Model Output Discussion - Late October Onwards

[phil nw.]

The ECM is more in line with what I would expect here. The latest (06Z) GFS run doesn't appear to agree with the mean heights and GFS FI starts around the 27th.

Yes i think thats a fair assesment C.

In the short/medium term it seems to make little difference to our weather on the ground as i indicated.

We are in Phase 2 now of the MJO and if i am reading the composites correctly it does suggest the Atlantic troughing remaining close to our West as we enter November.

The block holding further North and East than suggested by the GFS 00z mean hts.

Edited October 22, 2011 by phil n.warks.

[TonyH]

My take for the next week, contrasting west Wales with the Midlands:

Headline: Mild, some rain at times, mostly for west Wales

A complex low pressure system is waiting over the near Atlantic attempting to bring welcome rain to the Midlands, however a large blocking high over Eastern Europe looks likely to restrict this. However troughs do eventually cross all parts bringing some rain, but most this week for west Wales.

For Sunday and Monday a deep, very mild southerly flow covers the UK, While west Wales sees a little rain at times on Sunday, the Midlands should stay dry and will brighten up and become warm for late October, up to 18c perhaps. A windy day for all. Monday is even windier with further rain at times for the west, some perhaps heavy, this possibly reaching the Midlands later on too, and very mild again for all.

On Tuesday the front manages to cross all parts, while it turns showery behind over Wales. Lighter winds, and less mild. Wednesday looks like a day of sunshine and scattered showers, mostly for west Wales and a touch cooler again.

Differences in what the models see for later in the week:

ECM

keeps relatively low pressure close to the UK, so always the chance of showers but with dry, sunny spells between, and probably few showers for the Midlands.

GFS

builds a ridge of high pressure across from the east, so that all of us turn dry and quite mild, although there could be ground frost in places overnight.

By next weekend a new Atlantic low pressure is attempting to force the high block but seems to struggle once more, so that any rain looks likely in only reaching west Wales and it becomes very mild once more:

Edited October 22, 2011 by Tonyh

[Backtrack]

Uppers of 12C over some of the UK on Monday. Could be a lovely warm day.

[J10]

http://www.wetterzen...Rmgfs144sum.gif

This chart seems to back up the points made by TonyH above, a lot of rain in the west not making it that far east. One proviso with these charts, they do tend to overstate rainfall being based on GFS.

At times like this I miss the Walkers rain comp.

[summer blizzard]

The model divide continues..

ECWMF and GEM have the high being pushed out of the way resulting in low pressure closer to the UK.

GFS suggests that the high will remain strong even if it does sink and thus keeps England at least dry.

[I remember Atlantic 252]

http://wetterzentrale.de/pics/Rtavn2161.html hope GFS is overdoing that low, looks horrid, only 31 0ct I suppose but certainly dont want that in winter

[J10]

http://expertcharts....102412_2212.gif

NAE suggests a very wet next 48 hrs in Ireland and Western Scotland, There is potential for this to happen In Wales and SW England as well.

[bobbydog]

interesting to note, the 12z GFS has the jetstream taking a slightly more southerly track, consequently the cold boundary is further south. i know its only one run but worth watching to see if the models pick up on this

[Gibby]

Good evening. Here's a lightning trip through the 12zs tonight from GFS, UKMO and ECM.

GFS tonight shows Low pressure West of the UK and High over Europe with a strong and very mild or warm Southerly flow over the UK. After mostly dry conditions tomorrow the East and South see plenty of dry weather while the North and West see some heavy rain, especially in Northern Ireland and SW Scotland. Through Monday gales and heavy rain push East through the UK becoming lighter as it goes meaning probably not much for the far East. Then, after a couple of unsettled days pressure builds back once more from the East with a return to breezy and very mild condiions late in the week with some rain at times once more in the West and North. In FI tonight conditions become more mobile with Low pressures moving East Northeast to the NW driving fronts with wind, rain and less mild conditions through all areas on various occasions.

In the Ensembles there is a lot of scatter between the group from both London and Aberdeen with the overall balance keeping things close to the long term average.

UKMO maintains High pressure over Europe with Low pressure to the West. The High pressure to the east releases its influence for the early days of next week as deep Low pressure runs North just to the West. Strong to Gale Southerly winds would bring heavy rain to the far West and NW tomorrow before extending rain to other areas early next week. Once passed a period of showers and lighter winds dissolve into a synoptic setup by the end of the week not too dissimilar to where we are now with mild SW winds and rain for the NW while the South and East stay dry and bright with perhaps some overnight mistiness in the SE.

ECM follows the UKMO route with the progression from next Friday being that we enter a much more mobile phase with deep Low pressure moving West to East north of the UK with periods of rain and showers with strong winds and lower temperatures by the end of next weekend.

In Summary there is some agreement between the models tonight. After some heavy rain for a while for most early in the week the trend is for things to become more settled again in the second half of next week. There would be some sunny spells in the South and East although unsettled conditions would hold on in the NW. Later in the week and onwards both GFS and ECM show a more mobile setup looking likely as deep depressions pass to the North with gales and rain at times for all.

