Model Output Discussion - 28th November

[nick sussex]

It's now down to the UKMO to save us!

That output doesn't eject energy east off the now to be called SOSPOV (Spawn of Satan Piece of Vortex)in ne Canada.

This setting up there makes any route to cold much more difficult, the UKMO has a more amplified upstream pattern, the ECM is similar in pattern at 144hrs but flatter upstream after 144hrs and then you see too much energy spill east.

The GFS tries to build a little ridge in the Atlantic later but reverts to zonal dirge in its lower resolution output.

Going back to the UKMO it ejects energy more se off SOSPOV and thats what gives us a chance.

We also have to add in the complication of the low moving up from the south into the Atlantic and when and how the models phase that with energy coming out of the USA.

Edited November 29, 2012 by nick sussex

[snowmadchrisuk]

Is this the time to remind everyone that low res gfs op and gefs control are running at similar resolutions, taking into account the number of vertical levels on each one? That probably means they are both worthless!!

a small step back to the west overall this morning but not by too much. One wonders if we are looking at a similar solution to last week eith the trough eventually disrupting just to our east and becoming cut off to our se. Europe colder in a weeks time............

Do you know what resolution the GEM ensembles are ? The Gem Control is showing pretty much the same as GFS Control . EDIT it's ok just checked there 1deg same as GFS

Edited November 29, 2012 by snowmadchrisuk

[Richard Fearn]

hi guys don't know much about reading into the charts (so dont shout at me lol ), but i think i said this last year about the 528 dam needs to be established over the uk and into france before any large snow event will happen , this happened a few years ago now,the dam is there but waxes and wains because of lows rattling in off the atlantic which was a similar set up last year ,and that it drags in milder air, might be localised wintery events but nothing mounting up to much, i think the set up for the winter , wet and cold, hope im wrong love a nice wintery scene

[snowmadchrisuk]

hi guys don't know much about reading into the charts (so dont shout at me lol ), but i think i said this last year about the 528 dam needs to be established over the uk and into france before any large snow event will happen , this happened a few years ago now,the dam is there but waxes and wains because of lows rattling in off the atlantic which was a similar set up last year ,and that it drags in milder air, might be localised wintery events but nothing mounting up to much, i think the set up for the winter , wet and cold, hope im wrong love a nice wintery scene

Regarding the 528 dam line you are correct , If you get a Solid GL High or Scandi High for more than a few days , the 528 Damline should come ... Fingers crossed for December. .

[Glacier Point]

TEITS you smelling that easterly ?

Very interesting situation at the moment. ECM and GEFS picking up on the height rises to the far NE Atlantic. As long as the residual vortex is clamped to the west of Greenland we'll see bits of energy cutting their way SE preventing any further building.

However, trending around t168 suggests cut off lows developing in the mid and western Atlantic and ridge development towards southern Greenland (strong signal from GEFS around t168 onwards). That shuts down the flow of energy and allows the ridge to the NE to build.

GEFS also continuing to do 2 interesting things:

1) shift the residual vortex back towards the Canadian interior which further increases the chances of block development;

2) builds a large high pressure cell over Siberia as the vortex their is relaxed.

With the GWO potentially swinging back to a big phase 5 projection (composite below), interesting times ahead. The mean anomalous ridge to our west looks a safe bet, as does the trough solution over Europe. I think a build in pressure between Iceland and Scandinavia week 2 looks very plausible.

Edited November 29, 2012 by Glacier Point

[Frosty.]

It's now down to the UKMO to save us!

That's not strictly true though is it? the gfs and ecm show a mostly chilly spell apart from monday in the south, and they both show a cold blast through the second half of next week followed by a very cold frosty but fine weekend. Beyond that is pure speculation. Besides, as the ukmo has been forced to backtrack a lot recently, just proves it's as untrustworthy as the others.

Edited November 29, 2012 by Frosty039

[nick sussex]

Differences discussed this morning by NOAA in the USA regarding the speed of that deep low crossing the USA:

TWIN POLAR VORTICES NEAR SOUTHERN ALASKA AND OVER NUNAVUT/THE

CANADIAN ARCHIPELAGO THROUGH THE MEDIUM RANGE PERIOD SHOULD KEEP

THE FLOW PATTERN PROGRESSIVE ACROSS THE MID-LATITUDES OF THE

EASTERN PACIFIC AND NORTH AMERICA THIS PERIOD. THE BIG QUESTION

IS HOW PROGRESSIVE. WITH THE INITIAL LONGWAVE TROUGH MOVING

THROUGH NORTH AMERICA, THE 00Z GFS IS THE QUICKEST TO THE MOVE IT

EASTWARD WHILE THE 00Z UKMET IS THE SLOWEST/MOST SOUTHWEST

Those differences between the GFS and UKMO go along way to explaining their different outputs at 144hrs.

