Jump to content
Holidays
Local
Radar
Snow?
Sign in to follow this  
Paul

Model output discussion - mid January

Paul

Before posting in to the model discussion, please read our guide to posting in the model threads.

Message added by Paul

Recommended Posts

Just now, WalsallWeather123 said:

Forget that I quoted that chart. Just generally talking about -8 uppers meaning marginal conditions. Not guaranteed a widespread snow event 

Just a quick one  But the -8 from a north westerly  at the moment is shown to be hitting Continental Air.  Its a typical Battleground Scenario.  Granted if it was hitting the UK after a mild few days then Possibly  But here in the Midlands  the majority of our snow events this year have come from this direction  with Higher uppers.  

Share this post


Link to post
Share on other sites
1 minute ago, Yarmy said:

I like Liam Dutton, but the latest GFS inter run comparison does not tally with this assessment regarding the inferior performance of the 6z and 18z runs:

cor_day5_HGT_P500_G2NHX.png

The stuff about fewer observations is not true either. I recommend reading this thread, especially the post from dtk, a meteorologist working at NCEP:

https://www.americanwx.com/bb/topic/32149-gfs-12z-and-0z-runs-compared-to-6z-and-18z-runs/

The model as whole of course, is consistently outperformed by the Euros.

 

 

 

ensemble-tt6-london.gif

Share this post


Link to post
Share on other sites

Just a quick one, but why oh why do people spend so much time trying to guess snowfall from various model runs, when the model runs actually output that info? I mean, why say "Oh, too marginal" "Oh, it is indeed cold enough for snow". When you could actually just look at the output.

And then after you went to look at the output, ask yourself why you bothered so far out anyway.

 

Share this post


Link to post
Share on other sites

Be good if almost everything in the last few pages was banished to the moans & banter thread. Same old story, sadly, first sign of cold potential in the models and there's always someone ready to spew a plume of groundless hot air all over it, swiftly followed by a scrabble of rampers keen to defend a bunch of charts that haven't verified yet. This season has been much more interesting than many recent winters for most in the North/North West and Central Midlands (amongst others) but for the rest of us it's been a damp squib. I've seen a few flakes on the East Coast but as yet the kids haven't had chance to make a snowman (not even a mini one!) which is my standard measure of a winter worth remembering. The models this morning hold a great deal of potential but there is still much to be decided. On this forum, anyone saying we can fully expect cold rain is clearly a masochist and anyone rushing to shoot them down (secretly has my support but...) probably ought to know better. Good trends this morning, I'm very interested to know whether the 12z GFS continues to fall into step with the Euros or even improve on them. The Iceland Met Office site http://en.vedur.is/weather/forecasts/atlantic/#type=temp which shows ECM precipitation for next week looks interesting as a front pushes into unusually cold uppers Tues/Wed. Long may the interest continue.

ECM0-144.GIF

180131_0000_144.png

Share this post


Link to post
Share on other sites
11 minutes ago, Tamara said:

It was well intended and well meant advice:)

Taking NWP in the round, the stubborn persistence of polar jet energy (until now) flowing from upstream across the top of the Azores ridge has been indicative of a dominating +NAO pattern attributable to the lagged low point of atmospheric angular moment c/o La Nina forcing and stronger than average easterly trade winds since the turn of the New Year.

Whilst there is not yet any undercutting -AO/NAO Feb 1978 type redux fully apparent - NWP is now, within the reliable period, adjusting the upstream energy process incrementally, bit by bit, as greater and greater downstream amplification is finally being realised.

If we take another look at a yearly GLAAM anomaly, the size of the peak of the-ve GLAAM anomaly achieved is evident - which saw the La Nina strengthened trade winds ramp upwards.

MR-latest-365days.png

The atmosphere is now fast recovering from that low angular momentum regime and NWP attempting evolution of another Scandinavian ridge such as was seen in the first part of February 2017. That tropical momentum led +AAM anomaly spike, was discussed in a recent post, is clear to see again in the above 365 day chart for early February 2017

Back to ushering in Feb 2018:

High amplitude tropical convection progression with rapidly rising AAM tendency has all but scrubbed out that -3SD GLAAM deficit ^^ - and still heading upwards. The atmospheric state is becoming increasingly conducive to +ve poleward momentum flux helping to amplify the tropospheric pattern more meaningfully. This leading towards a much better shaped H500 anomaly to externally destabilise the vortex. This, at the same time as internal +ve mountain torque forcing occurs - as a direct consequence of the poleward +AAM anomalies c/o tropical forcing propagating to the extra tropics and perturbing the troposphere/stratosphere boundary.

