Model Output Discussion - 28th November - 4th December

[Frosty.]

The gfs seems to be struggling a lot in the closer timeframe of 3-5 days so if it can't even plot the track of the midweek low, surely it has got a bigger problem with FI? As things currently stand, there is now a big risk of disruptive snow affecting western scotland tomorrow night and snow showers generally across the northern scotland and then snow showers pushing further south on monday but then during tuesday and wednesday it becomes less cold again with a large sector of air originating from the north atlantic with rain rather than snow just about everywhere, then turning colder from the north with snow showers spreading south before pressure builds from the west next weekend with sunny days and frosty nights.

[lorenzo]

PL I think to be fair any model would not have the capability to effectively model the systems coming through the Greenland - Iceland Corridor at present, healthy jet profile thrown into the mix there.. the then turning colder in the North point you mention is where I think the models are at tipping point for choice of evolutions. Probably not resolved until Monday Tuesday 12 z even, encouraging however that this NW re-load is happening to maintain interest before a trended MA Ridge topples and resets to the static High pattern of November.

Interesting forcing the PV is throwing out. Also on this run it re-organises itself in spectacular fashion absorbing another low from across the hemisphere.

[weathe20]

The gfs seems to be struggling a lot in the closer timeframe of 3-5 days so if it can't even plot the track of the midweek low, surely it has got a bigger problem with FI? As things currently stand, there is now a big risk of disruptive snow affecting western scotland tomorrow night and snow showers generally across the northern scotland and then snow showers pushing further south on monday but then during tuesday and wednesday it becomes less cold again with a large sector of air originating from the north atlantic with rain rather than snow just about everywhere, then turning colder from the north with snow showers spreading south before pressure builds from the west next weekend with sunny days and frosty nights.

The GFS is not struggling, its outputing charts with the data it is given.

[nick sussex]

Looks like the ECM isn't following the GFS/UKMO, the 144hrs chart is either going to show that shortwave being forced se towards the UK with the trough being held back and more pressure rises over Greenland or something far less palatable, i don't think theres going to be a middle ground here, either wow or urgh.....

[Cecil Hogmanay Melchett]

Looks like the ECM isn't following the GFS/UKMO, the 144hrs chart is either going to show that shortwave being forced se towards the UK with the trough being held back and more pressure rises over Greenland or something far less palatable, i don't think theres going to be a middle ground here, either wow or urgh.....

That will be an urgh then nick.

[nick sussex]

That will be an urgh then nick.

It's an urgh with an asterix! something weird is going on with the PV, with the odd tweek at 144hrs it could be quite interesting, perhaps the 168hrs will be close but no cigar but don't give up hope yet!

My advice bin all the output past 96hrs, the only model thats been consistent over the last few days has been the UKMO and given the strange goings on this evening thats probably wrong aswell.

I do hope after this longwinded saga the UK ends up with something tangible in terms of a colder shot, all I can say is that the output is interesting but all over the place!

I will be interested to hear what NOAA make of all this considering they had already had low confidence in their morning discussions.

Edited December 3, 2011 by nick sussex

[Nick F]

Yes, ECM alot flatter with the jet than GFS at the end of the week, so the Azores high is unable to build north - which means the coldest air moving south maybe prevented from getting as far south as GFS, with winds tending to blow from the west across the south.

Subtle differences in the upper flow crossing the Atlantic will make all the difference to what occurs at the surface, something the models may not resolve beyond T+96. Need to keep an eye on the waves coming out of N America over the coming week to see whether a temporary ridge can build north towards Iceland/Greenland by next weekend as GFS and UKMO suggest.

Looks like northern Britain will hang on to cold zonality for much of the next 7 days though, with hill snow and snow falling to lower levels at times - especially across Scotland. Less cold for southern Britain, with rain at times.

[chionomaniac]

It's an urgh with an asterix! something weird is gong on with the PV, with the odd tweek at 144hrs it could be quite interesting, perhaps the 168hrs will be close but no cigar but don't give up hope yet!

My advice bin all the output past 96hrs, the only model thats been consistent over the last few days has been the UKMO and given the strange goings on this evening thats probably wrong aswell.

I do hope after this longwinded saga the UK ends up with something tangible in terms of a colder shot, all I can say is that the output is interesting but all over the place!

That's quite a big difference at T+168 Nick between the main two.

I think that anyone with experience has been here before and is wearing the t-shirt. I suspect that the amplification being played around with over the last few days will prove to be an exaggerated version of what will happen.

As ever I will always go with the model that fits in with the background signals and tonight up to T+168 that is the ECM.

[ukpaul]

The GFS is not struggling, its outputing charts with the data it is given.

Mere semantics, you know what he means. He isn't suggesting the models have an independent intelligence!

The models are 'struggling' then, in that the data is coming up with wide variations from run to run. That much is clear. ECM and GFS being very different in the medium range suggests nothing else.

