Model Output Discussion 26/08/2012

[Bristawl Si]

Just had a trawl around your website, Gibby - absolutely fascinating - loved your piece on different cloud types.

[Cloud 10]

Please keep on topic. We are still 3 months away from winter.........

12 weeks sounds better...

Or maybe less?

http://modeles.meteo.../cfs-0-1872.png

[Frosty.]

It's good to see the gfs and ecm 12z in broad agreement about high pressure rebuilding eastwards across the uk next week after a bit of a blip on sunday, the major difference about next week would be the inclusion of scotland and n.ireland in the fine anticyclonic weather as the high is being modelled rather further north crucially although it's not looking as warm as the next few days are going to be, but even that could upgrade nearer the time. This spell of widespread high pressure being shown on the 12z's is in conflict with todays meto update which was for unsettled weather in the north and west to gradually erode the fine and warm start for the south and east during next week.

Edited September 4, 2012 by Frosty039

[Iceaxecrampon]

First Scandi snow? - albeit low percentage but there you go.

Chilly in the Glens and on the tops.......

[Iceaxecrampon]

Please keep on topic. We are still 3 months away from winter.........

Even so isn't this a Model Discussion?

[NorthernRab]

Even so isn't this a Model Discussion?

Not long term / FI.

[Eskimo]

Is there a separate thread for FI charts? Would be handy for those who would like to see what winter has in store (albeit at long range).

[peterf]

best to say nothing, and just use the extra which is great.

[Frosty.]

The Gfs 00z operational run is showing another anticyclonic spell developing through next week but with a more unsettled interval early next week with mon/tues being generally cooler with some rain and showers and nw'ly winds but soon followed by a ridge as the azores/atlantic high forms a high over the uk by midweek onwards, eventually a large scandi high is the result and the weather remains settled for some time although as the high moves further east, low pressure to the northwest begins to affect the far north and northwest by the end of next week and further into FI shows a gradual change to generally unsettled and windier weather but still with high pressure to the south. The Gfs ensemble mean has a watered down version of the high shown on the op run, more like a ridge really and mainly affecting the southern half of the uk and then further on towards T+240 hours is looking more and more unsettled and also cooler.

[Gibby]

Good morning folks. Here's my take on this morning's 00z output from GFS, UKMO and ECM.

All models suggest a decent 3-4 days as High pressure transfers slowly East over Southern Britain through the next few days. Northern areas will stay a little breezier with a West wind feeding cloud and some rain in the far North over the next 48hrs. By Sunday a front moves slowly into the UK from the West with rain for most as it trundles East through the day.

Next week sees GFS rebuild High pressure near the British Isles with things turning drier and brighter again. It will not be as warm though with cold nights bringing a risk of fog and a touch of frost for a while chiefly in the North. Late in it's run the weather turns more unsettled as Low pressure moves in off the Atlantic late in the run

The GFS Ensembles still show the 11th as the day of change to lower 850's closer to the long term mean as Low pressure becomes more dominant and the risk of rain increases in all areas.

The Jet Stream continues to blow East close to the far North of the UK before next week disrupting and breaking up somewhat as a new arm develops moving out of the states later next week.

UKMO looks the most unsettled model in its timeframe this morning as a Low pressure North of Britain extends an active trough down over the UK as it drifts only slowly East on Monday. Outbreaks of rain look likely on both days but taking a fair while to reach the far East.

ECM pushes the trough eastwards quicker on Monday with a deep Low developing in the Norwegian Sea midweek blowing a strong Westerly flow over the UK with more mobility to the weather as troughs cross East bringing rain at times with the heaviest of this being to the North as High pressure remains reasonably close to the SW. It will become cooler everywhere once this pattern sets up.