[nick sussex]

That's not strictly true though is it? the gfs and ecm show a mostly chilly spell apart from monday in the south, and they both show a cold blast through the second half of next week followed by a very cold frosty but fine weekend. Beyond that is pure speculation. Besides, as the ukmo has been forced backtrack a lot recently, just proves it's as untrustworthy as the others.

I was being dramatic!

The ECM has another go a bit later in its run to develop something a bit more interesting so might get there, the GFS operational output also tries but doesn't quite get there.

So IMO two opportunities shown in the models today, its the UK so how many chances will there be.

The time for action is nigh, the NH pattern does show potential although that PV in ne Canada isn't helping matters, we'll see but it would be good to see something concrete happen within the next ten days.

[weather eater]

Differences discussed this morning by NOAA in the USA regarding the speed of that deep low crossing the USA:

TWIN POLAR VORTICES NEAR SOUTHERN ALASKA AND OVER NUNAVUT/THE

CANADIAN ARCHIPELAGO THROUGH THE MEDIUM RANGE PERIOD SHOULD KEEP

THE FLOW PATTERN PROGRESSIVE ACROSS THE MID-LATITUDES OF THE

EASTERN PACIFIC AND NORTH AMERICA THIS PERIOD. THE BIG QUESTION

IS HOW PROGRESSIVE. WITH THE INITIAL LONGWAVE TROUGH MOVING

THROUGH NORTH AMERICA, THE 00Z GFS IS THE QUICKEST TO THE MOVE IT

EASTWARD WHILE THE 00Z UKMET IS THE SLOWEST/MOST SOUTHWEST

Those differences between the GFS and UKMO go along way to explaining their different outputs at 144hrs.

Could be something in that Nick, certainly the GFS looks way more progressive this morning compared to the ECM and the UKMO.

[chionomaniac]

TEITS you smelling that easterly ?

Very interesting situation at the moment. ECM and GEFS picking up on the height rises to the far NE Atlantic. As long as the residual vortex is clamped to the west of Greenland we'll see bits of energy cutting their way SE preventing any further building.

However, trending around t168 suggests cut off lows developing in the mid and western Atlantic and ridge development towards southern Greenland (strong signal from GEFS around t168 onwards). That shuts down the flow of energy and allows the ridge to the NE to build.

GEFS also continuing to do 2 interesting things:

1) shift the residual vortex back towards the Canadian interior which further increases the chances of block development;

2) builds a large high pressure cell over Siberia as the vortex their is relaxed.

With the GWO potentially swinging back to a big phase 5 projection (composite below), interesting times ahead. The mean anomalous ridge to our west looks a safe bet, as does the trough solution over Europe. I think a build in pressure between Iceland and Scandinavia week 2 looks very plausible.

I think that that look plausable (stratospherically) with the trend of the PV relocating to the Canadian sector but around days 10-14 - probably not sooner. ( Latest 00Z GFS strat charts from day 10 I suspect may be outliers - but still show stretching of the vortex at the end)

[SMU]

Morning All-

Encouraging times this morning, especially again from the UKMO, which has generally been performing well.- everything edging west with the milder 0c incursion being shortened at both ends-

The UKMO dives that low well however holds the system stationary over southern greenland allowing the ridge to build ahead of it..

A lot of people reporting that the atlantic would come screaming back in & flatten off, however im still convinced the slider pattern is a sign of things to come.

S

[Gibby]

Good morning. Here is the latest report on the events of the 00z output from GFS, UKMO, GEM and ECM for today Thursday November 29th 2012.

All models show a cold but slack northerly flow down over the UK with a weak disturbance approaching the far west of the British Isles later. This pattern remains more or less in place until Monday when all models show a change to Atlantic based weather with a band of rain and hill snow move East across the UK in association with a set of fronts moving in from the West. So after a rather cold and frosty few days with freezing fog developing and some light rain or sleet in the far west for a time the weather changes in time for the new week.

