Model Output Discussion - 31/10/2014 and Beyond

[LomondSnowstorm]

So this will be the SEVENTH time that the GFS has tried to build a strong PV since the start of October. Current success rate: 0 out of 6. 7th time lucky? (and I really do mean 'lucky')

 

I have to concur with this - the GEFS mean showing a slightly more organised looking mean vortex by +384 than the currently very disorganised vortex isn't really surprising, or particularly indicative of anything except uncertainty. At this stage of the run the divergence between the various different runs means that you'd expect the mean height chart to become more diluted and trend towards the seasonal average. However, looking at the NAEFS anomaly chart there's still a signal, albeit weakly, for higher heights over the Arctic and for a chunk of the vortex to be displaced to Siberia:

It does also point towards low pressure in the Atlantic, which also doesn't seem too surprising as even some of the colder scenarios would have low pressure to the west (albeit centred further south than on this chart), but as for the vortex it doesn't look like a particularly strong signal either way. 

Edited November 9, 2014 by LomondSnowstorm

[Cloud 10]

Good post Steve

The PRHW is the new gfs

I want to know what the PRX is?

At day 10 it is also level pegging with the ECM

Anyone know. Can't find anything via google.

 

Plenty mention of PRX on this gfs parallel page,so maybe the PRX is actually the final "build" of the new GFS.?

 

http://www.emc.ncep.noaa.gov/gmb/para/parahome.html

[bluearmy]

Plenty mention of PRX on this gfs parallel page,so maybe the PRX is actually the final "build" of the new GFS.?

 

http://www.emc.ncep.noaa.gov/gmb/para/parahome.html

That's an old page cloud - 2005. !

PRX must be something to do with parallel but what ? Perhaps the new GEFS?

[Cloud 10]

That's an old page cloud - 2005. !

PRX must be something to do with parallel but what ? Perhaps the new GEFS?

 

Yes,quite  old  but they seem to use the same codes over the years.

 

Impressive stats if it is the new gefs,although more likely to be on the ensemble verification page?

[snowking]

There is discussion of the PRX here:

http://www.americanwx.com/bb/index.php/topic/44784-t1534-gfs-gfs-at-13km-along-with-other-upgrades-can-be-found-here

Haven't got time to discuss in detail but in short it is another parallel run initialised by NCO on a semi-lagrangian grid at 13km forming part of the 30 day evaluation period

Should essentially be same as current GFS(p) with a few tweaks

SK

Edited November 9, 2014 by snowking

[Robbie Garrett]

GFS is flirting with history. Take a look at this, obviously the dates are different but only by a few days.  Actually looking at a the synoptic in the future we are in quite a position moving forward.   I seem to remember 2010 was pure synoptic.     I actually think the Jetstream over the UK and western Europe is in quite a good position to allow the building of heights over Scandinavia and Greenland.    If the low to our south west is to further dig southeast, then we are surely in a good position synopticallly for the end of November 2014?

 

I expect downgrades, and upgrades if there's any fruition of a cold spell. It's just remarkable how the models are counting down to an event like November 2010.  Not saying they two will be the same, just how similar the models are behaving before a possible event.

 

2010 - 78hrs away

 

 

2014 - 78hrs away

 

 

 

2010 -120hrs away

 

 

 

2014 -120hrs away

 

 

 

Here's the NCEP clearing showing heights to our north, northeast.

 

Edited November 9, 2014 by Robbie Garrett

[bobbydog]

Excellent post steve. It explains your "crudely put" comments last night.

Maybe your post should 'stickied' in some way as a reference to explain model bias.

You're obviously not a big fan of the GFS but it would be interesting to hear your views at some point regarding the performance of the new upgraded GFS as it has had input from the ECMWF.

If they have 'fixed' it, then theoretically it could end up being better than the ECM.

[nick sussex]

Looking at the ECM ensembles in terms of wind direction theres a good cluster which move the wind towards the east. Now because of the set up you can draw the conclusion that for this to happen these deliver sufficient trough disruption to allow some lower heights into central southern Europe.

 

 

At the moment however we don't see a move towards any deep cold coming from the east however I think the first hurdle is just to get the right trough disruption so that low heights to the nw are separated from troughing to the south, this then allows ridging from the east/ne to back further west.

 

That's as far as I'd look because essentially the ensembles and especially the GEFS will have vastly different solutions depending on the correct modelling of the trough disruption.

