This morning's GFS OP may raise a few eyebrows this morning.
ECM also re-develops an easterly from +216.

And if you live in the Midlands and fancy a virtual snowstorm, have a look at the GFS control.

One run, one day and all that

The GEFS also look more interesting this morning. (Even the London snow row has managed to tick up to 3 )

Brian the snow row numbers, what does it actually represent. chance of snow? Snow depth? Is it on a scale so 10 means blizzard and whiteout conditions and 1 being a flurry. Any guidance would be most helpful.

Little support at present from GEFS for the easterly between 240h and 360h.Atlantic : Anticyclonic 70:30

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY MONDAY NOVEMBER 24TH 2014.

NEXT UPDATE TUESDAY NOVEMBER 25TH 08:00

THE CURRENT GENERAL SITUATION A ridge of High pressure over the UK currently will become weaker as a warm front moves North over the English Channel tomorrow.

MODELS-2 WEEK HEADLINE Generally uncertain conditions seem likely with the East vs West battle lines drawn. Some rain at times for all but a fair amount of dry and benign conditions too. While not warm it won't be especially cold either.

THE JET STREAM ENSEMBLE FORECAST The GFS Jet Stream Ensemble forecast shows the weak flow around the UK at present persissting until later in the week when the flow strengthens across the UK with the flow moving South late in the period to a point South of the UK.

GFS OPERATIONAL The GFS operational this morning shows High pressure to the East and later NE continuing to dictate the UK weather pattern. Disrupting Low pressure to the West of the UK later this week allows a strengthening Jet flow to ride over the Northern flank of High pressure over Europe around a week from now with a period of windier and wetter weather as a result before new High pressure builds across the UK towards Scandinavia later and brings a return to dry and cold weather briefly to the North and East while the South and West become under the influence of Low pressure moving SE to the SW of the UK with strong and chilly SE winds and rainfall as a result.

THE GFS PARALLEL RUN The GFS Parallel run also keeps High pressure to the East and NE well incontrol of the weather around the UK throughout it's morning run. The South of the UK in particular remains under threat of Low pressure at times either feeding up from the South or down from the NW with some rain at times here. Towards the very end of the run High pressure transfers to mid Atlantic and with an Azores Low pressure then a cold North flow for the UK could be just around the corner from the term of the run.

THE GFS CONTROL The GFS Ensembles take the operational run's route through Week 1 before a High pressure build across the UK based from the Atlantic crosses further NE later to Scandinavia at the same time as deepening Low pressure moves across the Atlantic towards Southern Britain. Colder air having moved West from Europe then is shown to engage with milder Atlantic air near Southern Britain to form an intense Low complex over Southern Britain and Northern France late in the run with gales and heavy rain the result and with moderately cold air close by sleet or snow could result in places

THE GEFS ENSEMBLES The GEFS Ensembles end this morning with the UK lying in a trough stretching from an Atlantic Low South of Greenland and down towards the Meditteranean indicting little overall change from the current pattern.

UKMO UKMO today shows a complex syoptic pattern late next week as High pressure to the East remains resilient and possibly realigns itself further North at the end of the run. Disrupted Low pressure to the West late in the week fails to cross the UK with rain held out to the West before a new ridge of High pressure next weekend keeps things dry if rather cloudy with some fog and frost patches in the South especially should skies clear overnight.

THE FAX CHARTS The Fax Charts continue to show High pressure out to the East holding up the natural West to East progression of troughs and Low pressure across the UK. Instead we lie in nomansland with decaying fronts either to the West or over the UK decaying in situ as winds slowly warm and freshen from a Southerly quarter later in the week.

GEM GEM this morning likes the idea of the disrupted Low pressure system to the West of the UK later this week developing it into a cut off Low to the South at the weekend. At the same time a UK ridge slips South in response to an increased Jet flow crossing the North Atlantic and into Northern Europe gradually strengthening a mild SW flow later with occasional rain spreading progressively South and East across the UK with time early next week.

NAVGEM NAVGEM shows a complex synoptic structure across the UK next weekend between High pressure to the East and SW and Low pressure up to the NW and SE with no one system having overall control. The resultant surface conditions would be variable as a result with all areas at risk of some rain but drier spells too in average temperatures overall.

ECM  ECM this morning also shows a cut off Low feature over Spain at the weekend while the UK in centre ground to a ridge from an European High to another one over the Atlantic. Fairly quiet if rather cloudy conditions are likely as a result with patchy fog an frost at night possible. Then through next week the Spanish Low moves North and High pressure to the West ridges across to Scandinavia strengthening an Easterly flow across the UK. Though chilly no real cold air is available to tap into at this stage so with thick cloud for many and a strong breeze it will feel chilly and uninspiring with rain at times for many especially towards the East and South.

THE ECM ENSEMBLES The Ensemble run shows Low pressure still close to Southern Greenland all the way down to the Meditteranean Sea with High pressure based over Eastern Europe and Scandinavia. The UK lies in nomansland with indeterminate conditions but not especially cold.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The trend is steadily returning to High pressure remaining the driving force to UK weather over the period with the positioning of such instrumental in determining air source and weather type which is currently variable between the models today.

