Jump to content
Snow?
Local
Radar
Cold?
IGNORED

Model output discussion - proper cold spell inbound?


Paul

Recommended Posts

Posted
  • Location: Burton-on-Trent (90m), Larnaka most Augusts
  • Location: Burton-on-Trent (90m), Larnaka most Augusts

I'm still going for an initial ridge messily squeezing through. Both ECM and GFS are massively overestimating the strength of lows in the Iceland area imo. Zonal winds could have reversed on the 12z updates...

Link to comment
Share on other sites

Posted
  • Location: Burton-on-Trent (90m), Larnaka most Augusts
  • Location: Burton-on-Trent (90m), Larnaka most Augusts
8 minutes ago, Gael_Force said:

I think, in this instance, it's the split that is actually fortifying the Canadian segment. The separation is not ideal as it leaves the dominant chunk in a position to drive westerlies. I've looked through the animations of previous warmings but there are none I can see where the split is similar to this ... the good ones had the split up through Greenland ...and felled the vortex with first punch!

Look through the Berlin charts at 10hpa. The warming is moving the center of the lobe away from Greenland and into central/west Canada. By t96 Greenland is under the influence of the high pressure.

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html

 

Edited by Snowy L
Link to comment
Share on other sites

Posted
  • Location: West/East/Sussex Surrey border
  • Location: West/East/Sussex Surrey border
12 minutes ago, Gael_Force said:

I think, in this instance, it's the split that is actually fortifying the Canadian segment. The separation is not ideal as it leaves the dominant chunk in a position to drive westerlies. I've looked through the animations of previous warmings but there are none I can see where the split is similar to this ... the good ones had the split up through Greenland ...and felled the vortex with first punch!

https://twitter.com/_chrisfawkes/status/962364093737963522

Link to comment
Share on other sites

The SSW still hasn't fully occurred and the models are still trying to get a grasp on it. They've gone back and forth for a few days now. I really don't like the look of this morning's runs but we should stay patient. Whatever the models are showing by Wednesday, we can be fairly confident that that's what will happen I think. 

Link to comment
Share on other sites

Posted
  • Location: Peterborough
  • Weather Preferences: Snow and frost in the winter. Hot and sunny, thunderstorms in the summer.
  • Location: Peterborough

I think Lorenzo's post in the strat thread is worth a read, as to me it certainly offers an explanation on why we saw the strong signal for the UK to turn cold from around the 19th/20th and why this signal has somewhat vanished from the model output.

It seems that a few days ago we were getting a clean separation between the two lobes of the polar vortex throughout the layers of the stratosphere which pretty much gave a clean route for heights to build in the Atlantic and allow a flow from the east to develop as a result. The reality is that the two lobes don't stay separated for a long enough time with the Siberian lobe transferring to the stronger Canadian lobe which prevents the strong ridging in the Atlantic which allowed the quick route to cold. Someone may correct me on this though as I probably have misinterpreted something here.

I have linked the post below.

 

So what does this leave us with, well surely all imperical evidence would suggest that whilst heights remain low towards Greenland and Canada, surely the strength of the jet coming off the eastern seaboard should weaken and potentially pull back west in time which should allow heights to build northwards over Europe. Could this develop into a proper cold easterly over time remains uncertain but the extended outlook still favoured a continental feel to our weather though it looks more likely to be cold and frosty rather than snowy.

  • Like 4
Link to comment
Share on other sites

Posted
  • Location: Evesham/ Tewkesbury
  • Weather Preferences: Enjoy the weather, you can't take it with you 😎
  • Location: Evesham/ Tewkesbury
13 minutes ago, CreweCold said:

The issue is (and I saw this coming from a mile off), some people seem to believe a SSW guarantees cold and snow in the UK. It doesn't work this way. It's almost as if people have the snowy end game as a starting point and trying to work the modelling back from there. Bizarre. 

Good point, if the SSW was guarantee of cold and snow in the UK ,why is it so difficult to forecast in the days ahead? The answer put more simply is that it's far more complex than a SSW developing and reversing the tropospheric winds , there are many other factors to consider perhaps looking downstream a bit to North America to see how the polar vortex influences our jet stream:sorry:

Link to comment
Share on other sites

Posted
  • Location: Exile from Argyll
  • Location: Exile from Argyll
28 minutes ago, Snowy L said:

Look through the Berlin charts at 10hpa. The warming is moving the center of the lobe away from Greenland and into central/west Canada. By t96 Greenland is under the influence of the high pressure.

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html

 

I'm looking further afield at day 10: by then a displacement warming. I still reckon you need the dominant vortex to be on the eurasian side as that drives the northerly cold to us; it all looks too flabby out east.

 

Link to comment
Share on other sites

9 minutes ago, Captain Shortwave said:

I think Lorenzo's post in the strat thread is worth a read, as to me it certainly offers an explanation on why we saw the strong signal for the UK to turn cold from around the 19th/20th and why this signal has somewhat vanished from the model output.

