Model output discussion - mid-winter

[shaky]

15 minutes ago, ghoneym said:

Screenshots of a weather update service we use at work. Might be useful for close range detail. I think from what I read they draw their own charts based from data from ECM / GFS / HIRLAM. We get updates every 4 hours or so, I can update when I can on here or maybe on the short range thread?

Brilliant mate please do!!carinthian does the same thing aswell!!we just waiting on his update for today!more importantly keep a good eye on that horrible shortwave coming out of the eastern united states!!

[blizzard81]

5 minutes ago, Broadmayne blizzard said:

Without wishing to offend in anyway there are an awful lot of ridiculous winter's over type post in here this morning. Anyone thinking any model has got anything on the nail beyond 120/144 at the moment is living in FI themselves. 

We all know that once a major back track occurs it hardly ever reverts back. We are more wise to these things than we used to be, that's all. January's have become a total borefest. 

[comet]

Very disappointing model viewing it has to be said. It certainly makes you feel that this model watching is a complete waste of time, commentating on charts at plus t168 then everything implodes and charts at t96 etc can not be trusted. Not trying to have a dig but even positive posts from those that follow the teleconnects more closely look to have come unstuck. I have never been a fan of the NOAA updates as they never seem to offer much assistance and sure enough the last update I read on here mentioned a more amplified upstream pattern over the states which would have benefited us yet the reverse now seems to be the case.

Warming is still being advertised in the gfs strat charts but this has been somewhat delayed and watered down from what the charts were showing three or 4 days ago although it does look as though there is now more of a response height wise with the vortices becoming more stretched again at 10 and 30mb. If this trend continues then a split may well be evident in early February.

Some of the more favoured areas likely to see some snow (perhaps significant) this week while for most the chance of some wintry showers with maybe a temporarily covering.

Edited January 14, 2018 by comet

[blizzard81]

2 minutes ago, markw2680 said:

Couldn’t have put it better myself tbh, expect more changes in the next couple of days, it’s not nailed yet by a long chalk 

If I had a pound for everytime I heard that, I wouldn't need to put the lottery on

[SLEETY]

Problem is whenever the models trend mild in fl from a cold outlook before they very rarely trend back to a cold outlook.Seen it so many times ,since I.ve been watching the models online for years and years,so utterly predictable 

Writing was on the wall after yesterday’s 12 I said then the ukmo  t144 was going to flatten,it’s the most consistent model I think at that timeframe.

NVM always end of jan and whole of feb for a repeat of 1947;1986 .Get those sledges ready.

[Dennis]

i still believe better days - its disappointing till now till models see whats realy to be happen

[bluearmy]

Without illustrating specific gefs members (which isn’t advisable as it skews your expectations noting the cold members and ignoring the non cold ones), the suite does illustrate that amplification is more than feasible in week 2 and could lead absolutely anywhere 

[blizzard81]

1 minute ago, bluearmy said:

Without illustrating specific gefs members (which isn’t advisable as it skews your expectations noting the cold members and ignoring the non cold ones), the suite does illustrate that amplification is more than feasible in week 2 and could lead absolutely anywhere 

Nice to hear some positivity but always seems to be week 2. Is it back end of week 2 by any chance? Lol

[Chesil View]

Just now, bluearmy said:

Without illustrating specific gefs members (which isn’t advisable as it skews your expectations noting the cold members and ignoring the non cold ones), the suite does illustrate that amplification is more than feasible in week 2 and could lead absolutely anywhere 

Quite so Blue.

[Catacol]

Time for a post. A lot happening in background forcings at the moment. Remember the elastic band?

So - frictionals look to have turned to an upwards movement (though a bit slower than expected if I'm honest) with graph now heading back up

and mountain torque also on the up. Andean South American torque in the wrong hemisphere for us, but note East Asian and Rocky Mts trending upwards once again leading to the global spike

MJO moving through the Indian Ocean and still forecast to cross the maritimes into the western pacific with, to my eye, amplitude sufficient to impact on NH circulation

 

All of this serving to increase angular momentum to a position where it can begin to impact on high lat circulation via poleward wave propagation. Note the steep spike here - though my previous post of "how high" can it go and for how long will it be sustained remains extremely salient

 

All this pretty much as expected with timescales remaining relevant... so given lag time we are experiencing a key resultant response not this week but next.

