Winter Model Discussion - Cold Hunting -12Z 30/12/12

[UV-RAY]

Lots of fascinating weather to get through in the next few weeks, first off some exceptionally high temps for the time of the year starting this weekend and at long last a drying out period for those flooded areas, then further out the prospects of the the PV being displaced but where this puts up shop is unclear at this moment in time. I still feel we will be on the wrong side of cold at first and will have to wait for the projected SSW later, for us to finally hit the bullseye. All in all lots to get through before then, so lets make the most of the drier spell of weather before any cold nirvana later on.

[ITSY]

Hi Itsy,

You sound like you should be a moderator. You have made a valid comment on how this thread should be, i.e: very informative, detailed posts, so people like myself and others willing to learn can interact with others points, not the one liner, back biting, down right nit picking posts.

keep up the good work we need people like you. Happy New Year

Here here

100% agree with you

Thanks you all, very flattering. Maybe at next selection!

Anyway, not long now till our next installment!

[Zenarcher]

Happy new year everyone

Model comparison using the GFS, ECM, UKMO, GEM, JMA and NOGAPS,

Next 72 hours to Friday - All the models show high pressure over the UK we can expect this to give us cloudy conditions with plenty of mist and fog around, winds will be generally light overall although Northern parts will see gales at times.

96 hours Saturday - All models show high pressure sticking over the UK at this time and out in the Atlantic we still have disagreement on the low entering the Atlantic, all models apart from JMA and UKMO form a low, I've marked out on the image where the center of the low is,

They all are close to each other although the depth of it ranges from 980mb to 995mb so still uncertain about it and we even have two models not showing it.

120 hours Sunday - Looks like it's 3 models against another 3, the GFS, ECM and NOGAPS show a very deep low to the South of Greenland, GEM has two lows in the Atlantic although none of them are too deep and the JMA and UKMO have a low sitting out in the Atlantic. Over at the UK the models still show high pressure in control.

144 hours Monday - Most of the models end up showing Atlantic depressions moving over our North giving unsettled weather for most of the UK although the far South of England hangs onto high pressure.

168 hours and ahead - General picture from them is the Atlantic staying in charge but the ECM builds up high pressure over the UK again and the end of the GFS run shows some wintry weather arriving.

Overall - The models are still in disagreement but do show high pressure staying with us for at least a week. Western and Northern parts will be unsettled at times as well. For those new to model watching or a reminder to everyone about why the models struggle in the long range take the GFS for example even in the high res part of the run it can get things wrong that happens all the time once we get to the low res part of the run 192 hours onwards that's where little faith is. Something like a SSW will take a bit of time for the models to catch onto but once we get closer to the time the models will become capable of picking it up. That being said the GFS for a while now has shown constantly a warm up in the Northern Hemisphere even in the low res.

[Iceaxecrampon]

Mean heading in the right direction (down) - that's all I can see for the next 2 weeks.

Fifteen days time.......

Any 1000ft asl Gully snow condition charts available tonight?

All pointless TBH

Ian

Edited January 1, 2013 by Iceaxecrampon

[Ali1977]

Higher pressure over Greenland on 18z

[TEITS]

Have to be honest im not convinced of the model output at +168 let alone beyond this.

http://www.wetterzentrale.de/pics/Recm1681.gif

http://www.wetterzentrale.de/pics/Rtavn1561.png

Looking at the ECM/GFS and the reason why the ECM has been so inconsistent is the models are struggling to resolve the Atlantic LPs and their eastward progression against the blocking to the NE (usual saga!). This is why I still wouldn't rule out an E,ly developing around the +240 timeframe.

[ITSY]

If you're following the SSW and its affects on the output, then this is interesting

upper level winds reversed to a prevailing Easterly with warming heading into Greenland and Scandinavia. There is nothing certain about what this means synoptically, but it should help feed a blocking pattern, so don't be surprised to see it

If you flick between frame 1 and frame 186 you will see the reversal - one of epic proportions as well, I should add. Truly amazing shift, even if it doesn't affect our weather!

Edited January 1, 2013 by ITSY

[Rocheydub]

@Ali1977 No there is not. Please stop trying to raise hope.

[johnholmes]

Happy New Year everyone

for what it's worth these are the rough notes I have made today after a close look over the past 48 hours of the 500mb anomaly charts.

