Model Output Discussion 18th Nov.2013-12z onwards.

[Frank Trough]

MetO has the pattern setting up much further West than GFS thankfully.

 

Looks better initially definitely but wouldn't it all just get bulldozed shortly afterwards? I really want to see some seasonal weather during December and i admire the stoic determination to see the positives but i really find it hard to see anything other than a fairly dismal start to December.

 

 

*edit* I've just realised that perhaps you can't call a "Bartlett" in advance because the definition of one is longevitiy - which we don't really know until it's happened? is that correct?

Edited November 23, 2013 by phil nw.
deleted the off topic-although humorous- remarks

[Tom Montalbano]

It does of course depend which 500mb anomaly charts one uses and how carefully one uses them. A correct prediction of 70% or more 10-15 days out over a 4 year period whatever the season makes we pretty confident using the 3 that I do use with their outputs. As always IF they show consistency over time and with themselves and are not at 180 degrees to other indicators. Never ever take one run, one model and use to predict what you think may happen. Use everything available and the first class inputs from other folk to help your assessment and analysis is something we can all do on Net Wx. I am constantly amazed at how many folk with no meteorological training have such depths of knowledge.

Hi John, I wasn't quite sure whether you were paying a compliment to some of the more technically gifted on here or if I was being gently chastised! LolAnyway, no problem whichever. The point I was making, was that an anomaly chart, is an anomaly chart, is an anomaly chart, whether it be from ECM, NAEFS or whoever and not a forecast chart and should not be confused as such.And actual forecast charts obviously will not correlate with anomaly charts,which is a trap some of us fell into, a few years back. I distinctly remember GP suggesting pressure anomalies for a long range forecast for D,J,F, which turned out to be pretty accurate, only to be unfairly criticised when some members wrongly interpreted his anomaly forecasts to be actual forecast heights, which would have resulted in a far colder Winter than actually ensued. As ever,the devils in the detail!Tom Edited November 23, 2013 by Kentish CZ

[Mucka]

Looks better initially definitely but wouldn't it all just get bulldozed shortly afterwards? I really want to see some seasonal weather during December and i admire the stoic determination to see the positives but i really find it hard to see anything other than a fairly dismal start to December.

 

interested to hear to about the "shedhead/drastik" breakdown love-in during the summer. shame it's all ended in divorce now.

 

*edit* I've just realised that perhaps you can't call a "Bartlett" in advance because the definition of one is longevitiy - which we don't really know until it's happened? is that correct?

 

Initially yes but hopefully the trough that comes in behind would set up far enough West to give us a taste of Winter a la some of the GFS ensembles.

I'm not saying it would, no real way to know but much better be here at 144 than GFS IMO.

 

ECM at 144 is not that far from UKMO but is a little further West again - I would love to keep seeing small Westward adjustments and eventually a much stronger mid Atlantic ridge setting up (not the 144 ridge - the likely one further upstream) rather than a toppler or something far worse such as GFS and its limpet slug of HP.

 

Edited November 23, 2013 by Mucka

[bradymk]

GFS is having an absolute nightmare with the low in USA. No agreement with the other models. Accuweather have been slating it all week. 

[Duane S.]

Looks better initially definitely but wouldn't it all just get bulldozed shortly afterwards? I really want to see some seasonal weather during December and i admire the stoic determination to see the positives but i really find it hard to see anything other than a fairly dismal start to December.

 

interested to hear to about the "shedhead/drastik" breakdown love-in during the summer. shame it's all ended in divorce now.

 

Indeed, that would very likely just get flattened. I think the interest in terms of real potential lies beyond the first week of December. That said, anything zonal looks even further away than real cold.

 

And with the main vortex more biased towards the East coupled with a West based MLB in situ, this COULD change quite quickly in our favour if we start seeing upstream amplification / increased wave activity towards the end of December. Not the favourite solution IMO but has to remain a possibility.

 

EDIT: Meant the end of 'November'!

Edited November 23, 2013 by s4lancia

[Summer Sun]

ECM going with UKMO at t144

 

 

Out of the big 3 GFS is on its own at t144 (nothing new there then)

 

GEM is also taking a similar route

 

 

The question mark for t168 on ECM is where the high goes does it back further west allowing a northerly in or does it move east again settling things down

Edited November 23, 2013 by Summer Sun

[Cheshire Freeze]

I've seen worse patterns to staring down the barrel at

 

[Mucka]

I've seen worse patterns to staring down the barrel at

 

 

 

 

Yes just a sniff of the trough setting up far enough West to displace our limpet high and bring in some colder air - how amplified behind though?

