Model Output Discussion - 5th December - 11th December

[Nick F]

http://www.meteociel...H1-120.GIF?05-0

Im still in the game for non Zonal...

S

Short-lived cold snap on Friday before the next Atlantic system rolls in and merges with the low off Norway - GFS has come on board with this now after showing more of ridge to the west on earlier runs.

Nonetheless, 12z ECM shows an interesting secondary wave/low dropping down from the NW across Ireland, Wales and western England on Friday - which could create a snow event.

Looking pretty zonal to me into the medium range - though still some uncertainty on how far south the jet will track - ECM op still prefering a more southerly track than GFS - which would be cooler/colder, wetter and windier for the UK.

[bluearmy]

watching the 12z op play with the ridge in western russia towards svaalbard. this could cut off the scandi trough. (but unlikely given the strength of the flow). only another variation from the model and its in fi but possibly interesting. i can see loads of cold rain for the southern half of the uk on that 12z ecm run. maybe some white stuff for high ground.

Edited December 5, 2011 by bluearmy

[WhiteFox]

Ok.....lets agree on chilly conditions? No concessions needed and this post of yours is nice and clear.

ECM 12z could be interesting....chucking a storm or two at us

BFTP

Spoken like a true debater! The thing is, you both know that the weather is never black & white (but you are both like me and don't ever want to back down!): a cold stratosphere does not mean never-ending flat pattern in the same way that a warm stratosphere does not mean never-ending northern blocking.

Looking at the current pattern, given the state of the stratosphere and the implied lack of potential for northern blocking, I would take the current setup quite happily. We are likely to see occasional PM bursts and the odd toppler. Some seem to expect a record-breaker every month these days, but this of course has never been the case. The setup we are seeing right now is not far from normal over any period (I'm not entering into a GW debate!) you take in history. Yes, anybody can pick out a few years where there was extensive blocking, but take any 20 year period of recorded weather history and you would see fairly similar conditions: periods of zonality and periods of colder weather. Mostly, the best you will get is a week of cold conditions. Last December was very much the outlier in terms of overall temperature and will, probably, continue to be so for many decades. Sub-zero CET months have always been a rarity and, probably, always will be.

[Weather-history]

http://www.meteociel...H1-120.GIF?05-0

Im still in the game for non Zonal...

S

Looks zonal to me. All 3 main models look zonal

[Liam J]

In the short term the 12z models are in agreement of a significant wind storm event over Northern Britain during Thursday with a sub 965hpa depression crossing the UK.

Meto quick off the mark with this one already with early warnings issued for gusts to 80mph, they must be expecting a sizeable impact from this storm and they are usually conservative with such events.

Stormy and zonal outlook it has to be said.

Edited December 5, 2011 by Liam J

[bluearmy]

Looks zonal to me. All 3 main models look zonal

i agree - flow is west to east. cold zonality but definitely zonal.

[Summer Sun]

ECM is rather stormy tonight

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

http://www.wetterzentrale.de/pics/Recm1921.gif

http://www.wetterzentrale.de/pics/Recm2161.gif

[Grimsby Snow Lover]

What I have noticed on tonights ECM especially is how strong the Siberian high seems to be getting. It certainly seems to be a little further west on this run. I wouldn't be suprised if this became more of a player over the next few weeks, especially since hight rises over Greenland currently look limited over the next week to 10 days at least.

http://www.wetterzentrale.de/pics/Recm2161.gif

[Summer Sun]

Final ECM

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

[phil nw.]

T72hrs. Fax is typical of a cooler Zonal Pattern.Milder wedge of air across the UK ahead of the next Low approaching from the West

A deep and active system to sweep South East with a return of Polar air in it`s wake.Snow returning to the North.

Edited December 5, 2011 by phil n.warks.

[Tim Bland]

All looking good for the scotish ski areas! Hope they will open soon

[nick sussex]

Generally after alot of chopping and changing the models look like they've finally agreed on the way forward. It's always disappointing that after some interesting charts they all decide to jump on the solution that the majority in here don't want to see.

I think we can see why I'm always underwhelmed by PM incursions, either the models overplay the southwards extent of cold or turn them into blink and you'll miss it affairs!

Of course some people will see snow from them, as we've seen from the last few days but generally unless you're on much higher ground it's a slushfest! not exactly crisp snow and sledging!

Before the models start their slippery slide into the PV abyss the ECM throws a chunk of interest at 120hrs by taking that shortwave east into the UK, at that point the ECM showed some promise, after that though we can't separate out that energy spilling east and it phases into troughing in Norway.

Eventually we might see the PV edge west and high pressure build in from the sw, I still think if theres to be a decent cold spell it's going to have to come from the east at least initially.

Lets see what the ECM ensembles have to show later with that shortwave, do any of them disrupt a little more energy off that low to the west?

It's hard to imagine a last minute reprieve given such a strong signal for that PV to rush back to it's partner in crime north of Iceland but it has been a rather weird week in the models.