[Liam J]

GFS & ECM 12z runs show a very unsettled outlook with depressions developing over the Atlantic and racing towards the UK, Potentailly very stormy on the GFS which seems to have dropped the more settled outlook it had shown previously.

[SP1986]

The GFS 18z definitely slackens things up, bringing a risk of air frost for Northwest England in particular by Thursday/Friday. Certainly not a jet sweep, with high pressure having a big influence. However I'm not sure I buy into it, and just for the sake of accuracy, I'd probably side with ECM anyway

[Isolated Frost]

Cold again in lapland, southern Germany/northern Austria/Switzerland and in eastern europe. Low pressure system just sw of britain and nw of britain - and strengthening hp block in e europe.

[Gibby]

Good morning. Here's my take on the 00zs from GFS, UKMO and ECM for today.

GFS shows Low pressure moving North close to the West Coast early this week followed by rising pressure once more from the east, possibly returning synoptics not too dissimilar to now for next weekend. In weather terms some very wet conditions look likely for the extreme west for today and tomorrow, though with dry continental air flooding North from europe further East the weather will stay dry for many with strong winds but mild conditions. Through Tuesday a narrowing band of heavy rain would move NNE over the UK followed by brighter, less windy conditions with scattered showers. Then things would dry up for many with mild South or SW winds to end the week and weekend as High pressure builds back from Europe. The far West and NW would continue to be at risk from rain and with time this is shown to extend to other areas through early November.

The Ensembles show the 850's being fairly close to the long term mean for the period with the operational fairly representative of the pack with only small deviation towards the end. The rainfall shows a short spike from the 25th -27th before the next rain risk occurs from the 30th or 31st. In Aberdeen the theme is fairly similar with temperatures above normal for most of the period.

UKMO also shows a wet start to the week for westernmost areas with a band of heavy rain swinging NE late tomorrow and Tuesday through all areas followed by less windy and more showery weather. High pressure then begins to build back from the east with drier quieter conditions for a day or two with lower temperatures particularly at night. By next weekend we return to mild Southerlies taking hold with rain for the far west and North again as pressure falls to the West.

ECM finally brings us into a more progressive scenario towards the final part of its run with deep Autumn Low pressure winding up to the NW by the final day bringing gales and heavy rain to all areas. Preceding that this week is shown to be similar to the other models in rain giving way to drier conditions later in the week.

In Summary today the pattern looks fairly set from the models. This week will see wet weather early in the week giving way to drier and mild conditions again for many away from the far West and North. In the extended parts of the output of GFS and ECM more progressive weather is shown to develop as the Atlantic to the NW ratchets up a few gears and sweeps troughs East through the UK on a cooler and still strong West or SW flow. Frosts and anything wintry look completely remote in the next two weeks on this morning's output.

[Liam J]

ECM 0z sticking with the unsettled outlook, perhaps a brief period of a few days that are more settled with a temporary ridge. LP quickly takes charge again, ECM has been the most consistant with this outlook and I'm sure if the UKMO model went out a bit further it would be showing similar. GFS chops and changes to much atm in the mid-long term.

Edited October 23, 2011 by Liam J

[Snowmad79]

Models starting to firm up on decaying the HP block to our east. Would rather see LP to our immediate NE/E right now rather than HP becuase that would just keep us locked into a Westerly/ SWesterly regime and I think we'd have more chance of troughs & ridges setting up in more favourable positions.

Is is right to say that a more mobile trough/ ridge pattern (aided by rossby waves kinking & buckling the jet around the globe), with bursts of warmer air up north over Svalbard into the artic as shown on the models up to 240, helps to disrupt or weaken the PV ? Sure I read in wikipedia that SSW isnt the only factor.

Edited October 23, 2011 by Snowmad79

[J10]

http://expertcharts.weatheronline.co.uk/daten/proficharts/en/nae/2011/10/23/basis06/ukuk/rsum/11102506_2306.gif (NAE)

NMM shows the potential for equally heavy rainfall.

Chance of extremely heavy rainfall over the next 48 hrs, currently pinpointed for the far West of Wales, SW England and SE Ireland, but exact focus is always liable to change.

[weathe20]

Cold again in lapland, southern Germany/northern Austria/Switzerland and in eastern europe. Low pressure system just sw of britain and nw of britain - and strengthening hp block in e europe.

Models starting to firm up on decaying the HP block to our east. Would rather see LP to our immediate NE/E right now rather than HP becuase that would just keep us locked into a Westerly/ SWesterly regime and I think we'd have more chance of troughs & ridges setting up in more favourable positions.

Still learning here, but these two posts seem to contradict eachother??

[lorenzo]

Weathe20 too different systems are being referred to here.

The first is the HP system reaching 1030 hpa in far Eastern Europe, the other is the Scandinavian High.

[Snowmad79]

Yeah sorry about that, should have been a bit clearer in what I was refering to:

The HP over Europe and Scandi sinking southeast leading to much more flater pattern:

Isolated Frost was talking about the strengthing in the next 48 hrs of said blocking high pressure, where as my post refers to 48 hrs to T240 time frame. You can see in the images above how the HP sinks and the ridge is pretty much flattening out. This was shown on yesterday evenings model output and todays so far.

