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Model output discussion - proper cold spell inbound?


Paul

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Posted
  • Location: Rotherhithe, 5.8M ASL
  • Location: Rotherhithe, 5.8M ASL
4 minutes ago, pureasthedriven said:

Not necessarily though, depending on where those low heights set up? Some flabby Iberian affair and we could easy end up getting warmer air in the mix fed westwards. 

Any to the south / south east will do much more good than harm. I guess we would be severely prohibited from achieving CAA with that cold air advection without low heights it ain’t going to happen. Think of it like stating blades instead of being on ice you’re on granite low heights are very important to have or it will collapse quickly and it will be dry cold which doesn’t really appeal to most on here. 

Edited by Daniel*
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Posted
  • Location: Cardiff/Reading Uni
  • Weather Preferences: Snow, Sun, Heat, Cold,T/storms via Spanish plumes *rare*
  • Location: Cardiff/Reading Uni

Does anyone know the handling of the coupling between the stratosphere and the troposphere in the models? 

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Posted
  • Location: North Norfolk, Antingham
  • Weather Preferences: Most except high humidity and thawing snow.
  • Location: North Norfolk, Antingham

I am offering a simple and not very scientific analogy as to the conundrum faced by the models in working out where we go from here. Run a hot bath add cold water and mix. Burnt fingers, hidden hot spots just when you think it safe. How can models address that on a global scale. Give them a chance? Fiw I have a feeling that the high will migrate to Scandinavia SSW or not. ?

Edited by Weathervane
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Posted
  • Location: Evesham/ Tewkesbury
  • Weather Preferences: Enjoy the weather, you can't take it with you 😎
  • Location: Evesham/ Tewkesbury

Evening All and I sincerely hope you have had a great weekend and enjoyed your weather:cold:  To much emphasis on the SSW as far as Im concerned and a lot more factors need to come togeather in the Jigsaw before we can go anywhere with deep cold from the East, To much intense cold over Hudson bay, as models predict in the next ten days releasing a very strong jet stream ,halting our build of high pressure across Scandinavia . I might be wrong , I might be right,  but late March and April spells winds from the East , Stats for the Uk go to prove this evolution ,  I predict the same weather which we have had in the last few months to carry on for a little while yet....Watch this Space! :hi:

SSW.png

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i2OHZE9.gif

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Posted
  • Location: Horley, near Gatwick
  • Location: Horley, near Gatwick
6 minutes ago, Daniel* said:

Any to the south / south east will do much more good than harm. I guess we would be severely prohibited from achieving CAA with that cold air advection without low heights it ain’t going to happen. Think of it like stating blades instead of being on ice you’re on granite low heights are very important to have or it will collapse quickly and it will be dry cold which doesn’t really appeal to most on here. 

Yes, agreed. As always, another cog that needs to land perfectly. I’d rather have a Bartlett this time of year than a chilly dry SE’ly! 

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

Patience guys, all is not lost!..still some beautiful Gefs 12z charts being churned out for late feb..the period of most interest!!:shok::cold:

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Edited by Frosty.
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Posted
  • Location: Hertfordshire
  • Weather Preferences: SNOW AND FREEZING TEMPS
  • Location: Hertfordshire

Well the BBC long range forecast not going with the later stages of the ECM . There saying a continued flow from the North west by next weekend and beyond and quite cold . Witch is nothing like these crappy charts .

EDIT - what I'm trying to say is the GFS has easterlies the ecm has Westlys and the BBC has north Westlys . Talk about uncertainties ?

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Edited by ICE COLD
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Posted
  • Location: Frankley, Birmingham 250masl
  • Weather Preferences: the weather extremes in general but my favourites are snow & thunderstorms
  • Location: Frankley, Birmingham 250masl

I’m thinking that when this ssw really gets going there might all of a sudden be a flip in the models where they all come together, whether that aligns right for the uk is a different matter. I suppose time will tell

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Posted
  • Location: West Sussex
  • Weather Preferences: Extreme cold & snow
  • Location: West Sussex
15 minutes ago, Panayiotis said:

Does anyone know the handling of the coupling between the stratosphere and the troposphere in the models? 

The way changes in the stratosphere work their way down into the troposphere isn't that well understood

For most on here (coldies) a SSW facilitates a series of very complicated events which raise the odds considerably of a decent cold spell - but don;t guarantee it of course.

To get 'real cold' (assuming we want sustained very cold air) you need blocking and the jetstream to be deflected. That is precisely what a SSW achieves by reversing the wind direction in the stratosphere and disturbing the jetstream below.

As for the model output, we should avoid keep over-reacting to one or more operational runs. The atmosphere around our latitude is a particularly active region and incredibly difficult to model accurately at the best of times. When you have potential impacts from the stratosphere it adds another layer of uncertainty, especially as these are infrequent events.

