General Model Output Discussion

[bluearmy]

significant ECM- I have tracked todays 12z's UKMO GFS & ECM together - 72, 96 & 120-

ECM still keen- just like the GFS to get the shortwave UNDER the block at day 5 with an initial Easterly vector-If this happens its almost odds on that the UK will stay on the Northern side of the PF until xmas eve, with some potentially heavy snow moving up into the South thereafter-

how far does it get North is the question-

Steve

given the propensity for stuff to get shifted a few hundred miles se as we approach verfication, that may well only get better. mind you, does that adage work with a -AO. ecm NH still looks in need of a large dose of cenakot latter stages of next week. if that verifies, i will be amazed if any breakdown is long lasting.

[JamieUK]

Nothing wrong with discussing events at 120-140 hrs,this is the model discussion thread not the "incredibly short range model discussion thread"

No, but don't you think it makes sense to look at the coming day or two which is changing here there and everywhere rather then even further out which, obviously of which you must know now....will change and will be unpredictable. I wanna know whats happening with the models now, not drivel about later on. Good to look at, not to talk about.

[Barb]

Don't like ECM. Cold spell history by Wednesday. I'm a dreaming of a wet and windy Christmas...

Long way off though.

Edited December 16, 2009 by Barb

[swfc]

personally anything beyond t 90 is up in the air.ecm is pretty good and in my opinion were not far off another easterly at 166 hrs.all to play for .

[Richard Lake]

Again when I see posts like this I wonder if I am looking at a different set of charts to some other members. The easterly for tomorrow and early Friday has actually upgraded in the last two days- there were some earlier runs that had limited snow potential away from the extreme SE as the shortwave currently over East Anglia was progged to move too far east. The snow from the easterly behind this shortwave was always forecast to begin at any time between today at the earliest, and Friday at the latest. The reality is late on Thursday, so the middle ground solution is set to come to fruition.

Evening,

Actually the cold weather was hyped up to be on Monday... or did we all forget last week? I'll believe it (the snow) when I see it as it constantly gets pushed back.

[wellington boot]

Tota;;y agree 24hrs 48hrs not 120 140.

Perhaps the wrong thread for you then. The thread is titled model discussion, so while the models may be difficult and changeable a way out, this thread is dedicated to their discussion. So long as we don't take them too seriously, there is no harm in this.

Having said that, the models do want the lp to drift somewhat west and bring a slightly more southerly/westerly flow. I think we probably have to accept that to an extent. As someone was saying though, the surface flow from France will likely be cold anyway, so this doesn't necessarily pose too serious a problem. What needs to happen is that at some point within that large area of lp which will likely develop, a centre must form which will drag some air in from at least a more se'erly direction, prolonging the cold air. Thereafter the key will be whether heights can rise once again to the north or west. The gfs shows hints that this might be possible. Even the ukmo doesnt show complete erosion of the hp to the northwest. Im going to be keeping my eyes on this.

[wellington boot]

No, but don't you think it makes sense to look at the coming day or two which is changing here there and everywhere rather then even further out which, obviously of which you must know now....will change and will be unpredictable. I wanna know whats happening with the models now, not drivel about later on. Good to look at, not to talk about.

You're not going to endear yourself to anyone here by accusing them of writing drivel. Just because you perhaps do not possess the knowledge required to make an attempt at analysing difficult models, it is not appropriate to instruct people to write about what you 'wanna know'.

In any case, the models for the next day or two are not changing here there and everywhere unless you look at them on a very local scale, in which case that is often true.

Re: the ecm, I think it is not far off being an exceptional run. There's no surge of warm air in there, heights never really give up in the northerly regions, and at several stages it looks close to a reboot of the cold. Encouraging I'd say.

[Thundery wintry showers]

Evening,

Actually the cold weather was hyped up to be on Monday... or did we all forget last week? I'll believe it (the snow) when I see it as it constantly gets pushed back.

Only on the basis of three GFS runs and one UKMO run! Most runs had nothing of it, and the ECMWF never showed snow on Monday at all.

I am getting a little concerned about a possible latching onto the pattern I mentioned earlier, where it slowly turns mild and wet from the south towards Christmas due to low pressure holding "in situ" to the west and blocking developing to the east. The latter is the main difference relative to the Dec 1981-esque runs I mentioned, which had lows sliding from west to east to our south and keeping us in colder air. But this is only one set of runs, and as it is keep changing, it might change again.

A lot hinges on the track of this low coming down from the Arctic as well. Earlier runs (and also the current GFS) had it sliding south almost on top of us rather than out west, and that reduces the chances of us picking up a southerly.

[swfc]

So where would the 216 ecm chart leave us temp wise and precipitation,ie rain or snow.still think given the pressure to the north the low couls skirt southern britain.

[Cumulonimbus Tower]

Only on the basis of three GFS runs and one UKMO run! Most runs had nothing of it, and the ECMWF never showed snow on Monday at all.

I am getting a little concerned about a possible latching onto the pattern I mentioned earlier, where it slowly turns mild and wet from the south towards Christmas due to low pressure holding "in situ" to the west and blocking developing to the east. The latter is the main difference relative to the Dec 1981-esque runs I mentioned, which had lows sliding from west to east to our south and keeping us in colder air. But this is only one set of runs, and as it is keep changing, it might change again.

A lot hinges on the track of this low coming down from the Arctic as well. Earlier runs (and also the current GFS) had it sliding south almost on top of us rather than out west, and that reduces the chances of us picking up a southerly.