Hope it continues with the 12z's coming out now.

Apologies again

[Gibby]

Good evening folks. Here's a look at the 12zs from GFS, UKMO and ECM

Up to 144hrs.

All models show deep Low pressure just west of Britain and High pressure over Europe. A strong Southerly flow blows over Britain with an active trough lying North to South over the extreme west. This moves slowly NE to affect other areas over late tomorrow and Tuesday. In the meantime Western and Southwestern parts (principally Cornwall and Pembrokeshire) could see problematic copious rainfall. Then as the rain clears away NE showers follow on Tuesday and Wednesday with the chance of more rainfall feeding North on Thursday. Late in the week a ridge of high pressure gives most of the UK a decent day on Friday before further rain reaches the NW on Saturday.

Beyond 144hrs

GFS in FI tonight keeps High pressure close to the South with only a little rain at times while the North sees the usual mix of rain and brighter spells and the strongest winds. Late in the run High pressure moves away East with Low pressure moving into the UK from off the Atlantic with nearer to normal temperatures.

Tonight's GFS Ensembles show typical mobile Westerly type weather developing from next weekend. The control run falls through the floor towards the end of the run for London while in Aberdeen a similar pattern of a gradual fall in 850's occur with once more a noteworthy cold outlier shown by the control run.

UKMO at 144hrs shows Low pressure feeding back in off the Atlantic bringing strengthening winds and rain to most areas in the days that follow.

ECM turns distinctly unsettled from next weekend with deep low pressures moving west to East to the North and then into the UK at 240hrs. The weather would become wet and windy at times for all with gales and temperatures rather lower than of late.

In Summary things look quite unsettled and seasonal tonight. Over the next few weeks it looks from tonights output that all areas can see at least some rain and strong winds and for some areas rather a lot of both. As usual in these situations there will be some shorter drier interludes notoriously for the south and East towards next weekend. With time the South and East will join other areas in seeing temperatures falling back to levels nearer the seasonal normal.

Edited October 23, 2011 by Gibby

[feb1991blizzard]

GEFS control run keen to build heights over Greenland extending down into the atlantic and an interesting T288 onwards perhaps giving some wintry showers for the east, zero chance of it veryfying though as its an outlier against the rest of its suite but good to just see some charts remotely approaching cold after the rubbish we endured the second half of last winter.

http://www.meteociel...ode=0&runpara=0

Edited October 23, 2011 by feb1991blizzard

[kold weather]

ECM places the upper trough a good deal further east than the GFS and keeps us in an active and quite stromy pattern. Its not an unreasonable forecast and I think we will have some sort of LP dominance at some point, its just when that happens really.

[bobbydog]

the GFS run is overall a very repetetive pattern. assuming this pattern stays in place indefinitely, as we move into the winter months, with reduced sunlight and increased cold, would i be right in saying it should 'evolve' or alter accordingly? if so, in what way could this happen?

[damianslaw]

All models show current heights out to our east will gradually sink southwards as the week wear on, enabling a much flatter jet pattern to develop and consequently allowing frontal activity to reach the east. Thereafter - signs of a very unsettled start to November are emerging especially from ECM this evening. Vigorous low pressure development is being shown thanks to a very active atlantic - its been dying to stir into at least fourth gear for ages and I believe ECM is onto the right theme.

Autumn has been an exceptionally benign affair so far away from the NW quarter of the country - and many in the SE really could do with the rain, however, much those in the SE don't want it. If ECM verifies some very useful rain will be delivered to the whole country as we enter November and quite likely some very stormy conditions.

On a personal note - I would rather see the back of the current pattern we are in, I don't normally want the jet to power in, but I would rather it did it now than in a months time when chances of proper cold and snow become much more real - the charts do remind me of this time in 2009 it has to be said - but I hope we don't see the rain we saw in Nov 2009.

[feb1991blizzard]

All models show current heights out to our east will gradually sink southwards as the week wear on, enabling a much flatter jet pattern to develop and consequently allowing frontal activity to reach the east. Thereafter - signs of a very unsettled start to November are emerging especially from ECM this evening. Vigorous low pressure development is being shown thanks to a very active atlantic - its been dying to stir into at least fourth gear for ages and I believe ECM is onto the right theme.

Autumn has been an exceptionally benign affair so far away from the NW quarter of the country - and many in the SE really could do with the rain, however, much those in the SE don't want it. If ECM verifies some very useful rain will be delivered to the whole country as we enter November and quite likely some very stormy conditions.

On a personal note - I would rather see the back of the current pattern we are in, I don't normally want the jet to power in, but I would rather it did it now than in a months time when chances of proper cold and snow become much more real - the charts do remind me of this time in 2009 it has to be said - but I hope we don't see the rain we saw in Nov 2009.

I certainly expect all models to firm up on a stormy spell and although i am a firm beliver that the right synoptics could bring a potent cold spell as early as the beginning of November, they rarely seem to happen, 1993 was about the earliest, i seem to remember some heavy snow showers for the east just after mid month but apart from that and last year i dont remember many Novembers full stop that have delivered, maybe one other in the 90s.