winter model output Winter Model Output Discussion -12Z 07/02/13 onwards

[AWD]

Right, for those that want a run down on what the 12z GFS shows without bias here it is.

Starting on Sunday when the interest starts. Sunday morning sees low pressure head SE down the western side of the UK;

Bringing PPN to much of Ireland, Wales and western England.

Away from the highest ground in the north, this will be rain due to less cold upper air temps caught up in the low;

as a result both Dewpoints and WBFL are also high;

Sunday afternoon and the centre of the low is over SW England, so further west than previous GFS runs;

as a result, colder upper air starts feeding into the east and north;

and with the PPN;

On a NW/SE axis over much of England and Wales, the NE flank of PPN will start to turn to snow;

By Sunday evening, the low really hasn't moved much;

and continues to draw in colder, continental air on its northern flank;

and the PPN continues to turn to snow from the north;

As drier, colder continental air mixes out the less cold air from the north, shown here by lower Dewpoints;

and lower WBFL values from the Midlands northwards;

Sunday night into the early hours of Monday morning and the low is now centred in the English Channel;

with much of tye M4 northwards under cold upper air;

not just shown by the 850's, but also here;

At this stage however, the PPN starts to break up and dilute;

so lighter PPN for most, but still showing snowfall for much of the Midlands;

Monday morning and a cold easterly/north easterly is present over much of the country;

as the low continues to very slowly sink south east;

The organised PPN has now cleared most of the country, but in the cold feed, snow showers quickly start up and pepper the east coast;

Into Monday afternoon, and it stays cold;

and snow showers continue in the east;

with cold surface temperatures for most;

Got to go now, my tea is ready, but that's the gist up until Monday afternoon. Probably change by the next run anyway!

[chris55]

UKMO looking much better at 144 this evening as well, much more blocked with the UK still very cold at the surface.

[Summer Sun]

GEM has pushed Sunday's low way out west - maybe the east missing out on the precipitation.

Yes the east could miss out on Sunday but Monday looks the likely day if the easterly kicks in as per UKMO

[weather eater]

GEM has pushed Sunday's low way out west - maybe the east missing out on the precipitation.

Yes funny that, I said on my earlier post if it keeps going west at this rate it will miss us altogether but that was a joke.

[Severe Siberian icy blast]

I'm beginning to think that the UK is on the cusp of a major cold outbreak.

This is the ukmo 36hrs from now

This is what happens at t72

Notice the undercut , now at t36 you wouldn't of necessarily saw this coming would you ?

Now look at t120

Now this is the predicted chart at t144

Even At this range , the Atlantic has know chance against this block ,even in this last chart we are so close to a penetrating easterly , I'm certain any energy from the Atlantic will go under the block rather than sinking it , keeping this Azores high in its place .

All I'm seeing is cold easterly winds to be honest now and il put my wages on it ! Any chart showing a rampant northerly jet to be looked at with EXTREME caution .

[Nigel Langton]

Thankyou. This is a fantastic example of a 'perfect post' for people like myself how want to learn about models and get a heads up of what to expect weatherwise. Better than a BBC forecast.

[bradymk]

UKMO, GFS and GEM all show the norwegian shortwave. Steve's post illustrated well the difference between a shortwave and no shortwave on NOGAPS 00z and 12z respectively. How that shortwave "behaves" is crucial to a more prolonged cold spell. We may even get away with having a shortwave there but we would need it to "behave" differently to how GFS and UKMO show. Saying that, GFS away from the far west shows T2m temps staying cold for most of the week. Potential for a sig snow event Sunday into Monday but this situation is constantly changing so I wouldn't want to say where/how much yet.

[Mucka]

Flicking through GFS ensembles roughly 45% of runs want to keep us on the cold side of the jet with some undercut and battleground UK post 144h, so all to play for.

Here is the GFS 12z short ensembles in graph form for central UK.

http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=251&ext=1&y=47&run=12&runpara=0

http://176.31.229.228/modeles/gens/graphe_ens4.php?temp=1&x=251&y=51&ext=1&run=12&runpara=0

Don't look mild do they?

[reef]

Can we stick to the models?

[chris55]

Overall I'd say the charts are loaded with potential at short range and trending colder in the mid range, not to bad for some February model watching in the UK!!

[Cecil Hogmanay Melchett]

Just saw susan powell talking about an increasing snow risk sunday but a fliud picture the graphics looked an absolute dogs dinner so if the pro's are unsure then i think that says it all.

