Model Output Discussion - 8th December Onwards

[Gibby]

Good morning. Here is the morning review of the 00zs as seen through my eyes on the output from GFS, UKMO, GEM and ECM for today Sunday December 9th 2012.

All models show a NW flow over the UK turning Northerly late today as a Low slips SE down the Eastern North Sea towards Europe. Pressure builds strongly over the UK from the NW behind with High pressure encompassing the UK out until midweek. After some cloud and patchy light rain clears Southern Britain later today all areas will settle into a cold and settled spell with some wintry showers in Eastern areas tomorrow and Tuesday. With sunny spells elsewhere by day and clear skies at night frosts will me a marked feature overnight with some freezing fog patches too.

GFS then shows a SE flow deveeloping on Thursday and continuing through Friday as pressure falls from the West. The weather would stay cold with wintry showers in the NE and a band of rain preceded by snow moving slowly NE into the SW later Thursday and into Cental areas by the weekend with an appreciable snowfall possible for a time. Over the weekend the snow moves on towards Scotland where it would likely stay with some disruption possible while the South sees less cold but very unsettled conditions with rain and showers over the weekend. In FI this morning the operational shows the milder air winning out for all for a time before the block to the NE forces Low pressures to move SE into Europe with a tendency towards further rather cold and unsettled conditions with rain, sleet or snow at times to return by the end of the run. CHRISTMAS DAY on this run would show a rather cold day with rain and sleet about and a chance for some snow on the hills meaning some areas would see a white Christmas.

The GFS Ensembles show a less supportive chance of cold for Christmas with a trend to normal 850's quite early in the run in a cyclonic flow over the forecast period with rain or showers at times.

The Jet Stream forecast shows the flow tumbling SE over the UK at the moment into Europe. This part of the Jet weakens in a few days time as a strong arm pushes East out of the States across the Atlantic making landfall over France and Southern England late in the week and over next weekend.

UKMO for midnight on Saturday shows a strong High pressure over Russia with a weak link to Greenland. Low pressure from the Atlantic is disrupting as it approaches UK airspace with troughs ganging up down to the SW carrying bands of rain with some snow on the forward edge in the SW and more widely for Northern and Eastern areas through Saturday. On this run it looks like changes to milder air will be slower than recent runs especially for the North.

GEM shows a much more progressive pattern with the cold air pushed away more quickly NE out of the UK. In its plalce Low pressure to the NW brings spells of rain and showers to all before the Low weakens by day 10 as the embryonic signs of a block to the North and East sends Low pressure down into Europe later introducing colder conditions again.

ECM shows a spell of rain with snow preceding it moving staeadily NE over Friday and Saturday in a strong SE wind. By the weekend all but Scotland see less cold and rainy conditions as winds turn cyclonic South-westerly. Scotland maintains the cold and wintry theme longest before it too joins the rest of the UK in an unsettled and windy, milder spell with rain at times to end the run.

In Summary there is a little more resistance shown to the models this morning in holding the cold a while longer and permitting the chance of a wintry breakdown to affect more locations as we reach the end of the week. For areas in the South and West this period is shown as relatively shortlived while the North could see quite a bit of snow before the thaw sets in for all with rain and milder weather taking over all areas beyond next weekend. There is a tentative sign from some of the models namely GFS and GEM where the block tries to reassert authority late in there runs pulling Low pressure down into Europe and reintroducing a cold continental feed. Things remain very volatile on the model runs at the moment and I still expect to see quite a few changes run to run from model to model over the coming days until this breakdown zone has passed

[SLEETY]

I said yesterday I was surprised the met office in their 6-10 updated forecasts were so confident that the fronts would push through so quick as they thought, and I was confident the models had underestimated the strength of the blocking high and we could see more prolonged snow as the front stalls.

Well we are certainly heading in the right direction.

I hear fergieweather wont be posting anymore .what a shame,what happened?

Edited December 9, 2012 by SLEETY

[TEITS]

As members have commented so perfectly on the changes this morning I thought I would look at the later period although obviously the changes we are seeing earlier on could impact this.

I said yesterday that despite the disappointments the models continue to suggest relatively high pressure across much of Greenland/Svalbard/Scandi/Siberia. If you look at todays +240 GEM you will see this is certainly the case.

http://www.wetterzentrale.de/pics/Rgem2401.gif

Same with the ECM although the earlier timeframes aren't as good as the GFS/UKMO.

http://www.wetterzentrale.de/pics/Recm2401.gif

Taking on board all of the output and making a forecast is a nightmare. I was convinced yesterday morning that all of the UK would be milder by Thurs but now this could be delayed or not even reach some parts of the UK. In these situations that the GFS/UKMO are suggesting the highest risk of turning milder is the SW and those in the N have a greater chance of remaining cold. The UKMO is a peach of a chart because most would remain cold with snowfall.