[Gibby]

Hi everyone. Here's a look at the 12zs of GFS, UKMO and ECM as well as a glance at the GFS Ensembles.

GFS shows a continuation of the Westerly regime of weather for the next week or so at least with fresh to strong winds at times and troughs of Low pressure bringing periods of rain followed by showers and then a drier day or so as ridges of high pressure pass by. It will be on the cold side at times with some snow on high ground in the North though not a major problem south of Scotland. In FI a continuation of a changeable Westerly type continues with potentially stormy conditions should the deep Low pressure on the operational over England verify at 300+ hrs.

In the GFS Ensembles the operational shows a typical sine wave pattern that is typical of a mobile, changeable theme while the mean of the pack shows 850's staying close to the long term mean after the rather below normal conditions this week.

UKMO shows a windy changeable 6 days in tonights 12z run with Low pressure to the North steering strong and sometimes chilly West or WNW winds with showers affecting many Western and Northern areas, some of which falling as snow on many Northern hills especially in western Scotland at first. On Thursday a milder and cloudy day develops as a new Low pressure pushes troughs across the UK before a renewed pull of cold and showery NW winds develop by the weekend. Further Low pressure then knocks on the door at 144hrs to keep the mobile weather pattern continuing.

ECM finally follows the same trend with rather cold and unsettled weather looking to continue throughout it's run. There will be some snow in the North at times while conversely some milder interludes could occur especially towards the Southern half of Britain. Late in the run the general theme continues unchanged with further Low pressures crossing east to the North.

In summary the Atlantic looks like ruling unabated over the next few weeks. That's not to exclude the risk of further snowfall for northern hills at times while most places see showers or rain at times with frost and fog remaining a little elusive as wind and cloud amounts dictate against it.

[Thundery wintry showers]

Agreed, the current outlook is about as zonal as it gets. That said, there is still no consensus on anything particularly mild, the main theme is for near-average temperatures with some warmer interludes when the fronts pass over and falling a little below average in the polar maritime incursions.

The progged setup does sometimes give wet snowfalls from the Midlands northwards but as a general rule lying snow is likely to be restricted to northern hills as per Gibby's summary.

The general opinion of polar maritime blasts vs hypothetical easterlies rather reflects the fact that most of the contributors live in southern England. Polar maritime incursions are usually poor for snow lovers south of the Midlands, and even in the Midlands and north of England snow often struggles to lie near sea level, but in Scotland and Northern Ireland it is a very different story- snow has lay widely to low levels across Scotland today for instance. Similarly, easterly outbreaks may be the most reliable bet for snow lovers in southern England but in western areas it is a very different story, and don't forget that just as we get watered-down north-westerlies and northerlies, we sometimes get dry cloudy south-easterlies with high pressure stuck over Scandinavia and a strong polar vortex sat over Iceland.

Thus, in short, I think snow lovers in Scotland have a lot more to be happy about with the current outlook than the ones in southern England, and calling it a "poor" outlook from that perspective is sensitive to location.

[wolvesfan]

Evening all,

Overall IMHO i think we're in a lot better position in respects of cold for the UK than a couple of weeks ago.Temperatures have tumbled and we're now seeing below average values.Everyone won't see snow but a lot happening nevertheless.

We might not be seeing severe cold but taking everything into consideration strat,etc we could be doing a lot worse,bartlett and euro high for example.

I for one will gladly take tonights output its not historic or record breaking but it's a damn site better than what we've had to endure this autumn.

[nick sussex]

Agreed, the current outlook is about as zonal as it gets. That said, there is still no consensus on anything particularly mild, the main theme is for near-average temperatures with some warmer interludes when the fronts pass over and falling a little below average in the polar maritime incursions.

The progged setup does sometimes give wet snowfalls from the Midlands northwards but as a general rule lying snow is likely to be restricted to northern hills as per Gibby's summary.

The general opinion of polar maritime blasts vs hypothetical easterlies rather reflects the fact that most of the contributors live in southern England. Polar maritime incursions are usually poor for snow lovers south of the Midlands, and even in the Midlands and north of England snow often struggles to lie near sea level, but in Scotland and Northern Ireland it is a very different story- snow has lay widely to low levels across Scotland today for instance. Similarly, easterly outbreaks may be the most reliable bet for snow lovers in southern England but in western areas it is a very different story, and don't forget that just as we get watered-down north-westerlies and northerlies, we sometimes get dry cloudy south-easterlies with high pressure stuck over Scandinavia and a strong polar vortex sat over Iceland.

Thus, in short, I think snow lovers in Scotland have a lot more to be happy about with the current outlook than the ones in southern England, and calling it a "poor" outlook from that perspective is sensitive to location.

Yes of course it's really down to where you live as to what winter synoptics you prefer.

Living in Sussex before here in sw France I always looked out for a ne or easterly flow, it's a bit different now, for the mountains a strong unstable nw flow delivers lots of snow but if I want long lasting snow at my 1,250 feet elevation it really has to come from the north to east.

