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Model output discussion - here comes the beast!

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/

We also have a special post SSW cold spell discussion open here:
https://www.netweather.tv/forum/topic/89358-ssw-related-cold-spell-will-it-wont-it/

Thank you!

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4 minutes ago, ITSY said:

Control - are you kidding me?!  wowza. 

gens-0-1-144.png

Edit: the actual "front" misses the UK in this scenario, but instead it injects lost of moisture over the north sea, funneling very heavy snow showers on a NE/SW track down the central swathe of the UK. Warmer uppers mind you, need to get those deck chairs out with uppers reaching a balmy -9. 

Interestingly the evolution is nearly identical to the12z GEM. That really is a bonkers run everyone! The angle of the low is more realistic though than the op due to it being further SE.

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amazing charts again this afternoon - run out of superlatives! Incredible cross model support now for something quite special early next week and who knows where it might go from there.

Hopefully this will lay to rest once and for all the old claim that "it can't get cold in late February" due to solar energy / longer days etc (given that March 2013 seemingly didn't put the claim to rest!)

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The Gem 12z looks a bit nippy next week..!:shok::D:cold-emoji:

GEMOPEU12_96_2.png

GEMOPEU12_120_2.png

123_uk2mtmp.png

GEMOPEU12_144_2.png

147_uk2mtmp.png

GEMOPEU12_168_2.png

171_uk2mtmp.png

GEMOPEU12_192_2.png

186_uk2mtmp.png

195_uk2mtmp.png

GEMOPEU12_216_2.png

210_uk2mtmp.png

219_uk2mtmp.png

GEMOPEU12_240_2.png

240_uk2mtmp.png

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1 minute ago, ITSY said:

I'd take a wobbly flow with the amount of features it has running across the country!! 

Same here. Looks really snowy!

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5 minutes ago, ITSY said:

Control - are you kidding me?!  wowza. 

gens-0-1-144.png

Edit: the actual "front" misses the UK in this scenario, but instead it injects lost of moisture over the north sea, funneling very heavy snow showers on a NE/SW track down the central swathe of the UK. Warmer uppers mind you, need to get those deck chairs out with uppers reaching a balmy -9. 

Edit again: so disruptive in fact that it merges with a feature in the Atlantic. I'd be buried! Can't keep up with the potential!!! 
gens-0-1-174.png

Yes, someone else mentioned this earlier....a win/win scenario if this sort of chart verifies....some snow close to the south coast to keep those poor snow starved souls happy, and the increased moisture advected from this system could set off snow machine streamers for some...happy days!

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Be wary of any output showing a fast breakdown of cold air, historically we've seen models breaking down cold spells too easily, the GFS especially appears to have a real bias for doing this.

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21 minutes ago, WalsallWeather123 said:

ARPEGE preciptiation charts vs HI RES ARPEGE precipitation chart at T120. Hi ris shows snow is more scattered and not widespread as the first chart shows.

image.png

image.png

You are comparing a chart for six hours with one for one hour, it's only logical that the six hour one shows six times as much.

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10 hours ago, MattStoke said:

Not with the low dew points. They will be through the floor. Some sublimation is possible though (snow evaporating without melting).

Thanks for this Matt, I have been following the models for years but have never come across this term 'sublimation' (when has it ever been applicable to uk cold?  just highlights the significance of the upcoming spell) 

The reason it caught my attention was because of the olympics, seeing snow falling on the TV and all the tracks/courses layed out with snow, yet the surrounding countryside is bare, with no snow cover. 

I did perhaps think this was due to the severe dry cold air they experience but now I know it's down to sublimation.

always learning :) 

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Just now, Weathizard said:

Be wary of any output showing a fast breakdown of cold air, historically we've seen models breaking down cold spells too easily, the GFS especially appears to have a real bias for doing this.

I agree, but milder uppers sneaking into the SE late next weak isn't really a breakdown in the traditional sense as really its just a slight nudging of the easterly pattern north. Clearly not too much can be read into it yet as too far away for such fine detail but I think its valid to consider it an option.

In fairness if this goes the way it looks I'd still be happy even if IMBY it does rain later in the week. Its hard enough to sustain that depth of cold in mid winter let alone early spring. 

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1 minute ago, Glacier Point said:

Worth noting that the 00z, 06z and now 12z GEFS is building back +ve height anomalies to our north and north-west beyond day 10. Indicative of the second tropospheric response to the stratospheric warming.

If there is any breakdown, it won't be a long one.

Are you talking about the mental state of nw members or the pattern? :D

I find snow melting a traumatic experience , hate to see it go after it’s been around !

