Model Output Discussion October 2012

[Summer Sun]

Although that models maybe showing something colder as October ends the Met Office are still going for temperatures around average for the time of year the only word of wintery showers is for upland parts of Scotland. This covers the period from Thursday 1st November 2012 to Thursday 15th November 2012

[Isolated Frost]

But Gavin, this is the model thread, not the met office thread.

[shedhead]

But Gavin, this is the model thread, not the met office thread.

I think he's making the point that the MO does not concur with the general models consensus...which although often the case seems a fair enough point imo.

[MR EXTREMES]

Although that models maybe showing something colder as October ends the Met Office are still going for temperatures around average for the time of year the only word of wintery showers is for upland parts of Scotland. This covers the period from Thursday 1st November 2012 to Thursday 15th November 2012

http://forum.netweat...00#entry2383913

i think the met office updates for the last week have been almost the same even to the point worded the same!

this in my opion means there as unsure as much as the models are after all fi is t144 and beyond.

but from what ive seen of the models in the last 7 days or so is very much a normal autumn setup with always the possibility of colder polar air stwitching to warmer sw flow pretty normal in october one thing that does stand out is the lack of stormy conditions much less of a feature since 2007/2008.

i feel the autumnal feel will progress for sometime yet with jan feb being more intresting if we can shift the current setup.

[A Winter's Tale]

Good afternoon.

Some of conditions today in Scotland has been more like mid January rather than mid October with some low temperatures and wintry precipiation on the hill, the rest of the country has seen some really unpleasant conditions. However, parts of eastern Wales and the southern half of England has been quite breezy but sunnier with showers, a largely cloudy day with some dampness for Ireland. Through the rest of the day the band of rain and some hill snow will continue to stay put over large parts of Scotland and some rain near northern Ireland with showers up and down the length of the Irish sea. Showers should mostly vanish in England and Wales with widespread clear skies but possibly more cloud cover and some rainfall for southern coasts. Through the night, the rain should break up and weaken in intensity over Scotland but most of the rain should be confinded to western coasts and possibly down the eastern side of Ireland. Another feature should make it's way north up the eastern side of England overnight but the rainfall here should have cleared into the north sea by dawn. Some clear spells overnight down the western side of England but by dawn some of the showers in the Irish sea may move a little eastwards to reach some coastal parts of Wales. Some clear skies may be possibly in a few far western areas of Scotland but rain may continue to affect the outer hebrides. Remaining overcast further over much of northern and eastern Scotland. Minima of 2C in Scottish glens to 13C in central London.

Thursday morning should start off with the best of the sunshine likely across England and Wales away from the north, possibly a few sunny spells in Scotland away from the east, a cloudy start is likely for Ireland with a little precipitation threatening the coasts, some showers in northern England and cloud cover from the continent may clip the south eastern corner. For the afternoon, some light rain may edge into the south east with cloud cover moving westwards across the southern half of England, sunny skies furthern north into southern Scotland and west in England and Wales. Showers continue to linger in the sea around northern Ireland, a cloudy day for much of the island. One or two patches of light rain across parts of Scotland and an overcast day across the east of the country. Maximum temperatures 10 to 15C. Thursday night should be largely dry for England with clear spells away from the west coast and south east, some showers in Irish sea likely to threaten coastal regions and still some rainfall situated over Scotland. Minimum temperatures 7 to 12C.

On Friday, a cloudy day for Scotland with some light rain in the area, heavier and more persistent to the north west of the mainland. Some cloud cover possible across northern England and Wales with one or two isolated light showers, sunshine further inland in England and still overcast to the south east as a result of a weak front, a much better day for Ireland with some decent spells of sunshine. Maximum temperatures of 11 to 14C. Friday night should be largely dry for most of us except a little rainfall clipping the far north of the Scottish mainland and islands and possibly the south eastern coasts of England at threat of a little rainfall. Some cloud cover down the western side of Scotland and Ireland and the south eastern counties of England, clear spells in inland areas. A return to slightly cooler nights with lows of 4-10C in cities.

Saturday at the moment is looking like a day of sunny spells for much of England, Wales and eastern Scotland. Cloudier for far western coastal areas of England and Wales at times and more extensive cloud cover for western Scotland and Ireland. The threat of showers to the north of the Scottish mainland and some light rain close to the west coast of Ireland. Maximum temperatures of 10 to 15C. Saturday night is looking likely to be a clear and dry one for much of Scotland with a possible frost in rural areas, a largely clear night for Ireland and northern England too. More in the way of cloud cover for England and Wales with a front bringing rain to south eastern areas. Minimum temperatures of 6 to 11C.

