Model Output Discussion 12z 18/10/2012

[AWD]

This is (hopefully) the GFS06Z for T+384. FI obviously, but still appears to show a poorly organized PV?

http://nwstatic.co.uk/viewimage.pbx?type=gfs;date=20121024;time=06;ext=384;file=h850t850eu;sess=65e3da1a51d046e06cb29a85513d9a06;

I agree. Obviously you can't take a chart from the very depths of FI from the GFS literally, but there have been few charts showing an organised PV, especially over Greenland & a lot more showing a more disrupted PV, and when building, doing so more over Russia way.

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=384&code=code&mode=0&mode3h=0&runpara=0&carte=1

It's a trend that I would like to keep going for as long as possible.

Edited October 24, 2012 by AWD

[Robbie Garrett]

Not really noticed this section of the CFS on Metociel, but the latest update probably goes along way in describing the conditions.

November a blocked Atlantic, with slightly cooler than normal conditions across much of the UK. Especially the south. The MetOffice senior forecaster has probably looked briefly at the CFS as the following is interesting.

As is usual, there are uncertainties in the forecast for this period, however there is a signal for temperatures to stay below average for November across much of the UK. Scotland is more likely than other areas to see near normal temperatures.

The following in bold, is pretty much what the below chart is showing for November. Give or take.

Take a look at the extended forecast for London. http://www.bbc.co.uk/weather/2643743 Grey cloud, which is likely to be low cloud suppressing temperatures to 1 or 0*C if the lower end of the models are correct. Which at current rate, may well be. London and the South East could see it's first snowfall, probably wont be massive but it's still going to snow if those temperatures at night and in the evenings verify.

Edited October 24, 2012 by Robbie Garrett

[bluearmy]

Robbie, those CFS anomoly charts change several times each day. i havent noticed any consistency yet which is surprising as i would have expected november to be showing similar output on the majority of the runs. i rather doubt exeter will be paying much attention to them, if any.

[Robbie Garrett]

Robbie, those CFS anomoly charts change several times each day. i havent noticed any consistency yet which is surprising as i would have expected november to be showing similar output on the majority of the runs. i rather doubt exeter will be paying much attention to them, if any.

That is a fair comment. But my comment was based upon them pretty much saying the warmer conditions would be Scotland. Which looking at the CFS anomaly charts would back that point up. It's far far to early for Wintry weather, December, January and February are better months for Snow. Having this weather in October and November is a bonus.

What's your thoughts going into November, as from what I can see is Northern Blocking over Greenland is going to be re-inforced by the Azores high which may pass over the UK as we head towards December.

[NorthNorfolkWeather]

Interesting to see the swings between the models.

Whatever is the final result of the next few weeks, it's been interesting the way that the GFS has picked up on the cold spell quite early on. I also find it interesting that in FI at the moment it tries to reset to it's default -- zonality.

Still very early in the year IMO to be thinking that the Polar Vortex will not get going properly before December, but Blocking looks to be quite well established through at least the first half of November

[legritter]

Interesting to see the swings between the models.

Whatever is the final result of the next few weeks, it's been interesting the way that the GFS has picked up on the cold spell quite early on. I also find it interesting that in FI at the moment it tries to reset to it's default -- zonality.

Still very early in the year IMO to be thinking that the Polar Vortex will not get going properly before December, but Blocking looks to be quite well established through at least the first half of November

always hard to say where F1 STARTS realy but the way i see it past 10 days for even a computer modell it will run out of ideas based on the trillions and tril of information it recieves ,and as we all know just one or two miles out per hr is the difference between say s/scotland and s/england near enough .but so long as blocking exists as a generall rule to our north somewhere we are always going to get these big swings in the modells . i will state this as a fact ,many moons ago before net weather /etc , my source of information was met fax up to 120 hrs sometimes longer and late night weather ,week ahead . if there was mention of high pressure n/foundland /greenland even scandy for me it was quite often game on ,i also had access to many weather stations in n/hemisphere ,and of course daily shipping forecast , i feel real F1starts past 192 hrs ,but is still usefull as a possible outcome .i do like todays ECM ,plenty of meat on the bones .cheers.