I wouldnt be at all suprised to see these lp's turn out much further south and west than currently being shown,what that means down the line is subject to debate1

[Ryan Dutch Weatherman]

Is it alloud that i put the name of my weathermodel forum here . Not for looking members , but than you can see i am Dutch en i run for 20 years weather .But you can see only the frontpage of it , becouse it is a closed forum .

I admit i am different en some funny than other weathermans , but they are so bored with oldschool faschion talk.

Ok very soon EC en other models will begin their 12z oper runs.

I must see i see very good postings en charts here.

Good work people , good wordk you are better than me en the rest , i am proud of you all.

It is about the weather en the people who hve eyes en sense for that.

Ok now serious , wait for ECMWF the mother of oll weathermodels.

[Methuselah]

Is it alloud that i put the name of my weathermodel forum here . Not for looking members , but than you can see i am Dutch en i run for 20 years weather .But you can see only the frontpage of it , becouse it is a closed forum .

I admit i am different en some funny than other weathermans , but they are so bored with oldschool faschion talk.

Ok very soon EC en other models will begin their 12z oper runs.

I must see i see very good postings en charts here.

Good work people , good wordk you are better than me en the rest , i am proud of you all.

It is about the weather en the people who hve eyes en sense for that.

Ok now serious , wait for ECMWF the mother of oll weathermodels.

Best you don't...

[SMU]

12z GFS MEAN @ 228

http://modeles.meteociel.fr/modeles/gens/run/gensnh-21-1-228.png?12

now sending energy under....

S

[chris55]

12z GFS MEAN @ 228

http://modeles.meteo...21-1-228.png?12

now sending energy under....

S

trending in the right direction Steve!

-5 line trending west in FI as well.

http://www.wetterzentrale.de/pics/Rt850m12.gif

Edited February 7, 2013 by chris55

[Weathizard]

Was just about to post that Steve, interesting individual members at 200+ too, certainly some nice evolutions within 10 days.

With regards to near time frame, ENS look good for country wide snow fall, I think the OP will be on the very mild side of the members within 100 hours, whether or not the ens are worth anything within such a close time frame is a good question but still lots of different way it could evolve. Worth noting as well that the Canadian vortex looks like its definitely on its way out, which ca only be good news.

Mean at T84 pretty nice

Wont take much to make this a big event really, few hundred miles shift, thats all.

Edited February 7, 2013 by Weathizard

[Mucka]

12z GFS MEAN @ 228

http://modeles.meteo...21-1-228.png?12

now sending energy under....

S

Yes, even several of the runs that back the pattern too far East or look to send too much energy NE in hi res still manage to back things up later and get some undercut.

Given that I would say the prospects for continued cold are improving despite the mixed signals coming from individual Op runs.

I am looking forward to the pub run since that was the coldest of yesterdays runs but more significant will be ECM's take on the prospects of undercut post 144.

We have two very interesting scenarios to keep tabs on. The snow potential over the latter part of the weekend and early next week and the bigger picture that develops thereafter. Both are in a state of flux so a fascinating period of model watching

[bluearmy]

GEM was west this morning aswell re sunday. going to have to rely on the faxes now for sunday and the NAE come tomorrow afternoon.

like the way the gefs are headed

[jules216]

best ensembles of the season on gfs 12z check them out guys around 320 hrs, i know its fi but a pleasure to look at if your coldie

[bradymk]

Impressive GEFS 12z, from start to finish, GEFS offering quite a few options for Sunday also, too much uncertainty at the moment.

[chris55]

GFS 12z op on the mild side of the ens throughout!

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=317&y=141

[Blizzardof82]

best ensembles of the season on gfs 12z check them out guys around 320 hrs, i know its fi but a pleasure to look at if your coldie

Looking at those maybe our Dutch friend is on to something!

[Mucka]

GFS 12z op on the mild side of the ens throughout!

http://www.meteociel...t=1&x=317&y=141

That is quite a strong cold signal building after the mid month uncertainties.

[Barry12]

Coming from a Scientific standpoint like snowballz, i think the GFS is on the milder side of the ensembles, certainly not implausible, for on the extreme side of reality more fiction. The ECM doesn't matter whether it show's cold, mild, rain or snow it's more the science that interests and engages me as an self confessed expert Mathematican and from a scientific standpoint. To the people who are saying it's all 'rain', the NWP's are not stable enough to predict with any mere accuracy whether it will be snow or rain. Wait to the NWP's are closer to the plausible solution and then we *may* be able to correctly decide whether the current NWP's are stable enough to predict such 'events'.

[bluearmy]

T72 FAX out quite early and places the shortwave centre over cornwall. pretty much where gem has it