Winter Model Output Discussion 01/02/2013 12z onwards

[winterof79]

00z?

They are 12z

[snowking]

http://www.knmi.nl/e...agse/index.html

A cracking set of ECM ENS underpinning the operational.- expect the MEAN at day 10 to be very good.

S

Just a slight word of warning here, the De Bilt (as suggested a few posts ago) do look very good indeed in the mid-term - the London ensembles will follow in a similar fashion in the 192-300 period....however expect a slightly milder set of graphed ensembles post 300 when the London ones arrive, with a temperature range across the UK still sub 3c across Scotland, but further south mean temps broadly 3-6c (this is the likely range of the mean for London) and as high as 9c in the far SW.

Plenty of time for all that to change, but just a word of warning so that we don't have any nasty surprises later on from the London ens

SK

[Jason T]

Evening All-

Steve Murr

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Posted 3 minutes ago

Evening All-

Sometimes its difficult to pick out what to write in amoungst the rest of the daily musings. Especially when you are trying to make a post a little exciting to read -

Today feels like deja vous. infact De ja vous on De ja vous perhaps....-

It feels like we have been chasing the cold from the east from this last winter, all across december with limited success, then this past January with moderate fortune & here on the doorstep of Feb, the final furlong of Winter when peoples opinions still have enough sway to change their perception of Winter we are chasing it again!

My Honest Commentary around this Winter so far- is that its not gone how some planned. The feeling we all got around November is that the snow advancement & the Ice melt + the Easterly QBO & neutral ENSO Supported the kind of pattern that had the cold setting in early-

However the stratosphere temp nose dived into negative anomalies late Nov - early december & once that percolated downwards through to the troposhere ( which took time - to mute out the positive signals ) we have seen mediocre synoptics since Dec 1, especially at the higher lattitudes-

Infact across the polar field & down through Greenland there has been no blocking, directly adjacent to the quasi stationary vortex that has parked itself in canada this winter.

My feelings around the stratosphere is the actual thread has ticked along well, with level headed measured posts, however with such a lead time between initial model conception & it landing - the expectation spiralled out of control. & now the expectation has cluster bombed all over the shop as people struggle to understand the propergation waves & the fallout from the warming.

The warming in Jan looked Epic on the charts- as we saw the temps go off the scale @ 10 HPA, however the tropospheric response was less flattering, with what I would call 'mild' anomalies developing over the polar field. Again I think what has caught some out that use analogue forecasting via the stratosphere was the overwhelming historic data support pointing to 'significant' blocking to the North across the polar field with a strong teleconnection modality change fom most positive to negative indexes.

In terms of height anomalies being 'mild' from a AO point of view this was also reflective with a mild -2 index across the piste.- What was great for the bulk of the UK was the fact that the polar front straddled the UK at angle where low pressures bumped along the cold air, however werent deep enough to disturb it & mix it out - so snow on snow on snow events occured & for some its was fantastic.- so great stuff.

We need to learn for next year & remember that with all the research thats presented, all the fancy presentation by some- the sample of data we have is not substantial enough to make a definitive forecast, just a rationialised one with probabilities.- which for the very reason just highlighted has a distinct chance of going wrong.

Anyway onto the here & now,I think we reach a crossroads tonight, where we take have 2 distinct outcomes, one where we possibly see the back of winter 2013 - which would certainly make it less memorable & taint peoples views towards the winter as a whole not being that great- or we go off on an opposite tangent where the cold attacks again, - in the bigger picture the hemispheric pattern looks mediocre with our regular 'cold' winter features notably absent- so we are going to rely on unusual patterns that are very specific to the UK to deliver the 'white' goods.

If people havent learnt this year- the GFS is useless. its useless because it has an eastward bias with the atlantic jet energy & for the fact that its model accuracy over to the NE - up by Norway / Svalbard etc is pretty wayward.

