Model output discussion - cold spell approaching?

[Mucka]

Yes all very tight. UKMO is borderline for sure, maybe just the right side of borderline.

GFS also very tight but just about keeps the low closed off without the phasing and is secure by 144 because of this.

The low W of Ireland will always move e and phase with the Scandi trough so long as  the cut off low tot he SW does not phase with it and create a trough to our W to stall it and pump up an Iberian ridge.

 

I Don't rate GFSp but I would be happy if this was right

But no so happy if this was

 

fine margins.

[northwestsnow]

UKMO 120 looked very good..

144 is poor though...

Nothing is straightforward for coldies in the UK..

Hope EC carries on from last night but I'm fearing it won't.

 

Edited January 12, 2021 by northwestsnow

[The Eagle]

Quite a snow maker on the GFS op though...

 

 

[Mucka]

 

Not to worried about FI, just getting the block secured through the mid term but this, Atlantic disrupting into V cold air, would be snow maker of yesteryear.

I expect if we get the  blocking though that low will exit t a good deal further S rather than stall and disrupt

[Kasim Awan]

I'm not too disgruntled by the initial limitation posed by the Iberian high & phasing. The pattern of amplification is ongoing, and potentially override these limitations to eventually bring in something worthy, as per the GFS 00Z. Nonetheless, from a cold perspective it is very frustrating to loose the potential of this first bout of amplification to Greenland.

[Battleground Snow]

8 minutes ago, northwestsnow said:

UKMO 120 looked very good..

144 is poor though...

Nothing is straightforward for coldies in the UK..

Hope EC carries on from last night but I'm fearing it won't.

 

Keep the faith NWS, gem is what we want a nice clean evolution. 

Sometimes a good precursor to what the ECM will show but not always

 

 

Edited January 12, 2021 by Battleground Snow

[weathermadbarnsleylad]

Like I always here people say in hear its only 1 run. Wait for the ensembles to compare the op run. Weekend not sorted yet never mind early next week. 

[Mucka]

4 minutes ago, Kasim Awan said:

I'm not too disgruntled by the initial limitation posed by the Iberian high & phasing. The pattern of amplification is ongoing, and potentially override these limitations to eventually bring in something worthy, as per the GFS 00Z. Nonetheless, from a cold perspective it is very frustrating to loose the potential of this first bout of amplification to Greenland.

We can't draw in a NE arctic flow until around the 19th/20th, we have tow ait for the Atlantic rubbish to clear E and phase with Scandi trough even in best case scenario.

For me it is an all or nothing situation and I won't mind waiting if we get the "all" solution.

Edited January 12, 2021 by Mucka

[The Eagle]

00z GFS is great but overwhelmed really by poor ICON, UKMO, GFS(P)

All down to the ECM. Depending on which way that goes it will be great here later or absolutely appalling.

[Kasim Awan]

Plus I suspect the second bout of retrogression, a term which I know @Mucka isn't a fan of, is now being explored by the NWP for around 200-220hours. It may be key in shifting the pattern amply south to bring cold air in. It's more of a high pressure waving westwards than classic retrogression. This exchange is visible on the GFS from Iberia > Azores around 192-230h though it's quite subtle. The NWP is processing a very complex delayed amplification given the new limitation posed by the shortwave. Eventually this leads to a very good outcome though.

[Battleground Snow]

JFF but what a @Tim BlandBland  snow map from the OP

[Kasim Awan]

2 minutes ago, Mucka said:

We can't draw in a NE arctic flow until around the 19th/20th, we have tow ait for the Atlantic rubbish to clear E and phase with Scandi trough even in best case scenario.

For me it is an all or nothing situation and I won't mind waiting if we get the "all" solution.

It's a textbook case of the binary concept (either phases / cuts off or doesn't), GFSP00Z and GEM00Z are two ends of the extreme of this binary logic which sometimes appears as a problem in NWP. I have to favour a middleground for this which would be partial phasing > temporary WSW winds before renwed amplification. This is why I feel the GFS00Z op is the most sensible solution yet. 

[Snowman.]

3 minutes ago, Mucka said:

We can't draw in a NE arctic flow until around the 19th/20th, we have tow ait for the Atlantic rubbish to clear E and phase with Scandi trough even in best case scenario.

For me it is an all or nothing situation and I won't mind waiting if we get the "all" solution.

It’s a tight race, ECM needs to pull through here with decent eps support, luckily it is early on in the output so we shouldn’t have to wait too long to find out. But betting on anything past Day 5 is definitely not something I would like to do.

[Mucka]

Just now, Kasim Awan said:

Plus I suspect the second bout of retrogression, a term which I know @Mucka isn't a fan of, is now being explored by the NWP for around 200-220hours. It may be key in shifting the pattern amply south to bring cold air in. It's more of a high pressure waving westwards than classic retrogression. This exchange is visible on the GFS from Iberia > Azores around 192-230h though it's quite subtle. The NWP is processing a very complex delayed amplification given the new limitation posed by the shortwave. Eventually this leads to a very good outcome though.

It isn't that I'm not fan, that was just me misreading what you were saying. While you were talking about retrogression and Westerly flow I was viewing a stonking 240 chart with -16 uppers on their way across the UK so I just took your post out of context.

It is a matter of preference as far as terminology goes and I just prefer to talk of the AH being displaced W rather than retrogressing as it requires forcing from a trough dropping down into Europe and the Iberian heights being pulled NW rather than retrogessing since it requires the link up with the Atlantic ridge to happen. The Iberian ridge is a consequence of troughing to the SW. If we avoid the Atlantic phasing then we have cut off low instead of a trough and only very limited ridging if any which will be no match for the Scandi trough pushing SW just so long as we have that Atlantic block in place.