However absolutely no getting away from the fact that ensemble data today has shunted the wave pattern a good bit, and ECM ensemble runs for the start of week beginning 22 Jan are not as pretty as they could be or were a day or so ago. Note the deep dig of the trough into Europe as expected, but it is currently forecast to be too far east to assist sufficiently in supporting height rises over Scandy. 

In simple terms the horseshoe of heights to the north remains but with more azores high influence and flat Nina forcing in the atlantic still present.

I'd emphasise the word "currently" because this is an evolving situation. ECM operational chart for 192 this morning to me reflects a whole basket of uncertainty - its a curious chart prior to NWP turning on the atlantic "tap" once again afterwards.... but it says to me that week beginning 22 Jan remains far from resolved.

Without doubt pacific forcings are impacting on NWP at this point... and the question "how high" can AAM ping back and how sustained can ongoing MJO activity be in the face of the same cold Nina waters that blocked it in Xmas week retains key significance. NWP is simply a reflection of these equatorial and ocean/atmospheric battles that are ongoing.

And what if it goes wrong - and Nina wins out again? We would move back into another waiting game of cycles. We would need to wait another fortnight for frictional/mountain torque activity to come back around... and for MJO (hopefully) to reach the ideal 7/8 orbit in early February. Note quite interesting stratospheric developments as signposted by far more knowledgeable people than me with the Jan 23rd chart showing a decent wave 2 signal for vortex attack.. and lag effects of this would also point to early/mid February impact. 

And so this winter keeps giving and giving in terms of interest. So far no snow IMBY but plenty of knife edge interest on a week by week basis. I hope readers of this thread can keep perspective going forward - we have been close to some excellent synoptics this season so far, and close enough for many regions to see some decent if rather transient snowfall. High ground to the north has been pasted consistently and Scotland has had a "proper" winter for sure. This is already better than any of the last 4 winters and we still have plenty of interest on the horizon. Even if southern England ends the season without a winter wonderland experience it will have been a fine run thing... and as we head into the solar minimum, forecast to bottom out in Oct 2019, we can expect winters more conducive to less atlantic impact over the next few years. Scant compensation for those wanting "snow tomorrow" I suppose... but for those who acknowledge the reality of our atlantic climate and infrequent brush with very cold airstreams it is actually something to look forward to!

Anyway - all eyes on the pacific surge and MJO battle. Model output will reflect how these drivers evolve. Cold zonality this week, and then next week still up for grabs I think.

 

Edited January 14, 2018 by Catacol

[Chris101]

My biggest worry over the last few days has not been the modelling of the SW as this was always to far ahead to put much into.

I've been consistently watching the Scandi/russian heights to our N and E.

In the middle of the week these heights were playing a big part at blocking the PV from moving to much to our East and its strength was forcing things in a much better SE direction to give us much lower heights over Europe.

Run by run up to now the blocks hold on the PV has become weaker and we see it heading in the wrong direction.

[snowice]

17 minutes ago, comet said:

Very disappointing model viewing it has to be said. It certainly makes you feel that this model watching is a complete waste of time, commentating on charts at plus t168 then everything implodes and charts at t96 etc can not be trusted. Not trying to have a dig but even positive posts from those that follow the teleconnects more closely look to have come unstuck. I have never been a fan of the NOAA updates as they never seem to offer much assistance and sure enough the last update I read on here mentioned a more amplified upstream pattern over the states which would have benefited us yet the reverse now seems to be the case.

Warming is still being advertised in the gfs strat charts but this has been somewhat delayed and watered down from what the charts were showing three or 4 days ago although it does look as though there is now more of a response height wise with the vortices becoming more stretched again at 10 and 30mb. If this trend continues then a split may well be evident in early February.

