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

[mountain shadow]

Looks like we could be entering a phase of northerly topplers driven by the MJO.

Certainly no sign of an extended cold spell but continue to hope that SSW influences can have a snowy impact on our wee islands.

[Polar Maritime]

I am going to call you High pressure loving Gavin from now on

I think most on here are well aware of Gavin's fascination with high pressure..

[mulzy]

In all honesty, the GFS and UKMO are pretty poor in terms of sustained cold. UKMO 144 pattern will just flatten out with a significant chunk of the PV over eastern Canada driving a strong flat jet i suspect.

[Jaffusmaximus]

I think most on here are well aware of Gavin's fascination with high pressure..

Its more a fetish

[Snowman.]

Rince and repeat...

[therecoil]

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.

When do you see this happening for the south east ,Nick ?

[cooling climate]

The GFS 12z seems to me to be making to much of a meal out of transfering energy

west to east under Greenland while at the same time trying to amplify the pattern. It just

seems to be a mess but having said that this occurs in low res and at 200+ hours out so

is understandable I suppose.

I would still expect to see some juicy ensemble members though with the continuing trend

to look towards the east for our next real cold shot.

[Summer Sun]

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.

What I said was last year, they are starting to remind me of how it panned out last year parts of eastern Europe are under -12 uppers which are pretty chilly

[legritter]

Tonights ECM should throw some more light on any chance of a cold spell but it will just be that .wouldnt be surprised if tonights GFS is a good one for cold past 240hrs . but we have all been here before ,the only thing i think staring us all in the face is how we are heading intoa very disturbed weather pattern .if the low shown on GFS takes the forcasted route it could give some surprises on its journey .i personally think high pressure will set up in either mid atlantic or just to our west next week ,but all depends on exact positioning intensity and shape . there is a very deep low over Newfoundland which looks like travelling up the west of greenland and jetstream moving south again ,so i think the dice is loaded a bit in our favour but needs to fall right . remember from small acorns come mighty oaks but oaks can be blown down ,just my take on current output cheers all ,

[Cheshire Freeze]

There seems to be some hopecasting by some members tonight that this cold spell won't materialise-not sure of the reason for this.

GFS shows repeated attempts to form a Greenland high. I suspect this will be close to the mark and it will take a couple of attempts to get there. Owing to the energy still left from the east Canadian vortex. Repeated bursts of WAA will, in reality, take us over the mark some time before the 14th of February I suspect. First attempt (phase one) shown 5/6th February.

Even with the topplers shown, the NW should do well from repeated,cold NW'lys bringing falling snow in the form of showers (including Cheshire gap).

Anything but spring like.

It was only a couple of days ago we were being preached to by members that we were looking at a 3 week zonal spell!

Edited January 27, 2013 by CreweCold

[ScottSnow]

What I said was last year, they are starting to remind me of how it panned out last year parts of eastern Europe are under -12 uppers which are pretty chilly

Don't really think its synoptically looking anything like the start of last Feb in Europe. The start of last Feb Europe was firmly in the freezer and dominated by easterly winds, at the minute Europe looks mild in comparison. This time we are looking more for pressure to rise in the Atlantic allowing northerly winds to develop.

None of the current runs look particularly mild in my opinion. I enjoy skiing and the current output certainly keeps the mountains in Scotland under snowcover. I believe we will see a couple of shortlived northerly incursions before a rise in pressure to our north west will allow a more sustained northerly regime to develop.

[Summer Sun]

GFS develops any interesting little feature in the south later this week with the potential for some significant rain in the areas which don't need it

Now I said interesting because as it pulls away some snow may develop on its back edge

[2810lollypop]

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

eastern & parts of southern britain did feel that cold for quite a while & we had lots of snow here in hastings ! so in all fairness not all of the uk avoided the worst of the cold last febuary .I remember it well along with the huge gas bill lol

[snowmadchrisuk]

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

It's a nice try , but I think the first shot will fail , but let's hope as it does , the P/V transfers to Siberia and we get another pressure build behind .. I think something is brewing , I don't think it will be another Feb 2011 where it all looked promising but failed.