[bluearmy]

That is a fair comment. But my comment was based upon them pretty much saying the warmer conditions would be Scotland. Which looking at the CFS anomaly charts would back that point up. It's far far to early for Wintry weather, December, January and February are better months for Snow. Having this weather in October and November is a bonus.

What's your thoughts going into November, as from what I can see is Northern Blocking over Greenland is going to be re-inforced by the Azores high which may pass over the UK as we head towards December.

except that the anomoly chart you posted has associated 2m temps of -4c for scotland, highest in the uk.

as far as november is concerned, it does seem that the three mean features of low heights to our ne and higher ones around greenland and kamchatka continue. you can paint any pattern you like around those and its feasible from mild sw around a west based -nao to screaming northerlies..

[latitude]

always hard to say where F1 STARTS realy but the way i see it past 10 days for even a computer modell it will run out of ideas based on the trillions and tril of information it recieves ,and as we all know just one or two miles out per hr is the difference between say s/scotland and s/england near enough .but so long as blocking exists as a generall rule to our north somewhere we are always going to get these big swings in the modells . i will state this as a fact ,many moons ago before net weather /etc , my source of information was met fax up to 120 hrs sometimes longer and late night weather ,week ahead . if there was mention of high pressure n/foundland /greenland even scandy for me it was quite often game on ,i also had access to many weather stations in n/hemisphere ,and of course daily shipping forecast , i feel real F1starts past 192 hrs ,but is still usefull as a possible outcome .i do like todays ECM ,plenty of meat on the bones .cheers.

F1 is usually on sundays, FI is usually after 144 in my book.

[The watcher]

always hard to say where F1 STARTS realy

I believe this week it is in New Delhi.

On a serious note though, as we head through this cold spell Early November will start to become clearer, but it is looking likely that a West Based -NAO will show up in the coming weeks. This would pull us to an average/slightly below November should it remain in situ and will definitely not bring boring weather. It is more variable than a GH situated too close and will still produce some topplers.

[summer blizzard]

Now thats what i call an inversion..

[phil nw.]

With time it looks as if those Greenland heights will regress somewhat and ease west towards Canada.

These graphs from the 00z outputs indicate the easing of the height anomolies this side of the Atlantic and show the main blocking for our part of the hemisphere will become more west based towards the Candian side.

As current daily outputs are showing, this leaves the UK under an extending upper trough moving from Scandinavia as we go into next week-so becoming more unsettled and still rather cold with a fair amount of polar air in the mix.

The T168 00z ens mean height anomolies show the expected pattern

Still some blocking around further north but regretably for cold lovers not in the best place to maintain a cold spell.

The one continiung feature is the generally disrupted jetstream which is currently a world away from the SW-NE mild flow of a few years ago.

[gottolovethisweather]

Still some blocking around further north but regretably for cold lovers not in the best place to maintain a cold spell.

The one continiung feature is the generally disrupted jetstream which is currently a world away from the SW-NE mild flow of a few years ago.

Phil, generally speaking where would we wish to have the HLB placed, for it to deliver even colder conditions to the UK?

Also, with others in here talking about polar vortices, can someone refer me to charts illustrating both split, organised and disorganised versions. I think I get the gist of it, but I would like clarification of this, which should in turn help any lurkers.

One day, I'll sit down and read all the learning guides within these forums.

[Zenarcher]

24 hour model comparison,

GFS 00z for the 30th October,

Yesterday

Today

On today's run the high pressure in the Atlantic gets pushed further West, we also see the low pressure system to the North of the UK being pushed more North and made slightly deeper.

GFS 06z for the 31st October,

Yesterday

Today

High pressure between Canada and Greenland moves more North West today also the low to the North of the UK is more deeper.

