Model Output Discussion - Into Winter

[Big Gally]

Around the  27th 

[blizzard81]

5 minutes ago, Big Gally said:

Around the  27th 

All very wishy washy though. No ooompff! It won't deliver what most of us want. 

[joggs]

1 hour ago, BLAST FROM THE PAST said:

Tell that to Russia, China, Korea, Mongolia, SE Asia, Japan, etc etc….NOT the thread 

 

BFTP

Sorry Fred. You always come across as a matter of fact. How many times have you been wrong on here.......

It was a reply on THIS thread about Iberian heights.

Edited December 21, 2023 by joggs

[joggs]

1 hour ago, BLAST FROM THE PAST said:

Tell that to Russia, China, Korea, Mongolia, SE Asia, Japan, etc etc….NOT the thread 

 

BFTP

I was replying to someone about the Iberian heights and I believe that climate change is the cause. It WAS on this thread. Also you replied in this thread.

[bluearmy]

33 minutes ago, Don said:

Wasn't it seeing the removal of Iberian heights earlier in yesterday's update?

As commented above, today’s run goes even later. There is run to run variance on this so wouldn’t take it all too literally. 

[northwestsnow]

18z

day 12

[Don]

15 minutes ago, bluearmy said:

As commented above, today’s run goes even later. There is run to run variance on this so wouldn’t take it all too literally. 

Absolutely, but the fact that it's being delayed is not a good sign.

[Don]

23 minutes ago, joggs said:

I was replying to someone about the Iberian heights and I believe that climate change is the cause. It WAS on this thread. Also you replied in this thread.

I've been thinking (and I'm sure others have too) that had this winter occurred 20 or 30 years ago, it would likely have been a straight forward cold season, with the pesky Iberian heights being less of an issue?

[bluearmy]

3 minutes ago, Don said:

Absolutely, but the fact that it's being delayed is not a good sign.

That depends if you have any faith in the output post ssw 

of course if there is no reversal then the charts are standard ec46 fayre - which is week 3 to be noted and the rest is just a loose indication of where things may head 

[Relativistic]

1 minute ago, Don said:

I've been thinking (and I'm sure others have too) that had this winter occurred 20 or 30 years ago, it would likely have been a straight forward cold season, with the pesky Iberian heights being less of an issue?

You would think so. The Hadley cell's got to be bigger than it was 30 years ago.

[Don]

4 minutes ago, Relativistic said:

You would think so. The Hadley cell's got to be bigger than it was 30 years ago.

Exactly and as an example, I'm thinking we could have had a late December cold spell, similar to that in 2000, had the Iberian heights not been around this year, courtesy of smaller Hadley cells?

Edited December 21, 2023 by Don

[sundog]

3 minutes ago, Don said:

I've been thinking (and I'm sure others have too) that had this winter occurred 20 or 30 years ago, it would likely have been a straight forward cold season, with the pesky Iberian heights being less of an issue?

I agree. The weather this week would have likely been much colder then the muck we are getting atm. That cold air to our north would have pushed south. Nowadays stubborn hp to our south is like a bloody wall in the path of cold trying to reach us ( of course there can be other factors too ) but this week has been a perfect illustration of that imo.

[northwestsnow]

Excellent 18z..

Lots of options after New Year..

 

[WYorksWeather]

2 minutes ago, Relativistic said:

You would think so. The Hadley cell's got to be bigger than it was 30 years ago.

Sources suggest that the rate of expansion has been around 0.1 degrees to 0.5 degrees of latitude northward per decade. Using the rough 60 miles per degree, then we can say that the Hadley cell is somewhere between 18 and 90 miles further north on average than it was 30 years ago. However, it has also strengthened, so the impact is probably larger than that suggests. IPCC says it is likely that the Hadley Cell has widened since the 1980s, but has only moderate confidence in the extent.

Here's the accompanying chart from AR6:

And the full explanation / discussion is on pages 49 to 51 of the PDF here:

https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter02.pdf

[Catacol]

23 minutes ago, Don said:

I've been thinking (and I'm sure others have too) that had this winter occurred 20 or 30 years ago, it would likely have been a straight forward cold season, with the pesky Iberian heights being less of an issue?

Hard to be certain…but one of the artefacts of CC is the northerly shunt of the sub tropical high pressure belt. When we combine this with a generally stronger stratospheric polar vortex (another consequence of CC caused by a cooling stratosphere) we have a more difficult envelope for high latitude ridges in winter. Pressure from the north in terms of the vortex and from the south in terms of a more obvious and intrusive Azores/Euro High suggests to me that we get less cold blocking and tropospheric forcing from the pacific is less reliable and dominant in shaping patterns. This is why I continue to think that we need the removal of one of these factors in order to achieve cold…and there is little sign of the Hadley Cell retreating….so that leaves the vortex. I have a totally unevidenced sense that CC might provide more frequent setups for SSWs to occur though we will need a much longer tale of the tape to be sure. So…in winters without a SSW we are really up against it to see a properly cold spell but when we get a SSW we are in the game…though admittedly an SSW is not a guarantee of anything and the 2018 style setup is unlikely to become common.

