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

[Scandinavian High.]

The uk is on path of some very cold snowy weather there south east of England looks worse place to be snowed in if that cold pool comes this way.

Edited December 30, 2016 by abbie123

[mhielte]

7 minutes ago, Singularity said:

 

When it comes down to it, the upstream amplification is what really counts for the longer-term, and it will take a further substantial shift for the Azores low to cause enough trouble to prevent that from doing the job. UKMO might well be at that point which is alarming, though as implied earlier it has enough of a hang-down of lower heights to place an undercut of the high at just +168 hours on the table. Not something I'd bet on, but you never know - we should see what the run gets up to later this evening via that alternative view people have started making use of.

 

Regarding the Azores low strength in the mid-range, something I noticed with the 12z GFS was that there was much more wave development along the frontal boundary moving south 1st-2nd Jan. This tricky feature could be important for determining how much development potential then exists for the Azores low to work with. Further swings may be possible in the 24-72 hour range, which is unusually close in time,

Really value analysis like this. Great post

That said maybe we know too much sometimes. I'm sure I was far less stressed than this viewing the 5-day forecast on Ceefax back in the day. Page 406 I think it was 

Edited December 30, 2016 by Polar Maritime
To move discussion on.

[Jason M]

I'm assuming Matt Hugo was being ironic because tbh I'd take that GFS run any and every day of the week. Cold, snow for all and power to add at the end!

If that's considered a bad run in its entirety I must have accidentally logged into a Canadian forum

[Paul_1978]

8 minutes ago, mhielte said:

Well he can, and he did. However the GFS op is way out on its own after the 6th. Matt is a knowledgeable chap but he jumped the gun a little on this one!

That's good news - 6th Jan is only T+159 so I'm ignoring the 12z op output after that. Might be best if many of us do for our own sanity!

[Iceberg]

Ens table out to 192 and it shows that a majority of the runs still bring the cold in 

[Mucka]

17 minutes ago, Iceberg said:

Here's the ens mean compared 06z an 12z at t240. I can't see a huge difference , except the higher pressure. 

No you won't see a huge difference as the better options still exist but that is a big change in a mean over a 6 hour period,  I expect contrasting with 00z the differences will be even more stark as I didn't actually look at the 06z ensembles but see they were flatter than 00z though still good.

The thing to notice is how much further East and flatter the ridge is.

Compare the 00z and 12z extended ensemble graphs when it is out for central England and you will no doubt see see how the mean 850's are quite a bit higher.

 

[Optimus Prime]

I see the carrots out in full force today. We should be very realistic about the outlook and not get too sucked in to what is being shown 7+ days away. The unreliable time frame charts are great to look at but lets remember as the res increases so often than not the eye watering synoptics go with them.

This certainly isn't 2010 where we have across the board agreement even a week out,

[BLAST FROM THE PAST]

No problem this run at all. Intense cold pooling, timing (ie to early) has been my only gripe of recent runs to my PoV.  Can still flip back as this is one run (which is still pretty darn good as a pattern) but even if not....it is ready to flood in from NE and E.  

 

 

BFTP 

Edited December 30, 2016 by BLAST FROM THE PAST

[Captain Shortwave]

GEFs

      

Still keen on a blocked signal with heights to the north and low heights to our south east, if anything this strengthens into week 3 with 850s  2-4C below normal by the end. All academic as to be honest the GEFs is having some continuity issues at the present so we can't overly trust the output though again the blocked signal is encouraging.

[AWD]

Just now, Paul_1978 said:

That's good news - 6th Jan is only T+159 so I'm ignoring the 12z op output after that. Might be best if many of us do for our own sanity!

I'm not ignoring it as it is a perfectly viable outcome, as well as the consistent UKMO.  

I'm just not taking it as done and dusted, whilst there are still other realistic options on the table.  Again, I await further 12z data.

FWIW, no model output portrays anything long-lasting mild or very wet.  The GFS 12z Op would certainly provide further pulses of interest in the first half of Jan taken at face value (which of course, it shouldn't be).  Plenty of cold, sub freezing minima on the GFS 12z too, just little in the way of the white stuff.

