Model output discussion - mid-winter

[Paul_1978]

4 minutes ago, Draig Goch said:

Early indications show yet another mild start to February, what some people living on the coasts in the south call their 'snowy month', when the sea temperatures reach their coldest and the sun is not too strong. Let's hope it will be a cold, snowy month this year instead of a mild stormy one. There is talk of an SSW by the end of January so there's hope! 

Even that's gone quiet in the last few days.... Unless I've missed something.

[bluearmy]

10 minutes ago, Paul_1978 said:

Even that's gone quiet in the last few days.... Unless I've missed something.

You haven’t 

[weirpig]

In regards to the low  Wednesday Night  into Thursday  the Arpege  deepens the low a tad  and draws the low slightly more north  hence winds are slightly higher and slightly more north  Ps  100k  really have you seen were i live.

[Man With Beard]

ECM ensemble clusters a little less keen on the end of month NE ridge this morning but it's still very clearly on option. As are mild westerlies.

[mountain shadow]

14 minutes ago, Man With Beard said:

ECM ensemble clusters a little less keen on the end of month NE ridge this morning but it's still very clearly on option. As are mild westerlies.

I think we know what will win that battle unless we can get the MJO into 7 or 8.

[karyo]

1 minute ago, mountain shadow said:

I think we know what will win that battle unless we can get the MJO into 7 or 8.

After phase 4 it looks like entering the circle of death.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml

[MP-R]

Just out of interest, what causes the MJO to get so far then just go back to the start of the cycle? Is it affected by the monumental pain that is La Niña or the other way around?

[mountain shadow]

1 minute ago, karyo said:

After phase 4 it looks like entering the circle of death.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml

I know, but these MJO forecast plots haven't been great this Winter due to the nina complications. The GWO is a better bet and GP seemed a bit more confident in that regards.

Maybe Singularity or Bluearmy can give us their musings on where things are looking in that regards.

[nick sussex]

It*s remarkable for all the wrong reasons just how much the upstream pattern has flattened out.

Even outputs at the normally reliable T72 and T96hrs haven't lasted and the trend shows no sign of stopping.

Barring a chance of some possible snow as some shortwave energy disrupts se around day 4 the outputs are sinking without trace.

A lack of trough disruption and poor phasing with low heights to the ne finish off hopes with just too much energy upstream.

Although some ECM ensembles are better than the op the latter with its higher resolution should be better at handling the pattern at short range.

We're now left to wait for another opportunity but certainly after the recent sorry episode best view any more amplified upstream solutions  with a huge degree of scepticism.

The recent ones hit the buffers quickly and the ECM once again over amplifying upstream.

 

 

[karyo]

10 minutes ago, nick sussex said:

It*s remarkable for all the wrong reasons just how much the upstream pattern has flattened out.

Even outputs at the normally reliable T72 and T96hrs haven't lasted and the trend shows no sign of stopping.

Barring a chance of some possible snow as some shortwave energy disrupts se around day 4 the outputs are sinking without trace.

A lack of trough disruption and poor phasing with low heights to the ne finish off hopes with just too much energy upstream.

Although some ECM ensembles are better than the op the latter with its higher resolution should be better at handling the pattern at short range.

We're now left to wait for another opportunity but certainly after the recent sorry episode best view any more amplified upstream solutions  with a huge degree of scepticism.

The recent ones hit the buffers quickly and the ECM once again over amplifying upstream.

 

 

Yes Nick, it is very disappointing to think that up to a few days ago the models were showing a ridge developing in the Atlantic towards the end of this week, with a northerly and then a possible pressure rise to the northeast. Instead we are getting the horrid Azores High extending its influence north and east and a spell of southwesterlies next week. My only solace is that I will not miss anything worthwhile when I am away next week. 

[swebby]

32 minutes ago, karyo said:

After phase 4 it looks like entering the circle of death.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml

I rather like the BOMM output - think you could say it is hedging its bets with what phase the mjo will be in....?