When you have these 2 weaknesses in tandem fighting against a retrogressive pattern then you will always see GFS runs flattening the pattern & overunning energy before slowly as more & more runs land & the timeline shortens from 200 to the 160's/170's a high pressure is resurected from the dead like a drawbridge over a mote- up she goes as it were with a higher amplitude each run. ( excluding the totally awful 06z GFS)

The ECM has nailed the wedge pattern. A few of us regulars have commented on this developing, however perhaps its been overlooked because the ever popular GFS doesnt 'see it' & also because people were to busy hoping for Greenland heights to develop at short notice.

This is your wedge, it comes from a highly amplifed jet which is split- heres the ECM chart-

http://www.meteociel...H1-192.GIF?01-0

Expect this to come into UKMO range soon-

Its still a slow burning pattern- why? because there is no evidence of a jet over Iberia moving North which is the signal for 'squeezing' low pressure north into a scandi block,.

As a result the flow from the east looks to be gentle with an ever increasing depth to the cold.

The big question is where the dividing line sits at day 8/9/10- this will be the make or break element for this Winter. If its out in the north sea then a lot of cold rain for the UK & a miserable forum, however we are edging west with time & the form horse is somewhere straddled again across the UK. possibly down the spine, with the East, SE, NE & scotland in prime locations for slider snow events, & the west more at risk of something less wintry..

If you note there is a steep gradient across a short distance - here demonstrated at the ECM france 240 chart-

http://www.meteociel...F0-240.GIF?01-0

-13c to the East, -6 over cornwall with -4/-5 over Ireland. - Presuming the jet continues to slide at a similar angle somewhere along the battle ground could get a lot of snow- so its a early watch out!

Over the next 24/48 hours look for consolidation of the ECM height profiles & the trough digging south - & watch the GFS resurect that high further & further North.

hope you enjoyed reading.

S

Jason T, on 01 February 2013 - 21:05 , said:

Posted 14 January 2013 - 18:49

Glacier Point, on 14 January 2013 - 18:41 , said:

and 12z day 10 with 06z for comparison:

06zGFSEnsembles500mbHeightAnomalyNH240.JPG 12zgfsensembles500mbHeightAnomalyNH240.JPG

and the GEFS temperature anomaly for that time

12zgfsensembles850mbTAnomalyNH240.JPG

This I think is a reasonable projection based on the global wind oscillation going through phase 4/5 type evolution. The key point that heights remain strongly below average across Europe. That supports +ve height anomalies to the north and prevents any widespread ingression of the Atlantic.

So low pressure signal in the Atlantic, agree with that. Atlantic powering through across NW Europe on a positively tilted jet - disagree with that, but with the caveat of a less cold spell 20th - 25th Jan is very likely based on the waxing and waning of the downelling stratospheric warming impacts.

Posted 21 January 2013 - 20:30

THE EYE IN THE SKY, on 21 January 2013 - 20:04 , said:

I know GP said early Feb and that we might even see a cold spell develop as early as the 28th Jan. However at this stage this is looking incredibly unlikely especially starting at the 28th Jan. At the moment a long fetch of SW,lys is looking the likely outlook for the end of Jan.

GP also said.......

Glacier Point, on 20 January 2013 - 22:22 , said:

So teleconnectively we have a reasoned case for anomalous heights to our north end January into February. The timing of this highly problematic as the models were to a degree blind-sided by the first downwelling wave, only latching onto it 2 days before the warming took place. Were this happen again, a sudden turnaround in modelling could well occur

So are we on the brink of a sudden turnaround. I think it would be foolish to take every timed output as sacred, Obviously we cant see what happens behind closed doors so to speak. Options well, I guess well and truly open. It is a case i believe from output happening today across the board all will be told very shortly, Once the correct signals are finely tuned. A poor Winter, Well i think i would rather wait till the end to compile statistics.

we are only on the brink of a turn around if you follow the GFS...

I guess we will have to wait and see Steve. Its not a challenge, Just believe not all is available to the naked eye.

[Panayiotis]

Difference between the 12z and 00z ECM ensembles are great if colder weather is what you're after! Look at the mean drop after next week!

Edited February 1, 2013 by Panayiotis

[Frosty.]

