Model Output Discussion 29th December - Into mid-Winter.

[bluearmy]

14 minutes ago, nick sussex said:

I'm wondering whether the outputs are reading the MJO signal slightly differently. As it is the MJO is weak at the moment. Matt H mentioned this is going to be in phase 5 however the MJO forecast  which tries to remove interference has this about to enter phase 6 and stay there for around a week.

It's of course questionable just how much impact this might have on us in western Europe given its low amplitude however phase 6 normally adds some amplification to the Atlantic.

The actual composites can be rather rigid tools because what ENSO is doing at the time needs to be taken into account, currently we're in a weak La Nina with this declining towards neutral values.

If we take it that the MJO is in phase 5 and could go into phase 6 depending on which forecast you use the research suggests this:

Phase 5 is associated with enhanced trough anomalies over the North Atlantic extending across north-central Europe, and across parts of eastern Asia, with substantial significant ridge anomalies over western Russia. Phase 6 is associated with enhanced trough anomalies over far northwestern North America and parts of East Asia, with significant ridge anomalies over the North Atlantic and parts of interior Europe.

Interestingly if you follow the ECM on the NH view you'll see a pretty good correlation with the above although it makes less of that ridge anomaly in the North Atlantic.

Again though we are dealing with a low amplitude MJO signal so this is likely to mute out some of the trop response and of course there are other factors to take into account.

PS If you were just using the standard MJO composite this doesn't show that strong ridge anomaly in western Russia,  you might conclude that the NH pattern is more closely following that research which  looked at not just whether you were in say El Nino or La Nina but more importantly were they declining or advancing and the different impacts that could have on the NH pattern.

Careful re the MJO nick

it's a few weeks since it was in any amplitude and I am suspicious that without any clear drivers (strat zonal wind and qbo aside, ) people tend to adopt it as an indicator when it isn't actually likely to have any influence 

unless we see some x model agreement and amplitude then I suspect it's irrelevant.  

[nick sussex]

Just now, bluearmy said:

Careful re the MJO nick

it's a few weeks since it was in any amplitude and I am suspicious that without any clear drivers (strat zonal wind and qbo aside, ) people tend to adopt it as an indicator when it isn't actually likely to have any influence

unless we see some x model agreement and amplitude then I suspect it's irrelevant. 

Yes you'll see I was questioning what impact it could have because of the low amplitude however there is a discrepancy between the forecasts. The MacRitchie one which reduces interference from Kelvin waves etc shows the MJO about to go into phase 6, something the others are less interested in. The trop response of course might not happen or be very muted however it was the close correlation with that research showing up in some of the ops which peaked my interest! Its noticeable that the normal composite doesn't show that strong ridge anomaly in western Russia, but the more targeted one using the La Nina declining did. You of course know where I'm going here but for fear of causing a run on ear muffs, scarves and hats I'll say no more! lol

[nick sussex]

46 minutes ago, Ed Stone said:

I've been wondering again:

Are the teleconnection forecasts separate from the 'ordinary' models or, are they constructed using the very same starting data? If they are related thus, won't they be subject to exactly the same degree of uncertainty? Why would, for instance, a GFS-based MJO forecast be any more (or less) useful than other GFS products?

These are genuine questions, and are not a nit-pick.

With the MJO the main models op and ensemble data is used and then they apply the Wheeler Hendon(2004) to that to give the MJO forecast. Of course if  say for example the GFS data is wrong then the MJO is also likely to be aswell. Its a bit like the chicken and the egg, dodgy chicken dodgy egg! The AO and NAO are again just bi products of the models themselves.

I should add re the MJO the normal dynamical model forecasts can sometimes show an innacurate picture because of interference, that's why we see different versions trying to reduce that interference.

Edited January 7, 2017 by nick sussex

[SMU]

1 hour ago, Ed Stone said:

I've been wondering again:

Are the teleconnection forecasts separate from the 'ordinary' models or, are they constructed using the very same starting data? If they are related thus, won't they be subject to exactly the same degree of uncertainty? Why would, for instance, a GFS-based MJO forecast be any more (or less) useful than other GFS products?

These are genuine questions, and are not a nit-pick.

