Model output discussion 25th Jan onwards

[Jason M]

Looking through the early ensembles the opp run is probably amongst the worst option on the table. Also the control is better.

Obviously can't completely disregard the opp, and ECM is also poor. Personally though I think the block will be more robust. Will it lead to lots of snow away from high ground and the NE? No, in my view but I'm much more interested in mid feb to be honest.

Edited January 26, 2014 by Jason M

[Alpine glow]

I see it different, logic says that the second possible slider should go SE, however there is no room for it to undercut. Look at the chart:

 

gfsnh-0-150 (1).png

 

Thank you I learned something with your explanation of that chart.

[Captain Shortwave]

I see it different, logic says that the second possible slider should go SE, however there is no room for it to undercut. Look at the chart:

 

gfsnh-0-150 (1).png

 

We have a Russian high, if it was a Scandi high the lows could slide under, with a Russian High the lows can only dig the upper trough deeper till it fills. This means further energy from the PV will be sucked east/NE as there is no room at the Inn. Some still leaks into the s.euro upper trough and this can only have one result, combined with the energy going east, is to push the Russian high east:

 

gfsnh-0-192 (2).png

 

By then the surface flow has reacted to the main upper flow pushing east and we end up back in a zonal flow. The GEFS for the last few days have clustered this solution. Not an outlier solution to me.

 

GEM solves this by having the Arctic High link with the Russian High dragging the block further north and the upper trough then has room to undercut that block:

 

T180: gemnh-0-180 (1).png  T240: gemnh-0-240 (11).png

 

We know if the Russian block is pushed aside FI on the GFS has been consistent with a return to zonal for the first week of Feb.

 

T384: gfsnh-0-384 (.png

 

So knife edge stuff.

Nothing wrong with a difference in opinion for sure, as always there is method to why models will show a solution based on looking at the European picture in fine detail, though I am unconvinced that the low would simply sit over Scotland and not at least try to drain into the trough over the Mediterranean. 

The operational for the 06z was like Jason M suggested probably one of the worst solutions out of the suite with the ensembles going for something a lot cleaner (more the way I envisioned anyway)

Clear movement south east of that low as opposed to stalling over the UK.

Mean temperatures look good in the north, more knife edge in the south with 850s around -2ish. 

 

Long term there is big support for a strong block north of Alaska for the foreseeable future

That's a huge signal for that to be in place. 

ECM not as strong but there is a definite positive anomaly up there

If the Scandi high remains persistent as it has and with a strong block well forecast over the other side of the pole. Then there is a good chance of keeping the two lobes of the tropospheric vortex separate and hopefully weakening the Atlantic jet somewhat. 

Edited January 26, 2014 by Captain shortwave

[Cloud 10]

Looking through the early ensembles the opp run is probably amongst the worst option on the table. Also the control is better.Obviously can't completely disregard the opp, and ECM is also poor. Personally though I think the block will be more robust. Will it lead to lots of snow away from high ground and the NE? No, in my view but I'm much more interested in mid feb to be honest.

 

A nice "slider" ens. mean at 144 hrs from the gfs,and even more encouraging

as its the 06z!

 

[Purga]

That looks excellent. Pleasing to see serious scatter after the 1st. That to me doesn`t look like the Atlantic piles in easily to spoil the party.

Well comme ci comme ça, Some of the ENS are good with sliders evident, see the Control

 

On the other hand the longer term ECM ENS for Debilt are not so tasty

 

 

But a lot of 'Shannon ....' so at least the more immediate term looks of interest.

[Tamara]

Ha Ha so the UKMO changes its mind from last nights awful 12Z and goes back to having the block further W than the ECM/GFS. Before anyone says the ECM/GFS is more likely to be correct then lets cast our minds back a bit.

 

At +72 all models agree with the LP sinking S. However it was the UKMO that modelled this consistently, whilst I recall the ECM & GFS especially flapped around with this. I should add the JMA was also consistent with this.

 

Trying to base a forecast on the output is a nightmare to be honest. Now like I said yesterday I wasn't convinced of a classic type E,ly i.e cold uppers, snow showers because the block would not be far enough W. However I certainly don't buy the W-E movement of LPs and SW,ly winds like the ECM is showing. I still feel the likely outlook is the block will prove more resistant and LPs will be sliders which will increase the risk of snowfall and keep the UK on the cold side.

 

The GEM is my favourite this morning as we see a slider followed by the block advancing W!

 

http://modeles.meteociel.fr/modeles/gem/runs/2014012600/gem-0-240.png?00

 

.

Yes this is what I am thinking as well I've been on the trough disruption trail for a while now anyway and continue to see this process as the fulcrum around which future changes in the pattern occur.

