Model Output Discussion - Into the new year

[SMU]

Afternoon....

You can sense the excitement building in here...

This cold spell will have many layers however the theme of cold becoming colder & colder > with the possibility of an even colder layer to come ( day 10 > )

The ensembles can be layered in the same way > 

06z displays this nicely...

So as we head through this week > as the cold air becomes established & milder layers of the boundry layer mix out & rain / sleet is replaced by sleet / snow....

[bobbydog]

23 minutes ago, Paul_1978 said:

Post again when it’s within T+200  

To be fair, strat charts don't change as dramatically as trop charts so they're much more reliable.

Here's a chart of the warming at just 72 hours, to keep you going... 

 

[Scott Ingham]

2 minutes ago, Steve Murr said:

Afternoon....

You can sense the excitement building in here...

This cold spell will have many layers however the theme of cold becoming colder & colder > with the possibility of an even colder layer to come ( day 10 > )

The ensembles can be layered in the same way > 

06z displays this nicely...

So as we head through this week > as the cold air becomes established & milder layers of the boundry layer mix out & rain / sleet is replaced by sleet / snow....

Cold building in situ. So classic for this time of year! 

Agree. Getting colder and colder and colder. Tonight wont be the only chance of snow its just your bread and butter before the starter even comes out 

[MJB]

5 minutes ago, Steve Murr said:

Afternoon....

You can sense the excitement building in here...

This cold spell will have many layers however the theme of cold becoming colder & colder > with the possibility of an even colder layer to come ( day 10 > )

The ensembles can be layered in the same way > 

06z displays this nicely...

So as we head through this week > as the cold air becomes established & milder layers of the boundry layer mix out & rain / sleet is replaced by sleet / snow....

Hi Steve

Can you please direct me towards that chart on Meteociel ?

[Kasim Awan]

5 minutes ago, Scott Ingham said:

Cold building in situ. So classic for this time of year! 

Agree. Getting colder and colder and colder. Tonight wont be the only chance of snow its just your bread and butter before the starter even comes out 

Agree, let's not get caught up on the snow risk within 24 hours. The flow in the next 4 days is optimal for both an inversion & surprise shortwaves. A pattern which is conducive to producing fairly prolonged snow cover very locally.

Edited December 27, 2020 by Kasim Awan

[Catacol]

Afternoon all - I’m a bit late to the party today....though not in the same league as @Scott Ingham who has pulled an all nighter and seems still be be going. As others have said - get to bed man!

Interesting data this morning - a little wobble from GFS overnight but nothing out of the ordinary in that regard. The models are beginning to pick up on change data post New Year and it will widen the range of solutions.

So where are we? In no particular order...

Momentum products show that we are in the downward slope of the most recent phase. Frictional torque has topped out and is likely falling already (chart dated 24/12)

and mountain torque is also falling - part of the ongoing wax/wane cycle and the never ending attempt of the earth and atmosphere to move momentum to net zero.

The next pacific jet streak on the back of the significant EAMT first widely advertised by Eric Webb on Twitter is moving into the semi-reliable window and this will signal the next upward momentum phase. As this jet ploughs through the pacific it will act as an eddy creator, and given the relatively weak zonal wind speed at the moment the wave breaks will be more significant. Always easier to break a relatively static pattern than cause an eddy in an already swift moving pattern.

 

 

Given lag impacts of this streak what is extended NWP looking like today? The gfs op is odd - reignites the Atlantic and then responds to the momentum state by throwing up a peculiar ridge from Canada to Greenland. 

 

I suspect the gfs bias towards a cyclonic Atlantic signal is causing it some grief here. Better is the ECM solution which we can only see out to 240 but shows a more likely mid Atlantic ridge.

 

 

With a trough already embedded over Europe - and assuming this is the “correct” path - then greater intensification of the cold over NW Europe will follow. Strat products flag this pattern well, with the forecast for the strat/trop boundary maintaining a strong Euro trough signal

 

and GFS at 240 also shows a Euro trough signal

 

Putting this all together....we have a waning phase about to start, but without much zonal momentum the pattern will stay blocked. Then the next uptick (wax) after New Year that will reenergise the ridge, reinforce the Euro trough and intensify the cold. Note this is all BEFORE any SSW impacts. Not time yet to muse with any precision on these, though I’m sticking with a projection of a split.

Coldish week this week. Staying so beyond New Year. And then cold digging in harder by zero hour of 7 Jan. @chionomaniac may well be correct in aiming at Jan 10....but for variety I’ll hold my crosshairs on Jan 7. Beyond that? Wait and see...

