Model Output Discussion - Deeper into Autumn

[Frosty.]

The longer term GEM 12z mean doesn’t look either unsettled or settled, kind of in-between, there are some benign members but also some deeply unsettled ones in early December…and the faint possibility of an easterly?..which is what most of us want at the start of the meteorological winter!!!!…but failing that, at least something more seasonal /  settled with frost / fog following all the unsettled mild Atlantic gunk?! ️ 

Edited November 20, 2022 by jon snow

[Cambrian]

Another fairly wet week ahead and through next weekend, away from the north of Scotland, 12z GFS op and para - days 1-8 precipitation.

 

Particularly wet in southwest England, Wales, the west of Ireland and parts of County Down on the total accumulated precipitation, another 100-125mm for some.

  

Well above average rainfall for the southern half of the UK, diminishing soil moisture deficits.

Soil moisture (GFS op) day 1 / day 8

  

The ground is already saturated here, springs popping up everywhere, not out of the ordinary for these parts in November mind, although overall, it’s a wet one to say the least - 175mm already this month, looking like a 300mm month is eminently possible. Thereafter, week 2 looking a lot drier, in the southern half of the UK and Ireland at least, and viewing of the 30mb+ rise in pressure between tomorrow and the beginning of December on the 12z GFS ensemble mean is most welcome. 

Edited November 20, 2022 by Cambrian

[Eagle Eye]

10 hours ago, mushymanrob said:

This is interesting, as the latest NOAA chart (right) clearly intensifies the blocking to our North and East since the previous chart (left) 4 days ago. Actually, this block has steadily grown for some time now on these charts.
But that is some predicted block, stretching from Siberia Westwards to Northern Canada. Assuming this is going to be accurate - this is supported from other anomaly sources, then after an initial milder spell, gathering cold to our East must become a threat in early December. The salient point here is that the block is expected to strengthen, not stay put or weaken, but strengthen.

Mushymanrob ramp...

Do not get excited...

Do not get excited...

Alright, I'm a little excited.

Stay tuned mid term, the Stratosphere is getting interesting...

Then slightly further on and we have the EHF's in the Greenland-European area ready to continue to affect the Stratosphere.

 

And that's shown by a relatively well-placed Stratosphere.

Edited November 20, 2022 by Eagle Eye

[stodge]

Tonight's ECM gets to what I thought we might see but the question then becomes whether it will be an MLB or HLB?

It's fair of course to argue that T+240 changes all the time - yes, it does - but the point about model watching is to spot trends and signals which move into the reliable which is for me T+96 to T+120.

What I'm not seeing currently is a raging Atlantic with LP crossing the British Isles into Scandinavia and beyond - indeed, getting an LP across the Meridian has been a struggle so far. The block to the "east" has been and remains substantial but there's currently an early taste of cold for Germany, Poland and Scandinavia with a small LP developing in the cold airflow and that energy extends west and draws ou trough further east and south east for the first part of the week.

[Frosty.]

The longer term ECMWF 12z ensemble mean has taken another step towards settled!…the operational has really followed through on that idea… tap the barometer time!..hopefully a more seasonal, settled end to autumn / start to winter with frost and fog but also some sunshine too!…fingers ️ 🌫   

 

Edited November 20, 2022 by jon snow

[Cambrian]

Yes. A few weeks of stalemate perhaps coming to an end. After many days of seemingly mere calendar holder synoptics until the real events are confirmed, our usual emphasis on the word “foreseeable” having had even more gravity than usual, but buoyed by our awareness that emerging signals of changes once detected can immediately compute into quite dramatic downstream pattern changes, this finally appears to be one of those instances.

  

12z ECM ensemble mean anomalies for days 2, 6 and 10. Day 2, the trough at its most proud, running from the Atlantic, through the UK and Ireland to Europe. From there, first the ‘squeeze’, from above and below, on that extension of the trough into Europe by day 6. Then by day 10, the ‘push-back’ of the Atlantic trough all the way to the western side of the ocean, a firm foundation to an anticyclonic start to winter proper. 

Edited November 20, 2022 by Cambrian

[Rayth]

Does anyone have the link to the model output thread in the lead up to winter 2010? Been looking for nearly an hour now, would be very interesting/educational to see how things developed 

Mods . Please move to an appropriate thread if needed, didn’t know where to put this initially 

[blizzard81]

A nice outlook into December from the CFS. 

[Allseasons-Si]

There are signs on the latest EPS that the heights over to our NE look to retrogress west towards Greenland.

@blizzard81how uncanny is that! ,that you post the cfs showing retrogression from Scandi to Greeny

 

Edited November 20, 2022 by Allseasons-si

[Kirkcaldy Weather]

4 minutes ago, blizzard81 said:

A nice outlook into December from the CFS. 

Thanks for sharing, hope you don't mind I've zoomed in a bit and got a better view from our perspective

Week 3 Week 4

 

[blizzard81]

11 minutes ago, Allseasons-si said:

There are signs on the latest EPS that the heights over to our NE look to retrogress west towards Greenland.

@blizzard81how uncanny is that! ,that you post the cfs showing retrogression from Scandi to Greeny

 

I was thinking exactly the same when you just posted those charts

11 minutes ago, Kirkcaldy Weather said:

Thanks for sharing, hope you don't mind I've zoomed in a bit and got a better view from our perspective

Week 3 Week 4

 

They look even better that way up

[Allseasons-Si]

The gfs going in the right direction this time,cold pool building to our east

Edited November 20, 2022 by Allseasons-si
added info

[January Snowstorm]

For late Nov/early December this is quite an extraordinary chart!!

