Model Output Discussion 26/10 2012 >

[Cold Winter]

NAE has the rain intensifying slightly as it passes to the east during tomorrow, which explains why the GFS is picking up higher totals in the east:

EDIT: Having said that, the precipitation accumulation totals for the next 48 hours is still greater in the north and west according to the NAE, apart from a little patch on the south coast. Cumbria/North Wales and western Scotland look set to get the most rain.

Edited October 30, 2012 by Cold Winter

[Tim Bland]

Strikingly, the ensembles seem to show more rain on the eastern side of the country with both the north and west being drier/less wet.

Also worth noting that the Op was a slight mild outlier in FI

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

http://www.wetterzentrale.de/pics/MT8_Dublin_ens.png

http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png

[AWD]

GFS persistent with a secondary low forming in the channel and heading east. Worst of the winds again reserved for the French though, just clipping SE England later on.

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=72&mode=0

[A Winter's Tale]

Good afternoon. Today there has been a north/south split with some rainfall across parts of Scotland and overcast skies whereas in southern England a much drier picture with some periods of sunshine. Tonight we see a band of persistent and heavy rain arriving in western Scotland and Northern Ireland and during the night this band of rain should move south eastwards crossing Ireland and reaching western north western England and western parts of Wales. Some showers should follow behind the front. Wednesday morning should see the band of rain affecting areas around the Irish sea and north eastwards into eastern parts of Scotland showers moving in behind in the front in western parts of Ireland and Scotland and southern England should remain dry with some breaks in the cloud cover until evening. Through the afternoon and evening, as the band of rain moves eastwards affecting the western parts of England and Wales, some clear skies should develop across Scotland and Ireland but still the continuing threat of showers here. During the evening and through the night the band of rain will move eastwards bringing rainfall to inland, central and southern parts of England then eastern areas before clearing into the north sea early on Thursday. Clearer skies skies across Ireland and Scotland with showers in the west. Maximum temperatures should be 7 to 11C and minimum values of 1 to 10C.

Thursday should be a much drier day as the persistent rainfall clears into the north sea. Widespread sunny spells could be likely for eastern areas in particular as showers continue to affect western areas and these showers will go quite inland. Maximum temperatures of 6 to 10C. Overnight, showers in western areas should continue whereas for north western Scotland some more persistent and heavy rain should arrive here overnight. Possibly cloudier in Ireland and Scotland with clearer spells for eastern areas. Minimum temperatures of 1 to 7C.

Widespread showers could be likely for Friday, particulary across some central and northern areas of England. But there should be some sunny spells, particulary in eastern parts of Ireland and Scotland and southern England. Threat of some rainfall near the far north of Scotland and showers continuing in the west of Scotland and Ireland. Maximum temperatures of 4 to 11C. Showers should be less widespread overnight on Friday and restrcited to parts of Ireland where skies here should be overcast. Across England and Scotland and eastern Wales there could be some good, widespread clear night skies for periods and a chilly night too with lows of -1 to 7C.

Saturday at the moment is looking like a day with less showers - some rain affecting the channel coast though. Out to the west of Ireland and Scotland should be the next batch of some persistent rainfall to arrive later - a mostly cloudy day for western Scotland and Ireland. Parts of eastern Scotland and southern England may enjoy some periods of sunshine during the day. A cool day too with maximum values possibly 4 to 10C. Saturday night should see rainfall situated over much of Scotland and parts of Ireland and south western England. Drier and possibly clearer conditions for inland areas of England and Wales. Another cool night too with lows of 1 to 7C.

The next few days are looking showery - particulary in western parts of Scotland and Ireland - however there should be some days of sunny spells for many of us and less in the way of widespread persistent rainfall - tomorrow should see the most widespread rainfall of the week - so this should make for some days of pleasant autumnal weather. One other feature of the next few days is for temperatures to be on the chilly side with some patchy frost and hill snow across northern hills at times. Interesting stuff!

[chionomaniac]

I have been away for a few days and have not been able to keep up with the models as much as I would have hoped but there is one noticeable thing that I have noticed upon reviewing this evening.

The polar vortex is set to increase in strength drmatically and centrally in the 4-7 day range. This is projected in every model but I will use the latest GFS run to demonstrate.

Day 4

Day 7 (vortex lowering of heights circled)

There is no surprise in seeing this - especially as the stratosphere has been cooling in line with average. The day 7 tropospheric vortex even though it has strengthened it is by no means as strong as we have seen it in the past.

So what will this mean after day 7?

