Model Output Discussion 1200 hrs 15/11/14

[bluearmy]

Sorry knocker but surely that Icelandic 'vortex' is just a trough extension from the Canadian which will lose its identity over a few days?

Anyway, plenty of cause for cold optimism this morning as the models settle on the broad message from yesterday. As the Atlantic high tumbles around itself, it will send ridges north if there is upstream amplification delivering some WAA off the eastern seaboard. add to this the arctic high and you have added assistance to any potential topplers. But these don't look to be standard topplers. Yesterday's ECM op was too far west with the first depression and the ens spread around Denmark looks reasonable 12 hours later. gfsp does develop a more potent northerly and possible shortwave development in the base of the trough would keep us alert. That looks a bit unlikely currently.

Thereafter, it currently seems the second bite at the cherry may be more successful as per yesterday's ECM control. however, what evolves week 2 is currently open to conjecture with no specific pattern being consistent, run to run. from a very cold norwester as the Atlantic block retrogresses a bit ( could even allow a block in the greeny area though lowest probability) to a scandi high with low heights over Europe. That would also include the option of a mid lat block across us! What seems very unlikely is a zonal sw flow. I would say that the cold London ECM ens graph seem pretty reasonable as we head through December. Very seasonal indeed.

As an aside, there seems to be a decent agreement on a TD in the nw pacific week 2. too early to make judgements on what happens to it but could be a fun watch if it engages with the PFJ. (As nuri did).

Edited November 29, 2014 by bluearmy

[Captain Shortwave]

Day 6 charts

ECM

UKMO

GFS

Parallel

GEM

Just differences in amplification in the Atlantic, I suspect the landing zone will be between the ECM and GFS(P), so enough to bring another polar maritime airmass through the UK by the 7th December.

Beyond this, as the ECM shows, rinse and repeat sounds like a sensible option for now.

[knocker]

Sorry knocker but surely that Icelandic 'vortex' is just a trough extension from the Canadian which will lose its identity over a few days?

 

 

We'll have to agree to differ blue. To me at any rate following the sequence from T96 shows the movement of the Russian 'vortex'. True it does lose it's identity.

Edited November 29, 2014 by knocker

[knocker]

Matthew Hugo â€@MattHugo81 16m16 minutes ago

GFS v GEM v ECM at 240hr sig spread in synoptic patterns = lot of uncertainty/model volatility. pic.twitter.com/RG1vhRKbJr

[TSNWK]

Matthew Hugo â€@MattHugo81 16m16 minutes ago

GFS v GEM v ECM at 240hr sig spread in synoptic patterns = lot of uncertainty/model volatility. pic.twitter.com/RG1vhRKbJr

This is good news! When the models disagree changes are afoot

[IDO]

The second Atlantic high due in a weeks time was over amplified on last night's ECM. This morning corrections towards the GFS:

 

 

 

Right idea but too early due to the continued progress of the Canadian PV's journey east. It was very likely a toppler at best:

 

 

Again at D10 with the third Atlantic High ECM amplifies that but this time the Canadian lobe is much reduced: 

 

I can see the potential for an Atlantic ridge building after D10 but bearing in mind the MO of D10 ECM charts I have little faith at this time scale, as a downgrade to a toppler usually follows. GEM does its own thing and blocks the PV transfer around D7 and builds heights over Scandi with the Canadian/Greenland lobe remaining in situ; again on its own:

 

 

GFS have changed (again) the way they model the Canadian PV, they send it east and it recycles back to Greenland/Iceland/Pole via Russia, as Knocker suggests in a previous post:

 

Op:   P:  C: 

 

As others have said the GEFS have been very volatile with respect to the Arctic high developments so hopefully this suite does not set a trend as its not a pretty development. So uncertainty in the bigger picture but, ignoring the GEM, relatively good agreement between the other models in our quadrant for the next 10 days or so, and I assume that the GFS and ECM will meet somewhere in the middle re amplification.

Edited November 29, 2014 by i'm dreaming of...

