Model Output Discussion - 12th December Onward

[Thundery wintry showers]

From a personal forecast perspective, it means that, after having predicted a brief milder anticyclonic interlude followed by a return to colder stormy conditions around Christmas, then having backed down and considered various anticyclonic options, my original prediction is all of a sudden looking feasible again.

From a layman's perspective, it means that we will probably drift into a colder, windy westerly type around Christmas. It will probably be milder than what we've seen during the first half of December, at least to begin with, with some frontal systems bringing "warm sectors" and maxima near double figures in between the colder, showery polar maritime bursts, but for the longer term it could promote more "cold zonality" with chances of marginal snow events like the ones we're having now. Also, if pressure rises over Scandinavia, a NW-SE depression track will increase the chances of low pressure digging into Europe and rising pressure to the NE sending continental air our way from the east.

[Summer Sun]

Could christmas eve deliver snow for snow?

http://www.wetterzen...s/Rtavn2042.png

Christmas day also has good potential away from the south-west of england

http://www.wetterzen...s/Rtavn2282.png

Into the end of FI

http://www.wetterzen...s/Rtavn3241.png

http://www.wetterzen...s/Rtavn3841.png

[January Snowstorm]

Nice thoughts by GP above.

Of course if that trend does happen there's a small chance we could see some of the white stuff between Christmas and New year esp for the North and West.

By the way had snow in Cork this morning and roads were lethal from ice!

[UV-RAY]

It still appears the models are all over the place at this moment in time, is this because of some unknown factor not currently being picked up by any of the models? IMO I believe this is the problem, we have southerly tracking jet with a strong PV, normally these do't go hand in hand. The unknown factor is overriding all teleconnections it appears.

[phil nw.]

Recent medium range output was suggesting more of SW-NE tilt as we approached Xmas with a ridging Azores High.

Latest runs are suggesting a flatter flow-more E-W after initial approach of the High.

http://www.wetterzentrale.de/pics/Rtavn1441.png

http://www.wetterzentrale.de/pics/Rukm1441.gif

http://www.wetterzentrale.de/pics/Recm1441.gif

UKMO have dropped the idea of ridging those heights much further north-shown on their 12zrun yesterday.

The PFJ is shown straddling the UK much of the time from midweek with the boundary between cold and milder moving around as the front wavers.

This flatter flow would keep a long period of mild South Westerlys at bay with those heights suppressed by the jet.

Although some mild brief spells are modelled next week it could be quite cold and wintry in the far North as the colder air moves south at times.

The uncertainty lies in how strong the heights to our South will be as the balance could easily switch and we would see mild uppers moving right across the UK if those southern heights build further north than currently showing.

[Met4Cast]

I'll be surprised if the rain, sleet and snow moving into parts of the NW will reach our region, no models that I've seen are predicting it to make it further than the Midlands

[nick sussex]

It still appears the models are all over the place at this moment in time, is this because of some unknown factor not currently being picked up by any of the models? IMO I believe this is the problem, we have southerly tracking jet with a strong PV, normally these do't go hand in hand. The unknown factor is overriding all teleconnections it appears.

Yes it's really a non correlation because in that run of milder winters the Azores high would often move in and the pattern would only go one way with a strong PV to the north.

Thats generally the form horse but as we've seen although not very cold there has been at least some seasonal weather for the UK.

A strong PV rarely works in tandem with a more amplified pattern upstream,however given recent events you would expect the models to begin to dig lower heights back into Europe, if the trend gathers pace we should expect to see some more interesting output beginning to appear in the latter stages.

[Bogman]

From a personal forecast perspective, it means that, after having predicted a brief milder anticyclonic interlude followed by a return to colder stormy conditions around Christmas, then having backed down and considered various anticyclonic options, my original prediction is all of a sudden looking feasible again.

From a layman's perspective, it means that we will probably drift into a colder, windy westerly type around Christmas. It will probably be milder than what we've seen during the first half of December, at least to begin with, with some frontal systems bringing "warm sectors" and maxima near double figures in between the colder, showery polar maritime bursts, but for the longer term it could promote more "cold zonality" with chances of marginal snow events like the ones we're having now. Also, if pressure rises over Scandinavia, a NW-SE depression track will increase the chances of low pressure digging into Europe and rising pressure to the NE sending continental air our way from the east.

Thanks mate.

