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Model Output Discussion - cold spell to end Autumn

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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The number of eps clusters early on tells us that it’s pretty pointless second  guessing this 

on the extended, the clusters reveal a binary evolution between a fairly zonal solution and more amplified with the more amplified cluster ending up with a distinct  ridge to our north and euro trough maintained (as much as one can see on the Icelandic output)

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Ensembles have the first slider hitting pretty much anywhere in the British Isles, no pattern at all yet defined. One even misses the south completely while the rest have snowfests to marginal further south, west, east and north!

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gens-0-1-108.pnggfs-0-108.png?6

Just to show the minute variance which makes all the difference, the low on the 6z control is about 5mb deeper, which helps to pull it a little further north and merge somewhat with the low to the north - net result is pretty good continuity with the median position of the potential snowfall from the 0z EPS (Wales, Midlands primarily, most of it to the north of the M4)

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22 minutes ago, Nick F said:

To give some credibility to the 06z more southerly track for Sunday's low, the 00z GEFS stamps had a fair few southerly tracks for the low too

gefs_stamps.thumb.png.effe9680635786518aee2e6b4bdcc48c.png

Be interesting to see what the 06z GEFS stamps show too, though as others have said, the high res runs should be a better guide than the ens mean or clusters at only 5 days out. Though there are six EPS clusters as early as 00z Monday:

ec-ens_nat_z500scenarios_2017120600_120.thumb.png.604a78d18bda91441fab3c21f393940b.png

 

And look at just how evenly spread the ECM clusters are - only 10 in the biggest cluster, 6 in the smallest. All with different interactions between the lows to the NW and SW!

This slider is absolutely not call-able yet.

One thing in my mind though - troughs to the NE are often correcting a little further NE nearer T0 - such a trend might favour the SW route?

Regarding longer term, there continues to be excellent continuity for 15-16 December with two-thirds of clusters a renewed Atlantic ridge by the 16th:

ec-ens_nat_z500scenarios_2017120600_240.

however, as BA alluded to, the less blocked solution becoming more evident between D12 and D15, up from 30% yesterday to 50% this morning. Still a very large cluster with a ridge to the north and potentially east ( @ShortWaveHell yes, this latter theme has been the most evident one in the past few ensemble runs, and interesting to hear Glossea going this way too)

ec-ens_nat_z500scenarios_2017120600_288.  ec-ens_nat_z500scenarios_2017120600_360.

 

Edited by Man With Beard

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The same posters on here always trying to see what they want to and hopecast. 

I have to chuckle when I see so much attention on one LP system, of course it's path is going to be modelled differently from run to run and I understand why so many people are interested, but the path is more or less clear..this will move pretty much straight across the UK from NE to SE cutting a thin sausage shaped wedge, Snow more likely from Wales in the West drawing a line to Lincoln in the East and anywhere North of that is in the firing line. 

 

Those like me in the South really aren't going to get much out of this from Sunday onwards...those in the South and South West...your best chances of seeing snow is prior to Sunday, with Friday being your best opportunity and this has been consistently modelled for some time now. 

 

prectypeuktopo.png

 

If you like cold zonality and lots of rain then you're in for a treat next week, I really can't see how anyone see's it any differently ?

 

prectypeuktopo.png

As it usual from cold Zonality, N.Ireland, Scotland or NW England coastal areas are where you want to be. 

If you want a UK wide snow event then you need an Easterly or a North Easterly and until that happens the majority of us on here are going to be in for a let down...personally I can't stand nothing worse than cold, strong winds and rain...and that's what most of us are going to see from this set up AFTER the weekend. 

 

So enjoy what is to come from Thursday through until Monday IMO, but by all means feel fee to see what you want to and ignore what is actually being modelled

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Sod’s law the slider low will go too SW and miss England altogether & skirt the extreme south coast instead hitting Northern France and the Channel Islands. I’d say that is highly unlikely not too surprised by southerly track by GFS 06z seen it time and again, would be good to see some consistency in the 12z.

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4 minutes ago, EML Network said:

The same posters on here always trying to see what they want to and hopecast. 

