Model Output Discussion 1st January 2014-06z onwards.

[nick sussex]

Reading through the upstream discussions the pattern suggested normally is below average for the UK, with high centred further west in the Atlantic and lower height anomalies to the south and sw, with high to the ne its condusive to troughing disrupting near the UK.

 

I think the issue is what side of that troughing the UK will fall? if you're a coldie you'd like the eastern side of that to help pull some cold se easterly flows into the mix and possibly see some frontal snow.

 

Thereafter its really what happens to the invigorated jet, if it splits west of the UK cold stays if it just barrels over the top then milder.

[bluearmy]

ext ecm ensembles at day 14, indicate strong signal for troughing to our NW, with the Scandi block no longer locked, .. This is is trend moving frwd. So, a scandi block, the preferred route, but temporary, before a reinvigorated jet brings the Atlantic backas for the 12z runs, the ecm & jma promote the idea of blocking to our ne, which creates a battle ground over the uk, between an easterly for a time, and Atlantic fronts trying to push in from west.gfs indicates a strong jet into second week, makes much less of the blocking, with any heights shunted.so, Imo, its turning less zonal, temporary blocking, before we return to a more mobile pattern, with the Atlantic once more in control. Gefs reinforces this idea into wk 2, with naefs keeping us unsettled, with little sign of blocking.11-15 day heights naefs

 

bit naughty draztik - the naefs has, in the 6/10 day area, taken a big step towards ecm ens recent output re the anomolys.  the mean slp are useless at this range as i have stated before.  post day 10 and the ecm ens again revert slowly to a more mobile flow as the re invigorated jet makes it back just to our east again with the blocking retreating. given that the period 8/12 days has drifted toward a slightly slower evolution to atlantic domination, i would be waiting for another couple of runs before being sure about the return of the jet through the uk by the end of week 2. 

 

there can be no argument that recent extended ens runs have shown a stronger jet powering back across the atlantic at the uk with no split evident. would temper that with the fact that low heights continue to be shown over europe. that makes a straightforward return of the atlantic a tad less clearcut as it will draw the jet se. 

 

and interestingly, the gem ens mean at T240 is a virtual carbon copy of the ecm for long wave pattern. it then goes on to develop the mobility discussed above though again with lowish euro heights persisting.

Edited January 6, 2014 by bluearmy

[snowice]

For the first time in ages, GFS 12z is showing a very similar set up to ECM at the crucial 144hr timeframe (always the absolute far reach of reliable timeframes). Both are supporting height development to the north of Scandinavia. Unusually UKMO is showing a different pattern, however, it has been very similar to ECM in recent days and was very keen on a strong build of heights to the north of Scandinavia too.

 

Will be interesting to see whether UKMO has the right evolution..

 

It is a very complex set up - always is when a split flow has chance of developing.

 

More importantly we look like finally seeing a weaker jet which in turn means much less in the way of wind even if it looks like staying preety unsettled. Also for the first time all winter some proper cold uppers look like developing to our NE - and unlike early winter cold pools to our NE become much harder to shift as we enter the second part of winter.

 

The synoptical evolution shown at the 144hr range by ECM is uncanningly similar to this exact time last year in terms of rising pressure to our NE blocking off what had also been a very rampant atlantic - however, things are different in many other respects, last year the PV was nowhere near as cold and we didn't have such a strong thermal temp gradient in the mid atlantic, we had also seen much colder uppers surface to our NE, unlike this time last year, we have many more factors not favouring a cold spell, but doesn't mean we can't get one.

Excellent post and lets hope your right!

[tight isobar]

Reading through the upstream discussions the pattern suggested normally is below average for the UK, with high centred further west in the Atlantic and lower height anomalies to the south and sw, with high to the ne its condusive to troughing disrupting near the UK. I think the issue is what side of that troughing the UK will fall? if you're a coldie you'd like the eastern side of that to help pull some cold se easterly flows into the mix and possibly see some frontal snow. Thereafter its really what happens to the invigorated jet, if it splits west of the UK cold stays if it just barrels over the top then milder.

yes nick its that close,,50/50,

[snowice]

^{18Z will have a lot of interest tonight, will it go towards the ecm again?}

[nick sussex]

yes nick its that close,,50/50,

I think you can see why its a bit of a nightmare to forecast too far ahead, if the high gets sufficiently north before the increased jet and you have lower heights to the south then you'd edge to cold, that's a way ahead, for coldies the key thing is to get as much dig  south of the jet to the west and more energy into Iberia.

[Earth Wind and Snow]

yes nick its that close,,50/50,

as alluded to by Ian Ferguson earlier - the UK Met do not know which way this is going to go so everything is up for grabs. Funnily enough it was about this time last year that Ian used the famous phrase Shannon Entropy when models were similarly undecided. Lets hope we get a repeat of what followed from late Jan through to March in 2014. The mobile regime last year was not as severe as now in relation to storms etc. however that does not mean that if a cold spell is to follow that this cannot also be more severe than what happened last year

 

More twists and turns to come over the next number of days methinks

 

EWS

[SMU]

hi Steve

about another post not this one

 

Re this comment Steve

 

Sorry to be a pedant on your posts Draztik - your analysis of the 00z Ensemble mean - returning to zonal seems quite suspect as you *may* be interpreting the GPDM intervals as the prevailing wind direction, when actually there not.