[TEITS]

Interesting model output considering the recent discussions about the weather over xmas. We have had one camp suggesting very mild SW,lys and another suggesting cold, dry via HP. The reality looks to be neither because at the moment its looking likely we shall see W/WNW,lys. This means average temps for the S but possibly slightly below for the N and maybe a white xmas for the higher ground of N England/Scotland if the flow is WNW,ly.

So really a very typical, average weather pattern for the UK.

[Lancashire Lass]

The snow is now sticking. :w00t:

[phil nw.]

I must admit when previous output was pointing to a more meridonal pattern with a Euro trough digging further South i was hoping that the Azores High could build far enough north over the UK.

At least that would have given us a shot at surface cold and frosts over Christmas-just to give a seasonal feel.

The trend now is to flatten things somewhat and if this continues then indeed we could get some "proper" cold incursions from the North showing up with those heights to our south being held at bay.

Anyway i am sure we will see variations on this continue to be modelled in the next few days.

[Gavin P]

From a personal forecast perspective, it means that, after having predicted a brief milder anticyclonic interlude followed by a return to colder stormy conditions around Christmas, then having backed down and considered various anticyclonic options, my original prediction is all of a sudden looking feasible again.

From a layman's perspective, it means that we will probably drift into a colder, windy westerly type around Christmas. It will probably be milder than what we've seen during the first half of December, at least to begin with, with some frontal systems bringing "warm sectors" and maxima near double figures in between the colder, showery polar maritime bursts, but for the longer term it could promote more "cold zonality" with chances of marginal snow events like the ones we're having now. Also, if pressure rises over Scandinavia, a NW-SE depression track will increase the chances of low pressure digging into Europe and rising pressure to the NE sending continental air our way from the east.

Stating the obvious I know, but the other point is that the further into the winter we go, the colder the potential cold zonality becomes, with more and more places at risk of snow rather than rain.

[kold weather]

Well this trend blows away Ian's 'mildest Xmas period ever' idea. Still nothing that interesting but at least the current models offer the chance of a brief WNW/NW airflow which may cool things down, though I suspect the south will be above average for most of the time from the 21st through till Boxing day at least.

Wouldn't be surprised to see some snow over the Xmas period in the north, though whether it falls on the day who knows. Maybe worth a cheeky bet on glasgow getting snow?

Yes Gavin, the Irish Sea should continue to cool down if we keep getting cool zonality....though I can never bring myself to call it 'cold' zonality

[shedhead]

I must admit when previous output was pointing to a more meridonal pattern with a Euro trough digging further South i was hoping that the Azores High could build far enough north over the UK.

At least that would have given us a shot at surface cold and frosts over Christmas-just to give a seasonal feel.

The trend now is to flatten things somewhat and if this continues then indeed we could get some "proper" cold incursions from the North showing up with those heights to our south being held at bay.

Anyway i am sure we will see variations on this continue to be modelled in the next few days.

Agree Phil, once again I must confess to being surprised (pleasantly so tho) by the current outputs, there seems a real determination not to let things settle into a mild pattern. This is the polar

opposite of what used to happen 4 or 5 years ago, when whenever a change emerged we ended up with the worse possible case senario for the situation, now we suddenly seem to be making

the very best of whats on offer, a la the first half of Dec.

Edited December 16, 2011 by shedhead

[MisfitDog3]

The GFS doesn't half like it's storms at the moment doesn't it?!! The Low generating at 150 hours+ is dwarfed by the monster towards the end of the run on 320 hours onwards!! At least the former one is reasonably believable..the latter looks to embrace everything from south of the Canaries to northern Greenland! Hmmmm...doesn't give me confidence.

[phil nw.]

Agree Phil, once again I must confess to being surprised (pleasantly so tho) by the current outputs, there seems a real determination not to let things settle into a mild pattern. This is the polar

opposite of what used to happen 4 or 5 years ago, when whenever a change emerged we ended up with the worse possible case senario for the situation, now we suddenly seem to be making

the very best of whats on offer, a la the first half of Dec.

Yes you`d think with that AH modelled so close next week it would only be a matter of time before it would build pushing the jet north of the UK and we get swamped by SWesterlys.

The tendency of a more southerly tracking jet than usual seems to be a constant these days-in spite of the strong vortex.

You could say from a coldies pov that we have been lucky to escape a much milder setup under the circumstances.

Edited December 16, 2011 by phil n.warks.