Dig out Dec 30th 1983 to Jan 6th 1984 and you get exactly the same setup.

Is it just me or is the GFS underplaying the amount of snow potential NE coast of scotland will get?

Done

[Tom Montalbano]

"Further to that superb post from Roger, I have dug out those Feb 1969 archive charts, they really are impressive and ended up with a stonking Easterly after the Northerly but the very cold spell ebbed and flowed, there were a few milder/less cold intervals as the pattern reloaded, yes the displaced azores high was a pain even then."

Sorry Frosty, you were quicker than me!

Cheers,

Tom.

[bluearmy]

the 12z naefs is an improvement on the 00z run as the 12z gefs were decent in week 2, pulling the trough west. the 00z gem ens didnt look so great so perhaps the signal is muted and if the gefs 00z suite has some continuity, we can expect a good 00z neafs update to follow. steve has described the general set up quite well above. its not so away far from the jan cold period though currently, the point of attack appears to be down the spine of the country as opposed to running at an angle to our sw. beyond that, the general evolution on naefs is for the atlantic to come further east over the top of the ridge at the end of next weekend and bring cold rain south with the shortwave running down the north sea. can we expect further retrogression ? perhaps, but it appears that beyond this possible less cold incursion, that shortwave energy will rebuild the euro trough and the atlantic ridge will build north again. thus the cold should return and at this point we can look towards a possible retrogression of the siberian ridge.

with a better set of ecm ens this evening wrt to the 00z run and the clear improvement in the gefs, i retract my post of this morning and reclaim my towel! the glass is again half full.

[chionomaniac]

I think for SM, one of the things that I have learnt from this year, is will be to suggest that SSW's will more likely lead to a disturbed tropospheric polar vortices, rather than necessarily to HLB's. Sometimes these may be coincident but other times not - such as this year. That is not to suggest that a disturbed PV cannot lead to a prolonged cold spell.

I have never suggested that SSW's definitely lead to HLB's but have always suggested that they will lead to a greater chance of this occurring - and this still remains true. But it seems that where I see possibilities that HLB's could occur and suggest this, many others see this as a definite - so that when I end up really pleased with the tropospheric response to the SSW, others end up disappointed. Something learnt for future I guess.

Promising outlook for mid Feb. The SSW disturbed tropospheric vortex effect will probably end by the end of the month anyway.

[Frosty.]

Yes Frosty lovely chart's there from 69.. Big turn around from the models today, everything seems to be falling in line with GP&Rogers forecast & timing, and they all seem very confident to me, as you say something epic could be on the way, Interesting times ahead for us model watches..!

Yes PM that would be a stunning event, before the last freeze even started, roger posted that the severe spell would arrive around mid feb and it looks like we are heading that way.

Edited February 1, 2013 by Frosty039

[Grimsby Snow Lover]

Yes PM that would be a stunning event, before the last freeze even started, roger posted that the severe spell would arrive around mid feb and it looks like we are heading that way.

Very exciting times ahead it seems which is great! Could someone tell me why the updated metoffice 30dayer doesn't scream severe cold as some on here are suggesting could happen. Thanks GSL

[ribster]

And I'll be more than happy to eat a large slice of humble pie if it does come off RP, frozen humble pie preferably.

If it occurs, I don't think you'll be the only one tucking into a delicious slice of that, still there will be plenty to go around!

[Summer Sun]

Very exciting times ahead it seems which is great! Could someone tell me why the updated metoffice 30dayer doesn't scream severe cold as some on here are suggesting could happen. Thanks GSL

They will always air on the side of caution which is fair enough however they do state

There are large uncertainties at this forecast range

Conditions will most likely start with temperatures close to or a little below average

There are signs that a slightly colder spell may then prevail throughout much of the rest of the period

[snowking]

I hope the below image helps to show the great uncertainty in the output beyond around 168-192, these are the 0z ECMWF Ensembles for Birmingham:

As you can see, some very tight clustering up until around this timeframe, before so much scatter that you can barely discern any sort of reasonable mean solution temperature wise - which looks to me reflected in the rather diluted ensemble means at present post 168

If we take a look at +168:

Still a pretty good definition to the output

If we move to +192:

A rather sudden loss of discernible pressure over NW Europe in particular

And of course as we move out to +240:

Whilst a fairly obvious trough visible from the mean heights, still a real lack of discernible pressure around the vicinity of NW Europe.

