Model Output Discussion

[reef]

A new thread for the upcoming 12z GFS run. Please continue. :lol:

[glasgow-guy]

A new thread for the upcoming 12z GFS run. Please continue. :lol:

I keep reading about dates 14 15 16 17 of December for the possible start of this cold spell when if any are we likely to get confirmation?

which GFS run is likely to provide answers?. before this forum goes into melt down

I understand further GFS runs could downgrade any potential trough

I am not a expert at all this weather speak I am still learning but if some one could give some possible insight in a way us non technical

enthusiasts can understand would be of great help

thanks in advance.

Glasgow-guy :lol:

Edited December 6, 2009 by glasgow-guy

[shuggee]

Experience tells us that not until 4 days beforehand i.e. at T+96 will we know anything for certain gg :lol:

[glasgow-guy]

Experience tells us that not until 4 days beforehand i.e. at T+96 will we know anything for certain gg :lol:

thanks shuggee. reading these forums sometimes may as well be written in Chinese but I always appreciate any simplified explanation

of discussions from time to time

thanks

glasgow-guy :lol:

Edited December 6, 2009 by glasgow-guy

[reef]

I keep reading about dates 14 15 16 17 of December for the possible start of this cold spell when if any are we likely to get confirmation?

which GFS run is likely to provide answers?. before this forum goes into melt down

I understand further GFS runs could downgrade any potential trough

I am not a expert at all this weather speak I am still learning but if some one could give some possible insight in a way us non technical

enthusiasts can understand would be of great help

thanks in advance.

Glasgow-guy :lol:

The truth of it is that the models are generally very accurate at under 96 hours out and very little change occurs to the general pattern after that. However, the problem in the UK is that a mere change of a couple of hundred miles can mean the difference between heaps of snow and nothing at all. We're also directly affected by what happens in the Greenland area, which has traditionally been quite a diffcult area for the models to handle.

You'll get the same small changes in all of the setups that the weather can throw at us in the UK, its just none are quite so noticeable as snow or no snow. :lol:

[pyrotech]

I keep reading about dates 14 15 16 17 of December for the possible start of this cold spell when if any are we likely to get confirmation?

which GFS run is likely to provide answers?. before this forum goes into melt down

I understand further GFS runs could downgrade any potential trough

I am not a expert at all this weather speak I am still learning but if some one could give some possible insight in a way us non technical

enthusiasts can understand would be of great help

thanks in advance.

Glasgow-guy :lol:

GFS is classed by most on here as fi (fantasy island) somewhere between between 96hrs / 120hrs onwards. It can be acurate but especially with cold you can see it often do a full circle and show a complete different scenario. Some runs are also done with more data and so likely to be more on the ball than others.

People have their own preference to a models reliability, GFS, ECM UKMO etc.

The best signs at the fi levels are for consistancy with one model showing same scenario run after run and better still models all showing similar charts.

The short time frame 120hrs and less i prefer fax charts but it comes down to personal preference.

People on here who give good anyalys are John Holmes and Teits amongst others where the analysis of the models are given in a fairly unbiased read.

Hope that helps

Edited December 6, 2009 by pyrotech

[winter watcher]

The truth of it is that the models are generally very accurate at under 96 hours out and very little change occurs to the general pattern after that. However, the problem in the UK is that a mere change of a couple of hundred miles can mean the difference between heaps of snow and nothing at all. We're also directly affected by what happens in the Greenland area, which has traditionally been quite a diffcult area for the models to handle.

You'll get the same small changes in all of the setups that the weather can throw at us in the UK, its just none are quite so noticeable as snow or no snow.

Very true reef the way that i see it these days i do not believe in the so called christmas pudding. However their is signs off our earth warming up but i am yet to be convinced. But what i do have a rule off saying to myself when we see cold patterns start to emerge is that "we are a very small island" and this ties in with your point and a few others a couple off hundred miles makes all the diffrence. I do believe however that this potential cold spell will go our way and i am very much likeing the near future state off the pv.

[Snowyowl9]

Countryfile going for a change later this week to at least HP so foggy conditions and some frost,so a patteren change we are heading for,I`m taking note of John Holmes aswell.

All this talk of inversion cold,nobody was any the wiser years ago a cold easterly just means cold whatever the upper air is in winter and snow grains,sometimes freezing drizzle or just plain drizzle/low cloud :lol:

Better than mild atlantic SW-lys anyday. :lol: There is a disadvantage you get little or no sun.

