Model Output Discussion 26/10 2012 >

[Alex]

Nice to see people optimistic this morning but I think some are over egging it, the GFS ensembles for the 00z tell the story, below average temps now becoming average with time, continuing unsettled. The ECM 00z looks similar to the GFS with the PV setting up shop to our north and a ridge setting up to the west of us but not too far away to influence things maybe cold and dry - mid November?

http://www.wetterzentrale.de/pics/MT8_London_ens.png

[BLAST FROM THE PAST]

Concentrating on the near time and all three are pointing at a very vigorus secondary LP to zip across the southern part of the UK on 2nd Nov. With a feature like that some very strong winds could be had along its southern flank which means southern counties could get near gale force winds with locally gale force on coasts. I suspect that there'll be quite a fair bit of rain associated too and already wet ground could lead to some issues. The main trough stays close to us throughout the whole reliable timeframe and beyond. Will this secondary LP or SW develop and track across the south? I know the MetO are watching the feature. Last one though turned out to be a damp squib fortunately as it didn't really develop and went off into France.

UKMO

ECM, see it developing SW approaches of the UK

24 hrs on and it nhas developed and tracked across and sits off Holland

GFS, which goes on to bring another LP up from Spain towards us after this one.

BFTP

Edited October 29, 2012 by BLAST FROM THE PAST

[Neilsouth]

I think we need to be thankful of that large high pressure across north eastern europe looking at those models!. Because i'm pretty sure with the direction of flow shown they'd be piling into europe and warming it up taking away the chances for winter

[Frosty.]

There has been a shift in the latest ens mean from gfs and ecm towards a gradual rise in pressure to the southwest of the uk during next week, high pressure looks like becoming centred to the southwest over the near atlantic but not close enough to bring a proper spell of anticyclonic weather, rather a cloudier wnw'ly moist flow with milder but mainly dry weather predominating during the outlook for the southern half of the uk as pressure slowly rises and low pressure becomes more confined to the far north of the uk, probably the only part of the uk that would remain unsettled in the set up being shown, however, it doesn't look like lasting for too long before low pressure to the northwest launches another attack and the later stages of FI look cold and unsettled with winds veering more towards the north with a cold spell further into november, cold and showery around the coasts but probably drier and sunnier inland but with widespread frosts. In the reliable timeframe, it looks like becoming very unsettled from midweek onwards with wet and windy weather mixed with sunshine and showers, both ecm and gfs show a brief cold snap with a showery nw'ly before pressure begins to rise from the southwest, so a chance of some wintry showers and night frosts later in the weekend or early next week before the trend towards less unsettled and rather milder weather begins to take hold.

Edited October 29, 2012 by Frosty039

[TonyH]

At least regarding possible flooding issues the Friday zipper is just that it does not hang around.

Edited October 29, 2012 by TonyH

[Methuselah]

This looks like an interesting chart. FI of course, that 1044 HP away to the ENE looks promising. Especially when considering how this year's snowcover is (hopefully) likely to develop?

http://nwstatic.co.uk/viewimage.pbx?type=gfs;date=20121029;time=06;ext=384;file=h850t850eu;sess=f9ed5d334d6b12f419b5fbc16e63b914;

[BLAST FROM THE PAST]

This looks like an interesting chart. FI of course, that 1044 HP away to the ENE looks promising. Especially when considering how this year's snowcover is (hopefully) likely to develop?

http://nwstatic.co.u...b5fbc16e63b914;

I think the snowcover has already develped Pete? Looking at the snowcover charts the last week has been mammoth, way ahead of last year an even ahead of 2010. Yes it caught my eye too and something to watch over coming week/s.

I personally do think the blocking is going to wax and wane this month and maybe beyond BUT I think that is at worst what will occur with the jetstream as it is

BFTP

[Isolated Frost]

Drop of sub 528 polar air at 144 on the UKMO.. look at them blocking heights developing o/Greenland + Scandi- ridge anyone?

Notable baffin low and N Pacific low (a la GP) on there- vortex certainly not weak, but relatively weak yes.. stratosphere still comparatively cold.

Overall view is cool zonality with some milder intervals, with the potential of a longer stretch northerly down the line.

[Methuselah]

I think the snowcover has already develped Pete? Looking at the snowcover charts the last week has been mammoth, way ahead of last year an even ahead of 2010. Yes it caught my eye too and something to watch over coming week/s.

I personally do think the blocking is going to wax and wane this month and maybe beyond BUT I think that is at worst what will occur with the jetstream as it is

BFTP

I guess I was trying, Fred, in an oblique kind of way, is that I hope that the snowcover doesn't suffer any major reversal...But, I don't want to have to delete my own post, for being off-topic!