To put some timelines to all this with the aim of helping explanations :

If we take a look at the Global Wind Oscillation below, which should be seen as a measure of how the amplified wind-flows are progressing from tropics to extra tropics- then the initial signal fired from the tropics to start the process now unfolding in NWP was around 22nd January as can be seen by the plot (high amplitude GWO Phase 3 into Phase 4).

This signal is representative of a surface +ve frictional torque which indicates the axis points where westerly winds in the tropics added by the forward movement of tropical convection start the initial process of scrubbing out the easterly trade winds responsible for the greater polar jet flow at mid-latitudes that inhibits amplification.

gwo_fnl.png

The lag time for this +ve frictional torque and associated poleward heading +AAM wave flux anomalies to arrive in the extra tropics is ~10 days. Based on the starting pistol fired around the 22nd January, the GWO progression confirms this ETA of momentum in the extra tropics by the imminent expected orbit to the boundary of Phase 4/5 and engagement of a considerable size +ve mountain torque.

See the added GWO template that confirms where these torque processes have taken place within the relevant phase progressions

gwo_phase_fig4.jpg

This mountain torque event has some highly interesting possible implications  - not just for the amplification programme clearly underway in NWP into the medium term and increasing programme of cold air advection, but also in terms of the sharper NH hemispheric pattern which corresponds to assist external stratospheric meltdown.

Such as stratosphere forecasts are playing peek-a-boo with.

At this stage, what is interesting about the current evolution is that, *she adds with due caution*  it looks slower and more sustained than Feb 2017.  

There are tentative suggestions of a slow burner,  as the models keep adjusting the pattern further on into the medium term to one that is more meridional due to +AAM flux.

It  *could be* that the +ve MT delivers something of an icing on the cake from mid month. Something to keep watching out for in the longer term.

Lag time for +MT >stratosphere/troposphere fall-out around 12- 14 days.

This zonal wind cross section illustrates how the westerly wind additions c/o tropical forcing is impacting the rossby wave pattern upstream, with the emerging propagation of +ve shaded anomalies replacing the sustained bursts of -ve anomaly easterly trade winds evident across the Pacific since the turn of the New Year.

u.anom.30.5S-5N.gif

This is another way of illustrating the switch from sharply -ve AAM anomalies to a contrasting swathe of +AAM anomalies impacting the extra tropics and as a consequence re-configuring the pattern from upstream with less strength into the northern branch of the jet stream - with more split jet flow and consequently greater trough disruption downstream - hence better mid to higher latitude amplification of ridging. 

The signs are emerging that the new travel of direction is gaining traction - with suggestions the models are contemplating a volte face towards a cold and blocked pattern with CAA ambush from both the NW and NE.  As soon as this weekend.

All rather confirming suspicions of recent days, and echoed in the semantics of the highlighted post above- that the flatter low angular momentum legacy might well be over-cooked.

In that sense on-going NWP suites are simply snapshots in time to the evolution of the pattern playing out.

Adopting this philosophy, it becomes more possible to watch what happens without unnecessary instinctive reactions to face value variations and swings within intra day operational modelling (and ensemble suites)

I'm not sure that either of these have been especially instructive to any great distance of late. If the latest trends are anything to go by this is already obvious.

Its not through it being my own model of choice based around  preference, but because its the model that has been best fitting the pattern to the signals on this occasion that the UKMO has been leading the way and paving the evolution of the pattern into the weekend and beyond. NWP is starting to better matches the suggested GWO evolution of recent days and makes more sense (to me at least!)

It does seem that an all-round catch-up is in progress and that might seem a (very pleasant) surprise to anyone who has taken NWP at face value in recent days:smile:

 

Summed up my optimism in a much more skilled way!

Share this post


Link to post
Share on other sites
1 hour ago, Man With Beard said:

The classic example of a cold UK chart even with a raging vortex over Canada

gfsnh-0-108.png?6  gfsnh-1-108.png?6

I do kind of wonder how I've missed this - when I get a minute I'll go back through the recent charts and see if there were signs I missed, or if it was the models (UKMO excepted) that missed it.

The 6th/7th need serious flagging for snow - when a front gets squeezed by cold left and right like this, big risk

gfs-1-156.png?6

 

All snow likely yes, but not really that much in the way of ppn, shouldn't be too big accumulations, especially not a 'big risk'.

Share this post


Link to post
Share on other sites

Well I have had no look at the models till now and wow! I can’t say I am surprised this is what happens with these set ups we see this short term upgrades at short notice, and suddenly we’re in a very nice place. 

