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Model Output Discussion - The Run In To Christmas


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So then anyone know which models they use to make these forecasts (Accuweather) for some reason something in the back of my mind makes me think someone mentioned GFS?

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Unfortunately, there needs to be a recognition that if we share at *this tentative juncture* the exact nature of what we have as Ops Centre guidance, certain individuals will inevitably extrapolate/wa

If the UK can't get cold from an upstream pattern with a negatively tilted troughing setting up over the ne USA , indeed the best set up since two winters ago then I will seriously consider throwing m

The good news just keeps on coming!   Upstream pattern is falling into place to deliver what many people in this thread want to see, NCEP give us the best update since winter 2012/2013,  indeed I'm

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Eye candy 18z run.

 

It's a while since I can recall such model volatility and at a time of year when so many people are weather watching. It's also curious to see forecasters ignoring the possibilities. My niece just teased me with an app screen print showing local temps in double figures so for fun I screen printed back the latest 18z. However, as to her to us all. These are confusing signals. Best wait for a couple more days and see if the ensembles tighten and the operationals conform.

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Consistent theme of an spiral quite angry LP system spawning in Atlantic, then transferring directly over Southern England snow to the northern flank then treading east over Holland and to the western flank colder uppers undercut? and snow for those down south :w00t: with that high winds.

I'll be watching how this develops. If i'm totally off please do enlighten me.

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It's not so much a case of it hitting low resolution, so much as it's a case of, once again, as we move the timeframe closer to T+0, it seems that the operational models are leaving more and more energy around the Greenland locale (especially to the North) - or to put it more accurately, it's starting to look as though once again (for about the 10th time in the last 3 years or so) the models may have overestimated heights in this area.

 

We can see this from the last few GFS and ECMWF runs (the ECMWF has been particularly guilty of this over the past few years as has been pointed out numerous times recently).

 

gfsnh-2014121900-0-204.png?0gfsnh-2014121906-0-192.png?6gfsnh-2014121912-0-186.png?12gfsnh-0-180.png?18

 

ECMWF:

 

ECH1-240.GIF?12ECH1-216.GIF?12ECH1-192.GIF?19-0

 

This has been such a consistent occurrence in the last few years that it has made me strongly distrustful of the ECMWF in particular (as this seems most prone to incorrectly evacuating low heights from Greenland in the extended timeframe).

 

This does not entirely preclude a colder spell in the shorter term, but any such spell is likely to be a little more short lived in nature than perhaps was initially suggested (assuming of course that this trend continues to keep a larger area of lower heights close to Greenland).

 

Of course what happens beyond the xmas - new year period is still very much open to debate, but right now the model trends seem a little too familiar for me in the shorter term. Let's hope for something a little more positive the other side of the weekend.

 

SK

Edited by snowking
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Looks like we're not getting a mean for the 18Z Ens at present, so it's a case of clicking on the individual members to see what they're showing.

 

For newbies, click on Pertubation/Disturbances...1,2,3 etc

 

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

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The big difference in the 18z is that the Greenland high is a blink and you miss it affair hence the cold outbreak is very short lived and we get an Atlantic flow pretty quickly while the 12z had a long lasting northerly.

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Well in fairness its not consistent as in the 12z it was over Shetland.

 

Yet it did have some backing from the ECM though albeit earlier in the run, see below.

 

https://forum.netweather.tv/topic/82046-model-output-discussion-the-run-in-to-christmas/?p=3092205

 

Something much cooler could definitely develop post Christmas around the 27th and 28th December for sure, but with today being the 19th I'd rather check the Daily Excess for a story about it rather than put too emphasis on things at that range. Get the cold Northerly/Easterly trend to remain in place come Monday, then it may well be a snowy Merry post Christmas for a few in the SE and who knows where else.

 

Night night.  :friends:

Edited by gottolovethisweather
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Looks like we're not getting a mean for the 18Z Ens at present, so it's a case of clicking on the individual members to see what they're showing.

 

For newbies, click on Pertubation/Disturbances...1,2,3 etc

 

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

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=288

This is easier SEB. Adjust the timescale at the top.

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Well, we must be in for some colder weather as no one is desperate enough to post any CMA, NOGAPS or GEM charts.

The fact that GFS ops coupled with extended ECM ensembles persistently showing much colder and potentially

snowy synoptics should fill us with greater confidence as we head towards year end :smiliz19:

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http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=288

This is easier SEB. Adjust the timescale at the top.

 

Oh, silly me, of course it is. Thanks BA.

 

It's getting late, and it's been a long day....

 

ECM Ens are out for London, and yet again the Op was out of kilter with most of its members at Days 9/10...

 

ensemble-tt6-london.gif

 

The ECM op needs to get into the Christmas spirit pronto! 

Edited by SE Blizzards
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The Christmas Eve fax is out and it follows it's raw output-allow for the different orientation of the charts.

 

attachicon.giffax120s.gifattachicon.gifUW120-21.gifattachicon.gifUW120-7.gif

 

the cold air back in place after the 2 day milder spell on Sunday and Monday.