GFS then shows that in the reliable time frame the pattern of Low pressure to the North with its associated rather chilly West or NW flow is maintained through the week with showers or rain at times wintry on the hills. By next weekend High pressure replaces a brief Northerly flow with fine and frosty weather for a day or two before the High slips South into France opening the door to milder Westerly winds with rain at times, most likely towards the North with dry conditions in the South for longer periods. Then towards the end of FI the pattern resets following the passage of a cold front SE over the UK.

The GFS Ensembles show a rather cold spell of weather still dominant through the pack. With rainfall shown through next week and beyond the rather coldness look likely to be due to a cold zonality pattern with rain or wintry showers the most likely weather pattern. the operational was a marked warm outlier through the milder phase.

The Jet Stream shows the light Northerly flow over the UK in association with the trough in the Jet over Europe lasting a few more days before a resurgence of the flow ESE from the States makes landfall near Southern Britain and France in a week or so time.

UKMO for midnight on Wednesday shows a low pressure close to the Southern North Sea with a trough NW to Iceland and SE to Italy leaving the UK in a rather cold and unsettled NW flow with rain or sleet at times.

GEM shows a complex Low pressure area over Europe at 144hrs and a cold North flow over the UK with a ridge out to the West which moves across later to be followed in turn by a new Low pressure area bringing rain and a return to rather cold NW winds and showers at the term of the run.

ECM shows a complex series of charts towards the end of its run with unsettled and rather chilly conditions clinging on especially in the North and East though with milder conditions out to the SW which are set to make inroads across the British Isles on day 10 of the run.

In Summary today the weather looks fairly benign over the coming two weeks. With no one weather type taking total domination the most likely outcome still looks like a rather cold zonal period of weather with rain or showers, and some snow on hills at times over the next few weeks. There are some slightly milder evolutions being shown across the output though and if they verify it could be some time before we can tap into any major cold outbreak given the synoptics shown in 10 days or so.

[swfc]

Morning All-

Encouraging times this morning, especially again from the UKMO, which has generally been performing well.- everything edging west with the milder 0c incursion being shortened at both ends-

The UKMO dives that low well however holds the system stationary over southern greenland allowing the ridge to build ahead of it..

A lot of people reporting that the atlantic would come screaming back in & flatten off, however im still convinced the slider pattern is a sign of things to come.

S

Morning Steve.Re the slider.Do you think pressure to the north and east is high enough or looks like being high enough to hold or push things further west?Is it a case of things changing at short notice.thanks in advance

[andymusic]

Latest snippet from MR desk at Ops Centre re developments Sunday. Stress considerable uncertainty but MOGREPS paints consistent story at least re snow potential: " There has been a trend towards less of a risk of sig snow in the forward portion of the frontal bands advecting from the west Through Sunday. This hinges on where the first occlusion slows/stalls/weakens as upstream wave development evolves. Snow probs from MOGREPS quite muted for England and Wales, but more substantial in Scotland".

Rather cold cyclonic signal with temporary milder interludes W/SW is a brief summary of their more detailed 6-15d analysis.

still think it might come down to the wire sunday night Ian - we shall have to see - but you obviously have more info than we do and experience to work with!

[SMU]

Hi SWFC

As it stands there isnt a strong enough signal to the NE for stationary blocking- it appears we will need a pressure build in the atlantic which eventually shears to the east & allows undercutting.

There is still a chance at day 4+5 for the snow line to be further west- however its still low-

-

More Possibilities within the atlantic at day 8+9

S

Edited November 29, 2012 by Steve Murr

[Methuselah]

So, with the 06Z oozing-out as we speak, the question is, I guess: will the model consensus (if such a thing even exists) continue to slowly edge away from anything severely cold, or will things miraculously turn around? We will see...

[SMU]

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

ECM unsure- very mixed signal.- very unclear around the atlantic movements..

S

[MKN]

Ian does mogreps suggest much between midday tomorrow into Saturday morning in terms of snow potential for the northeast and Scotland?

[Frosty.]

I was being dramatic!

Yep

The ukmo has been praised to the sky recently but it was plainly wrong with the persistent easterly and it was therefore forced to drop it and fall in line with gfs and ecm, so I don't trust anything the ukmo shows at T+144 after that fiasco. We are still in good shape for another cold snap later next week as we get a brief arctic blast and there is still plenty of time for the pattern to upgrade from a toppler to something more prolonged.