I suppose another desirable scenario would be for the low pressure system to sink far enough south west for us to tap into some nice frigid air being ejected from the forming Scandi surface HP…(à la NOGAPS nearly)

Edited December 16, 2009 by ned

[cooling climate]

The t168-240 charts are so close to being very good charts although they probably are for Ireland and Scotland.

A 500 mile shift eastward and we would all be happy.

Maybe the ECM is being to progressive with retrograding the high over Greenland.

All to play for still.

The BBC regional weather forcast for east Anglia and the southeast a few minutes ago was excellent

although they were programming the temps a little high I think.

[ANYWEATHER]

The 12Z ecm shows the cold lingering across the Uk right into the Holiday season....

[snow1975]

Hello

The low might head further south and get caught up in the southerly jet stream and be shoved east into the Med with very cold easterly winds returning to the UK.?

[Nick F]

The 12Z ecm shows the cold lingering across the Uk right into the Holiday season....

But winds across the UK are from the S or SW on that chart mate?

[cyclonic happiness]

Hello

The low might head further south and get caught up in the southerly jet stream and be shoved east into the Med with very cold easterly winds returning to the UK.?

possible FI has been showing loads of different secenarios over the past 2 days, I'd say its 60/40 erring towards a cold outlook, we'll just have to see.

[Highland Snow]

Given the latest 72hr fax for 12hrs Sat it doesn't come as a huge surprise to me. I think snow is possible down to sea level almost anywhere at times, especially in the heavier outbreaks/showers, but equally I wouldn't completely rule out some rain anywhere on low ground south of Scotland either - looks a bit of a cold mess IMO.

Thanks Worzel. Still can't understand those temps. of 4-5C behind the Occlusion with the air source obviously from the Arctic Circle.

[snowlover2009]

if tonights fi charts for xmas come off, would it be colder than last years christmas?

[snow1975]

Thanks Worzel. Still can't understand those temps. of 4-5C behind the Occlusion with the air source obviously from the Arctic Circle.

I think there could be some less cold air coming in behind the front for a short while, afterall there is some warm air mixed in with this system.

[Frosty.]

It's starting to look less likely that the cold spell will last longer than christmas day or boxing day with the atlantic lows moving in from a sw / ne direction to bring less cold and then milder air northeast but remaining unsettled with rain and probably more flooding with the snow melt which will be considerable. Scotland should hang on to the cold air for longest. The comparisons with 1963, 1978-79, jan 1987, feb 1991 seem a little OTT now in my view but certainly we are in for a wintry 4-6 days ahead to rival the best cold snaps we had last winter maybe.

[swfc]

I think given the change from this mornings output regarding the position of the low at i66 hours on ecm it proves that come tom mornin g we could be in another easterly.all to play for in my opinion and the models are really struggling

[phil nw.]

The 12Z ecm shows the cold lingering across the Uk right into the Holiday season....

It does show how much further west the pattern is shifting though.The omega block ,whats left of it there,is over the Eastern seaboard almost.

This is the problem of keeping the cold next week.

It`s shaping up for -v NAO too west based, allowing the warmer air coming north on the eastern side of the trough towards us.

The ukmo at t144hrs.

http://www.wetterzen...cs/Rukm1441.gif

Compare the t192hr chart you showed with this at 72hrs,

http://www.wetterzen...s/Recmnh721.gif

We can see how the whole pattern is modelled further west dragging the lows with it,early next week.

Edited December 16, 2009 by phil n.warks.

[Harsh Climate]

ecm

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

ukmo

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

Not the best ecm and ukmo this evening regarding the longetivity of this cold spell, but still time for big changes.

If these charts were to come to fruition milder air would probably end up spilling in from the south east around the vortice, probably allowing for a snowy breakdown boxing day.

I think we need these invading lows to make it as far south and deep into europe as possible as that would lower the chances of high pressure becoming established across europe after any breakdown and would leave us in the cold air longer.

Edited December 16, 2009 by Jed Bickerdike

[Iceberg]

The ECM is very very nearly a fantastic chart at 240, thicknesses even the south at only just above snow at approx 532-533, colder further north, obviously.

[cyclonic happiness]

It does show how much further west the pattern is shifting though.The omega block ,whats left of it there,is over the Eastern seaboard almost.

This is the problem of keeping the cold next week.

It`s shaping up for -v NAO too west based, allowing the warmer air coming north on the eastern side of the trough towards us.

The ukmo at t144hrs.

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

Compare the t144hr chart you showed with this at 72hrs,

http://www.wetterzentrale.de/pics/Recmnh721.gif

We can see how the whole pattern is modelled further west dragging the lows with it,early next week.

Mind you, it's nice to see cold getting shunted west for a change instead of that "oh so annoying" northerly toppler, that gets shoved eastwards into the north sea.

Synoptics are so unusual for the internet model watching era, that they may be badly wrong (or they may be right), but one thing is for sure...we won't end up with EXACTLY the ending shown <_<

[Nick F]

The ECM is very very nearly a fantastic chart at 240, thicknesses even the south at only just above snow at approx 532-533, colder further north, obviously.

Winds on the ECM t+240 chart are off the Atlantic and the charts available to the public only show the geopotential height not 1000-500mb thickness, you can have a 500mb height of 528 decameters (5280m) but it can still be mild at the surface at lower levels if winds are sourced from a mild direction. Lapse rates would be steep towards the NW though on the t+240 chart - so the low heights would give snow over high ground of the N and W.