Model Output Discussion - The Start Of Winter

[Snowman.]

Better polar heights forcing the low of the eastern seaboard further southward to allow for better amplification.

 

 

Allowing colder uppers to sweep south, snow possible at all levels potentially in the north of scotland combined with the wind and low pressure system looks to be a rather conductive snow session for the north.

Edited December 4, 2014 by SN0WM4N

[Panayiotis]

A much different story on the 12z GFS with a much more amplified high over the Atlantic at 168hrs compared to the 06z, could we be seeing an attempt from the GFS to ridge that high up and over the UK forming a Scandi high? Not on this run, but it could be a new trend to look out for over the coming days if that low exiting the US becomes more negatively tilted...

PS: I have come out of hibernation especially with snow on the horizon for some! Interesting winter ahead...

Edited December 4, 2014 by Panayiotis

[Barry12]

Interesting day 6 on the UKMO, arctic high, beaten up vortex, azores moving SE and a cold NW flow.

 

Edited December 4, 2014 by Barry95

[knocker]

A much different story on the 12z GFS with a much more amplified high over the Atlantic at 168hrs compared to the 06z, could we be seeing an attempt from the GFS to ridge that high up and over the UK forming a Scandi high? Not on this run, but it could be a new trend to look out for over the coming days if that low exiting the US becomes more negatively tilted...

PS: I have come out of hibernation especially with snow on the horizon for some! Interesting winter ahead...

 

I find that post quite extraordinary. Some weird speculation regarding the Azores high, based on one chart, and ignoring the potential storm. And I'm no doubt being a bit thick but what does, "if that low exiting the US becomes more negatively tilted" mean?...

Charts courtesy weatherbell

Edited December 4, 2014 by knocker

[PolarWarsaw]

I find that post quite extraordinary. Some weird speculation regarding the Azores high, based on one chart, and ignoring the potential storm. Plus if you moved on a few frames...............................

 

Charts courtesy weatherbell

 

That'll be something to do with the fact that very few people are interested in anything other than winter weather possibilities. You could probably put a CAT 5 hurricane over the UK in the middle of December and a day 12 ECM chart showing -5 uppers over Berlin would get more interest. You are a minority. One would counter that, and as mentioned in previous posts...this atlantic train we have been constantly reminded of since the first week of November...must be broken down somewhere along the line, either that or my tickets have been lost in the post, because I for one have seen absolutely, completely and totally zero sign of the 'inevitable zonal' train touted around by certain members. Some would consider that 'quite extraordinary'. 

 

The charts both of you have posted have similar chances of coming to fruition. It is nice to see that the charts have offered us some more exciting weather forms that we can expect to see in the next 10 days or so. I can see quite a wind event for the north at some point during the current output, here's hoping. Anything to deter us away from this boring atlantic train 'stalemate' we've seen over the last 6-7 weeks.

 

On another note, very frosty and cold overnight with more of the same expected tonight. Wrap up folks, we've already had more winter this year than we did last...all us winter lovers can rejoice in that fact alone!

 

Brrrrrrrr!! 

Edited December 4, 2014 by PolarWarsaw

[nick sussex]

The UKMO and GFS again different upstream:

 

The UKMO at T144hrs has that coastal USA low likely to run more ne, aswell as this you'll see that shortwave complication east of the main low:

 

 

The GFS has a weaker feature further ne which phases with the PV over Greenland later:

 

 

These differences are important going forward so until this is resolved I'd keep an open mind especially as the UKMO at T144hrs has started lifting low heights away from southern Greenland.

 

In recent days the UKMO has hardly been a star performer so I think we need to see the ECM to see which output it backs.

[knocker]

 

The charts both of you have posted have similar chances of coming to fruition.

 

I didn't post the chart with the expectation that it would become reality.

Edited December 4, 2014 by knocker

[Panayiotis]

I find that post quite extraordinary. Some weird speculation regarding the Azores high, based on one chart, and ignoring the potential storm. And I'm no doubt being a bit thick but what does, "if that low exiting the US becomes more negatively tilted" mean?...

Charts courtesy weatherbell

I dont see why I cant discuss something else apart from the potential storm, but anyway, I was eluding to something like this (as an example) , if we get more amplification and if the PV weakens over Greenland eg UKMO ...

Edited December 4, 2014 by Panayiotis

[chionomaniac]

I think that it is worth pointing out that there is no rule to what can or cannot be discussed in this thread as long as it is model related and relevant and pertinent to the thread. Whether that be the chance of a chart with wintry potential at day 10 or a storm at day 2.

 

If what someone else is discussing is not what you would like to discuss regarding the output, then just let that post pass......

[johnholmes]

I dont see why I cant discuss something else apart from the potential storm, but anyway, I was eluding to something like this (as an example) , if we get more amplification and if the PV weakens over Greenland eg UKMO ...

