[Model output discussion - another cold spell on the horizon?]

1 minute ago, IDO said:

Hi

If only statistics was as easy as you make it sound! You have to build into that 17/17/17 the ratio of those d10 Greenland highs, Atlantic ridge or Azores high being the solution by T0. Of course, we know that a d10 GH rarely lands at D0 so we would factor this in with an equation with those odds, ditto the other two possible outcomes. 

So although a 33% chance sounds great for a GH, the reality is that in a large sampling the chances are significantly less by d0. There are obvious caveats, but the mean is a balance to any "out there" solutions. If this was a plume from sub-tropical forcing then we would maybe have sub-set binning to qualify any results. Or if this is the imprint of an SSWE and we knew that for sure, then we would bin that factor. 

I think what we can say is that if the means are synoptic-wise correct (Scandi trough) then we should see increased chances of forcing to the Greenland region if we get a clean evolution. A real-life GH though, mostly in my dreams or in models in FI sadly!

@chris55 If you really really really simplified it & made all the pressures equal & had 3 fixed points

1) Greenland high for 17

2 ) Atlantic ridge for 17 

3 ) Flat pattern for 17 then of course the mean would show an atlantic ridge.

At the moment the 216 > 240 Means show the 552 contour level with ireland. 

That means the significant weighting is for 2-3 & a minor cluster for 1.

My next port of call then would be compare the 192 Mean 12z tomorrow with the 216 12z mean from today to see if there is any backtrack to a more amplified pattern.

The reality will be somewhere in the midpoint ....

[Model output discussion - another cold spell on the horizon?]

3 minutes ago, Scott Ingham said:

Your right. This is where weve had disagreements.

For clarity then so people know what im suggesting could he the outcome.

1) Greenland high (Contour line up one 3rd of Greenland

2) Cut off Greenland high (Same but cut off with low pressure under the high propping it up.

3) Greenland Ridge (Contour to the tip of Greenland)

4) North Atlantic High (Contour not reaching Greenland)

I see 168 to 240 us developing option 1 with a backing south west of the cold in Scandinavia

240-360

A WEST based option 2 - cut off from energy from the eastern seaboard. Slider and battleground snow favouring areas north of Southern Wales

So based on them terms what is it your saying you think will happen?

There is support in both eps and gefs for option 1 but this has dropped since this morning 

 

Somewhere between 2-3 - Maybe we can prop a wedge that sinks East slightly....

[Model output discussion - another cold spell on the horizon?]

5 minutes ago, Man Without Beard said:

Ok sorry mods for so many images but here's the op, control and first 10 ecm ensembles for D9, looking at North Pole view at 500mb. Won't do this again honest;

I'd describe 3 of them as Greenland Highs (a couple are a Greenland/N Atlantic combo), 1 or 2 others as a close shave. So in the minority at D9 - not quite as prevalent as the 00Z set, if the same proportion is evident in all 51 ensembles. Will check now, along with other dates

 

 

0 Greenland highs....

 

[Model output discussion - another cold spell on the horizon?]

2 minutes ago, Snowmut said:

So are you saying the GFS is a waste of space for sniffing out UK cold?

No thats 15% for a true GH

Also see above post...

[Model output discussion - another cold spell on the horizon?]

7 minutes ago, Scott Ingham said:

Your assesment of the 12z is correct if not a slight exaggeration with some good political language thrown in but after a ssw you cant take any model or even set as gospel really after 120z and there is Steve a large amount of support at that range for a greenland high/north atlantic ridge whatever youd like to call it in a logical place after shifting of the vortex back to asia and scandi

Possibly > Thats included in my 15% though > also inc is the GFS op. Thats all your getting...

I think really its just a matter of differentiation between an atlantic ridge & a true GH as remember there may be newer members that cant quite tell the difference yet - Some may see Greenland heights & think its the same as a true GH...

Also a GH would certainly guarentee the jet track in the atlantic being steered south now we are 'hoping' it stays south...

