Model Output Discussion 1200 hrs 15/11/14

[nick sussex]

I've decided to stop being so grumpy and am going to be Mr Positive.

 

Whilst the ECM isn't the most exciting of runs it at least keeps low heights in the Med , it also eventually cuts off the milder feed into mainland Europe, and a small cold pool does actually work westwards.

 

Also it looks drier and cooler than of late so although not really what we wanted to see in terms of wintry potential it could be worse.

 

Although the models do now agree on the phasing upstream over in the ne USA  and deep low running ne there is still some uncertainty as to events over there right upto next weekend. This will have knock on effects on trough disruption near the UK.

 

Heres the NCEP comments from earlier, at this point uncertainty is good because the GFS and GFS P are really very disappointing:

 

...OVERVIEW...

THE PASSAGE OF TIME IS DOING REMARKABLY LITTLE TO RESOLVE THE AREA
OF SIGNIFICANT SPREAD THAT GUIDANCE HAS PERSISTENTLY BEEN SHOWING
OVER THE NWRN CONUS/SWRN CANADA AS OF EARLY DAY 3 WED WITH
DOWNSTREAM IMPACTS ON THE MID LVL ENERGY/SFC SYSTEM TRACKING INTO
THE GRTLKS AND SYSTEM THAT MAY TRACK NEAR THE EAST COAST EARLY IN
THE PERIOD.  SOME ASPECTS OF UPSTREAM ERN PAC FLOW ALSO CHANGE
FROM DAY TO DAY WITH CONSIDERABLE MODEL/ENSEMBLE SPREAD AS WELL.
A GENERAL EVOLUTION TOWARD LOWER AMPLITUDE MEAN FLOW ACROSS THE
LOWER 48 BY NEXT WEEKEND MAY FURTHER REDUCE PREDICTABILITY... SO
NEEDLESS TO SAY THE CONFIDENCE IN A SPECIFIC SOLN IS BELOW AVG.

 

The full discussion can be found here:

 

http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html
 

Edited November 23, 2014 by nick sussex

[blizzard81]

I quite like the ECM tonight. It should bring some nice seasonal weather with frost and fog - always a good precursor to a cold outbreak. I still think the 120 to 144hr time period has some resolving to do. This applies to all the models as I don't believe any of them will have the south east diving atlantic trough modelled correctly. They will not get to grips with the track of this low until it comes in to the 72 to 96hr range. We can see by the JMA and GEM just how negative this low tilts can have major ramifications thereafter.

[OldMetMan]

I've been following model developments these past few days and it has been interesting to see the presence of blocking HP to our NE quite regularly run to run.

 

Although the GFS, in longer term, is being relentlessly mobile, as it often is, we are still seeing repeated trough disruption over or to the W of us, as has been happening and as is being shown to continue for a while yet.

 

The N hemisphere 500mb "shape" doesn't look particularly amplified at present, but there is still the rather weak Rex block over N Russia, which has been quite persistent - hence the trough disruption.

 

It looks to me that we will see a large, slow-moving vortex to the W and SW before long, which might enable a more pronounced upper ridge downstream. I think in 2 or 3 weeks would could be looking at a very different overall pattern, with the Atlantic mobility heading SE into the Med, and significant HP to the NE pulling in some real coldness. I just have a feeling about this - not exactly scientific!

[ANYWEATHER]

What a difference 24 hours makes! Looks as though the models are showing some settled conditions in the medium to later stages of there runs. I really don't understand the swift turn around from the models so quickly from yesterday. I will have to say little confidence past a few days, Ive been model watching for a good few years now and there has been many times of poor output, but this takes the biscuit!      

[Eugene]

I quite like the ECM tonight. It should bring some nice seasonal weather with frost and fog - always a good precursor to a cold outbreak. I still think the 120 to 144hr time period has some resolving to do. This applies to all the models as I don't believe any of them will have the south east diving atlantic trough modelled correctly. They will not get to grips with the track of this low until it comes in to the 72 to 96hr range. We can see by the JMA and GEM just how negative this low tilts can have major ramifications thereafter.

 

Yes those toasty 850's don't fool me either, would be as you say frosty with the risk of fog, deep cold is extremely rare this early anyway, may as well have faux cold for now and save the deep cold for late December onwards when it's of some use.

[summer blizzard]

More high pressure in FI from the GFS..

 

[nick sussex]

In terms of the ECM postage stamps and the all important troughing in terms of tilt at T120hrs:

 

 

You can see the range of options there, a mix really of positive ,a decent amount have at worse neutral and some negative ones aswell.

 

Just to clarify for newer members:

 

Positive- troughing running more ne/sw

 

Neutral- north/south

 

Negative- nw/se

 

You'll see from the JMA it has a negative tilt, the ECM operational positive.

