Winter Model Output Discussion - 06Z 09/02/13 onwards

[Coast]

Good morning all.

The last thread became a complete nightmare and was ultimately less about the model output than many other threads we have available. It really is quite straight forward as the topic title hints at.

Please ensure you read your comment or analysis before you post it as this will save us removing it if:

• It doesn't have relevance to the model output
  
• It is rude or discourteous to other members or their posts
  
• It adds nothing of value in moving the conversation on or expanding discussion/analysis of the models
  

Please remember that this is currently the most popular thread on the forum and is being read by a multitude of people with mixed abilities and understanding. Everyone would like to hear your view if it is about model output and what that might bring for our weather.

Thanks

[Methuselah]

And here is the ramping and whining thread:

[london-snow]

Today's runs are going to be vital regarding sundays potential snowfall.

Overnight runs bring the south east into play with possible snow showers or streamers following on going by the chart ryan posted.

Be very interesting to hear Ian F views in terms of what the met make of the overnight runs.

Going to be glued to this place all day now i feel.

Edited February 9, 2013 by london-snow

[Gibby]

Good morning. Here is the morning report of the 00z output from GFS, UKMO, GEM and ECM for today Saturday February 9th 2013.

All models show an agreed pattern between now until midweek. A warm front lies North/South across Central UK with outbreaks of rain and sleet with light snow over the highest hills. This will change little through the day. It will feel cold in the East but with temperatures nearer normal in the West. Tonight sees a more vigorous frontal system move into the West of the UK with rain following quickly behind with a strengthening Southerly wind. The rain then marches on North and East across the UK tomorrow turning to snow later in the day across Northern and Eastern areas, possibly giving disruption over Sunday night and into Monday before the whole system pulls away SE clearing the rain and snow away from Southern areas to leave the UK under a cold and raw East flow to start the working week with some wintry showers in the East. By midweek a new frontal system is approaching the West with rain and hill snow reaching the far West of the UK later on Wednesday.

GFS then shows rain moving over all areas with some hill snow in the East on Thursday while the West sees milder weather with rain clearing to brighter weather with perhaps a few rain showers. Through the weekend and start to the following week further troughs move in from the West with more rain at times with the less cold conditions making it just about all the way over to the East removing the risk of further snow even over the hills for a time. Later in FI further disrupting Low pressure continues to slip SE over the UK but thanks to the ever present and strong Azores High the UK lies mostly too far West to see anything of significant wintryness with cold rain at times with just snow over the highest ground in winds from an Atlantic origin for the most part.

The GFS Ensembles show a fairly average spread between the members this morning though there are some colder options on the table. The operational above was one of the milder options for a time after the mid run point with rainfall gradually reducing in amount and frequency later in the run.

The Jet Stream is currently undergoing a realignment over the coming days changing from a North/South flow over the UK to a SE moving flow just to the SW of the UK where it continues to move down to a stronger flow running East over Southern Europe.

UKMO for shows from midweek a front moving East bringing rain and temporary hill snow across from the West followed by a run of Westerly winds and rain or showers to end the working week in temperatures not far from average.

GEM shows milder conditions too spreading down from the NW later next week with the weekend becoming quite mild under a SW flow with Low pressure to the North and High to the South. Some rain would occur here too though Southern areas would likely stay dry and relatively mild if cloudy and breezy.

ECM today shows a further Low pressure midweek bringing rain and showers across all areas around Wednesday and into Thursday followed by a showery NW flow for a time with some wintry showers possible over Northern hills for a time and the SE too later. Thereafter, High pressure from Scandinavia to the Azores link up to form a UK centre when dry and sunny days with frosty nights would develop providing air around the top of the High stays sufficiently cloud free in the light West flow over the North.

In Summary today whichever way you look at it there seems to be a moderation in any cold weather as we move through next week. While the risk of snow is still very real for many Northern and Eastern areas early in the week the trend thereafter is increasing for milder air to eventually win it's way all the way over to the East with rain at times for all. The basic upflow pattern though remains somewhat blocked by the Northern European High with everything shunted East by a couple of hundred miles keeping much of Europe cold and snowy. ECM does buck the trend still bringing High pressure right over the UK keeping things rather colder perhaps but despite frosty nights the days would feel pleasant enough in the ever strengthening sun's power.

