Model Output Discussion 01/09/17

[chrisbell-nottheweatherman]

8 minutes ago, knocker said:

After last night's anomalies worth a quick look at this evening's to see if there any further indications as to where the evolution is going.

The 6-10 (the latter part of which is where the pattern starts a transition) is much the same as previously. Upstream the twin vortex lobes Russia and N. Canada and the strong N. Pacific ridge with the tenuous connection to the high cell in the Franz Joseph Land region. The Canadian lobe has troughs orientated SE & SW and also a pathway to the trough north and east of the UK.

There is a fairly flat westerly upper flow across the US but it splits on leaving the eastern seaboard where much of it swings SW around the ridge south east of Greenland and then north west over the UK to the trough just to the east whilst the other arm more in the direction of Iberia and points further south

Thus the likelihood of it staying unsettled in this period with troughs tracking north of the ridge and dropping SE in the vicinity of the UK possibly introducing some quite wintry weather particularly in the north with temps below average.

The transition continues to be indicated in the 10-15 period.  Upstream the two vortex lobes become more diffuse and the Canadian one drifts into the Arctic as the high cell over Franz Joseph Land loses it's identity. This promotes positive anomalies NE Canada and Greenland and the Atlantic ridge and the trough to the east moving east. This leads a much slacker NW flow as the UK becomes more under the influence of the HP and more settled weather with temps below average. There is a fine line here and there is not complete agreement between the three downstream and the key remains the precise amplification and orientation of the two major players.

Would you agree, Malcolm, that tonight's anomaly outputs are showing a continuation of heights near the Pole further into the latter part of the period modelled than yesterdays' outputs indicated?

[knocker]

10 minutes ago, chrisbell-nottheweatherman said:

Would you agree, Malcolm, that tonight's anomaly outputs are showing a continuation of heights near the Pole further into the latter part of the period modelled than yesterdays' outputs indicated?

Looking at the EPS Chris possibly slightly but still losing the high cell in the Franz Joseph region around T240 with at that stage low pressure across the Arctic connecting the two vortex lobes rather than before the HP ridging across.

Edited November 11, 2017 by knocker

[ICE COLD]

The GFS 18z turns into a horror show . Let's hope that's  not a new trend ? Why do I model watch so frustrating

[swfc]

Incredible change on the 18z on the nhp.not sure where thats come from time period wise!!!!

 

 

 

 

Edited November 11, 2017 by swfc

[Jonan92]

It's kinda amusing to see how many times a small low comes out from the atlantic into the middle of the block avoiding the chance of creating a solid block

e.g

[Nick F]

17 minutes ago, Mucka said:

GFS 18z goes with the theme of a flatter pattern too and just a brief waft of cooler uppers which are gone before the weekend is out.

High lat blocking has certainly been watered down through today but maybe just a wobble.

 

 

Yes, 18z GFS with the much flatter, less amplified flow over the Atlantic, with no wave breaking of the trough over eastern Canada to help amplify the flow downstream over the N Atlantic.

Still, teleconnections still seem to favour a blocked N Atlantic thanks to the weakened and convoluted jet stream over North America caused by the anomalously strong Aleutian high. 12z EPS clustering at t+240 gives strong support for mid N Atlantic blocking.

 

So plenty to be optimistic about, despite a possibly wayward 18z GFS ... which I think is too quick to rid of the mega Aleutian block and replace it with troughing which then opens up a zonal and stronger jet to take over downstream and prevents wave breaking and blocking over N Atlantic.

[cyclonic happiness]

11 minutes ago, Jonan92 said:

It's kinda amusing to see how many times a small low comes out from the atlantic into the middle of the block avoiding the chance of creating a solid block

e.g

Shortwaves for the win :-(

[feb1991blizzard]

Suddenly after the 18z GFS we now have a zonal late Nov / Early Dec in the offing, I have to say I did warn about the inevitable collapse but I am taken aback by the speed of it, the sudden acceleration, I didn't expect a 'That ECM' style collapse (ie such a quick one) but we might well have it, the only positive is that the uppers were never conducive to extreme cold a nd huge dumpings like with Dec 12 in the first place so even if the last weeks modelling would have verified, I'm not sure many places would have received what I categorize as a tonking.

[Nick F]

10 minutes ago, feb1991blizzard said:

Suddenly after the 18z GFS we now have a zonal late Nov / Early Dec in the offing, I have to say I did warn about the inevitable collapse but I am taken aback by the speed of it, the sudden acceleration, I didn't expect a 'That ECM' style collapse (ie such a quick one) but we might well have it, the only positive is that the uppers were never conducive to extreme cold a nd huge dumpings like with Dec 12 in the first place so even if the last weeks modelling would have verified, I'm not sure many places would have received what I categorize as a tonking.