 

 

Of course you can discuss it but already in your summation of the charts you showed you have two IFS out on 23 December? It is fine to speculate but that is really all it is when you require 2 ifs for perhaps your summary to occur. Perhaps you might discuss how likely your 2 ifs are and why then we can discuss that by all means?

[MR EXTREMES]

I dont see why I cant discuss something else apart from the potential storm, but anyway, I was eluding to something like this (as an example) , if we get more amplification...

The ukmo outputs recently have certainly been a little behind in terms of its outputs not totally but enough to cause some skepticism.

The chart posted shows a nice northerly which would indeed benefit a larger swathes of the uk.

But at this moment in time the weather in the states and the vortex over Greenland it's a waiting game.

It would be nice to resume wave activity into the stratosphere but at the moment we're stuck with a pattern of which we are seeing.

But I certainly agree this December has started of dam chilly even here in the south it's cold good to see some frost and wintry stuff even if it's in the north.

The ao index is showing signs of wanting to go negative but I really don't see a blast from the east or northeast this side of Christmas.

But I do see a slow progression into January for a better chance for the rest of the uk if the ao goes as expected.

Although there are little changes creeping into the models over the past few days but I personally am not taking anything beyond t96 as gospel the erratic nature of the weather right now is most certainly going to throw out some chaotic charts and this will continue for awhile yet I suspect as the stuck pattern is a slow mover for now.

But wintry it is and better than last year in terms of a messy vortex although this is still dictating our weather for now.

Edited December 4, 2014 by Polar Maritime
To remove personal remark.

[knocker]

I think that it is worth pointing out that there is no rule to what can or cannot be discussed in this thread as long as it is model related and relevant and pertinent to the thread. Whether that be the chance of a chart with wintry potential at day 10 or a storm at day 2.

 

If what someone else is discussing is not what you would like to discuss regarding the output, then just let that post pass......

 

Okay but surely it's reasonable to ask what "if that low exiting the US becomes more negatively tilted" means in meteorological terms. Some of us are on a learning curve so to appreciate a post one has to understand it.

[Mucka]

So one or two have post anomaly charts for indicators but my take is that we will still likely be in a much more favourable position around mid month for a cold pattern setting up (not the same as saying a cold pattern will set up at mid month, that would be too optimistic even for me at this point, we are looking last 3rd of month at best)

I am basing that off ECM anomaly charts and to a lesser extent on GFS ensembles, not single GFS operational runs or even ECM operational runs.

John posted the NOAA chart earlier which admittedly are not that promising with a fairly shallow trough, fairly run of the mill zonal pattern by day 10.

But ECM has always been more promising with the AH being squeezed west and the mean low anomalies dropping away from Canad/Greenland and a deeper trough into Europe with a displaced AH suggesting a colder zonal flow with a more northerly element within the ensembles. If someone can post the postage stamps from this morning then I would expect many to show a trough somewhere just E/NE of the UK with a displaced AH and low pressure running down its Eastern flank into the trough.

The split signal is that other forecasts have the AH ridging much more strongly forcing low pressure on a flatter track and a standard zonal picture setting up.

Both would be rather unsettled but offer very different weather types and prospects for the rest of December.

 

Fortunately this can be illustrated by placing this mornings ECM ens mean pressure anomaly alongside this afternoons GFS Op anomaly for the same period.

 

 

Chalk and cheese with ECM ensembles pointing toward a very different day 10 pressure pattern to GFS Op. We really need ECM ensembles to win this one and strengthen that signal and get ECM Op on board. I'm not saying the ECM 10 day anomalies are perfect, there a re a few adjustments we would want to see, with the trough further South and more elongated for example but compared to this afternoons GFS it is glorious.

So hoping that ECM is correct then we can see by day 10 we could be a true cold zonal flow (Not deep cold entrenched air, still transient but colder with more snow probabilities than the current spell offers. Not only that but with the low heights removed from Canada Greenland, troughing into Europe and a displaced AH giving opportunity of more amplification and a strong Atlantic ridge forming then that would not be a bad spot to be in come mid month.

 

I have been following these charts and developments in the 5 day time frame and while ECM anomalies have not become more favourable they have stayed pretty stable and it is GFS that has ever so slowly been thinking about setting up a cold zonal pattern I describe. As you can see this afternoons Op goes for the AH to ridge in strongly and flatten the pattern rather than drop the trough SE and displace it but as noted this morning its ensembles are starting to wobble around.

 

Look for this afternoons GFS ensembles to show a less prominent AH ridging into the UK around day 5 and therefore again around day 7/8 and a deeper trough.

When I say something is afoot it is actually in the day 5 range with the handling of the Greenland PV so we should know pretty soon if we are going to get flatter zonal pattern or something more wintry (though still unsettled) with better future prospects.

