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Model Output Discussion - Colder spell ending, what's to follow?


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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
    27 minutes ago, fellmike said:

    Whats happened to that high over russia ? Thought we were in for easterly this weekend

    The high over Russia has gone now, it was only ever going to deliver an easterly via promoting a SSW event and a lucky fall of the dice over the northern hemisphere.  That is off the table now.  

    82E60E4E-3CBA-4FD2-9B8D-A1075BD321E8.thumb.jpeg.b4212f8b7c1f34b8fda70b9a9b7e8edf.jpeg

    GFS pub run T270 shows what might be on the table if the Atlantic amplification coming from MJO forcing happens.  It might not though.  The table might look like this:

    575F682A-6805-428F-8EAC-C31BA0C1933C.thumb.png.c3f84240aefa97f7d7e5c9819879fef9.png

    Edited by Mike Poole
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    Sigh....given we have crossed swords before over the notion of bias, and I have put my position on it very clearly out there for others to see, I'm disappointed to read about it again. But seeing as y

    Hi the link doesnt exist any more plus the locale we would want to look at isnt on that small chart! Anyway evening All > Lots to be optimistic for tonight all detailed before the 18z Is

    Evening All - A very disappointing 24 hours where the very promising charts have not evolved into anything more than a fleeting prospect of deep cold > I held off all the while the UKMO contin

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    Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire
    12 minutes ago, feb1991blizzard said:

    It does i am afraid, these ridges just are not gaining traction, just transient ridges within the overall zonal flow, a classic sign that the atmosphere just isn't primed, suggests the global teleconnections are weighted towards mid latitude ridges only, its a classic tell tale sign.

    I would understand your point if there was more of a up and down snake like pattern to the gfs and ecm ext ens. However, there isn't. They just go one way. This could change of course but today the trend is clear as we approach Christmas. I think 'cold' is the watchword 😊

    Screenshot_20201212-210041.png

    graphe3_1000___-0.12574_51.5085_Londres.png

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    Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

    Some interesting example of the resurgence of the Scandi ridge in GFS ensembles with this being one of the more dramatic.

    gensnh-26-1-186.png

    If it happens then we need the undercut and WAA to head toward Greenland like this.

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    Posted
  • Location: Essex, Southend-On-Sea
  • Weather Preferences: Warm, bright summers and Cold, snowy winters
  • Location: Essex, Southend-On-Sea
    6 minutes ago, Mucka said:

    Some interesting example of the resurgence of the Scandi ridge in GFS ensembles with this being one of the more dramatic.

    gensnh-26-1-186.png

    If it happens then we need the undercut and WAA to head toward Greenland like this.

    Was about to say the same, if we want something this side of Christmas we may need to be looking NE...

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    Posted
  • Location: North East Hampshire
  • Location: North East Hampshire

    I think Mucka has alluded to this, but some early signs in the ensembles that we may need to start looking east again instead of an Atlantic ridge. 

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    Posted
  • Location: North East Hampshire
  • Location: North East Hampshire
    11 minutes ago, Mucka said:

    Some interesting example of the resurgence of the Scandi ridge in GFS ensembles with this being one of the more dramatic.

    gensnh-26-1-186.png

    If it happens then we need the undercut and WAA to head toward Greenland like this.

    Sorry, missed this post when I made mine just now, I quite agree!

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    Posted
  • Location: Essex, Southend-On-Sea
  • Weather Preferences: Warm, bright summers and Cold, snowy winters
  • Location: Essex, Southend-On-Sea

    Show better here 

    12z image.thumb.png.b910a56a534efb4877b2db47fadb79d7.png 18z image.thumb.png.e4dc286fc205f9d2ac030bfde2fb4334.png

     

    Early days in the run too, so shouldnt be strung along for days on end..

    image.png

    Edited by Snowman.
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    Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester
    3 minutes ago, Johnp said:

    I think Mucka has alluded to this, but some early signs in the ensembles that we may need to start looking east again instead of an Atlantic ridge. 

    It is Xmas, why not have both 😋

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    Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire
    5 minutes ago, Johnp said:

    I think Mucka has alluded to this, but some early signs in the ensembles that we may need to start looking east again instead of an Atlantic ridge. 

    Ridge to the E/NE would be better stratospherically for sure. Would ramp up pressure on the vortex once again.

    Perhaps Amy Butler won't be far away with her January SSW musings

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    Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire

    I have noticed over the years that the gfs pub run is very prone to over egging  north eastern height rises. I just don't see it right now. Ensembles across the suite are suggestive of height rises to our north west. 

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    Posted
  • Location: Stoke Gifford, Bristol
  • Location: Stoke Gifford, Bristol

    End of BBC update caught my eye:

    Any threat of cold and snow in January? A higher chance than last January, but we may have to wait until later in the month.