Some of the more favoured areas likely to see some snow (perhaps significant) this week while for most the chance of some wintry showers with maybe a temporarily covering.

Yes but we all model watch because we love it.! Kills the  long winter nights,  won't be long for the next chase, newer members feel the pain more. Loads of wintry weeather in the short term let's see what the 12z bring

Edited January 14, 2018 by snowice

[Blizzardof82]

Quote

 

My view FWIW is the models have not got this nailed past 96hrs, I work on the theory of twitter tweets, when lots of meteorologists who  I follow do not tweet its they are unsure of upcoming pattern. My twitter feed has been quiet for days from the Pros which says it all, I personally am still looking north/northeast for height rises.

[Tamara]

On ‎12‎/‎01‎/‎2018 at 17:00, Tamara said:

 

The next part of that analysis, based on evolved evidence of recent days is that tropical/extra tropical interaction is not necessarily going to be as straightforward as many might prefer, at least as I see it, in terms of bringing the anticipated amplification signal downstream as fleshed out in that last post based on 'upside potential'.

This post, especially in light of recent developments, emphasises downside - and in the absence of any other analysis on here that appears to do so :

A significant swathe of easterly trades have scrubbed all 'a-typical' La Nina signals of early winter from the atmospheric circulation. As a consequence total global angular momentum has plunged to levels last seen before the autumn rally which began with the amplitude MJO wave in October - and which imprinted the extra tropical pattern with an increasingly amplified La Nina based mid latitude pattern.

In short, the base Nina state in the Pacific proved more resilient to the a-typical MJO convection pattern further west. Net result : more La Nina easterly trade wind inertia remaining in the atmospheric circulation at the expense of tropical convection induced westerly wind bursts to sustain the Pacific jet extension into the Pacific (as alluded to by Michael Ventrice in his well worth watching video on @Bring Back1962-63 equally well presented thread).

So, the latest MJO wave headed from the Indian Ocean faces an added surplus of La Nina forcing in the system compared to December. The implications of La Nina -ve torques have been discussed by me in at least the last two summaries in terms of the strength produced of the sub tropical highs (which naturally includes the Azores high in this sector)

Its not just about the MJO of course. A reversal of low angular momentum -ve torque to a sufficiently+ve frictional torque response within the tropics c/o the MJO making amplitude progress to the Western Pacific (without then encountering easterly trade wind shear and cause weakening and loss of amplitude to the 'COD'), will  in turn shape the net amplification response within the extra tropics (the synoptic pattern) and associated +MT wave breaking to impact the stratosphere.

Translated into synoptic evolution parlance: If the natural re-bound response of angular momentum from its present low cycle point does not sustain strongly enough into the extra tropics (and we have to take the logical perspective that the atmosphere is potentially less conducive to processing amplifying +AAM anomalies than December) it means that once next weeks cold trough heads slowly off into mainland Europe, we  may not see sufficient and/or sustained enough poleward amplification of the Azores/Atlantic ridge in its wake, to take full advantage of the developments towards - AO within the polar field through the month 

If the analysis of preceding posts is taken into account explaining how +ve frictional torques in tandem with rising AAM tendency weaken the influence of the sub tropical ridges at mid latitude (inc Azores High) and -ve torques c/o of low AAM sustain them, then based on  those GWO composites for Phase 3 and Phase 4:

-as usual, best not to take literal interpretation of those composites at face value.  But suffice to say that  GWO Phase 3 (the lower AAM phase) infers greater suggestion of less amplification downstream of mid latitude ridging with the greater forcing for this kept upstream across the Pacific to also retain strength in the Canadian vortex- albeit slightly retracted to allow at least a temporary amplification of the Atlantic ridge.

With this in mind, frictional torque tendency remains depressed:

We have to take into account lag time responses for any upturn also, of which there is (currently) no indication.

So my niggling concern , which was omnipresent when I made a pre-seasonal post back in November is that the sub tropical ridging (the Azores High) as part of the traditional La Nina pattern, could well continue to do its best to be a potential spoiler to help evolve a colder and colder progressing pattern into what it might otherwise be towards the latter part of the month.