It seems that a few days ago we were getting a clean separation between the two lobes of the polar vortex throughout the layers of the stratosphere which pretty much gave a clean route for heights to build in the Atlantic and allow a flow from the east to develop as a result. The reality is that the two lobes don't stay separated for a long enough time with the Siberian lobe transferring to the stronger Canadian lobe which prevents the strong ridging in the Atlantic which allowed the quick route to cold. Someone may correct me on this though as I probably have misinterpreted something here.

I have linked the post below.

 

So what does this leave us with, well surely all imperical evidence would suggest that whilst heights remain low towards Greenland and Canada, surely the strength of the jet coming off the eastern seaboard should weaken and potentially pull back west in time which should allow heights to build northwards over Europe. Could this develop into a proper cold easterly over time remains uncertain but the extended outlook still favoured a continental feel to our weather though it looks more likely to be cold and frosty rather than snowy.

Good post, people really should take a look at the link. Explains why models may be struggling here. 

  • Like 1
Link to comment
Share on other sites

Posted
  • Location: West Ipswich, Suffolk
  • Location: West Ipswich, Suffolk

Another thing that puzzles me is that i was of the understanding that given timings the mjo forcing and ssw effects were not going to happen in tandem (the ssw would have to have been around a week or so earlier) so i would have expected to have seen the effects of the mjo forcing in outputs before ssw. Therefore is it at all possible given as at the same time the Ecm flipped it also killed the mjo to the circle that we are seeing the effects of another mjo fail and not the ssw.

I couldn't imagine given the amazing amplitude of the mjo that even if there was no ssw it would have shown itself in outputs even if it did fail. It seems to be the consensus that what we were seeing in the outputs was the ssw.

Please excuse me if i sound stupid this is my first year at trying to understand the teleconnections and mjo and add them to my model knowledge:)TIA 

Link to comment
Share on other sites

Posted
  • Location: st albans
  • Location: st albans
24 minutes ago, Captain Shortwave said:

I think Lorenzo's post in the strat thread is worth a read, as to me it certainly offers an explanation on why we saw the strong signal for the UK to turn cold from around the 19th/20th and why this signal has somewhat vanished from the model output.

It seems that a few days ago we were getting a clean separation between the two lobes of the polar vortex throughout the layers of the stratosphere which pretty much gave a clean route for heights to build in the Atlantic and allow a flow from the east to develop as a result. The reality is that the two lobes don't stay separated for a long enough time with the Siberian lobe transferring to the stronger Canadian lobe which prevents the strong ridging in the Atlantic which allowed the quick route to cold. Someone may correct me on this though as I probably have misinterpreted something here.

I have linked the post below.

 

 

I made this point yesterday morning to @Singularity

 

  • Like 3
Link to comment
Share on other sites

Posted
  • Location: Carryduff, County Down 420ft ASL
  • Location: Carryduff, County Down 420ft ASL

The reality is the models have backed up a quick tropospheric response to provide decent favourable high latitude blocking for us, we therefore need to wait until early March.

Link to comment
Share on other sites

Posted
  • Location: manchester
  • Weather Preferences: Summer
  • Location: manchester
2 minutes ago, mountain shadow said:

The reality is the models have backed up a quick tropospheric response to provide decent favourable high latitude blocking for us, we therefore need to wait until early March.

You wont get much cold out of any blocking in March as the sun will be too strong  .

  • Like 1
Link to comment
Share on other sites

Posted
  • Location: Gillingham, Kent
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Gillingham, Kent
6 minutes ago, - 40*C said:

You wont get much cold out of any blocking in March as the sun will be too strong  .

Tell that to March 2013..

11 minutes ago, mountain shadow said:

The reality is the models have backed up a quick tropospheric response to provide decent favourable high latitude blocking for us, we therefore need to wait until early March.

Do we? I still think 19th-24th will be the transition to blocked, whether the cold reaches the UK is a different story. I see no reason why it'd take until early March.

Edited by Daniel Smith
  • Like 7
Link to comment
Share on other sites

Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .
14 minutes ago, Chris101 said:

Another thing that puzzles me is that i was of the understanding that given timings the mjo forcing and ssw effects were not going to happen in tandem (the ssw would have to have been around a week or so earlier) so i would have expected to have seen the effects of the mjo forcing in outputs before ssw. Therefore is it at all possible given as at the same time the Ecm flipped it also killed the mjo to the circle that we are seeing the effects of another mjo fail and not the ssw.

I couldn't imagine given the amazing amplitude of the mjo that even if there was no ssw it would have shown itself in outputs even if it did fail. It seems to be the consensus that what we were seeing in the outputs was the ssw.

Please excuse me if i sound stupid this is my first year at trying to understand the teleconnections and mjo and add them to my model knowledge:)TIA 

Good post .  There’s a time lag with the MJO so it’s unlikely the blocking failure would be in relation to that.

It could be more to do with the post by Lorenzo which explains things re the strat.

