Model Output Discussion: 12Z (20/11/12) And On...

[Methuselah]

Here goes: a nice, new shiny thread...

Old one:

Edited November 20, 2012 by Rybris Ponce

[Cheshire Freeze]

Well the 12z evolution has a tinge of 62/63 about it; WAA bursts allowing HP to fluctuate in a spectrum between Scandi and Greenland. Not for one minute saying we'll experience anything near the 62/63 standard over the next few weeks but just noting that alternating Greenland/Scandi blocking was a theme throughout that winter.

[mattke]

Snow next Tuesday anyone?

[Ian Brown]

Just a quickie as stille at work - basically the models are not going to have a clue about handling HP in the Svalbard area, so it's best to concentrate on this side of T192 rather than get excited or depressed about what the GFS shows beyond it.

[Cheshire Freeze]

Just a quickie as stille at work - basically the models are not going to have a clue about handling HP in the Svalbard area, so it's best to concentrate on this side of T192 rather than get excited or depressed about what the GFS shows beyond it.

Did I really just 'like' an Ian Brown quote?!

[johnholmes]

GFS seems to be showing signs of actually believing the anomaly charts at last. Just how cold the first thrust from the NW will be is not clear yet. The anomaly charts all show the flow turning N-NE with a marked upper low just ESE of the UK and the ridge holding N-NW of the country, so it is looking at the moment not to be a dry high. How wintry is again not clear but if the cold persists for 5-8 days as it looks like doing, possibly longer, then increasingly wintry with the eastern side of the UK more favoured for that. There will be numerous ups and downs on the synoptic models along the way. I would expect from studying the various contributory factors that at some point the ridge will link pretty much across the north from NW-NE. Maybe 10-14 days is possible for a quite cold spell?

regarding something from the sky. Remember how poor the models can be at predicting where rain will fall and how much and when over the summer period less than 24 hours ahead? Today is a case in point for this area. Even allowing fro the rain shadow, the rain has been noticeably absent in fact rather than the forecast.Then be VERY careful looking at charts that appear to predict the white stuff for you beyond about 12 hours!

Edited November 20, 2012 by johnholmes

[Isolated Frost]

Today's 12z GFS n-hemi forecast for 27th 12z on the top.

Yesterday's 12z GFS n-hemi forecast for 27th 12z on the bottom.

Not only do we see a solid surface ridge building in the Arctic Circle on today's, compared to a more active surface low and prominent vortex in the Arctic on yesterday's 12z.

The American profile is changeable as well. The Pacific ridge builds into the Aleutian/Alaskan area today, whilst it strays back yesterday, limiting the disruption to the arctic pattern. The way it builds today leads to a high pressure cell o/ Svalbard- very encouraging for a widely conductive cross-polar flow.

The look of that GFS 0z (12z data not out yet) shows the broad agreement for a rise in AO- though the movement is stable up to D8. The 12z introduces that high pressure, so perhaps FI will look different on the 12z, in terms of AO movement.

I'm very much a fan of the ECMWF data more so than the GFS.

0z ECM and GFS height anomalies. I can only take from that a view at the Arctic. You can all see for yourselves the disagreement that remains still...

[The PIT]

Funny how the 00 oz and 12 oz have different views on the temps. 12oz seems to be constantly on the cooler side. Anyway a wee bit of a blow on Thursday with some gusty winds around. After that the next point of interest is the slight risk of some white stuff in FI from T111 onwards.

[The Eagle]

12 GEM flatter than the 00z. Could go anywhere at 144hrs.

[swfc]

12 GEM flatter than the 00z. Could go anywhere at 144hrs.

indeed.its also froze at 144 0n metiociel???

[Altohumorous]

With regard to the chances of severe cold around these shores, and those who like to see it happen, it's worth noting how the expectations of people looking at model output has changed since Dec 2009! Back then most were just hopeful that something, anything would happen, even for a few days. The rest is history.

Although I still enjoy looking at the forecast models I find it much better to leave the predicting/interpreting to those who have proven themselves to know about it. And I maintain the same perspective as three years ago, hopeful for anything, enjoying the fact that we had some seasonal weather so far this autumn, the fact that it is still very early days with the whole winter still spread out before us, and therefore lots of time for interesting/unusual things to happen.

And if anything really interesting DOES happen, it's very much bonus territory. The reason I'm posting this is that I've discovered this approach is alot less stressful or disappointment-provoking than the way it used to be for me.

You could compare it to following football teams - for the vast majority of supporters, their team will only win something or achieve something like promotion very occasionally. To be constantly hanging on tenterhooks hoping desperately that "this will be the year" for nearly every game is no doubt very exciting, but mentally and emotionally not very good for you.

I suppose you could also describe it in terms of addiction!

So by all accounts here's just looking forward very much to the models showing us something colder coming right in time for the very start of meteo winter, within the reliable range, and the potential for something a bit more than that - how good is that? Especially when you consider the many years that went before 2008ish where so little was on offer, and the patterns/model predictions were, well, oh so predictable.

Just a comment on previous charts/models during previous cold spells, I was looking again recently and it's amazing how much the mind/memory can play tricks, especially the further away it is. How often has it been said that "winter 78/79" and "december/jan 1981/82" were somehow unbroken cold spells with ideal synoptics that we can only dream of?