Edited November 20, 2022 by January Snowstorm

[Bristawl Si]

10 minutes ago, January Snowstorm said:

For late Nov/early December this is quite an extraordinary chart!!

Can you explain why? Just looks dry and cool.

[geordiekev]

9 minutes ago, January Snowstorm said:

For late Nov/early December this is quite an extraordinary chart!!

Reminds me too much of last Dec when the UK high was a hinderence rather than a friend. It was a whisker away from producing widespread goods in the end so not the worst of garden paths to begin

[Allseasons-Si]

I hope that's Casper the friendly ghost

jokes aside,TPV well over to the Asian side with huge azores hp cell to our SW,i hope this pushes north into Greenland on the later frames

edit: incoming from the north i would think from here.

[damianslaw]

18 minutes ago, Bristle Si said:

Can you explain why? Just looks dry and cool.

I think what is unusual is the extent of abundant heights over whole of Europe extending into the atlantic. The reason being the position of the PV, main core sat well on the asian side, allowing heights to build in situ and more importantly back west and north in time.

1 minute ago, Allseasons-si said:

I hope that's Casper the friendly ghost

jokes aside,TPV well over to the Asian side with huge azores hp cell to our SW,i hope this pushes north into Greenland on the later frames

edit: incoming from the north i would think from here.

There's that date again 5 Dec, watch this space..

[Allseasons-Si]

Here's one for you @CreweCold

Warming more prominant on the 18z run...

[Seasonal Trim]

2 hours ago, Rayth said:

Does anyone have the link to the model output thread in the lead up to winter 2010? Been looking for nearly an hour now, would be very interesting/educational to see how things developed 

Mods . Please move to an appropriate thread if needed, didn’t know where to put this initially 

Unfortunately, I don't think it exists anymore. 

[johncam]

Should we not be looking at the parallel which unless I am mistaken is taking over?

[Ali1977]

1 minute ago, johncam said:

Should we not be looking at the parallel which unless I am mistaken is taking over?

Not when it’s a rubbish FI we shouldn’t

[Eagle Eye]

This week on Olivia chooses: 

A document going into Stratospheric Eddy Heat Flux events in an idealised model 

Luckily it's a document that can be summarised in only a couple paragraphs as it's almost entirely what I've said before.

As discussed before, the coupling between the troposphere and the stratosphere is one of the main forces in the Winter circulation. This is often shown by the Eddy Heat Fluxes on weather models. These denote the change from the zonal mean (Eddies). Positive values denote vertical wave movement. Reanalysis studies showed that accumulating strong Eddy Heat Flux(EHF) anomalies occur prior to a SSW.

Extreme stratospheric eddy events are shown by "extreme positive zonal-mean wave-1 meridional heat flux values" compared to January, February, March (JFM) values. JFM used because that's when wave-1 amplitudes are at their highest.

The results of the experiment confirmed that it was mainly tropospheric Eddie's where the wave interaction and therefore the main part of EHF vertical propagation occurs and that the Stratosphere isn't the main place of specifically wave-1 interaction.

So, we look to the future now and at  the wave amplitudes.

Wave number 1 looks to dominate just past the 1st of December on the boundary between the Troposphere and the Stratosphere and that should increase coupling going into mid December with the upper-Stratosphere.

From the 17th November on the ECM, there really is no solution for now, it's a 50/50 but I'd like you to note, the weakening of the 10hPa values coming up in a few days wasn't really showing until the 10th/14th November runs, before that the trend was for it to continue to trend upwards with only a few ensembles showing down, much more are showing a downward trend this time. I think it's a case of too far away for now.

The EHF anomalies just beyond the first on the forecast part (far right) looking quite strongly positive and propagating vertically, not a bad position to be going into proper Winter in, definitely could be worse.

The NAM at the surface looks to be moving towards strongly negative for really the first time since we got into possible proper cold and snow territory. Beyond the surface and we have a short negative NAM in the Stratosphere and another one heading for the Stratosphere into early December,. Generally a negative NAM is better for cold here and I imagine in turn, warmer over the Arctic, so if we can get a strong negative NAM in the Stratosphere, that could be indicative of a possible future SSW but for now way too far off to tell and I am definitely not saying we're getting a SSW, it's still on the unlikely end of solutions.I think my 35% chance is probably a fairly accurate representation.

[Jason M]

Just looked through the GEFS at 192 hours to take a quick snapshot. Not really any indication of anything notably cold to be honest. Maybe looking at a period of calm weather with near normal temps. 

[Allseasons-Si]

I am kind of liking what shift has been taken by the op/control from the 12z to the 18z,...that is some shift back W/NW by them both...

gfs op 18z 240 vs 12z 252

control 18z 240 vs 12z 252.

this is a good step in the right direction to me.

[BlueHedgehog074]

2 hours ago, Rayth said:

Does anyone have the link to the model output thread in the lead up to winter 2010? Been looking for nearly an hour now, would be very interesting/educational to see how things developed 

Mods . Please move to an appropriate thread if needed, didn’t know where to put this initially 

Hi Rayth, also been trying to look myself, but sadly no luck finding anything. Have a horrible feeling that the Models threads from around that period have probably vanished into some kind of hidden vortex of the Netweather universe. (Maybe a small chance Paul might know something).

Although not on the lead up to Winter 2010, John Holmes did a thread around December that year focussing on the daily output of the 12Z models:

https://community.netweather.tv/topic/66549-a-daily-look-at-the-12z-output/#comment-1981122

 

27 minutes ago, Allseasons-si said:

I hope that's Casper the friendly ghost

 

Looking where both Casper’s hands are pointing, he’s seems to be showing the ideal ways for High Pressure to head in for cold (North-East or West).