Model Output Discussion; into 2015

[Frosty.]

WOW the Gfs 12z operation run really works itself into a frenzy with bouts of cold and stormy weather as a few weather bombs explode over the UK, the most disturbed spell is later next week onwards and it looks cold enough at times for snow.

[Tamara]

 

 Cue corresponding negative frictional torgue and negative mountain torgue over the US (cue renewed Wave 2 activity to follow up vortex split).

 

The MJO re-starting in Phase 3 with a fresh convective signal in the Indian Ocean is responsible for this poleward AAM momentum burst and accompanying movement of the GWO into phases 3/4. This is characteristic of a Nina atmospheric response. The problem with this cycle being rooted in the western hemsiphere is that cannot provide extra forcing on the pattern we need - as convection returns to the Indian Ocean before crossing the dateline. On that basis will predicted momentum through the Pacific of the MJO be sustained further than the last circuit?

 

This whole Indian Ocean rooted signal underpins the negative AAM tendency/ GWO Phase 3/4 and back to Phase 1/2 cycle and is also characteristic of the current Nina state of the atmosphere.

 

No surprise therefore that such a Nina type signal dogs us with a sub tropical ridge problem with a string of anomalous sub tropical ridges across the NH mid latitudes with the Azores High spoiling the pattern in our vicinity - and only becoming 'useful' when the Pacific pattern temporarily retracts in Phases 1/2 and provides us with some Atlantic amplification.

 

This is pretty much where the 'negative' news is derived form.

 

The continued MT events, as described, should continue to provide us with plenty of vortex ammunition to follow up the upcoming split on the vortex. It is true that these stratospheric forecasts might upgrade - however the pre-disposition of the atmospheric state and the Nina signal rooting in the Indian Ocean and Western Pacific continues to favour the -EPO ridge blocking the wrong side of the pole and not cross polar ridging to our side of the pole, whilst at the same time supporting return of the Canadian/Greenland vortex when tropospheric wave activity has split the vortex our side of the pole. The models currently support this scenario. As bluearmy said earlier today, we could do with a longer window of a split and fast further wave 2 activity bombardment. As discussed, this is expected vis GWO orbit return to Phase 2, but can it happen soon enough before the vortex has chance to reform once more across the pole?

 

Its great to have a weak vortex which is amenable to splitting quite easily this winter. However, it can be seen what the requirements are to take advantage of these splits. The unfavourable Pacific and sub tropical pattern is very much cancelling out (at the moment) the attempted cold pattern feedbacks over the polar field.

 

on the basis of what I have been discussing (not for the first time) understanding is becoming greater why the METO suggested a prevailing +NAO pattern into the winter with greater uncertainty into the second half of the winter.

 

There remains obviously plenty of time, and the watch is how we can break out of this atmospheric rut during January, to take advantage of a very weak and vulnerable vortex and transfer its goods to this side of the Northern Hemisphere.

 

 

　

　

A very good summary indeed from Nick F this afternoon about the pitfalls of the current unfavourable Pacific pattern  .

 

In my recent post, copied above, I discussed the problems with this La Nina type atmosphere response and how it might be stubborn to resolve.

 

Positively, the good suggestions continue of sustained wave activity assault on the polar vortex right into the first part of the New Year. We do not yet have any indicated SSW, although maybe quite close to one - and thus we can only keep looking to updated forecasts in this regard. We still have to look beyond the first half of January anyway to start to see any realistic benefits of this at tropospheric level to drastically improve the current woeful NWP - even if things evolve favourably.

 

One thing is clear enough however - suggestions a few weeks back that a full blown SSW wouldn't be necessary (on the back of aggressive SIA and SCE autumn feedbacks in tandem with a -QBO to assist fast poleward propagation of troposphere/stratosphere Rossby wave breaking) seem somewhat remiss.

 

These suggestions I sure don't think were meant casually in any way, and were based on the information and progress apparent at the time - but they do underline the fact that the atmospheric state has to be conduisive to allowing these factors to deliver the potential to a cold pattern they most definitely possess.

 

The unfavourable Pacific pattern clearly is manifesting itself downstream in the Atlantic and all modelling is unanimous of the way ahead for the foreseeable future - pending those developments above us.