Edited November 23, 2014 by nick sussex

[Captain Shortwave]

Out to day 10 and the ECM ens show moderately high surface heights over the UK. Interestingly low heights remain over the Mediterranean throughout.

I think high pressure near or over the UK giving settled and chilly conditions would be a good result until we start to see the low heights over Greenland and Canada wane somewhat. 

[Nick F]

Tonights fun run is the JMA

ECM is woeful but at least the hemispheric pattern is still reasonable-

Although day 10 of the ECM op should taken with a pinch of salt, it suggests to me a lot of potential to evolve into a much more favourable position to get deep cold our way thereafter. The empirical route to me from t+240 suggests a Scandi high could develop from there, as the jet shows signs of buckling then splitting the low heights to the north and allowing the ridge over the UK to build NE. Note the WAA poleward over Eastern Siberia too, which allows an arctic high to build across the pole which will help push cold air down into NW Russia. Already there's a chilly looking easterly flow in place across the UK.

Anyway, that's FI, but feasible with the strong signal now towards mid-latitude high over the UK rather than a persistent cyclonic southwesterly or westerly flow. Full on Atlantic mobility return cancelled? Maybe!

Edited November 23, 2014 by Nick F

[bluearmy]

are we getting to the stage where all routes seem to lead to something wintry? it seems that even the runs which deliver mobility evolve into a seasonal scenario.

This may be a bit premature but I'm taken at the way many runs which seem to bring back the Atlantic big time, soon amplify (or would do if they went further) again. (Ops and ens)

[492]

UKMO T+72 has shifted the low over England around 200 miles  SW compared to the previous run. Still plenty of uncertainty even at moderate time scales.

http://www.wetterzentrale.de/pics/brack2.gif

[phil nw.]

A glance at the 12z gefs stamps at day 7 show how uncertain things are beyond a few days.

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=168

There are some real splits in the PV showing up.A lot of ridging on our side well into the polar latitudes.

The vortex looks increasingly vulnerable to further disruption as we start Winter.

[phil nw.]

ECM mean also indicating strong cross polar height anomalies.

http://www.meteociel.fr/modeles/ecmwf.php?ech=168&mode=101&map=1&type=1&archive=0

Showing through to day 10 with signs of a retreating Atlantic.

Interesting little signs tonight of maybe blocking extended towards the UK in the medium term.

[shaky]

UKMO T+72 has shifted the low over England around 200 miles  SW compared to the previous run. Still plenty of uncertainty even at moderate time scales.

http://www.wetterzentrale.de/pics/brack2.gif

was gona say the same thing mate!! Yesterday run had it east of England yet today it has it off south west England! ! Huge change at a very early timeframe!!

[Barry12]

The models this evening have been disappointing for very cold weather. But in the reliable time frame and further on, the block to our NE has actually got stronger today than it was yesterday. As OldMetMan has pointed out, this block for weeks now has not shifted at all, and every attempt the Atlantic makes to push through has inevitably failed. Also, for weeks now the models, especially the GFS has shown the block on numerous runs getting broken down as we head into the unreliable time frame, but when was the last time we didn't have a strong block to our NE in the reliable timeframe? I think the block formed at the end of October at the earliest. So that means the block for a whole month now, has repelled the Atlantic, and that's at a time when the Atlantic should have been at its strongest. I'm very confident now we will still have this block to our NE well into December. In the past month, we've had a SE flow on quite a few occasions, and it's brought fairly average temperatures to the UK. But if we get a SE flow in December, which will be inevitable at some point in my opinion, assuming we keep this block, then this will probably be cold enough for snow, even if it isn't a far fetched Easterly. Which is why having such a strong block to our NE is very encouraging.

 

Day 5 yesterday:

 

 

Day 5 today:

 

 

You can clearly see from these charts, that the block has got much stronger, and this is well in the reliable time frame from the best model at that range. You wouldn't think there would be such a massive change at just day 5, but this block just keeps on defying it's doubters, and will refuse to let the Atlantic in.

 

Even when the Atlantic does finally manage to get the block to lay down tonight, it quickly gets back up and is ready for round two against the Atlantic, and the block also extends pretty far North into the Arctic. I don't know much about the stratosphere, but I know the GFS P will be good at getting more warming in there, which can only be a good thing.

 

 

 

Just to prove this is consistent across all the big three, here are day 5 charts from the UKMO from today and yesterday, just like on the ECM the block is far stronger, if this trend continues then who knows in a weeks time the block could extend far enough West to make it into the UK, nothing this block will do will surprise me anymore!

