Model output discussion - Winter has arrived and the hunt for cold is on

[northwestsnow]

6Z looks a bit nippy for those going to the poll booths !!

-9 at 9pm in parts of Scotland !!!!!

Edited December 4, 2019 by northwestsnow

[MR EXTREMES]

my take on the models is that its becoming more and more clear that a southeasterly tracking jet and holes of heights popping up over the northern hemisphere are really ramping up some of the rainfall spikes again are absolutely incredible.

now the way i see it is there's no doubt cold shots are lining up.

09/10 did not have an early warming of the stratosphere, but what was a feature that winter was the wave breaking effects this was on going just as we seen this season.

so no sudden stratospheric warming but next best thing.

also the vortex holiday is a welcome visit over outside of the pole into scandinavia.

my punt would be cold shots from the northwest and northerlies then as heights have a reshuffle eventually a northeasterly perhaps eastlerly as on of these little sliders will dig far enough south to really open the flood gates to wintry potential even though there is already a few showing.

law of averages would suggest eventually all that cold filtering down into mid latitudes.but as soon as that jet stream has a more zonal influence and if heights build to our south then you could safely say cold reduction likely.

but until then we have cross model agreement.

and to be fair i've seen in the past all models going for greenland scandi blocks and drop the idea at t96hrs.

but this season is pretty much inline with some of the classic winters of old like 80s.

but im still 80% at moment on some pretty wintry weather.

gefs only has one cold shot.

ecm only has one cold shot.

gfs has a few cold shots with cold established with longer duration.

gem has one cold shot.

so not totally a done deal but more than likely at least a cold shot in the next 10 days.

nao weak positive and ao up and down like hookers knickers.

so no doubt alot going on.

[Frosty.]

The Ecm 0z ensemble mean is still looking cold longer term with an increasing risk of snow / snaw! ❄❄❄❄

Edited December 4, 2019 by JON SNOW

[Methuselah]

So here are the GEFS 06Z ensembles...But, before making any sweeping statements, a question: is the 'GFS Operational' the FV3 or the GFS Legacy...?

   

    

Because, whichever it is, NW-SE tracking jetstreams have been known to 'do the unexpected'...

[LRD]

8 minutes ago, Ed Stone said:

So here are the GEFS 06Z ensembles...But, before making any sweeping statements, a question: is the 'GFS Operational' the FV3 or the GFS Legacy...?

   

    

Because, whichever it is, NW-SE tracking jetstreams have been known to 'do the unexpected'...

Still a fair few cold shots from most ensemble members there. Control is nice in far far away land

And a few others toy with the idea of height rises directly to our NE too

True, there are half a dozen SW'ly shockers aswell!

Edited December 4, 2019 by LRD

[northwestsnow]

EC 00z ens highlight the cold option later next week.

 

[jules216]

3 minutes ago, northwestsnow said:

EC 00z ens highlight the cold option later next week.

 

@northwestsnow, do you have link to the source of that image? thanks

[MATTWOLVES 3]

Here are a few pretty cold ensembles from the 6Z to keep you going till the 12s roll out....ohh the joys! And before everyone points out any snow will be reserved to high ground in the North.... Expext the unexpected with this set up!!! Remember December 2017,when a slider event with a Nthly brought a good 8 inch of snow to a good chunk of the Midlands!! Anything is possible good folk... Enjoy your days. 

[StretfordEnd1996]

Just now, northwestsnow said:

EC 00z ens highlight the cold option later next week.

 

Absolutely -

Still think that Thurs-Sat next week is very much plausible for a good decent Northerly 

The downgrades we've seen overnight never actually got rid of the possible cold from around Thurs-Sat. They lowered chances of cold prior to Thurs and probably lowered the potency slightly of days 7-10 but in my opinion still all to play for.

I can see agreement in this mornings output that it will be a bit of a short lived affair but at D7-10 I don't see much at the moment that it isn't going to be exciting

[northwestsnow]

Just now, jules216 said:

@northwestsnow, do you have link to the source of that image? thanks

There you go mate.

Weather: Ensemble forecast

WWW.WEATHERCAST.CO.UK

---

Ensemble forecasts identify the expected spread of weather conditions and assess the probability of particular events

 

[SteveB]

Surely with a southerly tracking jet, and the fact that we are still talking about weather 6-7days away, there is plenty of time for upgrades..... and yes downgrades too.

[northwestsnow]

4 minutes ago, StretfordEnd1996 said:

Absolutely -

Still think that Thurs-Sat next week is very much plausible for a good decent Northerly 

The downgrades we've seen overnight never actually got rid of the possible cold from around Thurs-Sat. They lowered chances of cold prior to Thurs and probably lowered the potency slightly of days 7-10 but in my opinion still all to play for.

