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Paul

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

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!

Message added by Paul

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GFS - very good 

UKMO - ok, bit delayed

GEM - Excellent

ICON - Superb

 

Need movement from the ECM this evening then confidence will be on the up.

Edited by The Eagle

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20 minutes ago, swebby said:

 

If in doubt, i'd have thought that sticking with the inherent/perceived bias of any particular model is the best option?  At the end of the day, they start with a data set @t=0 and run with it, so if there is a bias to the algorithms they'll be there in a westerly or easterly regime?  I'd assume that the only novel issue in these circumstances would be the remote possibility of an individual run being unable to coherently process the starting data set?  That said - @pages below may have a point that the TPV modelling may be struggling from the very start?

 

 

Perhaps. tbh I don't know.... would such bias still occur with a pattern partly in reverse? And does a pattern in reverse respond the same way to pacific forcing and angular momentum budgets? All new territory for my poor brain... but without doubt it is turning cold: that we can agree on.

I agree with the modelling of the Canadian vortex and have felt for a while that the cold might make it in earlier than initially forecast. It's the attitude of the block and angle of the undercut that I'm struggling to make a human interpretation on.

Bit strapped for time at work - will try and put together something a little more coherent later.

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A week tomorrow! I know these should be taken with a pinch of salt! but just shows what can happen and it may even happen with the current set up! 

snow.jpg

snow1.jpg

snow2.jpg

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6 minutes ago, radiohead said:

GFS hi-res ends with probably the biggest snow event/blizzard for Ireland in a generation. Purely fantasy island stuff of course.

240-779UK.GIF?19-12

Flooding for the UK! 

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6 minutes ago, bluearmy said:

anyway, the gfs shows my fears re @Man With Beard and the Iberian low from earlier today 

Try not to worry too much BA!! The UKMO is far slower again - I know which model I am expecting to back down (and I expect you'll be thinking the same!).

A very subtle clue for other readers - it's not the UKMO ;)

Slower evolution = less chance of snow armageddon at D10, more chance of cold armageddon for the next ten days after D10 - IMO.

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I can't really see such a deep cold pool giving way without interfering with the advance of the frontal boundary to at the very least prolong the duration of frontal snow - during which time more mixing out of the less cold air can occur plus potentially disruption of the LP circulation, and so on.

 

Anyway... in the not as unreliable range, amazing to see GFS, a model that tends to overlook the effect of frost hollows, predicting as low as -7*C in the west without having seen the at least slight snow cover that would quite likely be in place by early Tuesday;

ukmintemp.png uksnowdepth.png

In reality, with a bit of snow on the ground, that could be widely minus double digits with frost hollows below -15*C.

All academic of course, as it depends on a broad disturbance in the flow developing and slackening the wind, the likes of which hasn't been so prominent in other model runs so far. Just thought it was fun to think about (but then again, perhaps frightening if you like your water pipes intact?).

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Even if some area's don't see any snow or not as much as they like it's still going to feel bitterly cold with those temps! even during the day with some still in the minus! 

temp1.jpg

temp2.jpg

temp3.jpg

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4 minutes ago, LeeSnowFan said:

A week tomorrow! I know these should be taken with a pinch of salt! but just shows what can happen and it may even happen with the current set up! 

snow.jpg

snow1.jpg

snow2.jpg

Looks like those charts have been drawn by my worst enemy lol, I for one hope these charts don't verify like that. 

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6 minutes ago, Gustywind said:

Yes we don’t want the Greenie/Iceland high merging with the one further East into Asia, as per the GFS, as its cuts off the Easterly cold supply chain into Europe! Cold over us receives no reinforcements  and gradually mixes out.

Need the highs to remain separate as per the ICON.

yep I think the initial easterly is nailed down now and over next days runs will see just how snowy it will be. The next focus is the duration as you mention its how the eastern part of the block interacts which will effect the final outcome. 

at T-102  GFs-gfsnh-0-102.png?12

GEM-gemnh-0-102.png?12

Ikon-iconnh-0-102.png?19-12

all 3 have a Wave over Belarus at t-102 the Gem and GFS bring this North West which then allows low pressure to attack from South West.

Ikon  instead takes it North East which has 2 positives;

1.it stops the Eastern end of blocking joining the high further south- so the cold uppers are not cut off.

2. it means our block is stronger over southern scandie forcing lows further south west and we get a straight easterly rather than south Easterly.

will be interesting to see if any esembles/ECM show same process as Ikon.