Edited January 27, 2013 by snowmadchrisuk

[SMU]

There seems to be some hopecasting by some members tonight that this cold spell won't materialise-not sure of the reason for this.

GFS shows repeated attempts to form a Greenland high. I suspect this will be close to the mark and it will take a couple of attempts to get there. Owing to the energy still left from the east Canadian vortex. Repeated bursts of WAA will, in reality, take us over the mark some time before the 14th of February I suspect. First attempt (phase one) shown 5/6th February.

Even with the topplers shown, the NW should do well from repeated,cold NW'lys bringing falling snow in the form of showers (including Cheshire gap).

Anything but spring like.

It was only a couple of days ago we were being preached to by members that we were looking at a 3 week zonal spell!

I think perhaps you need to be able to distinguish the difference between a 'true' greenland high & some transient ridging into Greenland-

The GFS has not developed a greenland high in any model except the odd 18z flirtation at 360.

You are of course trying to blend the models to your forecast, but it reality there are ZERO greenland highs being modelled so you current assessment is a little wide of the mark-

The GFS tends to perform well in Northerly topplers, infact I recall December when I used the DAY 10 GFS 12z to forecast an outcome when did land very close.

Also when the prospects are there for a proper GH the GFS tends to model that very well with vertical advection from a Neg tilted high well west of Greenland-

What we have here is a positive tilted low when will overun the pattern- there is of course 2 ways 2 cold from the east from this evolution- one from a genuine GH looks out of the question, not just because of its absence in the models but also from its total absence this Winter-

THe other evolution is the low 'toppling' reaches greenland & a chunk of energy dives south drawing some high pressure towards Svalbard where eventually you get undercutting-

Again as rare as hens teeth.....

I would say people need to sit tight, proper cold ( thats away from a quick northerly toppler) is still 8-10 days +++

S

as roy walker used to comment: Say what you see....

Edited January 27, 2013 by Steve Murr

[Cheshire Freeze]

I think perhaps you need to be able to distinguish the difference between a 'true' greenland high & some transient ridging into Greenland-

The GFS has not developed a greenland high in any model except the odd 18z flirtation at 360.

You are of course trying to blend the models to your forecast, but it reality there are ZERO greenland highs being modelled so you current assessment is a little wide of the mark-

The GFS tends to perform well in Northerly topplers, infact I recall December when I used the DAY 10 GFS 12z to forecast an outcome when did land very close.

Also when the prospects are there for a proper GH the GFS tends to model that very well with vertical advection from a Neg tilted high well west of Greenland-

What we have here is a positive tilted low when will overun the pattern- there is of course 2 ways 2 cold from the east from this evolution- one from a genuine GH looks out of the question, not just because of its absence in the models but also from its total absence this Winter-

THe other evolution is the low 'toppling' reaches greenland & a chunk of energy dives south drawing some high pressure towards Svalbard where eventually you get undercutting-

Again as rare as hens teeth.....

I would say people need to sit tight, proper cold ( thats away from a quick northerly toppler) is still 8-10 days +++

S

Not at all Steve, the difference between a ridge and a cut off high is a pretty rudimentary one to grasp. The attempt at a cut off high is there and can be seen by looking at the wider hemispheric profile and the disintegration of the vortex over the arctic with associated raised heights in that locale. The GFS shows ridging and nothing else (both 6z and 12z) but to say the attempt isn't there is the thing that's wide of the mark IMO.

Also I would never try and skew what's shown to fit my 'agenda' because quite simply I don't work to agendas and no forecaster should. It's one sure fire way to fail at what you're doing.

The signs for a cut off high in February have been (and still are ) there for all to see.

If I recall correctly, you were quick to criticise people who had doubts over the failed December spell, guess what it didn't come off. Then you had a two day spell of dismissing the cold spell we've just departed- guess what it lasted 2 weeks and I saw the most snow I've seen for 10+ years.