 

 

Edited December 27, 2020 by Catacol

[Daniel*]

I don’t think you can get a much better outlook if you love cold temperatures, frost and ice what winter should be. No current indications for anything particularly snowy, nonetheless things are bound to pop up. And looking at FAX charts they show a lot of features most days next week within cold flow.

I thought 00z EPS was very intriguing retrogression signal from heights to NE to Greenland totally normal stuff. 

 

[SMU]

6 minutes ago, MJB said:

Hi Steve

Can you please direct me towards that chart on Meteociel ?

Go to the GEFS ENS

then hit table & click on your location

Then filter is to 850 s & ascendant

[Scott Ingham]

9 minutes ago, Kasim Awan said:

Agree, let's not get caught up on the snow risk within 24 hours. The flow in the next 4 days is optimal for both an inversion & surprise shortwaves. A pattern which is conducive to producing fairly prolonged snow cover very locally.

Yeah agreed! Whem you have such low heights its a slow moving convective recipe of surprises.

The south had a red warning for 20cm+ that only showed within 12 hours of it happening in 2010.

Granted overall the cold was a LOT colder but the instability was similar as was the slackness of the flow

[Scott Ingham]

14 minutes ago, Catacol said:

Afternoon all - I’m a bit late to the party today....though not in the same league as @Scott Ingham who has pulled an all nighter and seems still be be going. As others have said - get to bed man!

Interesting data this morning - a little wobble from GFS overnight but nothing out of the ordinary in that regard. The models are beginning to pick up on change data post New Year and it will widen the range of solutions.

So where are we? In no particular order...

Momentum products show that we are in the downward slope of the most recent phase. Frictional torque has topped out and is likely falling already (chart dated 24/12)

and mountain torque is also falling - part of the ongoing wax/wane cycle and the never ending attempt of the earth and atmosphere to move momentum to net zero.

The next pacific jet streak on the back of the significant EAMT first widely advertised by Eric Webb on Twitter is moving into the semi-reliable window and this will signal the next upward momentum phase. As this jet ploughs through the pacific it will act as an eddy creator, and given the relatively weak zonal wind speed at the moment the wave breaks will be more significant. Always easier to break a relatively static pattern than cause an eddy in an already swift moving pattern.

 

 

Given lag impacts of this streak what is extended NWP looking like today? The gfs op is odd - reignites the Atlantic and then responds to the momentum state by throwing up a peculiar ridge from Canada to Greenland. 

 

I suspect the gfs bias towards a cyclonic Atlantic signal is causing it some grief here. Better is the ECM solution which we can only see out to 240 but shows a more likely mid Atlantic ridge.

 

 

With a trough already embedded over Europe - and assuming this is the “correct” path - then greater intensification of the cold over NW Europe will follow. Strat products flag this pattern well, with the forecast for the strat/trop boundary maintaining a strong Euro trough signal

 

and GFS at 240 also shows a Euro trough signal

 

Putting this all together....we have a waning phase about to start, but without much zonal momentum the pattern will stay blocked. Then the next uptick (wax) after New Year that will reenergise the ridge, reinforce the Euro trough and intensify the cold. Note this is all BEFORE any SSW impacts. Not time yet to muse with any precision on these, though I’m sticking with a projection of a split.

Coldish week this week. Staying so beyond New Year. And then cold digging in harder by zero hour of 7 Jan. @chionomaniac may well be correct in aiming at Jan 10....but for variety I’ll hold my crosshairs on Jan 7. Beyond that? Wait and see...

 

 

Hahaha! I actually had a couple of hours while the 06z rolled out and im good to go again now

As usual a world class post mate and basically it sums up my own thoughts in a technically brilliant way with supporting charts as evidence! 

Everything is still on track!

Now show me wax next week!

[Kasim Awan]

9 minutes ago, Scott Ingham said:

Yeah agreed! Whem you have such low heights its a slow moving convective recipe of surprises.

The south had a red warning for 20cm+ that only showed within 12 hours of it happening in 2010.

Granted overall the cold was a LOT colder but the instability was similar as was the slackness of the flow

I am really interesred in what this Precip will do tomorrow between Bristol and Eastbourne. The cyclonic swirl is being picked up on the Harmonie & some others. At longer range I would be speculative however at just -T24 it is feasible. Additionally the smaller / slightly weaker signal to the low now means this is an increasingly likely feature. It might produce a localized 5-7cm.