Sunday could be largely overcast away from north western Scotland as the front works its way northwards with rain across Wales and central areas of England and edging into eastern parts of southern Ireland. Maximum temperatures of 11 to 16C. At the moment, there looks like being very little in the way of clear spells at all during Sunday night with the rain now situated over Ireland and Scotland. Minimum temperatures of 9 to 14C.

For the start of next week, it seems likely that winds will be drawn in from the south bringing mild weather, some pleasant temperatures look very possible for southern parts of England. It also seems likely that at some stage next week that with high pressure situated to the north west, a northerly looks likey to develop close to the British isles but finer details closer to the time will determin whether the set-up is suitable for the northerly to reach British shores, in my opinion I think it will end up to the east of the British isles and bring a possibility of some snow cover for Scandinavia and north western parts of Russia for a time, there are various different possible outcomes that could follow so I wouldn't rule out anything but what seems likely beyond this week anyway is that there will be a taste of warmer temperatures than of late - particulary in the south - and an attempt of a northerly outbreak later next week. Following where high pressure sets up in the following runs may give us an idea to which set-up and theme that may follow. Certainly a lively scenario in the NH for the next few weeks.

[Met4Cast]

Everything seems further West again on this run..

[swfc]

decent run again this.1060 mb over greenland in october!!!!!

[Met4Cast]

http://www.wetterzen...s/Rtavn1621.png

That chart is a thing of beauty, almost perfect undercutting low, massive high over Greenland, deep trough just South of Svalbard.

Open the floodgates

http://www.wetterzen...s/Rtavn1922.png

Though of course, the second we move into the low res part of the model it starts to reset to default

http://www.wetterzentrale.de/pics/Rtavn2521.png

Edited October 17, 2012 by Daniel AKA WMD

[Cheshire Freeze]

http://www.wetterzen...s/Rtavn1621.png

That chart is a thing of beauty, almost perfect undercutting low, massive high over Greenland, deep trough just South of Svalbard.

Open the floodgates

http://www.wetterzen...s/Rtavn1922.png

I don't know about floodgates, but flooding looks a real concern owing to tight thermal gradient across the UK if those charts are anything close to reality.

[Methuselah]

The 'Arctic Blast' is even further away in FI!

[The PIT]

Indian Summer first by the looks of it which is just nudging into the reliable time frame of T96. So a move away from the cool cold stuff we've been having.

[IDO]

The 'Arctic Blast' is even further away in FI!

Late in FI admittedly, but:

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121017/12/384/h850t850eu.png

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121017/12/384/h500slp.png

With the Jet also favourable, still cold prospects. Though the Atlantic high could be the spoiler again. Though false dawns at this time of year are not really a concern.

In the reliable, rain in the SE Friday, then dry and above average seasonal temps for the south for a few days and relatively dry till T168. Turning colder from the north by T144, but only transient. Wet till the end of FI from then, seemingly the south more at risk as per the GFS 12z.

[chionomaniac]

http://www.wetterzen...s/Rtavn1621.png

That chart is a thing of beauty, almost perfect undercutting low, massive high over Greenland, deep trough just South of Svalbard.

I would say that that chart flatters to deceive, Daniel. If anything the block is too far west based which allows the Atlantic back in.

In fact most of the output so far hints that the polar vortex is likely to displace to the Eurasion side - a complete displacement, classic wavenumber 1 activity. Whilst the vortex is disrupted, unless there is enough of another segment left over the Canadian Arctic then any block will slip away westwards.

I suspect we will see that occur and will need the next high amplitute Rossby wave to come along later in the month to retry with perhaps a better chance of a successful northerly.

[BlueHedgehog074]

Despite being in deep Fantasty island, and with the fact it is very likely to change, it seems like the GFS 12Z is suffering from severe Summer withrawal near the end of its run with that deep seated Southerly air flow - the 15*C upper line just about clips the far South of England :o

I think if this was to come off (though I do rather doubt it), I would probably expect temperatures to reach between 19 to 24*C in the far South, depening how wide spread the sunshine would be. With the shorter daylight hours, I think temperatures reaching towards 30*C would be rather unlikely. Plus, those very warm uppers do get swept away quickly as the airflow quickly backs Westerly, and then North-Westerly/Northerly. Could certainly feel quite Summery, nonetheless, with lots of ice-creams being sold. ;-)

Also encouraging that the GFS is still showing an Easterly a little bit before that with that block to the North/North-West, but I think anything Wintry would likely be restricted for the North, most especially over the hills, unless we can see some colder uppers spilling further South into that Easterly airflow.