    One suspects they think a SSW may occur early-mid Jan to influence weather later in Jan?

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    Posted
  • Location: County end Oldham 202 m Above sea level
  • Location: County end Oldham 202 m Above sea level

    A thoroughly enjoyable thread tonight,  thanks for some brill contributions...

    Onwards and upwards to the 00z runs...

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    Posted
  • Location: Rotherham, East Dene
  • Location: Rotherham, East Dene
    6 hours ago, Uncertainy said:

    Good evening all

    Now that the dust has settled on our latest disappointment, it’s now a question of whether our long hoped for December cold spell has been dashed or delayed. I am going to present some evidence for the latter, with the firm caveat that anything interesting to those of a cold persuasion remains at least 10 days away, and given recent history remains hard to put any ‘real’ faith in. Nevertheless, with the AO and NAO set negative for the next few weeks at least, we only need one burst of Atlantic amplification to tap into the cold air waiting to the North (it sounds so simple doesn’t it).

    The first factor to consider is the movement of the MJO. After meandering weakly between phases 4 and 5 for what seems like an eternity, the GFS suite today finally takes the signal towards phase 6 at reasonable amplitude. No surprise then to see this manifesting in more colder solutions appearing at day 11+.

    image.thumb.gif.7b3a4d06d6a2f8d42efe0b0bd0a6431a.gif
    The CFS too with a push across the West Pacific

    image.thumb.gif.0c1c0528f26f0da2c76305dcc2841a8c.gif
    The ECM, unfortunately is much less keen and kills the signal off.

    image.thumb.gif.71d3aa5bf9c2c0e9d07e57d558b73aaa.gif

    So, supposing the American models have got this sussed, where does that leave us with our North Atlantic amplification push?

    GEM and GFS on Christmas morning:

    image.thumb.png.b3d360504185c643933c1fe4c69dfadd.png
     

    image.thumb.png.b5c4206fd19442f7710bfaaa2a57fcf7.png

    Notably good agreement at 300 hours out, a nice pattern then with good heights to the North West and lower, but not especially low heights over the Low Countries.

    Still no firm evidence of a big block in the Atlantic and associated WAA, so no Omega style Greenland block on the menu at present, but higher, stronger heights than usual seems likely.

     This is evident by viewing the pressure and heights at 500mb, rather than using anomalies. This paints a somewhat less exciting picture.

    image.thumb.png.418a0cdcf1438ccd924bef143540e993.png

    Still a mean westerly flow but weak. There are some good members in there though, the control being a prime example.

    But if the above MJO argument holds, then the ECM should be flattest, right?

    Well the ECM was the pick of the day 10 op for me and has been discussed above. It wouldn’t take much for it to turn cold if that low to the south west stayed elongated and rolled under the the developing high to the NW. If we are to get a memorable cold spell, this is one of the ways it might manifest itself. But Was the op a flash in the pan? An ECM op day 10 garden path special that we’ve been conned by so many times in the past? Not according to the EPS, I’ve delved through those individual EPS again for the big day and wow, still genuine signs for high pressure to the Northwest, low pressure to the East. Dan and Nick have generously posted the day 15 temperature and height anomalies above but they mask some phenomenal members roughly one sixth of which produce a stonking Greenland high with associated euro trough and thus a white Christmas for many parts of the UK. Another 15 or so members have high pressure to the west and a cool, seasonal NNW flow. It remains the case as I’ve said before that the traditional flat zonal Xmas pattern is not well supported at present.

    The cause of the ECM’s amplification signal in spite of its weak MJO signal could be more +EAMT or perhaps the effects of the stronger signal for a weaker vortex but it’s not clear to me. I’d love to hear anyone’s thoughts on that as my personal view here is that getting the MJO into phase 6 with good amplitude is the crucial variable here.

    The future of the strat is highly uncertain, but for our period of interest it doesn’t seem to be strengthening in time to kill a potential cold spell, it’s still reeling from the moderate wave 2 hit it’s presently receiving.

    image.thumb.png.6db802f344db20de89bcce291957b47d.png

    image.thumb.png.38958760885c093742f82941cb77c1dd.png
    Those bias corrected CFS member which do go strong do so in January. We may well see VI in early January, the seasonals seem to be seeing it too but that’s for another day.

    In summary like it or lump it there’s another chase/opportunity/pipe dream on and it might be our last/best chance for the winter. 
     

    Im in full agreement on the MJO delay. I work it to about an 8 or 9 day delay on reaching 6 into 7. Options are still on the table for a rise in angular momentum coinciding with a weaker PV due to wave 2 currently ongoing. In theory I would now be looking at a potential cold spell Christmas week into the new year (how cold open to question) and any potential ssw being pushed back to the middle of January and if lucky a quick trop response leaving a cold back end of January and February or a slower response final half of Feb into March.