[Frosty.]

A really snowy spell developing during sunday, especially for the midlands, parts of wales, into northern england, even some snow for london and more especially kent, also an increasing risk of snow showers for eastern scotland as the Easterly winds increase. Tonight though it's rain which will be pushing into the west and southwest and then spreading northeastwards but as colder continental air starts to be sucked into the flow, the rain will turn to sleet and then by tomorrow afternoon and evening, to heavy snow and travel looks like becoming difficult, I reckon the monday morning rush hour will be very hazardous for the areas mentioned above and perhaps other areas too. The Ecm 00z shows the cold block coming under a vigorous attack next wednesday as a low carves it's way through and pushes the block east but the cold block/scandi high regroups and comes back stronger for the east and southeast, the northwest of the uk, especially the far northwest looks like becoming milder with wet and windy weather from midweek but then the ecm shows a more anticyclonic spell with widespread frosts for most areas but the far northwest and north look to have a milder/moist atlantic flow around the top of the high later.

Edited February 9, 2013 by Frosty039

[bobbydog]

most of the models seem to have the low further south on these runs, e.g. the ECM-

which is only just beginning to form on this chart (midnight tonight)

the BBC forecasts as to where snow will fall will probably be near the mark but still not decided as yet.

incidentally, its snowing heavily here! (not settling yet though)

edit- ok i posted the wrong ECM chart. its not looking as good but that one could still be as right as any at this stage!

Edited February 9, 2013 by bobbydog

[TEITS]

Judging by some of the posts I feel I need to advise some caution.

Firstly the Sun/Mon event doesn't look like bringing heavy falls of snow simply because the snow ratio is going to be poor. Infact when it actually comes to accumulating snow then E Scotland maybe N England could see greater amounts via the convective E,ly and colder upper temps. What you have to realise is technically you can have greater snowfall amounts from 5mm of precip than 20mm if that 5mm fell under conditions where we have a bitter convective E,ly with upper temps of -15C. I also see the dreaded "Streamer" word has cropped up and at the moment E Anglia/SE doesn't look favoured for any heavy convective snow showers because the models have downgraded the extent of the cold -10C E,lys that followed the LP sinking S. However like I say for Scotland and parts of N England the colder E,ly flow could bring these heavy snow showers.

As im typing the 0Z NAE corrected SW but actually the 06Z has surprisingly moved NW!!

http://expert-images...021018_0906.gif

Edited February 9, 2013 by THE EYE IN THE SKY

[Frosty.]

most of the models seem to have the low further south on these runs, e.g. the ECM-

which is only just beginning to form on this chart (midnight tonight)

the BBC forecasts as to where snow will fall will probably be near the mark but still not decided as yet.

incidentally, its snowing heavily here! (not settling yet though)

bobbydog that is the 12z ecm

[bobbydog]

bobbydog that is the 12z ecm

[Gustywind]

East mids looks best placed on 06z nae for tomorrow following a predictable shift back nw in precipitation, but it all still looks pretty uneventful to be honest, with rain or sleet for most of the south, hard to imagine much in the way of accumulation even where it does snow.

[Ryan Dutch Weatherman]

Ensemble for my country , its a complete mess the EC ensemble s.

Big spreading , unsure after 13e februari .

[NickR]

Judging by some of the posts I feel I need to advise some caution.

Firstly the Sun/Mon event doesn't look like bringing heavy falls of snow simply because the snow ratio is going to be poor. Infact when it actually comes to accumulating snow then E Scotland maybe N England could see greater amounts via the convective E,ly and colder upper temps. What you have to realise is technically you can have greater snowfall amounts from 5mm of precip than 20mm if that 5mm fell under conditions where we have a bitter convective E,ly with upper temps of -15C. I also see the dreaded "Streamer" word has cropped up and at the moment E Anglia/SE doesn't look favoured for any heavy convective snow showers because the models have downgraded the extent of the cold -10C E,lys that followed the LP sinking S. However like I say for Scotland and parts of N England the colder E,ly flow could bring these heavy snow showers.