I admit I haven't seem the other runs, except a brief glance at the 0Z ECMWF, where the uppers for the North aren't quite as cold, but there's still a lot of room for cold and wintry potential in the charts to upgrade, or downgrade. Just really need to see that block to the East try set itself up in the appropiate area, similar to that of what the GFS shows mid way through its run.

[Paul_1978]

Well the GFS 18z run is very pleasing to me, and the Synoptics on offer are interesting stuff.

If this was occurring in Dec-Feb then I guess this board would crash!

But maybe the seeds are being sown for the winter, we shall see. However at the moment Im just a little bit disappointed that it's mid October when we are getting runs like this (ie channel lows, easterly teases, northern blocking etc)

Edited October 17, 2012 by Paul_1978

[Liam J]

A very different look to the UKMO 12z when compared with the GFS 12z @ T144 - The UKMO having none of the big fat Greenland high as per the GFS, not yet anyway... We all know it would be foolish to ignore the UKMO.

UKMO - Scandinavian LP is much further east.

GFS

GEM offers support for the GFS evolution

Very much FI, a chart of extremes - Snow in the N Isles and temps around 20c further south!

Edited October 17, 2012 by Liam J

[Frosty.]

The latest models show an improving picture over the next few days with low pressure moving away northwards and filling with a ridge forming over the uk by saturday, the main story though concerns the first half of next week which looks like turning warm for the time of year with temps of 17-19c widespread across the southern half of the uk, especially further south where 20c is possible towards london and the southeast. Beyond that is very uncertain but the gfs 12z op run shows an arctic plunge attempting to push south but really struggling and only scotland seems to feel the full impact of the cold air although it does eventually turn colder further south towards the end of next week but next mon/tues/wed look warm in southern britain with a s'ly to se'ly airflow. The other main theme of next week would be the large rainfall totals as the arctic air and mild air clash and there would be flooding although details of where it occurs are pointless to speculate on as next week could just as easily be very mild and fairly benign with no cold southward surge, anyway, the gfs 12z then shows much milder weather sweeping northeast across the uk as a depression tracks across the uk, even the far north eventually becomes milder. if the 12z verified (long shot), there would be some huge temperature contrasts from north to south. I'm still hoping the cold air makes it down to the south coast but it does look like a struggle with shortwaves becoming more likely to stall it's progress as we get nearer the time.

[Zenarcher]

Tonights model comparison, I done this towards the end of the winter last year and people seemed to like it so here it goes again.

Up to 21st October: All the models agree within the 96 hour time range that a ex hurricane will enter the Atlantic but it will quickly be absorbed by a low pressure system in the Atlantic. While this is happening high pressure starts to build to our East and North, the low pressure systems in the Atlantic is now just one, it starts to move South and this helps more high pressure build up over our East and North.

GFS: At 120 hours it shows the low in the Atlantic continue to move South as the high pressure continues to build over our North. It seems to have good support on this tonight from all of the models except the UKMO. 144 hours on the GFS seems very interesting we see the Greenland high looking strong to be around 1050mb but we also have a strong low pressure system over the Svalbarb, now looking at the other models it doesn't gain too much support, the GEM is the closest with the ECM and NOGAPS not far behind, they place it a bit more East. Finally at 168 hours the high pressure over Greenland continues get stronger and reaches around 1060mb looking at the other models as you would expect there is disagreement between but none the less some interesting model watching for the next few days.

ECM: At 120 hours it seems to have good support between most of the models tonight and at 144 hours it looks similar to most of the models. 168 hours shows high pressure in the Northern hemisphere it's looking great up there with no signs of the dreaded PV taking charge or the Atlantic.

UKMO: I won't go too much into detail with it tonight because it doesn't seem to have too much support between the models but comparing the Northern hemisphere outlook at 144 hours to the ECM's they do look alike although I prefer the ECM's and this is at 144 hours so changes will happen I wouldn't say the UKMO is anything to be worried about.

