Model Output Discussion 12z 30/11/2012

[IDO]

The GFS op run remains a relative outlier in FI, thats four runs in a row, to one degree:

http://cdn.nwstatic..../t850London.png

Until we see some support with the members and especially as no other models hint at this type of cold then we must suspect this as low confidence. Note the cluster in the 850s for 0-5c. The air pressure ensembles:

http://cdn.nwstatic....prmslLondon.png

show that there is support for HP close to the UK but its placement is what will determine the level of cold and that easterly potency. The GEFS mean shows the cold to our east with Atlantic high close to our west, no mans land:

http://modeles.meteo...-21-1-384.png?0

http://modeles.meteo...-21-0-384.png?0

The GFS Control does again support the op, but if both get the Tropical storm's track wrong then they are both wrong and we head towards a cool (with colder shots) set up rather than a cold/v.cold one. This is like the first shot this weekend where it went wrong, and thus delayed the prolonged cold for a week, its another close call and another miss will delay cold till the last third December at least (as will be in a blocked pattern and if the UK is in the milder(*) side of the block...).

(*) less cold side of the block

Edited December 2, 2012 by i'm dreaming of...

[Duane S.]

The GFS op run remains a relative outlier in FI, thats four runs in a row, to one degree:

http://cdn.nwstatic..../t850London.png

However, yet again, the control follows. Whilst that is occuring it cannot be an outlier

[bluearmy]

Know what you mean but there wont be a 'mild' side of any block, just 'not the frigid side'!!

ecm changing its mind so much in its mid range never a good sign for confidence in any solution. broad agreement at day 6 remains intact.

[Severe Siberian icy blast]

For ones to say there is no quick way to cold is hideous .

Every model shows fantastic potential with lots of interesting opportunities this next few wks, looking at specifics for things even a wk away is useless really as details change. The last chart on the ECM shows a fantastic snow event for the bulk of the uk with a classic slider and blocking in place to our north. The ukmo is the flatist one but even that you can see where it wants to go. The gfs is brilliant , remeber the 850's mean nothing just look at the Synoptics.

Edited December 2, 2012 by shaun wilmer

[Frosty.]

Well i'm going to remain positive, the Gfs 00z op run is really good from a cold perspective, so many changes in the week ahead alone. We are still cold, there will be snow in the north tonight, tomorrow less cold with temps of 5-10c north to south but gradually turning colder from the north by late tuesday with a wintry mix, midweek is cold with wintry showers and N'ly winds, a ridge then brings a frosty fine interlude before the next depression pushes down from the northwest with wet and windy weather followed by cold air and wintry showers. So that's 2 more cold snaps but then the gfs 00z is showing a prolonged very cold spell with a massive blocking scandi anticyclone keeping the atlantic at bay. We are looking at a very complex pattern but at least the gfs 00z has made me happy this morning, initially though it's the north of the uk which has more wintry potential than the south but as time goes on we all become much colder.

[tinybill]

morning all i see on the gfs is starting from the dec 12 the UK could have a major snow event here in the uk !!!

Edited December 2, 2012 by tinybill

[nick sussex]

Not much change this morning in the overall pattern although it looks like low pressure to the nw splits and you have to wait for the second one to slip se before getting the build of pressure into Greenland.

Interestingly looking at the track of the shortwave at 96hrs could be some snow on the leading edge of this, the ECM continues to audition for the cannon fodder model section past 144hrs with yesterdays complex affair now a distant memory, hopeless is being kind to its poor continuity past this point in recent days.

Overall given the shape and positioning of the PV and high pressure building sw out of Russia later it does scream ne/e eventually,lets hope the models aren't deaf and get a move on!

[Frosty.]

For ones to say there is no quick way to cold is hideous .

Every model shows fantastic potential with lots of interesting opportunities this next few wks, looking at specifics for things even a wk away is useless really as details change. The last chart on the ECM shows a fantastic snow event for the bulk of the uk with a classic slider and blocking in place to our north. The ukmo is the flatist one but even that you can see where it wants to go. The gfs is brilliant , remeber the 850's mean nothing just look at the Synoptics.

Really good summary, i'm mystified again by the negativity by some, really drags things down in here. The trend is for more cold shots and perhaps a prolnged cold further outlook but I will leave the specifics of that to the experts, I am very encouraged by the trend, much more potential than last year.

[Long haul to mild]

The models still look messy this morning; the GFS has a couple of brief northerly blasts, then builds heights to the NE. It all looks set up nicely in deep FI but then it goes and pushes the block too far East and the E'ly doesn't quite get here!

Still, the fact that most of the solutions at the moment point towards eventual blocking to our NE in mid month is encouraging and I expect we will see a lot more of this over the coming days.

[nick sussex]

The much maligned ECM also delivers a chance of some backedge aswell as front edge snow that shortwave develops at 96hrs, as it clears into the Low Countries theres a decent undercut of colder air into the precip.

