Model Output Discussion

[weather eater]

FORECASTER: BRAD PUGH

The ECM has verified the poorest model in the last few days and it does seem to want to severe links

to the Siberian high which does not gel with what the other models are showing.

Never the less we are just talking detail the basic pattern is still there just differences with regard

to degree of cold and snow.

Pretty much as I was saying, certainly the operational ECM 00z has been flopping about like a landed fish for the last four days.

[kold weather]

The ECM is fine, sure it doesn't look loke there would be much snow and its not quite the severe set-up of yesterdays run but the Greenland high remains solid through and you'd get severe frosts under that sort of high pressure set-up...besides that shortwave is still causing all manner of problems for the models.

Very much swings and roundabouts this one folks, the easterly is now getting re-upgraded again on the models for Tuesday, snow showers would be very likely overnight Monday-Tuesday and probably heavy ones at that on the 06z.

Also looking at the 06z, that ESE flow would be utterly bitter, and also very snowy indeed for the east coast. Also whilst the ECM isn't a bad run IMO, it has been very inconsistant with regards to the evolution of this set-up, not sure how much trust can be put into it with this set-up this time, though you never quite know with the ECM whether its picking up new trends or just having a bad un.

[weather eater]

perhapes you could give me some more detail on why this is only a 1 week event,

i thought there was a reload.

from what ive lernt and seen over the years is pressure being high can last weeks.

with this being a omega block and gl high building surely this inplace cold is more likely in our neck of the woods.

some people on here are saying gfs is brillant the only model which is the holy gral ecm being not so good.

so please a expert opion would be welcome.

All I'm saying BB is that if a trends can be spotted in FI, then the trend on the parallel is for a break down during the second week, however we all know how output can change and trends change, it’s an observation not a forecast.

[Geordiesnow]

I think we are in danger of failing to appreciate what we have in the reliable timeframe rather than worrying about the medium/longer term.

Im so used to seeing fantastic charts in F.I and here we are with some fantastic charts between +72 & +144.

http://www.wetterzentrale.de/pics/Rtavn1201.png

To be fair, what you are saying is true, however seeing as we have not got agreement, then it's still to hard get excited.

If we can get the UKMO/ECM more on board with this easterly closer to the reliable timeframe, then i might get excited and worry less about the medium term.

[Tom Montalbano]

This is a better run out to t144 than the 00z, note the elongated low moving east into France, wasnt there on the 00z.

Regards,

Tom.

[VillagePlank]

Here's the Theta-W chart for Monday evening (still >T=96, so on the edge of reliability) As a general rule of thumb, if the Theta-W temps are below 0C, and it precipitates, it is a reasonable indiciator (on it's own) for snow-worthy air - of course, normal 500hPa, and 850hPa rules apply, too ...

Edited December 10, 2009 by VillagePlank

[cooling climate]

This would be a bitterly cold airflow if it verified with strong east/southeast

winds(windchill)from the midlands south and an ever increasing threat of heavy

snow moving up from the south.

[TEITS]

This is where it gets complicated.

http://www.wetterzentrale.de/pics/Rtavn1621.png

A cold front moving S with colder air behind the front. However ahead of the front we have the colder air via the E,ly with a slightly less cold slot inbetween.

The BBC forecast this morning mentioned snow on Wed and it is this cold front that I think they are referring to.

I don't envy those having to make a forecast next week!

[Snowaddict]

Can this 06Z run really be trusted though in fairness?

It's a fantastic run right from the beginning all the way out to T+168 with another reload from the northeast.

It looks too good to be true... (But I hope that it's right!)..

Snow showers into Ireland by early next also if it's correct..

[Tom D]

The GFS is intent on bringing that Scandi low down over the UK at +150 or so, it's been like that for a few runs now. The problem remains the in between period 120-140 where it cannot make it's mind up at the moment.

[Guest North Sea Snow Convection]

This GFS easterly early next week is superb and seems to be getting stronger and colder with more snow potential with each output!

There is not the agreement to the same extent with the other models though yet however - but very interesting nonetheless!!

[kold weather]

LP looks like it could become absorbed into the main Atlantic low this run, thats the biggest risk for a long cold spell there is because it could force the main low northwards, or equally it could stay far enough south and drag in the real cold continental air. Tough one to call.

Also, still cold enough overnight for snow on the 06z upto 168hrs, temps and dew points still below 0C away from the coasts even though uppers aren't nearly so cold. I'd imagine the bitter cold from the ESE would make a difference in that set-up.

[weather eater]

This is a better run out to t144 than the 00z, note the elongated low moving east into France, wasnt there on the 00z.

Regards,

Tom.

Yes and its really not that much different from the 00z, but those small differences can have a big impact. I think, at least on the GFS that we are getting a fair agreement, Mon/Tue bitterly cold air moving in from the east, Wed a brief warmer sector moving down from the north, followed by much colder air, then as dave says it all gets rather complicated.

Edited December 10, 2009 by weather eater

[Geordiesnow]

Decent enough run it has to be said, i'll worry about the details later but i think i might just start on the first easterly which has been upgraded in fairness.

Until we know if an easterly will happen on Sunday/Monday, the rest of the outlook is subject to change.

[TEITS]

LP looks like it could become absorbed into the main Atlantic low this run, thats the biggest risk for a long cold spell there is because it could force the main low northwards, or equally it could stay far enough south and drag in the real cold continental air. Tough one to call.

Nightmare to forecast.

I would say at the moment the further N you live the greater chance of being on the N side of the SW thus meaning you will experience the bitter ENE,lys. At the moment the most favoured location is E Scotland.

However most certainly subject to change!

F.I is going to be a blast to the past we a very similiar pattern to Dec 31st 1978/79.

