Model Output Discussion - 19th - 25th December

[Frosty.]

I note GP'S cautious post regarding the polar westerlies gradually running out of juice so to speak with interest. The CFS extreme range model that starts at 364 and heads on out to 1092 hours which has been showing endless westerlies and very much a mild rinse and repeat scenario for ages now has suddenly switched to repeated northerly and easterly outbreaks from about mid Jan onwards ( worth a peak if only from a chart porn point of view) which fits in very nicely with GPS's own winter forecast and that of RJS as well Possibly the first stirings of a change down the line perhaps

The Gfs 12z operational run shows that beginning to happen at T+384 hours with a chance of a NEly blast brewing.

[BARRY]

I have been looking at the models for week's, and a new year shift is definitly on the cards, Mrs B's hands and feet are getting sore and cracked which happens about 2 week's before a pattern change to cooler weather, happens all the time and it is always right,don't mean it will be really cold but it will be chilly

Edited December 21, 2011 by BARRY

[Frosty.]

This sparked my interest, hows that for a pattern change in the new year..this should be along the lines of what would happen as the warming strat impacts on the uk weather.

We just need that continental high to sod off and allow the floodgates to open wide.

Edited December 21, 2011 by Polar_ Low

[shotski]

This sparked my interest, hows that for a pattern change in the new year..this should be along the lines of what would happen as the warming strat impacts on the uk weather.

We just need that continental high to sod off and allow the floodgates to open wide.

Hi PL could you please go into a bit more depth about what you see for us in here still learning, all I can see on that chart are mild

S'westly winds ?

[weatherguy]

Hi PL could you please go into a bit more depth about what you see for us in here still learning, all I can see on that chart are mild

S'westly winds ?

He's referring to the atlantic essentially being blocked there, and the PV is no longer as strong as it has been over Greenland. Ie. The chart is not showing cold, but the potential for cold looks much better for us (because there isn't a stream of low pressure systems moving in from the west); as PL says, the continental high is preventing the cold from moving south into the UK in that chart however.

Edited December 21, 2011 by weatherguy

[nick sussex]

Regarding that low centred near the UK at 168 hrs, some support in the ECM ensemble maps for a more favourable ridge to the west:

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2009112700!!/

Quite a few have the -6 isoline further south.

The short ECM ensembles for De Bilt show some colder solutions over there, these are likely to be in relation to a more favourable toppling ridge bringing an easterly flow before the jet finally flattens the ridge.

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

[Frosty.]

Hi PL could you please go into a bit more depth about what you see for us in here still learning, all I can see on that chart are mild S'westly winds ?

Yes it would still be mild at that point but if the model run went a few days further it would hopefully show the european high pushing away southeast and with a decent greenland high building but mostly the deep trough over scandinavia waiting to unleash a NEly blast for the uk which is a possible outcome of SSW in the new year and something that BFTP and RJS are anticipating along with GP?..but definately not what Ian Brown is expectig.. bARTLETTS and more B********

Edited December 21, 2011 by Polar_ Low

[shotski]

Cheers polar, would it not also be possible for the euro high to migrate north over greenland or norway giving a similar outcome ?

Edit: wouldn't the trough over scandi produce a N'wstly ?

Edited December 21, 2011 by shotski

[phil nw.]

Regarding that low centred near the UK at 168 hrs, some support in the ECM ensemble maps for a more favourable ridge to the west:

http://www.ecmwf.int...t!2009112700!!/

Quite a few have the -6 isoline further south.

The short ECM ensembles for De Bilt show some colder solutions over there, these are likely to be in relation to a more favourable toppling ridge bringing an easterly flow before the jet finally flattens the ridge.

http://www.knmi.nl/e...M_06260_NWT.png

Yes i was about to search for those Nick and there are quite a lot of variations on how that High is modelled.

The GEFs thumbs also show some interesting solutions at T168 -ridging that High much further north.

http://www.wetterzentrale.de/pics/senspanel1681.gif

If that trough coming out of Canada could dig further south in furture runs it would blow up that ridge ahead of it further north.

Still too much energy to our north is being modelled at the moment.Signs of it weakening with these little developments but not enough to change the 500hPa wavelengths just yet it would seem.

[Frosty.]

Cheers polar, would it not also be possible for the euro high to migrate north over greenland or norway giving a similar outcome ?

No I think the high is too far south on that chart and I can't see a way for it to retrogress towards greenland, if the high was further north it could get sucked towards greenland but the best way forward on the chart I posted would be for the high to sink southeast and allow the trough over scandinavia to push south west towards the uk like it did last december when a part of the polar vortex swallowed the uk up on a few occasions a year ago.

Edited December 21, 2011 by Polar_ Low

[Grimsby Snow Lover]

Could anyone explain why weather online seem to have all the latest 18z charts already? I've checked the dates etc. Just wondering, thanks inadvance.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&CONT=euro&MODELL=gfs&MODELLTYP=1&VAR=prec&WMO=&ZOOM=0&PERIOD=&PANEL=0&ARCHIV=0&BASE=201112211800%26HH%3D378

Edited December 21, 2011 by Grimsby Snow Lover

[Richie V]

Could anyone explain why weather online seem to have all the latest 18z charts already? I've checked the dates etc. Just wondering, thanks inadvance.

http://www.weatheron...1800%26HH%3D378

Not that unusual really, Netweather seem to recieve the GFS later than most. Sometimes I'm all recieved by 20:50 on some days.

