Model Output Discussion 29th December - Into mid-Winter.

[frosty ground]

7 minutes ago, Mucka said:

I'm not trying to be pedantic, just give some clarity.

Basically low pressure going under block is described as undercutting. You can say it has slid under the block if you like but it still wouldn't make it a "slider" which is a specific term to describe low pressure disrupting "sliding" down the Eastern flank of a ridge - at least that has always been my understanding.

People can call things whatever they like for me but it gets confusing if people are using the same terminology to describe very different events.

If you track the low I called a slider it ends up between Sicily and Tunisia around the block......

[swfc]

2 minutes ago, Nicholas B said:

Truly hope the 06z operational is wide of the mark,  past the cold spell later this week it has a Bartlett high all the way. Worst case scenario but its a definite possibility with how things look to be playing out.

indeed and that euro high would see out jan with nothing really wintry as such to show!! guess feb will become the new dec now!!!

[johnholmes]

The term 'slider' is not found in any professional meteorological glossary. Other than a specific term apparently used in California. It is another word/term that has found its way into sites like Net Weather. Paul B gave his definition about 10 years ago which has since been used on here, usually during the winter months.

[chris55]

GFS again a mild outlier compared to the Ensembles. Especially from the 14-18th, when compared to the mean and the ECM.

[karyo]

4 minutes ago, Nicholas B said:

Truly hope the 06z operational is wide of the mark,  past the cold spell later this week it has a Bartlett high all the way as the ridge slowly moves SE . Worst case scenario but its a definite possibility with how things look to be playing out.

It looks good stratospherically though for later in January. In fact, all the gfs runs in the last couple of days have offered a squeeze of the vortex from the Canadian side. Hopefully, the euro high won't last too long this time.

[Seasonality]

4 minutes ago, Nicholas B said:

Truly hope the 06z operational is wide of the mark,  past the cold spell later this week it has a Bartlett high all the way as the ridge slowly moves SE . Worst case scenario but its a definite possibility with how things look to be playing out.

Well, to trot out a few well worn NW cliches it is the 06z bin it, or should it be the 06z is notoriously progressive... Ha ha, seriously though, thankfully this is in FI and as we know, currently even short term output shows disagreement. Also the GFS is not on the same page as ECM as they move forward. And my own anecdote, GFS seems to be resolutely modelling a mild breakdown in Europe of late, which keeps getting pushed back (just my observation, not scientific!). Any output is a "possibility" but don't start panicking yet Mr B!

[Mucka]

16 minutes ago, frosty ground said:

If you track the low I called a slider it ends up between Sicily and Tunisia around the block......

It just gets absorbed into the trough.

Here it is over Ireland, Central England, Holland 

Then being pulled SE by the trough through Germany before phasing

 

Funny thing is that once it gets into Holland it does begin to slide and sharpen the European ridge.

A good way to see whether it is sliding is check the boundary between warm and cold air as it should not move West to East if the low is sliding but keep roughly the same boundary.

Edited January 9, 2017 by Mucka

[samadamsuk]

Morning all,

Does anyone have any thoughts on the GFS potential for transitional snow on Saturday as the Atlantic pushes in ? - looks possible to me. Further afield we're back in to FI imo looking for wintry weather, with WAA ramping up in the medium term. 

John, I always thought the direction of travel of a low was controlled by the orientation of the warm sector and how that propagates forward the system, along with the stage of maturity and where the occlusion was (curving north of the JS once occlusion takes place) - I'm not sure how a slider would differ - im no expert so interested to hear.

 

Samos

 

[chris55]

There looks to be a few solution to the west, with speed and positioning of the lows/ridge and the handling of "that" small mid Atlantic low.

GFS  lifts it up and into the flow and it ends up in Holland by 144!

ECM keeps it west of the ridge and it get scooped up by the trough to the north which then begins to disrupt against the ridge.

UKMO has a different solution with less of a ridge but no apparent Atlantic low.

Baffles me as to where we will end up.

 

[Dennis]

Lets bring the retro

[chris55]

7 minutes ago, samadamsuk said:

Morning all,

Does anyone have any thoughts on the GFS potential for transitional snow on Saturday as the Atlantic pushes in ? - looks possible to me. Further afield we're back in to FI imo looking for wintry weather, with WAA ramping up in the medium term. 

John, I always thought the direction of travel of a low was controlled by the orientation of the warm sector and how that propagates forward the system, along with the stage of maturity and where the occlusion was (curving north of the JS once occlusion takes place) - I'm not sure how a slider would differ - im no expert so interested to hear.

