Model Output Discussion 18z 30/09/15

[knocker]

Why would the jet sustain the blocking as it's the latter which guides the jet?

 

Moving on to the ecm which does energize the trough a tad but but not enough with the block too far east so the UK remains under the influence of cyclonic south westerlies. Into the ext period the trough remains the major player vis the UK so I might be tempted to revise blue's odds to 5/4 given current underfoot conditions.

Edited October 17, 2015 by knocker

[bluearmy]

I get what jmatt means knocks. The two are hand in hand once the ridge is established.

Edited October 17, 2015 by bluearmy

[knocker]

I get what jmatt means knocks. The two are hand in hand once the ridge is established.

 

But that doesn't fit with your earlier comment, "Even that jet profile shows it splitting across the UK. Given that the output usually over eggs the progress of the Atlantic against a block". And given the atmospheric circulation determines where the jet stream is positioned and hence where surface low and high pressures reside I'm still struggling as to how the jet sustains the blocking.

[Cloud 10]

 

 

Oh how I have missed these bonkers storms in the model output 

 

 

The 00z GEFS (P) delivers one of those "seeds" you speak of in rather dramatic fashion.

 

 

 

Tis' the season i suppose.

[bluearmy]

But that doesn't fit with your earlier comment, "Even that jet profile shows it splitting across the UK. Given that the output usually over eggs the progress of the Atlantic against a block". And given the atmospheric circulation determines where the jet stream is positioned and hence where surface low and high pressures reside I'm still struggling as to how the jet sustains the blocking.

The block will probably sink if the split jet does not maintain its southern arm enough. I believe Matt was simply referring to that. The mean anomolys show the emphasis of the low heights being driven into Europe to our South which will prevent that sinking. Everything is connected isn't it. I know exactly what you mean but I also know what the earlier post was getting at.

[knocker]

The block will probably sink if the split jet does not maintain its southern arm enough. I believe Matt was simply referring to that. The mean anomolys show the emphasis of the low heights being driven into Europe to our South which will prevent that sinking. Everything is connected isn't it. I know exactly what you mean but I also know what the earlier post was getting at.

 

Only problem with that is as Matt was quoting my post of the GEFS 11-15 anomaly there is no split jet running south. In fact there is no jet at all in the eastern Atlantic or NW Europe. So what is keeping the block up? And of course things are interconnected.

Edited October 17, 2015 by knocker

[Nouska]

Only problem with that is as Matt was quoting my post of the GEFS 11-15 anomaly there is no split jet running south. In fact there is no jet at all in the eastern Atlantic or NW Europe. So what is keeping the block up? And of course things are interconnected.

 

That's a good question - if you run down the time stamps on the Meteociel view, the block strengthens, and maintains position even as the Med troughing weakens and the jet disappears on the output.

 

http://www.meteociel.fr/modeles/gefs_cartes.php?ech=192&code=21&mode=5&carte=1&runpara=1

 

Is this a result of the atmosphere responding to the forecast heavy snows on top of an already good westerly extent?  Theory per Cohen et al.

 

Mike Ventrice comment on projected snowcover.

 

https://twitter.com/MJVentrice/status/655031788583178240

[Singularity]

Only problem with that is as Matt was quoting my post of the GEFS 11-15 anomaly there is no split jet running south. In fact there is no jet at all in the eastern Atlantic or NW Europe. So what is keeping the block up? And of course things are interconnected.

 

I can see this being a reflection of there being little consensus regarding the jet stream location in the eastern N. Atlantic. Meaning a wide scatter of outcomes, some having a split jet running south, some taking it northeast and 'over' the blocking high. A fairly standard situation when there's blocking to the east and northeast of the UK being dealt with.

 

In other news, the 'seed' is back on the GFS 06z and this time it really slams Iceland. It will be of interest whether such a powerful storm does turn up in the N. Atlantic within the next fortnight, regardless of where exactly.

[knocker]

And no great surprise where the jet is, running around to the north of the block.

Edited October 17, 2015 by knocker

[Singularity]

And no great surprise where the jet is, running around to the north of the block.

 

One arm of the jet, certainly. There's another one through the Med. which helps to sustain the block... this is how we end up with a 'Sceuro' block.

 

The northern arm will have to quieten down a bit if the block is to become a proper 'Scandi High'. This is hinted at late in the GFS 06z op run but at that range I'm not giving much credit to solutions either way for the time being. The ensemble means may spend some time suggesting the potential for things to go either way, as there's no clear signal yet to bring about a 'majority vote' from the perturbations.

 

The polar vortex has been looking a bit off a mess as we start November, so we may get to experience some interesting weather patterns at times. It does seem to fit quite well with the 'strong El Nino + westerly QBO' analogues that have been cropping up on here in recent times.

[Nick L]

There appears to be a delay with the GFS 12z this afternoon.

