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Model output discussion - winter proper underway

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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After we get that low out of the way on Thursday it is back to settled and cold again. Heights then try to go to Scandi but the Atlantic is picking up strength at the wrong time. Interesting viewing though looks like a battle setting up.

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5 minutes ago, nick sussex said:

Interesting !

The GFS 12 hrs run  is holding the low further south to the east over Eastern Europe which allows the toppling ridge to the west some support.

You want low heights to remain there and not get pulled north as in the earlier 06 hrs run.

Hinting at a Scandi high? How long ago was the last one? 

Edited by ArHu3
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2 minutes ago, snowice said:

It's amazing that the other models are dished out when on the hunt for snow?

The poor mods have waved the white flag!I suppose you can't blame members after the last mild wet winters.I think there could be some interest next weekend again something we need to watch.:)

Always going to happen but looking at the position of the low that crosses the UK on the UKMO and GFS midlands still favourable place. NMM earlier was almost a carbon copy of what the graphics on the Met office forecast showed so that will be of interest as will the Euro 4. 

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Cold building over the very near continent at 210, some very cold nighttime minima I would have thought with low uppers and such slack winds

gfsnh-1-210.png?12 gfsnh-0-210.png?12

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4 minutes ago, snowice said:

It's amazing that the other models are dished out when on the hunt for snow?

The poor mods have waved the white flag!I suppose you can't blame members after the last mild wet winters.I think there could be some interest next weekend again something we need to watch.:)

To be fair, the lesser known models are dished out when thunderstorms are forecast as well. Think people find them pointless when looking at Atlantic storms etc as the synopsis is far broader. :) 

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3 minutes ago, ArHu3 said:

Hinting at a Scandi high? How long ago was the last one? 

12/13 not sure but there as common as hens teeth nowadays but one thing the NAO is set to go  possitive once again from mid december  from all models that is never good news 

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18 minutes ago, Snowy L said:

After we get that low out of the way on Thursday it is back to settled and cold again. Heights then try to go to Scandi but the Atlantic is picking up strength at the wrong time. Interesting viewing though looks like a battle setting up.

And my gut feeling is that most will remain well below average in the run up with the milder spell forecast for mid-week, downgraded over the next couple of days. Get the next two day's weather out of the way and we'll know more. I think the lying snow area could expand more widely than currently forecast and with that comes severe frosts over snowfields and temperatures struggling to get to currently modelled values. Quite a lot of my own conjecture but we can certainly learn from past events and their aftermath and cold air CAN be hard to shift. :friends:

Edited by gottolovethisweather
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1 minute ago, Singularity said:

Been too busy with non-weather things to keep track of the models today (shock horror!) but as interesting as the slider low adjustments are and that potential storm on Monday for that matter, what has caught my eye most today has been the huge discrepency between the model projections of two days ago that I saved for verification purposes and the actual observed MJO; I have overlaid below with the old runs as those fainter blue lines. No need to worry which model is which as they've all had a total 'mare :rofl:.

Seriously though, this means a lot more forcing toward amplification and HLB to our N and NE than the models have been working with lately. Might take a day for the corrected signals to work through fully but GFS looks to already be smelling the first fumes from the coffee.

There could even be increased sharpness to the ridge-trough pattern Thu-Fri this coming week but that might be too close in range given the typical lag time for tropical forcing to propagate across to the Atlantic sector.

MJO-ModelFail-7th9thDec17.PNG

Yes it does look like GFS has picked up on something, lows taking a very long time to get to that area of sea above the UK. Pretty much stalled from the 16th to the 19th on this run so far.

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1 minute ago, gottolovethisweather said:

And my gut feeling is that most will remain well below average in the run up with the milder spell downgraded over the next couple of days. Get the next two day's weather out of the way and we'll know more. I think the lying snow area could expand more widely than currently forecast and with that comes severe frosts over snowfields and temperatures struggling to get to currently modelled values. Quite a lot of conjecture but we can certainly learn from past events and their aftermath. :friends:

There isnt really a milder spell. Wednesday morning is the only time warmer uppers get mixed in but even then most central alreas will have lying snow keeping surface temps  down. Thursday onwards its below average again.

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Into FI and again the GFS is wanting to raise heights around scandi. Best model viewing in several years at the moment.....just feels different this year (as I'm sure those members in the Midlands will be testifying this time tomorrow)

gfsnh-0-252.png?12

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7 minutes ago, Ice Day said:

Into FI and again the GFS is wanting to raise heights around scandi. Best model viewing in several years at the moment.....just feels different this year (as I'm sure those members in the Midlands will be testifying this time tomorrow)

gfsnh-0-252.png?12

Tropospheric pattern is backed up by both low and higher stratosphere though. Both showing the bigges lobe of the vortex going to the other side of the North Pole from days 7-10. Did someone mention the strat and trop are very well coupled at the moment?

