[Model Output Discussion; into 2015]

First with the bad news as ever IDO!

Luckily history shows a SSW isn't always required for a cold spell.

Also it is a long term forecast and we know how reliable they are - it certainly does not put anything to bed.

[Model Output Discussion; into 2015]

I am aware that I am doubting ECM again (was chastised for doing it this morning)  but a 1055hpa High over Alaska is quite rare, I thought 1050hpa were uncommon (more common in Siberia):

 

ECH1-240 (4).gif

 

So I would be very wary of taking that seriously and looking at the height bias for D7 for the Alaskan Region you can see that even at that early stage it has massively over done heights on the last 5 12z runs:

 

NOAA_NWS_NCEP_WPC_MODEL_DIAGNOSTIC_-_INTERACTIVE_MODEL_BIAS_PAGE 7.png Mean: EDH1-240 (2).gif

 

Just something to take into account.

They cannot be that uncommon - the NH chart I posted for Jan 18th 2013 had one of 1050 hPa and in fact this grew to 1060 hPa by Jan 20th.

 

 

Point taken about ECM overdoing heights in the later charts though.

[Model Output Discussion; into 2015]

The ECM is exactly what I was alluding to earlier.

 

http://www.wetterzentrale.de/pics/Recm2401.gif

 

With the jet running SE a relatively weak area of HP is enough to potentially bring cold, snow. I shall have to check the archives later but im sure it was the winter of 2012/13 that often bought the snowfalls.

HI TEITS,

 

Yes you are correct  - there were several undercutting scenarios producing significant snowfall without a big block e.g. 9th Jan 1020 mB

 

 

and even more notably 23rd Jan 1015 mB

 

 

The latter produced about 1 foot of snow here in Northampton.

 

Interestingly the NH pattern shows a big Alaskan ridge along with the PV over NE Canada as is expected in the next few couple of weeks  this year. Back then I remember a lot of discussion about whether these 'blocks' would resist  the rampant PV and promote trough disruption  - the naysayers were wrong again.

Not saying this will happen again this year but is always a possibility which we should look out for to show up on the Ops and individual ensemble members (will not show on means)

[The Midlands - Weather Chat]

Amazing temperature changes here in Northampton. At 18:00 it was 0.9 C and snowing. Temperature gradually rose to 6.7 C at 10:30 with a DP of 6 C - felt quite balmy. Both temp and DP dropped 2 deg in 1/2 hr and now temp down to 0.9 C again. A 12 degree change on 6 hrs.

[The Midlands - Weather Chat]

After some snow earlier temp up to 5C  but expecting that to drop as the depression moves SE.

 

You can see where it is on XC weather

 

http://beta.xcweather.co.uk/GB/observations 

 

heavy snow to the North - rain to the South. Problem is the precipitation is usually heavier when the low pushes into the cold air and becomes lighter as it moves away. We shall see.

[Model Output Discussion - The final stretch to Christmas]

"I'm here to chew bubblegum and kick ass and I'm all out of bubblegum.  (Not aimed at you or MetO Fergie)

 

RE weather warnings. Likely a directive from government?

All part of the dumbing down of society and to reinforce the idea that we are helpless without "officialdom" 

The ones directed to health workers etc are absolutely fine and in context but the ones directed at the public these days are typical nanny state ramblings.

Of course being a member of the public I get to have an opinion on that regardless of how officialdom tell me how I should feel. 

 

 

What I find odd is that any potential cold snowy weather being modelled seems to be very much downplayed until it is actually certain it will arrive at which point we seem to go to the other extreme. There doesn't seem to be any middle ground. Well that's my opinion and you know what they say about opinions...

 

London ECM ensembles very much behind a warm up but where did the control run go?

I assume that found some undercut or perhaps it maintained high pressure over the UK? Anyone know?

 

 

That is not the control run it is the GFS 00Z Op.

[Model Output Discussion - The final stretch to Christmas]

FYI, GEFS goes up to 2hPa.

http://www.wmo.int/pages/prog/arep/wwrp/new/documents/GEFS_status_plan.pdf

 

Will soon be 0.2hPa in the next update planned in 2015 !

Thanks Sylvain,

 

Some significant improvements planned or early next year - especially the horizontal resolution. Not sure taking it out to 720 hrs as planned 2018 is a good idea - we will be discussing forever on here.

[Model Output Discussion - The final stretch to Christmas]

Hello, what does it give us to hold onto?

The pattern has not been flattened so much with HP still close by

 

 

Leading to some cold frosty weather (at least in England and Wales)

 

And therefore the potential that it could develop into something more interesting later.

[Model Output Discussion - The final stretch to Christmas]

The end of the high res GFS Op looks pretty weird to me  - nothing seems to be happening - just a few small lows dotted about in the large PV

 

 

 

Maybe the weather is in on its hols as well

 

Edit

 

Soon fires up in the low res though

[Model Output Discussion - The final stretch to Christmas]

Much as there is an overall improvement at 192 on the GFS (Op, P and Control) there is not much support in the ensemble.