 

Samos

 

This "potential slider" ( its not a slider on the GFS yet*) has been touted on a few runs over the last few days but not consistently. If we get the ECM solution it wont even exist, but if we end up somewhere between GFS and ECM then i do see some potential for it to slide up against what would need to be a slightly more pronounced ridge ahead. The cold air would be in place.

Way to far out with all the discrepancies at the moment but something to keep an eye on. And even if it did land as GFS 06 suggests some transient snowfall is likely.

Edited January 9, 2017 by chris55

[johnholmes]

6 minutes ago, samadamsuk said:

Morning all,

Does anyone have any thoughts on the GFS potential for transitional snow on Saturday as the Atlantic pushes in ? - looks possible to me. Further afield we're back in to FI imo looking for wintry weather, with WAA ramping up in the medium term. 

John, I always thought the direction of travel of a low was controlled by the orientation of the warm sector and how that propagates forward the system, along with the stage of maturity and where the occlusion was (curving north of the JS once occlusion takes place) - I'm not sure how a slider would differ - im no expert so interested to hear.

 

Samos

 

Yes, pre computers a rough guide to the movement of a low with a warm sector was in the general direction of the average direction of the warm sector isobars and, another very rough rule was, I think, (long long time since I used this!) was 2/3 of the average speed shown by those warm sector isobars.

re the 'slider' |I honestly have no knowledge of how this is dealt with.

Edited January 9, 2017 by johnholmes
spelling

[The Weather Dragon]

assessing the output it looks like a 2/3 day cold snap - snow falling anywhere but only really settling at higher elevations more particularly in the north - nothing unusual. Clutching at straws regarding a decent easterly - just cannot see it myself 

[frosty ground]

Some of the Ensembles show a reload from the north west..... (Example.)

[weirpig]

Control trie to bring in a easterly.

[Mucka]

ECM ensembles, chilly mean and still a good cluster going for remaining cold. Otherwise a lot of spread and noise.

[warrenb]

3 minutes ago, Mucka said:

ECM ensembles, chilly mean and still a good cluster going for remaining cold. Otherwise a lot of spread and noise.

That is a good 10 days below 5C, which in my book is a cold spell rather than snap.

[karlos1983]

3 minutes ago, Mucka said:

ECM ensembles, chilly mean and still a good cluster going for remaining cold. Otherwise a lot of spread and noise.

Replicating exactly this thread this morning 

still not a bad set mucka, the mean is actually pretty decent, although you could argue trending ever so slightly milder toward the end.

[Mucka]

2 minutes ago, warrenb said:

That is a good 10 days below 5C, which in my book is a cold spell rather than snap.

It certainly would be a long cold spell by UK standards if it came off.

 

GFS ensembles by day 10/11 have winds from S,SW,W,NW,N,E and SE.

That must mean a Northeasterly is on the way 

Anything but the Euro slug please.

[frosty ground]

GEFS is rather bullish about ending the cold Saturday. 

[Mucka]

2 minutes ago, frosty ground said:

GEFS is rather bullish about ending the cold Saturday. 

Certainly as far as uppers go. Slightly more encouraging in keeping the surface cold, though with a lot of spread.

Edited January 9, 2017 by Mucka

[Seasonality]

2 minutes ago, Mucka said:

It certainly would be a long cold spell by UK standards if it came off.

 

GFS ensembles by day 10/11 have winds from S,SW,W,NW,N,E and SE.

That must mean a Northeasterly is on the way 

Anything but the Euro slug please.

Not a bad effort from the control run at 10 days. Pleasantly chilly for all of Europe! Not able to post charts at the moment sorry, but the control keeps Europe in the freezer.

[karyo]

3 minutes ago, frosty ground said:

GEFS is rather bullish about ending the cold Saturday. 

So even the control agrees 

[weirpig]

Just now, Seasonality said:

Not a bad effort from the control run at 10 days. Pleasantly chilly for all of Europe! Not able to post charts at the moment sorry, but the control keeps Europe in the freezer.

It Certainly does  a much better run all around from the control   brings a chilly easterly towards us  will feel much more like winter.

[bluearmy]

Gefs are quite a wide spread on solutions though a notable cluster keeping it cold (both surface and uppers) as others have noted and in line with the latest eps. Of course if we do return to a more mobile flow off the Atlantic (which remains an option) all those colder runs will be gone and the ten day cold spell will become rather shorter !