 

The SST arrangement of very warm water anomalies off Newfoundland will exacerbate the upcoming zonal pattern by steepening gradients as cold air meets it but also it represents part of an overall SST signature which further supports the adverse +NAO pattern in the Atlantic

 

-AAM GWO Phase 1,2,3 - 3,2,1 represent an ebbing and flowing cycle that re-imprints the North Pacific High, Canadian vortex and resurgent sub tropical ridges (Azores High) with every Phase 3 return of the MJO to the Indian Ocean. As repeated, transitory amplification sequences occur in GWO Phase 2 before the pattern flattens out once more from upstream.

 

Breakdown of the MJO convective passage through the Pacific and return to the Indian Ocean in Phase 3 automatically re-sets the Phases 1 to 3 and 3 to 1 cycle - and so in this way can lock in such a pattern for anything up to a month through the subsequent cycle, depending on how the renewed ocean vs atmospheric responses behave.

 

It is on this basis, with entrenched -AAM, that optimism about the current MJO wave arrving at Phase 7 and on into Phases 8/1 to provide very welcome and helpful forcing on the stuck pattern is rather low as I see it right now.

 

I obviously wish to be proved very wrong!

 

December imprinted the Nina pattern, and tanked -ve AAM tendency in the process, with the return of convection to the Indian Ocean, and any return and repeat process during January will surely do the same.....

 

How might any SSW (the bigger the better!  ) alter the Nina style state of this pattern and improve the chances for arriving at a cold pattern in the UK (and NW Europe)?

 

The answer to that, in terms of context to the -AAM Nine type cycle. is that we would require such a vortex  'detonation' should we get one, to simultaneously occur in amplified GWO Phase 2 to give us a chance of breaking the rut and leading to any chance of a sustained flip to a -NAO.

 

Failure of the NAO to stay negative after any -AO induced SSW would force advected polar cold north once more - as the Azores High is re-engaged, returning the NAO +ve as response to the GWO progressing onward into Phase 3 and the MJO returning convection to the Indian Ocean. The effect of Phase 3 under -AAM is re-engagement of the Azores High into mid latitudes and to consequently send the jet stream back northwards...  lifting out the cold air - and prematurely ending any cold spell.

 

In January 2009 a -AAM state prevailed and we witnessed a similar problem with the Azores High in February spoiling and cutting short the cold potential for this very reason that followed the massive SSW of January 23 which downwelled to lead to the Scandinavian High at the end of January and start of February and attendant snowfalls.

 

This breakdown occured as a result of the GWO phasing not being ideal to maximise the -AO/NAO potential - and the poleward energy transport (re-invigorating the northern jet stream branch) associated with Phase 3 mitigated attempted retrogression of the Scandinavian High to Greenland (which would have prolonged the cold spell courtesy of fresh cold air advection from the pole)

 

In January 2009 we were in a westerly QBO and solar mimimum (which made the SSW an unusual occurence in itself).

 

This year we are descending a solar maximum, which is inhibitive to fully utilising blocking potential - but otherwise there are quite a few possible parallels ahead with January 2009 in terms of trying to 'de-demonise' the Nina-esque re-appearance of the Azores High !

 

So ( assuming it verifies at all) in order to benefit fully from any SSW induced beaten up polar vortex - we require a window of timing (amplified GWO Phase 2 Atlantic state) to occur at the same time as the tropospheric effects of downwelled -ve wind anomalies propagate to the surface from the higher stratosphere.

 

Should we fail to engage ideal timing of SSW and -AAM phase cycle, then any potential cold spell risks being cut short in the same way as Feb 2009. However, that is getting way too far ahead.  ..and we have to get to the position of an SSW verifying in the first place, and then propagating successfully in such a way that benefits us in the UK. We would surely take a 2009 reprise with both hands atm in the face of such repugnant NWP output

 

At least we have 2009 however as some kind of benchmark to show that even under -AAM Nina type patterns, we can still get to a cold pattern with a suitable SSW forcing on the vortex. However long this may last (if it happens)...