Edited January 17, 2018 by swebby
typo - hedging!

[nick sussex]

Just now, karyo said:

Yes Nick, it is very disappointing to think that up to a few days ago the models were showing a ridge developing in the Atlantic towards the end of this week, with a northerly and then a possible pressure rise to the northeast. Instead we are getting the horrid Azores High extending its influence north and east and a spell of southwesterlies next week. My only solace is that I will not miss anything worthwhile when I am away next week. 

Yes I agree its another tragic episode in the many that befall the UK when any cold synoptics manage to break through into the modelling.

The ECM particularly was more interested but even some of the other outputs still promised more than whats likely to arrive.

Although some parts of the UK have seen some snow for many its been another useless winter with expectations so low that a centimetre of slush is greeted as the next 62/63!

Of course in the UK you have to have lowish expectations given its difficult to get the right synoptics but really it's not like a Mission to Mars.

It should still be possible to get a decent spell with snow and not slush.

We now have to follow the MJO and urge it onto the more favourable phases and hope this can deliver.

Anyway I'm a bit grumpy as you can tell!

 

[Weathizard]

Why is nobody in here talking about the south this morning? I need my daily dose of southern bias

 

Had a quick browse through the models, the lack of posts says it all really... pretty much nothing to talk about, let's just hope it will be dry.

 

GFS 0z ensembles show not too much interest really, there's a cool down out to day 8/9 but nothing to write home about, even longer term there's really no sustained cold amongst any of the ensemble suite.   

[Methuselah]

2 minutes ago, swebby said:

I rather like the BOMM output - think you could say it is edging its bets with what phase the mjo will be in....?

Interesting, Swebby, and you've just reminded me of a question I have: do the models ever have the faintest idea where the MJO is, at any given time? Or do the models do their workings totally independently of teleconnection forecasts?

[mb018538]

I think everyone is feeling deflated (hence the lack of posts) - the SSW shown was overblown, the blocked scenarios are slowly disappearing, and we all know what we're going to be left with.....the same as always. If this winter has told people anything, it's that changes have happened at a rapid pace, and from nowhere at times. Still another 6 weeks to get something decent yet, plenty of time!

[ACCOUNT DELETED]

IMO, not too bad model runs this morning, we have a nice ridge bringing much milder weather across the south by Monday on both UKMO & GFS 6z meanwhile, the ECM builds an even stronger area of high pressure by next weekend with 1030mb approaching the south coast of England. 

[frosty ground]

1 minute ago, Ed Stone said:

Interesting, Swebby, and you've just reminded me of a question I have: do the models ever have the faintest idea where the MJO is, at any given time? Or do the models do their workings totally independently of teleconnection forecasts?

I thought all those MJO forecasts where generated from the models.

To me it looks like people are using MJO forecast generated by models as a signal for future development except they call it teleconnetics.

When the models looked good for next week and beyond the MJO got trotted out that supported the current  output, which to me is basically reading the models but in a different way, then when the models changed we where told that maybe the models are not reading the MJO signal right, except the MJO signal was derived from previous output therefore the statement should have been the Models misread the MJO originally.

[nick sussex]

In terms of the MJO the weakening is in relation to interference from a Rossby wave.

That's mentioned here in yesterdays Tropics update:

During the next two weeks, the current MJO signal is forecast to continue its eastward propagation. La Nina, the low frequency state, is expected to remain entrenched in the central and eastern Pacific. For Week-1, the RMM-index shows movement into Phase 4 for the MJO, moving the enhanced convective region over the Maritime Continent. The forecast shows deterioration in the amplitude of the signal over the next week and into the beginning of Week-2. This is most likely due to expected Rossby wave activity in the Pacific. Model guidance reflects this solution, though the GFS model forecasts a larger decay to the signal than the European model. Despite the weakening, eastward propagation into Phase 5 is expected for the MJO signal. The convective envelope of the MJO is likely to destructively interfere with the base state as it moves into the western Pacific. This is reflected in the shift of forecasted precipitation patterns for the Pacific from Week-1 to Week2.
 