[MR EXTREMES]

The second Atlantic high due in a weeks time was over amplified on last night's ECM. This morning corrections towards the GFS:

 

ECM1-168.gif  ECM1-168 (1).gif

 

Right idea but too early due to the continued progress of the Canadian PV's journey east. It was very likely a toppler at best:

 

ECH1-192.png

 

Again at D10 with the third Atlantic High ECM amplifies that but this time the Canadian lobe is much reduced: ECH1-240.gif

 

I can see the potential for an Atlantic ridge building after D10 but bearing in mind the MO of D10 ECM charts I have little faith at this time scale, as a downgrade to a toppler usually follows. GEM does its own thing and blocks the PV transfer around D7 and builds heights over Scandi with the Canadian/Greenland lobe remaining in situ; again on its own:

 

gemnh-0-240.png

 

GFS have changed (again) the way they model the Canadian PV, they send it east and it recycles back to Greenland/Iceland/Pole via Russia, as Knocker suggests in a previous post:

 

Op: gfsnh-0-264.png  P: gfsnh-0-264 (1).png C: gensnh-0-1-264.png

 

As others have said the GEFS have been very volatile with respect to the Arctic high developments so hopefully this suite does not set a trend as its not a pretty development. So uncertainty in the bigger picture but, ignoring the GEM, relatively good agreement between the other models in our quadrant and I assume that the GFS and ECM will meet somewhere in the middle re amplification.

either way as ba suggest nothing mild at all and im just pleased to see seasonal not really bothered whether it snows or not yet its the developements that matter and my its been the most interesting model watch since winter 4 years ago edge of ya seat stuff lots of possibles in the mix but not no zonal at all great stuff.

[nick sussex]

Behind the shorter term uncertainty a trend now to move the PV east looks likely, in terms of the amplification issues over the ne USA the GFS and GFS P are slightly more amplified this morning, the ECM tones down its amplification but still is more amplified than the former two with the UKMO the most amplified at the T144hrs mark.

 

There is however room for further changes over the USA given comments by NCEP:

 

...MODEL PREFERENCES/UNCERTAINTY ASSESSMENT...
THE PREVAILING FAST-ZONAL WESTERLY FLOW IS GENERALLY HANDLED BY
THE ECENS...GEFS AND NAEFS AS A SERIES OF LOW-AMPLITUDE WAVES FROM
THE NORTH CENTRAL CONTINENTAL DIVIDE TO THE GREAT LAKES THIS
MEDIUM RANGE PERIOD. THE KEY FEATURE OF THE FLOW IS THE RATHER
EXPANSIVE VERTICAL STRUCTURE OF THE TROUGH MIGRATING ACROSS THE
WEST COAST---DAY 3-4. THE SERIES OF SUBTLE 700MB WAVES THAT EJECT
FROM THE BASE OF THIS TROUGH---AS IT RACES ACROSS THE GREAT
BASIN...NORTHERN ROCKIES---AND TRANSLATE THEIR MOMENTUM DOWNSTREAM
INTO THE NORTHERN PLAINS AND NORTHEAST QUARTER OF THE NATION WILL
BE THE FORECAST CHALLENGE. TIMING THE SUBTLE WAVE ENERGY MIGRATION
AND THEIR ABILITY TO PULL CANADIAN AIR INTO THE LOWER 48

 

The colder solutions for the UK will be those that pull that cold air further south into the USA as these would correlate with more amplification over the ne USA.

 

In the broad scheme of things this shorter term uncertainty is really just the minor player because the movement of the PV east is likely to lead to some wildish swings in the output as to what happens afterwards.

 

Any ridge near the UK will be flattened by this movement however the negative anomalies near Iberia and into the Med support the high so effectively this stops any sort of mild zonal flow.

 

The case then is waiting for that transfer of the PV and seeing what the pattern is over the USA in terms of amplification which will decide the outcome downstream.

[Frosty.]

The only mild I can see on the charts is today, incredibly mild in the south with 16c 61f in places but it turns cooler and cloudier tomorrow and further ahead we will see an increasing risk of frost & fog with daytime temperatures struggling as a result. IMO we are much better placed for cold potential than a year ago. :-)

[bluearmy]

We'll have to agree to differ blue. To me at any rate following the sequence from T96 shows the movement of the Russian 'vortex'. True it does lose it's identity.

 

 

hope you can see where im coming from on this chart. the icelandic is just an extension from the canadian vortex.  maybe i'm not understanding what you meant in which case i apologise.