 

Changes of wavelength later in the winter, and more especially into March, alter -ve AAM and GWO phasing towards greater disposition to pattern amplification - and decay of cyclically induced sub tropical ridging. But clearly this is later than most of us would hope at this time - especially on this thread.

 

Methinks this will do for now

Edited December 30, 2014 by Tamara תָּמָר

[Iceberg]

Looking at the models, yet again, i can see westerly winds prevailing, although there is a hint that things could get much milder indeed. No hint of cold unfortunately.

I can feel a mild January coming up with perhaps a colder late February/March. 

 

I know that a few have tried to defend this comment, but simply there are very few hints in the models that things could get much milder, nor is there anything really to indicate that it will be a mild january nor colder late feb or march.

If we actually look at the the latest GFS (since the EC isn't out yet), we get far more of the T144 and beyond with 850s at 0 or below a few glancing +0's that last 12 hrs or so and far more -4's and below.

The problem with this kind of changable set up is that you can always select charts that show +4 850s in a strong SW, but they are not the dominent type. 

I rather think dragan know this......

[Iceberg]

Just to add Blues comment on the strat thread  this morning sums up perfectly my thoughts as well, but its done far better than i could possible do it. Fantastic post.

[Gowon]

ECM and UKMO are nearly identical at 120

 

 

[Captain Shortwave]

So week 3,4,5,6,7,8+ could be cold, not a bad position to be in really

Or they could be mild 

Anyway back to the models.

Probably the only straw to clutch

It might develop favourably (Scandi wedge) or it might not.

Well it's a little better

Forget it, intermission ends at day 8.......

Edited December 30, 2014 by Captain shortwave

[Betleyblizud]

Looking at the models, yet again, i can see westerly winds prevailing, although there is a hint that things could get much milder indeed. No hint of cold unfortunately.

I can feel a mild January coming up with perhaps a colder late February/March. 

Given that the GFS(P) indicates some possible PM air towards the end of its run and that this could result in some snow, particularly at height, can you explain to me how there is "no hint of cold"? Many thanks for your help.

[Continental Climate]

Cant imagine us getting much from this chart http://www.meteociel.fr/modeles/ecmwf/runs/2014123012/ECH1-144.GIF?30-0!!! Unfortunately the PV over Greenland and baffin is just too strong at present and will take some shifting!! It seems that that all our eggs are now in the stratosphere's basket with nowhere else to put them. It seems that even if we do get PV disruption or split a big fat lobe of the vortex ALWAYS moves to greenie/baffin!! No matter how hard you polish a turd it remains a turd, and that chart is very turdish I'm afraid!!!

[Iceberg]

Good EC T144, Short wave developing in the instability wake within cold 850's, Strong diving jet and plenty of -4 to -10 850's set to sweep in.

Not to mention the Arctic high that wasn't there previously as mentioned above.

[Frosty.]

Coldies might be a little happier with the 12z runs, it's a very disturbed outlook and cold enough at times for significant snow, especially on hills..all to play for.

[Cloud 10]

The models are clearly struggling to resolve the effect of the zonal wind reversal through the atmosphere in the fairly short term,an example of which shows nicely when comparing today's 

12z 144 hrs ECM with yesterday's 168 hrs.

 

today..  yesteday

 

 

Seems to be a bold prediction that the zonal train will choo choo along till mid-month!

 

 

 

[Continental Climate]

A decent cold pool developing in eastern europe by 168 http://www.meteociel.fr/modeles/ecmwf/runs/2014123012/ECH0-168.GIF?30-0!!! Of course that means diddly squat for us if we dont have any means to advect it our way, which we don't at present. We have cold to the left of us, cold to the right and were stuck in the middle with nowt!!! 

Edited December 30, 2014 by Continental Climate

[Iceberg]

Nice T168 from ECM, It creates a 1025mb high above Scandy, where it had sub 1000 pressure previously and places the the other arctic high favourable.

The small plume of warmer 850's look like they will provide support with WAA (red arrow).

 

[chionomaniac]

Big lower strat split on the latest ECM I bet! No trop jet stream breaks through that type of split - it hits the proverbial brick wall. If the split is only partial like the GFS, then the trop jet stream flow continues across the Atlantic. Which model is right?