Too early to declare a zonal rest of month and early Dec based on one GFS op run, a look at the 12z EC ensembles suggests N Atlantic blocking could be a strong possibility. There is still the chance that the trop PV will begin to organise as we head into early winter as the strat cools from top to bottom, as hinted by strengthening of zonal winds in EC forecasts on Berlin site, but for now the trop blockiness and weakish and amplified jet seems to be in control for next few weeks IMO. Below average temps more likely for a fair duration after this coming week’s milder blip, though less certainty of wintry precipitation away from the northern hills.

Edited November 11, 2017 by Nick F

[Cheshire Freeze]

11 minutes ago, feb1991blizzard said:

Suddenly after the 18z GFS we now have a zonal late Nov / Early Dec in the offing, I have to say I did warn about the inevitable collapse but I am taken aback by the speed of it, the sudden acceleration, I didn't expect a 'That ECM' style collapse (ie such a quick one) but we might well have it, the only positive is that the uppers were never conducive to extreme cold a nd huge dumpings like with Dec 12 in the first place so even if the last weeks modelling would have verified, I'm not sure many places would have received what I categorize as a tonking.

The speed of it was always inevitable, as we saw last year. It's what happens when you have an strat profile non conducive to blocking. Relying on the perfect trop pattern for wave breaking to occur successfully is risky and can quickly go wrong. It's the reason I have been ultra cautious all week.

The signs were there yesterday and perhaps the day before that the AO may not go as negative as first thought. This was owing, in the short term, to a decrease in vertcial advection Pacific side. After that, it's a domino effect.

 

 

[Boro Snow]

18z is not good but let's be honest the 850s have never been brilliant anyway, if it's cold rain you want below 400m then ok 

[blizzard81]

18z has always been the maverick of all model runs. Just like when it shows winter nirvana synoptics that never come to fruition, I will treat tonight's run with the same level of  suspicion. 

Edited November 11, 2017 by blizzard81

[BurwellWeatherWatch]

17 minutes ago, feb1991blizzard said:

Suddenly after the 18z GFS we now have a zonal late Nov / Early Dec in the offing, I have to say I did warn about the inevitable collapse but I am taken aback by the speed of it, the sudden acceleration, I didn't expect a 'That ECM' style collapse (ie such a quick one) but we might well have it, the only positive is that the uppers were never conducive to extreme cold a nd huge dumpings like with Dec 12 in the first place so even if the last weeks modelling would have verified, I'm not sure many places would have received what I categorize as a tonking.

very impressive to have predicted the demise, that hasn't yet happened, of an event that also hasn't yet happened - but either way may still do! On balance it's probably good to be seeing "I told you so" posts before even mid November, as it means there is at least some interest in the models this year. With 3 weeks to go until winter, i reckon it's going to be a long one!

18z a bit dull tonight, but if it was the other way round we'd just be told to ignore it...

[feb1991blizzard]

14 minutes ago, Nick F said:

Too early to declare a zonal rest of month and early Dec based on one GFS op run, a look at the 12z EC ensembles suggests N Atlantic blocking could be a strong possibility. There is still the chance that the trop PV will begin to organise as we head into early winter as the strat cools from top to bottom, as hinted by strengthening of zonal winds in EC forecasts on Berlin site, but for now the trop blockiness and weakish and amplified jet seems to be in control for next few weeks IMO. Below average temps more likely for a fair duration after this coming week’s milder blip, though less certainty of wintry precipitation away from the northern hills.

Do you think though in recent years, whenever a block to the N of us (whatever exect location), we seem to have so much less margin for error in that the 2 areas of low heights seem to engage each other after a few runs when initially it seemes there is so much gap in between them giving us seemingly a lot of leeway, it almost as if the only way we will get a proper Easterly again ever is if there's a high straggling almost half the of the globe!!!!!!!

 

EDIT : Big downgrade on GEFS as well, 0c 850 line was in spain on 12z, now its in Birmingham.

Edited November 11, 2017 by feb1991blizzard

[blizzard81]

1 minute ago, BurwellWeatherWatch said:

very impressive to have predicted the demise, that hasn't yet happened, of an event that also hasn't yet happened - but either way may still do! On balance it's probably good to be seeing "I told you so" posts before even mid November, as it means there is at least some interest in the models this year. With 3 weeks to go until winter, i reckon it's going to be a long one!

18z a bit dull tonight, but if it was the other way round we'd just be told to ignore it...