The differences between ECM and UKMO at the same time.

http://91.121.93.17/pics/Rukm1441.gif

http://91.121.93.17/pics/Recm1441.gif

[Glacier Point]

As John Holmes has highlighted, the wavelengths evolving are likely to aid retrogression.

A clear 3-wave pattern is being advertised by the modelling. Once in place, this is likely to become very slow moving.

ECM and GFS mean height anomalies:

http://www.meteo.psu...0z/hgtcomp.html

GFS 00z ensemble mean height anomaly (unchanged from yesterday):

A fait bet then that December will feature a 3-wave pattern with upper lows in the central Pacific / Aluetians, Atlantic and Russia. For years with a similar 3-wave pattern in December:

Rolled forward, these give us an idea of where the pattern might progress, important in terms of benchmarking what might be an outlier model run:

This means that we are looking at a solid -NAO signal evolving. Therefore, be very scepitical of any run that goes significantly against this pattern in the longer term.

The Netweather CFS update for January also shows a huge -NAO pattern.

Edited December 6, 2009 by Glacier Point

[Anti-Mild]

Great stuff GP, particularly the composite for January - that indicates a synoptic pattern not seen for ages, and not at all by some of the younger members of the forum. It also ties in nicely with your forecast for the winter. Possibly a very interesting festive period ahead in terms of the weather!

[chionomaniac]

As John Holmes has highlighted, the wavelengths evolving are likely to aid retrogression.

A clear 3-wave pattern is being advertised by the modelling. Once in place, this is likely to become very slow moving.

ECM and GFS mean height anomalies:

http://www.meteo.psu...0z/hgtcomp.html

GFS 00z ensemble mean height anomaly (unchanged from yesterday):

A fait bet then that December will feature a 3-wave pattern with upper lows in the central Pacific / Aluetians, Atlantic and Russia. For years with a similar 3-wave pattern in December:

Rolled forward, these give us an idea of where the pattern might progress, important in terms of benchmarking what might be an outlier model run:

This means that we are looking at a solid -NAO signal evolving. Therefore, be very scepitical of any run that goes significantly against this pattern in the longer term.

The Netweather CFS update for January also shows a huge -NAO pattern.

Everything is pointing that way.

GP, I see that the tendency for AAM is moving in the right direction. Do you see us entering GWO phase 5 anytime soon or do you think that we will have to go through another orbit first? The MJO couldn't be better positioned with a promising forecast.

[03jtrickey]

A fait bet then that December will feature a 3-wave pattern with upper lows in the central Pacific / Aluetians, Atlantic and Russia.

...

This means that we are looking at a solid -NAO signal evolving. Therefore, be very scepitical of any run that goes significantly against this pattern in the longer term.

Thanks GP. Is there any chance that you or another experienced model watcher could explain in more simple terms what this pattern is likely to bring in terms of UK weather over the upcoming weeks?

Looking at the chart you mentioned, I'm taking that to mean high heights over Greenland/Svalbard/Scandi/UK and lower over Russia. http://www.meteo.psu.edu/~gadomski/ECMWF_0z/hgtcomp.html

Does that imply that the UK weather will be mainly high pressure dominated from 8-10 days?

[kold weather]

Thats something to watch GP, hopefully by then the GWO will be in a better phase to support it as well.

I think for the next 10-14 days we will see a much below normal model confidence for synoptic evolutions because you've got a pretty potent jet still, a strong upper trough in the Atlantic that will eventually try and force itself back east as soon as a strong jet streak swings round it, but you've got a clear -ve AO present and a big signal for a Scandinavian high that will attempt to block anything in the Atlantic. These sorts of patterns often end up seeing one month that is very cold followed by another month that could be very mild so its a tough one to call. Does remind me very much of a 60s/80s type pattern though that the N.Hemisphere is trying to develop.

Synoptically, I agree with GP there is a real signal for a -ve NAO as we roll things forwards towards Jan, and if thats the case I think snow chances are probably higher then normal thanks to an active jet...I think eventually you'll get a cutoff low try and dive SE again and when that happens then its really game on.

[winter watcher]

As John Holmes has highlighted, the wavelengths evolving are likely to aid retrogression.

A clear 3-wave pattern is being advertised by the modelling. Once in place, this is likely to become very slow moving.