 

There are certain patterns whereby small detail doesn't impact greatly on the overall pattern, so for example northerly topplers which often end up further east, this really doesn't change the overall LW pattern, the error is small on a global scale, typical zonal patterns again it doesn't make much difference there.

 

Because of the set up the trough disruption has a huge knock on effect. To elaborate here this effects how much WAA takes place and also then dominoes as the next low moves in and disrupts, if you get the early clearance of troughing then the next low is likely to disrupt further west as the ridge would also be further west. Additionally how much energy goes ese, how far does this get into Europe, even before the main event we have some vast differences between the UKMO and ECM at T144hrs which again impact on how the troughing disrupts afterwards.

 

As for the possible reforming of the PV, I'm not convinced, lets look at this another way would we have confidence of the reverse if we were sat here looking at a PV stuck to the north which showed signs of lifting out at day 15!

 

I know I've now over done the "keep an open mind" statement but I really think we need to just be a bit patient to see what exactly happens with any trough disruption before having a more concrete idea of where the pattern might go afterwards.

Edited November 9, 2014 by nick sussex

[ukpaul]

As for the possible reforming of the PV, I'm not convinced, lets look at this another way would we have confidence of the reverse if we were sat here looking at a PV stuck to the north which showed signs of lifting out at day 15!

 

Even if it does, the warming we are seeing emerge in the strat in the next week or two will put further pressure on it. Just in time for mid December!

 

Cohen (via Snowking on the strat thread)

 

"Given the predicted already weakened state of the stratospheric polar vortex, we are monitoring closely a possible early weakening of the stratospheric polar vortex. The response in the troposphere following the stratospheric warming event is a more negative AO state, which is typically experienced about a week after the warming event and can persist for several weeks thereafter. This should promote colder temperatures across northern Eurasia and probably the Central and Southeastern US by mid-December."

[SMU]

Yes - ^^^

 

The ECM is depicting a Wave 2 tropospheric wave breaking event with a significant warming allowing a strong negative index at 70N.....

 

GFS & UKMO only have wave 1.

 

S
 

[snowking]

Even if it does, the warming we are seeing emerge in the strat in the next week or two will put further pressure on it. Just in time for mid December!

 

Cohen (via Snowking on the strat thread)

 

"Given the predicted already weakened state of the stratospheric polar vortex, we are monitoring closely a possible early weakening of the stratospheric polar vortex. The response in the troposphere following the stratospheric warming event is a more negative AO state, which is typically experienced about a week after the warming event and can persist for several weeks thereafter. This should promote colder temperatures across northern Eurasia and probably the Central and Southeastern US by mid-December."

 

 

It think it is worth picking up on this point over here, just incase some do not venture over to the stratosphere thread (it is understandable - I can imagine it may be a little daunting at times especially for newer members)

 

Whilst we have experienced a high SAI this year, in fact the highest on record (though this only stretches back as far as 1998), high SAI years do not tend to favour a cold first half to the winter for Western Europe. Occasionally this may happen as a consequence of the strengthening Siberian high nudging slowly Westwards, but it is not the most common of occurrences for us here in the UK.

 

However, what seems to be apparent this year is that the 'normal' timeline of events - i.e. the Scandi high/Aleutian low combo, and consequential wave breaking in to the Stratosphere is happening a little quicker than usual. Remember the mentioning of the failed Dec '12 Easterly, well this year that potential (or potentially failed) Easterly looks to be happening towards mid-November instead.

 

You may remember from 2012 that we saw a period of a return to Neutral/Positive AO before the Negative AO returned towards January. You may also have noticed in recent days many of the more seasoned members have been trying to temper expectations a little. The two are not mutually exclusive events. As Cohen has put it in his recent blog entry for this year:

 

 

 

Although the AO will be in a negative state in week 2, it will likely transition to neutral or even positive...

 

(I have omitted the final part of that quote so as to avoid an outbreak of mass hysteria in here)

 

So as per Nick Sussex's excellent assessment above, yes there is a possibility of (perhaps even a likelihood of) a return to less negative AO conditions. However, I would also add that any calls from current GEFS runs that we will be seeing a return to any sort of intense vortex in the next couple of weeks look very wide of the mark.

 

Just taking a look at the panels from the 6z:

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=384

 

We have perhaps two out of 20 members suggesting anything nearing a 'traditional' (perhaps should read 90/00's) polar vortex - and I would put that down to the standard variability we have come to expect from the GEFS at such range.