Edited November 23, 2013 by Mucka

[Summer Sun]

North to north westerly winds at t168 as Autumn 2013 comes to an end

 

 

So ECM is back to the original idea it had a few days back that later next week could bring something cooler from the north / north west

Edited November 23, 2013 by Summer Sun

[Mucka]

Oh dear, ah well there is always the next run.

 

[draztik]

Hi draztik...to be honest I wish I could find something +ive for the development of a cold pattern, whether that be within the ops, ensembles or even the teleconnctions.  However I can't, in fact all I can currently see is a slowing sinking HP dominated pattern, a slowly deepening PV and a resultant slow transition to milder, more unsettled conditions from the north.  You may see things differently, as may others, but no amount of wishful thinking, positive vibes or glass half full talk will change the overall picture...at least as I see it.

 

BTW, I seem to remember you singing from very much the same hymnsheet as me back in the summer, as several of your PM's back then atest.

you're absolutely correct shed, the difference being im not changing my tune in winter. Whenever the ens were trending for a cool down back in the summer, I was quick to highlight it. I only try and post what the models are showing, be that in summer or winter. Unfortunately I don't possess the necessary skill to dismiss a set of ensemble data from the models.

The GFS control is indicating heights building to our NW, with a trough to our NE / (or indeed, over us) - while the ens, have the trough further to our NE. But im definitely seeing a trend develop, and for me interesting times ahead; of course it could go either way, but id consider these positive signals for cold fans.

[Summer Sun]

winter opens up with the high slowly edging eastwards as we maintain a north westerly flow

 

[Tamara]

Hi Tamara. I have to disagree with the prognosis of stable +AO conditions becoming 'bedded in'. What we're seeing modelled is anything but a traditional +AO or even +NAO. Given the pressure distribution which we're seeing being unravelled in the medium term by the NWP, I see it only as a matter of time before this 'holding pattern' breaks down. As far as holding patterns go, on the face of it it's not the most wintry scenario but should ultimately lead to something infinitely 'better' than what we're seeing at present. At the moment in time, I don't think a westerly episode will even see out the first week of December.

 

A +QBO isn't necessarily the death knell of winter.

 

Furthermore, as I understand it a -EPO is actually correlated to a -AO?

This is where the conundrum lies. A +AO/-EPO correlation can and does exist, and this November is a very good example of that as it is the pattern that has dominated most of the month. Generally speaking, as I understand it, a large differential between the two indices is not sustainable indefinitely - and a deeply +AO generally forces the EPO positive eventually and a trough replaces the ridge over the Aleutians. This is influenced by seasonal wavelengths and it can be the case that the separation is not sustained into the winter months as the seasonal wavelengths lengthen.

 

But this is where the state of the stratosphere comes in and the likely future behaviour and direction of travel of the vortex in determing its strength and where the strongest areas of vorticity energy lie.  The current -EPO is assisting with the wave breaking pattern and keeping the bulk of the vortex over Siberia at present, but the strength of the vortex is muting any significant disturbance from troposphere/lower stratosphere activity to increase amplifciation of the pattern and reduce the +AO values that are a measure of its strength. On the basis of the vortex keeping strengthening and any wave breaking failing to have any impact (it has already been shown to have had little effect), then there is a real risk that it could re-organise itself back towards Greenland and Canada. This would reduce further the chances of any colder incursions getting south and a predominantly even flatter tropical maritime pattern would ensue with the jet stream aligned SW-NE.

 

Hence the best opportunties lie further into the winter in line with the +QBO being expected to decay through the winter and give better blocking opportunities. The +QBO is indeed not the deathknell necessarily of winter - but then at this time of year when the vortex is traditionally coming towards its strongest peak, then polar westerly assistance from the QBO that enhances the natural direction of travel around the polar stratosphere and makes it spin even faster is its greatest ally - and means that any available 'stick' put into it from the troposphere increasingly has to made of something akin to iron.

 

So we best hope we don't run out of sticks too soon, whatever they are made of

[Cheshire Freeze]

Oh dear, ah well there is always the next run.

 

 

I'm putting greater focus on ridging Pacific side. In the GFS ensemble members which promote a N Atlantic block we see the Pacific ridging aid a disintegration of the western side of the vortex which is what the general gist of my posts earlier were getting at.