[Singularity]

Thanks @mhielte, it's nice to know that my input is appreciated alongside that of countless others on this forum 

One last contribution from me for the time being; it seems that where GFS differs markedly from UKMO is with the jet as it moves out of Canada at +96; GFS keeps it flatter, which maintains the cut-off low setup to the south for long enough that the wedge of heights can join forces with the upstream ridge and build nicely poleward during the following few days.

In lifting out the cut-off low sooner, UKMO keeps the ridges separate, which also leaves them weaker in the face of the Atlantic troughs. 

For this reason I don't see GFS as having backed down to UKMO at this stage; the stronger Azores low is not as far as I can see the cause of any quicker lift-out; rather it's how flat the jet is as it leaves Canada.

[Snowman.]

2 minutes ago, Paul_1978 said:

That's good news - 6th Jan is only T+159 so I'm ignoring the 12z op output after that. Might be best if many of us do for our own sanity!

It's different to the UKMO anyway so if it helps it's on its own!

 

[Summer Sun]

Op and mean both go on the warm side of the mean (black and blue lines)

[Iceberg]

Full tabular 12 ens out and still plenty of cold. 

 

[karlos1983]

If you were to just look at the ensembles having not seen the op, what would you say? Look cold to me. Usual scatter in low res.

 

[Snowman.]

6z12z

 

Hey at least the snow chance for the next few days have increased!

Edited December 30, 2016 by SN0WM4N

[mhielte]

1 minute ago, Summer Sun said:

Op and mean both go on the warm side of the mean (black and blue lines)

Huge scatter after the 7th though. Really anything could happen! Exciting but nerve-wracking all the same.

[Banbury]

21 minutes ago, mhielte said:

Well he can, and he did. However the GFS op is way out on its own after the 6th. Matt is a knowledgeable chap but he jumped the gun a little on this one!

Of course he did and of course he can as can anyone one here  doesn't mean he cant be challenged, yes he has a lot of knowledge but occasionally 'experts' can be wrong you know

Edited December 30, 2016 by Banbury

[Paul]

Nick's latest blog is well worth a read:

January turning progressively colder toward mid-month?

[snowking]

If we compare the last 3 GEFS median T2M values:

(Green - 0z, Red - 6z, Blue - 12z)

Not a huge difference between them. The 12z ~1c warmer in the mid range, but trending colder in the longer range.

Still plenty of model water to run under the bridge yet

[Scandinavian High.]

Very cold weather to come high pressure to north low to south north easterly or easterly winds .

[Gael_Force]

3 minutes ago, snowking said:

If we compare the last 3 GEFS median T2M values:

(Green - 0z, Red - 6z, Blue - 12z)

Not a huge difference between them. The 12z ~1c warmer in the mid range, but trending colder in the longer range.

Still plenty of model water to run under the bridge yet

Was just about to post the Meteociel version of that. Blue (latest run) seems to be more abundant as a colder cluster in the late stages.

[inghams85]

6 minutes ago, snowking said:

If we compare the last 3 GEFS median T2M values:

(Green - 0z, Red - 6z, Blue - 12z)

Not a huge difference between them. The 12z ~1c warmer in the mid range, but trending colder in the longer range.

Still plenty of model water to run under the bridge yet

Was about to post the same thing. It's timing differences. I think the models have been too quick to bring in the cold. Always looked like East/North Easterlies longer term

[Man With Beard]

17 minutes ago, Summer Sun said:

Op and mean both go on the warm side of the mean (black and blue lines)

That's still a very very cold set. 

I fully expect the ECM to be similar to ours 00Z run at least until T168. It's just a rogue GFS run. It's allowed one or two??

[Mucka]

GFS 00z/12z ensemble comparison 2m temps if people still can't see the shift.

 

The good news is that there are enough cold runs to keep other mean charts a little more ambiguous and of course a shift in one set doesn't mean they can't shift back.

 

ECM T96 a step toward UKMO but not all the way.

Edited December 30, 2016 by Mucka