General notes re past 48 hours or so

Both have moved things east, ridge from <20E to nearly 30e and trough from 30-40 west to 20-30 west; movement of 5+ deg per 24 hours maybe touch more, flow over states kept wly no sign of any ridge/trough. There MAY be a touch more ridging south into Greenland on both

Pv bit different between thm, ec has deeper over n-nw Canada gfs not there

Both showing some sign of deeper vortex s of Greenland especially gfs

There are changes but not clear just what they are trying to suggest if they are hinting at a pattern change.

2-3 days more and noaa to show similar before any real idea of pattern by say 17 jan??

Noaa

The ridge n of uk towards nne of Greenland is kept, +ve value a bit below last issue; flow into uk is just s of west

As noted this morning its early days but possible some kind of block is being set up-would suggest a link from nne of Greenland into area that over Europe-say 2-3 days to confirm or otherwise?

Naefs less keen on this at 240h but slight signs but then overtaken beyond this with largish –ve w-e with uk at centre?

so possibly the first tentative signs of the upper air charts showing a change in pattern?

The answer should be known within 2-3 days one way or the other.

[Ali1977]

10mb @ T160

[Rocheydub]

Surface pressure and absolutely no use whatsoever.

[Grimsby Snow Lover]

10mb @ T160

Look for greens/yellows over Greenland mate. This indicated better heights for blocking to develop there. Blues/purples have cold uppers, no good to support blocking.

[Tim Bland]

This run looks more like the ECM with pressure rising over Scandinavia draging colder air east from central Europe http://www.meteociel.fr/modeles/gfse_cartes.php?ech=276&code=0&mode=0

Scrap that..goes the sme route as last few runs with PV slipping se over us. Would be nice if some colder air from the east came in first. Could be copious amounts of snow for the north and high ground if this happened and it's becoming a consistent signal from GFS now.

Edited January 1, 2013 by Tim Bland

[LomondSnowstorm]

Everything a bit more amplified and further west on this run, more similar to the ECM than the 12Z GFS was. Keeping the Atlantic energy from moving east and ensuring the pattern is amplified, preferably with neutral or negatively oriented troughing is what we really want to see in the 5-10 day range.

[Weathizard]

Not a moan but I'm getting slightly annoyed of seeing that PV power up after 240 now, very irritating, like watching one of them annoying showboaters prance around the boxing ring. Move over and allow the massive high in the Atlantic to move in. Massive storm at the end of this run, but about as likely to come off as Folkestone town winning the FA cup.

[I remember Atlantic 252]

Deepest FI has PV chunk over us again, shouldnt need very low uppers for snow off that, -4 to -5 surely okay

[ITSY]

If you're following the SSW and its affects on the output, then this is interesting

upper level winds reversed to a prevailing Easterly with warming heading into Greenland and Scandinavia. There is nothing certain about what this means synoptically, but it should help feed a blocking pattern, so don't be surprised to see it

If you flick between frame 1 and frame 186 you will see the reversal - one of epic proportions as well, I should add. Truly amazing shift, even if it doesn't affect our weather!

Following on from this, by the end of the run the vortex is completely displaced:

Large and steady HP building into West Greenland after about a week lag from a strong SSW. On the basis of the SSW, it looks plausible, and indeed positive. Expect several bites at the cherry and several potential failures before anything POSSIBLY occurs. (hopefully the ifs, buts and maybes will slowly fade as we sure up on the SSW and the resulting shift to blocking somewhere in the Northern Hemisphere).

People need to calm down about seeing a large vortex. Patience and detail is the key to understanding the nature of major upcoming atmospheric shifts.

Edited January 1, 2013 by ITSY

[nick sussex]

If patience was correlated with reward this thread should be enjoying loads of snow fun and sledging because having to endure the almost endless dross dished out by the models over the last few weeks certainly is deserving of that.

As it is we have two strat warmings one SSW and another smaller warming over Greenland, if this can't remove the limpet PV from Greenland then nothing will.

So it looks like we'll have to put up with the underwhelming output for a while yet, lets hope that we can get a quicker initial response to the SSW and more amplification upstream.

[damianslaw]

Realiable timeframe-i.e. out to the 7th Jan, all models show high pressure from the south dominating once we clear the front crossing the country tomorrow, however, far NW parts will see a moist flow from the SW so less settled here. As we move further into next week, divergences between GFS and ECM, the former wants to bring the atlantic in sending the azores high back south, whereas ECM holds the ridge and pushes it north as the atlantic trough elongates in the mid atlantic thanks to a weak PV, the end result an increasingly colder more seasonal outlook. However, we need to see future ECM runs maintain this evolution before we can give it any credence.

