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Model Output Discussion - The Start Of Winter

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Some snowfall forecast before the thaw

Chart weatherbell

 

post-12275-0-15355100-1417954334_thumb.p

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

Regarding next weekend.

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Regarding next weekend.

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

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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...!

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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.

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

Yes but wind the focus for attention really.

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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.

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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.

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Yes but wind the focus for attention really.

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

Edited by blizzard81

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Edit from above :

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

Edited by fergieweather

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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!

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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!!/

 

 

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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 , :cold:  :drinks:

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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.

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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

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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.

 

post-4523-0-84826300-1417951823_thumb.gi

 

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

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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.

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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.  :good:

 

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

 

gfsnh-2014120312-0-216.png?12gfsnh-0-120.png?12

Edited by Mucka

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

 

 

 

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

 

UN144-21.GIF?07-17UN144-7.GIF?07-17

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