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Model output discussion - Post SSW - Will it turn cold?


Paul
Message added by Paul

Please only post model discussion in this thread. 

For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
https://www.netweather.tv/forum/forum/142-regional-discussions/

Thank you!

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Posted
  • Location: Tunbridge Wells, Kent
  • Location: Tunbridge Wells, Kent
2 hours ago, John Badrick said:

Please no repeat of "that ECM" a few years ago when everything was a dead cert, even down to t48 and then... well we know what. Can remember even the met, bbc etc were certain. Is this set up Any different? Are we in a better position? Or could it all go horribly wrong again?

As I recall, although the Model output at the time was pointing to a coldish outlook, the ECM (and most of it's ensemble set) went for a very extreme outcome for 1 run.

There is far more model agreement this time, both in terms of cross model consensus and consistencies between runs for the same model. Add this to the background teleconnections as a result of the SSW and things look a lot more solid this time round.

It should be noted that there are still 4 or 5 ensemble members on the 06z GFS that don't really ever get that cold, so a complete collapse is I suppose possible until we see those blues and purples heading over the North Sea and the low countries at +72 or so.

What would concern me more based on 15 years or so of model watching, would be that some historic cold spells have shown similarly epic output in the 8-14 day range only for very incremental downgrades to occur in terms of severity or longevity (or both) which has resulted in a bit of a watered down version when the spell actually arrives, albeit with some noteworthy snow events on occasions. The two instances that I can recall the event being as severe as the models were December 2010 and March 2013, the latter event offering some hope to us here as that was also a SSW event.

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20 minutes ago, Daniel* said:

What we seem to be looking at predates the internet era, a classic easterly has been in deep hibernation like a dormant volcano. I won’t mention Feb 2009 that was very fleeting, it goes to show how rare synoptics like this are, when in Greater London we had the most disruptive snowfall since 1991 - 18 years.

And 2005 not really memorable not on level with may come. Last reference points has to be 1991 and this looks ruddy good if better, mean drops to -10C in London at day 8 looks like beast wants to pay a visit I think it’s coming... been a long time since. Exciting! 

B9492140-CE86-4B07-97A5-A7DFD0D45DC4.thumb.gif.bafce07b96f7c03462802bcb8a58d578.gif

 

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22 minutes ago, Daniel* said:

What we seem to be looking at predates the internet era, a classic easterly has been in deep hibernation like a dormant volcano. I won’t mention Feb 2009 that was very fleeting, it goes to show how rare synoptics like this are, when in Greater London we had the most disruptive snowfall since 1991 - 18 years.

And 2005 not really memorable not on level with may come. Last reference points has to be 1991 and this looks ruddy good if better, mean drops to -10C in London at day 8 looks like beast wants to pay a visit I think it’s coming... been a long time since. Exciting! 

B9492140-CE86-4B07-97A5-A7DFD0D45DC4.thumb.gif.bafce07b96f7c03462802bcb8a58d578.gif

Yep spot on as ever Daniel these set ups are very rare like the sudden severe weather set ups

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Posted
  • Location: Tunbridge Wells, Kent
  • Location: Tunbridge Wells, Kent
28 minutes ago, Daniel* said:

What we seem to be looking at predates the internet era, a classic easterly has been in deep hibernation like a dormant volcano. I won’t mention Feb 2009 that was very fleeting, it goes to show how rare synoptics like this are, when in Greater London we had the most disruptive snowfall since 1991 - 18 years.

And 2005 not really memorable not on level with may come. Last reference points has to be 1991 and this looks ruddy good if better, mean drops to -10C in London at day 8 looks like beast wants to pay a visit I think it’s coming... been a long time since. Exciting! 

B9492140-CE86-4B07-97A5-A7DFD0D45DC4.thumb.gif.bafce07b96f7c03462802bcb8a58d578.gif

If my recollection is correct, the build up to 2005 was quite similar, although by the time it actually arrived the uppers had got watered down quite a bit. I lived and worked in Central London at the time and got zilch, although it did deliver for quite a few as I recall. The cold pool looks more robust this time round, so a bigger threat would probably be a geographical deviation with the cold pool either missing us or not quite making it. here.

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Posted
  • Location: Wickham, S Hampshire, UK
  • Location: Wickham, S Hampshire, UK
55 minutes ago, Retron said:

While you rummage around, here's the ensemble output just before the cold spell of 2010 started. They're for "London", from WZ, which is closer to the Isle of Wight than London IIRC!

FWIW, the mean eventually ended up at -10/-11 for 3 days by the 29th November.

 

ens.png

Are we close to cross-forum agreement ?❄️

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Posted
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.
  • Weather Preferences: Winter synoptics.Hot summers.
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.
9 minutes ago, nsrobins said:

Are we close to cross-forum agreement ?❄️

Good to see you TWO seasoned and level headed posters in here.

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Posted
  • Location: Norton, Stockton-on-Tees
  • Weather Preferences: Snow and cold in winter, warm and sunny in summer
  • Location: Norton, Stockton-on-Tees
4 minutes ago, Stu_London said:

If my recollection is correct, the build up to 2005 was quite similar, although by the time it actually arrived the uppers had got watered down quite a bit. I lived and worked in Central London at the time and got zilch, although it did deliver for quite a few as I recall. The cold pool looks more robust this time round, so a bigger threat would probably be a geographical deviation with the cold pool either missing us or not quite making it. here.