[Grimsby Snow Lover]

Not that unusual really, Netweather seem to recieve the GFS later than most. Sometimes I'm all recieved by 20:50 on some days.

Just worked it out following a similar question on TWO. Apparently the chart time is displayed in the bottom right corner, in which case the charts are not all up to date as first believed. I find the GFS on netweather comes out in pretty much the same time as Wetterzentrale.

[georgiedre]

ive just checked weather online and its on pink which means previous post! so it hasnt been updated yet! i think thats how this works!

[nick sussex]

If this shallow low verifies and runs in towards the UK it's likely to become a forecasting headache.

Will it engage some colder air heading se'wards?

Here we don't really get a strong enough undercut of cold air because the ridge doesn't build sufficiently north to the west but don't rule out some snow just yet for favoured locations.

It's unlikely to hang around for long as the ridge is likely to be flattened but I'm sure would still be welcome.

Edited December 21, 2011 by nick sussex

[mountain shadow]

Well the 18z finishes with a big fat purple PV over the pole. No sign of warming tonight.

[Robbie Garrett]

I know it's FI, but oh crap look at the Jetstream, where does it go???

Does it start heading south around the ridge near Newfoundland??

Edited December 21, 2011 by Robbie Garrett

[chionomaniac]

Well the 18z finishes with a big fat purple PV over the pole. No sign of warming tonight.

There is on this chart from the GFS 18Z at 1 hPa T+240

[Jason M]

Hi All

No respite on the pub run. Pressure stays high to the south all the way through.

This pattern looks a bit like what we had in Jan / Feb where high pressure over Spain / Biscay killed those months as far as any prospect of colder weather was concerned. Its interesting to run quickly through the charts on meteocel as it just shows the high pressure ebbing and flowing but never moving. Opinions differ on what constitutes a 'bartlett' but the 18Z in my opinion is a textbook example. Shades of the record winter of 88 IMHO (think that was the one:-) ).

Lots of time for things to change of course and the new year often brings a new pattern, but i've got a horrible feeling that were looking at many weeks of this to come.

In my years of following these threads i've never seen such a sustained period of time where the charts have shown nothing significantly cold (even at 300 plus hours out). I guess this just reflects the fact that the computer modelling is demonstrating the robustness of the pattern.

From memory, i think FI GFS runs at a lower resolution to its ensembles, hence it always just defaults straight to zonal and is often the mildest run in the suite. IMO any change will be flagged in the ensembles before the opp, so thats where i'll be looking over the coming weeks for any signs.

Jason

[nick sussex]

Before stress levels rise because of the underwhelming GFS lower resolution output we should bear in mind that just a few days ago there was zero sign of even a colder day let alone a chance of some snow, and as we've seen there is at least a small chance within 168hrs.

Whether this verifies only time will tell, in terms of the effects of any strat warming, if it does verify sometimes the output will suddenly switch, and sometimes it takes several weeks to show its hand.

But at least that is moving in the right direction, I know everyones in a hurry to see some good synoptics but we're just going to have to be patient to see how strong this warming will be and whether it ends with the PV finding a new home.

[Stratocumulus perlucidus]

I have been looking at the models for week's, and a new year shift is definitly on the cards, Mrs B's hands and feet are getting sore and cracked which happens about 2 week's before a pattern change to cooler weather, happens all the time and it is always right,don't mean it will be really cold but it will be chilly

I remember u said this a few weeks ago. And we have just had that cOld snap

[Liam J]

Well after this milder spell has given up the ghost (I can't wait) it looks like we will be back to a very disturbed and cool zonal pattern, certainly nothing on the horizon that would suggest looking east for any cold to materialise, not with the jet firing right across to Russia!

We need to be looking north or north west over the next few weeks for anything wintry, fantastic depth of cold building over Greenland... Any PM incursions would be quite potent.

Watch this space

Edited December 21, 2011 by Liam J

[Aaron]

Eek North West? After this recent period of cool weather they have proved only to be useless for me!

[Cheese Rice]

lol am I the only one who is happy with the output?

After what was looking like endless south westerlies under a cloudy high we now are looking at a possible snow event for Scotland with a low tracking north. Ofc I want it to hit here and have harped on in the past about how it has never happened but I'm glad to see temperatures will at the very least return to average. Perhaps further polar incursions to come.

[Robbie Garrett]

Before stress levels rise because of the underwhelming GFS lower resolution output we should bear in mind that just a few days ago there was zero sign of even a colder day let alone a chance of some snow, and as we've seen there is at least a small chance within 168hrs.

Whether this verifies only time will tell, in terms of the effects of any strat warming, if it does verify sometimes the output will suddenly switch, and sometimes it takes several weeks to show its hand.

But at least that is moving in the right direction, I know everyones in a hurry to see some good synoptics but we're just going to have to be patient to see how strong this warming will be and whether it ends with the PV finding a new home.

Is there any better charts out there, that show the jet movement as far as I am looking? as I am sure it's going south around the ridge at 384+