[karyo]

23 minutes ago, swebby said:

I rather like the BOMM output - think you could say it is edging its bets with what phase the mjo will be in....?

I am not the most knowledgeable on the MJO but i think that it is less likely to reach phases 7 and 8 if it is weak before hand. Especially as it has to fight the La Nina easterlies that are dominating further east. And in this case, the MJO is not just weak but dead. I could be wrong though. Edit: just read Nick's explanation on the MJO weakening.

Hopefully, the GWO is more important as other members have said but I have no idea how is that progressing. Anybody can update us please?

Edited January 17, 2018 by karyo

[frosty ground]

19 minutes ago, nick sussex said:

In terms of the MJO the weakening is in relation to interference from a Rossby wave.

That's mentioned here in yesterdays Tropics update:

During the next two weeks, the current MJO signal is forecast to continue its eastward propagation. La Nina, the low frequency state, is expected to remain entrenched in the central and eastern Pacific. For Week-1, the RMM-index shows movement into Phase 4 for the MJO, moving the enhanced convective region over the Maritime Continent. The forecast shows deterioration in the amplitude of the signal over the next week and into the beginning of Week-2. This is most likely due to expected Rossby wave activity in the Pacific. Model guidance reflects this solution, though the GFS model forecasts a larger decay to the signal than the European model. Despite the weakening, eastward propagation into Phase 5 is expected for the MJO signal. The convective envelope of the MJO is likely to destructively interfere with the base state as it moves into the western Pacific. This is reflected in the shift of forecasted precipitation patterns for the Pacific from Week-1 to Week2.
 

So the Models got it wrong originally hence why forecasts based upon MJO was also wrong.

[nobble]

1 hour ago, shaky said:

gona have the same punch as it does in december or january as sun will be higher up in the sky!!especially mid to late feb!!06z continues the slide further!!

Late March 2013 snow was on the ground for over 3 weeks!!!!

[Tamara]

The long italicised explanatory post excerpt below from 2 January is just one part of an on-going seasonal continuity of theme intended from my posts in the MOD thread, which have been discussing both the obstacles and potential upsides to a cold pattern c/o Scandinavian heights - as the middle, and now latter parts of the winter come more into focus 

There have subsequently been several more updates to this particular post which have increasingly focussed on the downsides initially raised due to collapsing atmospheric angular momentum - but in my opinion reflect precisely what we see being played out in NWP at the moment and has been increasingly anticipated over the last 10 days by the evidence of GSDM (Global Synoptic Dynamical Model) data. It sounds a bit flouncy and pretentious in its title, but its a highly valuable concept mechanism (as long as it is approached with a mind to suspend biased weather preference application).

The main emphasis ever since this post has been questioning how much the Azores high would play its part as one of the sub tropical footprints of the mid latitude signature pattern which is associated with La Nina.

I think its important to re-post this particular post in its length to try and give reminder insight into why NWP has continued playing out some 'jam tomorrow' scenarios and  blowing cold on them - with any such upside potential being very much dependent upon atmospheric angular momentum achieving at least parity, or, better still, elevation relative to the base Nina state as it did in December:

 

> But the implications of forward moving momentum in the tropics mean that processes start happening which in time propagate to the extra tropics - and these become vital to how the longer term plays out.

One of those starting processes that accompanies an upward shift in angular momentum tendency is a corresponding upward shift in frictional torque tendency in the tropics  - and which has consequences over a considerable period of time in terms of what it can do to the longwave synoptic pattern in the extra tropics mid and higher latitudes.

What is this frictional torque and what exactly is implied by it?     Atmospheric angular momentum in simple terms refers to the amount of turning force in the Jetstream.  The balance (or budget) of AAM is determined in very simplest terms by the net amount of both easterly and westerly wind-flows that are present at any given time in the atmospheric circulation.

