Winter Model Discussion 12Z 15/1/13 onwards.

[Stevetynant]

Please read the key, as you can see the cream/brown is the -5C upper temp, thats good for snow, and with the feed coming off the continent the dew points will be low=snow.

Please read the key, as you can see the cream/brown is the -5C upper temp, thats good for snow, and with the feed coming off the continent thedew points will be low=snow.

My apologies - thanks for pointing this out.

[Stuie]

Hopefully this will quash all the will it won`t it west/east etc. This is a guide, nobody knows what is going to happen.

[weatherguy]

Did someone order a split polar vortex?

Never before in the field of human conflict have so many owed so much to so few...Of course I refer to the SSW, thank you for paying us a visit!

[stainesbloke]

Epic Gfs 12z, I never thought a Southerly could be so cold

It's a run choc full of reloads of snowy weather with lows tracking into the resident cold pool over the uk. Blizzards on fri/sat.maybe even on sun/mon and more to come next week. Hoping the Ecm 12z has a similar angle of attack to the gfs. These are amazing charts for such a close time scale, surely the undercut is now the favoured option and a severe spell is on the way for a large swathe of the uk, white- out conditions would occur unlike anything we have seen in recent years, even dec 2010 would be eclypsed if the gfs 12z or something similar verified, heres hoping

Lol, that has to the most hyped up post I've seen today I'm remaining cautious, have seen similar set ups in the 80s which delivered nothing or rain in the end. Big potential is there for sure but at this stage that's all it is. If the charts are showing the same on Fri morning I'll start dusting off the sledge!

[cooling climate]

where's the break coming from dave ? i've yet to see convincing evidence that anything that falls over the weekend will thaw. each ecm run appears to cement the cold even further. very low heights and a succession of occlusions interspersed with cold slack deep troughing.

The trend continues I see further corrections south and undercutting,trough disruption.

A very cold and for many very snowy outlook with little sign that I can see of any

milder breakdown. Excellent runs this evening. very exciting times ahead.

[Rob K]

Just going to post the JMA but some members came to the wrong conclusion about the 12Z NAE.

As you can see at +48 the JMA is like the NAE.

http://www.wetterzen...ics/Rjma482.gif

Look what happens though at +72 when the front pivots.

The cold backs W. However SW England/S Wales would miss out.

http://www.wetterzen...ics/Rjma722.gif

II take your point but the NAE is much more progressive with the mild sector than JMA. NAE has 0C into mid Wales at 48hrs; JMA keeps it out in Ireland

[Frosty.]

The 12z runs this afternoon have ramp alerts stamped all over them, and it's all so close we can almost touch it. Friday remains the pivotal day as the fronts hit the entrenched cold block of air over the BI, I can now picture metoffice going through their various levels of alerts through to the highest level by fri/sat. If the far northeast of the uk miss the main disruptive band of heavy snow/gales, they will still get blitzed by snow showers as winds strengthen and pressure falls, the further n and east you are in the uk should be a safe bet to remain bone chillingly cold with either persistent snow or snow flurries/showers, the position of the main zone of high impact weather is still to be nailed, but it does now look like most of the uk will remain locked in cold air with severe windchill, penetrating frosts and either prolonged snow or snow showers.

[k19]

Is it just me who things the GFS has thrown up an odd temp. ensemble? Its an outlier right from the start for 2m temp?

[weatherguy]

Is it just me who things the GFS has thrown up an odd temp. ensemble? Its an outlier right from the start for 2m temp?

only thing i can think of is that the op is ran at a higher resolution, so will have more precise 2m temps in a set up such as what we have now (much higher temps not too far west from us while we still remain very cold)

Edited January 15, 2013 by weatherguy

[fiftytwodegreesnorth]

Quick question to Steve M or the other experts. am i right in thinking the charts for Friday and wkend are looking very similar to early Feb 96, which gave many western parts and the Midlands impressive snow depth 8 inches here in Brum. I seem to recall a low pressure system coming against a Scandi block then.