I can see agreement in this mornings output that it will be a bit of a short lived affair but at D7-10 I don't see much at the moment that it isn't going to be exciting

I agree with all you wrote..

Some kind of northerly airmass still looks likely around 12-14th Dec -those on the north side of the jet will probably see temps plummeting at night given we are fast approaching the shortest day of the year and the source of the air.

If this makes it then the 1st half of Dec will likely be below average temp wise-esp up North.

On the other side of the coin its beginning to look a bit grim longer term IMO- the Atlantic looks very very lively and there are growing signs we may see  strong PV setting up to the north west.

[nick sussex]

The theme of the late autumn and winter so far .

Upstream amplification has a problem surviving in the outputs . I’d view any further attempts with a pinch of salt until you get cross model agreement at day 6 .

 

[winterof79]

Quite happy with this set. 

The attempted warm up on the 10th is having the life squeezed out of it. 

So a colder period from 7th through to 16th with snow row showing nicely end of next week. 

[Ali1977]

29 minutes ago, nick sussex said:

The theme of the late autumn and winter so far .

Upstream amplification has a problem surviving in the outputs . I’d view any further attempts with a pinch of salt until you get cross model agreement at day 6 .

 

Getting cross model agreement at day 6 is as rare as rocking horse ****, never mind with ampliation involved. 
Personally I think things will improve on the 12zs for coldies, and they are already pretty good to be fair. 

Edited December 4, 2019 by Ali1977

[Kirkcaldy Weather]

8 hours ago, The PIT said:

FI downgrade which isn't a surprise with cold pushed deeper into FI which is normally an indication that it's none starter.

Not true, periods of interest look to still be around the 9th / 10th and possibly a few days later too - ensembles for here  last 4 runs  still the chance of ice day(s) too 

6 hours ago, snowstorm27x said:

Problem is that middle ground solution is useless to anywhere other than Scotland and the high ground of Northern England. There is no denying Snow or even a cold spell is odds against now and what is even worse now is the deep cold to the north and west of us will be charging thst damm Atlantic and creating some nice storms for the UK. Flooding again I predict will be the issue not snow unfortunately. Sucks but this chase is like a Dodo utterly dead. Next time we must wait for cross model agreement.

certainly not odds against (again especially further north) and some big snowfalls in the UK can happen with the battleground scenario or even sliding lows (storms in your post) just need the right angle on the lows trying to move in from the Atlantic.

3 hours ago, mb018538 said:

Cold enough for snow at elevation, but I suspect nothing at lower levels.

I wouldn't be so sure of that especially areas further north, cold zonality can easily produce wintry surprises even at lower levels as I have shown in previous posts.

3 hours ago, Skullzrulerz said:

In general GFS is only slightly better then last night but it's miles away from what showing the last few days... 

It's either pushed back further or has been wiped out

It's hard to believe overnight we're gone from a harsh cold spell to a topper but it was somewhat expected with seasonal forecasts mostly stating a cold spell around mid month

Unless things start changing soon I can't see anything noteworthy yet

As mentioned hasn't been pushed back and hasn't been wiped out and as for the other statement this was never a "harsh cold spell" at any stage (yes we had that 12z GFS run yesterday) but still not akin to 2010 or BFTE levels of cold / snow.

This thread gets more ridiculously chaotic every year  I posted this last winter and still by the looks of things needed by many again this year  many on here acting like this will be the only chance of colder weather for the entire winter, cmon now we are only 4 days in and as I have mentioned in the past things can change quickly and we still have ongoing events in the stratosphere and any possible effects from that, yes it is wise to be cautious especially after last winters failed easterly but to assume that every modeled cold spell will go the same way is ridiculous , much more enjoyable to approach with the glass half full rather than half empty 

Edited December 4, 2019 by Kirkcaldy Weather

[BLAST FROM THE PAST]

Well when I got up this morning I looked at the UKMO....and to me is stepping towards cold and is improving chances.  GFS was always going to initially pull away from perfection charts, but I still see very nice cold and snow potential.  ECM Plunges cold south......the southern snowcane disappeared....but there’s very much interest still here.  Yep a slowing of the cold arrival.....and those concerned re Atlantic coming in......it always was, there is no major Scandi block to come this month, but if the cold air can dig enough we get little wedges and trough disruption......that isn’t off the table....we are still seeing PV displacement to our NE......game very much still on 
 

BFTP

[SMU]

Afternoon All

Lets see where the afternoon runs take us then especially the UKMO -

Often with big corrections to another mid term solution they movement is often overdone -

Maybe there is a half decent midpoint??

Its amazing through isnt it > total model agreement on amplification at 96>120 of GEM / GFS / ICON / ECM yet 1 model even at a slightly lower resolution than some can churn out a different solution & be correct.

Ive sung the UKMOs praise I think for the last 4-5 years now & once again thats the go to model-

Anyway roll on the 12s can we get a bit of movement back to cold - it wouldnt take much!!

