Model Output Discussion - The Start Of Winter

[knocker]

Some snowfall forecast before the thaw

Chart weatherbell

 

[fergieweather]

His post states significant uncertainties even at the start of day 6 - 15 period ?

Regarding next weekend.

[blizzard81]

Regarding next weekend.

Hi Ian, is that in relation to how cold it gets?

[fergieweather]

A wee, sneaky peek at the Reading EPSgram shows this up well - big spread after Saturday, the control and deterministic are at the top of the range at the end of forecast period.

 

http://i.imgur.com/55jJzgi.gif

... whereas they were both knotted together towards bottom end range by close of period in yesterday's 12z...!

[ukpaul]

Some snowfall forecast before the thaw

Chart weatherbell

 

Snowfall always comes before a thaw.......

 

What is notable is the ragged state of the pv around Canada/Greenland in the latter stages of extended runs at the moment, tying that in with a significant warming (not a technical SSW but that may come) looks interesting. Current talk on the strat thread is how a SSW affects a -AO versus a positive one, it seems that it would me more likely to reinforce a pattern with a -AO as opposed to exploding it with unknown consequences for a positive one.

[fergieweather]

Hi Ian, is that in relation to how cold it gets?

Yes but wind the focus for attention really.

[blizzard81]

http://www.meteo24.fr/fr/home/meteo-france-et-europe/passion-meteo/ensemble-de-previsions.html?eps=london

And in the extended, plenty of clusters over a wide spread.

Hi BA, I don't know what the London ensembles showed on last night's 12z but if you compare this morning's Debilt ensembles with last night's, there are quite a lot more colder runs this morning post day 10.

[nick sussex]

I think over the last month we've seen a cycle of bias in the NWP especially at longer ranges.

 

The pattern seems to have been, they project a flat pattern upstream, then they switch to a more amplified solution, then they reduce that amplification but are still more amplified than the original long term view.

 

For this reason I'd be a bit sceptical of the ECM at day ten, indeed if you look at some of the GEFS that's now showing some more amplified solutions. I don't think I've know this type of situation before especially with modelling within T144hrs which suddenly flattens the pattern out.

 

A good point in case is the UKMO over recent weeks which you couldn't even trust at T120hrs and has often been the most amplified, in fact the GFS has been the least jumpy in that regard.

 

It's been slow to amplify but rarely has it ever got to the extremes of the ECM or the UKMO.

[blizzard81]

Yes but wind the focus for attention really.

Thanks Ian. I thought the worst of the winds would be over by then?

Edited December 7, 2014 by blizzard81

[fergieweather]

Edit from above :

Yes (with phase of wintry PPN possible even in the S) but wind the focus for attention really.

Edited December 7, 2014 by fergieweather

[bluearmy]

Hi BA, I don't know what the London ensembles showed on last night's 12z but if you compare this morning's Debilt ensembles with last night's, there are quite a lot more colder runs this morning post day 10.

Anecdotally, (I don't save the output)' I'd say the London 00z suite had fewer cold runs in the extended than the 00z. (But the trend at the end is in a downward direction so a straw to clutch there!) tbh, post day 10 is real lala land for detail. there is no real trend for mild nor cold. chilly to on the mild side covers the envelope. all to play for as we approach the holiday period and wait to see if the current pattern is likely to evolve into anything else. So far today, sniffs that the Russian ridge could cut off the nw euro trough but you need to be downwind with a very keen since of smell to pick them up!

[Nouska]

A timely freebie from the ECM website - 700hPa wind and RH for out to T120.

 

http://old.ecmwf.int/samples/d/inspect/teasers/samplers/banner/rh_and_wind!700%20hPa!120!Europe!pop!od!oper!w_uv_rh!2014120700!!/

[Cloud 10]

Still lots of uncertainty regarding that day 5 storm from the 00z ECM,although looking at the postage stamps there are numerous members going for something similar.