The last part of that previous sentence needs careful interpretation. Its taken within the context of any wave 2 external forcing on the stratospheric vortex later this month. Clearly though, a stubborn +NAO pattern, would not be helpful to maximise the cold air advection potential of any vortex submission that might occur

As ever, not a predictive forecast summary from me. I leave it to others to make competitive predictions. Its simply my usual take on what might go wrong as well as might evolve according to what the majority would prefer to hear.

At some stage, when time permits, I intend to contribute to the learning thread using this kind of neutral approach to these tools that are usefully intended to help pre-empt NWP - as it is the biased use of them trying to fit signals to a desired pattern (cold or otherwise) that lends itself to the parochial dismissal echoed by some on these fast pace, very reactionary threads. Many others of course are more open-minded.

 

Based on the apparent disappointment and let down of anticipation evident in various quarters, there are no apologies at all for re-posting a sizeable chunk of the post made just two days back.

Much of the frustration is aimed at the Azores high - but the above analysis and at least two posts prior to that gave plenty of suggestion and associated reasoning and explanation of why  sub tropical ridging might continue to play a large part of the pattern to mid latitudes. Certainly a player in terms of the persistent strength of the Azores High based on the large programmes of La Nina easterly trade winds that underpin such ridges - with parallel strength of polar jet flow in evidence above the northern flank of the ridging

This pattern should be no surprise at all - essentially it has waxed and waned around the same theme since the summer, and just happened to coincide with when the first really significant programme of La Nina trades was evident and angular momentum took a tumble into August.

As a reflection of so much easterly trade inertia, total atmospheric angular momentum has fallen to about its lowest level since the inception of this La Nina.

 The Global Wind Oscillation, which is an orbit plot simulation of atmospheric angular momentum tendency as calculated by net total global wind-flows at any given time (and which sustain the jet stream) depicts the large easterly surplus in the atmospheric circulation by a considerable amplitude passage that centres it around low angular momentum Nina Phase 2.

 For atmospheric angular momentum tendency to overcome this deficit it can be seen just how much westerly wind momentum has to be added to the global windflow circulation by eastward passage of tropical convection, namely the MJO.

Another way of looking at what lies ahead of the MJO westerly wind bursts, is the cross section of strongly -ve wind anomalies across the Pacific representing the wall of easterly trades ahead of the MJO.

These easterlies are focussed in the critical downstream 'amplification phases' - the wind shear effects of these easterlies risk substantial weakening of the MJO and hence insufficient forcing to take avantage of any external forcing taking place in times ahead within the polar stratospheric field. Again, as discussed in previous posts. On that basis there is downside risk to atmospheric angular momentum recovery associated with MJO forcing to enable effectiveness of this in the way desired on these pages..

Much can still happen in the extended period, and how the unfavourable tropospheric drivers interact with any stratospheric weakness signal later this month will be interesting to see, Albeit, if the tropics and extra tropics do not co-operate it will clearly not help at all.

Time will tell.

But there is no 'winters over' message associated with this post, or any other post either which seeks to provide balance to the search for cold weather that popularly occupies this thread. But one main purpose of persisting with downside as well as upside risks is to demonstrate that it is not the signals or the teleconnection that is always at fault  - its much more the individual interpretation of them which can too easily weight probability favour towards a biased and preferred solution.

It is this which continues to be a constant theme in terms of combatting any remaining mythology or misrepresentation of posts.

Its not always about what one would prefer, but trying to put forward a realistic range of solutions that NWP may evolve towards. In that sense neither the models or the messenger should be hung out to dry, simply any biased expectations that may relate to either of these and have not been correctly managed.