[IDO]

Nice T168 from ECM, It creates a 1025mb high above Scandy, where it had sub 1000 pressure previously and places the the other arctic high favourable.

The small plume of warmer 850's look like they will provide support with WAA (red arrow).

The problem is the huge PV to the NW. That will edge east and any block will have to be strong to resist that. GEFS over the last few days have had charts like that but not one has ever stopped the PV moving east towards the UK, it is an irresistible force.

[Duane S.]

The problem is the huge PV to the NW. That will edge east and any block will have to be strong to resist that. GEFS over the last few days have had charts like that but not one has ever stopped the PV moving east towards the UK, it is an irresistible force.

Sounds good to me, will allow ridging in behind

[Continental Climate]

There is not a lot we can do im afraid when faced with a chart like this. http://www.meteociel.fr/modeles/ecmwf/runs/2014123012/ECH1-192.GIF?30-0!!! There are height rises over the pole but they are totally in the wrong place for us and all they are doing is pushing more of the hated vortex right above us which is where we don't want it. What use are strong height rises over Kamchatka and eastern Siberia to us? No use whatsoever I'm afraid the chart above is utterly zonal and a bit of a winter killer  not bad for Ben Nevis but useless for the rest of us. We need something to change soon. 

Edited December 30, 2014 by Continental Climate

[Frosty.]

Scottish ski resorts will love the Gfs 12z, they may get snow bound in the cairngorms..brrrrr

[mulzy]

There is not a lot we can do im afraid when faced with a chart like this. http://www.meteociel.fr/modeles/ecmwf/runs/2014123012/ECH1-192.GIF?30-0!!! There are height rises over the pole but they are totally in the wrong place for us and all they are doing is pushing more of the hated vortex right above us which is where we don't want it. What use are strong height rises over Kamchatka and eastern Siberia to us? No use whatsoever I'm afraid the chart above is utterly zonal and a bit of a winter killer not bad for Ben Nevis but useless for the rest of us. We need something to change soon.

Horror show - we're looking at a CET anomaly of at least +1.0c for the first 10 days of January.

Charts are textbook zonal - not even a hint of sustained cold.

Edited December 30, 2014 by mulzy

[Iceberg]

The problem is the huge PV to the NW. That will edge east and any block will have to be strong to resist that. GEFS over the last few days have had charts like that but not one has ever stopped the PV moving east towards the UK, it is an irresistible force.

Pressure over 40mb higher off the north Russian coast on this 12z EC compared to 0z. Jet much weaker and fails to make inroads into northern europe., far  better imho. jet pushed around 500 miles further west

[phil nw.]

Just a heads up folks.

 

Posts that only have views based on hopes or hunches may have been moved here

https://forum.netweather.tv/topic/81281-model-banter-moans-and-ramps-autumnwinter-2014/

 

so if anyone has seen their post disappear from this thread have a look in there.

 

OK back to model discussion.

[DEYS(Kent)]

ECM at 240 has HUGE potential. Granted, it is out at post D10 but could this be the start of the strat conditions filtering into the model output?

[Iceberg]

Huge arctic block on 12z EC at T240, no doubt a quick response to the Strat changes imho, positioning is to much of a consequence.

Massive change, but we need to see more over the next few runs, all as expected though.

[mountain shadow]

Huge arctic block on 12z EC at T240, no doubt a quick response to the Strat changes imho, positioning is to much of a consequence.

Massive change, but we need to see more over the next few runs, all as expected though.

Completely in the wrong place for us though surely. How does the PV drain away into Siberia with a big block there?

Edited December 30, 2014 by mountain shadow

[Continental Climate]

Huge arctic block on 12z EC at T240, no doubt a quick response to the Strat changes imho, positioning is to much of a consequence.

Massive change, but we need to see more over the next few runs, all as expected though.

I know i'm a novice but this chart doesn't scream potential to me in fact it looks pretty flat and zonal. What minimal height rises there are are in a useless position for us and they are simply pushing more vortex to our side of the planet. Hope im wrong though as i need a straw to clutch. Maybe chiono or some other poster can tell me im wrong about this.