ECM and GFS mean height anomalies:

http://www.meteo.psu...0z/hgtcomp.html

GFS 00z ensemble mean height anomaly (unchanged from yesterday):

A fait bet then that December will feature a 3-wave pattern with upper lows in the central Pacific / Aluetians, Atlantic and Russia. For years with a similar 3-wave pattern in December:

Rolled forward, these give us an idea of where the pattern might progress, important in terms of benchmarking what might be an outlier model run:

This means that we are looking at a solid -NAO signal evolving. Therefore, be very scepitical of any run that goes significantly against this pattern in the longer term.

The Netweather CFS update for January also shows a huge -NAO pattern.

Hi GP how are you? First off great positive post if your a coldie fan. Just a quick question from me though can you see this potential cold spell which you progged some weeks ago potentialy mergeing together with your above comments? For example a long cold outbreak or are you thinking along the lines off a breif colder period and then the main source off cold say mid january?

[Cecil Hogmanay Melchett]

As John Holmes has highlighted, the wavelengths evolving are likely to aid retrogression.

A clear 3-wave pattern is being advertised by the modelling. Once in place, this is likely to become very slow moving.

ECM and GFS mean height anomalies:

http://www.meteo.psu...0z/hgtcomp.html

GFS 00z ensemble mean height anomaly (unchanged from yesterday):

A fait bet then that December will feature a 3-wave pattern with upper lows in the central Pacific / Aluetians, Atlantic and Russia. For years with a similar 3-wave pattern in December:

Rolled forward, these give us an idea of where the pattern might progress, important in terms of benchmarking what might be an outlier model run:

This means that we are looking at a solid -NAO signal evolving. Therefore, be very scepitical of any run that goes significantly against this pattern in the longer term.

The Netweather CFS update for January also shows a huge -NAO pattern.

Great post,

Thanks for sharing GP.

:lol:

[Cecil Hogmanay Melchett]

GP,just a quickie.

Any thoughts on el nino and if we are seeing any signs of engagement?

[Glacier Point]

Thanks all.

I'lly try an asnwer all those questions in one.

Synoptically, we have a view how January should pan out. This involves the GWO responding to an increase in angular momentum over the next 2-4 weeks as poleward fluxing of the forward inertia generated by recent (ongoing) tropical convection, much of which is now located towards the Dateline supporting a -NAO signal. In theory this wil send the GWO from phase 4 (where it is now and likley to remain over the next 7 days or so) towards low amplitude phases 5-6-7-0. This is critical as the composites for these phases in January:

Phase 5

Phase 6

Phase 7

Phase 8/0

So we are looking for an evolution shown by the anlogs for the 3-wave pattern and GWO which would be expected for the Atlantic to undercut any block forming over Scandinavia aiding retrogression of the high back towards southern Greenland. This is a sign that El Nino is influcing the pattern although the crucial thing here is that overall angular momentum is low and momentum rise is from a low base.

In laymens terms, the weather to be expected would be for cold an frosty for a time, turning colder with the easterly stiffening but also the Atlantic trying to make inroads from a southerly tracking jet so milder interludes may just be possible although the boundary between cold and mild air masses is not possble to call at this range. Thereafter, we should move towards winds coming more from the north-east and then north bringing the colder weather back with wintry potential during January although as the GWO composites suggest, there is likely to be a lot of high pressure around bringing dry and frosty weather.

The crucial thing to watch over the next few weeks is just how much cold air is trapped over mainland Europe as this will have direct implications for us during January.

Edited December 6, 2009 by Glacier Point

[swfc]

Thanks all.

I'lly try an asnwer all those questions in one.

Synoptically, we have a view how January should pan out. This involves the GWO responding to an increase in angular momentum over the next 2-4 weeks as poleward fluxing of the forward inertia generated by recent (ongoing) tropical convection, much of which is now located towards the Dateline supporting a -NAO signal. In theory this wil send the GWO from phase 4 (where it is now and likley to remain over the next 7 days or so) towards low amplitude phases 5-6-7-0. This is critical as the composites for these phases in January:

Phase 5

Phase 6

Phase 7

Phase 8/0

So we are looking for an evolution shown by the anlogs for the 3-wave pattern and GWO which would be expected for the Atlantic to undercut any block forming over Scandinavia aiding retrogression of the high back towards southern Greenland. This is a sign that El Nino is influcing the pattern although the crucial thing here is that overall angular momentum is low and momentum rise is from a low base.