 

So I think the point to take from all of this is that yes there is a chance of something cooler towards the middle of this month, equally should it not come to fruition do not become disheartened, and as we see an almost inevitable return towards a more neutral AO later this month bear in mind this is an expected development. Hopefully by this time we will all be a little more distracted by activity way above our heads up in to the stratosphere.

 

SK

Edited November 9, 2014 by snowking

[bobbydog]

Yes - ^^^

 

The ECM is depicting a Wave 2 tropospheric wave breaking event with a significant warming allowing a strong negative index at 70N.....

 

GFS & UKMO only have wave 1.

 

S

Without trying to over-simplify it, are we seeing such large differences between the models due to the ECM incorporating the strat forecast whereas the other 'big two' are not (or at least taking much less account of it)

[bluearmy]

Without trying to over-simplify it, are we seeing such large differences between the models due to the ECM incorporating the strat forecast whereas the other 'big two' are not (or at least taking much less account of it)

All op models have their tops at the highest level of the strat, BD. The ECM does have more horizontal levels up there but the gfs op strat forecasts seem pretty good to me so in not sure that the differences in the trop are down to this, the gefs do not top out as high as the ECM ens so there could be an argument that the ECM ens could be more reliable when there is activity at the top of the strat which is downwelling.

[bobbydog]

All op models have their tops at the highest level of the strat, BD. The ECM does have more horizontal levels up there but the gfs op strat forecasts seem pretty good to me so in not sure that the differences in the trop are down to this, the gefs do not top out as high as the ECM ens so there could be an argument that the ECM ens could be more reliable when there is activity at the top of the strat which is downwelling.

Thanks BA, So maybe in situations involving strat warming, the ECM has the edge over the other models which have to 'play catch-up' once their data feeds into the trop models

[Swave Snow]

GFS is flirting with history. Take a look at this, obviously the dates are different but only by a few days.  Actually looking at a the synoptic in the future we are in quite a position moving forward.   I seem to remember 2010 was pure synoptic.     I actually think the Jetstream over the UK and western Europe is in quite a good position to allow the building of heights over Scandinavia and Greenland.    If the low to our south west is to further dig southeast, then we are surely in a good position synopticallly for the end of November 2014?

 

I expect downgrades, and upgrades if there's any fruition of a cold spell. It's just remarkable how the models are counting down to an event like November 2010.  Not saying they two will be the same, just how similar the models are behaving before a possible event.

 

2010 - 78hrs away

 

 

2014 - 78hrs away

 

 

 

2010 -120hrs away

 

 

 

2014 -120hrs away

 

 

 

Here's the NCEP clearing showing heights to our north, northeast.

 

 

 

 

Great Post,

 

I am intrigued to know if the NWP in 2010 were indeed forecasting the spell that eventually came in November 2010 as I remember many poster on two forums discussing the persistence in the NWP.   However something that was certainly present back then was (and I think it was later in the month) agreement being rock solid among the models.  Granted we are still early on at the moment and things could certainly firm up in terms of a cold scenario.  I must admit some of the Charts in respect of the heights being shown at the present time are quite remarkable to say the least and may bode well in the next few months.

 

I would be very appreciative if any one knows what the Met Office was saying back then and if at all they were saying the same thing as they are now ie that the y think on the probabulity of averages that November-December-January being above average temperature wise because of low pressure being more prominent to our south west than normal?

 

If it turn out that they (the Met Office) at this early juncture were also saying similar things in November 2010 to what they are saying now, then I feel we are in a fighting chance that the NWP starting with the ECM could be brewing something special for our part of the world.

 

Last thing does anyone remember what the temps were like back in 2010 at the same time as now in the regions like East Europe and Russia?

[blizzard81]

The updated cpc ensemble means for the AO and NAO are much better than I was expecting going into the

second half of Nov, especially the NAO which shows a clear trend to negative over the next couple of weeks.

[bluearmy]

Bobby dog - At the outset of a top down strat warming, yes. At the moment we have the warming showing below 5hpa so the gefs should be doing a decent job. However, if there is a renewed warming at the very top, the gefs won't see it but any trop response would be well out sight of the modelling that ends at day 15. therefore, it's not really a factor on the two week models.

Edited November 9, 2014 by bluearmy

[Bobby]

The D16 from the GFS parallel highlights the trend that has been showing in the GEFS for a much more organised PV:

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=204&code=code&mode=0&mode3h=0&runpara=1&carte=1&runpara=1

It may all change but there is a clear signal.