I have to chuckle when I see so much attention on one LP system, of course it's path is going to be modelled differently from run to run and I understand why so many people are interested, but the path is more or less clear..this will move pretty much straight across the UK from NE to SE cutting a thin sausage shaped wedge, Snow more likely from Wales in the West drawing a line to Lincoln in the East and anywhere North of that is in the firing line. 

 

Those like me in the South really aren't going to get much out of this from Sunday onwards...those in the South and South West...your best chances of seeing snow is prior to Sunday, with Friday being your best opportunity and this has been consistently modelled for some time now. 

 

prectypeuktopo.png

 

If you like cold zonality and lots of rain then you're in for a treat next week, I really can't see how anyone see's it any differently ?

 

prectypeuktopo.png

As it usual from cold Zonality, N.Ireland, Scotland or NW England coastal areas are where you want to be. 

If you want a UK wide snow event then you need an Easterly or a North Easterly and until that happens the majority of us on here are going to be in for a let down...personally I can't stand nothing worse than cold, strong winds and rain...and that's what most of us are going to see from this set up AFTER the weekend. 

 

So enjoy what is to come from Thursday through until Monday IMO, but by all means feel fee to see what you want to and ignore what is actually being modelled

Scrooge McDuck approves of this message.

AEBF037A-FE5B-4EDF-BDE0-4A2A07AC79E1.jpeg

In seriousness, ECM looks much more promising going forward than GFS?

Edited by Johnp

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3 minutes ago, EML Network said:

The same posters on here always trying to see what they want to and hopecast. 

 

I disagree, the last few GFS runs have corrected SW, that's indisputable fact, Nick F (a professional meteorologist) has just stressed uncertainty and that a more southerly track is possible and illustrated it with charts. Don't forget the 6z GFS is the newest data we have, ok - I admit, judging by the met office map, the UKV isn't yet seeing this but the trend is there.

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2 minutes ago, BLAST FROM THE PAST said:

So let’s get this absolutely right. The set up is so marginal.....it’s marginal?  Ok got that :)

 

BFTP

While the uppers are far from remarkable it can be perfectly good even for snow to settle to low levels, also bear in mind when rain falling evaporates this cools the air lowering the snow level. 

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58 minutes ago, Ed Stone said:

Looks like a whole week characterised by 'marginality' - which, lo-and-behold, is an actual word...So why 'zonailty' isn't is a bit of a mystery: 

 

h850t850eu.png

If you keep posting T240 charts to support your take on it, for this winter ill be happy :)

Edited by stewfox

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1 minute ago, Daniel* said:

While the uppers are far from remarkable it can be perfectly good even for snow to settle to low levels, also bear in mind when rain falling evaporates this cools the air lowering the snow level. 

Tbh I think blast was being sarcastic Daniel. Tbh his point is valid:rofl:

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19 minutes ago, ShortWaveHell said:

Hmmm *interesting* update that the ECMWF and Glosea are both getting signals of pressure rising to our N N/E in the week commencing 18th , think the last two ecm runs have leaned to this 

It would be useful to quote your source for this, ie Ian Fergusson, as per the Model Tweets thread. 

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@EML Network If you watch the latest BBC Weather For The Week you will see that next week appears to be more "interesting" than you think, so keep watching those models!

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The majority of GEFS members showing heights building to the north and east at day 12-15

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17 minutes ago, EML Network said:

The same posters on here always trying to see what they want to and hopecast. 

I have to chuckle when I see so much attention on one LP system, of course it's path is going to be modelled differently from run to run and I understand why so many people are interested, but the path is more or less clear..this will move pretty much straight across the UK from NE to SE cutting a thin sausage shaped wedge, Snow more likely from Wales in the West drawing a line to Lincoln in the East and anywhere North of that is in the firing line. 

 

Those like me in the South really aren't going to get much out of this from Sunday onwards...those in the South and South West...your best chances of seeing snow is prior to Sunday, with Friday being your best opportunity and this has been consistently modelled for some time now. 