I would be shocked if there’s no impact on the NH pattern.  The impact is effected by the base state of the AO at the onset , so the size of the reversal added with the positive AO at the time should lead to a stronger downwelling into the trop .

KS also touches on the issue of blocking , it’s not like the blocking is in the wrong place there is no blocking shown at higher latitudes which suggests a longer wait .

I think we’ll know over the next few days, now that the SSW has occurred hopefully the way forward might become a bit clearer.

 

  • Like 3
  • Thanks 1
Link to comment
Share on other sites

Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)
34 minutes ago, bluearmy said:

I made this point yesterday morning to @Singularity

 

Indeed you did and well done for doing so :good:

It seeded my growing suspicion that the charts for later next week have been influenced more by the MJO projections than stratospheric developments.

This has now increased even further as I have compared the behaviour of the weaker vortex across the past 8 GFS runs with the tropospheric patterns and found that since the idea of a sustained split lasting for many days was lost, there's been little pattern in the pace of the rejoin with respect to how soon and strongly HLB establishes N/NE of the UK in the troposphere.

In other words, I'm led to conclude that a quick tropospheric response aligned to a split vortex pattern propagating down was lost from the output several days ago and so when looking at the period Thu-Sun next week, we've been chasing MJO-driven Scandinavian highs ever since.

 

This would allow for some more confident expectations for that period if it wasn't for the fact that the balance of power between that and the Canadian vortex segment is extremely uncertain given the combination of model disagreements on MJO behaviour and inherent difficulties handling tropospheric vortex strength when there is steady weakening taking place above it. 

It's not even certain that the weak vortex traversing NW. Eurasia will perform the merger soon enough to prevent the quick response to the SSW after all, though I am starting to see that as a long shot.

  • Like 6
Link to comment
Share on other sites

Posted
  • Location: st albans
  • Location: st albans

The flatter trop pattern is even more noticeable on the 00z strat ecm charts 

approaching the point where those who feel the models will begin to react to the reality of the reversal will see if they are to be proven right - interesting times indeed !

  • Like 2
Link to comment
Share on other sites

Posted
  • Location: Locksbottom, NW Kent 92m asl(310ft)
  • Weather Preferences: Warm summers but not too hot and colder winters with frost and snow
  • Location: Locksbottom, NW Kent 92m asl(310ft)

Love the passion of this thread in the search of snow and cold.GFS Friday night was the single most best winter run you could ever see but that seems an eternity away now.Models will only get to grips with SSW during the week and there will be back and forth swings from winter nirvana and pleasant spring warmth over next few days.I think this week will be a continuation of what this winter has been all about with some cold days with some snow about in NW britain and accumulating snow above 500ft asl and some wet days Midlands southwards.Temps 3-5 for Northern Britain and 5-9 for Midlands Southwards.After that from next weekends nobody can say with any great confidence but for cold and snow lovers(myself included) we still have a ticket for the raffle although i appreciate we are slowly running out of time.I will just sit back and enjoy this forum and what will be will be but Keep the faith snow lovers:good:

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

Posted
  • Location: Bournemouth
  • Weather Preferences: Dry mild or snow winter. Hot and humid summer.
  • Location: Bournemouth
12 minutes ago, karlos1983 said:

It’s so cryptic in here sometimes, I’m not sure if it’s because people just like to talk in riddles because it makes one sound clever, or so they can sit on the fence if they don’t spell it out! Odd! 

Short term, the GFS ups the anti on Tuesday’s possible snow event! 

FC09242A-F65B-47D1-9AD2-7E18159C7087.thumb.png.e5bc6e5b9d646fbb8b4ca60169409655.png

Ah the club within a club. Sometimes start a sentence with the words "surprised know ones mentioned" blah blah.

 

anyway, a step in the right direction by the gfs I would suggest. Ukmo at t144 is not without interest also.

IMG_0538.PNG

  • Like 2
  • Thanks 1
Link to comment
Share on other sites

Posted
  • Location: Tonbridge, Kent
  • Location: Tonbridge, Kent
Just now, mountain shadow said:

And?

And nothing yet, thanks for asking, but the evolution of the GFS may give a clue to how the UKMET might go, as they are very similar at 144.

 

  • Like 3
Link to comment
Share on other sites

Posted
  • Location: Brighton, East Sussex
  • Location: Brighton, East Sussex

GFS still going with the flatter ECM like scenario at 144, been a very disappointing day of modelling as the SSW approaches.

Edited by Weathizard
  • Like 1
Link to comment
Share on other sites

Posted
  • Location: Bournemouth
  • Weather Preferences: Dry mild or snow winter. Hot and humid summer.
  • Location: Bournemouth
1 minute ago, Weathizard said:

GFS still flatter at 144, been a very disappointing day of modelling as the SSW approaches.

I would disagree. 

IMG_0539.PNG

IMG_0540.PNG

  • Like 2
Link to comment
Share on other sites

Guest
This topic is now closed to further replies.
×
×
  • Create New...