 

NAEFS and GEM means are picking up on that too. Worth keeping an eye on

 

 

[bluearmy]

They both show a split vortex with the Asian parent. remember these are day 14 day charts. rare to see definitive features at this range. You need to view these I tandem with the spreads to see where the blues are (this indicates some confidence as to the heights shown)

[shaky]

The updated cpc ensemble means for the AO and NAO are much better than I was expecting going into the

second half of Nov, especially the NAO which shows a clear trend to negative over the next couple of weeks.

definately mate!!am sort of surprised to see the nao and ao that negative aswell!!its a better update than yesterday's!!I think come this evening if we don't progress from last night's 12zs regarding heights around greenland and the pattern backing west then that will probably be that for any chances of getting cold into the uk before december!!just my opinion but I could be wrong!!

[Purga]

Apart from a couple of odd cold runs the ENS concensus is for above average and unsettled conditions to perpetuate for the foreseeable future

We could scrape the odd ground frost if we're lucky and pressure seems to be rising through the medium term.

Edited November 9, 2014 by Purga

[blizzard81]

definately mate!!am sort of surprised to see the nao and ao that negative aswell!!its a better update than yesterday's!!I think come this evening if we don't progress from last night's 12zs regarding heights around greenland and the pattern backing west then that will probably be that for any chances of getting cold into the uk before december!!just my opinion but I could be wrong!!

I totally agree. What I have noticed about the best cold spells in recent years is once the models pick up major blocking

patterns - much like the ECM at present, they tend to increase in intensity with each run. That's when I know something interesting

is around the corner and that is what I am looking for over the next couple of days - cmon winter 14/15 

[Altohumorous]

I would say that comparisons are as odious as statistics but............................Last year I was speculating about whether the current 'cold' period in the cycle of sun activity would follow any sort of similar trend in terms of how the winters pan out during the 'period' in comparison to previous 'cold periods'. So I looked at alot of charts and stats for how the weather and synoptics were for winters in the late 70s & early 80s, and also in the late 50s and early 60s.

 

If I thought I noticed anything at all interms of pattern, I speculated as to whether the last two winters, following on the 'cold' winters (in this region of the world) prior to it, had any echoes in the past, and felt that it was just possible that the late 70s & early 80s might contain something. Hence the winters of 2009-2013/14 were not entirely dissimilar to those of about 1977/78-1981/2 or maybe 83.

 

Furthermore I can see similarities between the past two winters and the current synoptics and the winters of the mid-1960s (post 63). Perhaps all it shows is that northern blocking/PV disruption, and also Jet emigration, occur much more during these periods. Big swing you may say and rightly so. But it's interesting nonetheless to speculate about.

There were winters in the mid 1960s that had fantastic 'potential' (for cold-weather set-up & unusual synoptic lovers) but which didn't lead to anything more than a few cold snaps (significant though some of those were) in these islands.

And of course it goes without saying that the complexities & infinite possibilities overall of the atmosphere preclude anything in any great detail in terms of predictable larger patterns. But I'll still say that the current model output does remind me very much of winter  charts I looked at for the mid-1960s. And given that we have passed by the 'peak' of the 'cold cycle' of atmospheric patterns for this round, I think it's unlikely we will see any prolonged cold in winter in the next couple of years. Perhaps overall a sign of the changing climate, given that the two very cold spells that did occur in this cycle did not persist as long as the coldest winters of the previous cycles.

But the beauty of it all is, nobody knows and these current outputs certainly raise great interest and speculation even in the short term. Looking forward very much to see how the next 4 weeks at least pan out. I think if we get even what is indicated in the next 10 days by the models it will have been quite unusual

[bobbydog]

Those touting a strengthening vortex would do well to pop into the strat thread and read Snowking's excellent post.

Basically there are expectations of an early season SSW during which time the AO would likely go positive. As he says, panic will ensue and "winters over" posts will be flying around. I would assume the vortex would appear to reform.

However,after this event (should it happen) the AO would go deeply negative and potentially last for several weeks.

Then we're in business...

[Polar Maritime]

Can we please stick to discussing what the Model Outputs are showing. As interesting as some recent posts are, And without sounding like a kill-joy.. They are bordering being moved into the Winter thread.

 

Thanks, PM. 

Edited November 9, 2014 by Polar Maritime