MY THOUGHTS A day off from the models yesterday has done nothing to alleviate the pattern that we are at currently and may stick with for some time to come. The main focus of attention is still the persistence and strength of the High block over Europe warding off attacks of Low pressure from the West and sending a cut off Low down to Iberia later in the week. This leads the UK in a slack ridge both from the High to the East and a new one out in the Atlantic. It's the movement of this one which could prove interesting as some output take it through Scotland to Scandinavia and sets up an Easterly flow over the UK. With pressure forced towards the South and SW of the UK because of this pattern would normally introduce a real risk of heavy snowfall and very cold weather being that we are now entering December soon. However, with a few exceptions due to the orientation of High pressure over Russia very little deep cold lies over Europe at the moment and as a result just chilly weather with rain is still the more likely option rather than snow. There are some exceptions to this general rule of thumb though and these in themselves have increased in number over the last few days. No one can doubt that the synoptic pattern is fascinating at the moment and it is a mile away from the pattern of last Winter with this early season standoff between East vs West very marked albeit and although meaning nothing to the UK currently in weather terms I believe that as the season deepens it is only a matter of time before things become better orientated to bring the UK at least a shot of cold weather soon. I think there is one word which is going to have to be adhered too though while all this drama unfolds and that is 'patience' but at least we have a whole Winter season in front of us still so with the synoptics as they are I feel we couldn't be better placed.

The snow row in the footer shows the number of computer model runs forecasting snow at any give time in the selected location. This can range from 0 to 23. It is a forecast so can be wrong, but 0 suggests snow isn't at all likely and 23 means it is. 

There's info about this on the probability forecast pages:

http://www.theweatheroutlook.com/twoforecasts/ensemble-forecast.aspx

I always do a little dribble when I see the GEFS start banging out the snow symbols ...But I only ever take it seriously at t48

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=306&y=141&ville=Londres

Thanks! If Plymouth ever got to 23 I reckon the next ice age will be upon us!

Lol! Indeed.

Two weeks out I know, but worth a link:

http://www.wetterzentrale.de/pics/Rtavn3361.gif

The last time the Polar Vortex gave us a visit I believe was December 2010 .... if anything this seems more intense, though not as cold... Higher ground and favoured spots would get a pasting though!  Will be interesting to see if this is a recurring theme or a one-off FI tease.

GEFS6z tend to hand the initiative back to the Atlantic. 

A few more of them snow symbols showing on the GEFS lol

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=306&y=141&ville=Londres

Less runs on the GEFS6z going for a snow risk in the south east but still some interest with a couple of runs holding 850s down for a while.

Is there factual evidence available for this? Every winter we get told certain runs favour certain outcomes and I've read from forecasters before that that's nonsense. Not discounting it myself as I'm not sure, but where is the proof of this, and more importantly, if it is accurate - why?

Anecdotally I always thought the 06z favoured cold/blocked conditions. But recently I've heard I was completely wong (not for the first time)

Anyway, here's today's video update;

Chance of a cooler start to December + More on BCC winter update:

http://www.gavsweathervids.com

A lot going on but a lot of uncertainty. 

Is that equivalent to the 18z rolling out of the pub after a few pints?

It's the same model as the 0z, 12z and 18z so how can that be the case?

There was a time a few years back when I thought that many GFS 12z runs were weighted towards atlantic mobility during the winter months. I think it's pretty much down to people's perceptions, rightly or wrongly.

Hi all, I am new here. My first post

As far as I know there are two routine radiosonde launches every day at 0000 UTC and 1200 UTC which are included in the 00z and 12z runs. Therefore those runs include actual updated atmospheric data. It could well be that the 6z and 18z tend to the default mode as per the absence of real data... and consequently the 00z and 12z should be more reliable... I'm just guessing here guys

I know these things crop up from time to time. In reality, surely the only differences can be in the quantity and quality of the input data? As Brian says the model (i.e. the program behind it) is the same on all runs, but the data may be more or less complete. I would guess that there may be data variations that are similar every day, so it may be that say the 18 may always miss a certain set of data, and that this in theory could result in persistent biases in one way.

All of that should be taken with a pinch of salt...

As others have said the current evolution and state of the synoptics is totally different from last year. I would also note the massive overhype of the cold snap in the States, coupled with the Lake-Effect snow in the NE states, as leading people to think we were set into the same problem of endless cyclogenesis in the atlantic heading our way. We are not yet in December and there are interesting times ahead.

I've heard it said that the 06z gets a bit less data which leads to such bias, but I have no idea whether that's true or not.

After a morning's break from the models, I've nearly caused myself some kind of hernia of the mind taking in all of the different options available from the models so far today 

Thankfully, the breaking down of the polar vortex remains a consistent theme, though some get there faster than others.

The majority vote now points towards some form of easterly influence for a time at least as the lobe over Greenland loses some of its punch.

The intensity and duration prior to about 10 days from now both depend on how much energy fires northeast days 5-7. The GFSP and UKMO 00z runs both showed the Atlantic hitting a wall, and GFSP went on to bring several days under a bitterly cold easterly flow.

The GFS 00z run showed the benefits of the Greenland lobe collapsing, with the Atlantic troughs disrupting and energy sliding SE, allowing the block to the east to bring a few days of continental cold, but this arriving outside of the 10 day range.

The ECM 00z run really shuts down the Atlantic days 8-10 and is consistent with it's 12z run of yesterday; we again see trough disruption in the Atlantic looking to build heights from Iceland to around Svalbard going forward, in fact it looks more convincing this time around.

The great thing about having the polar vortex break down so much is that every one of the above runs finishes with lots of potential for further cold outbreaks down the line.

The GFS 06z op run has the least such potential on the face of it, but factor in that GFS has a habit of giving the jet too much energy and positioning it a bit too far north in lower-res, and you're looking at something far more promising 

The GFSP 06z carries greater potential from the end of its op run, though the worst possible positioning and extreme intensity of an Atlantic trough days 14 and 15 leaves the deep cold air mass a lot of ground to cover. Good thing that storm system is right on the edge of what's feasible!

To summarise, very encouraging output so far today as far as the longer term (i.e. the middle part of December) is concerned, and with a potential bonus cold spell in the 10-14 day time frame if we get lucky.

Here's to some epic 12z op runs to gawp over - you never know!