Edited October 29, 2012 by Rybris Ponce

[sebastiaan1973]

I guess I was trying, Fred, in an oblique kind of way, is that I hope that the snowcover doesn't suffer any major reversal...But, I don't want to have to delete my own post, for being off-topic!

For the development of a negative AO (according to Cohen) just october values count. So a decrease in snowcover in november ain't a problem.

[TonyH]

Indeed all it's all very early Season.

[Frosty.]

An interesting update from the metoffice today, not at all what I was expecting having looked at the 00z ens mean from gfs and ecm, no mention of pressure rising with drier, milder weather encroaching from the southwest which the latest mean indicates, they are saying it will remain unsettled and windy at times with rain and showers and only shortlived drier and brighter interludes and temps continuing near or below average, so this is surprising.

[Thundery wintry showers]

The really changeable, low pressure-dominated weather looks set to arrive on Tuesday/Wednesday as a belt of rain will spread south-eastwards- Tuesday looks like being a wet day over most of Scotland and Ireland while Wednesday will be wet over most of England and Wales.

For Thursday and Friday, I can't help but feel that the synoptics would have provided a good example of "cold zonality" had it been later in the season, as we get 850hPa temperatures just above -5C coming right over from the west. As it stands, showers will fall as rain at low levels, with snow confined to high ground, though temperatures will generally be down on the seasonal average with highs of 6 to 9C by day and possibly some frost in central and eastern areas if winds fall light as suggested by the GFS. It is hard to pinpoint whether secondary lows will bring spells of persistent rain towards the weekend- the GFS shows quite a vicious low on Saturday but the ECMWF does not.

A northerly outbreak is likely when the low pressure complex eventually drifts away to Scandinavia but it probably won't be as potent as the one that we had last Friday/Saturday.

[Frosty.]

A quick look at the Gfs 06z op run shows some complications this weekend as a low forms to the southeast with a small core of milder air within the overall structure of the complex trough covering the uk, this low deepens and spreads up the east coast of the uk towards eastern scotland and acts to stall the invasion of polar air from the northwest which by friday looked like spreading across the uk, the colder 850's making inroads into the northwest corner of the uk by friday. It's sad to see that flood of arctic air and snow showers sweeping south harmlessly into the atlantic from iceland and once that small low has done it's worst, we are only left with a small pocket of displaced arctic air but a ridge builds into the uk bringing more widespread frosts at least to the north of the uk, a frosty bonfire night for scotland in particular, pressure then generally builds through next week with even a weak link up of the azores/scandi high and pressure remains high to the east for a time with some fine days and frosty nights, but pressure then falls dramatically to the northwest with a trough swinging southeast, eventually much colder with a brief northerly blast which soon topples as another ridge cuts off the arctic flow but leaves the uk in a pool of cold air with more frosty nights, then low pressure pushes east with some frontal snow which then turns to rain as milder air spreads in off the atlantic. This run bears no relation whatsoever to the latest meto update beyond the weekend or the 00z ens mean but it's still a very interesting run.

Edited October 29, 2012 by Frosty039

[SMU]

One for Liam & JS

Gridpoint for the NW now says snow..

S

& wales at 156...

All about the boundry & what the flow is & heights behind the zipper

S

[Isolated Frost]

GFS at D6 looks v interesting, meridional flow out of the US seaboard, and a meridional sub-t high.. it isn't quite UKMO 'northern linkup' at 132, but does have a easterly flow at 70N after D5, and injects that polar jet into britain by D6, very cold mid-tropo air, and a lack of zonality due to a ridging subtropical high and a supportive hemispherical pattern.

As a result, Bonfire Night looks pretty cold and wet at times, the 12z for the UK puts in a surface low at 162, leading to some rain o/ Southern England- chance of snow shrs on higher ground in Scotland and N England at times as well, generally cold and bright for many though, once that surface low has cleared- though plenty of convective activity possible in nw'ern parts.

and finally...

not a very zonal pattern projected by the ecmwf upper air charts today

some interesting waa being put into the arctic at 192, will be interesting to see the solutions from that..

Edited October 29, 2012 by Isolated Frost

[Isolated Frost]

This from the NW Extra suite, the hi-res NMM..

Vicious squall line on Halloween, big temperature variations in and behind it.. anyone for trick or treating?

[Isolated Frost]

UKMO at 144 persists with them polar heights, intensifying them o/ Greenland and even introducing a stable surface high o/ Novaya Semlya.

GFS completely disagrees with no heights o/ Svalbard/Scandi and a strong deep upper flow going down baffin island- another cross-model battle to go over the next few days, and the ECM tonight should be watched with close eyes.