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Whilst northern Europe goes into an extended winter parts of southern Europe could become quite warm during next week

  gem-1-240.thumb.png.036c4f043177cd64c9706aec7d740bc1.pnggem-9-240.thumb.png.17b99c964278d860b18add8a91945b8f.png

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23 minutes ago, WalsallWeather123 said:

Channel low at T222 which would bring heavy snow to southern parts of the UK

image.png

Its a shame these chats are not 3 weeks earlier. Almost 1947 like.

 C

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Just now, carinthian said:

Its a shame these chats are not 3 weeks earlier. Almost 1947 like.

 C

In that winter there were a few epic snow events in mid to late February. In fact you will find a lot of significant snowfalls over the years have occured in February or March, rather than in December or January.

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18 minutes ago, bluearmy said:

Getting to the stage where if it might, it will - don’t joke !

You sound pretty nervous Blue?  Are you still of the view this could all go t*ts up or is it more a case that there will always be part of a run somewhere given the UK's location that makes things dicey for us?!

Or more of a direct question.  Are you genuinely concerned about the pattern imploding on us or are you just highlighting some minor niggles that may give us only a brilliant cold spell rather than a historic cold spell (for the time of year)?

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Think @bluearmy is just being real here ! And as a clearly experienced poster has seen things go awry and seen ones verify ! Been bitten before perhaps , let’s hope he’s bitten again , by frostbite this time 😉 

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216-290UK.GIF?19-12 222-290UK.GIF?19-12

As much as I am suspicious of the way GFS handles the Iberian LP development, those are wind chill maps worth saving if you like that sort of thing.

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9 hours ago, carinthian said:

Morning all, certainly the GFS is the best  run for a quicker route to much colder weather. Both ECM and UKMO have milder uppers (850mb level) over Western Europe and The British Isles by this coming Sunday with the very cold advection sinking ever so slowly SW. Anyway we have been issued with  severe cold warning for Sunday morning, temp -22c.  Maybe the human input on forecast charts may become more prominent this week as we continue to see up grade and downgades on the intensity of cold or not. However, I do not like the switch from negative uppers shown widely this Saturday to positive on Sunday ( RE UKMO/ECM ) hopefully a correction to follow.

C

UW144-7.gif

Evening, think a bit of a up grade from latest UKMO run .Has colder air advection through the lower layers into SE Britain by next Sunday. GFS continues on its merry way towards a noticeable cold wave into much of the British Isles by this time next week with snow risk increasing.

C

UW144-7.gif

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2 minutes ago, Steve Murr said:

GEFS mean @ 72 & 96-

If we are here tomorrow @48 & 72 with identical charts then were all but home & dry...

Still another 24-36 hours of nerves - so maybe wait for the weds 00z ( 36 & 60 charts ) to confirm - we can then raise the excitement levels by saying when not IF...

4BC37462-4C7D-4144-99E0-DFA63C966B27.thumb.png.cff611fb914b729a0d1114265b789c56.png095CD95A-36E9-4223-B40B-163039A45A5C.thumb.png.297d46025e79f9b78868c6e9c99ce842.png

S

When not if for the Easterly, or when not if for the deep cold (sub -12s & lower)? Assume the former?

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8 minutes ago, carinthian said:

Its a shame these chats are not 3 weeks earlier. Almost 1947 like.

 C

What did your post from earlier say please Carinthian. I guess it was a forecast in your part of the world ?

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28 minutes ago, K9 said:

How far west realistically can we expect to see the 'cold pool' of low 850's go with the current outputs?..I know this 'potential' cold spell is still a fair few days away and things are constantly subject to change, just fancied picking your brains and hearing your thoughts ?

I am no expert but we have already seen some runs get the -13 / -14 air over to the West coast of Ireland.

There is no reason why us here in Yorkshire couldn't see a bit of -16 action under the perfect alignment of the coldest air.

I won't be greedy though I will be happy with what most of the runs from this afternoon show at around -13!  :drunk-emoji:

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GFS has unprecedented in ‘christmas pudding’ 500 dam air reaches east Kent, there’s been several incidences of this in 20th century but nothing so far in the 21st century. Absoloutely monsterous and historic.

567E24E5-52C1-4E8A-9412-3A8EB2E30FD1.thumb.png.ef59106aacd6dbd3205a3230832295e2.png

Edited by Daniel*

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2 minutes ago, Gustywind said:

When not if for the Easterly, or when not if for the deep cold (sub -12s & lower)? Assume the former?

The easterly is coming - its to confirm the upper air cold pool is following ( those timelines )

The movement in our direction of upper air cold pool is at 120-144 so weds overnight will be 84 & 108 - by the confidence above 80% ish - currently 50/60% to the good!

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