ECM 00z for the 1st November,

Yesterday

Today

Good consistent run from the ECM here with today's chart looking a lot better as the blocking over Greenland looks better positioned.

UKMO for the 29th October,

Yesterday

Today

Nothing big has changed just pushed back more West and the low over the UK see's a downgrade.

Edited October 24, 2012 by weathermaster

[Frosty.]

A nice little cold snap is now nailed on with arctic air not really sweeping south, more like filtering south slowly but eventually it turns colder everywhere but for most inland areas it's more likely to become much brighter and drier with the wintry showers confined to northern scotland and the coasts of northeast britain, barely any inland penetration, a small low forming near iceland then slips southeast later on saturday into sunday with outbreaks of rain and temps recovering slightly after a frosty start but into next week it looks colder again with rain and showers, wintry at times but especially for northern hills, there is no sign of any mild weather but temps will alternate between on the cold side to near average, probably the coldest weather always towards the far north and northeast as the scandi trough moves further west during next week and pressure remains higher to the west/northwest.

[mountain shadow]

A west based -NAO can still deliver for western areas and Ireland depending on where the mean trough sets up. The west will be closer to the coldest air drawn from the North where as the south east can possibly be in less cold/more modified air.

The longer the heights remain to the north west the better as it will continue to allow arctic air to come down from the North, which will be getting colder and colder and will deliver the goods over time.

[Alan Medlock Valley]

A west based -NAO can still deliver for western areas and Ireland depending on where the mean trough sets up. The west will be closer to the coldest air drawn from the North where as the south east can possibly be in less cold/more modified air.

The longer the heights remain to the north west the better as it will continue to allow arctic air to come down from the North, which will be getting colder and colder and will deliver the goods over time.

Yes we have had cold zonality in the 80's which delivered snow for Northern and Western areas.

[Methuselah]

Are we 'deviating' somewhat from the models, peeps...Would some of the recent posts be more suited to the 'Expectation' thread?

[Alan Medlock Valley]

Rather unsettled and cool or cold for the most part http://www.wetterzentrale.de/pics/MT8_Aberdeen_ens.png http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png http://www.wetterzentrale.de/pics/MT8_London_ens.png

[Paul]

Can we keep this thread to actually discussing the models please - saying they're boring, good, bad or whatever with absolutely no reasoning or information about the model output within the post other than a personal preference really doesn't add anything to the discussion. Writing off (or bigging up for that matter) the weather for the next 4 months or so based on a model run out to 2 weeks is also not the way forward.

We have threads to discuss winter, threads to ramp, in fact threads for pretty much every weather subject under the sun, so no reason not to stick to the models in this one. Thanks!

[phil nw.]

Phil, generally speaking where would we wish to have the HLB placed, for it to deliver even colder conditions to the UK?

Also, with others in here talking about polar vortices, can someone refer me to charts illustrating both split, organised and disorganised versions. I think I get the gist of it, but I would like clarification of this, which should in turn help any lurkers.

One day, I'll sit down and read all the learning guides within these forums.

Ideally an Omega shaped block with a solid Greenland High and troughs east and west of the Uk are as good as it gets -such as late November 2010.

The cold air filters down on the eastern trough across the UK.

There are other cold set ups of course such as the easterlys from Scandi highs but i don`t wish to stray too much off topic here..

I commented that a west based -NAO isn`t best for cold taking into account that it`s early in the season yet and medium term current outputs put the UK very much in the middle of a cyclonic set up in week2 with the coldest Arctic air having long been mixed out.

If the heights are too far west then we lose the coldest Arctic feed and are left with modified polar air-as can be seen by the less cold uppers across the UK in later modelling.

Some examples of different vortex shapes

The first is an organised vortex and second is a displaced vortex pushed to the Siberian side.A split vortex is when we simply see 2 active segments more or less divided by heights across the pole.