[ANYWEATHER]

There appears to be a delay with the GFS 12z this afternoon.

Indeed Nick. I was just going to post this myself! Perhaps the Gfs is cooking up some tasty and exciting synoptics    

[Nick L]

Starting to arrive now.

[knocker]

One arm of the jet, certainly. There's another one through the Med. which helps to sustain the block... this is how we end up with a 'Sceuro' block.

 

The northern arm will have to quieten down a bit if the block is to become a proper 'Scandi High'. This is hinted at late in the GFS 06z op run but at that range I'm not giving much credit to solutions either way for the time being. The ensemble means may spend some time suggesting the potential for things to go either way, as there's no clear signal yet to bring about a 'majority vote' from the perturbations.

 

The polar vortex has been looking a bit off a mess as we start November, so we may get to experience some interesting weather patterns at times. It does seem to fit quite well with the 'strong El Nino + westerly QBO' analogues that have been cropping up on here in recent times.

 

Really, sustaining the block? Well this is the chart that was under discussion not the one above.

Edited October 17, 2015 by knocker

[bluearmy]

I can definitely see it splitting on that chart knocker. It may not be particularly strong south or North but it splits nevertheless and if some of it is headed through the med, the block is aided in its position.

[knocker]

Well it hardly constitutes the word jet and you could just as well be looking at a 250mb contour chart and pressure distribution but I'll sign off on this now as I'm boring myself and everybody else and it's going nowhere fast. I'll go and check to see how the dafs are getting on.

Edited October 17, 2015 by knocker

[phil nw.]

It looks like our block starts to get eroded from the north west as we go into next week.

No surprise i guess as the ens have been pointing that way for a few runs now.

 

A look at the 12z GFS and UKMO charts can see this process underway at t120hrsrs.

 

 

further north we can see the westerly winds picking up across the top of the high as it eases south with patchy rain moving in off the Atlantic.

 

not a complete change to really unsettled weather yet tough as through the following frames there's still signs of occasional ridging from the High which still remains close enough to weaken any rainbands further south.

We should at least rid ourselves of this overcast and rather raw feeling setup that we currently have,with some brighter interludes between any frontal systems.

 

[knocker]

As you say Phil quite a fluid run by the gfs  The north could cop some nasty weather but of course it's jusy one run one model

Chart courtesy weatherbell

Edited October 17, 2015 by knocker

[Mucka]

Generally we have seen the models  tilt more in favour of a shallow trough for the 10+ day range and have it a little further East the last day or two but there is still a weaker signal for the trough to develop in the Atlantic and push some WAA toward Scandi and the higher latitudes.

 

The North should slowly come under the influence of low pressure next week and see some wind and rain at times which may or may not get further South  but we still are not seeing a standard zonal pattern develop IMO, at least not yet while the upstream remains fairly amplified.

[legritter]

Certainly looking like a break down come later next week ,but i think the full fury of the Atlantic will be kept at bay for some time yet .high pressure looks to be dominant ,but its exact location hard to pin down .I suppose the next few days could throw up some more detail but things are slow moving at the moment ,anything of note and action seems to be taking place away from our Shores at present .

Come on gang its time for a Stella or two ,winter will soon grace our computers [hopefully ] .

[knocker]

The GEFS anomalies tonight don't really resolve the evolution with any great confidence. The 6-10 has the trough to the NW and a weakening Scandinavian ridge slipping east and low pressure central Europe Thus the UK in westerly air stream. But the 11-15 retrogresses the HP and reinvigorates it so although the trough is still in attendance, a tad further west, and the UK still under a mainly westerly airflow the analysis is pretty much on a knife edge again and perhaps the NOAA 8-14 is on board with this but much uncertainty remains,

http://www.tropicaltidbits.com/

Edited October 17, 2015 by knocker

[johnholmes]

yes the NOAA 8-14 does show the UK under a more mobile 500mb flow. There are indications of increasing +ve heights way up n over n Norway. A couple of days down the line the anomaly 6-10 should be picking this up IF it is real?

link

http://www.cpc.noaa.gov/products/predictions/814day/500mb.php

Even if it does then its influence would be far from clear, if it has any major effect on the UK.

[carinthian]

The latest ECMWF charts do not look right. Low pressure forming to the SW, sinks south, then replaced in 24 hours by Atlantic ridge, this replaced by depression forming out of no where. This run all over the place. I would take with a pinch of salt. I am sure the picture will change again on tomorrows run. The developing Atlantic jet could split with many scenarios to form. The pressure zones over Europe and Scandinavia not determined as of this instant with -in the 10 day limit.

C

[Paul]

Strat thread for winter 15/16 is now open - and includes a huge amount of info that's well worth reading in Chiono's opening post 

 

https://forum.netweather.tv/topic/84231-stratosphere-temperature-watch-20152016/

[aitchbomb]

No OPI figures available this year?