Edited December 27, 2020 by Kasim Awan

[Scott Ingham]

2 minutes ago, Sheldon Cooper said:

The latest Cold Spell was predicted for the 21st, it was 2 Days out I expect the Same to happen with the next Cold Spell pinpointed by @chionomaniac but until @Steve Murr is definitly on board we need to be wary. 

5th of January onwards following the eamt and pacific jet streak. Give or take a day.

[Scott Ingham]

10 minutes ago, Kasim Awan said:

I am really interesred in what this Precip will do tomorrow between Bristol and Eastbourne. The cyclonic swirl is being picked up on the Harmonie & some others. At longer range I would be speculative however at just -T24 it is feasible. Additionally the smaller / slightly weaker signal to the low now means this is an increasingly likely feature.

What are your current thoughts? 

It does look like a developing system

Doesnt matter ive just seen the totals on your edit 

Edited December 27, 2020 by Scott Ingham

[Ols500]

this chart looks nice

[Kasim Awan]

3 minutes ago, Scott Ingham said:

What are your current thoughts? 

It does look like a developing system

The initial front looks to produce 1-2cm locally 2-4cm where there is a slight pivot across W Mids Wales, room for sway either way to C Mids & restricted to Wales coast still so an element of nowcasting. Precip also getting into West Country as a mix locally 2-4cm over 200m. 

Another wave early tomorrow West Country SW Mids, marginal south of m4 corridor 9am-12 however producing locally 1-3cm in heavy ppn. Later in day winds spinning to east with localized heavy ppn. Still marginal south of M4 but temps falling so more localized accumulations. Sweet spot tomoz could be 100m+ M4 corridor down towards I of W.

[Frosty.]

I used too be quite the weatherman at school..the number of kisses from the girls  I got when I told them it was going to snow!..wow, those were the days!...anyway..a few more from the GEFS 6z..absolutely stunning potential!!..fingers GANG..sausage baps and stellas all round if it verifies!..is that ok with you legritter?    

 

Edited December 27, 2020 by Jon Snow

[MATTWOLVES 3]

Subtle differences with any snow tomorrow,regarding the Swiss HD,the Euro4 and the ECM 6z graphs...ECM keen to keep it further West further South...one thing they do all agree on is the NW could be getting a pelting.. So any of you up that way,its looking good.

[XtremeUKWeather]

So far NNN 2km is accurate with the band of precip currently

UKV, ECM, ICON all way off 

Harmonie somewhat similar as well

[phil nw.]

Some posts have had to be removed. Can we please keep to model discussion please all. 

Chat in the appropriate threads please. 

Thanks. 

 

[weirpig]

Latest thoughts  for the snowfall from the icon.

[iowpompeylee]

34 minutes ago, Ols500 said:

this chart looks nice

Bin it... if only: Thats never going to happen. Doesn’t snow on the Isle of Wight.... only snows once every 20 odd years here!! 

[legritter]

Hi gang ,charts looking good into January, we all know how they can change in the area of out past 168 hrs and even sooner If with a possible SSW early January. Im very happy with the next 96 hrs as surprise synoptics pop up , Fax charts at the ready ,radar turned on ,Lets hope ecm is a good one tonight ,perhaps some eye candy from Gfs in about an hours time ,right SAUSAGE BAPS ,And STEROIDS  sorry STELLA'S on me ,great forum gang ,let the Hunt commence, cheers . 

 

 

[markw2680]

7 minutes ago, weirpig said:

Latest thoughts  for the snowfall from the icon.

If that is anywhere near what happens we could be in for quite a covering in the Midlands 

[Geordiesnow]

I think the issue on here with some is the charts on the face of it don't really look all that snowy yet I can't deny, when you see kinks and little low pressure systems, it's a forecasters nightmare. 

It would seem to me the trend in terms of uppers is they will go slightly colder as the week goes on. Aslong as skies remain clear at night, there should definately be some sharp frosts around also. 

The UK will remain on the cold side of the jet for a while yet but there is no signs of a big freeze and looking at the northern hemisphere charts, it looks meteologlly impossible for any Arctic air to drop into Scandinavia so it is going to be down to the models picking up on areas of lower thicknesses which may in turn develop a colder pool of air and hopefully head our way. 

I still stand by any snowfall at this stage will be transient but given the slack set up, I would not rule out some disturbances developing but whether the air above is cold enough to fall as snow at lower levels remains questionable. 

[Ben Sainsbury]

UKV 12z shows a slight eastward shift compared to its 9z run, slight uptick in intensity too.