Model Output Discussion

[Harsh Climate]

Despite the fact every single model is showing virtually the same output past 5 days ,never seen such model agreement before regarding a cold spell

What models are you looking at then

lol, actually for the past few days they have been toying with lots of different outcomes.

[Yeti]

Yes, I do share your concerns wrt that low dropping south across Scandi. Both GFS and ECM show milder sector being dragged south by this low from a pool of WAA over Iceland, so uppers become less cold after the initial easterly developing this weekend. but then both models pull the low SW and allow a bitter NE'erly to develop ... eventually.

We need to hope that the upper low/cold pool eventually turns SW over the N Sea rather than sink S or SE into central Europe otherwise we may not tap into those coldest air and there is still time for the models to change in respect of a less favourable track of the shortwave moving S early next week. Alot depends on how the low develops and interacts with the southward moving jet streak down the N Sea/Scandi. Still room for error in respect of modeling the shortwave ... which may in turn delay the backing west of the real of the frigid cold towards us.

I'm praying the track changes to straight S... but that's me being selfish!

Temps a touch lower perhaps on the 18z. Just look at the WAA carving out the block at 72!

http://www.wetterzentrale.de/pics/Rtavn721.png

We haven't seen synoptics like this in years... if the current charts were to come off, we would have a cold spell to dwarf last February in both intensity and duration. And all this before Christmas!

Let's just hope it doesn't all go to pot... or I can see a bumper profit for prozac!

[SMU]

To be honest the models have been far more consistent lately than I think I've ever seen them, with the gfs parallel in particular having shown roughly the same outlook for days now. As many experts on the forum have already said, the building blocks are in place, with only a few details to work out. When JH says he is 90% certain of this cold spell, with as good model support as we could possibly expect, I think people have a right to get a bit excited about what are, after all, exceptional charts. After all, it's what most model watchers have been looking for since they first started model watching! Although it still could all fall apart, I think it is more likely than not to happen.

LS

http://91.121.94.83/modeles/gfs/run/gfsnh-0-96.png?18

Here we go- the 18z firing into action - just 6 hours behind the 12z-

Eyes down for a full house on the deep trough moving through Scandi-

remember even though it has a warm sector the SE & EAST could have enough embedded cold at the surface to hold it as sleet & snow-

A PERFECT TOM SE20 Easterly flow at 108-- angle around 265 degrees- with -8c approaching-

Could be a small streamer-

S

Edited December 9, 2009 by Steve Murr

[NorthantsSnow]

Bit of a slight downgrade early on with that initial easterly shot...but it was never looking particularly strong anyway.

http://209.197.11.95/c9s4a5k3/cds/gfsimages/gfs.20091209/18/93/h850t850eu.png?dopvhost=charts.netweather.tv&doppl=0f36092b441616de&dopsig=67598bf572d41e77be29ac3d4e6d2c5f

[Harsh Climate]

And If you think these charts are very similar you need glasses mate

ukmo http://www.wetterzentrale.de/pics/Rukm1441.gif

ecm http://www.wetterzentrale.de/pics/Recm1441.gif

gfs http://www.wetterzentrale.de/pics/Rtavn1441.png all at 144h

Edited December 9, 2009 by Jed Bickerdike

[SnOwFeSt]

I still have memories of last December (just after xmas) fresh in my memory. Seem to remember that GFS showed a stonking high pressure over greenland, with low pressure after low pressure dragging -15 850 air directly from the north at about the same distance as the current cold spell shows (5-6 days away). A different scenario, sure, but everyone was ramping + I was convinced it would happen, instead we ended up with dry cold inversion weather (which was nice, but not as exciting as was predicted/expected).

Just a note from memory lane to suggest that this is far from nailed - short waves and the exact positioning of high pressure can alter things significantly beyond +72 or perhaps even shorter!

[Yeti]

And If you think these charts are very similar you need glasses mate

ukmo http://www.wetterzentrale.de/pics/Rukm1441.gif

ecm http://www.wetterzentrale.de/pics/Recm1441.gif

gfs http://www.wetterzentrale.de/pics/Rtavn1441.png all at 144h

Well they all look pretty similar to me; remember it's T144 so you'll never get complete agreement! All show the shortwave to varying extents (GFS maybe overcooking; ECM undercooking); all show the strong block with slightly different shaping and hence these two things combined alter the flow slightly over Europe. This is all that matters atm - there have been so many past cases of totally different outcomes at 144, and yet here we have all the main models showing a cold incursion from the NE with the upper trough riding beneath the block. To me that's quite rare - rarely is there so little diversion at this range. Yes, there are differences but none so great that it's a case of "all or nothing" as seen in the past.