[SMU]

As above commentary-

It has to be said that the GFS & ensembles have been very consistent with their handling of the polar heights modeliing in the 144 range- generally all suites have collapsed the block at day 6/ 7

UKMO is the only model persisting with the GH in situ ( notice the lows splitting over western greenland at 120)

The ukmo however has been equally consistent....

An early winter stand off on the models, the GFS is 1/0 I think V the euros based on last weeks episode-

lets see how they fair- history tells us that the GFS will be correct based on the last 8 -10 years model watching-

( just in this TYPE of evolution....)

s

[Chess01]

There seems to some kind of reload for cold around the 11th this has being showed on the last few gfs runs

[BLAST FROM THE PAST]

Its interesting as the UKMO persists with its evolution. Personally I'm liking what the GFS is showing bith on personal thoughts and the way it keeps us cool/chilly with visions of renewed blocking and the jet very amplified and remaining on southerly path in general. Looking forward to the ECM and future runs now as we have another interesting stand off.

BFTP

[A Winter's Tale]

Good evening. I haven't got much time but I'll do a shorter summary of the weather during the next few days. The clear skies should move further south during tonight with increased cloud cover in northern and western areas with a risk of showers. Quite a chilly night with lows of 2 to 10C and some patchy frost and fog in places.

Tuesday should see a north/south split with cloudier skies in the north and the west with rainfall for parts of Scotland; some clear spells in southern parts of England and the wet conditions continue overnight across north western areas but remaining dry and at times clear across the south east. Maximum values of 6 to 11C and minimum values of 4 to 10C.

During Wednesday and Halloween it seems that a heavy band of rain should affect areas surrounding the Irish Sea and into northern parts of England and southern Scotland. Some showers near the coasts, some sunny spells at times in northern Scotland and the very south east corner but light rain never too far away from London despite the main band being further west which will move eastwards overnight with showers following on behind. Maximum temperatures of 8 to 12C and minimum temperature quite chilly at 2 to 6C for many, 7 to 11C in southern England.

The band of rain should have clear into the north sea, leaving the British Isles cool on Thursday with some showers around western areas and a decent some sunny spells across western areas too. Maximum temperatures possibly 6 to 11C and a cool night with a touch of frost, some clear spells and thin cloud cover and showers affecting western areas. Minimum temperatures of 1 to 7C.

A cloudier day on Friday with quite thick cloud cover and little sunshine at all, still showers affecting western and northern areas but an area of more persistent rain set to move further move in bringing heavy rainfall to much of England and Wales overnight but Scotland at the moment should remain largely unaffected with showers continuing in the seas. Maximum temperatures of 6 to 10C and minimum temperatures of 2 to 9C.

Certainly an interesting and a very much autumnal week with plenty of showers, some chilly nights, a few sunny spells and band of heavy rainfall sweeping over the British Isles quickly - a very seasonal scenario and the outlook beyond also keeps a chilly, unsettled and autumnal theme.

[BLAST FROM THE PAST]

As above commentary-

It has to be said that the GFS & ensembles have been very consistent with their handling of the polar heights modeliing in the 144 range- generally all suites have collapsed the block at day 6/ 7

UKMO is the only model persisting with the GH in situ ( notice the lows splitting over western greenland at 120)

The ukmo however has been equally consistent....

An early winter stand off on the models, the GFS is 1/0 I think V the euros based on last weeks episode-

lets see how they fair- history tells us that the GFS will be correct based on the last 8 -10 years model watching-

( just in this TYPE of evolution....)

s

Steve

I have always found that if blocking breaks down a la GFS that its very encouraging to see the jet as it is with a very up and down pattern and LPs so far south, as a return to HL blocking is always on the cards down the line and not too far down the line either.

Particularly now as well that we are seeing the longterm continuation of a jet shifted south and meridional.

BFTP

Edited October 29, 2012 by BLAST FROM THE PAST

[phil nw.]

As above commentary-

It has to be said that the GFS & ensembles have been very consistent with their handling of the polar heights modeliing in the 144 range- generally all suites have collapsed the block at day 6/ 7

UKMO is the only model persisting with the GH in situ ( notice the lows splitting over western greenland at 120)

The ukmo however has been equally consistent....

An early winter stand off on the models, the GFS is 1/0 I think V the euros based on last weeks episode-

lets see how they fair- history tells us that the GFS will be correct based on the last 8 -10 years model watching-

( just in this TYPE of evolution....)

s

Yes Steve these little differences at relatively short range keep us on our toes.The continual fragmenting of the vortex challenging the modelling across the arctic at present.

[Snow and storms]

I believe this will be the equaliser for UKMO. In my opinion GFS seem to be the top model for noticing trends picking them up deep in FI and UKMO seem more accurate the nearer we get at pinning down the important details that make big differences.