If there is excess easterly wind inertia in the global jetflows, at any given time (c/o La Nina trade winds propagating to the extra tropics), then this has the effect of lowering angular momentum tendency and producing a -ve frictional torque at the surface. The frictional torque refers to a pressure differential created from the point of where easterly winds are added and westerly inertia is scrubbed from the atmospheric circulation. Divergence across the tropics, where the trades are found leads to the spin-up of sub tropical anticyclones which align from west to east circum-globally.

One of those sub tropical ridges relevant in our sector is obviously the Azores High. This has, as expected, been a prominent feature of this winter so far and has meant that cold air incursions have been based on mid latitude amplifications.

We see this coming week how the Azores High plays it part as an amplified mid latitude feature once again in introducing another cold incursion to the UK. The longevity of this phase comes down to what happens in the tropics over the coming medium term period, and pertinent to the discussion in this post, how much frictional (ocean) surface torques and extra tropical (mountain torque)  mechanisms can be altered (upwards) by increasing angular momentum tendency.

The consequence of a sufficiently robust eastward moving tropical signal is that the subsequent eddies in the windflows (produced by the significant alignment of tropical thunderstorm activity on a macro scale) tend to flux poleward with time. This means that an amplification mechanism is triggered which follows the principles of a stone thrown into a pond, and the ripples spread out according to the size of the stone and also how far away from starting base the stone is thrown,

So  poleward motion of flux, +ve frictional torque tendency in the tropics can lead to +ve mountain torque tendency in the extra tropics according to the size of the initial 'splash'.  The size of the splash of course relates to the size of the tropical forcing advancing eastwards through the tropics, and if there are differences between models as to the strength and longevity of that signal, then the consequent downstream amplification signal is going to vary from one model to another

What of the implications of +ve frictional torque in the tropics and +ve EAMT in the extra tropics?

The shorter term product of a good amplification signal is of course the ability of the initial amplified Atlantic ridge to extend into Scandinavia, with a split jet that enables 'appropriate' jet flow over and under the ridge to support it, and enable the 'horseshoe' configurative return of the jet back SW'wards to assist cold air advection this way.

But as suggested in the stratosphere thread by chiono, an H500 pattern being one of Scandinavian heights and upstream EPO ridge is one that aligns itself suitably to externally pressurise the vortex. This has, as stated, extended term implications for potential SSW much later in the month/ early Feb.

But also there is the poleward effects of +ve torque mechanisms to perturb the vortex internally as part of a tropospheric tropical>extra tropical mid/higher latitude>stratosphere disrupting mechanism.   The wavelength/timeline of a programme of +ve frictional torques implies a dismantling of the sub tropical ridges through westerly winds added through the tropics by eastward moving convection to scrub the La Nina easterly trades from the atmosphere that underpin those ridges.

That is in addition to lagged effects of extra tropical +ve mountain torque effects that deflect warm air advection into cold vortex segments

If a programme of higher heights and a -ve AO profile is to be created by a combination of poleward fluxing +AAM anomalies as well as a wave 2 activity response from a height profile each side of the pole, then the domino to fall is the weakening of the Azores High to facilitate undercut and remove the +NAO profile. 

It is this that restricts us to what we see this weekend that depends upon maximum amplification of the Mid Atlantic ridge to achieve a Scandinavian High, to one where the Pacific forcing pattern, that is a-typical of La Nina, can override the base state forcing and engineer maximum downstream capital c/o split-flow with enough energy going into the southern stream to undercut heights to the N and NE. This happening in the absence of a sub tropical ridge, that is both a natural feature of a La Nina pattern, but is also counter-intuitive to developing a -NAO to assist backing cold air west c/o of a -AO profile

I suspect however the on-going shorter term Atlantic ridge>Scandinavian ridge plays out vs Canadian vortex, this will be a cat and mouse theme to dominate January and we will be relying on the Azores High playing ball according to (and dependant on) the relative level of atmospheric angular momentum - and to the extent the Nina trades are mitigated to allow undercutting energy. The undercut has remained elusive this winter so far in the midst of quite an amplified mid latitude pattern

Can the extra mile be achieved?