They are model based poorly quite often- some days the models initialise in a different phase than the previous days 24 hour forecast-

If you think of how many teleconnections there are - at the very least you need to remove the ones that are non effect ones like AO / NAO / PNA etc - these are effects not cause & are just expressions of patterns -

I guess you have the main global ones below - some are stable & some are volatile -

* El nino / La nina ( ENSO ) - stable enough to forecast 

* GWO encompassing AAM & MJO - which is somewhat volatile & difficult to predict - the starting point gives you composites to work with however like MJO the forecast can go one way but the reality is very different

* Strat zonal winds & structure of vortex- starting point V climo norm very usefull for week 1 week 2 forecasts to generate a base map of NH - Interim ERA daya access would be a god send... ( athough merra is similar ) -

-Strat wind undepinned by QBO - no forecasts for this really as its cyclical ( or it was thought to be until 2016 ) but we know the base state-

* Sunspot incidence also enhances net zonal wind -

You will then have perhaps more local ones - or should I say ones that have more regional impacts that as yet probably arent factored into modelling & 'perhaps' some of the reason why the UKs winters may have gone pearshaped

- SAI metric which should support higher heights over Russia

- SSTA atlantic cold anomaly- this will have regional impacts as yet not diagnosed.... also the PDO that everyone used to love will impact regionally

Also all the available forecasts for Teleconnections generally predict where the greatest positive & negative anomalies are going to be - making continental forecasting a bit easier, however UK winters can be influenced by very weak unpronounced high pressures ( infact some of our very best cold weather has come from weak blocking )

This wont get picked up in T/C models or the GSDM referred to earlier which is based around the MJO-

S

in terms of this summer Im going to make my own TC up specific to NW europe & work on that relating to important global teleconnections & regional ones -

Name ?? MODWIN With its own phases...

 

 

 

 

Edited January 7, 2017 by Steve Murr

[Severe Siberian icy blast]

38 minutes ago, bluearmy said:

Careful re the MJO nick

it's a few weeks since it was in any amplitude and I am suspicious that without any clear drivers (strat zonal wind and qbo aside, ) people tend to adopt it as an indicator when it isn't actually likely to have any influence 

unless we see some x model agreement and amplitude then I suspect it's irrelevant.  

This is what I found a bit odd to be honest in matts tweet. I suppose some of it has to be continued marketing for his clients. But considering how low amplitude it's been most of the season and the fact we have had several red herrings on the mjo driving the weather is really think he could be setting himself up for egg on face here because iv began to doubt how much impact the mjo has on our weather especially when we have other stronger factors to consider. More especially in the low amp like we have. Granted if we see a upkick into a higher amplitude I would put more weight on it. Anyway this wild card of a winter at least is bringing surprises this year and in sure will continue to do so. I'm beginning to think we may eventually have a true scandi high during last wk of Jan into Feb, especially if we can keep the vortex over Greenland area, if it's tracks toward the Canadian artic it will open all sorts of doors but who knows what wil happen in a week let alone a month!

[nick sussex]

Just now, Severe Siberian icy blast said:

This is what I found a bit odd to be honest in matts tweet. I suppose some of it has to be continued marketing for his clients. But considering how low amplitude it's been most of the season and the fact we have had several red herrings on the mjo driving the weather is really think he could be setting himself up for egg on face here because iv began to doubt how much impact the mjo has on our weather especially when we have other stronger factors to consider. More especially in the low amp like we have. Granted if we see a upkick into a higher amplitude I would put more weight on it. Anyway this wild card of a winter at least is bringing surprises this year and in sure will continue to do so. I'm beginning to think we may eventually have a true scandi high during last wk of Jan into Feb, especially if we can keep the vortex over Greenland area, if it's tracks toward the Canadian artic it will open all sorts of doors but who knows what wil happen in a week let alone a month!

I see what you mean, the MJO seems to have had a lot of attention. A bit like one of those Z list celebs who haven't achieved very much but yet continue to appear all over the papers! The reason I was a bit more interested today than for a while was the forecast of it avoiding the COD and getting into phase 6. And then adding in the slightly different trop impact because of La Nina declining and then looking at the ECM got me thinking. Anyway the GFS is coming out soon, hopefully it can follow the research! lol

[Catacol]

5 minutes ago, nick sussex said:

With the MJO the main models op and ensemble data is used and then they apply the Wheeler Hendon(2004) to that to give the MJO forecast. Of course if  say for example the GFS data is wrong then the MJO is also likely to be aswell. Its a bit like the chicken and the egg, dodgy chicken dodgy egg! The AO and NAO are again just bi products of the models themselves.

I should add re the MJO the normal dynamical model forecasts can sometimes show an innacurate picture because of interference, that's why we see different versions trying to reduce that interference.