O contraire mes amis! In December 1978, and again in 1981, there was not, in fact a seamless run of perfect charts, though they were certainly good enough to have brought some significant snow at times (still only about 3 significant falls at most where I am). But at times the pattern over west Europe at least had temporary breakdowns, with short milder spells that would have some people on this forum going beserk with horror and predictions of doom for winter.

I'm also wary enough to recall that in december 2008 (I think?) there was an intense scandi high that extended towards us for lenghty periods, but produced no severe cold due exact positioning & to a lack of NW area block to loink with it/of very cold air being advected towards us.

Looking at the current model output all we can say really is that there is a strong trend for a week at least now for northern blocking and colder weather for these islands, possibly an easterly/northeasterly at first in any event, which is something that there has been little enough of even in the very cold spells of 09 and 10.

Edited November 20, 2012 by Altohumorous

[AWD]

12 GEM flatter than the 00z. Could go anywhere at 144hrs.

Whilst its not flat as such, it's not as amplified as the GFS & doesn't send any WAA up towards Greenland, instead keeping the HP much nearer to the UK;

http://www.meteociel.fr/modeles/geme_cartes.php?ech=144&code=0&mode=0&carte=1&archive=0

Looking at that, it looks as though its going to send the HP over the top of the UK & maybe into Scandinavia however.

[bluearmy]

indeed.its also froze at 144 0n metiociel???

not frozen - the 12z run only goes to T144

[swfc]

not frozen - the 12z run only goes to T144

thanks,ill get my coat .Does indeed look less amplified and heading towards a mid latt position

[Zenarcher]

Some good changes in both the GFS and ECM over the past 24 hours,

ECM for the 27th today's shows better heights to our North.

Yesterday

Today

GFS for the 26th today's also better PV weaker and the low yesterday to the East of Greenland was at 995mb now its been replace with a 1035mb high all in just 24 hours,

Yesterday

Today

[Glacier Point]

Definate 'low resolution' issue with the GEFS.

At t180 we have reasonably tight cluster around a ridge solution centred around Iceland. Through t192-204 that drops out significantly and a lot of spreads suddently develop. Don't think that's related to a synoptic evolution, more inability to deal with the dynamical processes going on.

[Cheshire Freeze]

GEM at 144 is grim viewing!

[weather eater]

Definate 'low resolution' issue with the GEFS.

At t180 we have reasonably tight cluster around a ridge solution centred around Iceland. Through t192-204 that drops out significantly and a lot of spreads suddently develop. Don't think that's related to a synoptic evolution, more inability to deal with the dynamical processes going on.

I think that’s got to be pretty much the truth of it, we know that the GFS from the mid range is going to give over the course of several runs a fair splattering of solutions, but in the past few days we have seen a bewildering array of evolutions offered by this model, that can only be down to its ability to deal with the background signals.

Edited November 20, 2012 by weather eater

[Liam J]

GEM at 144 is grim viewing!

Some very underwhelming charts from the 12z's..... For what it's worth the NOGAPS @ T144, remarkably similar to the GEM....

Over to you ECM.....

Edited November 20, 2012 by Liam J

[Cheshire Freeze]

Some very underwhelming charts from the 12z's..... For what it's worth the NOGAPS @ T144, remarkably similar to the GEM....

Over to you ECM.....

Yes the GFS looks out on its own at the minute with its much more amplified pattern! Hope we're not going to be left deflated and let down after all this.

[snowking]

Some very underwhelming charts from the 12z's..... For what it's worth the NOGAPS @ T144, remarkably similar to the GEM....

Over to you ECM.....

Good job then that the 12z's verify 500mb heights @ Day 6 as follows (and trust me, theres a bit of a surprise in the offing here):

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day6_HGT_P500_G2NHX_12Z.png

1. ECMWF

2. GFS

3. JMA <<<<< (spotted the surprise? Ian has mentioned the thoughts of MO regarding this previously)

4. UKMO

5. GEM

6. NOGAPS

SK

[bluearmy]

Definate 'low resolution' issue with the GEFS.

At t180 we have reasonably tight cluster around a ridge solution centred around Iceland. Through t192-204 that drops out significantly and a lot of spreads suddently develop. Don't think that's related to a synoptic evolution, more inability to deal with the dynamical processes going on.

tbh, the gefs recently have worried me in fi with a lack of clustered solutions. the pattern change across the arctic has them confused. given that the ecm ens beyond day 10 are running at even lower resolution than gefs and maybe you can undetstand exeter's nervousness. it worries me as the gefs mean is directly fed into naefs and all the mean data is used by noaa cpc. the extended charts arent just a guess ! maybe this is indeed a time for analogues and teleconnections re the MJO, GWO etc.

btw, no surprise re JMA, i always look at it although it only runs once a day which is a shame.

Edited November 20, 2012 by bluearmy

[AWD]

FWIW, the GFS Ensembles;

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=306&y=141&ville=Londres

More milder members than in previous ensemble runs. Uncertainty continues.

[SMU]

Are we really favouring the Schmuck NOGAPS & GEM over the UKMO 12z & ECM 00z...

Excellent UKMO tonight-

expect big things from the ECM shortly-

S

[fergieweather]

We have enough problems looming in the next 12-48hrs without even pondering the longer term... 4KM modelled rainfall totals are troubling and we're also now changing warning emphasis to highlight strong pre-frontal winds Thurs; widely to 50kts inland with 60-65kts western exposures ahead of v squally frontal progression later that eve.