[snowblues]

Well what a nice surprise this morning,there was a fair few of us in the last 48 hrs thinking that atlantic charging in does not look right, with the russian high standing its ground.Maybe short term upgrades for tues/wed,depending how the brakes are put on theatlantic.

Edited December 9, 2012 by snowblues

[TEITS]

A feature worth keeping an eye on is this running down the N Sea.

Still a chance that this could be further W.

[bluearmy]

can someone work out what is happening with GEM. the wz data seems to be continually at odds with meteociel. it was pointed out that meteociel was the correct feed the other day. what is wz showing? is there a parallel op being run ?

[Paul]

I've not looked on WZ or Meteo, but there is a hi-res and a low-res version of the GEM (we're about to start showing the hi-res one on netweather), so it's possible that they're using different versions.

[beng]

I think part of the reason for the model shift maybe this:

http://www.wetterzentrale.de/topkarten/fsdivka.html

Much of Europe has become snow covered in the last day or so, which will lead to a more intense level of embedded cold. On top of that the models were always wrong in how they originally brought southerlies into Scandinavia in such easy fashion - part of the changes are just reflecting the model adjustments back to something more reasonable.

[bluearmy]

paul - do you have the data yet? if so, can you advise if it has an azores ridge or cut off low over the s uk. maybe that question is an illustration of where we are !!

[Paul]

I don't have live data for it currently I'm afraid as it's built but not running.

[bluearmy]

I don't have live data for it currently I'm afraid as it's built but not running.

just accessed meteocentre and meteociel is right. no idea what wz is running off. shame as that rather takes the edge of TEITS earlier post as the GEM chart was indeed a gem!

[Methuselah]

Well peeps, the 06Z'll be oozing out very shortly...Toys at the ready!

[Severe Siberian icy blast]

Imagine this. . . . Suddenly the models get to grips with the real issue, the continent is in the freezer, entrenched cold coming over the uk, the models completely over reacted to a signal from the Atlantic AKA false dawn ( Gp ) and now the go back to showing "right" scenario and show -10 upper air flooding the country with any attacks from the Atlantic sliding down the country reinforcing the block and keeping us cold and snowy.

Now the models are finally getting to grips with movement of the vortex to Siberia they can finally settle down and begin the retrogression from scandi to greenlands.

Déjà vu

[bluearmy]

Imagine this. . . . Suddenly the models get to grips with the real issue, the continent is in the freezer, entrenched cold coming over the uk, the models completely over reacted to a signal from the Atlantic AKA false dawn ( Gp ) and now the go back to showing "right" scenario and show -10 upper air flooding the country with any attacks from the Atlantic sliding down the country reinforcing the block and keeping us cold and snowy.

Now the models are finally getting to grips with movement of the vortex to Siberia they can finally settle down and begin the retrogression from scandi to greenlands.

Déjà vu

wake up shaun !! it can't happen till you change your username back !

[ribster]

As members have commented so perfectly on the changes this morning I thought I would look at the later period although obviously the changes we are seeing earlier on could impact this.

I said yesterday that despite the disappointments the models continue to suggest relatively high pressure across much of Greenland/Svalbard/Scandi/Siberia. If you look at todays +240 GEM you will see this is certainly the case.

http://www.wetterzen...cs/Rgem2401.gif

Same with the ECM although the earlier timeframes aren't as good as the GFS/UKMO.

http://www.wetterzen...cs/Recm2401.gif

Taking on board all of the output and making a forecast is a nightmare. I was convinced yesterday morning that all of the UK would be milder by Thurs but now this could be delayed or not even reach some parts of the UK. In these situations that the GFS/UKMO are suggesting the highest risk of turning milder is the SW and those in the N have a greater chance of remaining cold. The UKMO is a peach of a chart because most would remain cold with snowfall.

Indeed, I'm not convinced that we will see a full breakdown, at least not yet anyway (as you illustrate above). If the models can flip one way, they can flip back the other, which they seem to be slowly, but surely doing.

[Rollo]

Imagine this. . . . Suddenly the models get to grips with the real issue, the continent is in the freezer, entrenched cold coming over the uk, the models completely over reacted to a signal from the Atlantic AKA false dawn ( Gp ) and now the go back to showing "right" scenario and show -10 upper air flooding the country with any attacks from the Atlantic sliding down the country reinforcing the block and keeping us cold and snowy.

