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Gandalf The White
29 December 2022 00:41:22

Maybe in response to this SSW? - Seems to be a persistent theme now toward the end of the runs where by temps @ 10hpa rise significantly after the 1st week of January: - Here's for hoping anyway?! 🤞

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Originally Posted by: tallyho_83 





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.

 
Location: South Cambridgeshire
130 metres ASL
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DEW
  • DEW
  • Advanced Member
29 December 2022 08:03:49
The WX temp charts are anything but stable. This morning's version has the ultra cold area in Siberia restored in week 1, and while Europe remains above average for that week, cold spreads well south to the Black Sea in week 2 as well as the rest of W Europe cooling down though to a lesser extent. Pptn more consistent, continuing in Atlantic coastal countries incl Britain, with some extension to the Baltic, and in week 2 down through France and onward to the Adriatic.

GFS Op - default W-lies but with interruptions, and not penetrating so far into Europe as shown yesterday. The interruptions may be based on LP coming down from the NW with cold N-ly spells (Sun 1st, 995mb Scotland weakly, Tue 10th 985mb E Scotland strongly) or HP developing from the S with mild SW-lies (Thu 5th 1040mb Spain-Norway, Sat 14th ditto)

ECM - similar to GFS in general pattern and specifically for Sun 1st (though LP centred over England) and Thu 5th (though ridge placed further E). This model then develops a very large LP centred 950mb SE Iceland which dictates the weather all the way down to the Alps

GEFS - temps up and down to match the above until Sat 7th (this variation most marked in S, the N having a flatter and cooler profile) after which little agreement between ens members, with a final spread on Sat 14th from 10C below to 8C above norm. Rain in one or other ens member from time to time, most probable around 1st and 8th, heaviest in W and lttle prospect of snow exc in far N.
War does not determine who is right, only who is left - Bertrand Russell

Chichester 12m asl
+1
Brian Gaze
29 December 2022 08:25:14
Looks like a "choppy" zonal flow to me rather than a very flat one. The sine wave pattern is clear for the next week or so and beyond that it could simply be that the individual runs are bringing disturbances through at different times so the mean is being smoothed.

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Brian Gaze
Berkhamsted
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Brian Gaze
29 December 2022 08:29:44
Also there are 23/31 runs dipping below -5C and only 3/31 going below -10C. Very similar to recent days and IMO no real sign of a significant cold period at the moment. 


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Brian Gaze
Berkhamsted
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UncleAlbert
29 December 2022 09:03:08

Looks like a "choppy" zonal flow to me rather than a very flat one. The sine wave pattern is clear for the next week or so and beyond that it could simply be that the individual runs are bringing disturbances through at different times so the mean is being smoothed.

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Originally Posted by: Brian Gaze 



Except to my eye, the lower plots in the later part of the run are the more stable ones, so in that way some sort of split?
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+1
The Beast from the East
29 December 2022 09:35:34

Also there are 23/31 runs dipping below -5C and only 3/31 going below -10C. Very similar to recent days and IMO no real sign of a significant cold period at the moment. 


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Originally Posted by: Brian Gaze 



Pitiful. Just roll on spring and those warm sunny days. Hopefully a long fetch bartlett can set up at least for the south and we can keep those heating bills down
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doctormog
29 December 2022 09:38:08
Meanwhile up here it looks like it will remain on the chilly side in the coming days then a potential warm up to something milder for a couple of days then more average or below again beyond that. The latter (cooler) part has changed over the last day or so should be viewed with a lot of caution. 

https://modeles16.meteociel.fr/modeles/gensp/graphe_ens3.phpclim=1&x=&y=&ext=1&run=0&lat=57.2&lon=-2.25&runpara=0 

Overall though the pervading theme is unsettled. 
Aberdeen
Current conditions (personal WS) 
ballamar
29 December 2022 10:14:15
Scandi high at 150h on GFS op, nothing to get excited about though!
fairweather
29 December 2022 10:37:43

Except to my eye, the lower plots in the later part of the run are the more stable ones, so in that way some sort of split?

Originally Posted by: UncleAlbert 


​​​​​​​Sorry, could you explain  this to me. I don't understand what is more "stable" about the lower ones?
S.Essex, 42m ASL
UncleAlbert
29 December 2022 14:40:58

Sorry, could you explain  this to me. I don't understand what is more "stable" about the lower ones?

Originally Posted by: fairweather 



On the 850mb 0000hrs GFS ensembly around 6 of the members at around -5C or lower stayed at around that value for quite a few days rather than exhibiting the fluctuations we see from the passage of frequent troughs, possibly suggesting  the chance of a somewhat different pattern emerging, all be it near to the end of the run.  Of course this  has totally vanished on the latest run!
Hungry Tiger
29 December 2022 14:42:48

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.


Originally Posted by: Brian Gaze 



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


 
Gavin S. FRmetS.
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South Cambridgeshire. 93 metres or 302.25 feet ASL.


tallyho_83
29 December 2022 15:19:31

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.

 

Originally Posted by: Gandalf The White 



Yes but it is a precursor and a good sign for a beginning of a SSW? Agree?
Home Location - Kellands Lane, Okehampton, Devon (200m ASL)
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Gandalf The White
29 December 2022 18:08:46

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

Originally Posted by: tallyho_83 



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.
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


+6
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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Brian Gaze
Berkhamsted
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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.

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Jacee, Hucknall (Notts) 😽 x
+3
Jive Buddy
29 December 2022 23:53:31

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

Originally Posted by: Jacee 


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 👍😎
 
It's not over, until the fat Scandy sinks.....

Location: St. Mary Cray, S.E. London border with Kent.
+5
Caz
  • Caz
  • Advanced Member
30 December 2022 06:09:31

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 👍😎
 

Originally Posted by: Jive Buddy 

Completely agree with you JB.  Love Jaycee’s ‘no personal agenda’ posts.  👍
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+2
TheJudge
30 December 2022 06:47:35

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

Originally Posted by: Caz 



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.
+3
DEW
  • DEW
  • Advanced Member
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
War does not determine who is right, only who is left - Bertrand Russell

Chichester 12m asl
+2
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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Brian Gaze
Berkhamsted
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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

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!

Originally Posted by: ballamar 



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!

 
Jacee, Hucknall (Notts) 😽 x
+4
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

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!

Originally Posted by: ballamar 


And again at 360 hours, almost but not quite. Maybe third time lucky!
Yateley, NE Hampshire, 73m asl
"But who wants to be foretold the weather? It is bad enough when it comes, without our having the misery of knowing about it beforehand." — Jerome K. Jerome
+1
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