Post of the day

[blizzard81]

Some kneejerk posts based on the gfs 18z. Let's at least wait until the 00z runs before we write the obituary. 

[bobbydog]

 

yes. because meteorological organisations the world over have been anxiously awaiting tonights 18z GFS, to decisively predict the winter of 2017/18 once and for all. 

or not....

Edited November 11, 2017 by bobbydog

[Scandinavian High.]

I’m still going for cold blocked conditions it’s looking very good if you want some seasonal weather for November I’m going to bin that gfs run ..

[Cheshire Freeze]

2 minutes ago, blizzard81 said:

Post of the day

Not really.

If you step back and look at the bigger picture, you will see even the more learned on here have preached caution with the upcoming spell due to lack of supporting background signals, along with the longer range seasonal models which have almost unanimously and consistently pointed towards a +NAO tendency for the upcoming months. 

Of course you may say 'just one run' but it's pertinent to note that the flatter runs are closer to what we can expect given the stratospheric state at the moment, amongst a plethora of other factors to consider. With that in mind, you have to prepare for something many of us do not want to see i.e a more Atlantic driven outlook rather than one affected by an abundance of N blocking.

[Nick F]

16 minutes ago, feb1991blizzard said:

Do you think though in recent years, whenever a block to the N of us (whatever exect location), we seem to have so much less margin for error in that the 2 areas of low heights seem to engage each other after a few runs when initially it seemes there is so much gap in between them giving us seemingly a lot of leeway, it almost as if the only way we will get a proper Easterly again ever is if there's a high straggling almost half the of the globe!!!!!!!

There is always the danger that high latitude blocks will be undercut by troughing which keeps the real cold at bay from the UK, yes. Certainly it’s more unusual in November for blocks to sustain a cold pattern across the UK for long, than say in Jan or Feb when there is a greater chance because of SSWs propagating down. Exception was late November 2010 of course, though don’t think we are heading that route for now, but I still think there’s some merit in a blocked N Atlantic that will keep the UK locked into a below average spell of temps, until ECM decides to move away from this signal as well.

Edited November 11, 2017 by Nick F

[bobbydog]

4 minutes ago, CreweCold said:

Not really.

If you step back and look at the bigger picture, you will see even the more learned on here have preached caution with the upcoming spell due to lack of supporting background signals, along with the longer range seasonal models which have almost unanimously and consistently pointed towards a +NAO tendency for the upcoming months. 

Of course you may say 'just one run' but it's pertinent to note that the flatter runs are closer to what we can expect given the stratospheric state at the moment, amongst a plethora of other factors to consider. With that in mind, you have to prepare for something many of us do not want to see i.e a more Atlantic driven outlook rather than one affected by an abundance of N blocking.

come on mate, what happened to your old optimism? have you been possessed by the ghost of ian brown?  

[Cheshire Freeze]

7 minutes ago, bobbydog said:

come on mate, what happened to your old optimism? have you been possessed by the ghost of ian brown?  

LOL

I just don't think the model thread is a place for hopecasts and unfounded optimism...the banter thread can be used for that purpose.

I promise you though that as soon as things genuinely look interesting (from a more holistic rather than just NWP perspective), I will be the first person making my optimistic thoughts known

For interest, here is the latest CFS 850s anomaly for December...it has hardly budged on this for a long time now, if we look at the averages

3 month pressure anomaly D-J-F

Edited November 11, 2017 by CreweCold

[blizzard81]

11 minutes ago, CreweCold said:

LOL

I just don't think the model thread is a place for hopecasts and unfounded optimism...the banter thread can be used for that purpose.

I promise you though that as soon as things genuinely look interesting (from a more holistic rather than just NWP perspective), I will be the first person making my optimistic thoughts known

All well and good but I do notice you have only come out with your thoughts after the underwhelming 18z which followed a full day of very positive runs from a coldie perspective. Edit - your thoughts as in today. 

Edited November 12, 2017 by blizzard81

[Cheshire Freeze]

2 minutes ago, blizzard81 said:

All well and good but I do notice you have only come out with your thoughts after the underwhelming 18z which followed a full day of very positive runs from a coldie perspective. 

Where have you been all week...

Pretty sure you can check my post history and see I have, in fact, been urging caution for a number of days...

Regards

[blizzard81]

2 minutes ago, CreweCold said:

Where have you been all week...

Pretty sure you can check my post history and see I have, in fact, been urging caution for a number of days...

Regards

Absolutely, I realised my bad choice of words so edited my post. I know you have always been sceptical about the current output but I was referring to today's posts.