My guess is that the AO and NAO indices will move towards neutral. Any Rossby wave train will have to be twice a strong to keep the meridional pattern that we have been seeing persist throughout November. My guess is that we would see some more flattened (less amplitude) meridional pattern for a while yet, especially if the MJO wave loses amplitude.

http://www.cpc.ncep....clivar_wh.shtml

Talking of the MJO, there is promise here in the forecasts - avoidance of phases 3-6 is welcome at all times!

Edited October 30, 2012 by chionomaniac

[Snowy Easterlies]

hmmm, after an upgrade on the overnight runs, the 12z GFS looks like its want to collapse that mid atlantic ridge over us, like it was showing on yesterdays 12z runs, garden path springs to mind

UKMO looks a bit better for the weather to remain chilly, but im not qualified enough to judge what would happen after T144

Edited October 30, 2012 by Snowy Easterlies

[Zenarcher]

I made a post regarding the unsettled weather ahead for Wednesday and Friday here http://forum.netweather.tv/topic/74373-atlantic-storms-autumn-2012/page__st__120#entry2393729

[phil nw.]

I have been away for a few days and have not been able to keep up with the models as much as I would have hoped but there is one noticeable thing that I have noticed upon reviewing this evening.

The polar vortex is set to increase in strength drmatically and centrally in the 4-7 day range. This is projected in every model but I will use the latest GFS run to demonstrate.

Day 4

Day 7 (vortex lowering of heights circled)

There is no surprise in seeing this - especially as the stratosphere has been cooling in line with average. The day 7 tropospheric vortex even though it has strengthened it is by no means as strong as we have seen it in the past.

So what will this mean after day 7?

My guess is that the AO and NAO indices will move towards neutral. Any Rossby wave train will have to be twice a strong to keep the meridional pattern that we have been seeing persist throughout November. My guess is that we would see some more flattened (less amplitude) meridional pattern for a while yet, especially if the MJO wave loses amplitude.

http://www.cpc.ncep....clivar_wh.shtml

Talking of the MJO, there is promise here in the forecasts - avoidance of phases 3-6 is welcome at all times!

Yes i have been watching these trends in the various ens outputs Chio. and it does look like some flattening of the Atlantic 500 pattern for a while as we go into week 2.

The 00z ens mean Heights/Thickness underline this trend if we compare now and T192hrs.

We can see the yellow heights and high thickness levels around the Canadian maritmes disappear and those lower blue heights start to spread across that same area.

Looking at the 12z GFS Ens graph fairly normal temperatures seem on offer in the next 2weeks= rather cold to around normal with op run very close to the mean.

So no mild south westerly setup expected with the jet still running south but perhaps it`s fair to say a trend back to more typical late Autumn for now with any Atlantic heights at a lower latitude.

[MR EXTREMES]

I did say yesterday vortex is strengthening and on the move all models have been consistent showing this let's hope the ao and nao don't go to much into the positive.

Pretty stormy and cool the alantic is well and truely alive.

[Gibby]

Good evening. Here is the report of the 12zs from GFS, UKMO and ECM.

All models continue to show a deepening depression moving towards the area just to the North of Scotland with a freshening West or Southwest flow developing over the UK over the next 24 hours. A trough will swing steadily East as tomorrow goes by reaching Eastern Britain after dark. An area of rain associated with it will affect the NW later tonight, then other Western and Northern areas tomorrow and reaching the East Coast after dark. Following on behind will be a colder and showery flow of winds, still basically from a Westerly quarter with some heavy showers likely through the end of the week and the weekend as the deep Low pressure remains close by over or near the British Isles. Once the showery weather arrives it will be cold enough for some wintry showers on Northern hills and mountains.

GFS then shows next week starting in much the same way with Low pressure slipping away East leaving a legacy of cold and showery weather over the SE before a ridge brings drier if still rather cold conditions by Tuesday as it advances East off the Atlantic. By midweek things remain rather cold but with some brighter spells and the chance of frost at night with most places by then dry. At the start of the lower resolution part of the run the ridge clings on in the South for a day or two keeping things dry if rather cloudy. further North winds freshen from the West bringing somehat less cold weather with rain at times in a blustery wind, extending to all areas by the end of next week. A windy and changeable pattern sets up then to end the run with some rather cold and blustery showery conditions in a stiff NW wind giving way to quieter conditions briefly at the end of the run.

The GFS Ensembles show a brief milder interlude once the current low pressure releases it's grip early next week, indicating a ridge of high pressure as it's supported by a period of less rainfall. Changeable conditions return thereafter with temperatures little better than normal at best with occasional rain from Atlantic low pressure. Again tonight there is no evidence of any real cold or mild weather with very standard Autumn weather likely to be felt at the surface.

The Jet Stream blows South to the West of the UK before turning East over France during the coming days. By next week the flow shows signs of weakening and ridging North through the Atlantic later.