I'll keep an eye on the 12z once they come out and see if theres any noticeable swing

SK

Edited February 1, 2013 by snowking

[Frosty.]

Very exciting times ahead it seems which is great! Could someone tell me why the updated metoffice 30dayer doesn't scream severe cold as some on here are suggesting could happen. Thanks GSL

Because they are rightly ultra cautious and don't want to scare the beejesus out of the general population unless they have bullit proof confidence that a mega freeze is the likely outcome, but they are hinting at a colder pattern for second half of feb with widespread frosts, this will be the understatement of the year if RJS prediction comes true.

[SMU]

Snowking the ensembles on the ECM that are flat & against the pattern are distorting the mean flatter & further east.

Take the outliers out & watch that high rise up!-

the ECM 240 is excellent considering the opposing runs....

S

[be cause]

HELP .. as a newbe in my 50's only getting to grips with a second hand computer etc.. is there anywhere I can get the gfs or any other forecasts .. with the actual weather of the previous 24 or 48 or however many hours easily tagged on to the front of the forecast charts ??? I want to be able always to see where the weather came from again and it must be easy for any fool to do so help this one please THANK YOU in advance !!

[bryan629]

just click on the charts and data tab , third tab from the left on the home page , then on the right select the model you want.. easy peasy

[be cause]

oh ! and I do love this almost winter .. but dont worry .. snow is piling up all over the northern hemisphere esp. at altitude and polar maritime is not a bad source when the sea is cold

[Cloud 10]

HELP .. as a newbe in my 50's only getting to grips with a second hand computer etc.. is there anywhere I can get the gfs or any other forecasts .. with the actual weather of the previous 24 or 48 or however many hours easily tagged on to the front of the forecast charts ??? I want to be able always to see where the weather came from again and it must be easy for any fool to do so help this one please THANK YOU in advance !!

I presume you mean archived charts from the GFS? if so,here is the link.

http://www.meteociel...ode=0&archive=1

Archive charts are available from the ECM,GEM,UKMO and most of the other models on the same

site.

[Sussex snowstorm]

As what I seen this winter is that when a cold spell is coming in the models, the ukmo and ECM is normally on the cold side whilst gfs is riding them Atlantic systems quick and getting rid of any cold weather over the uk , whilst the ukmo and ECM keep the cold over the uk , in the past cold spell the ukmo/ ECM was more correct then the gfs , but when it was milder the gfs was more on the ball , then the ukmo / ECM , gfs was always uncertain till the nearer time Frame (last cold spell) are we heading the same way again with the ECM and ukmo becoming correct ? Or will the gfs over come it ? I know what I got my money on

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2013020118/gfsnh-0-120.png?18

GFS way better with less eastward movement & a more amplifed flow.,....

S

[Cloud 10]

A nice clean looking northerly on tonight's 120 hrs fax.

[Panayiotis]

A nice clean looking northerly on tonight's 120 hrs fax.

Yes and if you look at the previous frame it shows the occluded front up north which gives me the idea that the front had to pass down the UK to get to its position shown in the 120hrs chart, and with the 528dam line covering the UK, this band will produce snowfall as it passes. Edited February 1, 2013 by Panayiotis

[I remember Atlantic 252]

A nice clean looking northerly on tonight's 120 hrs fax.

Wishbone damn, snowless for many inland locations

[Isolated Frost]

There's plenty of things you can call modelling, but 'zonal' is not one of them

These upcoming charts are very promising, and the EC 12z solution in particular is very cold. Have a look at how Scandinavia is developing... that will be key for mid February- and right now it's looking like the cold pool is advecting south-west... and sticking there