Share this post


Link to post
Share on other sites
24 minutes ago, Tamara said:

It was well intended and well meant advice:)

Taking NWP in the round, the stubborn persistence of polar jet energy (until now) flowing from upstream across the top of the Azores ridge has been indicative of a dominating +NAO pattern attributable to the lagged low point of atmospheric angular moment c/o La Nina forcing and stronger than average easterly trade winds since the turn of the New Year.

Whilst there is not yet any undercutting -AO/NAO Feb 1978 type redux fully apparent - NWP is now, within the reliable period, adjusting the upstream energy process incrementally, bit by bit, as greater and greater downstream amplification is finally being realised.

If we take another look at a yearly GLAAM anomaly, the size of the peak of the-ve GLAAM anomaly achieved is evident - which saw the La Nina strengthened trade winds ramp upwards.

MR-latest-365days.png

The atmosphere is now fast recovering from that low angular momentum regime and NWP attempting evolution of another Scandinavian ridge such as was seen in the first part of February 2017. That tropical momentum led +AAM anomaly spike, was discussed in a recent post, is clear to see again in the above 365 day chart for early February 2017

Back to ushering in Feb 2018:

High amplitude tropical convection progression with rapidly rising AAM tendency has all but scrubbed out that -3SD GLAAM deficit ^^ - and still heading upwards. The atmospheric state is becoming increasingly conducive to +ve poleward momentum flux helping to amplify the tropospheric pattern more meaningfully. This leading towards a much better shaped H500 anomaly to externally destabilise the vortex. This, at the same time as internal +ve mountain torque forcing occurs - as a direct consequence of the poleward +AAM anomalies c/o tropical forcing propagating to the extra tropics and perturbing the troposphere/stratosphere boundary.

To put some timelines to all this with the aim of helping explanations :

If we take a look at the Global Wind Oscillation below, which should be seen as a measure of how the amplified wind-flows are progressing from tropics to extra tropics- then the initial signal fired from the tropics to start the process now unfolding in NWP was around 22nd January as can be seen by the plot (high amplitude GWO Phase 3 into Phase 4).

This signal is representative of a surface +ve frictional torque which indicates the axis points where westerly winds in the tropics added by the forward movement of tropical convection start the initial process of scrubbing out the easterly trade winds responsible for the greater polar jet flow at mid-latitudes that inhibits amplification.

gwo_fnl.png

The lag time for this +ve frictional torque and associated poleward heading +AAM wave flux anomalies to arrive in the extra tropics is ~10 days. Based on the starting pistol fired around the 22nd January, the GWO progression confirms this ETA of momentum in the extra tropics by the imminent expected orbit to the boundary of Phase 4/5 and engagement of a considerable size +ve mountain torque.

See the added GWO template that confirms where these torque processes have taken place within the relevant phase progressions

gwo_phase_fig4.jpg

This mountain torque event has some highly interesting possible implications  - not just for the amplification programme clearly underway in NWP into the medium term and increasing programme of cold air advection, but also in terms of the sharper NH hemispheric pattern which corresponds to assist external stratospheric meltdown.

Such as stratosphere forecasts are playing peek-a-boo with.

At this stage, what is interesting about the current evolution is that, *she adds with due caution*  it looks slower and more sustained than Feb 2017.  

There are tentative suggestions of a slow burner,  as the models keep adjusting the pattern further on into the medium term to one that is more meridional due to +AAM flux.

It  *could be* that the +ve MT delivers something of an icing on the cake from mid month. Something to keep watching out for in the longer term.

Lag time for +MT >stratosphere/troposphere fall-out around 12- 14 days.

This zonal wind cross section illustrates how the westerly wind additions c/o tropical forcing is impacting the rossby wave pattern upstream, with the emerging propagation of +ve shaded anomalies replacing the sustained bursts of -ve anomaly easterly trade winds evident across the Pacific since the turn of the New Year.

u.anom.30.5S-5N.gif

This is another way of illustrating the switch from sharply -ve AAM anomalies to a contrasting swathe of +AAM anomalies impacting the extra tropics and as a consequence re-configuring the pattern from upstream with less strength into the northern branch of the jet stream - with more split jet flow and consequently greater trough disruption downstream - hence better mid to higher latitude amplification of ridging. 

The signs are emerging that the new travel of direction is gaining traction - with suggestions the models are contemplating a volte face towards a cold and blocked pattern with CAA ambush from both the NW and NE.  As soon as this weekend.

All rather confirming suspicions of recent days, and echoed in the semantics of the highlighted post above- that the flatter low angular momentum legacy might well be over-cooked.

In that sense on-going NWP suites are simply snapshots in time to the evolution of the pattern playing out.