Perhaps the models will speed up the warming response in which case that would rule out a breakdown .

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9 minutes ago, ukpaul said:

You are comparing a chart for six hours with one for one hour, it's only logical that the six hour one shows six times as much.

You know what, in the 8 years of model watching, I didn't actually realise that's what it meant. I just thought it was a six hour time stamp. 

Related image

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2 minutes ago, Glacier Point said:

Worth noting that the 00z, 06z and now 12z GEFS is building back +ve height anomalies to our north and north-west beyond day 10. Indicative of the second tropospheric response to the stratospheric warming.

If there is any breakdown, it won't be a long one.

Next hit could be from a Northerly? If it builds to NW. If you were a betting man which do you think is more plausible a Northerly or Easterly? Ty

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7 minutes ago, Summer Sun said:

GFS 12z op later next week can probably be ignored

graphe_ens3_phr1.thumb.gif.8a12e8ad9429b0df30abfdbace36da66.gif

 

This is incredible stuff- there’s still a lot of support for between -10 to -15 uppers all the way out to 6th March. 2 weeks worth. 

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The direction of that trough into week 2 would probably favour a north easterly.

gens-21-1-168.png   gens-21-1-216.png   gens-21-1-264.png

I suspect the general trend will be to keep low pressure south and east of the UK, the strength of the flow and the depth of the cold we could get depends on the heights to our west. At the moment we do see those strong heights fade away, but I suspect we would be able to develop some sort of weak high perhaps towards Iceland to draw that deep cold again from Scandinavia. The one thing on the next wave perhaps is that we probably wouldn't need the depth of cold that we would see this week to deliver heavy snow given heights will be even lower and a NE wind will allow a larger sea fetch.

For the south, always the risk of fronts trying to push into the cold air which would bring snow and strengthening winds as the pressure gradient tightens.

I can't see a quick breakdown from this with the end result likely to look close to the ECM with low pressure struggling to push north into the cold air and will likely elongate.

As for the coming seven days, the first wave of cold (Monday) could reach -14C in terms of 850hpa temperature in the south east, the second pulse following that disturbance on Tuesday looks to be -16C quite widely by Wednesday night. Time to try and firm up on the areas most at risk of disruptive snowfall for the coming week before we see a pattern change later in the week (Not necessarily a change away from very cold conditions of course).

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18 minutes ago, Glacier Point said:

Worth noting that the 00z, 06z and now 12z GEFS is building back +ve height anomalies to our north and north-west beyond day 10. Indicative of the second tropospheric response to the stratospheric warming.

If there is any breakdown, it won't be a long one.

gefs and eps build an excellent NH pattern with the vortex pointing from Siberia towards nw Europe  - and then try desperately to push the p/v back towards Canada. the hope would be that the retrogression of the block gets no further or that we see a surge of the Aleutian ridge across the pole as per this mornings ec op which would help take the vortex towards scandi and e Europe kepping it on the Asian side intact

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GFS 12z is a little out of kilter regarding the push from the south, however for a memorable snowstorm for the southern half of the UK im hoping we can introduce some moisture laden fronts into the cold air, but not to far north :) 

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32 minutes ago, nick sussex said:

I know everyone gets a bit IMBYIST in terms of snow which I can understand because it’s so rare.

But purely  speaking as a neutral as the track of the low to the sw doesn’t make any difference to me here.

In terms of the best outcome if you want to keep the cold you’re bellwether is that low.

The best outcome going forward is the low to flatten more and disrupt energy east . This of course means not everyone will get the frontal snow, but for example if the low was to get too far north this would tell us that the block is too far west and there’s less forcing on it.

I’m sure most here want snow and to see it last on the ground so for that to happen it’s a case of risk versus reward.

Personally if I was still living in Sussex , I’d want the low to trend south even if it meant not being in the game for that frontal snow as I wouldn’t want to risk it.

It depends how lucky you feel! :)

Couldn't of put it better myself Sussex is where my mum was born and grew up beautiful place and usually do well from easterly flow.

Anyway moving on to the models as GP has just suggested any breakdown is likely short lived even into march a northeasterly or Arctic blast would do the trick.

I'd thought Greenland looks likely the area where heights will remain high.

And possibly record breaking cold to come GFS gem and the ECM are already trying to continue to remain cold.

Been a much more interesting winter even more interesting late winter.

Excellent I'm blown away.

Exceptional.

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6 minutes ago, Summer Sun said:

12z ICON snowing snow picking up on Tuesday may be a bit drier Wednesday

output_5BdnRg.gif

I read somewhere that icon down plays precipitation and has a drizzle bias. I don't know if that's true,just repeating what I read. 

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