[Catacol]

I think the slider low is now likely to turn into a damp squib for most with the ridge to the ne giving in very quickly, after 144hrs i'd bin all the operational output because we now have these sub-tropical lows on the scene which are likely to throw a curveball into proceedings.

Its very difficult to say where these will track and where they will phase with northern stream energy coming out of the USA. The ECM reverts from its winter wonderland of yesterdays FI to show potential again but really we're going to have to wait and see.

I'd expect even more model volatility now, the NH pattern does have potential but I think most people would now like to see this translated into tangible effects on the ground.

Agreed - whether it slides or not there is not enough embedded cold for this first low to produce much but sleety rain or rain for the majority.

What I find fascinating at the moment is the constant attempt by all the models to try to reform the vortex, and as a result bring back atlantic influence in our sector. This runs totally at odds with the ongoing assault on the strat, forecast temp rises at 30hpa and the analogs posted by GP. It also runs counter to the pressure anomaly pattern posted yet again yesterday over at cpc for the 8 - 14 day period.

Something has to give. Either we are going to find that the models simply cannot cope with the state of the vortex at present (take any model you like on meteociel: run it past the high res 72 hour mark and all seem to me to jump from the current messy pressure pattern to a much more zonal appearance very quickly) and have it wrong, or a good number of analogs,teleconnections and heavy weight forecasters are going to have egg on their faces. Add the EC32 to that list, and also the updates of the MetO which, while accepting considerable variation in output, have leaned towards cold.

I am still confident that the models are struggling, certainly beyond 120h. The pattern is forecast to be fairly flat over the US, but there is still the strong suggestion of mid atlantic height rises and pressure over greenland hand in hand with an indication of the ridge over california backnig west (cpc prognosis yesterday)... and with that announcement I will stick with the feeling that we might get height rises to the east of Iceland. Timeframe? Good question... certainly 144h plus.

[chionomaniac]

Whats this slipping in the heart of the England at T+51

Edited November 29, 2012 by chionomaniac

[MKN]

The whole pattern is slightly further southwest quite early on in this run, what knock on effects that will have though is up in the air

[snow drift]

Whats this slipping in the heart of the England at T+51

Snow!! Lots of great tech posts but you are not sure what the pink blob is?!!!!

Edited November 29, 2012 by snow drift

[SMU]

looks like a snow flurry chiono ! lol-

http://modeles.meteo...fsnh-1-72.png?6

T72- a line of -6s now across the spine & the front further west-

higher risk of initial snow now shown... things turning in our favour again over the last 24 hours- all because the low is modelling back west up to greenland.

Steve

Edited November 29, 2012 by Steve Murr

[nick sussex]

Agreed - whether it slides or not there is not enough embedded cold for this first low to produce much but sleety rain or rain for the majority.

What I find fascinating at the moment is the constant attempt by all the models to try to reform the vortex, and as a result bring back atlantic influence in our sector. This runs totally at odds with the ongoing assault on the strat, forecast temp rises at 30hpa and the analogs posted by GP. It also runs counter to the pressure anomaly pattern posted yet again yesterday over at cpc for the 8 - 14 day period.

Something has to give. Either we are going to find that the models simply cannot cope with the state of the vortex at present (take any model you like on meteociel: run it past the high res 72 hour mark and all seem to me to jump from the current messy pressure pattern to a much more zonal appearance very quickly) and have it wrong, or a good number of analogs,teleconnections and heavy weight forecasters are going to have egg on their faces. Add the EC32 to that list, and also the updates of the MetO which, while accepting considerable variation in output, have leaned towards cold.

I am still confident that the models are struggling, certainly beyond 120h. The pattern is forecast to be fairly flat over the US, but there is still the strong suggestion of mid atlantic height rises and pressure over greenland hand in hand with an indication of the ridge over california backnig west (cpc prognosis yesterday)... and with that announcement I will stick with the feeling that we might get height rises to the east of Iceland. Timeframe? Good question... certainly 144h plus.

Good post and I think the GFS is being too progressive, indeed on this run theres already some adjustment westwards especially in the USA .

In terms of the slider low, this run looks a little better, this may well trend towards the UKMO.

Scratch that! this is going somewhere else, a big change, surely not!

Edited November 29, 2012 by nick sussex