It's easy to criticise people but harder to get a forecast at 2+ weeks to come to fruition

Edited January 27, 2013 by CreweCold

[Methuselah]

There seems to be some hopecasting by some members tonight that this cold spell won't materialise-not sure of the reason for this.

Could be something to do with fact that, many a 'hopecast' cold spell never quite manages to happen CC? I should know, I've been hopecasting for 45 years!

Edited January 27, 2013 by Rybris Ponce

[SMU]

CC can you show some links or data for a cut off high over greenland- as they simply dont exist.

S

[Bristawl Si]

There seems to be some hopecasting by some members tonight that this cold spell won't materialise-not sure of the reason

It was only a couple of days ago we were being preached to by members that we were looking at a 3 week zonal spell!

Thing is though CC, with only tentative signs showing of a return to cold in the future, one could argue that the "hopecasting" is coming from those saying there will be a cold spell.

[Jason M]

CC can you show some links or data for a cut off high over greenland- as they simply dont exist.

S

Indeed, lots of examples of the dreaded AZH mid Atlantic blob and the odd temporary ridge but full on Greenland highs are rather thin on the ground. If its coming it will be via a Scandinavia high / ridge. Greenland high will happen though, we just need to wait until late April.

Jason

[nick sussex]

Well between 120 and 144hrs if it verifies, certainly don't bank on it just yet as there are still differences between the GFS and UKMO at that timeframe.

You need a decent cold input into the precip from the n/ne and thats still too far out to be sure of.

[TEITS]

Very little change in my opinion since this morning.

A shortlived N,ly on the 2nd Feb followed by a 48hr spell of W,lys as clearly shown on the ensembles.

http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=304&ext=1&y=82&run=12&runpara=0

Another spell of N,lys around 4th-6th Feb.

Beyond and note yet again how the PV shrinks and weakens into FI.

If you read the Met O forecast they suggest colder with above average precip in the S & E. Now what pattern would cause that?

Well the answer isn't a convective E,ly because the forecast would of said E/NE areas. This is a clear indication of something we haven't seen so far this winter and that is a GH, Negative NAO, LP tracking S. The reason they don't mention snowfall because at this stage its impossible to say because only a slight shift N or S makes the difference between rain or snow in these patterns.

So apart from the 48hr W,lys around the 3rd Feb it will turn progressively colder from the N before winter really returns with a vengeance and at the moment im saying the 10th Feb is the day this will occur.

Quick note about the N,ly at +144. I doubt this will bring much snowfall as its classic case of by the time its cold enough any precip has moved away apart from a few showers.

[SMU]

TIETS if there was a clear GH in the 32 ECM ( consistent ) & the MOGREPS

then their wording would have been more positive towards cold... the METO is a little neutral which is where the models seem to sit at day 10 tonight-

Cold over Central Europe with low heights- a possibility of this coming west with time...

S

[chris55]

TIETS if there was a clear GH in the 32 ECM ( consistent ) & the MOGREPS

then their wording would have been more positive towards cold... the METO is a little neutral which is where the models seem to sit at day 10 tonight-

Cold over Central Europe with low heights- a possibility of this coming west with time...

S

How do you get this West Steve without high pressure to the north?

[Cheshire Freeze]

TIETS if there was a clear GH in the 32 ECM ( consistent ) & the MOGREPS

then their wording would have been more positive towards cold... the METO is a little neutral which is where the models seem to sit at day 10 tonight-

Cold over Central Europe with low heights- a possibility of this coming west with time...

S

Steve RE your question.

You may well be right.....a true GH may be pushing things at this point and within guidance from the NWP (may be overly optimistic in cut off heights scenario). However I think heights to the south of Greenland and modest heights over the plateau look quite assured at the very least.

I don't know why there is negativity though, potential for cold looks quite high, even with a slightly more southerly placed HP than you would ideally like.

FWIW CFS continues with general theme...

colder than average 850s

and continuing into March (same as last night)

Edited January 27, 2013 by CreweCold