[northwestsnow]

1 minute ago, Snowman. said:

It’s a tight race, ECM needs to pull through here with decent eps support, luckily it is early on in the output so we shouldn’t have to wait too long to find out. But betting on anything past Day 5 is definitely not something I would like to do.

Me neither ..

I be off to bed in a few hours, UKMO has alarm bells ringing now unfortunately.

An amazing NH setup  with a stupid high just where coldies dont want it.

GFS much better at 144 for me.

[Snowman.]

0z FI is absolutely incredible tho. Iberian heights erased with a good easterly feed across southern half of the UK with winds switching northerly further north you go. 
 

Means absolutely nothing but it is nice to observe 

[Snowman.]

2 minutes ago, northwestsnow said:

Me neither ..

I be off to bed in a few hours, UKMO has alarm bells ringing now unfortunately.

An amazing NH setup  with a stupid high just where coldies dont want it.

GFS much better at 144 for me.

UKMO is indeed a wake up a call to anyone trying to call this a done deal. GFS is incredible later on but it’s hard to place trust in it. ECM is our hope here to help calm the nerves before I skip the Prozac and head straight for the bottle.

Sleep well and hope the ECM & Eps delivers.  

[Battleground Snow]

3 minutes ago, Snowman. said:

0z FI is absolutely incredible tho. Iberian heights erased with a good easterly feed across southern half of the UK with winds switching northerly further north you go. 
 

Means absolutely nothing but it is nice to observe 

It has support of the control and more crucially the mean at 150.

I think the ECM will be good, but it's all knife edge stuff for our small Island

[Continental Climate]

Hate the fact that everything seems to be getting pushed back again. Having to wait for the second bout of GL amplification because the first one was scuppered by a stupid shortwave. Who's to say another shortwave won't pop up at t120. 

[Kasim Awan]

10 minutes ago, Mucka said:

It isn't that I'm not fan, that was just me misreading what you were saying. While you were talking about retrogression and Westerly flow I was viewing a stonking 240 chart with -16 uppers on their way across the UK so I just took your post out of context.

It is a matter of preference as far as terminology goes and I just prefer to talk of the AH being displaced W rather than retrogressing as it requires forcing from a trough dropping down into Europe and the Iberian heights being pulled NW rather than retrogessing since it requires the link up with the Atlantic ridge to happen. The Iberian ridge is a consequence of troughing to the SW. If we avoid the Atlantic phasing then we have cut off low instead of a trough and only very limited ridging if any which will be no match for the Scandi trough pushing SW just so long as we have that Atlantic block in place.

I tend to view retrogression in terms of high pressure as an east to west movement, regardless of the driving mechanism. The atmosphere is fluid - the Azores / Iberian high pressure may retrogress & be eroded simultaneously, which is what needs to happen 200-220h ideally if the phasing is not optimal because the phasing will amplify the Azores high. Thankfully, if there is phasing, I think there's a chance of the Azores being weakened given the strong troughing to the NE. For this reason too I am not entirely reliant on clean phasing, there are ways to get the cold in afterwards and I've seen many times the models evolve to the cold.

Edited January 12, 2021 by Kasim Awan

[Snowman.]

Just now, Battleground Snow said:

It has support of the control and more crucially the mean at 150.

I think the ECM will be good, but it's all knife edge stuff for our small Island

All well and good. I am still on high alert with regards to it all, as you say it’s a extremely knifes edge stuff. It’s going to be difficult for if it does completely phase to get something good together quickly. 

Just now, Continental Climate said:

Hate the fact that everything seems to be getting pushed back again. Having to wait for the second bout of GL amplification because the first one was scuppered by a stupid shortwave. Who's to say another shortwave won't pop up at t120. 

Alas when I saw my Dec 2012 easterly disappear in front of my very eyes due to a pesky shortwave I felt the same. 
 

We always need a little bit of luck here in the UK. Such a small segment of the hemisphere for things to align perfectly. 

[Snowman.]

Para going for the 2nd bout of amplification, now past D10 but still would rather have a 2nd attempt than not one at all!

 

4 minutes ago, Kasim Awan said:

I tend to view retrogression in terms of high pressure as an east to west movement, regardless of the driving mechanism. The atmosphere is fluid - the Azores / Iberian high pressure may retrogress & be eroded simultaneously, which is what needs to happen 200-220h ideally if the phasing is not optimal because the phasing will amplify the Azores high. Thankfully, if there is phasing, I think there's a chance of the Azores being weakened given the strong troughing to the NE. For this reason too I am not entirely reliant on clean phasing, there are ways to get the cold in afterwards and I've seen many times the models evolve to the cold.

 

[Mucka]

JFF -4C by day. That would 2010 levels of deep cold

Never that simple though is it?

[Mucka]

GEM has the low so cut off by 144 it never gets within 1500 miles of the UK and ends up exiting N 

Nice to see GFS control is very safe in this manner as well as others have mentioned.

Edited January 12, 2021 by Mucka

[Roger J Smith]

With just about the entire land mass of Britain and Ireland sub 516 dm by 324h GFS, that's a strong signal and seems unlikely to be entirely wrong. The GEM backs up the GFS evolution to ten days. I regard this as quite an upgrade from earlier runs, but the JH test is to compare same time runs, there it just holds serve, maybe a slight upgrade. (00z vs prev 00z).