Model Output Discussion - 23rd Jan - 12z onwards

[shotski]

Although it was nice to look at the GFS 06z op was a significant cold outlier after 3rd Feb

 

Expect changes on the 12z

An outlier 10 Days out, it's hardly lightly to get across the board support at that range ?

[summer blizzard]

A week of northerlies followed by a big, fat high if the 6z is to be believed.

 

[Jason M]

The GEFS 06Z is IMHO much better than the 00Z suite. Yes the PV is likely to intensify to our NW but that of itself doesn't preclude very cold weather in the UK. It really depends exactly where it sets up.

Re the Opp being an outlier, just need to remember that we are looking at the new improved opp which is high res out to 240. So we are comparing the new opp with the old GFS ensembles (IDO said they update in Q3). Also, I think the opp does actually have some support anyway.

Tbh,I'd bank the opp run given the chance. plenty of snow across most of the country on that one! Too far out to be taking seriously though.

Edited January 26, 2015 by Jason M

[Jason M]

A week of northerlies followed by a big, fat high if the 6z is to be believed.

 

Which would be followed a few days later by this http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=384&mode=0

Believe me, people wouldn't be arguing about marginality if that came to pass. Of course its all just speculation anyway.

[bluearmy]

Note the 06z gefs meaM stretches the vortex back towards Siberia and then splits it. Looking t the individual memebers, one wonders if the suite might be onto something. The feb forecasts are looking for a polar block

[The Weather Dragon]

Which would be followed a few days later by this http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=384&mode=0

Believe me, people wouldn't be arguing about marginality if that came to pass. Of course its all just speculation anyway.

This is what we need to see for prolonged nationwide snow & cold

[winterof79]

So was the Control.........

You were replying to:

Jonathan Evans

Yes a warm outlier and i suggest the OP was not that significant a cold outlier.I do expect changes on the 12zs......there always is.....it may get even colder

Edited January 26, 2015 by winterof79

[Ali1977]

Are any of the models showing the front crossing the UK on Friday as snow?  I know the GFS is showing a warm secter but was wondering if others maybe were showing colder air??  Also, are there likelt to be troughs in amoungst the Northerly flow over the weekend????

[frosty ground]

You were replying to:

Jonathan Evans

Yes a warm outlier and i suggest the OP was not that significant a cold outlier.I do expect changes on the 12zs......there always is.....it may get even colder

Yeah I would agree with that......

 

just a point as any one noticed the 2m Temps on the GFS Operational being a  few degrees warmer than all the Ensembles? 

[Timmytour]

This is the period of interest for me at +144!!

 

http://www.wetterzentrale.de/pics/Rtavn1441.gif

 

Some of the GEFS ensembles last night hinted at pressure rising towards S Greenland and instead of low pressure toppling the AZH we see low pressure going underneath. Now this is very much an outsider but a sudden flip at +144 towards a much colder NE/E,ly cannot be ruled out!

TEITS...just wanted to say that I was looking through the previous thread, from about 6 days ago at a time in the middle of the preceding "cold snap" we had and just after IF had bought down the mood of the place with regard to the further outlook. You stood up there, in the thread and dared to declare they might be wrong! And you said "look North!" So hats off to you.

Not, I hesitate to say that IF was wrong as such....he was only relaying the signals as they appeared to be at that time. But it's why I enjoy reading posts such as yours....they don't just tell me what the models are showing but give your assessment of what they might go on to show in future runs. Of course you are not always right, nobody is. And you didn't jump onboard with the current potential straightaway. But I am an admirer of your cool rational approach and the way you (for the most part!) post with the head and not the heart

[carinthian]

Our special internet portal for winter services gives a weekly update with probability percentages, especially as with regards to snow in the short term high resolution fine mesh model and a 30 day forecast trend . A snowy first week of February for many in Europe including the UK to start with followed by fairly pronounced pressure rise in the vacinity the British Isles , keeping the cold in Central Europe with snow threat continuing. By Mid -month still a good degree of confidence of signs of high level blocking to develop with retrogression of cells likely to feed a source of more Arctic Continent feed into much of Europe and the British Isles ( 40% probability rate ) as opposed to( 30% )probabaility to mobile Atlantic.

