Model output discussion - into the start of Winter

[cheshire snow]

4 minutes ago, Sweatyman said:

There will be surprises. There always is! You see...

Indeed if you take the second half of the week from MO for NW England becoming colder with ice,frost and risk of snow".

C.S

[Daniel*]

15 minutes ago, northwestsnow said:

While a true Cold spell is not indicated on EC a more seasonal outlook is...

There is low temps, well below in some places, and probably some frost etc...

Beats wind and rain off the Atlantic in my world.. 

It is a frosty run. I know a fair bit will change but it forecasts an impressive min of -15.2°C following Monday in Cairngorms area perhaps more useful in highlighting potential for very cold nights.
 

Edited November 29, 2020 by Daniel*

[Mapantz]

Several posts moved.

For general chat about Winter's past & present, head over to here:

https://www.netweather.tv/forum/topic/94744-winter-202021-moans-ramps-chat/

Thanks.

Edited November 29, 2020 by Mapantz

[WxHerts]

Lol, GEM is the dream scenario for next weekend: temperatures very widely down to -5c, shortly accompanied by precipitation bumping up from the south

[swfc]

21 minutes ago, northwestsnow said:

I know, I'm focusing on thereafter Nick !!

Course you are nw

[carinthian]

If the forecast wave develops in the colder airmass out West of Ireland on Thursday into Friday as shown on the latest UKMO fax, the position of the low centre seems to be as shown on the ICON winter overview chart. Certainly a risk of snow , especially on the higher ground of the west and north. Of course these runs change daily but the risk is there.  Could be one to watch in an interesting weeks development to come.

C

[northwestsnow]

8 minutes ago, swfc said:

Course you are nw

I always concentrate on colder weather, I'm a shamless cold zealot ?

[northwestsnow]

ECmean suggests some potentially foggy frosty weather after day 7 as the troughing drops south ....

Pea souper conditions ...

[Mapantz]

3 minutes ago, northwestsnow said:

Pea souper conditions ...

It has been like that for days here, with extremely bad air quality.

On a side-note, snow or no snow, ECM 90 hrs > would bring some interesting weather, in terms of hefty showers with hail, thunder, and Wintriness to some places.

A little more exciting compared to the last few days that have been endured down here.

[ANYWEATHER]

Evening!  Lots of blocking ! It does mean one thing ,colder than average across the UK during this time of year. But , how cold it will get ? Computer models really struggle with this scenario,  but we could be looking at the coldest synoptics since 2010.........

[Cleeve Hill]

3 minutes ago, Mapantz said:

It has been like that for days here, with extremely bad air quality.

On a side-note, snow or no snow, ECM 90 hrs > would bring some interesting weather, in terms of hefty showers with hail, thunder, and Wintriness to some places.

A little more exciting compared to the last few days that have been endured down here.

Country file forecast pretty keen on snow for the Welsh mountains - snowdown and mid wales Black mountains. 
I slight eastward movement and the Clint Hills, Malverns and Cotswolds could see some early winter snow. 

[Mr Frost]

Evening all

NW UK are still in the game for wintry showers to fairly low levels - Wednesday afternoon through to Thursday morning. 
Thursday night through Friday is a mess - rain, sleet, snow, kitchen sink, washing machine could pop up anywhere from Northern Scotland to Southern England! 
This period is still up for grabs with regards to wintry potential - higher ground the better but who knows what could happen!? 

UKV 15z snapshot for Friday 00:00 - quite the difference from this morning when it was all further South! This won’t be resolved for another couple of days. 

 

Just for fun here is the lying snow depth chart (mm) for this run out to 04/12. (15:00)

 

Huge amounts expected over the mountains! 

http://mwis.org.uk//icon/favicon-128.png Home Page

MWIS.ORG.UK

Planning outlook:

A change to sustained cold conditions arrives from the northwest during midweek. Higher mountains becoming persistently frozen, likely into the weekend and beyond. Low pressure will drift slowly southwards across Britain. Widespread areas of precipitation, widely snow on higher terrain - a mix of rain, sleet and snow lower down. Wind likely to vary considerably. May eventually turn toward east or northeasterlies. Chilly conditions are likely to prevail through early December.

Not a bad outlook either! 

It all makes for a lovely seasonal start to Meteorological Winter - snow capped peaks, wintry showers, risk of snowfall and even a bit of soft hail!? 

All the above within the first seven days of December - not too shabby at all. 

All the best.

[stodge]

Evening all

Another day, another set of 12Z output to consider and certainly plenty to comment on yesterday so let's see where we are at the start of a new week and almost at the official beginning of winter:

12Z GEM - yesterday this was very much in the negative alignment with the block to the east forcing successive LP systems SE over or just to the west of the British Isles. On then to tonight and by T+120 the LP has shifted south on cure and become a complex feature with multiple centres over northern and central Britain.  The complex trough fills in situ with the next Atlantic feature - a shallower LP - sliding SE over Ireland. Clear pressure rises to the NE and perhaps a hint of a rise of pressure in mid-Atlantic and the latter becomes a key development by T+240 as the Azores HP ridges North and North East with the LP settling over the continent leaving the British Isles in an E'ly airflow.  Unremarkable 850s at the time with the air source further south than some might like but the Eurasian bloc is very much in charge at this stage with the Atlantic moribund.  