This season I have tended to use the Ventrice plots becasue the Wheeler/Hendon diagrammes appear frequently to be both incorrect and in conflict when one looks across the different models. Not that Ventrice is necessarily correct BUT what his graphs do provide is data that can be interpreted.

Looking at the current plot today it is easy to see why there might be some model confusion regarding MJO phase, and therefore confusion as to any particular MJO forcing going forward

That top diagramme is a right mess - positive and negative anomalies on top of each other and to be honest to my eye that isnt a coherent signal. We have seemingly been waiting all winter for such coherence. What the bottom chart shows - a prediction chart of course - is a return to the suggestion of movement into phase 7/8 - something else we have been waiting to impact on our sector of the globe seemingly all season long!! The Wheeler Hendon sub-seasonal bias shows that we ought to be moving towards 7/8.... but progression has been painfully slow all winter and really I'm still not 100% sure whether the phase 7/8 progression with any decent amplification is about to happen or not. We may sit in the doldrums for longer still.

January composites for phase 7/8 are decent for winter here. 6 is a bit meh..... but 7 is good

and 8 not too bad. 

 

Roll forward to February and they remain good for 7/8

 

But - all of these composites assume an amplitude of greater than 1. Therefore while we remain in the Wheeler/Hendon Circle of Death the forcing is slight. And that means we are left looking for vortex splitting or stretching... and it isnt on the horizon.

So 2 paths forward to my eye - either the MJO continues to stagnate and this winter is entered into the annals of weather history as dry, occasionally frosty but fundamentally rather boring throughout... or we get the MJO injection of amplification and possibly we can pull a cold spell of some description out of the bag. I cant see a vortex led cold spell happening now.

Is this an optimistic or pessimistic post? Not sure really. I've sat waiting and expecting a degree of MJO led amplification to occur to maximise the benefits of the early winter signals that were so good. It may still indeed happen. Phase 7/8 to my eye is the only way the MJO can progress from here if it does indeed progress. But the Pacific in general looks so quiet I'm starting to lose faith that it will happen. Noticeable that the technical experts on this forum and on twitter have been generally muted in their posts regarding anything dramatic in terms of torques, AAM spikes or vortex disruption. 

All we can do is wait. There's a lot of winter still left. Fingers crossed.

[Chris.R]

 I remember Ian F quite recently saying that the Meto  seasonal team considered the MJO was likely to have no impact for the time being. I seem to recall him strongly dismissing  any effect it might have due to its weak amplitude. Obviously this view may have changed now. 

Edited January 7, 2017 by Chris.R

[Mucka]

Well teleconnections aside (and always a fascinating discussion) I'm surprised the ECM mid lat blocking is being written off by some.

At face value it seems fairly unlikely given other output but it is seemingly well supported within ECM suite

A clear split develops, but noticeable that colder ones have very cold night time temps so, without seeing the postage stamps, I would infer from that we are under the influence of high pressure rather than a trough.

Either way, we are on track for the first real prospect of seeing snow fall at least.

Edited January 7, 2017 by Mucka

[bluearmy]

3 minutes ago, Mucka said:

Well teleconnections aside (and always a fascinating discussion) I'm surprised the ECM mid lat blocking is being written off by some.

At face value it seems fairly unlikely given other output but it is seemingly well supported within ECM suite

A clear split develops, but noticeable that colder ones have very cold night time temps so, without seeing the postage stamps, I would infer from that we are under the influence of high pressure rather than a trough.

Either way, we are on track for the first real prospect of seeing snow fall at least.

It's the favoured route forwards based on the last two eps suites mucka but as I mused this morning, with the gefs and gems not really in agreement, I remain wary about taking too much from the eps  

[Cheshire Freeze]

1 hour ago, Gustywind said:

Sorry Crewe yes your right, 2009-10 was the El Niño year.

It's OK, I was getting a bit confused myself 

[Mucka]

5 minutes ago, bluearmy said:

It's the favoured route forwards based on the last two eps suites mucka but as I mused this morning, with the gefs and gems not really in agreement, I remain wary about taking too much from the eps  

Oh absolutely, very wary myself and wouldn't call it either way, I was just a little surprised by the strength of some the statements that seemed to rather discount it.