I would say 'moderate' optimism tonight for cold weather in the 7-10 window but maybe not deep cold.

Rain turning to snow thurs could be another curtain twiching moment this week...

[Model output discussion - another cold spell on the horizon?]

2 minutes ago, feb1991blizzard said:

I still think there could be an in between solution and until the ECM i always thought this the most likely solution - 2-3 days of very cold air - toppling - yes, but would slow the Atlantic and give further chances as well afterwards.

 

A slow toppler > yes thats in the Mix....

[Model output discussion - another cold spell on the horizon?]

4 minutes ago, snow mad said:

Do we need any upstream amplification? If the chunk of pv pushes its way into Europe. When the pv slides back into its normal winter home when a high pressure is in Greenland the pv has no trouble dislodging it. What with the jet not being as strong this year surely that’s a possibility.

Yes ...

1) High pressure enhances the advection process - Weaker high = slower / weaker CAA

2) High pressure stops / steers the movement East of the atlantic > without it cold will never last...

So the PV dropping into Scandi / Central Europe alone cannot drive the cold air west alone - it needs help..

[Model output discussion - another cold spell on the horizon?]

6 minutes ago, bluearmy said:

I won’t disagree with you based on the momentum but 99% confidence is too much with this spread around greeny at day 10. Clusters say it’s 33% 

 

I will give you 15% > that includes some goodwill

[Model output discussion - another cold spell on the horizon?]

7 minutes ago, bluearmy said:

Almost half the eps in the extended are in a distinct greeny ridge cluster ?. Those clusters days 9/10 looked very amplified around in greeny aswell 

I’m not sold on anything more than a decent wedge at the moment .....may well be enough given a strong sceuro trough 

Just looked at the 12z EPS.

Chances of a GH. 0% with 99% confidence.

552 Contour at 12z 216 EPS -

168 Jet to much positive tilt. GH will come from a northward vertical ridge not a ridge out of Canada.

A proper Greenland high

A lot of confusing wording on here being posted that should be made clearer for some of the newbies....

The *Best* case scenario is as @Kasim Awanmentioned a block in the atlantic that holds in situ long enough to deflect the atlantic track further south whilst the trough to the forces cold air south..

[Model output discussion - another cold spell on the horizon?]

Just now, Man Without Beard said:

Fair enough wrt the mean, but about 1/3 had a N Atlantic high ridging into Greenland, and another 1/3 had a full blown Greenland High. I suspect some deep troughs over Greenland on the other members flattened the mean

Look at the mean here.

( & others )

The 552 Contour is what we use to distinguish the wave height & whether thats a GH or an atlantic ridge.

The ECM 00z 240 mean has that contour adjacent to Ireland.

That means the GH cluster could be scrapped essentially.

 

When there is going to be a cut off GH that contour will be way up there over Greenland even at day 9/10.

[Model output discussion - another cold spell on the horizon?]

Just now, Scott Ingham said:

Yes.

In other weather patterns

Not in this pattern

Theu already discounted ecms flatter scenario in yesterdays discussion

You keep saying theres a GH on the means. There isnt.

Theres no GH on the GEFS means either.

So what your posting is totally wrong.

GEFS 12z Mean 192.

No GH.

EPS 00z Mean

No GH

12Z  GEM Means

 

The only model is the GFS operational.

Which means its 99% going to be wrong.

[Model output discussion - another cold spell on the horizon?]

2 minutes ago, Scott Ingham said:

I have to disagree with you on the first part mainly experience and from input shared im such scenarios from our friends in America. 

The envelope though is very large and as others have said id be very surprosed if this am outlier and we see the ecm move over to the GFS scenario

I dont personally see a cut off high shown on the 06z but i do see one further east cut off wothout gaining as much latitide.

But its the fun of model watching well see in due time!

The American pro mets rarely blend the GFS. Its always EPS & ECM & Occasionally GEM driven.

@nick sussex watched them most of the time. He will 100% say the same thing.

Euro blend > GFS always.

 

Also can you show the GH on EPS as it doesnt exist.

