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


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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3 minutes ago, Weathizard said:

Jesus, historic snow event incoming?

IMG_0302.PNG

Snow to rain and back to snow again unless it goes due east then all snow. If it moves north east it will bring milder uppers to the south of the UK at least before moving away and dragging colder air back south again. Not that it is going to happen any way but the 6z had a similar scenario but a lot shallower so you never know!

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I quite often agree with your sort of sentiment, as I'm one who opts to look at the most likely solution to fit the signals rather than the preferred one But, equally impartially and with intended

Sorry, I just thought I’d walked into the moans threa.. oh wait. <passes around a big bag of grips> No sooner do we get a cold spell within sight it astonishes me that time and time again some p

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1 minute ago, bradythemole said:

GFS going for massive blizzard for the south at Day 9-10

Turning to rain though as it pushes milder air back in. All FI though so will definitely change. Looking great for some proper cold though 

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gfs-0-228.png?12

Just now, Frostbite1980 said:

Snow to rain and back to snow again unless it goes due east then all snow. If it moves north east it will bring milder uppers to the south of the UK at least before moving away and dragging colder air back south again. Not that it is going to happen any way but the 6z had a similar scenario but a lot shallower so you never know!

gfs-1-234.png?12

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1 minute ago, Kentish Snowman said:

The Outer Hebrides are the mildest part of the UK on that chart under a toasty -6 upper air!  :rofl:

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 ?

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2 minutes ago, Deep Snow please said:

Amateur hour question, that's 4cm an hour of snow right? 

No chart available for the selected hour. Many charts start at 3 hours ahead, so if you have 0 hours selected try stepping forward or selecting a later hour.

It will be either per 3 or per 6 hours, depending on the timescale the TWO charts use. If their charts are displayed in 6 hour intervals then it will be per 6 hours...ditto 3

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Just now, Smiler1709 said:

Turning to rain though as it pushes milder air back in. All FI though so will definitely change. Looking great for some proper cold though 

Yes. A LP like that coming up from the south at day 10 is definitely not something to even think about. But fun to see anyway!

another great set of runs so far. Great to see such eye candy charts but still some disagreements to resolve yet.

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2 minutes ago, snowice said:

EC op why?

@Mucka knows why!

seriously, when the models are churning out decent runs, something always goes wrong for us at a weeks range - of course plenty of time to come back on track 

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

we don’t need to blow it all away so quickly 

gem just holds onto the cold but is still a bit  close for comfort and would  likely take a sou’wester before the effects of the next cold pool headed southwest impacted us. Of course the less cold flow getting that far north could well keep the next trough too far north for much of the uk so I will continue to hope the Iberian Low stays precisely in Iberia and extends east, not northeast 

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1 minute ago, bluearmy said:

@Mucka knows why!

seriously, when the models are churning out decent runs, something always goes wrong for us at a weeks range - of course plenty of time to come back on track 

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

we don’t need to blow it all away so quickly 

gem just holds onto the cold but is still a bit  close for comfort and would  likely take a sou’wester before the effects of the next cold pool headed southwest impacted us. Of course the less cold flow getting that far north could well keep the next trough too far north for much of the uk so I will continue to hope the Iberian Low stays precisely in Iberia and extends east, not northeast 

Blue is it the huge temperature gradient that is blowing up that Iberian low? It seems to blow up really quickly and that is the only explanation I can think of as to why?

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2 minutes ago, bluearmy said:

@Mucka knows why!

seriously, when the models are churning out decent runs, something always goes wrong for us at a weeks range - of course plenty of time to come back on track 

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

we don’t need to blow it all away so quickly 

gem just holds onto the cold but is still a bit  close for comfort and would  likely take a sou’wester before the effects of the next cold pool headed southwest impacted us. Of course the less cold flow getting that far north could well keep the next trough too far north for much of the uk so I will continue to hope the Iberian Low stays precisely in Iberia and extends east, not northeast 

I see your point but I think sometime we just have to be a glass half full.:)

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16 minutes ago, bluearmy said:

@Mucka knows why!

seriously, when the models are churning out decent runs, something always goes wrong for us at a weeks range - of course plenty of time to come back on track 

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

we don’t need to blow it all away so quickly 

gem just holds onto the cold but is still a bit  close for comfort and would  likely take a sou’wester before the effects of the next cold pool headed southwest impacted us. Of course the less cold flow getting that far north could well keep the next trough too far north for much of the uk so I will continue to hope the Iberian Low stays precisely in Iberia and extends east, not northeast 

But at the same time, if it blows up a little less than the GFS is showing, it could be absolutely epic for parts of the south

Edited by s4lancia
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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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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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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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