Edited December 3, 2011 by ukpaul

[nick sussex]

That's quite a big difference at T+168 Nick between the main two.

I think that anyone with experience has been here before and is wearing the t-shirt. I suspect that the amplification being played around with over the last few days will prove to be an exaggerated version of what will happen.

As ever I will always go with the model that fits in with the background signals and tonight up to T+168 that is the ECM.

The problem is that we're not talking of differences in FI, there is no agreement at 96hrs so even if the others are overamplifying the pattern at 144hrs what explains the nearer timeframe.

The ECM would not develop like it does even if the pattern was less amplified later if it phased the shortwave in similar fashion to the UKMO at 120hrs.

Oh well on to tomorrow mornings model runs when surely we can at least get agreement in the earlier timeframe.

[shedhead]

That's quite a big difference at T+168 Nick between the main two. I think that anyone with experience has been here before and is wearing the t-shirt. I suspect that the amplification being played around with over the last few days will prove to be an exaggerated version of what will happen. As ever I will always go with the model that fits in with the background signals and tonight up to T+168 that is the ECM.

Very wise and completely agree chiono - going with the model that suits the background signals rather than the coldest evolution has never been the most popular way of doing things though, hence the perpetual rollercoaster that is Winter in the MDT! Only 3 days in and she's hurtling around at breakneck speed already.

Edited December 3, 2011 by shedhead

[phil nw.]

I must admit when i first viewed the GFS12z Op.run and saw the High building that far North i was suprised and then i viewed the GEFs and mean run later and was brought back down to earth.

I can`t see much change in the outlook for the coming week now.

Wrt slight differences in the nearterm modelling,yes a bit more amplitude would dig the Pm air somewhat further south but these brief flirtations would not deliver down here i fear.

If we look at the GFS mean run along with the ECM beyond 5 days there`s reasonable agreement for a mainly Westerly pattern, just North of West at times ,with the High pressure close to the South of the UK later.

Day 10 here

http://www.meteociel...M1-240.GIF?03-0

http://176.31.229.22...21-1-240.png?12

The cold air never really get`s to the far South and as usual in this type of zonal flow Scotland gets the lion`s share of any Wintry falls.

It will certainly feel colder for all next week but as often the case cool zonality rarely delivers for Southern and Central areas in terms of snowfall.

The trend after the unsettled spell is for the Azores High to build somewhere near or over the UK-latest NAEFs Anom. hts chart

http://176.31.229.22...s-0-0-240.png?0

and the CPC 500 heights outlook mean days 8-14.

http://www.cpc.ncep....y/814day.03.gif

This sort of setup has been fairly consistently showing for week 2-should feel quite cold at the surface with night frosts if the High builds like this.

Edited December 3, 2011 by phil n.warks.

[Richie V]

I can't wait to see the 18Z deliever another huge lump of dissapointment to you coldies.

I'd expect the 18Z's to start showing some really OTT Lp's now, Something is telling me we're on the brink of some spectacular windstorms at some point this coming week. I think rather than short notice blocking appearing there will be short term mega Lows appearing on this weeks gfs runs

On the 12Z there are prominent differences even at T+96! expect this to remain the case for quite some time.

[Uncle_Barty]

I'd expect the 18Z's to start showing some really OTT Lp's now, Something is telling me we're on the brink of some spectacular windstorms at some point this coming week. I think rather than short notice blocking appearing there will be short term mega Lows appearing on this weeks gfs runs

Why?

[Richie V]

Why?

In short....Seriously cold strat and the continued strenghtening of the PV

Edited December 3, 2011 by Richie V

[cfallon]

The far north of scotland currently getting hit by snow as we speak lets just hope over the next few days it pulls down to the north west! ;-)

Edited December 3, 2011 by cfallon

[Gibby]

Good evening folks. Here's a laymans guide to the operational output tonight supplied from GFS, UKMO and ECM.

GFS tonight looks windy and changeable over the next 7 days or so with strong West or Northwest winds bringing occasional spells of rain alternating with periods of showery weather. With temperatures frequently on the low side snow will fall on hills in the North and lower ground too at times. In the South snow should be restricted to the showery spells and the highest hills, moors and mountains of the Midlands, Wales and the Southwest. In FI High pressure takes control with cold and frosty conditions taking hold with freezing fog too, this weather type lasting in one shape or form to the end of the run.

The GFS Ensembles did not agree with the operational for London which turned out a cold outlier while the mean of the rest of the pack stayed quite close to the 30yr average. In Aberdeen the above run was much nearer the mean of the group from midway followng a period of below average 850's.

UKMO shows a windy week to come with strong West or Northwest winds with showers and afew longer spells of rain for all. the showers will be heaviest and wintry in the North and West while Eastern areas see fewer showers. Temperatures will be somewhat on the low side especially in the North where snow may lie on the hills. By next Friday high pressure nudges in from the SW bringing cold and frosty conditions to the South and West by next weekend.