:)

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Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire
28 minutes ago, Panayiotis said:

Does anyone know the handling of the coupling between the stratosphere and the troposphere in the models? 

In while..will format them.

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Posted
  • Location: Weymouth, Dorset
  • Location: Weymouth, Dorset
29 minutes ago, lorenzo said:

In benign times the Berlin 150 can give a look at the further ECM thoughts.. right now, needs used in tandem with higher levels to view downwelling

http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ec.php?alert=1&level=150&forecast=all&lng=eng

 

Also interesting to see how the 19th changed from one day to the next at the low strat level..

0547BE3A-2DCC-4B40-B25F-0DE0C0282B9D.thumb.gif.1665d41111f39ffeb62540e97400ae23.gif

7841C158-2A36-4F06-9E6F-55B4EE6CAF1F.thumb.gif.48e3a7bce442f651aa039317a5949266.gif

 

Much better looking profile on yesterday’s day 10 compared to today’s day 9. There is some hope with that ridge I suppose.

 

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Posted
  • Location: @scotlandwx
  • Weather Preferences: Crystal Clear High Pressure & Blue Skies
  • Location: @scotlandwx

MJO input ends tomorrow. Dr Lopex with some good intel .. it#s the strat that's in control, 240  next staging post..

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Posted
  • Location: st albans
  • Location: st albans

A view of the three ens for day 15 reveals strong agreement on decent blocking for nw Europe - gefs not actually quite as high a latitude with the mean surface high as the geps and ecm 

EFF1F9BC-B9E3-4DE7-8B06-A922506C1BA0.thumb.jpeg.77e293cd750c266fda331816e3f5bb0f.jpeg 397F4BA2-27E6-473F-85ED-585A6B2C3455.thumb.jpeg.7d0eda59155ce3eb7213e373d136deb1.jpeg46CC6E36-072C-479E-A6DE-355B5A7D76C4.thumb.jpeg.665c0f19c798cb55867eb70f73e1d5b5.jpeg

 

As ed posted earlier, all roads lead to here. Given the time of year, plenty hope we find a quicker route .......

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Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire

Pacific ridge and russian warming is now in momentum phase!

So impactual ssw-will have differ- on trop/-lag effects...

18z can apply...progs!??

Edited by tight isobar
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Posted
  • Location: Methil, Fife
  • Weather Preferences: Baltic
  • Location: Methil, Fife
12 minutes ago, lorenzo said:

MJO input ends tomorrow. Dr Lopex with some good intel .. it#s the strat that's in control, 240  next staging post..

Thats either telling me that the downwelling is strong enough to counter any GFS MJO predicted phase 7 mid level amplitude input or the MJO is moving into 8 / 1 COD (most other models) , would have no effect regardless? Or am I picking this up all wrong?

 

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Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire
9 minutes ago, ghoneym said:

Thats either telling me that the downwelling is strong enough to counter any GFS MJO predicted phase 7 mid level amplitude input or the MJO is moving into 8 / 1 COD (most other models) , would have no effect regardless? Or am I picking this up all wrong?

 

Depends on synoptic format of phases!.

There is minamal lag-7/8 heading to 1 on table!???

Ops will not as yet refer to that stage!!

Ecmwf-..forwarding process is in diss-agree(crosd modeling)..operational confuse!-miss-diagnostics-further non diffuse!!...

Lag-effect down welling- consider!

ECMF_phase_51m_full (1).gif

Edited by tight isobar
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Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire

Dont usually like gfs synops-with strato- decipher!!!

However!..

The warm-is coming into phase of now.

As the ssw is clearly underway!!..

And the bird (pv main)..continues to fall off its perch.

Still looking good for tranfer of main lobe-steel- of colder infer...as both are imbedded with warming.

gfsnh-10-66.png

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Posted
  • Location: Nr Chelmsford, Essex
  • Weather Preferences: Hurricanes, Thunderstorms and blizzards please!
  • Location: Nr Chelmsford, Essex
1 hour ago, Daniel* said:

Maybe too many of us are expecting a QTR however it is a record breaking reversal for the time of year and it seems to sustain this reversal for quite some time, which is additionally impressive. I’m a bit baffled by ECM as to me it looks like there is very little imprint from this event, if this was a normal SSW I’d somewhat get it.

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Mirrors my thoughts exactly.  Whilst I accept this SSW won't necessarily deliver for the UK or even NW Europe, given the strength of the warming along with significant wind reversals, I can't believe we won't see some crazy NH profiles being shown.  For that reason, I don't believe the models have got a proper handle on this yet.

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my distain for the ECM grows larger every day-   

As much as it pains me to say this - The ECMs form in the run up to cold spells ( for the most part ) has been woeful, with the UKMO beating it easily on the last one & the GFS in the mains better over Dec / Jan 

Decent 18z coming - ridging already better-

BBF1DF43-01AC-4628-BB29-B0DB0E5A8539.thumb.png.a578f2d05eaae3d1bcfa9c8de639ccc1.png

S

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10 minutes ago, Tamara said:

You are quite right:) As was Captain Shortwave observation at the same time about the amplification in the Pacific sector.