UKMO for noon on Monday shows Low pressure off NE England with a rather cold and unsettled flow of winds from a NW quarter over all areas bringing rain and showers with snow on Northern hills.

ECM shows an unsettled start to the new week as our large Low pressure from later this week finally moves away as well as filling up. High pressure builds strongly to the SW of Britain bringing a milder Atlantic airflow around the top of the High pressure and down over the UK with a fair amount of dry if rather cloudy and breezy weather for all with most of any rain restricted to the far North. This pattern lasts for a few days towards the middle of next week. However, later in the week a resurgence of Low pressure brings another spell of rather chillier and unsettled weather back to all areas before the weekend.

In Summary the models seem to agree tonight on something of a pressure rise at the beginning of next week as High pressure builds down to the SW. In this setup a rather cloudy airflow would likely cross around the Northern perimeter of the high and down over the UK bringing a spell of milder if rather cloudy winds but less rain than we would of been used to. However, this seems unlikely to last with a return to a basically rather cold and unsettled conditions again by the end of the week as Low pressure sinks down once more from the NW.

[ANYWEATHER]

The ecm, at T+240, shows that even with the pattern we have at the moment, any amplication in the Atlantic is possible and leading to some shots of very cold air for a while, but with the pattern we have at the moment, shots of" real cold" will be at a premium!!!

[lorenzo]

Some longer range teleconnections for AO and NAO, missed these being available so grabbed a trial on WB to view them.

AO certainly spikes then falls in the first half of the month.

Ensembles

Extended NAO

[chionomaniac]

Moving on from my earlier post this evening the 12Z ECM is a classic example of what I was trying to explain. We have an increase in the vortex strength, but this fails to knock out the meridional pattern.

Here at T +168 the increase in PV is obvious.

However, critically the meridional pattern survives so that by the end of the run we have the dampened down, but still evident autumnal patten:

The present cooling forecast in the stratosphere won't be influencing the vortex for around a month yet (and may still not if the meridional tropospheric pattern wave breaks centrally into the stratosphere in the meantime), so this pattern persisting over this time could potentially lead to some increased cold outbreaks before we get an idea where winter is headed.

I also have a hunch that the MJO will recycle back to phase 6/7 when it regains amplitude (sticking with ECM ensemble mix)

Edit: that fits in with Lorenzo's 'aero' graphs above.

Edited October 30, 2012 by chionomaniac

[mcweather]

Absolutely and theres no disputing that. However, that prognosis is fairly useless at such a range when you don't know what that scenario will be! And surely thats the point of forecasting? Picking an outcome rather than saying, well model X suggests 4 possible scenarios beyond day 10 at present, and so one of these 4 scenarios will come to pass.

Kind Regards

SK

Hi SK I would agree with you up to a point however if the scenarios are similar and quite often they can be then a reasonable stab at the outcome at day ten or more can be made. After all this is essentially what the meto are doing with their15 and 30 day forecasts.

regards

MC

[EML Network]

Well I can't but feel let down, it looked to all intensive purposes that this week was going to be a real corker, with strong winds really hammering many parts of the country, as per normal it's all been watered down and all were left with is a big pile of mushy nothingness over the next week, leaving everyone looking into FI territory for anything remotely interesting.

YAWN ...zzzzz

Wake me up when something exciting is within +72 please

[Liam J]

Well I can't but feel let down, it looked to all intensive purposes that this week was going to be a real corker, with strong winds really hammering many parts of the country, as per normal it's all been watered down and all were left with is a big pile of mushy nothingness over the next week, leaving everyone looking into FI territory for anything remotely interesting.

YAWN ...zzzzz

Wake me up when something exciting is within +72 please

Certainly some interesting weather coming up within the next 24 hours - http://forum.netweat...00#entry2393740

I think the problem we have sometimes is that people are looking to far ahead - more often than not ending in disappointment once we get into the reliable time frame, like last weeks colder spell for example.

Edited October 30, 2012 by Liam J

[Gibby]

This is why I don't get carried along on the tide of euphorium of winter charts at t180+. Much as I admire and enjoy the in depth analysis that some posters give on longer term projections of cold I think the danger is of over analysing things. Greenland High's might be good for Northerlies but as is illustrated in tonight's output it can quickly be displaced as the Polar troughs push through. Our problem tonight is our old friend the Azores high which is misplaced to the Northeast of the Azores and far enough South to allow milder air to push around the high and over Britain early next week. As long as that high stays in that position any cold will be brief and fleeting.

[BLAST FROM THE PAST]

As yet the azores HP has had no influence and with the jet on its southerly track it too will be fleeting, so lets not get ahead with both cold scenarios or AZH spoiler scenarios.

