turning to snow event for the south, also a short window with some convective snow potential for the se.

The UKMO probably also has a shortish window of snow showers towards the se, unfortunately we don't get the 6hr frames but I think that also has a chance of some snow.

[Snowman.]

To much energy still over Greenland not enough went through.

That high will also topple.

[Summer Sun]

Once more tonight any cold shot is looking short lived with high pressure quickly building back sending the cold air east

We go from this

To this in 2 days

High pressure then keeps the real cold away

This is starting to remind me of the February freeze last year eastern Europe was in the freezer whilst the UK avoided the worst of the cold

Edited January 27, 2013 by Gavin.

[Grimsby Snow Lover]

Once more tonight any cold shot is looking short lived with high pressure quickly building back sending the cold air east

We go from this

To this in 2 days

High pressure then keeps the real cold away

This is starting to remind me of the February freeze last year eastern Europe was in the freezer whilst the UK avoided the worst of the cold

More importantly the trends remains for pressure to build towards Greenland during the first full week of February. The detail will change run to run and at present I would not be too concerned that the cold on this run remains too far east as this will no doubt change nearer the time (further east/west who knows). Plenty to look forward to if you ask me as the zonal train is looking pretty short lived at present.

Edited January 27, 2013 by Grimsby Snow Lover

[Summer Sun]

UKMO was close to building pressure later this week this morning and tonight its done it

[bradymk]

Once more tonight any cold shot is looking short lived with high pressure quickly building back sending the cold air eas

This is starting to remind me of the February freeze last year eastern Europe was in the freezer whilst the UK avoided the worst of the cold

Those charts you post above Gavin do not show Eastern Europe in the freezer so i am not sure what you mean by that. Also, there will be a big difference between if too much energy goes over the top of the high compared to if it does not and these are only small margins and something you would expect not to be modelled too well in GFS low res. Anyway, still a concern is the amount of energy remaining west of Greenland but this will also not be modelled well at this stage. When the high does ridge in, the winds would be a cool NW flow with frost and fog widespread. Back to your comment regarding last February, it certainly does not remind of last February. I am going to call you High pressure loving Gavin from now on I thought Steve M post earlier was great and I think we are not seeing signs of a sustained very cold pattern yet but it looks to turn colder once again into week 2. Personally I think this will develop into a more sustained period of cold once again.

[Jason M]

I suspect that the models are overplaying the cold next weekend. As we get nearer I would imagine that the models will flatten things out somewhat. The AZH is the biggest player in town for the next 10 days. Beyond that,we will see but with this set up in the past you wl usually see nice eye candy in the ensembles before they gradually get removed nearer the time. There is a big difference between a circular displaced AZH and a blocking high.

Jason