Yeah I remember 2005 well, I was so excited for the spell, told all my relatives and friends what was coming and how biblical it was going to be and the closer it got the less the impact was forecast to be. I also remember on the 27th (I think) that the dewpoints were too high and the snow had turned to wet drizzle and I remember being gutted!

 

That is one of the many reasons why I will not get excited about this until it's right on the doorstep, and I am certainly not telling anyone to stock up on essentials as I've been burned by that far too many times before! That said, even if it a watered down version of what's being modelled it'll still be a notable event.

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
1 hour ago, Catacol said:

Agreed. This is still a risk. I'm slightly concerned the models may not yet be seeing the full impact of the SSW... and if anything that storm track might drop further south. The wailing and gnashing of teeth that would follow if Paris was buried and it was sunny in Portsmouth would be hard to bear!

That's interesting, and certainly one of the two biggest risks, but I think it may be the lesser one.  My gut feeling is that the second warming in the strat will only strengthen the block and the bigger risk is that the block will maybe drift too far north, GFS 0z run exemplifying this evolution?  

Having said that, there's very little in the output today to suggest that either of these risks are significant, quite the contrary, it's just that there are some days to go and things can always change.  At least I think the risk of the Atlantic breaking through is negligible.

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Posted
  • Location: Hernia Bay
  • Weather Preferences: Heavy Snow
  • Location: Hernia Bay
1 hour ago, supernova said:

By a considerable margin the best set of ENS I ever remember seeing for the Eastern counties. Am gonna see if I can unearth the ensembles for 2009/10 when I get time later - be interested to compare - but honestly I'm not sure they were ever this good.

graphe3_1000_296_42___.thumb.gif.ae7b47b1277fb73fc8459f48a9753a8c.gif

Could u please provide ME with a link to Kent ensembles thanks 

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Posted
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.
  • Weather Preferences: Winter synoptics.Hot summers.
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.

Lets play Spot the difference  at 240z while we await the 12zs

EDM1-240.GIF?18-12

gens-21-1-240.png

Truly amazing agreement which is usually laughable, except this time highly likely

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Posted
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.
  • Weather Preferences: Winter synoptics.Hot summers.
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.

Edit link provided already

Edited by winterof79
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Posted
  • Location: Blackburn - 180m asl
  • Location: Blackburn - 180m asl
1 minute ago, winterof79 said:

Lets play Spot the difference  at 240z while we await the 12zs

EDM1-240.GIF?18-12

gens-21-1-240.png

Truly amazing agreement which is usually laughable, except this time highly likely

Incredible agreement. Getting more and more confident about this now.

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Posted
  • Location: Blackburn - 180m asl
  • Location: Blackburn - 180m asl
1 minute ago, bluearmy said:

a week away from the deep cold onset and plenty of shortwaves to run under the bridge in the meantime. The cold pool just leaving Siberia. A warming currently under way in n America which could change the modelling again. 

Should that American warming really have much bearing on the European cold which is already in motion? As for shortwaves few have been modelled and some of them have been beneficial.

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Posted
  • Location: Bristol
  • Weather Preferences: Thunderstorms and Snowstorms
  • Location: Bristol
16 minutes ago, Penicuikblizzard said:

Still plenty time for a spanner in the works to appear,,this event is still a week away a long time in terms of weather 

This is where I disagree, for the deep cold we are most certainly looking a week away.

But for the general pattern we are looking at 72-96 hours at most; we are very close to nailing this upcoming spell. (Although the GFS seems to bring the cold in 12 hours earlier compared to the ECM)

GFS.png ECMWF.gif

Edited by Ben Sainsbury
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Posted
  • Location: Purley, Surrey - 246 Ft ASL
  • Weather Preferences: January 1987 / July 2006
  • Location: Purley, Surrey - 246 Ft ASL

Awaiting the 12z with interest. 

My word of warning is little downgrades in the medium term (72 to 120hrs). We have seen this a number of times this season already. -10c 850s at 120hrs and by the time we get to 48hrs we are looking at -6c and snizzle.

This set up looks a million times better than anything for the last 4-5 years, but it could become 'average' if these little downgrades creep in. 

 

 

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Posted
  • Location: Rotherhithe, 5.8M ASL
  • Location: Rotherhithe, 5.8M ASL

We’ll be looking at explosive snow convection no doubt if deep cold arrives I’d say this has a very likely chance of it happening has strong support from EPS and GEFS.

SSTs are above average mmmm - particularly offshore south east! The deep cold will offset the ‘moderation’ I don’t see marginality even on the coast some really deep snow possible in the east. What with the strengthening sun, showers will pop up anywhere even far away from the east coast these will likely be heavy in a very cold, low heights continental airmass.

A4961E08-7D2A-4D5A-AACE-0EC07C69B0D7.thumb.gif.39a5397068953c5e26bfc336c52b93dc.gif

Edited by Daniel*
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Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire

Im expecting the number/member levels to surpass +300 for the 12z this arvo!!

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