BFTP

[shotski]

why does this forum watch the models so far out in fi.

To pick up trends.

[BlueHedgehog074]

I think it's because people like to look for particular synoptics, for example; a chilly snowy Easterly wind with a solid block of High Pressure to the North and Low Pressure to the Sourh. Clearly, while charts in deep FI should not be taken too seriously due to the fact accuracy with the models' outcomes lowers the further out they go, they can be useful for trend spotting. It's just like with the GFS - on some of its runs its been showing some kind of Easterly in FI, only for the model to erase this idea on some of its other runs and then bring back the Easterly again (the latest 00Z update pretty much has an Easterly with that Scandi/Euro High later in its run). Should the GFS continue to show this solution with it stepping into a more reliable timeframe, then it has effectively spotted a trend which the other models may be (or already be) starting to follow. This 'trend spotting' idea is another reason why people may/will look far into FI of various charts.

Edit: shotski already beat me to it.

Edited October 31, 2012 by DiagonalRedLine

[Timmytour]

why does this forum watch the models so far out in fi.

Because the models go out that far

[snow drift]

I have been away for a few days and have not been able to keep up with the models as much as I would have hoped but there is one noticeable thing that I have noticed upon reviewing this evening.

The polar vortex is set to increase in strength drmatically and centrally in the 4-7 day range. This is projected in every model but I will use the latest GFS run to demonstrate.

Day 4

Day 7 (vortex lowering of heights circled)

There is no surprise in seeing this - especially as the stratosphere has been cooling in line with average. The day 7 tropospheric vortex even though it has strengthened it is by no means as strong as we have seen it in the past.

So what will this mean after day 7?

My guess is that the AO and NAO indices will move towards neutral. Any Rossby wave train will have to be twice a strong to keep the meridional pattern that we have been seeing persist throughout November. My guess is that we would see some more flattened (less amplitude) meridional pattern for a while yet, especially if the MJO wave loses amplitude.

http://www.cpc.ncep....clivar_wh.shtml

Talking of the MJO, there is promise here in the forecasts - avoidance of phases 3-6 is welcome at all times!

Plus GP's post 210. Sorry tried to multi quote but I was beaten by tech.

The two posters above are very much respected on here and by myself. What I find interesting is that often their thought pattern is similar but these two posts seem to be coming to a very different conclusion. I appreciate that these guys are not joined at the hip and are a loud to have different opinions but I would be interested if either or someone else can through some light on to what seems to be a very different take on the output.

I am not trying to be clever and raise this as I feel this will help in mine and others learning. If I have got this wrong and in fact they are saying a similar thing, then my apologises in advance.

Edited October 31, 2012 by snow drift

[IDO]

GFS has been flattening out in FI for a while now. The first half of November now looking to be relatively quiet but cool, after the toned down LP influence of the next week. At the end of FI:

h500slp.png

There is a slack Easterly (pattern in recent runs), pulling in 500hPa temps, that are on the mild side, but cooler 850's, but still not far off average for November.

The best I can see in the medium term is cool zonality, though with the jet trending North at times:

hgt300.png

It may not be that cold.

The ensembles starting to show more scatter:

00_384_mslp500arc.png

as early as seven days, with as many milder options as cooler ones, so Azores High maybe moving into the picture, probably not on a blocked basis, according to the current runs.

The PV is becoming more organised:

00_384_mslp500arc.png

Though there is plenty of cold there, so still potential for energy to disrupt to our latitude, and as a whole the synoptics remain good for a wintry outbreak, but weeks away at best on the GFS 0z op run. Hopefully "potential" is not the watch word for the coming Winter!

Edited October 31, 2012 by i'm dreaming of...

[fergieweather]

UKMO Ops Centre goes for the milder option later next week: " Weight of deterministic and EPS solutions show depression expected near or over Scotland for much of this weekend moving into the N Sea for the early part of next week. E’ward movement of associated upper trough allows a jet to propagate E’wards across the N Atlantic leading to a much more zonal pattern becoming established during the early to mid-part of next week. Note that the expected position of this jet is such that both milder conditions are expected for many by mid-week and build of GPH into at least S’ern UK suggests drier conditions developing here for a time too as Atlantic depressions are steered north of Britain towards Scandinavia..."

[winterof79]

Remaing blocked according to ECMWF this morning for the foreseable.

http://www.wetterzentrale.de/pics/Recm2401.gif

GEM also showing the potential for a N/NE outbreak the deeper we venture in to November and conditions become more favourable

for cold.

http://www.wetterzentrale.de/pics/Rgem2401.gif