 

Some of the analysis this morning has too much face value reaction to individual model output and whilst I recognize that this will always be a regular feature of this thread, then there is also always a place to try and be consistent and keep perspective of the trend ahead that too easily gets masked by intra day/output reaction.

 

Some concern expressed about the role of the Azores High in our sector of the NH and how any amplification of it may serve to send energy eastwards. There is continuing suggestion that the downstream pattern will be influenced by forthcoming changes upstream, and on the basis of likely continued trough disruption and energy being diffused NW-SE and the Azores ridge being displaced westwards, as changes feed through from the Pacific side, then whilst its certainly possible that phasing of energy may provide flatter outcomes to push the pattern eastwards, on balance its hard to see a path to High pressure re-asserting itself over Europe to any degree and a reversion to flat mild(er) zonality.

 

In this sense I think the ECM this morning is not reading the script...a prime example of best not taking operational output at face value. Better to try and read the trends suggested over a day or two (and more) rather than chop and change opinions based on 12 hour computer roll-out.

 

The London ensembles bear out this fact with the operational at the far top end of solutions by day 10 and on the basis that it is also at the top end by days 6 and 7 (where the disagreements over the block to the NE have started already from day 5) then we best take it indeed with a pinch of salt for what the rest of the output shows

 

http://www.weathercast.co.uk/meteo/eps/ensemble-tt6-london.gif

 

At the other end of the spectrum, a sunshine and snow showers easterly remains unlikely for the time being, but, with the cards hopefully falling right for the UK in terms of continued demise of the vortex, this becomes a much greater prospect of possibility as we head further through February. In the meantime, enjoy the first wintry flavoured salvo of the season this week and the day to day ride of model output whatever it appears to bring

Edited January 26, 2014 by Tamara תָּמָר

[IDO]

Nothing wrong with a difference in opinion for sure, as always there is method to why models will show a solution based on looking at the European picture in fine detail, though I am unconvinced that the low would simply sit over Scotland and not at least try to drain into the trough over the Mediterranean. 

The operational for the 06z was like Jason M suggested probably one of the worst solutions out of the suite with the ensembles going for something a lot cleaner (more the way I envisioned anyway)

 

 

Clear movement south east of that low as opposed to stalling over the UK.

Mean temperatures look good in the north, more knife edge in the south with 850s around -2ish. 

 

Long term there is big support for a strong block north of Alaska for the foreseeable future

 

That's a huge signal for that to be in place. 

ECM not as strong but there is a definite positive anomaly up there

 

If the Scandi high remains persistent as it has and with a strong block well forecast over the other side of the pole. Then there is a good chance of keeping the two lobes of the tropospheric vortex separate and hopefully weakening the Atlantic jet somewhat. 

 

 

Hi, yes some of the ens have the trigger slider low further west and this enables the upper trough to be accentuated allowing the second slider to move more south/SE:

 

op:   mean:  T180: 

 

However the mean by T180 are losing the darker blues digging into the upper trough as the flow goes over the top, and the surface low in the Med is static, suggesting it is not being fed and is more a cut off feature. Close to the op with slight timing issues.

 

That is why it is a knife's edge; the track of the first slider and the track of the potential second slider can make big differences to the medium term. Not much inter-model, inter-run or inter-ensemble clarity so all conjecture at the moment.

Edited January 26, 2014 by i'm dreaming of...

[Stuie]

Well comme ci comme ça, Some of the ENS are good with sliders evident, see the Control

 

On the other hand the longer term ECM ENS for Debilt are not so tasty

 

 

But a lot of 'Shannon ....' so at least the more immediate term looks of interest.

For a model that has been touted as below par (this forum) for a few runs, that isn`t as bad as it could of been. Any westward correction from the ECM today (at about T192) regarding the block holding then the scatter at the 0degC wouldn`t be so cohesive and more "Shannon" as you put it.

 

Edit:

ECM T192 / JMA T192

Edited January 26, 2014 by StuieW

[Stuie]

Interesting that the GFS has the jet stream really running out of steam and on a really southern route by T180. Hopefully take the wind out of the Atlantic sails for a while.

 

Edit:

JMA does favour this route also.

Edited January 26, 2014 by StuieW

[tight isobar]

Good day this feature maybe a devolp, of what most are wanting as is feasible at least, mean 144.and lots of talk AGAIN Midlands northward possible snow events of sort.however should such modeled become more of an evolution then such scenarios can be of the possible Midlands southwards pasting with perhaps disruptive elements. Again only one of many options available and further evolution and change likely occur between times, but well worth flagging. Back to here and forward there appears to be ample chance of a few surprises thrown into the mix going forward, with gradients and mixing flux of colder and slight ly milder air, and ye old famous battle ground, transitions ie rain to / snow to rain. But again sit back and watch for such possible +24/+48.winter appears to be saving itself for uk, and we appear to be now at of the traps. ?..lets keep running.