Edited by Snowy L

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As others have mentioned, interesting GFS 12z... again the setup for the Friday northerly is key
image.thumb.png.dfabe041b1c38fd4ca197071888af3da.png

I've highlighted the things to look out for, again the more amplification the better chance of a good Scandi high later. It wouldn't surprise me if it did improve a bit more :)

image.thumb.png.bad249b7fdd680a0b6e694d0bfb5ade6.png image.thumb.png.5be623c9be5fd137bfcda9b5a1be979e.png  

In the 12z GFS the Atlantic charge is held back. The synoptics don't look flattering but given the slack pattern it would actually be very cold at the surface. The long nights and weak solar input means stagnant patterns become increasingly colder if they persist.

A very messy synoptic picture at the end of Friday's northerly, a surprise undercut may appear? :rofl: Probably not but there is a good opportunity to extend this cold and it would be great to see some small improvements to that higher SLP in the North Atlantic and get some good heights to our NE.

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http://www.meteociel.fr/modeles/arome.php?ech=3&mode=142&map=0

Okay so I've finally had a look. Interesting indeed with snow-rain-snow events on offer for locations as far south as me overnight Sun-Mon and all snow for places just a little N of me (say, 20+ miles inland from the coast?). The brief transition to rain occurs where the 'warm' sector of the LP just edges inland a touch in a shallow wedge formation. That region does see heavier precipitation as a trade-off but it only takes a bit of rain to mush some nice lying snow into a nasty slushy later that then freezes into ice when further snow starts falling. This region, i.e. CS England less than 20 miles from the coast, is within a minute (by modelling standards) S shift of an all-snow event, but equally so of an all-rain event. Talk about nerve-wracking! This is why I was actually more relaxed when the snow prospects were minimal this far south :laugh:.

AROME, linked above, actually brings the snow south by Sunday afternoon in a sweeping motion that's seriously mesmerising. Seems this wrap-around of cold has increased with each new run today as the elongation of the overall trough structure to the west has been diminished to the point of insignificance.

WRF-NMM 2km 12z is not so 'sweeping' in its ways but does have an interesting boundary line setting up that transitions to snow by Sunday evening as the cold air cuts in;

nmm_uk1-42-28-0.png?09-17

I can already see the forum posts complaining about the wet ground making it take so long for the snow to start accumulating :reindeer-emoji:.

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7 minutes ago, Catacol said:

Yep - going to agree strongly here as I have been following the same. Models are wanting to reduce AAM and move back towards the COD but the reality continues to be different. Amplification will be the result - and while this always introduces the chance of mild shots we do seem to be setting up on the cold side of the jet. Crucial that the continent cools... and I'm starting to get a funny fuzzy feeling about a properly cold spell on the horizon. If/when an easterly materialises I hope we can avoid it being dry and cold - that is always a risk with a scandy high setup and we need decent troughing to south and west to provide more in the way of frontal snow on top of the east coast streamers - but let's get the cold in first before worrying about anything else.

For those in the North, Midlands and parts of Ireland I expect they couldnt give a rat's ar*e about medium and long term signals because winter has arrived for most parts away from southern counties... but it would be good if everyone could get in on the act and these rinse and repeat northerlies are often marginal for many parts... tomorrow being an example. Give me a solid continental feed followed by an atlantic attack any day. 

Starting to look like even far-southerners may be a bit distracted from the longer-term by tomorrow evening :snowman-emoji:.

The cold pooling on the 12z GFS is considerable not far east of here. Were it not for the westerly bias of lower-res, I think we'd have had some fun charts to look at there. 

I suppose we actually did for Xmas Day (despite a less than ideal sliding low track) but it could easily have been quite a bit sooner.

GFS takes quite a while to switch over to Aleutian ridging. I can see how a bit of toning down of the Pacific westerlies could bring it about a good few days sooner.

gfsnh-10-384.png?12

The Aleutian Low/Siberian High combo does plenty of work on the stratosphere beforehand, though - so it may be best if that's not cut off too soon after all?

Judging by IF's tweets in the model tweets thread, the Met Office are already adjusting their timing accordingly (via GloSea5 behaving itself); the longevity of the more zonal signal is being played down more today than was the case yesterday.

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Quite a difference at such a short time frame between all the hi-res models of the location of precipitation and the cold front for tonight and tomorrow. Shows how unusual the set up is! 50 miles shifts can make huge differences on the ground for the cold and snow lovers!

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Looking through the GFS ens and there is definitely increasing signs of a more anticyclonic outlook with Scandi high potential in around 10 days time.

There's a few awful members but the control is also bullish on a Scandi high again. This cold spell could last for quite a while and its starting to get close to Christmas....

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