So all in all looking good for much of February, possibly with the most potent widespread cold spell of the winter to develop around the 3rd week of the month.

 C

Edited January 26, 2015 by carinthian

[winterof79]

I wonder if the Control and quite a few of the GEFS have picked up on more amplification to our west around the 156z period

 

Quite a few peturbs are toying with the idea which would sustain our "toppler" for a good while as Chio said.

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=156

 

EDIT:

As Carinthian has muted maybe a pressure rise to our West can trap the trough and allow it to feed of the the Siberian vortex lobe which is progged

Edited January 26, 2015 by winterof79

[Tamara]

Let's just remember that last Sunday, there wasn't much in the way of anything wintry for say, this coming Sunday. Possibly hints that something may have been on the horizon but we ALL know not to take anything beyond about 7 days with too much confidence, especially if only one or two models are showing it.

 

The winds have swung 180 degrees, 544-560dam replaced by 508-520dam, blocking in the Atlantic, LP coming up against blocking over Russia...need I go on?

 

Some of us are already looking 10-14 days ahead to find the end of this upcoming cold spell before it's begun.

 

 

Let's just enjoy what happens over the next few days, eh?

I agree there wasn't much face value evidence in the modelling of anything particular to come, but atmospheric signals were already plotting the way ahead quite clearly in tandem with advertised stratospheric displacement. In fact, if anything, I was a little too conservative with timing as we only have to look from mid week for the next wintry action to begin, and not the start of February

 

Tamara, on 19 Jan 2015 - 12:40, said:

 

Re-emphasis on yesterdays points remains the same as then and recent days - despite the rapid oscillations in recent days. More changeable conditions ahead - but it remains questionable at this time that there is any sustained return to westerlies.

 

At the same time as the pattern adjusts back, we have vortex perturbment that is piling up a hemispheric vortex ambush (not Pacific dominant, from both sides of the pole) courtesy of a lagged and laddered programme that ask questions of the re-cycling long term sustainment of this repetitious westerly pattern>

 

< the signal that I am reading from extended ECM data, which has picked up on GEFS suggestions of late, points exactly to that pincer movement I discussed yesterday from one side of the pole to the other. So the Pacific side might lead as we have seen, but tropospheric action through recent +East Asian Mountain torque, plus displacement pressure on the vortex...............>  a series of significant NH amplifications as cross polar ridging occurs and displacement activity stresses the upper vortex to our NW as pressure rises right over the pole.

Timing of all this perhaps not too long after the new month arrives (not far away). Renewed MJO activity into the Western pacific towards Phase 6 remains quite possible - and thereby still implies renewed forcing activity.

Its worth watching GWO forecasts in this respect.  We could quite conceivably, as recently, see orbit progression through 3 back to phases 4/5 and engineer yet another +MT early in February. The stakes then go up yet another gear

--------------------------------------------------------------

 

Posted by Tamara on 21 January 2015 - 13:41  in Forecasting Model Discussion.

 

Another day, and further clear evidence that this is not any sustained flat pattern re-set such as we saw after the late December mini Atlantic amplification.

 

<A clear cyclical -AAM NH pattern advertised so far this winter with the GWO for the most part locked into a Phase 1,2,3 and reverse 3,2,1 phasing  - we had that late December minI amplification, then the extended zonal gap to the current post mid month January amplification, and now the much narrower gap indicated between this and the next amplification already coming into view to coincide as suspected with the turn of the month.

 

No surprise though that usual continuity, and also in my own opinion, reliability in extended ensembles has started to break down within the last week. The emerging changes in the troposphere/stratosphere role-play relationship alerted suspicions some days back that longer term ensemble data might become less reliable  - this presaged mostly by the very recent +EAMT and break out of the GWO into orbit phases 4/5 round to 8/1 which has added a missing dimension this winter to a type of NH vertical wave activity supply that at the outset was assumed to play a much greater part in the winter pattern.