In Summary the weather remains set fair until Sunday with high pressure crossing slowly East over Britain. Next week the confusion still remains in the models in how they handle the exit of the trough bringing the change next Monday and how the following High pressure interacts with a Low pressure near Iberia or the Azores. GFS has the High moving East over Britain keeping things set fair while ECM collapses it South by low pressure to the North bringing a mobile Atlantic feed in for a while. In any event ECM too brings High pressure into the SW at the end of the run returning fine and bright weather to the South at least in time for next weekend. I think we shouldeExpect some more changes in the 12z tonight and tomorrow before a true coming together of the models for next week evolve.

[Gavin Hannah]

06 GFS run firming up on the idea of a cold incursion next week as early as Monday for Scotland with 0 deg uppers which slowly moves south over the UK by thursday. A good chance for snow on the mountains with some proper chilly autumn weather. Some -5's sneaking into the north half of Scotland too....

The deep depression swings north and into Greenland and away from the UK on this run.

FI shows a massive ridge out in the Atlantic although it doesn't stick around long. FI was looking rather messy actually.

Edited September 5, 2012 by IBringTheHammer

[Frosty.]

It was a relief to see that the Ecm 00z operational run was at the unsettled end of the ensembles and that the ensemble mean looks rather better with a ridge across at least the southern half of the uk later next week (similar to the gfs ensemble mean) but the models have firmed up this morning on a more unsettled first half to next week with a trough to the north in control, later in FI looks more generally unsettled but even by T+240 hours it may still be reasonably dry and warm at times in the far south/southeast with a weak ridge persisting but much more unsettled further north and west.

[bluearmy]

however the 00z ecm op is an outlier re uppers next weekend so at this stage its fi placement of the block is suspect. not picking on you in particular as you aren't one for doing this too often but too much dissection and analysis of fi op runs can be quite misleading for those less knowledgeable who may come on here looking for some guidance re week two.

whilst the ecm op runs last weekend were indeed correct to push high uppers across much of the uk, they were over optimistic in their subsequent placement of the block. therefore both the ops and ens were right !!!

[Paul]

The GFS has had a small update to improve temperature forecasts today.

Effective with today's 12Z run of the GFS, NCO has implemented a

correction to the GFS 2m temperatures and sfc moisture. EMC was

notified that the GFS forecasts were too cold and too moist in recent

months. Investigation by EMC developers found the problem was

introduced by erroneous land-surface model tables introduced during

the last major GFS upgrade. The correction removed the warm-season

cold temperature bias and high moisture bias, and significantly

improved GFS precip forecast skills over the CONUS, especially for

light rain. The change has no significant impact on other forecast

skill metrics such as 500 mb height anomaly correlation, hurricane

track and intensity, or cool-season forecast metrics. GFS MOS

temperature and dew point guidance are improved due to the corrections

in the GFS.

[AWD]

Well, according to the 12z GFS, at just T120 we have the first Autumn storm for the northern half of the country, Scotland especially.

Severe gales & rain, a world away from previous output at that timescale.

Would urge caution at anything past T96 currently as there are large variations between model runs!

[Frosty.]

The Gfs 12z op run is very action packed early next week with a vigorous depression hitting northern britain, the south mainly avoids that trouble but then the second low moves in by midweek albeit much less intense, more of a showery trough, pressure then rises as a ridge topples eastwards across the south and pressure then remains fairly high across the far south whereas central and northern uk are progressively more unsettled and windy but then we have another anticyclonic spell which looks almost a carbon copy of the current one with temps well into the 70's once again in southern britain. It's fair to say the outlook the models were showing yesterday has changed considerably.

[Gibby]

Hi Folks. Here's the evening look at the 12zs from GFS, UKMO and ECM.

The models show High pressure situated over Southern Britain fairly slow moving currently but drifting slowly east away into the continent as we move into the weekend. the far North continues to be influenced by a Westerly flow with fronts entrained across the far North giving some rain for a while in the next 36 hours or so. As winds turn Southerly towards the weekend temperatures will rise to the very warm category especially in the SE.

GFS then takes us into the first half of next week with a major storm system North of Scotland with gale and severe gales likely for exposed areas of Scotland with rain at times for most too as troughs cross quickly East in the flow. From then onwards the basic pattern of High pressure to the South and Low pressure to the North remains with rain at times though the South could see some drier and brighter spells as transitory High pressure passes over. Needless to say the temperatures will tumble to near normal values at best through this unsettled phase.