 

 

[Weegaz]

In my view the gfs has modelled the up and coming snowy period this week quite well. Signal was definitely picked up

Chart below 10 days out and now 3 day chart

[nick sussex]

37 minutes ago, comet said:

Very disappointing model viewing it has to be said. It certainly makes you feel that this model watching is a complete waste of time, commentating on charts at plus t168 then everything implodes and charts at t96 etc can not be trusted. Not trying to have a dig but even positive posts from those that follow the teleconnects more closely look to have come unstuck. I have never been a fan of the NOAA updates as they never seem to offer much assistance and sure enough the last update I read on here mentioned a more amplified upstream pattern over the states which would have benefited us yet the reverse now seems to be the case.

Warming is still being advertised in the gfs strat charts but this has been somewhat delayed and watered down from what the charts were showing three or 4 days ago although it does look as though there is now more of a response height wise with the vortices becoming more stretched again at 10 and 30mb. If this trend continues then a split may well be evident in early February.

Some of the more favoured areas likely to see some snow (perhaps significant) this week while for most the chance of some wintry showers with maybe a temporarily covering.

It was me! 

I’m just relaying what NOAA think and their discussion. they preferred the more amplified solutions over the eastern USA because they better fitted the ridge upstream .

So they went with the ECM but even if they had gone with the others  that would still be much more amplified than today’s solutions.

The models have made a pigs ear of the upstream pattern couldn’t even get the engagement of the Pacific originating shortwave with shortwave energy correct over the ne USA at T120hrs.

Although  they might tone down the amplication they’ve gone almost completely flat barring the ECM .

I’d put today’s debacle as even worse than some of the easterly trigger shortwave dramas which are more complicated to model.

[swfc]

4 minutes ago, nick sussex said:

It was me! 

I’m just relaying what NOAA think and their discussion. they preferred the more amplified solutions over the eastern USA because they better fitted the ridge upstream .

So they went with the ECM but even if they had gone with the others  that would still be much more amplified than today’s solutions.

The models have made a pigs ear of the upstream pattern couldn’t even get the engagement of the Pacific originating shortwave with shortwave energy correct over the ne USA at T120hrs.

Although  they might tone down the amplication they’ve gone almost completely flat barring the ECM .

I’d put today’s debacle as even worse than some of the easterly trigger shortwave dramas which are more complicated to model.

Anyway back nick given the quick change over 24hrs ??? I'd say probably not but we live in hope. The areas towards esb and canada look so complicated I guess anything could happen barring the uk getting a real taste of winter!!lol

 

 

[MP-R]

It's all about the upstream this week - Canada's constant flatulence of cold really not helping. Should  the midweek bomb transpire (on the same date as that of January 2007's), a similar progression thereafter would be a lot better than what particularly the GFS is showing from the 21st onwards!

  

We were very close to a decent cold spell then. Amplification was on hand from the west and at least a colder drier pattern ensued, with some snow on the 24th (third chart) but then the high pressure toppled in and it got milder with no decent link up to Greenland, that is until the coldest spell of the winter in the first week of February.

Regardless of what happens this week, we really need the Azores High / Canada cold combination to chill (pardon the pun).

[Frosty.]

Having just read the latest update, sounds very similar to yesterday, no indication that we are looking at a sw / ne aligned jet in just over a week's time bringing much milder conditions as some of the latest operational / ensemble output shows so far today which has caused the downbeat mood among some coldies!...lets wait and see what the 12z has to offer!

[andymusic]

3 minutes ago, Frosty. said:

Having just read the latest update, sounds very similar to yesterday, no indication that we are looking at a sw / ne aligned jet in just over a week's time bringing much milder conditions as some of the latest operational / ensemble output shows so far today which has caused the downbeat mood among some coldies!...lets wait and see what the 12z has to offer!

absoflippinlutely - as some others have said beyond t96 is fI - let's see what other options are on the table before throwing in the towel begins lol

Edited January 14, 2018 by andymusic

[Yorkshirepudding]

3 hours ago, offerman said:

Nice post snowbunting. 

 

Classic examples of too much excitement too far out and the charts letting people down as the event draw nearer. 

 

When will folks learn not to get their  aspirations and excitement up too much beyond 3-4 days. 

Time and time again it happens with the charts . Most of the time to the let down side for collies . 