Good day this feature maybe a devolp, of what most are wanting as is feasible at least, mean 144.and lots of talk AGAIN Midlands northward possible snow events of sort.however should such modeled become more of an evolution then such scenarios can be of the possible Midlands southwards pasting with perhaps disruptive elements. Again only one of many options available and further evolution and change likely occur between times, but well worth flagging. Back to here and forward there appears to be ample chance of a few surprises thrown into the mix going forward, with gradients and mixing flux of colder and slight ly milder air, and ye old famous battle ground, transitions ie rain to / snow to rain. But again sit back and watch for such possible +24/+48.winter appears to be saving itself for uk, and we appear to be now at of the traps. ?..lets keep running.

[nick sussex]

The goal posts keep changing with new variables being thrown into an already complicated set up for the models.

 

The latest variable is what happens near Svalbard re another lobe of high pressure and how long a shortwave takes to clear se into Norway, because until that shortwave moves then you can't add more forcing on the upstream energy to disrupt and head se, you can see from last nights UKMO what happened without that new variable.

 

Historically once pressure rises near Svalbard and you get then the pressure rising over eastern Greenland you rarely end up  without energy heading se so I think that area is now looking key to the UKs cold and snow potential.

 

If you look at the GEFS you can see the clear correlation between the area around Svalbard and the colder solutions for the UK.and what happens with the first possible slider will then go on to effect the next.

 

Even though we're talking about the GFS 06hrs run and even the lowly NAVGEM given the pace of changes and the fact these have newer data, even allowing for their less than stellar reputation I would be surprised if the models and especially the ECM don't move in a different direction this evening.

Edited January 26, 2014 by nick sussex

[Cecil Hogmanay Melchett]

http://www.wetterzentrale.de/pics/Recm961.html

Thursday remains the best option for snow this week in my opinion.

Moreso the further north and east you go.

Before that im not sure the uppers are low enough for snow as opposed to wintry showers,

Obviously i hope the ECM is wrong with its evolution thereafter but the growing consensus seems to be an Atlantic breakthrough,whether its a damp squib or something more interesting remains to be seen...

[nick sussex]

We're now back to seeing a shortwave as the star performer in terms of its role in the current model drama!

 

 

The circled red is the shortwave, all the models have this, slightly differently modelled but you'll see that this runs  clockwise around the western periphery of the high to the east. The lobe of high pressure near Svalbard will be unable to really influence things till this shortwave has cleared se into Norway.

 

Once that shortwave has cleared the high will be able to edge sw and start to develop some pressure rises over eastern Greenland,of course timing is so important in weather but you need this cleared in good time before low pressure has moved too far east and lifted out the cold from the UK, if you get that WAA north this will slow down the low and help to keep the tilt of any troughing favourable towards the negative side or at worst neutral.

 

As an example of how that shortwave effects things for the UK the NAVGEM is a good synoptic example of how this helps to change the tilt of the troughing and helps to send more energy se'wards.

Edited January 26, 2014 by nick sussex

[Mucka]

Good afternoon all, just speed read my way through today's thread so apologies for repeating that which has already been said - which I surely will.

 

The more things change the more they stay the same...

I think that sums up both the inconsistency in the output and the continued uncertainty going forward today.

 

UKMO has flip flopped over the last 3 runs after being very consistent but the run most likely to verify was probably this mornings and that shows a continued battle between Atlantic and block which is finely balanced.

 

ECM Op is yet again one of the most progressive runs within its suite and it really would be nice for it to show something more representative of its mean output this evening.

It both bothers me and worries that the highest res run has continually been pushing for an Atlantic win but I am encouraged that it at odds with its own ensembles and other output so currently very low confidence in ECM output. 

 

GEM Shows the block hanging on and eventually dominating by day 10 so the opposite extreme of the ECM. The trouble with  extremists is they never really want to find a balanced solution, don't you find?

 

GFS Wants to bring a brief wintry spell before pushing the Atlantic through although it should be noted its ensembles are not so bullish and the 06z set is the chilliest for a few runs.

 

Ensembles

 

GFS 06z/ ECM 00z (Central England)

 

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=256&y=93

 

 

I'm still firmly on the fence (A very sensible if uncomfortable place to be given current conflicting signals and you can always see both sides from up here)

A forecast that covers all bases for next week would be; Colder with rain pushing in from the West and the prospect of some wintriness at times, especially further North and East. Thereafter temperatures should remain below average for most through the weekend with the possibility of unsettled, less cold weather pushing in the following week.