Our grandchildren may reflect on a U.K. context which sees properly cold spells in winter becoming a 1 in 10 year event. Sadly I’m not sure the direction of travel suggests anything other than this. I grew up in the 80s when cold spells were common. Those days - until something significant changes in the climate - are gone for now.

[sundog]

Jan 1958 such a big turn around in only 4 days. Imagine that happening nowadays.

From high pressure centred to our southwest to bang full on northerly.  While there still can be turn arounds of course they don't seem to be as often or as quick as before . 

[Big Gally]

That’s quite a significant drop in temperatures from this morning. The 27th up here showed around 8 Celsius. Now it’s showing 2 Celsius at 1pm. Hopefully tomorrow run start heading into the minus. Wishful thinking.

[Cambrian]

This comes up a lot in the winter and draws excellent discussion, but the reflections surrounding the Hadley Cell often occur as a reaction to a specific phase of “Hadleyesque” heights, an oscillating signature of which the waxing phase has to be progressed through, before we often quite swiftly get to a pattern where the last thing anyone is thinking about is anything close to what concerned George Hadley in 1735. 

If we take the 18z GEFS at day 5, and compare it with the classic Hadley signature, Azores and eastern Med heights, we have a culprit. Shoot the Hadley. 

 

But look at the north-south alignment of the Greenland and Atlantic lows, and the forcing heights through eastern Canada, ready to progress that wall of low heights east into Europe.

By day 10, the trough moves east and south, a cold trough with low heights through the Norwegian Sea, UK, Ireland and North Sea down through the continent to Algeria.

Irony is of course that the telltale elements are still there, Azores and eastern Med heights, just we’re not thinking about them any more because they have waned and because we’re on the cold side of a sumptuous looking trough that could well bed down as a Euro-low by day 14, a notion reinforced by a look at tonight’s EC46, and the NAO- signal for the first week of January. 

 

Are we thinking Hadley and its associated roaring NAO+?

Yeah, exactly, not at all, more Hadbeenley than Hadley, and as is so often the case after a milder Christmas, the winter resumes. 

[Kentspur]

Wow best I've seen yet more ensembles going further down on both GFS and CFS! Getting increasingly confident in a significant SSW!

[Lukesluckybunch]

1 hour ago, Kentspur said:

Wow best I've seen yet more ensembles going further down on both GFS and CFS! Getting increasingly confident in a significant SSW!

But as I've heard before a ssw doesn't always mean cold in the uk..it's a break up of the vortex isn't it?it depends where the two decide to go

[Kentspur]

54 minutes ago, Lukesluckybunch said:

But as I've heard before a ssw doesn't always mean cold in the uk..it's a break up of the vortex isn't it?it depends where the two decide to go

Common knowledge on here mate on average its a 2/3 chance so the Met have mentioned in the past just gotta hope it falls right for us and we don't end up too far east or west of any high lat blocking set ups

[Mucka]

UKMO staying with the possibility of some wintriness for Scotland and high ground for England but possibly a little sleet/snow for NE England.

 

GFS still has the low much further N and the difference with UKMO by 168 is fairly stark.

GEM is closer to the UKMO solution , ICON somewhere in the middle.

GFS Op doesn't offer much hope TBH, relentlessly wet and windy and the only remotely interesting thing on it is the strat warming.

 

GFS p25 is a very unlikely outlier sending the low into Spain/France, can't see ECM following that unfortunately.

[nick sussex]

The UKMO sticking with its low tracking ese with a chance of some snow on the northern flank for mainly higher ground .

The models have the same overall pattern but the detail for the UK is being complicated by the handling of shortwaves to the north and west .

Not sure I’d put too much faith in any solution at present. 

There’s a steep acceleration in zonal winds then a big drop and of course if there is a SSW previous history suggests the models make a drama until the reversal has happened and that’s in the actual starting conditions.

[carinthian]

On 21/12/2023 at 05:24, carinthian said:

Morning all. UKMO still have that troublesome Low in their extended model. A slightly slower movement this run but with a more southerly correction. Again , some sort of backing from the more aggressive GEM  this morning. No backing from GFS  at the moment. No sure where ECM will head ? . Quite a large snowfall across the Northern Pennines and Lakes District mountains based on that chart below  with freezing contours as low as 250m in parts of Northern England. Trouble brewing ?

C

Morning all. UKMO still ploughs on with its post Christmas Low across the North of England. Chart below indicates a couple of cold nights to follow. -10c at 18z  across the snow fields of the Southern Pennines  ! Um ? Hope their run stays the course as I am soon due over in Skipton for Christmas and then onto Stockholm for New Year ( hate mild and rain ) Not very nice on GFS showing quite a lot of rain and less cold towards the New Year. There can only be one outcome !!

C

[That ECM]

T144. Struggling to work that out.  Wedges are hard to model.

 

Edited December 22, 2023 by That ECM