As im typing the 0Z NAE corrected SW but actually the 06Z has surprisingly moved NW!!

http://expert-images...021018_0906.gif

WHat's your take on that convection TEITS? Yesterday it looked very watered down on GFS and ECM (uppers too warm), with only the UKMO offering good news. Would you feel more confident of some proper convection for E Scot/NE Eng based on today's charts?

[weatherguy]

Ensemble for my country , its a complete mess the EC ensemble s.

Big spreading , unsure after 13e februari .

Interesting to note that pretty significant cluster of ensembles going for that sub-zero region throughout that run...That being said, with a situation such as this where a couple of hundred miles can make all the difference between bitterly cold/milder conditions, I don't think ensembles for De Bilt (I presume?) are quite as useful with regards to the UK's conditions over the coming week or so.

[nick sussex]

I wouldn't be reading too much into the NAE precip accum. That's been well out even at T6hrs!

Also the arc of precip associated with the frontal zone can be difficult to pinpoint, if you factor in some margin for error its looking at the moment that the northern boundary is around Manchester.

In the medium term the UKMO looks dire with a very flat pattern, the ECM a bit better but at the moment still taking the next low too far east before cutting it se,it does bring high pressure from the east back into play in the mid range but we'd need to see the pattern further west thereafter it has a crumb of interest at 240hrs with a chance of some pressure rise to the nw but really I'll believe it when I see it.

The GFS just really drab and uninspiring throughout, certainly if we have any hope of finishing the winter on a high then we need to see either a strong Greenland high which given the winter so far looks very unlikely or a strong Scandi high with a decent cold pool and as we've just seen as soon as a decent cold pool looks like appearing the models push the high too far east.

;

[lorenzo]

To save some chart hopping here are the last 4 NAE runs for Sunday 1200 hrs in GIF format starting from when the low first came into range, show the initial projection taking a jump west and remaining pretty focused on the eventual track.

Then the 3 remaining available charts out to Sunday evening, before it turns and delivers for sections the East Coast.

For comparison UKMO fax from 5am.

It looks to my eye that the bigger track changes were dialled in by the model in yesterday output, that being the drop slightly south and to the west.

Am sure most will have this bookmarked but just incase http://www.yr.no/satellitt/europa_animasjon.html will be the way to watch this one, hope Ian F manages to drop in with some UKMO charts today.

[Summer Sun]

Thursday continues to look like the day we'll loose this cold air and see a returning of something milder but wetter for a time

Pressure then slowly rises as the milder air spreads across the country

[Captain Shortwave]

I wouldn't be reading too much into the NAE precip accum. That's been well out even at T6hrs!

Also the arc of precip associated with the frontal zone can be difficult to pinpoint, if you factor in some margin for error its looking at the moment that the northern boundary is around Manchester.

In the medium term the UKMO looks dire with a very flat pattern, the ECM a bit better but at the moment still taking the next low too far east before cutting it se,it does bring high pressure from the east back into play in the mid range but we'd need to see the pattern further west thereafter it has a crumb of interest at 240hrs with a chance of some pressure rise to the nw but really I'll believe it when I see it.

The GFS just really drab and uninspiring throughout, certainly if we have any hope of finishing the winter on a high then we need to see either a strong Greenland high which given the winter so far looks very unlikely or a strong Scandi high with a decent cold pool and as we've just seen as soon as a decent cold pool looks like appearing the models push the high too far east.

I want to ask you something which is related to what you said here (latter part), any other more experienced posters feel free to answer this if you want.