 

In my personal view the model output is most progressive on Sundays but I have absolutely nothing to back that up. 

Hopefully though I will have some circumstantial evidence by tomorrow evening with the block proving more robust in the output than today.

Of course they may also show the Atlantic rushing through in which case we never had this discussion and this message will self destruct.

Edited January 26, 2014 by Mucka

[IDO]

Although the GEM 0z op is a corker it has little support if the mean is a guide.

 

OP at T180:   MEAN: 

 

The mean is close to the GFS 06z mean: 

 

The Arctic High has been modelled by GFS the last few days to migrate to join the Russian high:

 

Some ens go SW towards Greenland. The GEM op also goes towards the Russian High but luck strikes with wedges of HP that prevents the (ex) Arctic High sinking and a Scandi block forms. That looks a bit tricky...

 

 ...and bearing in mind the mean?

 

ECM mean also strong that the Arctic High sinks SE into Russia. Looks the call.

[Nick L]

Ian Fs tweet answers that, poss 2cm + in Wiltshire tonight...

 

Please keep posts like this in relevant threads. Thanks.

[Long haul to mild]

 GEM Shows the block hanging on and eventually dominating by day 10 so the opposite extreme of the ECM. The trouble with  extremists is they never really want to find a balanced solution, don't you find? 

Yes, finding it hard to trust the GEM. From what I recall it hung on to the idea of a significant Easterly for this week just gone when all the other models had dropped the idea. Eventually it flipped overnight to join the others. I expect it to do so again soon re the current setup, although I have to say that the block should not be underestimated!

[phil nw.]

Please keep posts like this in relevant threads. Thanks.

Yes on this point a number of posts containing more general chat and or comments unrelated to model discussion have been moved over to the other model thread here-

http://forum.netweather.tv/topic/78680-model-banter-moans-and-ramps-winter-201314/?view=getnewpost

 

Before the evening discussions just a request for everyone to please only post about the model runs in this thread.

 

General chat including tweets,BBC weather forecasts etc should go elsewhere,either the Winter thread or the Moans/Ramps thread.

It's your views of the charts that should go in here not from other agencies.

 

Thanks everyone.

[bryan629]

Just for newbies, a couple of images below that demonstrate how a scandi block behaves. notice the front that passed over us earlier today has run into the block and stalled over the north sea, if the block would have been a few hundred miles west, we would have been seeing a major snow event , because the front would have stalled over the uk. hope this give you a better understanding why we all on here want to see the block move west

these images are an hour in lapse

 

[Paul]

12z's rolling out now, so thought this would be a good time to remind everyone that we need your help to keep the atmosphere on this thread friendly.

 

Trolls!!

We know that occasionally some people post on here (and other forums) with the intention of causing hassle and controversy - eg trolling. When this happens we act, and we'll be able to act even more quickly if people hit the report button when they see a post that they believe to be an issue rather than responding to it. 

 

Troll Hunters

Beyond that though, what also causes problems is some people believing every person who isn't jumping from the rafters to talk about cold weather is some sort of troll, determined to wind them up and ruin their chances of cold weather by daring to mention milder weather is possible! This type of thing is something we deal with every day (far more regularly than we need to deal with blatant trolling), it really can affect the discussion and isn't acceptable.

 

Mildies vs coldies - no,no,no!

If you're the sort to jump in all guns blazing at times, please just take a moment before reacting to someone - re-read the post, consider their view and if you want to disagree do it in the context of a discussion about the models rather than a point scoring frenzy of mildies vs coldies - it really doesn't have to be that way...

[chionomaniac]

The runs start with the GFS with a slightly stronger Scandi block by T+72.

[shaky]

The runs start with the GFS with a slightly stronger Scandi block by T+72.

hopefully which is something we can build on come 144 hours!!fingers crossed!

[Ian Suffolk]

The low at T72 is a little more flabby on the GFS but we still get that easterly feed. If only those uppers were lower!

Let's hope the Scandinavia high can hold this time....

Edited January 26, 2014 by Ian Suffolk

[DeKust BergenaanZee]

Well, as I had hoped and expected, the models seem pretty much in agreement that the winter will make a come back in the second half of the coming week.  Unfortunately, it looks like a short visit, with moderating influences again gaining the upperhand next weekend. Then we are in early February, which statistically has probability of somewhat higher average temperatures (February thaw). So IMHO nothing substantial in terms of a stable winter pattern to expect before middle of February. 

[Long haul to mild]

UKMO on its way out, still looking cold at T96 in an Easterly flow