The models not suprisingly disagree with its track though and how much cold air is available at that time.

[chris55]

Models starting to struggle again this morning in the mid term, should be fun watching all the different solutions being thrown out.

That Tropical wave at 144 gets kicked north on the Western side of the high on both the GFS and ECM, but how far north the ridging high gets and potential split flow over Western Greenland is undecided.

[IDO]

MattHugo81

ECMWF ensemble mean from 00Z is a cracker!. Builds pressure to the N and then NE towards the 10th-12th = cold & seasonal!

02/12/2012 08:25

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

Also: http://ds.data.jma.g...e/pole30_n.html

It looks like the ECMWF ensemble may be more reliable than the op run at the moment. That was my point with the GEFS, with so much uncertainty the ensemble mean is the best place to look, till a clear signal emerges:

As others have said the synoptics are exceptional so its a matter of time before we get very cold down to this latitude.

Edited December 2, 2012 by i'm dreaming of...

[Gibby]

Hi Folks. Here is the look at the 00zs from GFS, UKMO and ECM for today Sunday December 2nd 2012.

All models show a fairly similar evolution of events and synoptics through the next 5-6 days. Todays cold weather is the remains of the recent weak Northerly and are being replaced by troughs of Low pressure moving in off the Atlantic later today and tonight bringing increasing cloud, wind and rain across all areas. The rain will fall as snow for some time over the North with a covering for many before it turns back to rain late on. Following on behind is several days of rather cold and blustery NW then North winds with showers, heavy in the North and West and increasingly wintry again by midweek, especially in the North and East. Towards the end of the week High pressure lies not far from SW Britain with a NW flow down over the UK with a renewed pool of cold air behind another cold front later on bringing further wintry showers to Northern and Eastern Britain while the SW stays dry and rather cold.

Over the weekend GFS shows another more definitive spell of wet weather as Low pressure moves SE over the UK with rain and wind followed by cold NW then North winds and wintry showers by Monday with the likelihood of heavy snow showers near Eastern coasts with frost at night, especially in the West. Through FI this morning the pattern is shown to be influenced by High pressure close to the West gradually linking as a ridge to a Scandinavian High maintaining cold weather for many over the UK with frost and fog patches for many and still a few wintry showers likely in the far East and SE at times.

The GFS Ensembles are less encouraging this morning for coldies with a warming trend later in the run. The operational and control runs are both at the bottom end of the pack later in the run while many members sees a return to 850's close to average at the end though there is a huge spread over north and South locations in the second week. Some rainfall is shown but no great amounts beyond week 1.

The Jet Stream flow shows the South moving flow over the UK backing NW to SE over Southern Britain in the coming days and continuing to flow all the way down to the Med before moving East over Southern Europe later in this coming week.

UKMO for midnight on Saturday shows Low pressure over Germany with High pressure close to SW Ireland. The rather cold changeable theme would continue with some wintry showers in the East clearing away as drier weather elsewhere extends to all areas as a ridge slips East bringing frost and fog patches overnight.

GEM this morning at Day 6 shows a continuation of the slack NW flow with wintry showers possible for the North and East while High pressure to the SW keeps many dry here . It would be rather cold in the North and East. Later as the High ridges North then NE to Scandinavia winds turn North to NE making things much colder everywhere with further wintry showers in the East while the north and west stay or become dry and frosty.

ECM shows a changeable pattern over the UK with winds between West and north around High pressure to the South and West. It would be rather cold at times, chiefly in the North and East where rain or wintry showers occur at times. Late on a slender ridge moves down over the UK from the North with a dry and frosty spell likely before cloud with rain and sleet from a cut off low to the SW could affect Southern and Southwesternmost areas later.

In Summary today the pattern looks like becoming a NE/SW pattern with the coldest and most unsettled weather reserved for more North-eastern areas with rain and wintry showers likely at times while Southern and western areas see a lot of dry weather with temperatures just slightly below normal and frost by night. All this due to the persistence of a misplaced Azores High centred close to SW Ireland. The models seem less encouraged to link this with the Scandinavian High in this run with the net consequence that serious cold is kept East over Europe on this run. However, there is still potential for this to change though the steady rise in the GFS Ensembles towards more normal levels in week 2 are a concern for coldies I feel.

Edited December 2, 2012 by Rybris Ponce
Date amended.

[nick sussex]

MattHugo81

ECMWF ensemble mean from 00Z is a cracker!. Builds pressure to the N and then NE towards the 10th-12th = cold & seasonal!

02/12/2012 08:25

Also: http://ds.data.jma.g...e/pole30_n.html

It looks like the ECMWF ensemble may be more reliable than the op run at the moment. That was my point with the GEFS, with so much uncertainty the ensemble mean is the best place to look, till a clear signal emerges.