All eyes to the south west for a wave development running along the jet after Boxing day.

The track and depth will dictate where snow may fall as it comes against the cold air.Strong winds or gales also likely for a short while as it comes through.

That looks like a very nice seasonal chart for xmas eve. Lets just see how we progress from there.

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Oh, silly me, of course it is. Thanks BA.

 

It's getting late, and it's been a long day....

 

ECM Ens are out for London, and yet again the Op was out of kilter with most of its members...

 

ensemble-tt6-london.gif

 

The ECM op needs to get into the Christmas spirit pronto! 

What on earth is the control run doing from the 27th with those straight lines? Something really is not right with the ECM right now. The OP is perhaps not a strict outlier in my opinion but right at the top end (warm end) of its members. Quite a bit of spread around then with more members then going for cold but by all means is there full consensus on this one. Going to be Monday/Tuesday possibly even Christmas Eve before any real confidence on next weekend I feel.

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What on earth is the control run doing from the 27th with those straight lines?

 

 

I think the Blue line is the GFS 12Z op run, is it not?

 

Perhaps someone else can confirm this.

 

Edit: 18Z Ens look fairly decent at 192.

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=192

Edited by SE Blizzards
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What on earth is the control run doing from the 27th with those straight lines? Something really is not right with the ECM right now. The OP is perhaps not a strict outlier in my opinion but right at the top end (warm end) of its members. Quite a bit of spread around then with more members then going for cold but by all means is there full consensus on this one. Going to be Monday/Tuesday possibly even Christmas Eve before any real confidence on next weekend I feel.

That is the NCEP, or GFS output not the ECM control, temperature wise the ECM control was similar to the operational.

The output looks a mess,  subtle differences between the models at day 6, but this determines the output further on.

GFS

gfs-0-138.png?18

Closed low in the Atlantic with high pressure established north of this. We get a northerly though is is extinguished (typically) in low resolution.

ECM

ECM1-144.GIF?19-0

Already developing a trough to the south of Greenland, this will push cold air southwards, nearest area to phase is the Atlantic low, at this point its game over.

UKMO

UW144-21.GIF?19-18

It also has that trough developing, but the low is closed off unlike the ECM. It could go either way.

GEM

gem-0-144.png?12

Unlike all the other output.

 

In the end you don't want cold air digging south from Greenland as your first weakness is that Atlantic low unless you cut it off fully (unlikely). So we need this cold arctic air either pushing south at a more easterly longitude or the cold air pushing in a more south-easterly direction and hence the cold air pushes towards the UK (AKA GFS).

As I said earlier, we can't discount the ECM given it's milder evolution is set well on course at 6 days out. Lets hope it changes tomorrow.

Also it is rather amusing that the GFS was binned this morning, but now is being used as evidence for a cold spell whilst the ECM has gone from hero to the trash bin. At this stage we can't discount anything. We could end up in the freezer or in a blowtorch come next week. We will have to wait and see what will happen.*

*Note in-between scenarios (AKA every other possible solution under the sun) are also possible at the moment :p

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I think the Blue line is the GFS 12Z op run, is it not?

 

Perhaps someone else can confirm this.

 

Edit: 18Z Ens look fairly decent at 192.

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=192

 

I computed manually the average/spread for the GEFS 18z, now they're available from +180h (I will redo all from +0 once the run is finished)

 

And yes the blue line is supposed to be the 12Z GFS run but there were data issue today, so who knows :)

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If the darker blue (neg) anomalies were more towards the West side (Ali G) of the UK then I'd be happier. We need the squeeze of those anomalies running through the mid atlantic ridge  (albeit that's underwater) i.e. through Iceland, tighter both sides. Definitely going the right way, though.

Edited by kumquat
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ECM mean looks more like the GFS/GFS P at day 8. Expect a backtrack from the ECM in the morning.

 

That's a pretty brave call there Barry, but i must say i'm kinda with you on that one.

 

However, 'IF' the ECM continues on it's scrooge ways on both it's runs tomorrow i really will have to start thinking it's called this one correctly.

 

More fun and games to come tomorrow no doubt.

Edited by SE Blizzards
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ECM London ensembles.

 

ensemble-tt6-london.gif

 

control goes into deep freeze after a brief warm up.

 

I know GFS ensembles are showing a toppler and fairly short lived cold spell but as I have said previously, any modeling that shows a remotely organised PV into January needs to be treated with suspicion.

IF we get a good start and decent amplification and strong Atlantic ridge I think we will quickly see the length and severity of the cold being upgraded across GFS ensembles.

The scenario they show with the PV moving back West and reorganising is unlikely given the strat warming and likelihood of an Atlantic and EPO ridge. Far more likely will b a split with the dominant half of the PV setting up home to the East.

 

My concern is only that we get a good start rather than the halfhearted ECM attempt.

I really think we are on the verge of something special developing in January but want to see ECM get fully on board with the initial cold spell first.

Edited by Mucka
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