[Harsh Climate]

http://www.wetterzentrale.de/pics/Rtavn1202.png

No real differences so far

[stewfox]

Although it still could all fall apart, I think it is more likely than not to happen.

LS

A cool down and then... thats what the models are saying at present.

The only 'fall apart' or 'disaster' that could happen now is driven by peoples expectations of '10ft snow drifts -18c 850pha . If they dont come off then all the models will be dismissed as tosh again. Major major 'let downs' etc.

I'm please we might even get a frost with reliable time frame with a increasing looking Easterly feed

No one should post a thread 'Goodbye even larger teapot' just yet

Of course cold snaps in the middle of February lead into the end of February with day light hours increasing. The one (of many things) I like about December 81 was that low angle of the sun

[Nick F]

Love the way the pool of sub -10C T850s slips west to the south of the UK over France at t+120 ... the benefits of having nothing but land to the east I suppose.

[I remember Atlantic 252]

high seems further south, not too good?

[anvilhead]

Is that snow on monday? http://www.wzkarten.de/pics/Rtavn1204.png .. looks like a convective shower train running Ne to SW to me ?

[Harsh Climate]

Well they all look pretty similar to me; remember it's T144 so you'll never get complete agreement! All show the shortwave to varying extents (GFS maybe overcooking; ECM undercooking); all show the strong block with slightly different shaping and hence these two things combined alter the flow slightly over Europe. This is all that matters atm - there have been so many past cases of totally different outcomes at 144, and yet here we have all the main models showing a cold incursion from the NE with the upper trough riding beneath the block. To me that's quite rare - rarely is there so little diversion at this range. Yes, there are differences but none so great that it's a case of "all or nothing" as seen in the past.

fair enough I think the point I was trying to make is that this is far from set in stone and the charts are struggling to come to a conclusion of what exactly will happen and will do untill about 72h. So far too early to start predicting snow.

[frozencamel]

Hi all,

Looks like the winds are stronger on this run over the top of the high over Finland. May be the colder air will come down with a bit more zing

[swfc]

look to the far north east,reinforcemnts on the way.great run.

[Cloud 10]

What an absolutely stonking chart to have at +144.

[Harsh Climate]

http://www.wetterzentrale.de/pics/Rtavn1442.png

Im liking the look of this run, I think central parts of britain are guna take a direct hit to easterly winds down the line, rather than scotland..

[cooling climate]

Looking at the 18z GFS run come out and then comparing it with that of the

12z ECM and also the 12z GFS on the meteociel n/hemisphere charts it looks

like the Siberian Arctic high is coming more into play(moving further south)

than was programmed a couple of days ago.

This would almost certainly lead to a much more frigid source of air with

even more instability as it crosses the n/sea.

[kold weather]

Looks like a fine run at the moment, out to 144hrs and the shortwave has developed pretty well, so should still be a good run.

Looks like a little bit of slightly less cold air comes in but then the risk for snow increases for Monday eveing before pressure increases too much, probably only wintry conditions on the band coming in on Monday morning however.

[Optimus Prime]

Can't really see anything especially cold nor wintry on this run. Very marginal really...am I missing something?

[Tom Quintavalle]

Our trigger low wants to park itself over Copenhagen, how ironic?

Regards,

Tom.

[cyclonic happiness]

Are we treating this as the main 18z GFS run now or the parallel?

either way, this one seems fine.

[stewfox]

http://www.wetterzen...s/Rtavn1442.png

Im liking the look of this run, I think central parts of britain are guna take a direct hit to easterly winds down the line, rather than scotland..

Another T144 , have been numerous T144 posts for a few days

Lets hope it stays that way at T72 ?

[TEITS]

Latest fax chart is out.

http://www.wetterzentrale.de/pics/brack4.gif

Splendid chart and note the SW off the Scandi coast. Possibly a few wintry flurries in E Anglia/SE!

[Nick L]

Can't really see anything especially cold nor wintry on this run. Very marginal really...am I missing something?

Yup, that big pool of cold air over Norway heading straight for us!

http://212.100.247.145/viewimage.pbx?type=gfs;date=20091209;time=18;ext=159;file=h850t850eu;sess=3ffa13ecce20263c329bb134011b435b;