[Model output discussion - another cold spell on the horizon?]

1 minute ago, Man Without Beard said:

btw ECM ensembles this morning leaned heavily in favour of a Greenland High this morning, biggest risk to cold spell on that set was west based -NAO, not collapsed greenie. What will the next batch come up with?

They didnt mate.

There may have been a cluster however dont confuse a ridge & a GH on the anomalies 

00z 216 Mean. No GH

[Model output discussion - another cold spell on the horizon?]

10 minutes ago, Scott Ingham said:

Not in this situatiom

Gfs for Greenland heights

Ecm for split energy

I would say based on this and ensemble support the odds are 70/30 on a gfs solution but 30 % is still a percent and could come true

GFS will never be ahead of any euro for a greenland high.

The chances of a GH here are near 5% if not below.

Why? Because the models have to much positive tilt on the jet to develop anything other than a blocking atlantic ridge which may stay in situ long enough like the GEM to bring the cold air south more so than the ECM.

The solution lies probably somewhere in the middle.

It looked great intially with the vortex apparently dropping into Europe however that position is morphing North westwards towards Norway & this means it has to come round the back of a low pressure rather than direct NE > SW like before.

As a result its modified warmer & not as good.

 

[Model output discussion - another cold spell on the horizon?]

8 minutes ago, Kasim Awan said:

ECM to me isn't terrible? Mid Atlantic high setting up in a position favourable for continued bouts of amplification.

No > it is terrible.

Flat as a witches...

[Model output discussion - another cold spell on the horizon?]

The 216 is even worse...

As Said 2 days ago ..... Need to keep firmly grounded here. No booms or anything else until Euros on board.

[Model output discussion - another cold spell on the horizon?]

Just now, Djdazzle said:

If the ECM 192 is poor, people are setting their bar way too high. Not as good as GFS, but it’s a good chart.

Not really - No sub -4c air makes it a pretty poor effort

[Model output discussion - another cold spell on the horizon?]

Mixed emotions tonight

Excellent 12z GFS but another very poor ECM ...

Another day of waiting ....

The ECM OP continually being the odd one out - it has a history of being volatile - but we do need the euros on board...

[Model output discussion - January cold spell ending, what next?]

Day 5 swing back to cold for the SE -5c the midpoint & -8c the top out > could be some snow

[Model output discussion - January cold spell ending, what next?]

1 minute ago, Uncertainy said:

Glad to hear this Steve, the wedge was a beautiful but unlikely option but the day 8-9 trend was a day 14/15 day trend 6 days ago so it’s still counting down...

Also, that ECM op has 1030mb surface high over Scandi and it wouldn’t take much for that link up with the AR and the crazy 850s to advert westwards: that’s the key to the puzzle we’ve been missing so far this winter...

Your thoughts on the GLOSEA 3monthly run on Monday? The others have flipped, will the UKMO make it a full house?

I didnt see it - have you got an image -

S

[Model output discussion - January cold spell ending, what next?]

57 minutes ago, Day_9 said:

Wasn’t winter declared over in the first week of December?

No it wasnt.

It was just time to take a break - chasing the charts in early December rarely bares fruit so good to take a 2 week or so break

[Model output discussion - January cold spell ending, what next?]

Evening

My comments earlier were directly aimed at the slighter poorer medium term trend from UKMO today as it didnt follow yesterdays move to the wedge > infact it moved away from it.

The spirits have been somewhat lifted by the ECM Mean though > lets hope those crazy values are still there come day 3/4 

[Model output discussion - January cold spell ending, what next?]

A pretty poor day model watching.

UKMO has trended flatter, ECM also poor all the way out past 192.

We are pinning hopes on outputs past 200 again which is always dicey at best.

Shame really just as the deep cold was getting going like the good old days...

[South East and East Anglia Weather Discussion January 2021 onwards]

-2.1 / -2.3c at home already !!

[Winter 2020/21 chat, ramps, moans and banter]

GFS 06z looks improved through 66

sending more energy SE