[Summer Sun]

t216 we are back with high pressure over the UK

 

[Catacol]

Problem is with have a jet stream thats pretty much doing this through the whole run:-

 

 

 

Which i think is only helping to keep that high in place with low pressure steering along the jet into norway.  It also remains fairly static - at least thats how i read it.

 

I would have thought we would need that jet to start heading south of us, enabling high pressure to move in a northerly direction, don't really care which way just north will do. With the jet south it would also allow the cold air to flow south. 

 

But thats just a chart produced by a model at 204 hrs - i don't know how reliable the models are at forecasting jet streams at that range so it could be entirely wrong. 

 

For better or worse, right or wrong, I have come to the conclusion that the jet is not a driver of our patterns. I think the jet ends up where it is due to the shape of our pressure patterns and the overall rossby wave shape. Taking this approach it is therefore no surprise to see that jet forecast - it is simply a reflection of the hemispheric wave pattern and the pressure patterns in our part of the world.

 

What controls the pressure and wave patterns themselves? That is a discussion for the tech thread... but I wouldnt get too hung up on a jet forecast on its own.

[Mucka]

I'm putting greater focus on ridging Pacific side. In the GFS ensemble members which promote a N Atlantic block we see the Pacific ridging aid a disintegration of the western side of the vortex which is what the general gist of my posts earlier were getting at.

 

Yes I understand, you are playing the long game but while the door is not slammed tight on a turn up in around the 7/8 day range I'm going to stay wishful.

Edited November 23, 2013 by Mucka

[Summer Sun]

t240 ends with colder air moving closer to Scotland as the high moves south

 

Edited November 23, 2013 by Summer Sun

[Frosty.]

Tonight's GEM 12z delays the cold plunge but the shape of the jet and the positions of the atlantic high and scandi trough are pretty similar to the 00z and with the nw / se alignment still intact, a good blast of polar maritime possibly veering towards an arctic outbreak remains a possibility by early December, the anticyclonic signal has strengthened but the gem trend from previous runs is still there.

[Cheshire Freeze]

Yes I understand, you are playing the long game but while the door is not slammed tight on a turn up in around the 7/8 day range I'm going to stay wishful.

 

We're at the 23rd November and we're hardly seeing classic N Atlantic zonality. There's much to be satisfied with at present even if the general pattern in our locale is uninspiring at present. I think there is far too much unjust pessimism in here at the moment. I'm not straw clutching or trying to hopecast in the slightest......if you remember, December last year we had stellar charts being churned out but I never bought in to the whole evolution. Seems to be the opposite unfolding this year!

[alexisj9]

There seems to be a very big difference between the op and control run very early on, either can happen or anything in between, I would be happier with the out put it they agreed at least a little. The GFS is having trouble with something.

[MP-R]

Tonight's GEM 12z delays the cold plunge but the shape of the jet and the positions of the atlantic high and scandi trough are pretty similar to the 00z and with the nw / se alignment still intact, a good blast of polar maritime possibly veering towards an arctic outbreak remains a possibility by early December, the anticyclonic signal has strengthened but the gem trend from previous runs is still there.

 

Of interest there is the lows spiralling towards Spain and the Med. The other one out over the east Atlantic would also probably roll across underneath the high to north and from there it wouldn't take much to get us into a cold feed from the north to east.

[Frosty.]

Of interest there is the lows spiralling towards Spain and the Med. The other one out over the east Atlantic would also probably roll across underneath the high to north and from there it wouldn't take much to get us into a cold feed from the north to east.

Yes but i'm just pleased the GEM trend hasn't imploded tonight, still resembles the 00z which was the best run today whereas the gfs 12z op is dreadful.

[Cecil Hogmanay Melchett]

We're at the 23rd November and we're hardly seeing classic N Atlantic zonality. There's much to be satisfied with at present even if the general pattern in our locale is uninspiring at present. I think there is far too much unjust pessimism in here at the moment. I'm not straw clutching or trying to hopecast in the slightest......if you remember, December last year we had stellar charts being churned out but I never bought in to the whole evolution. Seems to be the opposite unfolding this year!

I see no reason to be optimistic at this juncture.

Its a classic +NAO setup,and looks like quite a stable protracted positive NAO  at that.

[Frosty.]

Tonight's ECM 12z op run is not as dire as this morning, the jet becomes aligned more towards wnw / ese with rather cold incursions from the northwest (polar maritime) and the run ends with colder air heading towards the uk, not as good as the gem but much better than the gfs.