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

[Jason T]

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.

[Froze were the Days]

GFS continues to be a complete pain in the backside as regards in being progressive with the Atlantic as it has done most of this winter whilst ECM shows a more amplified pattern off the Canadian seaboard and builds heights to our North East which could show something more significant in 8/9 days. A long way to go as always.

[bluearmy]

Why are so few of you realising the big change re the 12z gefs?. Forget the op. It's just another ens member in low res. ECM ens imminent. Very important from my perspective.

[snowking]

Well i've now got access to the ECMWF 2m ensemble for europe as it rolls out, we're out to day 10 now, and NW Europe is running around 1-2c colder than the 0z mean (average 0-3c away from the far SW and Ireland, where its nearer 3-6c)

Now awaiting the pressure means to see where we stand, but all steps in the right direction so far this evening

SK

[Bristawl Si]

This looks exceptionally promising for severe cold by the middle third of February.

The dive-bombing low on Tuesday will turn into a wintry hurricane for northern regions of the UK and in itself is a major severe weather event, but after a couple of days it will reach a position over central Europe that will allow a retrograde cycle just showing signs of life now to develop gradually and feed the coldest Siberian air west across northern Russia into Scandinavia.

I think there will be near-record cold in mid-February and that means daily means in the -5 to -10 C range, so a very severe frost and with a northeast flow there may be heavy snowfalls even without any organized low pressure, but this winter also has shown a tendency to storminess so I have the feeling once this very cold air starts moving in, there could be epic snowfalls with it.

The eastern Canadian vortex from my research can be expected to last about a week then start to drift northwest to become another part of the hemispheric retrograde cycle. Heights will then build over central-eastern North America and they could go from the current cold pattern to very mild in about ten days to two weeks.

I think it's coming anyway, and this storm on Tuesday is the pattern changer much as there was a severe windstorm around 1 Feb 1969 although that was more of a straight northerly blast. But the temperature signal from very mild to very cold is similar, and don't forget that also happened (a bit earlier in late January) in 1947.

A brave prediction Roger - let's see what happens.

[Brassneck]

Well i've now got access to the ECMWF 2m ensemble for europe as it rolls out, we're out to day 10 now, and NW Europe is running around 1-2c colder than the 0z mean (average 0-3c away from the far SW and Ireland, where its nearer 3-6c)

Now awaiting the pressure means to see where we stand, but all steps in the right direction so far this evening

SK

I've never posted in the model forum before but am an avid reader.

Are you able to do this for a series of runs over the last few days just to see what the variability is from run to run. Couldn't the next run be equally 1 - 2 c higher than the 12z?

Thanks

Stephen.

[BLAST FROM THE PAST]

No more to be said, ECM continues with the thoughts, RJS has made his post...and those thoughts have not changed since way back in early autumn. The build up continues and the timing is there....10-15 feb for main retrograde signal/push, build up before...and models have been latching onto the build up all week.

My Monthly update on Sun, got a concern with my old man's health at mo so rather 'distracted'

BFTP

[ForeverPomeroysnow]

BFTP - My Father passed away last week so understand the concern for yours, love him and cherise him.

Sorry if off topic mods

[damianslaw]

UKMO, GFS and ECM all showing a cold northely airstream by Tuesday lasting through at least until Thursday with sub 528 dam air invading most of the country - any precipitation will very likely be of a wintry flavour, especially further north, showers are very likely to give accumulations of snow where heavy and long lasting - NW parts look most prone to showers on Tuesday and Wednesday, with the north and then NE more prone Wednesday into Thursday.

As is often the case, there is a difference between ECM and GFS as we move beyond the reliable timeframe. The reason for the difference is in there modelling of the Canadian Vortex. GFS wants to maintain it as a very strong feature preety much in situ, allowing further energy to spout off from it into the atlantic thus cutting off the cold feed by the end of next week and a return to wet westerlies, with polar maritime air not far behind. However, ECM is suggesting the PV will have less energy and shift slightly westwards combined with heights building to our NE behind a southerly digging trough heading into central europe and look what is lurking to the far east - the russian high which has a clear path to nosedive its way into scandi - the outcome eventually would very likely be a potent easterly - very 80's February esque....

Its too difficult to call, both scenarios could easily play out, the key player is the Canadian Vortex which has dictated our weather so far this winter, if it begins to advect westwards even ever so slightly and weaken a little, then the ECM evolution is very plausible, however, if it refuses to move from its current position with similiar intensity then the GFS evolution is most likely - but this doesn't mean no chance of cold wintry weather, as evidence by what we are likely to see mid week next week, but it will make the chances of a significant prolonged cold spell much more difficult.

One positive for cold lovers, is traditionally regardless of any other factors, the PV weakens during February which increases the chances of heights building strongly enough to hold the atlantic at bay.

[snowking]

I've never posted in the model forum before but am an avid reader.

Are you able to do this for a series of runs over the last few days just to see what the variability is from run to run. Couldn't the next run be equally 1 - 2 c higher than the 12z?

Thanks

Stephen.

Hi Stephen

Unfortunately the comparison tool i've got only shows inter-run change from the previous issue (i.e. 12z > 0z, 0z > 12z). However, there is an archive of actual temperature forecast, looking at this for a specific date within range:

13th Feb 12.00GMT:

Things have trended around 0.5-1c cooler since the 12z run on 29th Jan (as far back as I can go for that date)

Incidentally the whole run is now out, the UK is around 1c warmer vs 0z suite post 300hrs, but NW MAINLAND Europe is around 1c cooler...so in the extended range the De Bilt ensemble mean may be a touch cooler than the 0z....in the medium range (192-300) the whole of NW Europe is around 1-2c cooler than the 0z suite, so expect a bit of a downward trend from the 0z mean around this time range on both De Bilt and London ensembles. And in all honesty, its upgrades in terms of cold in this timeframe that I like to see - post 300 is still very open to change!

