Hungry Tiger
29 December 2022 14:42:48
Originally Posted by: Brian Gaze 

An odd cold run has been appearing in recent ECM and GEFS updates but they are still few and far between, at least for the south.

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GEFS35 possibly picking something up during the second half of January.




A very common time for a cold spell. The old term - The days lengthen the cold strengthen.


 
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tallyho_83
29 December 2022 15:19:31
Originally Posted by: Gandalf The White 

Although it looks quite impressive, that isn't a SSW: it's neither 'sudden' nor has sufficient warming.  To propagate down into the troposphere and influence weather systems there needs to be a sudden 'jolt' exerting downwards pressure. There also needs to be a wind reversal and that's not appearing in the forecast charts.

 



Yes but it is a precursor and a good sign for a beginning of a SSW? Agree?
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Gandalf The White
29 December 2022 18:08:46
Originally Posted by: tallyho_83 

Yes but it is a precursor and a good sign for a beginning of a SSW? Agree?



Actually, I'm afraid I don't agree. What we're seeing across Arctic Russia is what we see every winter: modest increases in temperature which ebb and flow, often moving west to east.

The subject of the behaviour of the stratosphere is way above my pay grade but I don't think there's any correlation between what we are seeing and possible SSW events.

Of course, even a notable SSW doesn't guarantee propogation down into the troposphere, let alone guaranteeing blocking in the right place.
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Brian Gaze
29 December 2022 18:39:58
I had to do a double take on the chart below to make sure it was the mean and not one of the perturbations. IME it's unusual to see the mean showing such a tight pressure gradient at t+240 hours. 

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Jacee
29 December 2022 21:52:31
There is definitely some interest after the first week of January, if it is cold you are searching for. Looking at the GEFS, there is a cluster of runs for London that are between -5 to -10C 850hPa by week two with the snow row numbers responding in kind.

Given the pressure anomalies for Oslo at the same time are not indicative of a Scandi high, it seems the GFS would prefer to bring in cold from the north or northwest with our trough moving east and high pressure building northwards in the mid-Atlantic which is how the 12z operational brings in a brief colder snap deep into FI.

I haven't had a chance to look at the individual ensemble members that bring in the cold, but at a glance it seems the cold would be brought in a similar fashion with a lack of sustained cold shown currently. Feeding on scraps, I think you'd call it.

UserPostedImage


UserPostedImage
 
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Jive Buddy
29 December 2022 23:53:31
Originally Posted by: Jacee 

snip.... another very eloquent and interesting post...


While it's quiet on here, can I just say welcome to a breath of fresh air on this forum. Jaycee, I don't recognise your posting style, so I'm assuming you're fairly new to TWO - apologies if you're not. From what I've seen from you so far, I think you're fast becoming one of the few "must read" posters we have. A huge thumbs up from me 👍😎
 
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Caz
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30 December 2022 06:09:31
Originally Posted by: Jive Buddy 

While it's quiet on here, can I just say welcome to a breath of fresh air on this forum. Jaycee, I don't recognise your posting style, so I'm assuming you're fairly new to TWO - apologies if you're not. From what I've seen from you so far, I think you're fast becoming one of the few "must read" posters we have. A huge thumbs up from me 👍😎
 

Completely agree with you JB.  Love Jaycee’s ‘no personal agenda’ posts.  👍
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TheJudge
30 December 2022 06:47:35
Originally Posted by: Caz 

Completely agree with you JB.  Love Jaycee’s ‘no personal agenda’ posts.  👍



I have to agree. Nice to read fair posts that analyse the output, without an agenda. Furthermore, backed up by providing the evidence of the interpretation of the models with images and links. Thank you Jaycee, long may you continue to post.
DEW
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30 December 2022 07:48:52
WX temp charts continue to favour a very cold north - week 1, a large area N of the Urals, week 2 spreading acrosss to N Scandinavia - but is uncertain as to how far south the cold will reach. In week 1 there is a steep temp gradient to a mild W Europe, but colder air in week 2 does not reach so far S as shown yesterday. The 0C isotherm does reach Poland and mountain areas further W, and W Europe is cool, but Ukraine and around the Black Sea not so much in the chiller as previously shown.

GFS Op has a W-ly theme to start, with the LP slowly shifting N-wards from generating the current heavy rain to a drier spell towards Thu 5th. Then the W-lies get broken up by LPs dipping from N of Scotland into the N Sea dragging N-lies behind them (990mb Denmark Fri 6th, and more extensively 985mb Thu 12th). The final frame Sun 15th has the very deep depression 950mb S of Iceland which was in that position yesterday but only affecting the Atlantic as higher pressure begins to link the Azores to Norway, each 1030mb with Britain under a col.

ECM resembles GFS to Fri 6th, but then the following LP instead of waiting to the N for a few days takes the direct route SE-wards 980mb Scotland Sun 8th with NW-lies for the rest of Britain

GEFS has no really strong signal; temps rise and fall for a while, especially in the S, and likely to become cooler later on away from the SW. Some rain in most ens members from time to time, heaviest in the W
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ballamar
30 December 2022 08:10:38
Hints of a change in the NH pattern in 9-10 days which could start showing some decent cold Synoptics but as always huge caveat with strength and direction of the jet
Brian Gaze
30 December 2022 08:20:24
Still looks like the sine wave is rolling over the horizon. With that said, it does look more like a traditional zonal flow rather than one displaced slightly further north which has been the trend in recent decades. 