However the problem with the current type of zonality is that it only delivers even to northern areas with some amplification, lose that and with a strong PV the Euro high will tilt the jet unfavourably.

Now if we had proper colder zonality that would spread the fun around but thats a rare thing in recent years.

[ANYWEATHER]

It has to be said that given the or one of the warmest October and November on record we are now looking at some normal stuff for the time of year. Its easy to be forgiven what is normal for this Country in the last 18 months. January 2010, coldest Winter for at least 30 years then a record breaking six weeks of record cold weather in November and December, and then a complete flip this year with a record warm spell in April and October and not to mention some of the driest conditions in central and eastern England for about 100 years!......... Looks as though the Scottish Ski industry will be busy from now on! Gfs has to be said has been performing very badly over the last few days although its my preference model! So Cold at times, with some shots of milder air , snow for Snowdonia and further North at that elavation, wind and cold rain at times further South, with some drier, milder inturludes and potentially Stormy at times just about everywhere.......Thats my take on the models and I must say the Ecm proudly wears the feather in the Cap over the last few days..!

[spindrift1980]

The general opinion of polar maritime blasts vs hypothetical easterlies rather reflects the fact that most of the contributors live in southern England. Polar maritime incursions are usually poor for snow lovers south of the Midlands, and even in the Midlands and north of England snow often struggles to lie near sea level, but in Scotland and Northern Ireland it is a very different story- snow has lay widely to low levels across Scotland today for instance.

Thus, in short, I think snow lovers in Scotland have a lot more to be happy about with the current outlook than the ones in southern England, and calling it a "poor" outlook from that perspective is sensitive to location.

Absolutely. Plenty of crisp, powdery stuff on offer up here, even at low altitudes. Personally, I'm always happy to see a pM incursion.

[shedhead]

i agree - flow is west to east. cold zonality but definitely zonal.

Cold zonal in the north perhaps across the next week or so, but average zonal for most and I'd even go as far as to say rather mild zonal for the far south

[Geordiesnow]

I still go by the rule of thumb that anything past 96 hours is subject to change and that has not changed but the models appear to be agreeing that any meaningful ridge has backtracked somewhat but you never know what the models might hint at further down the line.

Regarding the 18Z run, I'll be keeping an eye out on that low for Thursday into Friday and see how much cold air is mixed in and where the PPN is because as I said earlier, blizzards could be possible even down at lower levels for a time across Northern Scotland in particular and everywhere else up in the North East of the UK especially could see severe gales so on a personal point of view some interesting weather potentially.

We'll see if the 18Z trends towards the ECM for the first part of the run at least but remember the ECM tends to have a blocking bias so we have to bear that in mind but I don't think the trend back to milder weather is all that clear cut. The GFS's set up of a high ridging in after the cold shot which in turns into a Euro high has not been followed by the UKMO/ECM as of yet so the outlook could be alot worse atm.

[jpwild]

Snowing in Disley now. Looks like wet snow can't be sure though. Watching the radar I expect more to come up here. Hopefully this will settle.

[nick sussex]

The ECM ensemble maps upto 168hrs don't have alot of support for that shortwave at 120hrs, just really the control run.

The extended ensembles are average for Holland, I'd call them beige! basically drab and uninspiring!

http://www.weerplaza.nl/15daagseverwachting/default.asp?type=eps_pluim

Of course if we're dealing with a mobile pattern then you'd expect northern areas of the UK to tap into the odd colder day, but we have to watch high pressure to the south which could eventually ridge ne changing the jet axis.

[SMU]

Looks zonal to me. All 3 main models look zonal

thats not a zonal chart- however the following charts I have to conceed are progressive-

I was expecting a bit more trough disruption that the ECm demonstrated on its OP run at 168

steve

Edited December 5, 2011 by Steve Murr

[damianslaw]

Very volatile situation and ever changing it seems - reliable timeframe remains about 96 hrs. Models now saying no to any signficant pressure rises this weekend - shame as I was hoping for a window of dry decent cold weather and some sunshine, alas a window of about 24 hours looks possible - but the ridge looks very weak and the atlantic looks like it wants to quickly knock on its doors.

Longer term - can't see much changing remaining very unsettled with further spells of wind, rain and snow for northern high ground and possibly scotland. Jet titled slightly NW-SE so some polar maritime bursts into the NW from time to time.

All in all very standard December weather. What may be different this year compared to many recent ones is the absence of dry settled conditions mid-month, its been a long long time since we have seen the atlantic this active, it had to happen sooner or later, it will run out of steam eventually though..

[nick sussex]

thats not a zonal chart- however the following charts I have to conceed are progressive-

I was expecting a bit more trough disruption that the ECm demonstrated on its OP run at 168

steve

Have you checked the ensemble maps Steve:

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!120!pop!od!enfo!enplot!2011120512!!/

Actually theres a few more than I initially thought with regards to that shortwave. Yes at 120hrs it promised much then failed to deliver!