[nick sussex]

The only mild I can see on the charts is today, incredibly mild in the south with 16c 61f in places but it turns cooler and cloudier tomorrow and further ahead we will see an increasing risk of frost & fog with daytime temperatures struggling as a result. IMO we are much better placed for cold potential than a year ago. :-)

Yes the pattern is vastly different to last winter and as long as those negative anomalies remain in the Med then its a case of when not if something more wintry pops up.

 

There are several correlations between key winter time features and what the UK gets and low pressure in the northern Med is what you want to see if you're a coldie.

[johnholmes]

re this from Nick F last evening

Certainly the probable mean H500 pattern 8-14days, but this masks waves in the upper westerlies that may bring brief/transitory northerlies to the UK, the classic Nly topplers. 

Very true Nick, minor waves do develop and run through the major trough-ridge set up. These can sometimes confuse over a 48 hour period that a change is starting. That is part of the reason I prefer to wait 2 sometimes 3 days to see the anomaly charts 'settle'. Looking at things this morning and there is again a difference in how Ec-GFS suggest the upper pattern will be, see below. In these cases I tend to go with the pattern show by NOAA assuming it shows more consistency. No sign yet of any major pattern change.

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

[Barry12]

The ECM day 10 chart is a beauty. Ridging towards Greenland, Polar Vortex to the North of Scandinavia. That could be the start to a significant cold spell.

Things are getting very interesting!

[knocker]

gefs_z500_4800u_nh_33.png

 

hope you can see where im coming from on this chart. the icelandic is just an extension from the canadian vortex.  maybe i'm not understanding what you meant in which case i apologise.

 

No it's my fault, you are quite correct, my geography is askew, took the Faroese as Iceland would you believe. Another senior moment; the nursing home beckons.

[Captain Shortwave]

ECM ens

Day 7

At this moment the ensembles are generally seeing this cold snap as being similar to the one we will see on Tuesday/Wednesday. High pressure at the moment tending to squeeze out the coldest air, still chilly though with temperatures never really getting above average for the time of year.

[Cloud 10]

Yes the pattern is vastly different to last winter and as long as those negative anomalies remain in the Med then its a case of when not if something more wintry pops up.

 

There are several correlations between key winter time features and what the UK gets and low pressure in the northern Med is what you want to see if you're a coldie.

 

A good example of the above from the ECM 00z in its last 2 frames with high pressure pulling back into the Atlantic.

 

[lorenzo]

Some great volatility in model output from suite to suite at present, Indian Ocean MJO is mixing things up. You can read more about the MJO in the excellent link below from Kyle McRitchie.

 

Differing solutions from GEFS and ECM on how far this current event travels across the Pacific, thereby imprinting onto the atmosphere. UKME guidance does not go out as far as what we have available from ECM / GFS on the CPC site.

 

GFS

 

Note the high amplitude and also the progression through to phase 8.

 

UKMO / ECM

 

ECM less keen on this eastward progression across the Pacific.

 

Courtesy of WSI this next image shows the location of MJO / KW ( Blue) with a handy view of the Pacific Basin so you can see the MJO direction of travel. Indian Ocean > Maritimes > West Pacific > Central ( Fade) into origin or what is referred to as COD ( Circle of Doom)

 

So, we have phases 6-7-8-1 projected by the models.

 

From the Cassou paper here are the leading modes affecting Europe in each phase, have annotated where we are just now and going forward into December, there is no definitive dividing line generally each phase imprints within 6-10 days, bearing in mind the MJO travels slowly eastward where other components in the MJO signal move more quickly, so you may see on the modelling a blend of the composites or trending from one phase to the other.

 

Phase Plot Composite Anomalies for each of the phases

 

December Phase 6 Phase 7

 

December Phase 8 Phase 1

 

So, the question today -  is the MJO a little fast on GEFS due to the CCKW imprinting on the MJO diagram, or is GEFS suite correct and the ECM is yet to catch on and further amplify as it then sees Phase 8-1 also. Will be a good watch for the next week or so, Phases 8-1 really do herald fun and games for Xmas.