And that remains the clue, despite suspending usual thought yesterday for good reason:D. We can all think we are missing something when there are extraordinary things happening at all levels of the atmosphere.

But seeing as I have returned to my head attempting to be in control over what is happening, then as previously suspected - its the case that falling angular momentum since the MJO induced Scandinavian ridge of last week, is meaning that -ve zonal easterly winds are lining up again along the tropics at 30N

gfs1.png

 As repeated a bit like a stuck record by me this season (sorry about that but its based on intended good reasoning) the effect of a return to more La Nina-like type forcing (for the time-being)is to  re-boot the sub tropical ridges aligning along 30N.  The classic configuration of this forcing this winter has built up the signature traditional default pattern of amplified North Pacific ridge which locks in the Canadian vortex, with increased polar jet energy and further sub tropical ridging downstream pushed to mid latitudes across Bermuda and to the Azores ridge.  The -ve zonal wind anomalies supporting these ridges underneath, with the polar jet flow across the top.

Very much a +NAO regime.

However much members dislike it, that is what the ECM operational keeps modelling each time at the moment into the medium term, and its not hard to see where it is coming from - based on its interpretation of the recent very high amplitude tropical forcing concluding its cycle - and with those -ve zonal winds returning across the 30N as angular momentum falls back ...ahead of the next tropical cycle retuning to the Indian Ocean.

If one thinks that the deep amplitude low angular momentum GWO pattern of January helped cement the Canadian vortex at a time when the polar field is typically at its most organised, then as suggested in posts at various times through January (and in anticipation of the latest MJO forcing) it was always going to be a big ask (initially) to change an entrenched tropospheric base state pattern - which in turn frameworks the polar field.

I think a weak El Nino forcing, in tandem with eQBO would have created the stratospheric pathway that does not favour amplification restricted upstream in the Pacific and does not teleconnect to a strong Canadian vortex lasting in latter winter and being more resistant to any poleward wave flux that does come from phases of tropical momentum 

Under a feedback pattern that produces steady background poleward +AAM forcing, and unlike a La Nina regime not relying wholly on tropical convection forcing to boost westerly winds in the tropics as a means to amplifying the extra tropics downstream  (the Atlantic and European sector) then this SSW would have taken route 1 - as last weeks +AAM spike produced in terms of the Scandinavian ridge and less upstream energy waiting to return c/o the Canadian vortex.

.The SSW would be more likely dealing in those circumstances with a sibling Canadian vortex and parental Siberian lobe - rather than the other way around as we see at the moment, and as very well described by @lorenzo on the stratosphere thread today

Its a case in my opinion of the tropical cycle re-setting from the Indian Ocean and angular momentum rising once again. Also I think that March will see the Pacific profile change and warmer sub waters changing to mean that a more sustained +AAM cycle will evolve as a signal that this La Nina is going to fade though the Spring into early summer.

So an extension of 'winter' and a cold March does look intuitive on that basis at this stage

Before then, however and notwithstanding all said in intended sense as above - its still very much the case to watch this bag of tricks called the SSW . As soon as the parent Canadian vortex shows weakening and the models factor in better the constantly new starting conditions based on the Krakatoa evolving from the highest levels of the atmosphere downwards, then the stubborn tropospheric pattern c/o (weakening) low angular momentum forcing should become less dominant and more easily overridden -  especially as wavelengths shorten and assist cold air advection heading into March

 

Can I just say quite blatent - the SSW will wipe the la nina base state off the map. It wont matter if theres a pacific ridge when theres downstream ridging blocking the canadian vortex.

Anyway - Have a good night all*

Edited by Steve Murr
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Posted
  • Location: Hull
  • Weather Preferences: Cold Snowy Winters, Hot Thundery Summers
  • Location: Hull

With this cheeky low pressure system just to the South I really can't see this going the same way as the ECM.

image.thumb.png.9a41628d64d8315dd3b96d45471a73ce.png

The low pressure should stop high pressure over the UK sinking south and eventually allow a block to build. Here's hoping :rofl:

Edited by Quicksilver1989
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Posted
  • Location: @scotlandwx
  • Weather Preferences: Crystal Clear High Pressure & Blue Skies
  • Location: @scotlandwx
3 minutes ago, Steve Murr said:

Can I just say quite blatent - the SSW will wipe the la nina base state off the map. It wont matter if theres a pacific ridge when there downstream ridging blocking the canadian vortex.

think the mjo has had a hand here too Steve, Pacific base state has had it's time called. Already musing ahead wQBO rising Solar, weak el nino...

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