Now the models are finally getting to grips with movement of the vortex to Siberia they can finally settle down and begin the retrogression from scandi to greenlands.

Déjà vu

Whoa there and hold your horses, I would wait awhile otherwise it could be another huge anticlimax yet again, the 12z will be of interset but this saga has some way to run. We have been given hope but thats about all.

[chris55]

We have had a significicant change in the GFS & UKMo overnight to a slower system and a stronger signal for trough disruption at a better angle for the UK-

Instead of the South westerly onshore flow we now see a South easterly on SOME runs & the 0c isotherm straddling the SW not making in any inroads-

The overnight turnaround is pretty spectacular & nothing short of the turnaround from the other day when we lost the initial easterly- its almost a double barrelled laugh at us, because not only did things collapse at short notice for the easterly, but now could the thing that was partially driving the collapse of the easterly collapse itself into something more snowy!

If the ECM goes this way then a more positive upbeat mood should ensue today, also the UKMo at 144 sees the shortwave over SE Scandi beginning to turnover allowing high pressure to filter back over the top rather than stay at an angle whereby retrogression can develop-

We are not there yes, however thats a BIG step- we dont need any more big steps on the UKMO- just fine tweaks will do-

SNOW for many...........

Whilst we emphasise the usual disclaimers here are the 18z ensembles for london for reference-

Note the 2 peaks in succession- one for the first wave to move to 0c - then the continued drive east from the atlantic to reach 5c-

Watch for these 2 peaks to be smoothed & taken down sub zero- hopefully could happen over a few runs-

S

Excellent summary Steve, I couldn't really believe my eyes when I flicked through the charts this morning. Huge changes in favour of a colder more snowy attempted breakdown. Exciting stuff.

Edited December 9, 2012 by chris55

[Habsish]

Working on the chaos theory does any one think that a crowd of butterflies in the Amazon jungle are flapping their wing hard to queer up the models?

[Severe Siberian icy blast]

Whoa there and hold your horses, I would wait awhile otherwise it could be another huge anticlimax yet again, the 12z will be of interset but this saga has some way to run. We have been given hope but thats about all.

Lol I thought that would raise a fe eyebrows , I do however feel we will now begin to see a complete turn around, I genuinely feel them fronts will not make it up the uk , I can't see this cold spell ending next wkend.

[nick sussex]

I don't think we've managed the Great Escape yet!

But we've started digging! With the PV moving to Siberia we might see more changes, this mornings output is a start.

Looking at the ECM ensembles they still bring in some milder conditions to De Bilt but this is delayed and theres another cluster of colder solutions developing from Friday into Sunday, in these set ups with energy going se you can see some wild flips in the ensembles.

As a comparison heres this mornings extended ECM ensembles:

Compare that with last nights shorter ensembles:

You're getting a more distinct separation of clusters around Friday..

I'd disregard the ones past 10 days too far out given the change in the NH pattern. And much depends whether the models continue to retrogress the pattern.

Edited December 9, 2012 by nick sussex

[chris55]

The biggest change this morning and it is supported by the big three is the slider shortwave digging south east at T96, this begins to under cut the block and it's this change overnight that's key.

[Severe Siberian icy blast]

I don't think we've managed the Great Escape yet!

But we've started digging! With the PV moving to Siberia we might see more changes, this mornings output is a start.

Looking at the ECM ensembles they still bring in some milder conditions to De Bilt but this is delayed and theres another cluster of colder solutions developing from Friday into Sunday, in these set ups with energy going se you can see some wild flips in the ensembles.

Well the baggies managed the great escape several years ago in the prem, why can't we see it in the models??! After all they decided to snatch this away from right under our noses without warning. Why can't it do it again? After all , what the models are hinting at this morning is more in line with the teleconnections and strat conditions, along with fitting the bill within gp's forecast.

[Methuselah]

I still remain unconvinced - of anything - right now; whatever any individual model run might suggest...

[Cloud 10]

Comparing the gfs 00z jet stream charts from yesterday and today for wednesday

clearly show the jet being diverted south as it approaches the UK.

In other words,SLIDER ALERT!

yesterday.. today..

[Jason H]

The cold has been delayed yes, but the outcome by the weekend will still be milder in my opinion. The block is stubborn, but we're really right on the edge of it. I would imagine Holland might hang onto the cold but milder for us. The chances of a snowier breakdown has increased this morning according to the models and if I was in Northern England and Scotland things could get quite interesting later this week.