GEM and NOGAPS: Both seem very similar to the GFS for their entire runs with the high pressure over Greenland gaining strength and a low pressure system over Svalbarb digging down South.

Overall - The models continue looking good this evening for a blocking pattern to take place soon and into the end of October, there are disagreements between the models tonight but all of them seem to show some sort of blocking occur. The GFS, GEM and NOGAPS both seem the most alike tonight with the ECM not far off.

[Gibby]

Good evening. Here is the evening look at the 12zs from GFS, UKMO and ECM.

All models show a deep depression near Ireland drifting slowly NNE and filling in the next 24 hours. A trough lies to the SE with disturbances running along it at times. In between a showery SW flow is shown. By Friday the Low loses it's identity over the UK with slack winds and fair weather with mist and fog problems developing overnight. By Sunday a depression over Biscay pulls North and brings rain and fresh winds back to the South transferring North later in the day. Behind it pressure rises from the East with a warm South or SE flow developing early next week.

GFS then moves forward showing Loow pressure moving close to Southern Britain with a strengthening East wind and rain returning. The North becomnes steadily colder and windy too but will stay mostly dry. By the end of the week cold and wet conditions arrive everywhere with persistent rain in the South while Northern areas continue in cold but drier conditions though wintry showers would develop in the North and East. through the rest of FI the weather eamins cold and unsettled for a while before a quieter interlude occurs. Then at the end of the run wet and windy weather returns to all with alternating rain bands and showery conditions for most.

The GFS Ensembles show a major split at the halfway point with much spread between the members. The operational was a cold outlier for the upteenth time for Northern locations while rainfall gradually subsides from current levels in the second half of the run.

The Jet Stream continues to trough sharply South just to the SW of Britain before returning NE over SE England and NW Europe. later the flow splits with one flow travelling East to the North of the UK while a lighter Southerly arm moves across the Atlantic towards SW Britain in a week or so.

UKMO for noon on Tuesday shows Low pressure West of Spain and the UK in a slack airflow with relatively Low pressure aloft. The weather would be quite warm by day with some sunny intervals but the odd heavy shower could not be ruled out especially near Southern Coasts. Fog could be an issue overnight too.

ECM for the same time shows a High pressure moving East towards Portugal with High pressure over Northern Britain and a SE-E flow over the South. The weather would be dry and fine for many and relatively warm. Later in the run the low over Spain pushes a trough slowly NE towards Northern France strengthening the easterly flow over Southern Britain and introducing rain too in steadily lowering temperatures. The Day 10 chart shows a strong East wind over the South with High pressure near Northern Scotland bringing dry and cold conditions there with cloudy and raw conditions in the South too by then.

In Summary the weather looks like settling down briefly early next week with a warm fetch of wind from the SE. Later in the week it looks like the weather will turn colder as cold air infiltrates the UK from Scandinavia on a strengthening Easterly wind later. With Low pressure ending up somewhere near the South of the UK re GFS and well to the South re ECM it looks like the South would end up seeing the most if any rainfall.

[SMU]

Evening ALL-

forum was down earlier so this was done at 715-

Not sure If/ What posts were removed earlier- Anyway, as mentioned this isnt a competition to see whos the best, All I am doing is trying to highlight the model differences between GFS run to run & why some weakness & why the ECM V GFS-

In the short term & even mid term its pleasant enough with a gentle south easterly breeze- all thats of a concern is that small shallow shortwaves could develop in the flow & make it wet -

Anyway-

heres the Charts we are looking at from last night- for the 28th OCT-

My expected forecast date ( using the 12z GFS 16/10/12)- 228 Hours

http://modeles.meteo...12-0-228.png?12

As said- classic OMEGA block.- with the CAA filtering into the UK

If we look at the ECM for 00Z earlier at 192 & 216-

http://www.meteociel...ECM1-192.GIF?00

http://www.meteociel...ECM1-216.GIF?00

As we can see ( or at least should aknowledge the ECM has moved to the GFS since its 12z run yesterday-)

As look at what it presented then-

http://www.meteociel...ECM1-240.GIF?12

So some degree we see a move from the euro to the GFS-

Remember I have discarded the 00z ECM & the 12Z ECM yesterday-

Do we remember my comments on the ensemble suite-

http://www.knmi.nl/e...agse/index.html THumbs up for that & the ECM mean at 216

http://www.meteociel...1-216.GIF?17-12 pretty good- if you know what signal to look for-