 

prectypeuktopo.png

 

If you like cold zonality and lots of rain then you're in for a treat next week, I really can't see how anyone see's it any differently ?

 

prectypeuktopo.png

As it usual from cold Zonality, N.Ireland, Scotland or NW England coastal areas are where you want to be. 

If you want a UK wide snow event then you need an Easterly or a North Easterly and until that happens the majority of us on here are going to be in for a let down...personally I can't stand nothing worse than cold, strong winds and rain...and that's what most of us are going to see from this set up AFTER the weekend. 

 

So enjoy what is to come from Thursday through until Monday IMO, but by all means feel fee to see what you want to and ignore what is actually being modelled

Such certainty!

The met office would give their eye teeth for it.

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28F82FA7-2253-4964-81B4-072C5DE2965E.thumb.gif.e85eb8523379618701693315efc11016.gif

its been a while since we’ve seen that much scatter towards the end of the run. Certainly more support for the warmer members than 12 hours ago when I posted yesterday’s 12z graph. One to watch.

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3 minutes ago, swfc said:

Tbh I think blast was being sarcastic Daniel. Tbh his point is valid:rofl:

I see, well I didn’t!

 I don’t see anything overly marginal on GFS 06z I must be honest I haven’t looked at the T850 temps but sure they will suffice. Ahead of the slider we see a waft of the continent this will ensure dew points are all good. The slider low fills out making it very conducive for evaporative cooling, it’s a near perfect track for Southern England. 

2DC17A8B-DDC0-46A1-AFEE-E97BCB416B26.thumb.jpeg.bd37f287ba84559bcda67285f966b30b.jpegE00FFB97-EA5C-49D3-AD8A-28C7219F76B7.thumb.jpeg.9806aea9799d9c6b3be87e1c92b7cd6d.jpeg

 

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11 minutes ago, stewfox said:

If you keep posting T240 charts to support your take on it, for this winter ill be happy :)

In fairness Stew, I could've posted almost any chart that has any 'cold' on it; it just so happens that that was the one I was viewing, at the time...?:santa-emoji:

PS: Friday and Saturday are of course the exception.:D

Edited by Ed Stone

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All this talk about the track being nailed yesterday / today. Not a hope, was never a hope and what's more, it isn't over yet.

Zero surprise whatsoever to see the SW shift, es expected, it always does, Steve explains the reasoning earlier on very well. Be aware though, as improbable as this sounds, this could actually end up missing the UK altogether. I give that a hefty 30% chance which may seem crazy at this seemingly late stage. Should it, take the goods news, we are in all nice inside the cold air and locked in for a while.

The models are starting to throw a few little hints about a spell of SW-NE jet activity in FI. Not to be ruled and quite plausible, one to watch and even if so I expect it to be transitory. That said, how about this instead... !! :shok:GFSP18EU06_384_1.thumb.png.428010e3af02f1d9edd9790fe4eead54.png

Edited by s4lancia

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Afternoon all :)

Whatever happens in the near future - I'm starting to look at beyond the beyond and as others have noticed and noted, the increasing trend for height rises to the NE. The 06Z OP doesn't really get there but plenty of the members in the ENS do.

The truth is the route to very cold often starts from very mild and the transition from an Azores HP dominated airflow from the SW to a Scandinavian HP dominated flow from the east or south east can mean a period of mild or very mild conditions before the colder continental air sets up and moves in.

Some of the most notable cold spells have started with the Azores HP moving NE across the British Isles to Scandinavia but they are as rare as hen's teeth and a more likely evolution is or are the two HP system squeezing out any residual trough over the British Isles and creating a single large HP cell which migrates NE and opens the door to the cold ESE flow.

We are seeing both the Azores HP re-orient towards western Europe (a positive tilt) and heights building to the far NE but it may take a few days for anything to come into the reliable range and possibly not even until the New Year.

Even if and when that happens, while it will guarantee cold, it won't guarantee snow and we will need to see lower pressure to the SW and the classic battle ground scenarios from which large snowfalls can occur.

I now expect it to go mild in the week before Christmas and probably through Christmas with a return to colder weather around the New Year.

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