 

http://old.ecmwf.int/samples/d/inspect/teasers/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!120!pop!od!enfo!enplot!2014011300!!/

 

 

[legritter]

Charts currently showing interesting weather for the next 7/8 days with some lucky posters seeing some snow ,also towards the end of the working week depending on synoptics a few more of us could join in the fun .I also take on board signs of temperatures recovering past 8 days as high pressure to our s west regains any lost ground BUT beyond this say 12 days away is realy pushing medium range modelling to the limit ,you have only got to remember last winter and how that Monster broke out of its cage .Realy enjoying our forum with its daily changes ,ebbing and flowing ,Thats Meteorology for you ,Hands up those who would like a supercomputer for christmas that is accurate out to 4 weeks ,No thanks lets continue to enjoy the uncertainty ,  

[Barry12]

Sorry mods if you want to put this in another thread but I think its disrespectful.

 

I am not aware Tamara gets paid a heavy fee for the time and effort she puts in ? if you can highlight the 'ded cert' she mentions please provide a link.

 

Its also been pointed our that changes in NH patterns doesn't always lead to snow IMBY on a specific date 

 

If this was a exact science we wouldn't need this thread and ps its still FI

She chooses to put time and effort in as I assume she has an interest in the weather and enjoys it, like most of us on here. It's not like it's a chore. I apologise if I caused any disrespect.

I know changes in the NH doesn't always lead to cold and snow in the UK, but there hasn't been a change in the NH either, the NH profile has been the same for weeks.

It is FI, but when we have the Met Office confident that there won't be a significant pattern change in the 10-15 day range, then I'm not filled with much hope.

[A.J]

some posts and one-liners in here that would be better served if communicated by pm.....current model output discussion only in here please....thanks

[Tamara]

ECM has changed quite significantly this morning. It gets cold temporarily for the North at day 6 with -4 uppers. Positive uppers for the south, so average to above most likely. Then at day 7 we get a cool NW with probably average temperatures. The UKMO and GFS have heights moving towards Greenland while the ECM doesn't. Until We see the 12z's we shouldn't worry as it's the odd one out. The medium term outlook is a worry though. I think the likes of Tamara have some explaining to do as to why this ded cert pattern change is looking unlikely to happen.

Thanks for this Barry   You are however wrong on both counts you suggest :

 

1) I have explained in extended detail, as much as I am able, the progress of the patterns thus far from autumn (see first posts back in October in OPI thread and then continued on this MOD thread thereafter last month and into this). Many of these posts have had copied entries to illustrate continuity of thought so that progress can be checked and thereby form a very transparent check for accuracy. But most importantly of all (as far as I am concerned) for learning when mistakes are made - as they most certainly will be in a science as complicated and unpredictable when it comes to evaluating weather and weather patterns.

 

2) Its the first week of December with at least 11 weeks of official winter remaining.  None of my posts have proposed any 'dead cert pattern change' till the second half of December at the very earliest. The key here though is 'very earliest' because there was an outside chance (as I and others more technically gifted than me had observed) that the accelerated advance cold pattern feedbacks apparent this autumn might deliver an earlier route to polar vortex demise sufficient for deeper more extenseive cold to arrive than the polar maritime incursions this coming week. These toppling events on their own are still more than last winter managed to muster in its 3 month span....

 

The feedbacks discussed on here and in places like the stratosphere thread are based on scientific theory which have a large element of proven success - otherwise we wouldn't have analogues and composites to draw on from previous years. Once again - a marvellous opportunity to observe progress and try to learn something. If it snows at the end of it all, then hey well that is a large reward in itself for watching and hopefully learning something  Far better, I think, than moaning one week into winter because premature expectations for instant gratification of preferred weather type haven't yet been granted or don't appear to be granted in the heart of December time period  . But again, this brings us back to managing expectations, or, if you don't mind me saying so, your own inability to manage them. I know for my part, I try to help do this - and hence why your post is all the more bewildering

 

So to more of the facts, rather than incorrect perceptions :

 

The shorter term sees a very seasonal prospect with an often below average week ahead with high impact weather conditions expected. High impact conditions that take on a more wintry flavour than those witnessed a year back when a cyclonic pattern was evident. Those in the north and in Scotland will indeed be wondering what the fuss is about with very high winds and blizzard conditions expected most particularly for upland regions. Wintriness penetrating a little further south at times too.