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ballamar
30 December 2022 10:16:23
The charts at 150 on GFS are the almost easterly charts which look like they could get there until that pulse of jet stream takes away hope!
Jacee
30 December 2022 10:35:18
Originally Posted by: ballamar 

The charts at 150 on GFS are the almost easterly charts which look like they could get there until that pulse of jet stream takes away hope!



The holy grail would be an easterly of some sort but it would be a long and fraught road to get there currently. You are right though, that day 7 chart is a bit of a tease.

Going from the morning output, it still looks like we'd have to look to the northwest as we head to week two of January as we see heights squeezed south in Europe and a colder PM flow attempt to establish as the jet realigns. Admittedly not inspiring if you're further south but such a setup would lead to incresed snow chances further north and potentially open the door to a northerly down the line if we get the required amplification (still a big if!).

ps, thanks for the kind words on the previous page 😊 I had wanted to join for a long time and it was a wonderful surprise to see registrations open!

 
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ballamar
30 December 2022 11:12:11
Decent enough Scandi high at the end of GFS op run, hoping for this to become more of a theme in subsequent output
Rob K
30 December 2022 11:12:48
Originally Posted by: ballamar 

The charts at 150 on GFS are the almost easterly charts which look like they could get there until that pulse of jet stream takes away hope!


And again at 360 hours, almost but not quite. Maybe third time lucky!
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shepherd
30 December 2022 19:50:17
Now it's wet and windy for the foreseeable, lots of cold rain but then it's January.
Jacee
30 December 2022 20:22:03
In the near term it is indeed looking like a continuation of unsettled weather with any wintriness reserved for the mountains of Scotland as we see a trough-ridge-trough pattern. As always in such a setup, the north and west cop the worst of the rainfall totals.

UserPostedImage

There seems to be a semi-permanent low pressure somewhere in between Iceland and Scotland and that theme continues into the medium term with polar maritime air perhaps more prominent as the lows potentially take a more NW-SE track. This is how we may introduce a greater wintry risk for favoured hills rather than just the ski resorts.

UserPostedImage

Now, there is a lot of cold air bottled up to the NE and it is encouraging to see less extreme cold heading into the States. However hard I want to cling to the hope of a Scandinavian high to eventualy unlock that deep cold to the east, I am struggling to see anything meaningful in what remains charts deep in FI. Previous GFS operationals for instance have not been well supported in the ensemble suites. I note the 06z which was a high pressure outlier for Oslo in its latter stages for instance.

UserPostedImage

So my main thoughts, if you're still clinging to something colder and more widespread happening, the most likely period for that remains mid-January but perhaps not from anything to the east/northeast. It is more likely, given (admittedly low amplitude) the MJO forecast that we see heights over SW Europe decline westwards and aid some modest amplification in the Atlantic which would help the jet buckle SE and steer the ever-present Icelandic low(s) deeper into Europe and drag colder PM (but not deep cold) air to our shores.

Before any of that tenuousness I suppose the succinct line from Shepherd above sums up the reliable. Wet and windy with cold rain ☺


 
Jacee, Hucknall (Notts) 😽 x
Joe Bloggs
30 December 2022 20:55:20
Originally Posted by: Jacee 

In the near term it is indeed looking like a continuation of unsettled weather with any wintriness reserved for the mountains of Scotland as we see a trough-ridge-trough pattern. As always in such a setup, the north and west cop the worst of the rainfall totals.

UserPostedImage

There seems to be a semi-permanent low pressure somewhere in between Iceland and Scotland and that theme continues into the medium term with polar maritime air perhaps more prominent as the lows potentially take a more NW-SE track. This is how we may introduce a greater wintry risk for favoured hills rather than just the ski resorts.

UserPostedImage

Now, there is a lot of cold air bottled up to the NE and it is encouraging to see less extreme cold heading into the States. However hard I want to cling to the hope of a Scandinavian high to eventualy unlock that deep cold to the east, I am struggling to see anything meaningful in what remains charts deep in FI. Previous GFS operationals for instance have not been well supported in the ensemble suites. I note the 06z which was a high pressure outlier for Oslo in its latter stages for instance.

UserPostedImage

So my main thoughts, if you're still clinging to something colder and more widespread happening, the most likely period for that remains mid-January but perhaps not from anything to the east/northeast. It is more likely, given (admittedly low amplitude) the MJO forecast that we see heights over SW Europe decline westwards and aid some modest amplification in the Atlantic which would help the jet buckle SE and steer the ever-present Icelandic low(s) deeper into Europe and drag colder PM (but not deep cold) air to our shores.

Before any of that tenuousness I suppose the succinct line from Shepherd above sums up the reliable. Wet and windy with cold rain ☺


 



What an absolute stunner of a post. Great to have you posting. Welcome. 👍😊

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Jive Buddy
30 December 2022 22:36:38
Originally Posted by: Joe Bloggs 

What an absolute stunner. Great to have you posting. Welcome. 👍😊


Steady Joe, steady! .....😉🤪
It's not over, until the fat Scandy sinks.....

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Joe Bloggs
30 December 2022 22:41:50
Originally Posted by: Jive Buddy 

Steady Joe, steady! .....😉🤪



Sorry getting carried away…

Not that you’ve ever witnessed that before. 😂

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