 

So, in respect of the implications of GWO/torque behaviour, a good illustration here of the value and importance in these tools when attempting to make forward suggestions as to the path that NWP might take and evolve towards. Also in this respect, very useful in trying to decide when longer term ensemble data might be heading in a questionable direction, or, at the least, when cyclical seasonal pattern trends might be overstated or even on the verge of changing path completely.

 

So, stratospherically there is now good support for pronounced euro trough allied to vortex displacement. We then also have vortex action of +EAMT

 

At face value the models don't suggest any upper ridge holding over the Atlantic sector, but there are increasing signals that the atmospheric pattern wants to attempt the sort of break-out that often blends itself towards a colder later part of a weak El Nino winter. A second GWO Phase 4/5 orbit following up the recent one is a good clue in this respect.

 

So, I am also suspicious about the lifespan of any far flung ensemble suggestion of returning further westerly mobility to follow early February amplification. Actually more suspicious than I was of the suggestions the other day of the impending return to less cold westerly mobility which, as suspected, is looking shorter than assumed

.I'm reasonably anticipating the Atlantic to increasingly be disposed to further meridional patterns through February and lead on to more definitive upper blocking

--------------------------------------------------------------------------------

 

The GEFS forecast for GWO phasing plots continue to advertise rinse and re-cycle of the pattern. However, next time will be determined by a different type of vortex stress. Displacement this time, next time a distinct split?

 

Notice the apparent symmetry in the predicted cycle to the post mid January period. The amplitude and progress of re-cycle is still open to question wrt GWO Phase 4/5, but further wave activity through +ve frictional torque and subsequent EAMT not out of the question I think. This potential second round of vertical wave activity has further added implications for that upper blocking potential for later in February

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png

 

We shouldn't worry too much about attempted vortex shift back to the Canadian side into next week as the displacement signal wanes and as the GWO moves through expected Phases 3/4 with any associated suggested flattening out of the pattern. This is for exactly the reasons given in copied posts above. A next westerly reset remains likely to be transitory once more, if it occurs at all.

 

The differences we can glean to mid January are the obvious bolstering of the cold tropospheric Siberian High (aided as suggested by recent EAMT), allied to the supplement of the cold air advection of the upcoming cyclonic northerly which looks to engulf much of western and northern Europe as well as the UK. 

 

Following stratospheric displacement, the odds are increasing on a stratospheric split that could well be primed to time with the next upstream amplification and this time have heights to the NE waiting in the wings to bring some elusive interest from that vector into the mix for the first time this winter. Unlike Feb 2005, which synoptically was brilliant, but didn't have deepest cold pooling from the beginning of that prolonged spell - any similar Feb evolvement this time might well have a better cold supply through the collective of a Eurasian High and the legacy of a displacement vortex cold pool to tap into.

 

In caution, still one or two jigsaw pieces to complete before this can be called with higher confidence - but the suggestion, as we head through February, of increasingly amplified patterns leading to a possible cold upper block have continued, thus far, to stay a constant theme since they were first muted a week to 10 days back

 

However, before any of these possibilities, I wholly endorse the suggestion that the upcoming week should be enjoyed by all who stand to benefit from it. Looking for the end of a cold spell before it has begun does not ever make sense, but I think the view should be taken that the closing winter pattern is putting more and more clear water between the dominant westerly pattern of the first half of the season

[Nick L]

Are any of the models showing the front crossing the UK on Friday as snow?  I know the GFS is showing a warm secter but was wondering if others maybe were showing colder air??  Also, are there likelt to be troughs in amoungst the Northerly flow over the weekend????

 

The ECM is showing that front to be of a wintry nature for the eastern half of the country, but slightly warmer air to the west keeps it as rain.

[johnholmes]

On IPad, excuse mistakes, not brevity, my password!

500mb charts have indicated the upcoming coldl spell

latest seems that Thursday is the start,

For 7 maybe 8 days ago!

Enjoy

[Mucka]

Before this evenings runs come out, a quick appraisal of where we are.

Wednesday evening/Thursday look the most likely periods to give meaningful snowfall with the North and West most favoured.