As others have said the synoptics are exceptional so its a matter of time before we get very cold down to this latitude.

Yes if you look at the ECM ensemble mean its very good in terms of overall pattern, something really outlandish in terms of the crappiest luck this place has ever seen would have to occur for the UK to miss out on some tasty synoptics.

[bluearmy]

i dont think there is much doubt that we face a cold fortnight. the specifics look difficult to pin down. gefs week 2 offer several scenarios, none of them anything other than cold although a high squashed between energy to our nw and troughing to our se will feel cold under average uppers rather than offering anything other than a possible retrograde further down the line. the control and op are similar for uppers but their set up late on is different with a retrograde greeny block on the control as opposed to the op with its n scandi blocking. not enough confidence to pin down a favoured solution for week 2 approaching mid month although as per the past couple of days, i would still plump for the trough to our se with the ridge across to our north and renewed energy dropping into the trough from time to time.

[bluearmy]

However, there is still potential for this to change though the steady rise in the GFS Ensembles towards more normal levels in week 2 are a concern for coldies I feel.

the slow rise in uppers relates to the majority of output having us under a block of some kind martin after the euro troughing has filled on the colder ones. that would only concern me if there was a strong trend from the model to drop heights near greenland.

[bluearmy]

MattHugo81

ECMWF ensemble mean from 00Z is a cracker!. Builds pressure to the N and then NE towards the 10th-12th = cold & seasonal!

02/12/2012 08:25

Also: http://ds.data.jma.g...e/pole30_n.html

It looks like the ECMWF ensemble may be more reliable than the op run at the moment. That was my point with the GEFS, with so much uncertainty the ensemble mean is the best place to look, till a clear signal emerges.

As others have said the synoptics are exceptional so its a matter of time before we get very cold down to this latitude.

the way that mean and spread is setting up by day 10, it wont be too long before mr murr is along to play 'spot the siberian cold pool dropping into the flow east of the urals and heading our way'

[chris55]

As Mr Hugo said ens mean on ECM looking good

[Cloud 10]

Big difference between the 00z gefs and 00z ecm ensemble means at +240 hrs.

The ecm has -4 upper air covering most of the country, and in ensemble mean

terms that is a stonker!

gefs.. ecm..

[bluearmy]

Big difference between the 00z gefs and 00z ecm ensemble means at +240 hrs.

The ecm has -4 upper air covering most of the country, and in ensemble mean

terms that is a stonker!

gefs.. ecm..

that will probably be down to the number of ecm members that keep troughing close to our east or se. the gefs has plenty of blocking options near the uk with inevitable less cold uppers. whilst the uppers may be a bit different, the surface temps will be cold under both scenarios.

[TEITS]

Slowly the mist is clearing and I can see clearly now. A combination of the ECM mean and the GFS Ops gives a good guide of the likely events in the near future.

At +168 we have lovely warm S,lys spreading from the Atlantic into W Greenland (always a good sign) and in the mean time low pressure to the N of the UK slowly tracking SE.

http://www.meteociel...1-168.GIF?02-12

As this occurs we then start to see a rise in pressure towards the Iceland region. Now in my opinion rather than a Greenland HP developing we're going to see the core of this HP over Iceland/SE Greenland. The low pressure continues to track SE.

http://www.meteociel...1-192.GIF?02-12

By +240 and bingo a lovely E,ly flow as the LP is now SE of the UK.

http://www.meteociel...1-240.GIF?02-12

This is perfectly logical and is one of the main reasons why GFS F.I has been so consistent.

Edited December 2, 2012 by THE EYE IN THE SKY

[Polar Maritime]

If I remember correctly, GP sounded very confident of high pressure setting up over Iceland.

[bluearmy]

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!144!pop!od!enfo!enplot!2012120200!!/

post T96 seems to offer plenty of options with the shortwave energy and track.

[IDO]

Big difference between the 00z gefs and 00z ecm ensemble means at +240 hrs.

The ecm has -4 upper air covering most of the country, and in ensemble mean

terms that is a stonker!

gefs.. ecm..

I would ignore that. If you look at the 12th on the GEFS graph:

http://cdn.nwstatic....erdeenshire.png

The mean is subdued due to a few members going into mild 850s (cant see how 3 members get +5c!). Take these out and we would be around the ECM, -4c mean. The mean surface temps are the best guide:

http://wxmaps.org/pix/temp4.html

They show in week 2: 0 to 5c for the majority, with some areas -5 to 0c. Pretty cool/cold.

Edited December 2, 2012 by i'm dreaming of...

[Cloud 10]

that will probably be down to the number of ecm members that keep troughing close to our east or se. the gefs has plenty of blocking options near the uk with inevitable less cold uppers. whilst the uppers may be a bit different, the surface temps will be cold under both scenarios.

The spreads seem to agree with that.