[UV-RAY]

The 12z runs this afternoon have ramp alerts stamped all over them, and it's all so close we can almost touch it. Friday remains the pivotal day as the fronts hit the entrenched cold block of air over the BI, I can now picture metoffice going through their various levels of alerts through to the highest level by fri/sat. If the far northeast of the uk miss the main disruptive band of heavy snow/gales, they will still get blitzed by snow showers as winds strengthen and pressure falls, the further n and east you are in the uk should be a safe bet to remain bone chillingly cold with either persistent snow or snow flurries/showers, the position of the main zone of high impact weather is still to be nailed, but it does now look like most of the uk will remain locked in cold air with severe windchill, penetrating frosts and either prolonged snow or snow showers.

That's nearly as bad as my ramp in the regionals Frosty, but if the models do verify then I believe this will be one of the snowiest periods of weather England and Wales will have seen for over twenty five years. Amazing charts and it's very rare I ramp.

[snowking]

For anyone still doubting snowfall potential from tonights ECMWF 12z, ive got access to the full suite

Dew points - sub 30F (damn americans, bear in mind 32F is 0c) for the whole run, bar some VERY limited periods of ~35F for the very far southern coastline, and some far south-western counties.

SK

EDIT - also add 850's to that. Sub 0c all the way through!

Edited January 15, 2013 by snowking

[AWD]

For anyone still doubting snowfall potential from tonights ECMWF 12z, ive got access to the full suite

Dew points - sub 30F (damn americans, bear in mind 32F is 0c) for the whole run, bar some VERY limited periods of ~35F for the very far southern coastline, and some far south-western counties.

SK

So in laymans terms, that suggests snow for everywhere except Devon/Cornwall & the south coastal line, regardless of 850hpa temps?

[snowking]

So in laymans terms, that suggests snow for everywhere except Devon/Cornwall & the south coastal line, regardless of 850hpa temps?

Yep - even in those regions you pinpoint above (could also add S Somerset and Dorset to those) it only temporarily raises above 0c

SK

Edited January 15, 2013 by snowking

[Paul T]

Pretty much all of the charts have been posted, but I will use the 12z ensembles to highlight something rather unusual.

I will take Somerset as an example, but other counties across England also apply.

The GFS 12z Ensembles show two very unusual points:

1) I have never seen such a range of member 850hpa's within 60hrs. This could highlight the uncertainty at the moment. However, the mean, control and operational are all tightly bunched so actually I believe the scenario progged is probably fairly accurate.

2) The Mean is consistent, unmoved and varies very little. Quite amazingly the mean fluctuates by only 2oC in the final 14 days of the run. That is remarkable and, again, I’ve never seen this before. Consistent cold weather is certainly on the cards!

We are most certainly entering, what could be, one of the snowiest phases of winter the UK has seen for many many years, and even decades?

After checking all charts over recent weeks with interest I have seen outputs act and behave in very unusual and odd ways:

The SSW and Negative AO have created a jet stream that, on paper, should be powered by huge convection fed by severe cold coming from Canada, but actually when it comes to the UK, it is uncharacteristically submissive. And I love how the models don’t really understand this until 72-96hrs!

Great model watching, it just needs to convert now.

[Frosty.]

Lol, that has to the most hyped up post I've seen today I'm remaining cautious, have seen similar set ups in the 80s which delivered nothing or rain in the end. Big potential is there for sure but at this stage that's all it is. If the charts are showing the same on Fri morning I'll start dusting off the sledge!

LOL i'm not the only one hyping up today's charts, they are EPIC and hopefully more of the same or dare I say even more severe tomorrow. It's more than just potential when you consider how twitchy the experts are now, it will be a nightmare to forecast where the highest impact will occur but it will be fun for all us snow starved weather fans, it looks like win win to me, either bitterly cold with snow showers and severe frosts or blizzards and gales, only the far west and southwest may escape the full force of whats heading our way.

Edited January 15, 2013 by Frosty039

[Zenarcher]

My summary on the models tonight using the GFS, ECM, UKMO, GEM, JMA and NOGAPS.