 

Day 5 yesterday:

 

 

Day 5 today:

 

 

 

I could post about a thousand charts showing this, but I think I have made my point! So in conclusion, as the knowledgeable folk on here have already pointed out, while theirs no deep cold in sight on any of the models (which the exception of some GEM runs of course) the blocking remains, the weak Atlantic remains, the weak Polar Vortex remains, as they have done for weeks. Some of the Seasonal models have also switched to a cold winter for us now. So to be honest, with the exception of November 2010, we have not been in such a good position as we head into Winter for cold, for many many years. Of course I'm not saying this Winter couldn't turn out to be mild, but we couldn't ask for anything better in terms of the NH profile as we head into Winter. Reading some posts over on the stratosphere thread, and from reading posts on here from the likes of Steve Murr, SnowKing, Chinomaniac, I am very confident that by Christmas time we will be looking at great charts, and most of us will have already seen some snow! I am also looking forward to the Official Netweather winter forecast for later this month!

Edited November 23, 2014 by Barry95

[Captain Shortwave]

Barry95, your comparison charts are for different forecast days (Thursday and Friday), surely it's best to compare todays T96 with yesterdays T120.

Yesterdays

not much difference to be honest. We do see another pulse of WAA at the end of the week which then gets pushed eastwards but does punch into the Arctic.

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2014112318/gfsnh-0-90.png?18

 

Another tiptoe south & West for the GFS - we have gone from a strongly positive tilt yesterday on the 12z

http://modeles.meteociel.fr/modeles/gfs/archives/gfsnh-2014112212-0-108.png?12

 

to a negative one tonight--- So the GFS follows the UKMO & GEM ....

 

S

[Barry12]

Barry95, your comparison charts are for different forecast days (Thursday and Friday), surely it's best to compare todays T96 with yesterdays T120.

Yesterdays

not much difference to be honest. We do see another pulse of WAA at the end of the week which then gets pushed eastwards but does punch into the Arctic.

 

True, but on the GFS  you see that the block has moved more west today than yesterday:

 

Edited November 23, 2014 by Barry95

[blizzard81]

http://modeles.meteociel.fr/modeles/gfs/runs/2014112318/gfsnh-0-90.png?18

 

Another tiptoe south & West for the GFS - we have gone from a strongly positive tilt yesterday on the 12z

http://modeles.meteociel.fr/modeles/gfs/archives/gfsnh-2014112212-0-108.png?12

 

to a negative one tonight--- So the GFS follows the UKMO & GEM ....

 

S

Steve, you are 12 hours out on your charts!

[swfc]

Im hearing talk of an upgrade on the 18z?looks pretty similar to the 12z tbh if things slightly further west???

[knocker]

The anomalies tonight are showing a slight shift change.

 

NOAA 6-10 has the HP north Pacific linked via the pole to Scandinavian HP. Canadian trough not extending quite as far south east allowing the Azores HP more influence and another linkage to the Scandinavian HP. The GEFS goes further with more dominance from the Azores HP in eastern Atlantic and this is even trumped by the ECM although at the same time the latter weakens the Scandinavian HP.  On the surface this tends to a zonal flow with  HP in western Atlantic and Scandinavia and low pressure over Greenland. It must be said that at T336 the GEFS reintroduces the trough in the eastern Atlantic which is more in line with the NOAA 8-14 so the jury is still out.

Edited November 23, 2014 by knocker

[swfc]

Well the 18z takes the jet into north africa out in fi and the low still wont undercut!!! :rofl: Incredible tbh !!!

Edited November 23, 2014 by swfc

[nick sussex]

Quite a mix of features going on in the GFS P in particular.

 

Mean looking PV

Arctic high

Azores high ridging ne

Russian high

Low heights over the northern Med

 

If the PV would  at least pull further nw or weaken we might be in business, overall amidst the mixed signals the best today IMO is low heights in the Med, that's really nice to see.

 

This is normally a good sign that at least the PV won't push the Azores high into that region, interesting that the GFS P gives us a nice end to its higher resolution output.

 

Of all the winter correlations for the UK  low heights in the northern Med means you won't end up with mild muck and more likely to go cold .

Edited November 23, 2014 by nick sussex

[SMU]

Interesting Navgem 18z

 

http://www.meteociel.fr/modeles/navgeme_cartes.php?ech=6&code=0&mode=0&carte=1&archive=0

 

Identical to the JMA 12z.

 

S

[blizzard81]

Interesting Navgem 18z

 

http://www.meteociel.fr/modeles/navgeme_cartes.php?ech=6&code=0&mode=0&carte=1&archive=0

 

Identical to the JMA 12z.

 

S

Now cmon Steve, you know better than to bring out the cannon fodder!!