 

Edited January 7, 2017 by Mucka

[SMU]

Good start to the 12z losing the kinky low over SW greenland @ 96 as this pesky system encouraged heights to lift ahead of it & a flattening of the flow over the UK...

upstream looks good as well-

[feb1991blizzard]

3 minutes ago, Steve Murr said:

Good start to the 12z losing the kinky low over SW greenland @ 96 as this pesky system encouraged heights to lift ahead of it & a flattening of the flow over the UK...

upstream looks good as well-

Are you talking about that shortwave that has been on almost every GFS for a few days but on hardly any other run?   I liked that as it could have given some more prolonged outbreaks of snow as opposed to just showers, plus there tends to be more margin for error with uppers with those systems, that was the only chance of seeing decent white stuff for the south, admittedly the last few runs it wasn't digging as far south anyway though to be fair.

[Kieran]

Snow again shown for Thursday. I wonder if it will be as widespread as the 12z GFS is suggesting:

Edited January 7, 2017 by Kieran

[SMU]

12 minutes ago, feb1991blizzard said:

Are you talking about that shortwave that has been on almost every GFS for a few days but on hardly any other run?   I liked that as it could have given some more prolonged outbreaks of snow as opposed to just showers, plus there tends to be more margin for error with uppers with those systems, that was the only chance of seeing decent white stuff for the south, admittedly the last few runs it wasn't digging as far south anyway though to be fair.

Yes - & in reality I think the GFS would have been overdoing the snow as that s/wave made the flow at best North westerly- now at 132 without it ( but with other developments within the flow in terms of troughs ) the flow is now NNW..

before & after

 

[feb1991blizzard]

1 minute ago, Steve Murr said:

Yes - & in reality I think the GFS would have been overdoing the snow as that s/wave made the flow at best North westerly- now at 132 without it ( but with other developments within the flow in terms of troughs ) the flow is now NNW..

before & after

 

To be fair, yes it has already downgraded anyway, some of the runs a few days ago though would have given a right dumping, potentially anywhere, depending on track, not sure how much PPN there will be around now, this run does look slightly better regarding longjevity / reload potential.

[SMU]

Polar low at 156 trying to nudge towards scotland

[Captain Shortwave]

Good agreement on conditions turning colder everywhere by Thursday, the UKMO looks like following its previous output. Day 5/6

   

The shallow wave south of Iceland will allow the Scandi trough to dig further south to affect most of Europe and will usher away the higher heights like previous runs. Blizzard conditions look likely over the higher routes in the north but snow could fall anywhere really. The UKMO shows a shallow system over Iceland at day 6 which should take a potentially more southerly track.

GFS Day 5/6

   

Quite similar and some unusually cold air is pushing down from the north west, 850s of -10C across Scotland. Can we keep the cold air entrenched over us or will the jet running over the high push the ridge back into southern Europe. 

Edited January 7, 2017 by Captain Shortwave

[booferking]

Uk model looks good for more a prolonged cold spell after 144hr.

Edited January 7, 2017 by booferking

[chris55]

Im liking the "wedge" on the 12!!

Overall a good run so far, slider territory beging suggested

[Geordiesnow]

3 minutes ago, Steve Murr said:

Yes - & in reality I think the GFS would have been overdoing the snow as that s/wave made the flow at best North westerly- now at 132 without it ( but with other developments within the flow in terms of troughs ) the flow is now NNW..

before & after

 

Without the shortwave, not only we get a cleaner flow, it also allows any mild sectors to be very limited to no mild sectors at all. I guess shortwaves can be looked at whether your glass is half empty or not, yes they will bring more cloud and PPN which if the air is cold enough could bring more persistant snow but on the other hand, it reduces the convective potential and especially with NW'lies, your more likely to get milder sectors appearing which means instead of heavy wintry(snow) showers from a strong NW'ly, you get cloudy grey boring skies with outbreaks of rain(in most cases).

UKMO is a peach of a run btw, low thicknesses, deep convective potential and with the kink in those isobars, a chance of something more persistant. I must admit, I'm surprised the models are at the moment seemingly going for a cleaner flow but I am aware that this can change fairly quickly. It also has more amplification earlier on in the run which does help things for our shores.

[Mucka]

1 minute ago, Steve Murr said:

Polar low at 156 trying to nudge towards scotland

@156, it's nailed on Steve.

I'll take this run and bank it though thank you very much.

 

[radiohead]

Low pressure sneaks in from the Atlantic at T168 bringing a mild sector and rain. Snow on northern edge. 

[feb1991blizzard]

3 minutes ago, Mucka said:

@156, it's nailed on Steve.

I'll take this run and bank it though thank you very much.

 

Its showing on the UKMO as well.