96 hours Saturday - All models continue to agree on high pressure building over our North and just making it into the East of Greenland,

We still have rather big differences on the Atlantic low to the South of Greenland the NOGAPS and UKMO have it more South than the rest like this,

Meanwhile the ECM, JMA, GFS and GEM want to hold it back a bit more and have it further North like this,

120 hours Sunday - The ECM, JMA, NOGAPS and the UKMO agree on some sort of low pressure system to sit to the West of the UK,

Then the GFS and GEM don't show a low like the rest do but instead a few low pressure systems and shortwaves a rather messy and complicated picture from them,

144 hours Monday - The same models that showed a low to the West of the UK at 120 hours now move it South East and either place it over Ireland or near Southern England in the Channel but I will add GEM has managed to show a low here as well and the GFS does have weak shortwaves around as well so they sort of agree.

What most show,

GFS and GEM's,

ECM 00z run did show a low to the South of the UK and I've just looked through the 3 hour data of its 12z run and shows the same thing although it has made changes it still brings a low in to the same place at the same time as before.

Overall - The models yesterday were just getting to grips of the high pressure building over our North now that they agree on that they have the messy Atlantic to sort out and we still have disagreements there at 96 hours despite that most do show something similar by 144 hours. The changes I see across all models is they don't show a massive deep low like yesterday the Atlantic overall seems to have been pushed back West slightly a sign of the models overdoing the Atlantic that some people on here suspected. A new thing they have picked up is will the low on Sunday and Monday really dig South agreement appears good on most models today and they do continue to look good.

Edited January 15, 2013 by weathermaster

[phil nw.]

Some off topic posts have been deleted.

A reminder to post in here only if it`s about the model outputs.

General stuff about snow and previous dumpings or anything unrelated to the outputs please post here.

Let`s keep this thread informative and useful for other members and indeed all our readers.

Thankyou.

[Rob K]

Quick question to Steve M or the other experts. am i right in thinking the charts for Friday and wkend are looking very similar to early Feb 96, which gave many western parts and the Midlands impressive snow depth 8 inches here in Brum. I seem to recall a low pressure system coming against a Scandi block then.

I don't claim to be an expert but yes this from Feb 1996 does have a lot of similarities if you compare to current output!

http://www.wetterzen...00119960206.gif

Edited January 15, 2013 by Rob K

[derrylynne]

Not so sure about that. It remains in the balance for Wales and SW England at the moment, still a lot to play for, with a few days left for the models to twist and turn, but it's Marginal. Albeit I foresee snow.

I see no balance here. In fact we have already had early blizzard alerts here in wales. It is often the case with these kind of synoptics the warm air is stalled. And could be stalled over wales and the Sw before sliding away. Time will tell but Wales is very much in the line of fire. Even if it snows hard then turns to rain for a short time before reverting to snow again. My thoughts are that I have seen these kind of chars all too often back in the 70's and 80's and in many case the cold wins hands down. Will have an even better idea this time tomorrow.

[SMU]

Quick question to Steve M or the other experts. am i right in thinking the charts for Friday and wkend are looking very similar to early Feb 96, which gave many western parts and the Midlands impressive snow depth 8 inches here in Brum. I seem to recall a low pressure system coming against a Scandi block then.

Yes they are - but they are probably a bit faster through the UK than 96-however thats what John kettley said about 3 days before - I still have that forecast on VHS tape somewhere-Then 1 day before they suddenly forecast it would grind to a halt over london up to Aberdeen-then on the day it stopped 5 miles from Kent....S

[Essan]

Is it just me who things the GFS has thrown up an odd temp. ensemble? Its an outlier right from the start for 2m temp?

Looks like a glitch

This is for the SW Midlands from Wetternzentrale - OP run is right in the midst of the ensembles

[Rob K]

Looks like a glitch

This is for the SW Midlands from Wetternzentrale - OP run is right in the midst of the ensembles

Kev's pic was a 2m temp ensemble rather than 850s. Only thing I can think is higher resolution vs the ensembles??

BTW a question for anyone who knows - does ECM model run at finer time intervals than the 24hrs we see?