SK

Edited February 1, 2013 by snowking

[cooling climate]

It wasn't a dig at yourself and I do apologise if it came across as such, a lot of my angst is borne out of frustration at how a synoptic pattern which should have been conductive of cold has failed to deliver. I retract my earlier post Chion and hopefully we can draw a line under this and move on.

There has been a lot of talk this winter of a smashed PV and final nail in the PV's coffin when of course that

has not been the case at all. You will never see the PV destroyed in winter it is impossible.

I think though you have your wires crossed in so much as it was I who has been posting a lot the

last couple of weeks of the second phase of the SSW and a much more blocked and amplified

-AO and that this would happen along with a colder outlook from around the end of the first week of

February with hopefully a true freeze setting in around the middle of the month.

The ECM output today does indeed show a much more amplified pattern setting up in that time frame

with the blocking to the north and northeast and a east/northeasterly airflow rather than northerly as

I don't think we will see Greenland heights for a while yet.

Whether any of this verifies remains to be seen and I am not trying to blow my own trumpet here as

things could go pearshaped very quickly but after reading a few of your posts I thought I should say

something. Cheers.

Edited February 1, 2013 by cooling climate

[Methuselah]

This looks exceptionally promising for severe cold by the middle third of February.

The dive-bombing low on Tuesday will turn into a wintry hurricane for northern regions of the UK and in itself is a major severe weather event, but after a couple of days it will reach a position over central Europe that will allow a retrograde cycle just showing signs of life now to develop gradually and feed the coldest Siberian air west across northern Russia into Scandinavia.

I think there will be near-record cold in mid-February and that means daily means in the -5 to -10 C range, so a very severe frost and with a northeast flow there may be heavy snowfalls even without any organized low pressure, but this winter also has shown a tendency to storminess so I have the feeling once this very cold air starts moving in, there could be epic snowfalls with it.

The eastern Canadian vortex from my research can be expected to last about a week then start to drift northwest to become another part of the hemispheric retrograde cycle. Heights will then build over central-eastern North America and they could go from the current cold pattern to very mild in about ten days to two weeks.

I think it's coming anyway, and this storm on Tuesday is the pattern changer much as there was a severe windstorm around 1 Feb 1969 although that was more of a straight northerly blast. But the temperature signal from very mild to very cold is similar, and don't forget that also happened (a bit earlier in late January) in 1947.

I would very much like to see that come-out right, Roger...I remember 1969 well!

[Tim Bland]

We've seen before when the ECM is against the GFS the answer lies in the ensembles ... I'm afraid not 1 GFS ensemble even for Averdeen gets to -10 uppers. Until at least a few ensembles buy into the ECM op I won't be forecasting snow hurricanes or waxing my skis

[Jason T]

BFTP - My Father passed away last week so understand the concern for yours, love him and cherise him.

Sorry if off topic mods

Its not of topic with these situations and i would like to express my sincere sympathy's for your loss and im sure all on the site and apart of the thread share the same thoughts.

Jason.

Edited February 1, 2013 by Jason T

[Frosty.]

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!

Fingers crossed for an EPIC month ahead

[Ladyofthestorm]

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?

[SMU]

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.fr/modeles/ecmwf/runs/2013020112/ECH1-192.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.fr/modeles/ecmwf/runs/2013020112/ECF0-240.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

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...

[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?

Here they are Ladyofthestorm

That must be the coldest westerly ever.

Edited February 1, 2013 by Frosty039

[Polar Maritime]

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!

Fingers crossed for an EPIC month ahead

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..!

Edited February 1, 2013 by Polar Maritime

[Summer Sun]

Evening, here are the ECM ensembles

[SMU]

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

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

S

[Panayiotis]

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

00z?

[SMU]

00z?

no 12z. update your cache.

[UV-RAY]

I would very much like to see that come-out right, Roger...I remember 1969 well!

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.

[Tom Quintavalle]

"I think it's coming anyway, and this storm on Tuesday is the pattern changer much as there was a severe windstorm around 1 Feb 1969 although that was more of a straight northerly blast."

Interesting re. Rogers thoughts about a possible evolution similar to Feb.1969.

Tomorrows ECM chart at 12z - http://www.wetterzen...ics/Recm241.gif

3rd Feb 1969 - http://www.wetterzen...00119690203.gif

Forecast chart for 6th Feb - http://www.wetterzen...cs/Recm1201.gif

8th Feb 1969 - http://www.wetterzen...00119690208.gif

Forecast chart 8th Feb - http://www.wetterzen...cs/Recm1681.gif

10th Feb 1969 - http://www.wetterzen...00119690210.gif

You can see some similarities between the poss. evolution this Feb and what actually occurred in 1969.

The obvious difference being the lower heights and segment of the PV west of Greenland.

IF this segment were to weaken as we move into the 2nd week of February, its not out the question to see a similar

scenario developing, poss. SE diving low and Russian high waiting to pounce and trundle into Scandinavia.

I'll leave you with a little look further into that Feb. of 1969.

http://www.wetterzen...00119690213.gif

http://www.wetterzen...00119690215.gif

http://www.wetterzen...00119690219.gif

Weather Gods, make it so!

Regards,

Tom.

Edited February 1, 2013 by TomSE20