Model output discussion - 5th December 2016 - Into Winter we go

[Frosty.]

Nice end to the Ecm 00z..high pressure in the ascendancy following a battle with the atlantic..hp delivers a knock out blow.

Edited December 7, 2016 by Frosty.

[mountain shadow]

4 minutes ago, Frosty. said:

Nice end to the Ecm 00z..high pressure in the ascendancy following a battle with the atlantic..hp delivers a knock out blow.

I think according to GP last night he would expect the PV segment over Greenland to move East and the UK/Azores High to retrogress West then North West in response.

A big shout that, and the only thing snow lovers can grab onto.

[nick sussex]

The ECM output bites the dust this morning , looks like it was the worst of the outputs in terms of modeling the Iceland area. Quite surprised to see it so wrong within the T96 hrs timeframe. If the stakes were higher with a Scandi high and then we saw this drama with the shortwave then this thread could have got very ugly!

Overall this morning nothing of any real interest showing up in the next ten days, although  the ECM shows a crumb of hope  at day ten but overall we're stuck in a rut until we see upstream changes. 

Edited December 7, 2016 by nick sussex

[Gavin Hannah]

You step outside for a day or so, and come back to find the GFS raining on our parade.. again. I have the feeling, that if we are to get any sustained cold and snow before Xmas, it's not going to show its head on the charts until the last possible moment. Yet again, we seem to be seeing lots of promise just outside the reliable time frame and then BAM! It's gone a day later....

[Faronstream]

The NAO value is still close to neutral and trending slightly negative, how can the atlantic still be quite powerful in this mornings output? GFS updates too many times a day ( 2 would be the best like ECMWF) beacuse especially 06Z is in 75% of the times always the outliner and mildest

[mb018538]

The AO is trending towards its highest reading for 6 months - but after this there is quite a spread. A couple go sharply negative, but there is a larger cluster in the positive territory.

[Frosty.]

The GEFS 00z mean is still trending strongly anticyclonic for a time during the mid dec period with frost and fog returning but gradually becoming more unsettled later.

Edited December 7, 2016 by Frosty.

[ArHu3]

9 minutes ago, Faronstream said:

The NAO value is still close to neutral and trending slightly negative, how can the atlantic still be quite powerful in this mornings output? GFS updates too many times a day ( 2 would be the best like ECMWF) beacuse especially 06Z is in 75% of the times always the outliner and mildest

the gfs can't look too far into the future, therefor they run it 4 times per day to win 6 hours of forecasting vs ec

[Summer Sun]

Pretty much sums up this morning's ECM

Edited December 7, 2016 by Summer Sun

[Summer Sun]

It seems to be ECM ens v GFS ens this morning

 

[SLEETY]

Hmmmm that's a bad update ,hopefully it change again,but gfs keen lol place your bets 

Edited December 7, 2016 by SLEETY

[TEITS]

1 hour ago, mountain shadow said:

I think according to GP last night he would expect the PV segment over Greenland to move East and the UK/Azores High to retrogress West then North West in response.

A big shout that, and the only thing snow lovers can grab onto.

I am somewhat unconvinced of any retrogressing high and I shall explain why.

My personal preference is I would prefer to see a return of mobility with regards to low pressure systems because like the 18Z GFS illustrated something more favourable could develop. The problem I have with high pressure over the UK is typically the high pressure eventually sinks rather than retrogresses to a more favourable position. This is simply based on years of following weather patterns than anything else. So in my opinion a high pressure over the UK may bring frost overnight but to me it is just wasting winter away!

At the moment I cannot see any real potential for a change towards any signficant cold/snow. This is why I have hardly posted in this thread. If I was honest I didn't understand all the hype back in November. All these fancy teleconnections forecasts mean sweet FA if the potential is not shown on the model output at a sensible timeframe. Following the models is alot less stressful if you choose to only view the output to +240 and ignore the rest.

Edited December 7, 2016 by TEITS

[nick sussex]

The GFS 06hrs run now ejects the shortwave near Iceland! It's the clean separation  from the upstream troughing of this which could make a difference to how far north any high gets initially.

Edited December 7, 2016 by nick sussex

[carinthian]

Morning this bigger picture of the 500mb flow from UKMO at 144 hours is not bad. Note the cross Polar high pressure link from Siberia to Western Canada with a extensive -AO flow ( east to west/north to south ) with little zonal flow across the Atlantic.  Looks like a split in the Polar Vortex , one in the NE Canada but the main one resident  in Northern Russia. So height rises again on the cards to dominate much of Europe in 6 days time, signs of heights start to  fall in the South Med. If that comes off we could get the Atlantic trough to dig SE wards and then bingo retrogression of the Euro high can take place. Keep the faith, we will get there . Its very much a different pattern to last years Zonal train.