Adopting this philosophy, it becomes more possible to watch what happens without unnecessary instinctive reactions to face value variations and swings within intra day operational modelling (and ensemble suites)

I'm not sure that either of these have been especially instructive to any great distance of late. If the latest trends are anything to go by this is already obvious.

Its not through it being my own model of choice based around  preference, but because its the model that has been best fitting the pattern to the signals on this occasion that the UKMO has been leading the way and paving the evolution of the pattern into the weekend and beyond. NWP is starting to better matches the suggested GWO evolution of recent days and makes more sense (to me at least!)

It does seem that an all-round catch-up is in progress and that might seem a (very pleasant) surprise to anyone who has taken NWP at face value in recent days:smile:

 

Super informative post. Thanks Tamara

Share this post


Link to post
Share on other sites

Good too see the models are showing the height rises starting to influence our weather a bit more now but as for the details then that remains unclear but it does look like there is a risk of some persistant snow for some on Saturday.

The issue I see is the raging PV across Canada which is forecast to spill into the Atlantic and that will put pressure on any blocking but it can also help potentialy to create battleground snow events so it be interesting what the models will show in the coming days.

Either way, a colder spell of  weather has arrived and it will be here for the forseeable future so no more double figures for a while thankfully. 

Share this post


Link to post
Share on other sites
24 minutes ago, supernova said:

Be good if almost everything in the last few pages was banished to the moans & banter thread. Same old story, sadly, first sign of cold potential in the models and there's always someone ready to spew a plume of groundless hot air all over it, swiftly followed by a scrabble of rampers keen to defend a bunch of charts that haven't verified yet

I say, that's a little harsh on some of the well-reasoned responses to a flurry of Wa***** posts (thanks Wa****  for opening up page 13 of my 'ignored' posters - for those getting exercised by some of the irrelevant stuff on here, hover over the poster profile, click on ignore ... they tend to be serial offenders and reading the thread without them makes for lower blood pressure! Be your own moderator!).

Anyway, thanks for the serious/knowledgeable posts from the usual people at this time of intrigue and excitement - the less experienced on here benefit greatly from your posts :)

Share this post


Link to post
Share on other sites
2 hours ago, Man With Beard said:

The classic example of a cold UK chart even with a raging vortex over Canada

gfsnh-0-108.png?6  gfsnh-1-108.png?6

I do kind of wonder how I've missed this - when I get a minute I'll go back through the recent charts and see if there were signs I missed, or if it was the models (UKMO excepted) that missed it.

The 6th/7th need serious flagging for snow - when a front gets squeezed by cold left and right like this, big risk

gfs-1-156.png?6

 

There is always talk of how a rampant vortex to NW will just plough anything through. For the 4th and 27 years ago to that day one does see some similarity there not expecting the level of cold however. 

A0F39D22-84E2-4793-9982-D511FEA36DF2.thumb.png.857a33413b8e3b50396b643ed6d79a1c.pngB38C56AA-C08C-45C5-947B-D174928EC7FD.thumb.png.78f81a6fb3512292614479e2f6905cd7.png

Share this post


Link to post
Share on other sites

Thanks for the excellent update @Tamara :good:

I was about to put forward that this is increasingly looking to be the validation of GWO 3-4-5 / rising GLAAM impacts that has been long awaited this season after the attempt a month ago was first undermined by poor continental cold availability during the precious window of time prior to the more mobile, zonal period that itself validated the GWO 8-1-2 / falling GLAAM impacts.

This you have effectively done in recent posts but no harm in re-iterating, eh? :D

 

Although even now I'm having to use 'looking to be' in case some regional anomaly decides to trash the party in terms of the details next week :rolleyes: but what can you do, it is the UK after all :laugh:.

Share this post


Link to post
Share on other sites

Afternoon all :)

Plenty of interesting comment and I hope for everyone's sake we get a decent shot of cold/snow.

From the 06Z GFS Ensembles I'll take P10 all day every day for the next two and a bit weeks.

 

Share this post


Link to post
Share on other sites
On 29 January 2018 at 11:22, Sky Full said:

 

On 29 January 2018 at 11:22, Sky Full said:

Irrespective of what we might expect beyond 10 days in deep FI the model ops are showing a trend towards a colder snap almost in the reliable range at +168h (5th February)....