[Gibby]

Good evening. Here is tonights look from my perspective of the 12z output from GFS, UKMO and ECM for tonight Tuesday January 15th 2013.

All models are fairly much in agreement for just the next couple of days tonight. High pressure over Scandinavia is pushing a ridge SW towards Southern Britain holding at bay for now Atlantic fronts and depressions to the West. The weather will be cold with severe overnight frosts, especially over snow cover in the East where freezing fog could also form overnight. By day there will be some sunny spells with temperatures near to freezing or a little above away from snow cover or freezing fog. A few further snow showers could occur near the SE coast and along channel coasts tomorrow and Thursday as winds veer more to the SE and freshen somewhat in the West.

GFS then brings in a series of disrupting troughs from the SW into Southern and Southwestern Britain with widespread disruptive snowfall over Friday and the start of the weekend. Some milder weather will infiltrate into SW areas later as winds fall light and widespread fog forms over the snowfields. Snow will move North to other areas too but may not be so heavy as further South. Through the early days of next week the cold weather returns to the far South for a time before a renewed thrust of Low pressure from the SW brings the risk of further snow and sleet to many areas, probably turning to rain later across the South. Through the whole of FI in fact the pattern remains very knife edged between cold and snowy weather or less cold and rainy conditions with the difficulty being predicting where that boundary will be as Low pressure continues to move into the South of the UK and disrupts against the cold block further North and East.

The GFS Ensembles show a rather cold couple of weeks for many. The operational is very much on the cold side of the pack for Southern locations indicating more members have the boundary between the cold and mild rather further North than the operational shows. Northern locations continue to see tight agreement between the members on the run as a whole. Precipitation is shown for all areas from the end of this week indicating Low pressure being present.

The Jet Stream shows a slack Northerly flow down over the UK for a couple more days before a strong flow surge moves out of the States, across the Atlantic to reach Europe close to France later in the week and weekend.

UKMO for the weekend shows a cold and raw start to the weekend following a very snowy day on Friday in the South and West. After the first area of snow dies out a renewed thrust of energy moves NE into the SW by Sunday but this looks like being rain in the far South and West with a thaw setting in while areas further North and East have their turn for copious snowfall causing disruption in places. By Midday on Monday Low pressure is just West of Ireland with the cold and raw SE winds restricted to Scotland by then with a very unsettled and less cold regime with rain or heavy rain showers likely for much of England and Wales.

ECM shows a complex pattern of mild vs cold throughout the latter end of its run. It too shows a snowy Friday for the South and West as a trough slides SE over the SW carrying a significant period of snow for some. This might turn to rain before dying out later in the day leaving a lot of dull and foggy weather over the hills. Through the weekend a repeat performance looks likely of Friday though the rain to snow boundary would be slightly further North as shown meaning many Southern parts of Britain would more likely see rain rather than snow. Through next week the pattern persists with further disrupting Low pressure sliding SE over Southern England and maintaining a very bleak outlook for many in the North with major disruption from blizzards should these charts come off. The far South will also run the risk of some snow at times with some transient milder interludes with rain rather than snow.

In Summary the weather couldn't be more interesting over the coming week or so and possibly beyond. There is a strong chance of major disruption over the UK from Friday onward with blizzards a distinct possibility over many parts of the UK at various times of the output. There is a growing trend tonight from both ECM and GFS of the pattern of disrupting Low pressure crossing close to Southern Britain continuing for the foreseeable future with the path and position of these depressions as they pass totally responsible for the type of weather experienced at the surface. To the North of them would be cold and strong ESE winds while to the South a lighter SW flow would bring less cold air in at times, at least to the South. A couple of 100 miles further North or South for these Low pressures could totally change the weather in any one place over the coming week or so.

[zubzero]

Kev's pic was a 2m temp ensemble rather than 850s. Only thing I can think is higher resolution vs the ensembles??

BTW a question for anyone who knows - does ECM model run at finer time intervals than the 24hrs we see?

Up to T144 yes

http://en.vedur.is/weather/shipping/atlantic/#type=prec