If you are cold lover you don`t want the organised one-the Christmas setup of last year.

With the other 2 then we have chances of some cold blocking to our north but as you can see Arctic blocking needs to be in the right place for the UK.

Hope that helps GLTW.

[A Winter's Tale]

Good afternoon. The sun has made an appearance across some western areas, the central highlands and some southern areas too. Through the rest of today clear skies should be restricted to western areas and parts of northern Ireland and Scotland with cloud cover and drizzle continuing over England, Wales and some northern and eastern parts of Scotland. Tonight should see some clear skies developing across northern parts of England, northern Ireland and northern Scotland. Cloud cover and some drizzle further south and some light rain in south eastern Scotland briefly. Minima of 6 to 14C.

Thursday should start off with two distinct areas of sunshine: northern Ireland, central Scotland; Lancashire to east Anglia. Some light rain should be clearing the south west of England and some light rain should be moving south in the north east of England. Northern Scotland should start off cloudy as light rain approches from the north. As various belts of different areas of cloud cover/light rain and sunshine move south across British Isles, the cloudy skies and drizzle of recent days should clear southwards and by Thursday evening some widespread clear skies should follow across northern areas and much cooler temperatures with a frost developing in the highlands. Maximum temperatures should be 8 to 14C. Thursday night should be largely dry and clear with only the last of the light rain and cloud cover ready to clear the south west. A cold night with lows in cities at around 3 to 7C.

Friday is set to be a sunny and cold day with maximum temperatures at 5 to 9C for many of us but even colder in the Scottish highlands. Wintry showers should be present across northern and eastern parts of Scotland and north eastern England. A widespread frost and temperatures of -2 to 3C seems likely for Friday night and wintry showers still continuing over northern Scotland and north eastern England.

On Saturday some persistent rain is set to move from the north into Scotland and raising the temperatures here - precipitation may fall as snow on the mountains for a time. Further south generally sunny conditions with maximum temperatures of 7 to 8C. Saturday night should be milder and cloudier with lows of 3 to 7C and rain across northern areas and futher south into parts of England.

Sunday should be a milder day with cloudy skies and some rainfall around - particulary in northern and western areas. Maximum temperatures should be milder at 8 to 10C. Cloudy skies seem likely to continue overnight with rain across more southern and western areas. Possible lows of somewhere between 5 to 7C.

So that's the outlook for the coming days. With the colder spell starting tomorrow I think it's worth looking at what sort of temperatures we could see and where wintry precipiation could fall.

Currently there is some sort of a northerly flow over the Shetland Isles and by midnight the upper air temperature here should be around -6C. Netweather snow risk map shows first wintryness arriving at Lunchtime tomorrow in the Shetland Isles and near the Inverness area.

Thursday evening a more widespread snow risk for Scotland.

By midnight, the most likely areas for snow is Caithness, Sutherland, Moray, Aberdeenshire and further south to the Cairngorm mountains.

Early Friday morning, snow risk for the northern coastline of Scotland, the Shetland isles and a risk extending down the north sea coastline of Scotland and into some north eastern parts of England.

3pm Friday, widespread snow risk for much of the higlands and a little for north east England.

Friday evening and once more a decent snow risk for much of the northern half of Scotland and north eastern England extending further south down the eastern side of England. Even a little risk for parts of Ireland.