ECM shows an often windy and unsettled 10 days or so ahead with rain or showers at times for all. In the North it will be cold enough for hill snow, especially early next week when this could extend to lower levels. With time the model shows a more westerly flow restricting the colder uppers and pushing the snow level up to the mountains of the North.

In Summary things remain unsettled from the models tonight. Without ever being really cold temperatures will be somewhat below normal with some snow possible in the North especially early and late next week. GFS and UKMO look like providing a chance of higher pressure next weekend with frost and fog patches possible in the South then. However, ECM has none of this high pressure developmemt, instead keeping things changeable and bringing somewhat less cold conditions in from the West.

[A Winter's Tale]

The far north of scotland currently getting hit by snow as we speak lets just hope over the next few days it pulls down to the north west! ;-)

Wintry showers in the central belt aswell!

I have to say that I'm impressed with the models for next week. Sunday and Monday looking good for snow, Tuesday morning and lunchtime look good aswell with slightly colder uppers and then we have the end of the week aswell! It just makes me wonder, if it's wintry right now, what on earth will it be like next week with far cooler uppers. I also expect some low nightime temperatures in parts of Scotland. Also I'm interested to see what the showery activity will be like in the coming days as today showers in Scotland have travelled quite a bit east and have been heavy and regular aswell.

[weathe20]

In short....Seriously cold strat and the continued strenghtening of the PV

Dosent mean anything. Whats happening now? We have more and more cold shots appearing in the models. If the weather was as easy to forecast as you suggest then whats the point of this thread?

[SNOWPLOUGH]

FI is definitley +96 hrs at the moment, I stiill cant believe how much cold weather the models are projecting when you take the teleconnections into consideration.

Dan

Edited December 3, 2011 by Paul
Removed personal comments

[lorenzo]

http://176.31.229.22...fs-0-126.png?12

there ya go Richie - sub tropical it aint ! Just a nudge from FI yes but hey look what this pattern is serving

[Richie V]

http://176.31.229.22...fs-0-126.png?12

there ya go Richie - sub tropical it aint ! Just a nudge from FI yes but hey look what this pattern is serving

Firstly, my comments we're in reference to tonights 18 Z onward not 12Z.

2. Where did I make reference to it been mild (subtropical)

3. T+96 is FI at the min let alone the cherry picked T+126 hrs chart in your post.

The pattern 12 Z is "serving" is liabale to severe changes even at your belovid (Chosen by you range) T=126 chart

[TonyH]

My take on the coming weeks output and resultant weather (west Wales and central MIdlands specific)

For supportive charts see here:

http://forum.netweat...n/page__st__220

Guide to the weeks weather Sunday 4th to Saturday 10th December (west Wales and Midlands specific)

Headline: Rain or showers at times, quite cold early and late in the week, some snow for high ground

Autumn 2011 was the second warmest in the central England temperature series that goes all the way back to 1659, with only 2006 being warmer. Rainfall wise for November, it was rather dry, with 93mm falling on Llanwnnen, 45mm on Coventry and just 31mm on Rugby (only half the average here). Maximum temperatures below 5c early and again late this coming week will be a shock to the system with a bit of a taste of Winter!

Sunday to Tuesday southern Britain is in a rather cold west to NW flow of air, this originating over the Canadian Arctic, although greatly warmed by its long passage across the Atlantic, and nowhere near as cold (or snowy) as Scotland will be. Quite windy with showers at times for most of us, these most frequent for west Wales and during Monday, with fewer reaching the Midlands, unless the 'Cheshire gap' allows them through, and more in the way of dry bright weather here. Showers will be heavy at times, with hail quite a feature for west Wales, and snow for the hills, more especially Snowdonia and the tops of the Cambrians, although it is unlikely that Lampeter will see more than a few wet flakes. Frosts could well be a feature given clear enough skies and lighter winds during the Sunday and Monday nights.

It turns milder Tuesday night through to Thursday but still quite windy, with some more rain at times, but dry brighter intervals too.

A great deal of uncertainty in the model outputs for the end of the week, but it looks as though another short lived colder snap arrives with more wintry showers of rain, hail, sleet, and snow for the hills again, with overnight frosts returning too.

ECM

maintains the procession of cool lows from the WNW next weekend, while

GFS

moves high pressure towards western Britain, however the

GFS

runs have been fluctuating wildly recently, so the more unsettled theme could be back by the pub run!

Edited December 3, 2011 by TonyH

[ukpaul]

Firstly, my comments we're in reference to tonights 18 Z onward not 12Z.

We haven't had the 18z, does someone have access to a crystal ball?

[Snowmadsam]

We haven't had the 18z, does someone have access to a crystal ball?

Sorry, mine fell off a cliff.....looking forward to 18z.....