It appears when we do get a decent looking Scandi high, the high just seems to retreat eastwards with any real force put on it, I find it rather odd as it's not exactly the jet riding over the top of it and sinking, it's just moving away by its own free will. Why is this? Probably a stupid question but it's kind of baffling me that I would have thought our odds of a good cold spell would have increased from a few days back but the case seems to be the reverse. Cheers

[winterof79]

Thinking a bit of orographic snowfall for the eastern upslopes of the Pennines

http://expert-images.weatheronline.co.uk/daten/proficharts/en/nae/2013/02/09/basis06/ukuk/prty/13021018_0906.gif

http://expert-images.weatheronline.co.uk/daten/proficharts/en/nae/2013/02/09/basis06/ukuk/pslv/13021021_0906.gif

[phil nw.]

Not such a big deal for snow looking at the latest runs.Less pptn. and very marginal conditions suggest that lying snow will be reduced and more restricted to higher ground Sunday to Monday.

http://expert-images...021106_0906.gif

Rather disappointing but does underline the latest BBC TV forecasts this morning showing less of an event through Sunday.

It does look as if our cold air will be gradually eroded through this coming week with the block to our NE too far away to stop a weak Atlantic moving in from around Weds.

We can see on the UKMO chart at T120hrs this expected pattern

http://cdn.nwstatic..../00/met.120.png

A similar picture of the next low moving in further north is shown on the GFS and ECM too.

At the moment it`s difficult to see where a renewal of cold will come from as each weak attack from the west simply mix`s out the coldest air.It looks likely it will remain below average but the real cold is held just a couple of hundred miles further east and the pattern does not promise any way of bringing this west at the moment.

http://www.meteociel...0-192.GIF?09-12

http://modeles.meteo...-21-0-192.png?0

Unfortunately this seems to have been the setup for much of the last few weeks with the UK on the margins of real cold.Many of us got lucky in January but this time i it looks like a brief and modified 2 day snowy spell for a few before a gradual less cold period.

[TEITS]

Just want to echo Nick S comment about the NAE precip prediction being rubbish because I have also found this to be the case. Whats rather worrying is how often the BBC forecasts reflect the NAE output, remember the farce last Feb? I said at the time the NAE was wrong and it took the BBC/Met O 15hrs to agree with me. If anyone is wondering what im on about im referring to the snowfall that hit the E Midlands instead of the W Midlands. The NAE was wrong at 0+ due to a difference in the actual radar.

These are the charts you want to follow in my opinion.

http://www.wetterzentrale.de/pics/Rmgfs423.gif

The NE extent of the snow appears to be Lincs. Even for my location its getting close!

[nick sussex]

I want to ask you something which is related to what you said here (latter part), any other more experienced posters feel free to answer this if you want.

It appears when we do get a decent looking Scandi high, the high just seems to retreat eastwards with any real force put on it, I find it rather odd as it's not exactly the jet riding over the top of it and sinking, it's just moving away by its own free will. Why is this? Probably a stupid question but it's kind of baffling me that I would have thought our odds of a good cold spell would have increased from a few days back but the case seems to be the reverse. Cheers

Good question, well the high isn't that strong and theres no strong signal to retrogress the pattern so you've got a weak jet ambling along and we see some disruption close to the UK.

In the latest GFS a smidge of interest at around 120hrs with more trough disruption but we need more amplification and a clean break with the upstream energy.

A much better GFS run so far with more amplification and it finally clears the shortwave energy se, not bad and I think we really need to see this trend gather steam.

Edited February 9, 2013 by nick sussex

[TEITS]

.

In the latest GFS a smidge of interest at around 120hrs with more trough disruption but we need more amplification and a clean break with the upstream energy.

I know its the 06Z but my word what is going on here.

http://www.wetterzentrale.de/pics/Rtavn1381.png

Maybe I should keep an open mind for the following week because the 06Z is such a massive change at such an early timeframe.

[winterof79]

06z better with a push from the east http://www.meteociel...&mode=1&carte=1

EDIT beat me to it EYE.

Edited February 9, 2013 by winterof79

[winterof79]

Mmmm.... http://modeles.meteociel.fr/modeles/gfs/runs/2013020906/gfsnh-0-144.png?6

Ridging evident.

[TEITS]

I don't have any time to view the rest of the run but the difference in the 06Z is incredible.

Hope this is a new trend because I don't think i've seen such a change between runs at this short timeframe, really extraordinary.