The GFS Ensembles show a marked fall to below normal 850's on the 11th before a slow recovery to slightly above average 850's return late in the run. The operational was a warm outlier at that point though. Rainfall amounts increase in amount and frequency from the 11th but decrease again in the South late in the run.

The Jet Stream shows the current West to East flow near Northern Scotland become much more undulating as we move through the following week or so.

UKMO for Tuesday at Noon shows a deep Low North of the Faroe Islands dominating the UK with Westerly winds and showers or rain at times the most likely weather experienced. A slack Westerly flow in the South will probably keep things drier here unless a slow moving trough from the Low to the North ripples over the South to enhance the chance of possible rainfall.

ECM shows a more mobile setup next week as a deep area of Low pressure remains North of Britain for much of the week. With fresh West winds and troughs moving through rain will always be a risk at times though some drier and warmer intervals could develop in the South at times.

In Summary the pattern is slowly becoming a little clearer next week. Low pressure is now shown by all models to be the governing factor with Westerly winds blowing strongly at times as disturbances run West to East in the flow. Temperatures will return closer to normal with a rather cool feel in the fresh breezes.

[ANYWEATHER]

Been looking for a while now to see what the period for next week is likely to be and for the last several days there has been a messy outlook from the models as to where and when! It does look however ,that a general breakdown in the weather is likely from Sunday although even at this stage certainty needs a lot of caution! The tropical storms out in the North Atlantic make a mockery of the computer models at this time of year!

[phil nw.]

Next week looks like evolving into a typical +NAO pattern with transient ridging and troughing becoming increasingly mobile with time as the mid latitude high becomes squeezed further south.

GFS mean and ECM Op.run from the 12z show the increasingly changeable pattern around next mid-week

In the meantime the current High will continue to give many of us sunshine and decent temperatures until the weekend at least.The far north somewhat less settled though.

Edited September 5, 2012 by phil n.warks.

[Sunny Android]

Thanks to Gibby and others for the analysis, although I'm not looking beyond the weekend since FI is 120hrs for me at present !

There is nice agreement with MetO and GFS on the pressure drop in this locality. Between 12noon Sat to 12noon Sunday, it's quick, a little too quick for my liking, both dropping 15mb.

[Gavin Hannah]

Far too much variation in the latter stages of each run so Anything past Sunday is open to change. I'm going with the idea that the likely outcome for the start of next week is the cold incursion from the north which will bring colder air across the UK for most of next week.

[Scorcher]

Far too much variation in the latter stages of each run so Anything past Sunday is open to change. I'm going with the idea that the likely outcome for the start of next week is the cold incursion from the north which will bring colder air across the UK for most of next week.

I think the likely scenario at the moment is for a brief cooler incursion for the north on Tuesday and Wednesday before warmer air again moves in from the south west. I can't really see it lasting the whole week. Even GFS is showing a warm up from Thursday and it's had a tendency to come into line with ECM recently rather than the other way round. If the ECM 12z is on the money most of next week will be warm for the south. The far south may not get that cool at all.

[Frosty.]

Far too much variation in the latter stages of each run so Anything past Sunday is open to change. I'm going with the idea that the likely outcome for the start of next week is the cold incursion from the north which will bring colder air across the UK for most of next week.

I wouldn't use the words cold incursion to describe what the models show next week, yes it will become cooler and more unsettled after the weekend until around midweek but then probably some recovery in temps will occur.

[Gavin Hannah]

Ok so cold incursion is probably a bit extreme lol. But depending on how it goes, a chance for some snow on the mountains and some frosty mornings in the north,

[Mark Burton]

Not happy with the models slowly but surely downgrading Saturdays weather in the Lake District. Every run sees a gradual downgrading in conditions - all models seem to be in agreement with this too. Important wedding in Windermere on Saturday!!