OP

 

P

 

Control

 

Ensemble mean

 

and spread - op and control outliers

 

[Model Output Discussion - The Run In To Christmas]

No it doesn't. It shows a rain deluge followed by some wet back edge snow. Away from hills you will be better served with a brolley than a sledge

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=156&mode=2&runpara=1

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=162&mode=2&runpara=1

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=168&mode=2&runpara=1

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=156&code=0&mode=2&runpara=1

 

Would certainly be windy

and feeling cold

 

l

It shows heavy snow sweeping the country between 156 and 174hrs with blizzard conditions, bank

Bust as Jason says no real snow - this is maximum extent of lying snow - 50 cm in  the highlands but best for England is possibly a cm of probably wet slush.

ECM would bring in some proper cold which could lead to some decent snow at a later date. Problem is these 240 hrs charts are not verifying but I would still rather take this chance.

ECM still a mild outlier (along with the control)

[Model Output Discussion 1200 hrs 15/11/14]

Here we go on the 06z, with changes in the phasing of the lower heights to the NW and the Azores HP wedge to the SW, which negates the troughing to the SE into the  Med. So by D9 we get the repeat of the undercut drama for this week already downplayed as the ridge blocks the LP cutting SE:

 

Op gfs-0-186-2.png  Parallel gfs-0-186-3.png

 

So at D11 the UK just the last stop on the Atlantic conveyor belt as LP stalls against the block, and is then driven N/NE over the Sceuro ridge:

 

gfs-0-264-3.png  Brute force from the Atlantic the block gets slowly pushed back east:

 

D12 gfs-0-288-7.png  D13 gfs-0-312-5.png

 

The Parallel has more disruption than the op and continues its theme from this morning with low heights disrupting over the UK with the block to the east, but this time more energy going over the block so no retrogression, and back to square one by D14:

 

D10 gfs-0-240-27.png  D12: gfs-0-312-6.png

 

This scenario looks so much more likely, with that more organised PV, than a disrupting trough undercutting the Sceuro block. At D16 we remain in a similar pattern. We saw from last year once the pattern gets locked down it can kills weeks of the Winter. Not that this block is too bad as long as it remains a Sceuro high rather than just a mega Russian one, and we do eventually get the sliding Atlantic scenario.

 

As for this morning's GEM, it looked like one of it's regular outliers and the Mean at D10 confirms that: gens-21-1-240-35.png

 

And as for pinning hopes on the current strat warming, the recent posts in the relevant thread are giving caution to those expectations, so in reality we need the trop to start moving in a colder direction otherwise real cold will remain out of reach.

Not sure why you are saying the GEM is an outlier to its mean. The Op shows a main low situated just SW of Greenland with a trough to Portugal, a Euro/Russian high with a ridge to S Scandi.

Seems quite consistent with the mean to me with the same general pattern being shown.

[Spanish plume anyone? Storm and convective discussion 17th July Onwards]

Sadly we've witnessed the death of your once great storm!!

It just about made it to S Northampton before dying - we had lots of thunder then torrential rain with hail. Looks like the cause was the overhang from the French storms getting this far N.

http://www.sat24.com/include/images/trans.png 

[Spanish plume anyone? Storm and convective discussion 17th July Onwards]

yup ..  looks like something is kicking off in that area

http://www.blitzortung.org/Webpages/index.php?lang=en&page_0=12

Yep - lots of flashes to the South near MK - should be here shortly

[Model Output Discussion 19th January 2014-18z onwards.]

The op run from the 0z was in a synoptic cluster of 20%: Screenshot_20_01_2014_16_51.png

 

The 12z op is much closer to the main clusterings of the 0z.

Doesn't mean that it is 'right' though - fortunately the weather does not run by averages

[Model Output Discussion - 10th Jan Onwards]

incidentally, the ecm extended keep the arctic high but it is kept on its axis towards nw russia (see cloud's post above) as the vortex spits out more venom in our direction, again traversing the dumbelling atlantic ridge and dropping into europe. no appetite for any s greenland blocking beyond the day 10 weak upper ridge.  the control builds a huge block from the eastern seaboard across to russia with a strong s euro trough. we end up with the vortex energy having nowhere to go but the pole which sort of sets it apart from the ens mean !

I think this illustrates two of the main otions open with the arctic high (if it appears) - it can link up with the Scandi high and then we have a chance of a major cold outbreak. This is illustrated by P1 although we do not quite the cold yet.

The other option is that it links with the azores high through a mid atlantic ridge as shown on the ops.