[shedhead]

Yes you`d think with that AH modelled so close next week it would only be a matter of time before it would build pushing the jet north of the UK and we get swamped by SWesterlys.

The tendency of a more southerly tracking jet than usual seems to be a constant these days-in spite of the strong vortex.

You could say from a coldies pov that we have been lucky to escape a much milder setup under the circumstances.

Very much so, you do get the feeling that the first half of Dec 05 would have seen a lot more mild SW'erlies given the same big picture, so I guess the more S tracking Jet must be

a big player in what is currently manifesting itself.

[pyrotech]

Can some one comment at the end of the run on current GFS , obviously deep in Fi but what are 850mb temps of +12 doing over Canada?

I can not remember temps like that for the time of year, can someone with more knowledge enlighten me on the chance of that happening, how or what could cause it and if its normal. Is it a data failure by the GFS or feasable.

I just really did not expect to see such high 850mb temps over the UK let alone Canada ( further North)

Anyone able to comment on this? Or is it a stupid question?

Edited December 16, 2011 by pyrotech

[Methuselah]

So am I Stew. Sorry for one liner but what else is there to say in answer to that. My post 689 very much supports that train of thought so I'm intrigued that GP has these thoughts.

BFTP

Models have been very up and down pete, not consistent

BFTP

And, from my own experience, that often presages what I call a mixed bag: changeable and highly unpredictable weather.

[Frosty.]

The models show the weather turning much milder towards the middle of next week with temps up to 10-13c in most of the uk and with spells of rain with windy conditions at times, there is a chance of it becoming a little colder towards the end of next week with the snow risk increasing again for northern hills. This mornings snow event was well overhyped nonsense although some areas have seen a thin covering, total overkill by the meto for what turned out to be patchy snow for many.

[shedhead]

The models show the weather turning much milder towards the middle of next week with temps up to 10-13c in most of the uk and with spells of rain with windy conditions at times, there is a chance of it becoming a little colder towards the end of next week with the snow risk increasing again for northern hills. This mornings snow event was well overhyped nonsense although some areas have seen a thin covering, total overkill by the meto for what turned out to be patchy snow for many.

Was always likely to be the case PL from about 48hrs out. In truth the raft of warnings issued were fully justifiable prior to that considering the outputs, but ever since Wednesday all models began significantly downgrading the risk of severe weather, but the MO still crashed on regardless. When you think of the snow and ice around this time last year that only constitued Yellow Warnings, the Amber issued for the Midlands early yesterday afternoon was massively OTT and in no way whatsoever reflected the model outputs at the time. No one is suggesting it's not a difficult job and in marginal situation it's prudent to air on the side of caution, but if that little bit of sleet and wet snow was worthy of an Amber, what are they going to do when/if any real snow and ice arrive in rhe New Year?

[Methuselah]

But, in all fairness, it wasn't the models, MetO or other respectable forecasters that did the hyping. It was, IMO, the work of a gaggle of 'alternative' forecasters and the gutter press, trying to demud their faces after all the wildly inaccurate 'Snowmageddon' forecasts that have bedeviled us since September. As usual!

[chionomaniac]

I knew that last line in PL's post would get a response!

Let's stick to the models please!

[danm]

The models show the weather turning much milder towards the middle of next week with temps up to 10-13c in most of the uk and with spells of rain with windy conditions at times, there is a chance of it becoming a little colder towards the end of next week with the snow risk increasing again for northern hills. This mornings snow event was well overhyped nonsense although some areas have seen a thin covering, total overkill by the meto for what turned out to be patchy snow for many.

Bit harsh that. The way the low pressure system was modeled earlier in the week meant that if it took a more northerly track there could have been some very strong winds over a densely populated region. As it turned out, closer to the day the models predicted it staying further south, but with the possibility of snow. I don't think the Met ever stated that there would be anything particularly heavy - they just said that the rain will turn to snow and this morning's rush hour could be tricky in a few places.

[Liam J]

This mornings snow event was well overhyped nonsense although some areas have seen a thin covering, total overkill by the meto for what turned out to be patchy snow for many.

This sentence is nonsense, a number of places over NW England have seen 2-3'' of snow today which is rather more than a thin covering, which was indicated by the models but perhaps to a lesser extent than the eventual outcome today.

Anyway this is the MOD thread, lets keep it as such, plenty of other threads to discuss the snow or lack of it.

Edited December 16, 2011 by Liam J