My thoughts are that Shetland should get the first wintry showers by lunchtime tomorrow with -10C upper air arriving here and a decent northerly flow. The snow risk for northern parts of mainland Scotland should develop during the afternoon and evening but I suspect that conditions here should be on the dry side but the Shetland Isles continue to be at risk of catching snow showers throughout the evening. It's not until the early hours of Friday that I expect the chances of wintry showers to increase for the exposed coastlines of northern and eastern Scotland and possibly into north eastern England. Friday is set to be the best day for wintry activity. Certainly the exposed areas to northerly wind in Scotland should catch the showers and some flurries should make it further south and inland. I expect Caithness, Sutherland, the Inverness area, Moray, Aberdeenshire south into parts of the Grampian highlands and down the north sea coast into north eastern England should have the best risk for wintry showers. Possibly some of the outer hebridean islands, maybe even some exposed areas of northern Ireland and further south along eastern England could catch some something. But regarding possible snow events, we can only have a real idea once we are actually experiencing the cold spell and following the showers on the radar but I'm sure that exposed areas of northern Scotland and the Shetland Isles at least will see some snow showers. Here in the western part of the central belt, I'm not particulary confident about seeing snow but there always remain a slim chance of catching a flurry that managed to make it south over the mountains.

For temperatures, I would rather under estimate the values, so I'll experiment with using the UK Max temperature charts.

Early Thursday morning, colder temperatures should be evident across northern areas but still remaining mild across the south.

Daytime temperatures should be lower across Scotland than of late during Thursday evening and afternoon. During the night a frost for many areas of Scotland and much colder temperatures for everyone. Lows shown to be -1 to -2C but I'm sure that a met office site in the highlands would record colder values.

Cold maximum temperatures for Friday with typical highs of 3 to 6C across Scotland, northern Ireland, northern England and parts of Wales, more like 7 to 8C south of the Midlands. Some maximum values of 0C shown on the chart for the Cairngorm area, remember that the coldest maximum temperature on record for October is -0.7C, it would be interesting to see how low the maximum values get at stations such as Aviemore and Braemar.

At 9pm, temperatures shown to be below freezing over a good chunk of Scotland and into northern England and close to or just above freezing elsewhere. -4C in the highlands on that chart.

A widespread frost with temperatures for many below freezing. Coldest night of the season here was -3C, in Braemar we've already seen -8C this month but I wonder how low we can go during the coming nights. A complete contrast to this time last year anyway when it was a big struggle for many to have a frost.

Less cold conditions arrive during Saturday but southern parts of England could still have cold Saturday night and Sunday morning.

For the following days the potential for reloads remain but at this moment I expect any reload to be short lived with upper air not quite as cold as during Friday and Saturday. Eventually the high pressure over Greenland should move further west towards eastern Canada and western Greenland, a more unsettled period may prevail with some brief interludes of cooler air in the form of north westerlies but Sunday/Monday is just about the edge of the reliable - and even still, we don't know where, when exactly it'll snow during Friday and Saturday - but it's worth following where the high pressure currently over Greenland goes and the nature of low pressure systems around the British Isles then we could develop some sort of idea of what could follow. But in the meantime it's worth enjoying some lovely crisp weather early in the season with frosts and a risk of snow for some of us - it wouldn't have been possible a year ago. And some lovely sunshine to go with the autumnal colours too after what has been an overcast, drizzly and foggy week.

[SMU]

Evening guys-

Just a quick one from me-

Keep an eye on the UKMO trough at 48 through 60 on the 12z

A band of rain sleet & snow down through the UK sat eve..

Can someone link the europe 48 & 60 chart for clarity

S

[ICETAB]

The latest GFS run looks like it is coming in line with the ECM, with the blocking further west. I'm interested to know how the HLB evolves in the coming weeks. Could be an eastly down the line?

Edited October 24, 2012 by ICETAB

[andymusic]

The latest GFS run looks like it is coming in line with the ECM, with the blocking further west. I'm interested to know how the HLB evolves in the coming weeks. Could be an eastly down the line?

Think we're gonna have to wait and see how hurricane Sandy and tropical storm Tony affects the model set up 1st!

Edited October 24, 2012 by andymusic

[AWD]

Spot the UK!

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=186&code=code&mode=0&mode3h=0&runpara=0&carte=1

A rather unsettled run after the cold snap this weekend. Plenty of rain around for all, along with some windy days. Temps often on the cool side of average.

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=192&mode=0&carte=1