Thereafter cold with wintry showers, more especially in the North and East with this extending into next week.

All the output is solidly behind a warm up and return to mobile Westerly type around Feb 3rd/4th.

A small cluster of ECM members hold onto the cold a day or two longer but there is pretty much zero support for any blocking to form and hold back the Atlantic at this point.

 

So it is down to seeing what we can get out of this Northerly type over the next 6/7 days and hoping for some big change in FI to support a deeper cold once we are into Feb proper. 

I think the likelihood is we will be returning to a fairly stormy zonal phase as we head toward 2nd week of Feb but the milder flatter zonal regime may not be too long lived just as the last spell wasn't. I wouldn't be surprised to see another cold spell, deep Euro trough/Atlantic ridge, take shape as we head toward mid Feb.

It would be great to see a nice swing toward sustained blocking on the back of this spell but it looks quite unlikely at the moment.

 

If only GFS ppn charts were accurate.

 

 

That chart just 48h out.

Edited January 26, 2015 by Mucka

[Ali1977]

I know they aren't accurate, however there seems to be much more precip/snow showing on the GFS run upto T84...and on a wider scale.

[Captain Shortwave]

I know they aren't accurate, however there seems to be much more precip/snow showing on the GFS run upto T84...and on a wider scale.

The GFS sends a shortwave south east through the UK during Thursday afternoon

Note the kink around the Scottish border area, that will pep up the showers an organised them potentially into a band which swings south/south east. It's the things like that we will need to look out for during the coming few days.

Edited January 26, 2015 by Captain shortwave

[Ali1977]

The GFS sends a shortwave south east through the UK during Thursday afternoon

Note the kink around the Scottish border area, that will pep up the showers an organised them potentially into a band which swings south/south east. It's the things like that we will need to look out for during the coming few days.

If this is true then maybe the METO warnings will widen, and maybe extend into Friday...People may not see lieing snow everywhere but definately looks like most will have a chance of seeing some fall..

 

Lots more precip showing up on Saturday too....people saying it will be dry apart from the coastal regions prone may be wrong....

Edited January 26, 2015 by Ali1977

[Mucka]

Both GFS and UKMO already look more amplified upstream early in the runs, will it be enough to prolong the cold?

 

 

Overall I think for initial cold spell today has gone the right way, especially the gFS output which has moved things back East and stopped over-complicating the trough circulation so limiting warm sectors

Edited January 26, 2015 by Mucka

[BLAST FROM THE PAST]

 

Slightly higher pressure off SE of Greenland.....more of the same as 06z to follow?  Who knows but another t120+ chart that I like....this could be a cobra run

 

BFTP

Edited January 26, 2015 by BLAST FROM THE PAST

[Mucka]

Formidable Atlantic block on the UKMO

 

[Captain Shortwave]

Whatever the evolution at the moment, the output for next Monday keeps cropping up potential significant snow events

GFS

the western side of the UK sees a spell of snow moving south, east looks drier on this run (though with snow showers near coastal districts)

 

UKMO for day 6

Shallow low passing over the Atlantic ridge. I suspect the next day would show interest.

 

The ECM showed a deep depression pushing south east next Monday into Tuesday too from this morning. Something to watch. The GFS is showing some very cold air arriving next week (-10C isotherm pushing into Scotland by day 7)

All in all the next week offers plenty of fun and games I think.

Edited January 26, 2015 by Captain shortwave

[BLAST FROM THE PAST]

 

 

 

That LP to SW tip of Greenland from t174 to t180 has moved 'vertically' N and no Eastward progression...looking good.  Could be a lot of snow for West UK, Ireland from that feature running down, plenty of -8 uppers mixed in.

 

BFTP

Edited January 26, 2015 by BLAST FROM THE PAST

[nick sussex]

Formidable Atlantic block on the UKMO

 

Interesting UKMO, that shortwave south of Greenland is now crucial as to where it would go at T168hrs, to extend the cold that needs to head se with the upstream low amplifying sufficiently to allow some ridging to head north. The GFS has the same shortwave but further east.