Edited December 4, 2014 by Mucka

[nick sussex]

Of course you can discuss it but already in your summation of the charts you showed you have two IFS out on 23 December? It is fine to speculate but that is really all it is when you require 2 ifs for perhaps your summary to occur. Perhaps you might discuss how likely your 2 ifs are and why then we can discuss that by all means?

But isn't a lot of weather about IF's? Panayiotis was discussing possibilities and this thread would become very stale if people are being told what they can and can't discuss.

 

His post was model related and it doesn't matter how many IF's is needed, are we now going to embark on a three IF's and you're out rule, or  are you allowed one IF or two just how many IF's are acceptable.

 

For example the UKMO T144hrs chart, what if the shortwave runs into the base of the UK trough, the low over the ne USA runs ne, what happens over Greenland if this happens, oops too many IF's.

 

I'm not being difficult for the sake of it but just people should be welcome and feel happy to post in here as long as its model related.

[johnholmes]

But isn't a lot of weather about IF's? Panayiotis was discussing possibilities and this thread would become very stale if people are being told what they can and can't discuss.

 

His post was model related and it doesn't matter how many IF's is needed, are we now going to embark on a three IF's and you're out rule, or  are you allowed one IF or two just how many IF's are acceptable.

 

For example the UKMO T144hrs chart, what if the shortwave runs into the base of the UK trough, the low over the ne USA runs ne, what happens over Greenland if this happens, oops too many IF's.

 

I'm not being difficult for the sake of it but just people should be welcome and feel happy to post in here as long as its model related.

 

not at all Nick I did suggest IF he explains why he feels those ifs are probable, give his reasons and what may follow then we can discuss those theories. That type of post should stimulate a genuine discussion amongst those of us truly interested in the weather.

I perhaps could do something like that with my favourite anomaly charts, I do it to my own data files on my pc, and it can make for interesting times?

[Mucka]

A much different story on the 12z GFS with a much more amplified high over the Atlantic at 168hrs compared to the 06z, could we be seeing an attempt from the GFS to ridge that high up and over the UK forming a Scandi high? Not on this run, but it could be a new trend to look out for over the coming days if that low exiting the US becomes more negatively tilted...

PS: I have come out of hibernation especially with snow on the horizon for some! Interesting winter ahead...

 

 

That is why I love these threads. Perfectly valid observation you make but I just wrote a post hoping for the opposite to occur 

Yes of course if we get so much amplification that we have that opportunity I will take it, it is possible but if the AH ridges in I see a flat zonal pattern setting up being far more likely which is why I would rather the opposite occur and the trough flatten and displace the AH earlier in the output so the trough can sink Se rather being forced E/NE, 

Either are valid possibilities but what we don't want is this afternoons GFS Op  middle ground. 

 

Edit: Just glanced through GFS ensembles for day 10 and still too much of this

 

 

And not enough of this.

 

Edited December 4, 2014 by Mucka

[pointswest]

Can I just say..welcome back  Panayiotis. I cannot post charts or comment on this thread because I am still learning and it's sure taking a long time but I have been following this forum for a very long time and find your and many others knowledge very helpful.

Edited December 4, 2014 by pointswest

[nick sussex]

not at all Nick I did suggest IF he explains why he feels those ifs are probable, give his reasons and what may follow then we can discuss those theories. That type of post should stimulate a genuine discussion amongst those of us truly interested in the weather.

I perhaps could do something like that with my favourite anomaly charts, I do it to my own data files on my pc, and it can make for interesting times?

I know you love those anomaly charts so yes why not .  Sometimes trying to get cold into the UK is like pulling teeth so its very natural to be more interested in colder synoptics at this time of year.

 

It's the same in summer with extreme heat, I think because of the UK's temperate climate people are always drawn to the extremes.

Edited December 4, 2014 by nick sussex

[Smiler1709]

The pressure is certainly rising over Greenland, I've noticed on the last few gfs runs that the ridging in the Atlantic is moving further north on every run, now I'm still learning with all this model stuff but maybe the gfs is picking up a trend to send high pressure up into Greenland and put us in a blocked pattern.

I've seen a few posters talking about a pattern change come mid month onwards, trending to Northern blocking. Maybe were just starting to see these changes. With 1040 pressure over Greenland it wouldn't take much for the high pressure in the Atlantic to ridge up and create a good block over the artic.

Here's hoping anyway

[BLAST FROM THE PAST]

A much different story on the 12z GFS with a much more amplified high over the Atlantic at 168hrs compared to the 06z, could we be seeing an attempt from the GFS to ridge that high up and over the UK forming a Scandi high? Not on this run, but it could be a new trend to look out for over the coming days if that low exiting the US becomes more negatively tilted...

