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Paul

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!

Message added by Paul

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39 minutes ago, stainesbloke said:

Well, thankfully you’re here to tell us all how the weather will pan out in 6 days time, during a record breaking double SSW and with an extreme cold pool of air affecting the UK. I’m envious, to my feeble mind anyone ‘calling it’ at this stage is clearly Einstein reborn and must be fast tracked to the Met Office with immediate effect. I’ve never seen models reverse or drastically change, after agreeing for 20 minutes. Oh, hang on.....

Bit harsh in your assessment of what is a very sensible post and a very viable outcome. The models whether some like it or not are at the minute and have been for the last few days been showing less cold / milder conditions approach from fri / sat onwards. The models and yes even the UKMO introduce these conditions to particularly southern England. These are backed by the ensembles. Anyone thinking otherwise must have blinkers on if they can’t see the trend across the different models.

We may have had a record breaking SSW but as the experts have said in the strat thread, it doesn’t always guarantee cold for us. We do get a blast for a few days yes and yes there will be snow. Will it be record breaking - imho no. The issue is the HLB drifts to the west to Greenland and on some runs further towards the eastern seaboard. The block need to set up shop over Scandy as it has done previously in many of the real cold spells that the UK as seen previously were it has on occasions remained for several weeks. 

There will be further tweaks north and south but imo the trend is there and the deep cold lasts no more than a few days.

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To say you can't see how the models could be wrong 5 days out is ridiculous.

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I'll take a PTB1 please 😂 It's bizzare but it's  the best of the bunch

IMG_0391.PNG

IMG_0392.PNG

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10 minutes ago, Reverse Zonality said:

The only thing I can suggest is you check the ensembles on ECM and GFS. There is huge spread after Thursday which is why jumping to conclusions after every op run is a pointless exercise. 

 

the voice of reason . . . 

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I feel like we're giving a little bit too much attention to the 850hPa temperatures for the event on Friday. The colder uppers seem to be easily pushed aside by the low, but with 4-5 days of temperatures struggling to get above freezing and harsh night time frosts the boundary layer is going to be extremely cold.

Whilst the 850hPa temps could possibly become "mild" in comparison to what we will experience this week, the warmer air associated with the low will probably be pushed aloft to an extent with the surface temperature staying around or below freezing. If not snow, counties in the far south would probably see some freezing rain.

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2 minutes ago, Frosty. said:

There's still tons of uncertainty from the end of the week but I think the models are backing away from the milder trend compared to last night and what an incredibly wintry week ahead..I'm so excited!:):D:cold:

Yes Frosty, I agree. Just flicking through the ensembles for next weekend shows the uncertainty, some just bring slightly colder air meaning copious amount of snow nationwide. You can see why some weather forecasters have a serious look in their eye while presenting atm! 

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image.thumb.png.b4d77c60d04be505637a33e46c3e116c.png

More runs backing milder air by the weekend on the 06z. Far from a done deal given the knife edge synoptic situation later in the week but I'd like to see the trend go the other way....

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I think the problem that most people have with Weathizard's assessment is that he's saying it's " game over for the south/far south ", he then presents the main models for day 5 as evidence for this.

Naturally most people want the cold (and snow) to continue, there is also understandably a certain degree of hope-casting, BUT we need to bear a few things in mind:

a) How many times have we seen the models reach a consensus for 5 days hence, only for them to be wrong? Quite a number I'd say, particularly where snow is concerned

b) Bearing in mind the timescale and also the added complications of the SSW this leaves the model output even more open to question than usual

c) The various model outputs overnight/this morning has already seen some corrections for the less cold air not getting as far north as modeled yesterday

d) We're only looking at small changes in the flow and position of the low for the precipitation to fall as snow, even in the far south

e) I don't think that we'll have this nailed down even by Thursday, it could well be a now-casting event

If Weathizard's assessment wasn't so cut and dry (and accepted that there is room for error) then all would be well.

 

Edited by Buzz

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I just can’t see that low moving from directly south to north it will have some easterly movement to it surely sending centre of the low into north France and Belgium that’s how I see it going.

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1 minute ago, Steve Murr said:

Just the first signs that the GEFS not so keen to move the warmth North- More of an attempt North before stalling & moving East - PTB 2 for example...

As highlighted though it will probably go to T24-48 etc

S

I think the NAVGEM has got it right ! :D

 

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06z Short ens for London showing it staying very cold until around Thursday then the control, op and mean all agree on slightly less cold air for the weekend ground temps on the other had will take longer to respond

graphe_ens3_ubs5.thumb.gif.d063a8c46149e55441a55c914dbb3c1a.gif

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Meanwhile back at the ranch.......

Rain/Snowfall EURO4 Tu 27.02.2018 00 GMT

Rain/Snowfall EURO4 Tu 27.02.2018 06 GMT

And that's before the second push of really cold and the tightening of the isobars

tempresultgbm9_mini.png

And yes that is Arpege ,which for the sake of your sanity,is a good bet as it doesn't run into la la land and probably nearer the mark for the METO 

Edited by winterof79

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Full London ens on the 06z a fraction lower than the 00z around the 7th obviously seeing a repeat of the -15's is probably unlikely but still on the chilly side

00z

MT8_London_ens.thumb.png.2ac38b747bf48f3b700d0fc14a9faa9c.png

06z

MT8_London_ens1.thumb.png.8daf8adce7cadd59c9365a8923b903d9.png

Edited by Summer Sun

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Thickness watch:

Ec and gfs : T90/T96. 504 dam crossing Scotland. Small area ne england T90

 

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Morning all :)

No detailed analysis from me as Mrs Stodge has other plans for my Sunday.

Just a few comments on the output I'm seeing this morning:

1) The threat of a west-based negative NAO has always been there - I was talking about it at the beginning of last week. We needed a much stronger HP profile than we are now seeing to firmly the deflect the Atlantic LP more east and south. This is how the 2010 cold spell ended (and in fairness was superbly modelled by GFS which nailed the evolution consistently from T+384 down).

2) Bringitback62-63's excellent summations did take me back to March 2013 when GFS consistently modelled the return of warmer air from the south west for it to fail time and time again. I'm less convinced of the parallels this time but it's worth bearing in mind.

3) Many have agonised in the past week over the exact positioning of the cold pool which varied by 150-200 miles from run to run - now we are agonising over an LP where the scale is similar. As others have said, exact tracks and trajectories won't be clear until Wednesday but the NAVGEM solution would, I suppose, be many people's preference. I wouldn't be surprised to see less cold air cross the country over next weekend.

4) It's unrealistic to expect -12 uppers to be over us for weeks - the coming 72-96 hours will be an exceptional spell for many (and a predictable disappointment for some) but inevitably it couldn't last and even if we had managed a seamless transition to a NE'ly (which never looked likely) there would have been an easing in the frigidity of the air.

5) Once again we are seeing signs of height rises to the east and north-east in far FI - not inconceivable we could have another Scandinavian HP by mid month and certainly one to watch. It's entirely possible while this week's cold may be the most severe, it won't be the last.

One thing is certain - more exciting and tense model watching this coming week as there has been in the past fortnight watching the cold spell evolve.

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29 minutes ago, nick sussex said:

I think the NAVGEM has got it right ! :D

 

Wouldn't it be amusing if a combo of Icon and NAVGEM nailed this cold spell 😁

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