 

It is the modelling following this where the interference of the Azores High as a spoiler appears to raise it thorny head once more again. We see the prospect of a weak poleward Hadley cell. This is supportive of poleward propagating (sub tropical) anticyclones to mid latitudes (i.e Azores High) combined with positive Atmosphere and Angular Momentum (+AAM). The energy budget deficit and then rebalancing in the atmosphere poleward is contributory to a spike in the AO. It is this which largely (probably?) lies beyond your own obvious angst and maybe one or two others. But ( if taken like this in isolation and out of context with everything else that is going on right now, and expected to evolve through December) completely misses the bigger picture.

 

Here are several reasons how and why:

 

Further likely re-enforcing of warming of the western Nino regions is likely to weaken the Hadley Cell, especially as the other hemisphere feedbacks tighten their grip in tandem. Why is this relevant?

 

Weaker eddy heat flux into the mid latitudes occurs as ENSO warming occurs in the region which reverses the Ferrel Cell circulation and meridional mass field/Polar vortex gradient and that, self evidently, leads in turn to enhanced opportunity for stratospheric wave attack to lead to higher latitude blocking.  The sub tropical ridging (think Azores High again) is weakened and retracted in this process as the higher sea temperatures supporting these anticyclones is weakened. This is a key to the +NAO spoiling conundrum appearing in seasonal forecasts. But we have to be patient and watch to see when this happens.....

 

Much explained winter SAI feedbacks ( which, despite the recent delays due to a short period of Asian troughing) are back on track to re-strengthen the Siberian High and should resume strong wave activity on the vortex through the second half of December.

 

A +PDO and a cool Kuroshio-Oyashio extension (basically in simple terms two water currents found over the NW Pacific) are a common product of El Nino. Warmer than normal SST's build up over the Bering Sea and Sea of Okhotsch. This correlates extremely highly with a displaced (strong) Pacific Jetstream (tick box checklist so far) and evolution to blocking over the pole.

 

The stratosphere is belying its apparently unfavourable strengthening at upper levels and looks destined to set itself up for a bigger fall by doing so. Best remember that bicycle wheel analogy here. The faster the vortex (wheel) spins..the more spectacular the outcome when something is suddenly jammed right into the heart of it. Think SSW   Why should we continue to expect an SSW? We know that it cannot guarantee a cold spell for the UK, but if one is seeking guarantees from the weather than maybe they should seek another hobby and another forum....

  

In terms of solar background - geomagnetic activity has been at a record low level back to 1932. With the solar polar field flipping polarity (ie descent from twin peaked maximum) no further increase is likely in geomagnetic activity (circa 80 to 90 sunspots)   Current predicted and observed size makes this the smallest sunspot cycle since 1914. Current activity comes on the back of two winters with Nina pre-disposed conditions. Ozone concentrations build up significantly on the back of dual winters of nina like conditions and these contribute to an SSW occurring. Taking into account prevailing/ongoing sunspot activity combined with an _QBO then this also points strongly towards an SSW occuring

 

Adding all this to the 7/8/1 phasing of the MJO and Greenland wave activity response still currently well enough on track for late in the month, the massive witnessed autumn Siberian snow feedbacks in complete resumption as head towards mid December, then with the changing wave lengths are increasingly on course to bring about a vortex that might spectacularly resemble a beaten up/crushed coke can into the New Year.

 

An early 2015 SSW, if occurring ( as evidence strongly supports),doesn't guarantee a UK freeze, as much as anywhere else - but if one is not prepared to take the selective wintry prospects of the coming week and wait and watch and test the accuracy of all of the above evolve in progress, then best to save frustration for elsewhere and not to post too much on this thread

Edited December 7, 2014 by Tamara תָּמָר

[ukpaul]

Thank you Tamara for, again, an excellently explained look at what may transpire. 

 

Given this level of detail, with caveats, it gives people a lot to look for when chart watching in the coming weeks (and not take for granted, as some appear to do with long range musings). It certainly beats one liners or a cherry picked chart accompanied by a snarky comment!