12Z GFS OP - perhaps the pick of the output last evening with a classic route to an E'ly - some similarities to what tonight's GEM is showing - but with increasingly cold 850s as we approach mid December. The initial trough disruption south means by T+108 a defined and quite deep LP over North Wales with presumably plenty of rain, strong winds and hill snow.  It doesn't clear fully to the south but fills slowly over or just to the east of the British isles as pressure rises to both east and west. Moving further into FI and we find a bit of a stalemate developing with pressure rises to the east and west slowly squeezing out the residual trough which has by T+264 headed south to a core position over Corsica. Ultimately, as you might expect from GFS, the Atlantic re-asserts and by T+384 there's quite a familiar look but the LP still aligns negatively. The NH profile suggests a new but shallow PV re-forming over Canada and the 10 HPA profile in FI is very interesting with warming first from Siberia and then from Europe putting a lot of pressure on the vortex so it's an interesting scenario if not perhaps quite as positive for cold fans as yesterday.

12Z ECM - better last night than Friday I thought. As we see with the other models, the LP sinks south and by T+120 the centre is over northern Britain. By T+168, the LP has moved further south to Biscay but there's no rapid build of pressure behind initially as the next Atlantic LP is already sliding SE further to the west of the British Isles and by T+240 the LP is off the west of Iberia and there is a clear pressure rise to the west and North west while at the same time the Eurasian HP had extended a ridge into Scandinavia. I'm struggling to see the very cold 850s but I'm not seeing a raging Atlantic either. I'm seeing a disorganised PV suggesting an anticyclonic set up is very much on the cards.

Where are we then this evening? The initial evolution is clear but there remains a lot of uncertainty as to how the LP exits to the south and where it goes and whether we will see the build in pressure behind it. Both GEM and ECM suggest we will see this but GFS is less clear and defaults back to an Atlantic-led scenario deep in FI (well, the OP does, Control is if anything even messier suggesting a lack of clarity in the medium to longer term). 

[Snowboard Tennyson IOW]

Needs to cool down considerably down here (S England) over the coming days to ensure any precipitation becomes what we want. Models are very interesting and in my view good watching currently, get the block/s in and the rest could evolve. Bumped into a Net weather enthusiast today locally which is a first, and we both discussed the past few years model watching  and the great expertise on this forum. Let’s get this pattern locked and loaded

[legritter]

Hi Gang ,well all looking good for our first week of Winter , and i am over the moon , i would say a fair chance that eventually many of us will see falling snow , and a possibility that high pressure could rise to the north of the uk .I did say falling snow not settling snow ,so lets hope the charts over the coming days gives us coldies some early cheer .great forum ,great posters ,great week coming up ,STellas on ice .

[sheikhy]

Icon much further east now!!mainly due to slightly less amplification in the atlantic!!is that a good thing in the long run?

[snowsummer]

21 hours ago, DiagonalRedLine said:

Yep, going through the lush countryside down many winding roads, but find themselves getting lost as they find the sign posts for freezing, wintry, weather. They should have gone down the highway!

I think we have to step back and look at the bigger picture.  Think of the snow like a train. You look down the lines and see it in the distance. Its on its way but not here yet. And when it arrives at the station we've still  got to wait for the doors to open.... now where have we heard those words before.....

[booferking]

Further west wintry precipitation increasing on icon.

[sheikhy]

Fantastic icon!!seems to have pushed everything further east with each run today!!sign of things to come?

[northwestsnow]

Icon 18zis a fair bit colder then its 12z offering...

Edited November 29, 2020 by northwestsnow

[sheikhy]

2 minutes ago, northwestsnow said:

Icon 18zis a fair bit colder then its 12z offering...

And also looks more like the ukv posted earlier for friday!!

[Tim Bland]

Patches of -5c air in the midlands / south!! Loads of precip = ️

[Scott Ingham]

These diving lows historically tend to shift east slowly closer to the time. Its usually as we hit the 72-96 range and under. I still think there is scope for further eastward adjustments between 200 and 400 miles by T-0

Edited November 29, 2020 by Scott Ingham

[Mike Poole]

Well winter starts in 2 days folks, and instead of staring down the barrel of endless zonal patterns, there is so much interest.  As yet the mouthwatering patterns shown on some models are tempered by a lack of cold air anywhere near the UK but that will change as we move deeper into winter.  It seems to me that it is all about disconnects at the moment:

The atmosphere doesn’t seem to be behaving as if it’s influenced by La Niña - here’s the CFS AAM forecast:

Not bothered too much about the forecast trajectory at the moment, but right now AAM is in positive territory, which is not really what you’d expect with La Niña, so there’s Disconnect 1 there.  

Disconnect 2 - the strat and trop vortex, I’ve posted about this before, but while the strat vortex spins faster, the trop vortex is all over the place.  Here’s the NAM chart with forecast from today’s GFS 0z:

Showing increasing -AO in the trop, while the strat is +AO but maybe losing some strength, although the zonal winds are still fast.  No coupling anytime soon is my take.  All to the good.  

SSTs, what are they like?

No tripole unfortunately but cold out west and warm in the North Sea, if we can get an easterly with teeth in the next few weeks then potential for convection and snow showers.  

ECM 12z ensemble mean:

This is looking good, vortex away to Siberia, Atlantic ridge, Euro trough...and a possible SSW on the cards if the current patterns aren’t enough...with a deck this loaded we can’t possibly fail to land one of these at some point folks:

All the best, Mike

[sheikhy]

6 minutes ago, Tim Bland said:

Patches of -5c air in the midlands / south!! Loads of precip = ️

IF the gfs follows the icon am gona go crazy!!!!!!!