In laymens terms, the weather to be expected would be for cold an frosty for a time, turning colder with the easterly stiffening but also the Atlantic trying to make inroads from a southerly tracking jet so milder interludes may just be possible although the boundary between cold and mild air masses is not possble to call at this range. Thereafter, we should move towards winds coming more from the north-east and then north bringing the colder weather back with wintry potential during January although as the GWO composites suggest, there is likely to be a lot of high pressure around bringing dry and frosty weather.

The crucial thing to watch over the next few weeks is just how much cold air is trapped over mainland Europe as this will have direct implications for us during January.

Great post.Just a quick question.What is the importance of warm air been pumped up into the north.???.Back to the models and dry and cool looks the order of the day to me which will be most welcome

[Methuselah]

I really hope so, GP! Whether it does or doesn't pan-out that way, your insight (together with JH's et al) is worth all (my!) comprehension problems!!

[ChartViewer]

Thanks all.

I'lly try an asnwer all those questions in one.

Synoptically, we have a view how January should pan out. This involves the GWO responding to an increase in angular momentum over the next 2-4 weeks as poleward fluxing of the forward inertia generated by recent (ongoing) tropical convection, much of which is now located towards the Dateline supporting a -NAO signal. In theory this wil send the GWO from phase 4 (where it is now and likley to remain over the next 7 days or so) towards low amplitude phases 5-6-7-0. This is critical as the composites for these phases in January:

Phase 5

Phase 6

Phase 7

Phase 8/0

So we are looking for an evolution shown by the anlogs for the 3-wave pattern and GWO which would be expected for the Atlantic to undercut any block forming over Scandinavia aiding retrogression of the high back towards southern Greenland. This is a sign that El Nino is influcing the pattern although the crucial thing here is that overall angular momentum is low and momentum rise is from a low base.

In laymens terms, the weather to be expected would be for cold an frosty for a time, turning colder with the easterly stiffening but also the Atlantic trying to make inroads from a southerly tracking jet so milder interludes may just be possible although the boundary between cold and mild air masses is not possble to call at this range. Thereafter, we should move towards winds coming more from the north-east and then north bringing the colder weather back with wintry potential during January although as the GWO composites suggest, there is likely to be a lot of high pressure around bringing dry and frosty weather.

The crucial thing to watch over the next few weeks is just how much cold air is trapped over mainland Europe as this will have direct implications for us during January.

Fantastic post GP...Thanks for sharing that...Whats it mean for us....Around 700 Model runs of shredded nerves Upgrades Downgrades cold mild etc.....-5 -10 then Bartletts Euro Highs being progged......What a superb Winter we are in for on here

Edited December 6, 2009 by ChartViewer

[nick sussex]

Just a quick note regarding warm air advection for those interested, heres a link explaining this:

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/af/adv/wadv.rxml

In the current set up we need this going into the arctic to help build pressure,the cold air then has to go somewhere and heads south on the eastern flank of the high, this is just a quick explanation not wanting to bore everyone!

Edited December 6, 2009 by nick sussex

[winter watcher]

Well 12z just about to roll out. For some reason i feel this run will be very important so heres hopeing all goes well.

[Dingwantssnow]

I Always enjoy Reading GP's posts. Started back on these forums in october with the doom and gloom but it was GP's comments that always gave me hope for this comming winter. And what he has said previously has started comming to fruition with the recent model outputs.

Are we really on the verge of somthing special this year?? I have no idea. Last year was a wash out for me we had maybe 1-2 days of snow that never reached more than an inch whereas other regions got the pasting of the century(if you believe the news).

With my extremly limited knowledge (practically none:whistling:) Am i right to believe that its been a fair while, years, since we have this much potential for wintryness?? Or am i merely dreaming:lazy:

I just want, for once, to get up one morning this winter and look outside to see 3 foot of snow lying.....mainly so i dont have to go to work and for it to last more than a day....ohhh the days when that happened:cray:

[Devon-Nelly]

What a wonderfull post GP, i hope to be as knowledgeable about all these factors and players in global weather one day.

Looks as though the models are going to go through big swings an roundabouts with this new data, how long do you think a negative NAO signal can last for?

[weather eater]

12z coming out and you could hear a pin drop.