 

If all this is too garbled, watch this nice Diagram of the evolution of the MJO through the phases which clearly demonstrates the kick the MJO wave delivers to the mean flow http://envam1.env.uea.ac.uk/images/wh04_mslp1.gif

 

More about Waves, MJO / Kelvin Waves in this great guide  http://www.kylemacritchie.com/equatorial-wave-background/equatorial-wave-theory/

 

[IDO]

The ECM mean at D10 again does not support the op run; and synoptically in our sector of the NH is similar to the GEFS, although the latter sinks the mean heights further south:

 

 

 

No surprise that the GEM is an outlier, both its control and mean in line with the GEFS: 

 

 

 

In fact a million miles away from the GEM op! 

 

 

[carinthian]

Morning all. By Monday low pressure expected to be centred between the French Med and the Balearics and low heights to remain in the Western Med for much of next week and not sinking.

The main trough with this is likely to be further north and west of the Alps than was previously expected, so less of snowfall in the Eastern Alps with slight milder air here. Monday into Tuesday a NE ly flow from the Low countries, affecting France and SE England with perhaps more precipitation than expected previously. This pattern should help to maintain high pressure for much of the UK next week, so not sinking and a colder outlook for much of Western Europe this coming week. Thereafter, the high can only mitigate west and allow a flow from further northerly quarter, whether this becomes a toppler situation for your part of the world is too early to say, but certainly by this time next week increasing probablity some good snowfall can be expected in parts of Europe.

C

[knocker]

This alignment is much the same in the extended period but with connection Pole-Scandinavian, albeit it slim, HP and weakening of Canadian trough. Nothing to indicate to my uneducated eye any incursion of cold weather apart from brief cold snaps.

[Cloud 10]

Looks like another variant of the GFS has been included on the model verification pages which is the PRHW14N.

 

 

Model performance starting to fall off at the moment,probably due to their difficulties with high pressure over the Arctic,although the ECM seems to be holding its own at the moment.

[blizzard81]

Just for info: UKMO have modified 12z GM (versus raw/unmodified output seen on public websites) to make ridging more prominent out towards E/SE towards T+132, preferring the GFS 12z solution into that timeframe (and equally preferring as signalled in earlier UKMO-GM run).

Just want to highlight the above post from Fergie last night which some may have missed. The pro's at the met did not agree with their own model last night which means they didn't agree with the ECM either. You could see this when the modified fax charts came out last night - they made much less of the low pressure over southern Europe and placed more emphasis on the ridging from the azores. This is the interesting bit though - the updated modified fax charts this morning have done an about turn. They now agree with lower heights over Europe with the azores ridge much less prominent. It looks like the met should have stuck with their own model and ECM last night.

[Mapantz]

Just want to highlight the above post from Fergie last night which some may have missed. The pro's at the met did not agree with their own model last night which means they didn't agree with the ECM either. You could see this when the modified fax charts came out last night - they made much less of the low pressure over southern Europe and placed more emphasis on the ridging from the azores. This is the interesting bit though - the updated modified fax charts this morning have done an about turn. They now agree with lower heights over Europe with the azores ridge much less prominent. It looks like the met should have stuck with their own model and ECM last night.

At what days are we talking? I only ask this, as days four and five only get updated once a day on FAX charts (to my knowledge) which means they wouldn't have updated yet?

[blizzard81]

At what days are we talking? I only ask this, as days four and five only get updated once a day on FAX charts (to my knowledge) which means they wouldn't have updated yet?

On an evening they update to day 5 and on a morning they update to day 3. The timeline I am referring to in my post is the 72hr period. In this period, the fax charts underwent a flip overnight whereby pressure over southern Europe is lower and also influencing events more over the low countries and France (see carinthians post this morning) and as a result, the ridging from the azores is less prominent.

[legritter]

Still in my opinion plenty to be cheerfull about past 6/7 days .it would have been good to see todays GFS runs go more for high pressure to our n/west but there is plenty of big change from run to run .Ecm is looking good at 6/7 days ,but the big picture at about a week away seems to be Where will any high sit ,which of course is crucial to weather at the surface over good old uk .IM pretty sure that if a northerly with cold 850 s and pressure low to our north east is on its way in about 8/10 days we should start to see plenty of signs over coming 48 hrs .we must look for consistancy and agree ment at the 7 day range ,beyond that the Horizon is as clear as MUD i feel but still interesting enough for a bit of Model Discussion ,Interesting times ahead and it starts proper Monday for 13 weeks ,Did you all get your Black friday STELLAS IN ,