All eyes then on how the building pressure from the south behaves which will be dictated by events over the mid atlantic and the strength and position of the PV which looks to be weakening by the day.

If the ECM scenario verifies, I would expect the high to very quickly build northwards over scandi and with a weak PV it opens all sorts of possibilities from the north and east. I do think the route to cold as we move into the middle of Jan is more likely to come courtesy of heights building from the south into scandi rather than relying on trough displacement/fragmentation which is most likely to occur with the GFS output this evening - a much more difficult route to cold. Indeed looking at the ECM output this evening reminds me alot of early Dec 2009...

[ITSY]

If patience was correlated with reward this thread should be enjoying loads of snow fun and sledging because having to endure the almost endless dross dished out by the models over the last few weeks certainly is deserving of that.

As it is we have two strat warmings one SSW and another smaller warming over Greenland, if this can't remove the limpet PV from Greenland then nothing will.

So it looks like we'll have to put up with the underwhelming output for a while yet, lets hope that we can get a quicker initial response to the SSW and more amplification upstream.

Absolutely. The fact that we have so much upper level warming is, as far as I am aware, relatively unusual (though be no means unheard of), so the likelihood of cold as a consequence is far greater than 'normal' possibilities (like last December for example). Ian's earlier posts that the metoffice guys and girls are excited by upcoming prospects illustrates the unusual circumstances

[Timmytour]

FI sees a cold pool to the East make some progress towards the UK. Doesn't reach us as the Atlantic pushes it back. But i think that will turn out to be a reverse of what we had in December. This time I think the models are overplaying the Atlantic and come around the T200 mark they will start to show that cold pool to the East reaching and progressing across the UK while the Atlantic fails to make the progress shown at present.....maybe we'll also get the help of an undercutter as well show up in a couple of days time

[pyrotech]

Happy New year everyone.

Just a precaution on the SSW and to ensure that less experienced users do not get to think cold and snow is guaranteed.

The Met Office are discussing this, and they think it is feasable that we will see a cold spell like 2010.

However like many seasoned members here are aware it all depends on where the high pressure sets up its stall.

one such quote is "to whet the appetite the 2009 sudden stratospheric warming split the polar vortex (rather than displacing) and so does this one! "

So yes we have an opportunity for something rather special. But the cold could stay in Europe if other factors do not come in to play that makes it right for our little Island.

The models are showing the SSW propogate, but the effects nearer the surface are totally not represented IMHO on the models and will not for a little while, i expect the models to fish tail a little and then when everything starts to happen it will then get interesting.

Its a very exciting time for cold lovers, but a time to be causious in case, as the fall can really hurt as we found out with the beast from the east.

I would say that once the models do pick it up in both cross model and consistancy ( if we are to get the cold air) that its more likely to happen than what happened a few weeks ago. But until we get that then its a case of one step at a time.

We do look like heading in right direction with heights trying to ridge north of us as shown in the models, but they really do not know where to exactly place it, the trend right now is that blocking will be over Russia / Siberia, I still have a horrible feeling if that happens it could be a repeat of what happened with our neighbours getting an awesome winter.

with the effects moving from stratosphere to troposphere occuring during next fortnight i think we will see alot of changes on the models.

I would suspect what Ian is talking about with discussions at Meto, is the possabilities of this cold, that somewhere in Northern hemisphere will get something very special, but for us its a possability, Europe probably almost a certainty. ( Ian please correct me if im wrong) What ever happens it will certainly make model watching very interesting, but its not guaranteed cold and snow for us - at the moment.

[TEITS]

Just looked at all the ensembles upto +300 and to be honest they are clueless which isn't surprising considering the varied operational runs we have seen. Having said this the 14th Jan continues to be the day when some of those ensembles show it turning colder.

Must admit though ideally I would like to see a cold spell develop earlier i.e 11th-12th Jan but currently it looks around the 14th Jan. This is why I said a few days ago that im eagerly anticipating the ECM output later this week.

[Weathizard]

Interesting ENS, as said above they don't really have a clue, its hard to take any clues because their isn't a real clear scenario that is being repeated(to a certain extent) being shown on the models, quite a few cold members with brief topplers but there is a few that have some nice Greenie/Atlantic ridges being built!

On to tomorrow for more clues, evening guys and happy new year.

Edited January 1, 2013 by Weathizard

[Slowpoke]

I'm sick to the back teeth of Atlantic driven weather....