 

 

The lines are showing you the depth of height anomaly -  whilst you could intimate that westerly conditions maybe pushing through, you could also say that the UK could be under a battle ground scenario with the polar front straddling the UK, or even that the high pressure in the atlantic was ridging NE to reinforce the cold anomaly over us & Europe- its not always right to put the first assumption in as your punt as to whats happening.

 

In dark=not true they are the height lines at 500mb shown in geopotential metres, with the standard heights shown on each alternate line (no idea why there is an intermediate line between each). That is if it is the black lines you are referring to with the numbers attached? Thus we see familiar numbers such as 528, 546, 564 etc. The coloured areas are the +ve or –ve height anomalies with the colour code at the bottom of the chart?

 

Or am I misunderstanding what your post was driving at?

 

Hi John I missed a bit out- it was supposed to read -

 

The lines are showing the height in GPDM & the height anomalies- as well

 

God knows how that translated to that gibberish sentence-

 

I was pointing out that they may be construed as windflow lines....

 

S

[london-snow]

Why or why do folks keep looking for cold there is not any real cold in the near future  

Isn't you're post just going to add more fuel to the fire I.e mild campers v cold campers?

I would have thought being a mod you would want a easy life lol..

Anyway to answer your question. Truth is that there is no cold and snowy days coming up anytime soon. However we are first and foremost beginning to see a pattern change and the most interesting thing about that is quite simply no one can be certain which way we are heading. There is potential for things to turn colder from the east or north east as per the hype atm but at the same time nothing at all is a given and we can end up again being dominated by tiresome lp systems. I'll leave you all on this note ' If ian F and the meto don't have a rough idea then where does that leave us '?

That's why in heart we come back year after year. . Thrill of the chase!

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2014010618/gfsnh-0-84.png?18

 

GFS at 84 sees a chunky correction west as it sharpens up the east coast system-

 

Can we get the GFS over the line tonight at 168....

 

S

[Duane S.]

I'd say this highlights the uncertainty of the Mid-month period very graphically...

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2014010618/gfsnh-0-114.png?18

 

2 shallow systems in the atlantic-  very unlikely.... one main one in the gap is where we should have been-

 

never the less it may make a run for it in the mid term!

 

S

[Cloud 10]

I'd say this highlights the uncertainty of the Mid-month period very graphically...

prmslReyjavic.png

 

Looks like the 920mb low was a slight outlier. 

[nick sussex]

Well at last a bit of consistency between runs, not a bad GFS so far, it would look much better with a more negative tilt to the troughing earlier. The question is what will the UKMO do with their fax charts because at the moment their raw output is looking very flat and isolated at T120hrs.

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2014010618/gfsnh-0-168.png?18

 

Houston GFS has lift off.

 

S

[Cloud 10]

Well at last a bit of consistency between runs, not a bad GFS so far, it would look much better with a more negative tilt to the troughing earlier. The question is what will the UKMO do with their fax charts because at the moment their raw output is looking very flat and isolated at T120hrs.

 

Just noticed the UKMO on Meteociel has had the UK only view upgrade as well. 

 

Meteociel - Modèle UKMO pour la France, résolution 1.25 degré

[nick sussex]

This is really turning into a thriller! yes I should get out more! You can make a case for so many different scenarios, its one of those situations where the boundary might be right over the UK and the models will chop and change the snow line between outputs, the whole lot could then slide away to the se with the ridge back over the top and bingo, or the pattern is too far east and the North Sea fish get frozen!

 

I'd say for each little westwards correction you can add a bit more percent onto cold, conversely it could go the other way.

[Ice Day]

Cold really building to our east at 174.  Just a couple of hundred miles then bingo!

 

[shaky]

This is amazing could we actually be looking at our first cold snowy spell of the winter!!its just too hard to believe at the moment!!I just know something is gona ruin it.

[Ice Day]

Not sure, but are we finally looking at an undercutting low?

 

[Radiating Dendrite]

Finally an undercut.......get the car started!

[snowice]

This is amazing could we actually be looking at our first cold snowy spell of the winter!!its just too hard to believe at the moment!!I just know something is gona ruin it.

This could be the turn around we were waiting for?Tommorows runs will be interesting!

[Nick F]

Well, I have consumed enough runs and ENS now to see that the signal is growing for blocking to the NE by days 8-10,  with the UK, as often the case, looking to be the battleground between east and west.

 

You can quite clearly see the Atlantic lows struggling to get past the meridian on the 18z GFS once the ridge builds north over N Sea/Wern Scandi next weekend. The only place that energy can go then, is under the block across continental Europe.

 

Interesting times ahead, but finely in the balance at 50:50 IMO.

[Dibdabbers]

Finally something to get excited about! Whoop whoop

[tight isobar]

Far better from the 18z GFS, if in term of potential. Further runs cross" should hopefully start firming v, soon. ? And dare isay evenupgrade dedevelopment.