We now take todays GFS for the 192 arena-

00z

http://modeles.meteo...700-0-204.png?0

06z

http://modeles.meteo...706-0-204.png?6

12z

http://modeles.meteo...12-0-192.png?12

Its a small sample size but quickly the 06z sticks out for the polar blocking being poor & weak- & even at this early stage indicates to me the 06z is one to be discarded ( again based on the assumption that my original pattern will occur)

Why the variability- its all about the shortwave over SE greenland- so before we look at that cast our mind backs to Dec 2010- who remembers the HUGE GH that send that massive cold surge south-

Actual chart

http://modeles.meteo...-12-16-12-0.png 16/12/2010

Now rewind the model output 7 days before-

ECM-

http://www.meteociel...ECM1-168.GIF?00 00z

http://www.meteociel...ECM1-168.GIF?12 12z AWFUL!!!

GFS

http://modeles.meteo...900-0-168.png?0 00z

http://modeles.meteo...12-0-168.png?12 12z

I knpow I keep going on about this 'type' of scenario- but rewind 10 days back

GFS at 240 12z

http://modeles.meteo...12-0-240.png?12 AWSOME

GFS 06z

http://modeles.meteo...606-0-252.png?6 not bad I guess-

So wheres the trouble occuring this time around?- same region / same time ish-

Shortwave moving South East off the coast & how it then spins the polar air south-

here it is-

http://modeles.meteo...snh-0-96.png?12

look at the east coast of greenland-

Its Angle & movement along some easterly or south easterly vector- THIS is the variability you see between 12z & 00z-

All the subsquent jet energy is moving south east across the pole-

http://modeles.meteo...nh-5-120.png?12

The energy on the ECM I believe to be wrong & moving to far EAST with no southerly component....

This is where we need to focus over the next 48 hours-

There is a near 100% correlation between the momentum EAST V the penetration SOUTH- If the low exits direct 90 Degrees East the cold wont reach the South-

If we get an exit away from GH at say 135 degrees ( which is exactly halfway between 90 degrees & 180 degrees )- otherwise known as SE then the penetration will more than likely get into the south of the UK

There are other factors like the returning jet north at around 168-192 because this jet will try to equalise the polar air moving south-

see it here on the 12z over france moving North-

http://modeles.meteo...nh-5-168.png?12

So before I run out of time before the ECM runs-

I am EXPECTING the ECM 12z or 00Z tonight to follow the GFS- or at least get closer-

GFS > ECM on greenland shortwaves - I hope im right now...

S

Edited October 17, 2012 by Steve Murr

[Geordiesnow]

Indian Summer first by the looks of it which is just nudging into the reliable time frame of T96. So a move away from the cool cold stuff we've been having.

Again, the details are sketchy so I certainly won't say anything about an "Indian summer" just yet but the trend for warmer air(so it should feel warmer even with cloud cover) and a pressure rise is still there.

Orientation of the high is going to be important aswell in deciding who gets sunshine and who gets cloud cover. Must say, even at 96, the UKMO looks a little bit on its own at the moment.

Regarding any cold shot, can't deny the possibility is there but a lot of complications before you can nailed the output either way, would appear there is going to be some strong heights over Canada/Greenland and whilst that can open the door of a Northerly as the GFS to some extent shows, we can also see it does not guarantee a cold set up. As I said earlier, don't get hung, drawn and quartered on every individual run and just look at the general trends.

[ANYWEATHER]

The gfs has been barking on this projected cold spell for some time. Ecm has been all over the place! During the summer period the gfs took the lead in its outlooks......Ecm followed the lead...Here we Go...!!!! It must be said our weather is certainly changing, this cold progged so early on in the season is not the norm,but the transition to a colder world is likely! PS.....Someone will say back up the idea!

Edited October 17, 2012 by ANYWEATHER

[Cloud 10]

Today's outlook discussions form CPC still favouring the GFS regarding their 500mb charts.

Climate Prediction Center - 6-10 and 8-14 Day Prognostic Discussions

[SMU]

Today's outlook discussions form CPC still favouring the GFS regarding their 500mb charts.

Climate Prediction Center - 6-10 and 8-14 Day Prognostic Discussions

MODEL OF THE DAY: GFS SUPERENSEMBLE MEAN

[shedhead]

all gone quiet on here.

Hard to know why with charts like this on offer from the 18GFS, but of course it's still deep in FI and in the short/medium term it's warmth rather than cold that looks set to dominate.