I love the cold and snow. I too once always looked too far ahead getting excited only to be let down. I see so many others doing the same. You can’t predict the weather so far out. Just look to charts 3-4 days within but even these can change but should be more reliable timeframe as rule of thumb. 

On the flip side. People looking at models for the first time this morning without knowing the last 3days events with 36-48 hours still out would be thinking "Potential" I've seen events change within 12hours. Given the change isn't as dramatic but still its changeable. One thing I've learnt over the years you can never predict the weather. Lol. 

[nick sussex]

Much of todays drama is in relation to two areas circled. I posted a few days back regarding the phasing of energy there and this was when we were seeing a divergence of opinions between the outputs.

The circled red over Canada started its life on the Pacific coast, the more amplified solutions took this further south over Canada which then phased favourably with shortwave energy running up the eastern seaboard.

 

The best downstream solution in terms of margin for error and cold would be the one which phased that into one more amplified  system near the coast as that would develop a cleaner evolution downstream with a better ridge to the west.

The ECM was the one with the most amplified solution so we've seen from experience it can overdo that, however the other outputs began to converge on not as amplified but more than they were.

Now you can see today still divergence as the ECM still goes onto develop one system at least with some better ridging to the nw.

This is all because it has a more favourable phasing outcome between those areas circled shown earlier at T96hrs. The ECM solution if it wasn't so isolated would be something that although flatter than recent days you could see how it could evolve better.

Unfortunately the others are resolutely not interested with a totally different view of events upstream.

So tonights 12hrs runs are really the last chance if you want to see a better evolution because given the timeframes involved its unlikely this divergence will last much longer in terms of the pattern upto T168hrs.

 

 

 

[BLAST FROM THE PAST]

On 12/01/2018 at 19:48, BLAST FROM THE PAST said:

This Atlantic thrust has come earlier than expected as in it’s penetration through us.  The fact there’s signs of it getting disrupted I’m not entirely surprised as I anticipate another displaced PV chunk to hit us towards last week of the month.  So for me what is initially coming is a bonus....let’s see what develops onwards....but any break in cold Synoptics is only resetting for main surge.

 

BFTP

So deteriorating Synoptics on 00z runs for any prolonged cold pattern.  We are currently travelling through strong solar wind burst from coronal and thus I anticipate a ramping/ certainly consolidation of rough Atlantic affect mid week....not that it isn’t showing  lively enough currently.  Track of that ‘runner’ and how it develops sure one to watch ( sun is blank again)....so changes are imo still up for grabs re jetstream movement and track of the lp.  Down the line still no reason for me to not still forecast another displaced PV movement over us to usher in main event during the last week of Jan into Feb.

However, on my above basis my view is that we will be Atlantic driven over coming 2 weeks, but hopefully continuation of cold pM air.

However, the model movement today needs to be watched for momentum or being a glitch.  

 

BFTP   

Edited January 14, 2018 by BLAST FROM THE PAST

[johnholmes]

this is oh so true, and of so many on here.

It is this which continues to be a constant theme in terms of combatting any remaining mythology or misrepresentation of posts.

Its not always about what one would prefer, but trying to put forward a realistic range of solutions that NWP may evolve towards. In that sense neither the models or the messenger should be hung out to dry, simply any biased expectations that may relate to either of these and have not been correctly managed.

I have only just started to pick up on the events of the past 18 hours or so. A quite large change in UK Met outputs re their Fax charts, and this extends to their upper air charts on the same link, scroll down and compare the 00z Friday with the previous issue for Friday. Quite a marked change with the upper ridge from the Azores not on he 12z but noticeable on the 00z output. I wonder what has caused their model to do this? It appears to have caused a similar change on the others although I have not had time took closely. It would be great to be able to hear what the senior man is suggesting in his techincal chats with colleagues in Exeter and elsewhere.

Who knows may be it is a 24 abberation-unlikely though!

[OfficialKevWX]

I’d expect a reload of cold probably around the 23rd if the Atlantic wins out on this one