C

Edited December 7, 2016 by carinthian

[Ali1977]

Better looking run, high cut off over southern Norway

[Singularity]

With deep cold air over N. America interacting with much warmer than usual waters in the western N. Atlantic, the big question is whether the resulting cyclogenesis will be so powerful as to force a SW flow across the UK even when the background forcing favours a continental one or a least a col setup with neither one or the other.

With respect to this, the extent of any model bias toward too much cyclogenesis is very important when assessing our prospects relative to what the teleconnections point toward. I believe there is some - surely in the case of GFS at least - but does anyone know of any hard evidence to support this? If they do, and can share, I'll appreciate that very much .

[Singularity]

12 minutes ago, carinthian said:

Morning this bigger picture of the 500mb flow from UKMO at 144 hours is not bad. Note the cross Polar high pressure link from Siberia to Western Canada with a extensive -AO flow ( east to west/north to south ) with little zonal flow across the Atlantic.  Looks like a split in the Polar Vortex , one in the NE Canada but the main one resident  in Northern Russia. So height rises again on the cards to dominate much of Europe in 6 days time, signs of heights start to  fall in the South Med. If that comes off we could get the Atlantic trough to dig SE wards and then bingo retrogression of the Euro high can take place. Keep the faith, we will get there . Its very much a different pattern to last years Zonal train.

C

Glad to see I'm not alone in thinking it wasn't so bad despite first appearances.

It's wildly different to ECM and GFS with the vortex segment over western Asia days 4-6, as it remains far more intense with a lot less 'draining' toward Canada.

That cross-polar transfer - linked to the elongated vortex profile in the lower stratosphere - is part of the problem with the insane cyclogenesis threatening the settled regime next week. Another aspect for which bias information would be very useful - how long might it take to find and examine historical cases I wonder...!

[Singularity]

If you need something to hang your hopes on for a chilly and dry outcome by the middle of next week - it's the fact that we have a split jet situation coming up, and we know how poorly the models handle the ratio of jet stream intensity between the N and S arms, often underestimating the latter. Have fun staring at jet stream charts over the next few days 

[Seasonality]

For amusement, the GFS para shifts a monster blob of vortex over Scandi.

[Ali1977]

1 minute ago, Seasonality said:

For amusement, the GFS para shifts a monster blob of vortex over Scandi.

That would bring a cold Xmas 

Edited December 7, 2016 by Ali1977

[weathernewbie]

1 hour ago, TEITS said:

I am somewhat unconvinced of any retrogressing high and I shall explain why.

My personal preference is I would prefer to see a return of mobility with regards to low pressure systems because like the 18Z GFS illustrated something more favourable could develop. The problem I have with high pressure over the UK is typically the high pressure eventually sinks rather than retrogresses to a more favourable position. This is simply based on years of following weather patterns than anything else. So in my opinion a high pressure over the UK may bring frost overnight but to me it is just wasting winter away!

At the moment I cannot see any real potential for a change towards any signficant cold/snow. This is why I have hardly posted in this thread. If I was honest I didn't understand all the hype back in November. All these fancy teleconnections forecasts mean sweet FA if the potential is not shown on the model output at a sensible timeframe. Following the models is alot less stressful if you choose to only view the output to +240 and ignore the rest.

Absolutely., how many times does FI fail to materialise. We all know the amplification of any near term data model inaccuracies (at that range) can easily make it way off point, but who here doesn't gaze into the distance and raise their hopes.  So glad to see you're still here posting TEITS. 

[swfc]

Looking at the ecm and gfs this morning at 240 hrs"fi granted" the gulf is huge and shows where things are atm.Ive no idea what the nhp will look like at that time range but as teits mentioned any building of heigths to the north west looks unlikely tbh!!!

[carinthian]

Funny how the latest run from GFS fires up the zonal train at 240 hours and then drops it 36 hour later ( as shown on this picture ) All very uncertain.

 C

[Ali1977]

1 minute ago, carinthian said:

Funny how the latest run from GFS fires up the zonal train at 240 hours and then drops it 36 hour later ( as shown on this picture ) All very uncertain.

 C

This has been a theme of a few runs lately,  and whilst we see this happening there is nothing saying it couldn't fall right for us. 

[bluearmy]

The extended eps removes the Azores ridging into w Europe which allows a broad shallow upper trough to establish 

the jet look strong to our west but seems to want to split approaching the e Atlantic and the absence of the upper ridge to our sw will allow more energy to head se. 

As matt has tweeted, a flow from the west seems more likely now (if the gefs are barking up the wrong tree) but a split flow would open up some trough disruption avenues. Cluster assessment would allow for a better view but I think currently a more active Atlantic headed into the uk and disrupting across w Europe is probably favoured.