[Jordan S]

ECM shows very unsettled conditions next week with temperatures remaining pretty cold with snow for hills for the north perhaps to lower levels at times too wintriness to any precipitation not to be ruled out further south next week but the Atlantic depressions become more vigorous with frontal systems carrying some very heavy rain in places along with very strong winds for all pushing through..

Sunday..

11th..

13th..

With the jet remaining just over or to the south throughout the run then digging a long way south by day 9 uppers colder too. Details don't matter too much the overall pattern from the ECM is unsettled perhaps stormy with a wintry theme to add to the mix especially for the north.

[BLAST FROM THE PAST]

Stevie Murr

The NH profile of the UKMO to me is teetering on a plunge of arctic air, it doesn’t look as flat as yesterday morning, indeed looks primed

 

BFTP

[Mr Frost]

19 minutes ago, BLAST FROM THE PAST said:

Stevie Murr

The NH profile of the UKMO to me is teetering on a plunge of arctic air, it doesn’t look as flat as yesterday morning, indeed looks primed

 

BFTP

Agreed.

To be fair to @Steve Murr I think he threw his toys out the pram early this morning with regards to...it’s all over post!  

We all view the model output with a bit of IMBY mentality which is also fair enough.

For the North (and a few other parts of the UK and Ireland) today’s ECM, GFS and Met Office outlook show a potential wintry spell of weather from Tuesday onwards. (Especially towards the end of the week)

So for me being based in Scotland I now want the current charts all be to correct and countdown to 24 hours away! 

Of course I would love every member on here (who loves cold/snow) to see snowfall sooner rather than later! 

Onwards and upwards! 

Edited December 4, 2019 by Mr Frost

[danthetan]

25 minutes ago, BLAST FROM THE PAST said:

Well when I got up this morning I looked at the UKMO....and to me is stepping towards cold and is improving chances.  GFS was always going to initially pull away from perfection charts, but I still see very nice cold and snow potential.  ECM Plunges cold south......the southern snowcane disappeared....but there’s very much interest still here.  Yep a slowing of the cold arrival.....and those concerned re Atlantic coming in......it always was, there is no major Scandi block to come this month, but if the cold air can dig enough we get little wedges and trough disruption......that isn’t off the table....we are still seeing PV displacement to our NE......game very much still on 
 

BFTP

Unless Im reading the UKMO fax charts wrong the 0z was much better than yesterdays 12Z looking at the 500mb & MSLP

UK Met Office Fax Charts - UKMOMSLP Analysis and Prognosis - org

WWW.WEATHERCHARTS.ORG

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UK Met Office . . Europe and North Atlantic MSLP analysis and prognosis charts

 

[Mucka]

As I said this morning UKMO compared to its previous runs was actually a small improvement.

However the other models have moved significantly if not completely away from the sort of trough disruption we we were seeing well away from the UK with the best of those runs keeping the cold in place with snow for England while others had larger mild sectors but did not mix the cold out to our NE

ECM and GFS examples below 

Yesterday

Small ridge was much further West due to disrupting low and has already been undercut, hence heights moving NW.

Today

Small ridge just being shunted East no disruption/undercut

Here are the jet profile for yesterday at point of undercut (disrupting low) and today(bowling ball low)

And result

The disruption holds low pressure out West and disrupts their energy SE which allows for the amplification behind. Without the disruption the bowling ball lows barrel through and this has knock on upstream because the next low on a Southerly jet has nothing to "squeeze" against to create the necessary WAA and amplification. We can still get some but nothing like if we get the disruption and stalling lows.

To get  a wedge of heights or WAA you need a way of slowing the Atlantic down and without high pressure to run against the only way is disrupting troughs SE.

Get the disruption back and you will see a much more favourable FI although UKMO also led the way with how the PV would behave upstream spawning a deep low instead of a cul of over 1000mb a with previous ECM and GFS output which means upstream has more forcing, so a double whammy for any ridge trying to build around the 12/13th

Both these aspects were modelled by UKMO but not any other output, that is quite a beat down for mid range modelling and so you would think now we are closer and all the other output has moved to UKMO we are looking as a far more typical zonal spell, with snow chances for the N and hills, rather than a locked in cold with daytime maxima stuggling above freezing.

That is the way of it with the UK, fine margins can make huge differences.

Of course it is not over, things may change again this afternoon but I think if we see any sustained cold then it will be back to deeper FI - unless we see a big U-turn on that trough disruption!

 

 

Edited December 4, 2019 by Mucka

[booferking]

Voting day could be wet and windy not white if the icon is anywhere near right.

[Weathizard]

Poor from the Icon, but I would guess day 8-10 might be good would depend on that energy to the west whether it wants to flatten the pattern or not.