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

Allora... e poi?

The whole post is pertinent to the here and now - but special emphasis given to the bolded parts

The answer thus far has been that the extra mile has been/is struggling against another substantial programme of easterly trade winds that have depressed angular momentum to a level that would reflect a robust La Nina base state if it was to be sustained to meet official criteria. That particular scenario certainly seems unlikely looking forward, but nevertheless it does represent a considerable challenge to any +AAM poleward anomalies c/o tropical convection heading eastwards during the medium term at the very least.

Any NWP extended ensemble signal showing a height anomaly to the NE has been/is based upon what looks at the moment like something of a leap of faith assumption that MJO tropical forcing successfully negotiates the trade wind wall of easterlies in the Pacific, overcoming in the process a substantial -3 low angular momentum standard deviation from parity, (reflective of the easterly trades swamping the atmosphere) and then manages to trigger a downstream signal for that greater amplification in the Atlantic and European sector.

My take remains exactly the same as of late that the above described atmospheric hoop jumping is a big ask based on simple AAM budget maths. NWP is now awake to those maths.

 Until or if those easterly trades relent some, and change the complexion of the budget maths to allow greater +AAM anomalies c/o MJO tropical convection to scrub out some of those surplus easterlies (to permit greater downstream amplification), the cat is very much in the ascendency of the mouse at the moment and it increasingly becomes a case of whether the mouse can roar during February. Which to those more especially further south seeking some seasonal whiteness implies more 'jam tomorrow' - and assessing that comes against a spectre of ever greater doubting questions vs also the seasonal wavelengths ever shortening.

But whichever way one slices it, that would all be part of any future rolling programme of seasonal analysis.

Andiamo - attraversiamo,... Ciao

Edited January 17, 2018 by Tamara

[ACCOUNT DELETED]

7 minutes ago, Dafydd Tomos said:

Indeed but we need to see that persistent very cold air move out of America than the jet can relax in intensity as it is not helping us in the south one bit. As you say though, February but even March has the highest chance of snow settling on the coast. Still about 9 weeks to turn this disappointing Winter around for us

CFS looks poor but suggests March will be our best chance, February looks mild again but thankfully April looks about average or slightly above this year! 

[joggs]

4 minutes ago, Draig Goch said:

CFS looks poor but suggests March will be our best chance, February looks mild again but thankfully April looks about average or slightly above this year! 

If all else fails roll out the faithful  cfs lol.

[Man With Beard]

8 minutes ago, Tamara said:

Any NWP extended ensemble signal showing a height anomaly to the NE has been/is based upon what looks at the moment like something of a leap of faith assumption that MJO tropical forcing successfully negotiates the trade wind wall of easterlies in the Pacific, overcoming in the process a substantial -3 low angular momentum standard deviation from parity, (reflective of the easterly trades swamping the atmosphere) and then manages to trigger a downstream signal for that greater amplification in the Atlantic and European sector.

My take remains exactly the same as of late that the above described atmospheric hoop jumping is a big ask based on simple AAM budget maths. NWP is now awake to those maths.

 Until or if those easterly trades relent some, and change the complexion of the budget maths to allow greater +AAM anomalies c/o MJO tropical convection to scrub out some of those surplus easterlies (to permit greater downstream amplification), the cat is very much in the ascendency of the mouse at the moment and it increasingly becomes a case of whether the mouse can roar during February. Which to those more especially further south seeking some seasonal whiteness implies more 'jam tomorrow' - and assessing that comes against a spectre of ever greater doubting questions vs also the seasonal wavelengths ever shortening.

 

Thanks as ever Tamara.

Sorry to quote just this part of your post but I think it is quite relevant to the ECM clusters that I post - so I'm gathering that the NE height rises suggested for the month end are dependent upon a couple of background signals which, at the moment, are uncertain and perhaps over-optimistic.

@iapennell - it's getting very close to your timescale for an end of January easterly - I would be very interested in your take on this!