Edited December 10, 2009 by THE EYE IN THE SKY

[MR EXTREMES]

I think we are in danger of failing to appreciate what we have in the reliable timeframe rather than worrying about the medium/longer term.

Im so used to seeing fantastic charts in F.I and here we are with some fantastic charts between +72 & +144.

http://www.wetterzen...s/Rtavn1201.png

i totally agree for once i dont see this spell vanishing into thin air its going to be about we need this cold into europe battle ground was a feature of the 80s.

excellent chart posted by eye,

there have been so many brillant charts for a few days now we are bound to see not so good charts this is model watching at its best.

its absolutely lovely out there today blue sky nice frost tonight and getting colder day by day i think anybody that thinks that next week wont produce cold is very wrong,

as for snow this is always finer in detail and is predicted better in 36 to 24hr periods.

imagine how i feel i live on the southcoast and last winter was absolutely brillant even if it onlt lasted a couple of days in regards to snow but cold frost was the prolonged feature of winter it was fantastic.

to see cold and a setup like this so early in winter is the absolutely fantastic aswell so we have the big guns GP JH and others listens to them there confidence is good even if there not toatlly right all the time thats what the weather does best it changes it happens.

but the big guns are sure that winter09/10 will be good for us coldies add the el nino that ongoing yet we are getting this with good high pressure around greenland its all good.

we are all guilty of picking out the best and worst of things the models are concrete on omega block + gh so its all good.

[kold weather]

Well as expected the low does get absorbed however this is where having the upper high still intact over Greenland helps and we get an utter classic battleground situation develop...indeed it takes two fronts to clear the south coast and even then it struggle to make it to the Midlands.

So FI probably less cold for the south but still not exactly mild, whilst the north stays locked in a bitterly cold set-up.

For IMBY reasons I'm not a huge fan of this runs FI even though there would likely be a snow event, my location would get caught up in the milder airflow with temps probably between 3-5 (yes...all relative mild!)

Ends up very mild for xmas as well. Ah well time is on our side for that to change!

One other point, I believe the GFS will be a lot closer to the ends outcome then the ECM but we shall see...and the Paralell run shows how close its going to be in regards to a borderline battle between cold and warm, esp for the south...

Edited December 10, 2009 by kold weather

[TEITS]

I prefer the parallel run.

http://91.121.94.83/modeles/gfsp/run/gfs-0-180.png?6

The SW merges with the LP into france and this pulls the ENE,ly across the UK as the LP then travels into the Med.

A splendid E,ly beforehand though.

[phil nw.]

It would be bitter at T126hrs.

http://91.121.94.83/...gfs-1-126.png?6

http://91.121.94.83/...gfs-2-126.png?6

-12C uppers across England with snow about.

Edited December 10, 2009 by phil n.warks.

[West is Best]

Sensational 6z run. Much better again, with snow pulses in the mix right out to 10 days' time.

I have absolutley no idea why we're discussing the Christmas setup on December 10th though. I mean surely there's a whingeing thread for an alleged breakdown that is, literally, more than a fortnight away?!

I love the evolution on this run - really like the way the north-east attack comes back in, and then further attacks from the south-west. That's precisely what we need. I don't want an arid boring easterly. For big snow events we need a really cold but unstable picture. That's why 1978/9 is so much more interesting than 1985/6. So bring this run on - it's excellent.

[chionomaniac]

I think I'll go on holiday to Morocco to get away from all this cold.

[Harsh Climate]

To be fair the gfs 06s isnt bad, synoptically almost perfect. But the lack of proper cold air brought over from europe is now becoming a dissapointing trend. From this run eastern scotland and the east midlands would do quite well. Apart from transient snowfalls elsewhere can expect snow to be restricted to high ground... And if this comes to fruition coastal areas can forget any lying snow at all!

The crunch period for me is how far that low in the north sea pushes south

http://www.wetterzentrale.de/pics/Rtavn1681.png

If it pushes far enough south, some of the real cold air will be pushed in and with the direction of the wind more from the continent rather than the north sea, the 2m temps should allow for settling snow more widely.

Edited December 10, 2009 by Jed Bickerdike

[Snowaddict]

Some sensational snow events on the 06Z Parallel Run..

In fact, several feet of snow would fall widely across the country..

In the somewhat more reliable, it looks like rather heavy snow could be falling by late next Tuesday if GFS were correct..

Time for this forecast yet??

A STUNNING 06Z GFS PARALLEL RUN!!!!

Edited December 10, 2009 by Snowaddict

[kold weather]

I love the evolution on this run - really like the way the north-east attack comes back in, and then further attacks from the south-west. That's precisely what we need. I don't want an arid boring easterly. For big snow events we need a really cold but unstable picture. That's why 1978/9 is so much more interesting than 1985/6. So bring this run on - it's excellent.

Only boring for you West, a easterly would do me very nicely thank you.

However the evolution is there fo a big snow event, it does need luck though and the set-up is complicated yet further by the other shortwave.

As Eye said, the Paralell run doesn't have quite the same snow event for the Midlands northwards but its a far more sustainable run in the long run..IMO I agre with Eye, its a better run, esp for the south which would have a light/moderate snow event followed by days of rain on the 06z whilst Midlands northwards get snowed in!

[Megamoonflake]

I prefer the parallel run.

http://91.121.94.83/modeles/gfsp/run/gfs-0-180.png?6

The SW merges with the LP into france and this pulls the ENE,ly across the UK as the LP then travels into the Med.

A splendid E,ly beforehand though.

Yip the parallel run is something else and I thought the GFS 6Z run was amazing! It will be interesting to see if the ensembles adds confidence to these runs...... Roll on next week I can't wait to see the first flakes of the winter.