PS: I have come out of hibernation especially with snow on the horizon for some! Interesting winter ahead...

 

P

Yes indeed more amplification is showing and we may well get even more too...but apparently December has been taken care of?.

Re the negative tilt, I read into it that you mean that would enhance the northward ridge of the AZH with less chance of the Atlantic riding over the top/breaking through and flattening the pattern?  For me more chance than December being written off at this point.

 

For me, we are entering interesting solar/lunar period...its an interesting start to the 12z

 

BFTP

[knocker]

P

Yes indeed more amplification is showing and we may well get even more too...but apparently December has been taken care of?.

Re the negative tilt, I read into it that you mean that would enhance the northward ridge of the AZH with less chance of the Atlantic riding over the top/breaking through and flattening the pattern?  For me more chance than December being written off at this point.

 

For me, we are entering interesting solar/lunar period...its an interesting start to the 12z

 

BFTP

 

Fine so what is meant by negative tilt in meteorological terms?

I know you love those anomaly charts so yes why not .  Sometimes trying to get cold into the UK is like pulling teeth so its very natural to be more interested in colder synoptics at this time of year.

 

It's the same in summer with extreme heat, I think because of the UK's temperate climate people are always drawn to the extremes.

 

Deep depressions with destructive wind speeds are also examples of extremes. And given the nature of the beast I would have thought far more relevant in the short term. But, yes everyone is entitled to their own priorities.

Edited December 4, 2014 by knocker

[Polar Maritime]

I've just moved a few posts, Can we only discuss what the 'Model Outputs' are showing as per thread title. 

 

Many Thanks, PM

Edited December 4, 2014 by Polar Maritime

[Ali1977]

A few FI members in the ensembles starting to show a little more interest, not gold but WAA heading into Greenland on a few.

[chionomaniac]

Okay but surely it's reasonable to ask what "if that low exiting the US becomes more negatively tilted" means in meteorological terms. Some of us are on a learning curve so to appreciate a post one has to understand it.

 

 

Fine so what is meant by negative tilt in meteorological terms?

 

Deep depressions with destructive wind speeds are also examples of extremes. And given the nature of the beast I would have thought far more relevant in the short term. But, yes everyone is entitled to their own priorities.

A negatively tilted trough is one where the long axis of the trough is from a NW to SE direction, whereas a positively tilted trough is one that has a SW to NE long axis. The negatively tilted trough is more likely to undercut a block whereas the positively tilted trough is more likely to ride over a block.

 

Edit this is better demonstrated with charts but I am unable to at work.

Edited December 4, 2014 by chionomaniac

[SMU]

Okay but surely it's reasonable to ask what "if that low exiting the US becomes more negatively tilted" means in meteorological terms. Some of us are on a learning curve so to appreciate a post one has to understand it.

 

Hi Knocker-

 

The difference between a posive tilted low & a negative tilted low is the expected windflow in the eastern quadrant of the low & also the potential for trough disruption relating to how much ridging there is ahead of the low-

You dont need the jet chart to observe them- more so the 500's

 

A positive tilted low has a 'positive' tilt to the Axis - so the southern & SE quadrant will always support strong westerly / SW winds - & with this showing in a model you would suspect that any ridging north from a lower latittude high pressure would be supressed. If you image a low is square ( for a moment ) then a positive tilited low always has the NE edge leading ahead of the SE edge leading-

the UKMO has a positive tilted low at 96 over SE greenland-

http://www.meteociel.fr/ukmo/runs/2014120412/UN96-21.GIF?04-17

Note the azores ridge is getting surpressed,

 

On the other side of the coin a negative tilted low demonstrates that the jet is amplified more & is often split ahead of a high pressure that is building.

We often term lows that are negative tilted & moving SE 'slider lows'

 

heres a negative tilted low last month-

http://modeles.meteociel.fr/modeles/gfs/archives/gfsnh-2014111400-0-6.png

see how the SE quadrant is leading & the NW quadrant is further west that the SW quadrant -  Also the jet at that time is split-

http://modeles.meteociel.fr/modeles/gfs/archives/gfs-2014111400-5-6.png

So thats classic trough disruption territory-

 

1 day later-

http://modeles.meteociel.fr/modeles/gfs/archives/gfsnh-2014111500-0-6.png  Seperation-

2 days later

http://modeles.meteociel.fr/modeles/gfs/archives/gfsnh-2014111600-0-6.png full trough disruption.

 

 

So when people are referring to negative tilted lows thats usually the precursor of a low thats going to disrupt & support blocking close to the NE flank..

Obviously the disruption is actually a result of the block, however its the image of the shape changing to neg tilted that shows how strong a high pressure is before the model then goes onto to show the high building North westwards...

 

regards

S