ECM     image.thumb.gif.a44387fbd30893efd281aff561a6b3a7.gif    image.thumb.gif.e1038d323220f70b00a4b5ff532e59a0.gif

Anyway, it is a possible trend which offers some potential!  :)

On the 29th January the ECM was showing the above evolution for the 5th February ^^^

This morning the ECM 0Z was showing the following for the same time and date:

image.thumb.gif.9d373979bad6d78b18276bb1ed2c516f.gif   image.thumb.gif.8010cdb9e3f5c9408f6bd9401071edf3.gif

and then goes on to this for the 6th:

image.thumb.gif.f9e353e9ba4acc46a2d3cb6964b12fb1.gif   image.thumb.gif.b793a27f3e61671102e0d3ee8ed75541.gif

and then the 7th.....

image.thumb.gif.f5645569870aff80597019b27b16743e.gif   image.thumb.gif.50904b7db2e0f2dfadbd6f689ab7bd12.gif

Now that's what I call an upgrade... (for those that don't want to write off winter yet, anyway!)   :)

(Oops - have quoted my own post twice - Doh!  Sorry about that...)

 

 

Edited by Sky Full
.

Share this post


Link to post
Share on other sites
1 hour ago, jvenge said:

Just a quick one, but why oh why do people spend so much time trying to guess snowfall from various model runs, when the model runs actually output that info? I mean, why say "Oh, too marginal" "Oh, it is indeed cold enough for snow". When you could actually just look at the output.

And then after you went to look at the output, ask yourself why you bothered so far out anyway.

 

 

Well you could just look out the window I guess

It’s a model discussion thread so if I see

7 Feb 3am

prectypeuktopo.png

I'm lamp post watching with my friends

untitled.png

Edited by stewfox

Share this post


Link to post
Share on other sites
4 minutes ago, stewfox said:

 

Well you could just look out the window I guess

It’s a model discussion thread so if I see

7 Feb 3am

prectypeuktopo.png

I'm lamp post watching with my friends

untitled.png

You would have been better off quoting and bolding the next few sentences and then merely saying "I agree".

 

Share this post


Link to post
Share on other sites
9 minutes ago, jvenge said:

You would have been better off quoting and bolding the next few sentences and then merely saying "I agree".

 

You’re such a bore jvenge hopefully some freezing temps and snow would do you good.. :D

Share this post


Link to post
Share on other sites

GEFS are very much improving. I believe @Singularity mentioned the low exiting the east coast at 126 yesterday which of course was being sent straight over the block is now adding amplification to Azores high out west which puts a bit of oompf downstream over the UK maybe giving a snow event? 

Who knows but there is plenty to play for right now.

Edited by SN0WM4N

Share this post


Link to post
Share on other sites
Just now, Daniel* said:

You’re such a bore jvenge hopefully some freezing temps and snow would do you good.. :D

Well. Sometimes I think I'm typing in Romanian on here, with how people seem to be confused by my posts. As the guy above seemed to be agreeing withme by looking at the output, which is kinda what I said people should do.

Also, I just had two weeks where temperatures stayed between -3 and -13. Keep it :D I have a beautiful bruise on my hip from the joys of ice.

 

Share this post


Link to post
Share on other sites

Good afternoon

Some fascinating model output at the moment. One of those easterlies out of nowhere types scenario and I feel something exciting could be unfolding.

Unusually we have a situation where we have continental cold building to the east and Greenland cold spilling out into the North Atlantic. After such a long time with continental mildness to our east we are looking at a change.

A look at the temperature anomaly maps over the next week appears very interesting with warm air over SE Europe and cold air over Scandi. This will probably help encourage the formation of low pressure over the Med.

temp4.png

At T120 on the 06z GFS we have two notable cold pools around us split by a mild edge. It would be easy to see this falling as snow somewhere over the UK.

GFSOPEU06_144_2.png

So many fine details to sort out before then though. Ideally we want the Azores high to hang back a bit to allow more energy to slip under the Scandi high.

Long term output also appears encouraging with a high over Svalbard helping pump some seriously cold air to our east on some ensemble members. Ideally we would want that mild air to head straight into the arctic.

Anyhow some very cold ensemble members just to our east on the 06z ens.

GFSC00EU06_192_2.pngGFSP02EU06_192_2.pngGFSP05EU06_192_2.pngGFSP06EU06_192_2.pngGFSP09EU06_192_2.pngGFSP10EU06_192_2.pngGFSP14EU06_192_2.pngGFSP15EU06_192_2.pngGFSP17EU06_192_2.pngGFSP19EU06_192_2.png

Isn’t it ironic that we have had signals for a good cold spell fail to materialise several times from medium range. Now suddenly one pops up at T44 and looks like it may deliver something for the SE?

Still may not work out but this could be vindication for Steve Murr, Nick Sussex’s et al persistent searches for cold when it would be easier to pull our heads down after this January (though I know further north its been better).

A fair way to go yet though, the 12z’s will be very interesting to watch.

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...