As NS and SM alluded to the first option is much better in terms of a real cold outbreak. With the second option because the PV is still located in NW Canada it is only a matter of time before it breaks down the ridge and we are back into more of the same mush. In addtion as NS suggested we have the worry that there is not quite enough amplification and the ridge is not enough to stop the low in NE US from phasing with the low over us - the result is no cold at all. The only route there to a major cold outbreak is if the mid atlantic ridge links up with the NW Russia high pressure through the latter ridging west  - e.g. P7

 

So for me I would much prefer the 1st option. The main worry with this would be that it sets up to far East and the cold does not reach us or the Scandi high parks its bottom in the E Med.

 

So lots of interest to see how it all pans out but I know what I am rooting for.

 

Edit - of course anything is better than what we have just seen from the18Z

[Model Output Discussion - 10th Jan Onwards]

The ensemble mean has changed quite a bit a might be expected (especially for the 850s). However the debilt ensembles still showing some cold runs so still some possibilities although the METO 10% is probably about right.

 

 

The mean at 240 still shows to my untrained eye a split jet to the WEST of the Uk  - perhaps someone more expert could clarify. It also shows the PV moving menacingly towards Greenland

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

big problem is steve is that tiny area of high pressure is really not enough to keep things going this is why the 30dayer ukmo Is so reluctant to give us the real deal. im afraid longevity will be the issue although granted it is the gfs.

 

im going to see what the others come up with it looks far more messy with the only a little weak surface ridge to our north its in the right place but not potent enough that's my thoughts anyway I hope im wrong and it changes for the better.

If you must worry about how long something will last which has not even happened you should read the guide for forecasters on Scandi highs posted by JH yesterday. It clearly states that the longevity of the block does not depend on its size. Quote 'The intensity of the anticyclone on the day of formation has no effect on persistence'. The main factor is the  mobility to the East of the block. There are then someguidlines as to what factors affect the persotence of this set-up. I reattached it in case you did not see it yesterday.

Empirical rules for scandinavian high to developc.doc

 

This was also borne out last January when we had a small block with central pressure of only about 1015 mb which proved quite resilient. 

 

http://www.meteociel.fr/modeles/archives/archives.php?day=17&month=1&hour=0&year=2013&map=0&mode=2

 

It is the orientation and placement of the block which is most important in my view.

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

As a lurker here for several years and only occasionally posting - can I say a 'big thanks' to posters Ian, Snowballz, Gibby and Nick for their informative and welcome input into this forum. It has certainly become a really authoritive voice. Long may it continue!

Don't forget Steve Murr

[Model Output Discussion 17th Dec.2013-12z onwards.]

GFS 06z is completely different to the 00z. But also vastly different to the ECM, UKMO and GEM which all in turn differ from each other at 5/6 days out.

Need a lie down 

Yes it seems GFS is having nothing to do with the inland track of the US low and the consequent sharp mid atlantic ridge which leads to the weak Scandi ridge on the ECM. However it does seem to be favouring more robust buildng of heights to the NE in general.

 

However it seems unlikley that this pattern could give us anything very interesting from a cold perspective in the medium term as it allows the reforming vortex to take up residence close to NW UK. Maybe some cold zonality due to its close proximity which I think was what the Meto were alluding to in the 15-30d upate yesterday regarding more wintry conditions - especially for the North..

I think I know which option I would prefer but the odds seem stacked against this. Were it to happen though (and it obviously possible) there would some very incorrect forecasts knocking about at present.

[Model Output Discussion 17th Dec.2013-12z onwards.]

Colder rain..

Wrong

[Model Output Discussion 17th Dec.2013-12z onwards.]

GEFS has some WAA amongst them, some into Greenland, and some up in Scandy at t300Maybe a change to the EC32 tonight will sched some light on a poss change...Perturbation 6 please...

 

 

 

I prefer 7 and 8 myself

[Model Output Discussion 17th Dec.2013-12z onwards.]

Fair enough, William...But individual perturbations start from incorrect data?

Modified data I think is the phrase but indicates possibilities only and of course the averages are used to give the most likely solution at this range rather than the ops (as JH keeps telling us)

[Model Output Discussion 17th Dec.2013-12z onwards.]

Yes those heights were promising, Russian, N. Pacific and polar heights: gfsnh-0-288.png

 

But there was an inevitability about it. So much PV energy, you squeeze one part of the NH it will power up the lower heights elsewhere and flatten the pattern: 

 

gfsnh-0-384.png

 

In this instance the Pacific ridge is quelled by the energy in the form of lows, spinning off the bottled up NE quadrant of the NH. Thus the jet is re-invigorated and off we go again, repeat and rinse pattern. What IB warned us of.

 

Till the PV loses some of its bite, any transitional HLB is going to be of little help unless we lose the Greenland blob, seemingly the only part of the PV that is omnipresent, meaning any cold flown in on the jet from the Canadian vortex is washed out time it finishes its N. Atlantic crossing to the UK.

Pertubation 2 is interesting and demonstrating the sort a thing we are looking for( or hopecasting for depending on your pov)

 

I see Mucka beat me to it.

[Model Output Discussion 4th Dec.2013-12z onwards.]

Hope this does not come off for Christmas day!