 

For me, the state of the strat and its relationship with the current tropospheric output is fascinating. The regular warmings appear to be having as, compared to last year for example, a disproportionate effect. With the credible suggestions of something more extreme in the next month or so, then the results of that would be fascinating.

 

 

via Chiono 1hpa at 384h (n.b. strat forecasts have a greater reliability at such a range)

[BlueHedgehog074]

I suppose the only thing that has changed with the weather is that the blocking we had over Europe/Scandinavia is generally concentrated further East towards Russia, and with the UK looking to become more influenced by Atlantic dominated weather from the West. It is kind of a shame to see the Northerly for late next week has become somewhat eradicated on the models. And more of a North-Westerly flow probably looking more likely instead. Which is still better than a mild South-Westerly flow if it's the sort of thing you hate. Having said that, the general pattern for next week seems to be there, with the UK experiencing some vicious Lows at times, and a general flow still likely between the West or North-West.

Maybe still not impossible that the models might improve the Northerly again (especially if they're being too eager trying to flatten the pattern out). But would have to agree that it does seem to be that case that when a Northerly gets modelled in FI, the models enjoy trying to stamp their foot all over it. I think, in a way, having a Northerly suddenly turn up within the 48/72 hour time-frame would deliver much more promising results.

For now, though, those to the North/North-West should see some continued wintry surprises into next week from wintry showers or longer spells of rain, sleet, or snow, especially on high ground. Rain more likely for Southern areas, but perhaps wintry at times on the highest ground. And maybe something slightly more wintrier for some lower-level areas (perhaps around 200/300m or above) in the South during the more cooler, brighter, showery periods. It could still be possible things could change for the better for more areas to see something more wintrier. Definitely not totally over yet. However, at least there are further chances for the white stuff this Winter should this week fail to fill many of the cold and snow fans' hearts full of snowy excitement.

[Frosty.]

An exciting week of weather ahead with everything including the kitchen sink.. I think stormy weather will be the main headline from midweek with coastal storm surges, lots of wintry showers with snow on hills, even in the south later. Looking further ahead, it's rinse and repeat with a nw / se aligned jet with lows crashing southeastwards bringing bouts of wet and windy weather like next Tuesday but with cold air digging in behind active cold fronts and during any quieter intervals, widespread frosts..it's all action in the run up to Xmas and probably beyond. :-)

Edited December 7, 2014 by Paul
Removed the un-needed baiting.

[Mucka]

Mixed signals this morning going into this evenings output. The general theme this morning was for a shallower trough and for the pattern to slowly flatten. ECM anomaly ens charts day 10 certainly show no positive move toward any blocking day 10 and this mornings ECM was uninspiring.

But...

There is also still a strong enough hint that pressure will rise to the NE and blocking form the final 3rd of the month. Hopefully better output this evening but more especially through early next week where I hope to see a stronger signal for a pattern change. i'm still confident we will be seeing good prospects ahead by mid month but want to see things improve over the next couple of days.

 

Meanwhile good look on catching an elusive snow shower in the coming week. 

 

Edit

 

Just a quick comparison of GFS charts for the 12th from just 4 days ago to today to show 5 days is along time in model land

 

Edited December 7, 2014 by Mucka

[Cloud 10]

No sign of the 00z ECM day 5 secondary LP on this evenings GFS or UKMO.

 

 

 

[Barry12]

UKMO at day 6 looks better, snow would surely fall to lower levels in Northern England, Ireland and Scotland.

 

[knocker]

Michael Ventrice â€@MJVentrice

ENSO + MJO 500H analogs that best match current State. Hello western North American ridge. GOA trough still there pic.twitter.com/Kg49kxCDrI

[Grimsby Snow Lover]

Michael Ventrice â€@MJVentrice

ENSO + MJO 500H analogs that best match current State. Hello western North American ridge. GOA trough still there pic.twitter.com/Kg49kxCDrI

Hi knocker, what exactly does this mean for the Uk? Sorry I dont understand the jargon. Thanks GSL