    That leaves 2 potential chances for winter one in around 2 weeks time the other end of jan to beginning of March depending on strat and trop coupling 

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    Posted
  • Location: Rotherham, East Dene
  • Location: Rotherham, East Dene
    5 hours ago, Mike Poole said:

    The high over Russia has gone now, it was only ever going to deliver an easterly via promoting a SSW event and a lucky fall of the dice over the northern hemisphere.  That is off the table now.  

    82E60E4E-3CBA-4FD2-9B8D-A1075BD321E8.thumb.jpeg.b4212f8b7c1f34b8fda70b9a9b7e8edf.jpeg

    GFS pub run T270 shows what might be on the table if the Atlantic amplification coming from MJO forcing happens.  It might not though.  The table might look like this:

    575F682A-6805-428F-8EAC-C31BA0C1933C.thumb.png.c3f84240aefa97f7d7e5c9819879fef9.png

    I would suggest the scandi heights will prove more stubborn than you think if tropical signals are now re-emerging after a delay. MJO 6 promotes this and a move into 7 retrogrssion of the pattern to Greenland so I think the models are potentially ridding of the Russian high too quickly and picking up a response for a greenie high too quickly. Which still promotes wave activity for a ssw and a short term mid atlantic/Greenland High for a chance of snow after. But I think Russian or uk high then mid atoantic heights closer to new years eve and day than crimbo

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    Posted
  • Location: Rotherham, East Dene
  • Location: Rotherham, East Dene
    5 hours ago, Mucka said:

    Some interesting example of the resurgence of the Scandi ridge in GFS ensembles with this being one of the more dramatic.

    gensnh-26-1-186.png

    If it happens then we need the undercut and WAA to head toward Greenland like this.

    MJO 6 - short term gain (potential long term gain from strat damage)

    MJO 7 - Retrogade to Greenie. 

    How strong both ridges will be will be decided by amplitude. The MJO is the ace in the pack here for angular momentum and snow chances because zonal speeds are heading below average. High lat ridges are there for the taking. But not without some amplification in the pattern. Watch these RMM plots closely 

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    Posted
  • Location: Rotherham, East Dene
  • Location: Rotherham, East Dene
    5 hours ago, Johnp said:

    I think Mucka has alluded to this, but some early signs in the ensembles that we may need to start looking east again instead of an Atlantic ridge. 

    Yes John.

    Look east the models are picking up on the tropics. 

    East first. Potentially UK high 

    Then West. Good amp and a greenie high small amp north ant ridge.

    Strat intensification next move due to ssw then the real deal.

    All seems so simple but as we know it isn't has all if this had already been pushed back over a week 

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    Posted
  • Location: Rotherham, East Dene
  • Location: Rotherham, East Dene
    5 hours ago, CreweCold said:

    Ridge to the E/NE would be better stratospherically for sure. Would ramp up pressure on the vortex once again.

    Perhaps Amy Butler won't be far away with her January SSW musings

    I think she'll be out mate by a week. I would suggest 15/16 jan now as she was basing it on a Russian ridge which has temporarily relaxed due to a drop in angular momentum which is now suggested to rise again as we move back into phase 6. Phase 7 is a Greenie High.

     

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    Posted
  • Location: Rotherham, East Dene
  • Location: Rotherham, East Dene
    5 hours ago, blizzard81 said:

    I have noticed over the years that the gfs pub run is very prone to over egging  north eastern height rises. I just don't see it right now. Ensembles across the suite are suggestive of height rises to our north west. 

    I think its on the money background wise 

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    Posted
  • Location: County end Oldham 202 m Above sea level
  • Location: County end Oldham 202 m Above sea level

    Day 11 it maybe but i think GFS is sniffing at something for coldies just in time for Santa's Christmas eve trip...

    image.thumb.png.e32b8c72407ab92c112bf8b7475bc041.png

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    Posted
  • Location: Rotherham, East Dene
  • Location: Rotherham, East Dene
    1 minute ago, northwestsnow said:

    Day 11 it maybe but i think GFS is sniffing at something for coldies just in time for Santa's Christmas eve trip...

    image.thumb.png.e32b8c72407ab92c112bf8b7475bc041.png

    A week later I think pal personally. I think its doing what it does. Pick up a pattern move with it too quick drop it them re emerge round new year. I hope I'm wrong but I see more stubborn Russian high blocking for Christmas week first then our Greenie high the week after.

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    Posted
  • Location: Cyprus and North east Swindon. 104 ASL
  • Location: Cyprus and North east Swindon. 104 ASL

    Ho Ho Ho, this would feel festive

    399F4E5F-2828-44AA-875C-16753A20D492.png

    14757B91-B9B4-4FC4-878D-82853AA82185.png

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    Posted
  • Location: Cyprus and North east Swindon. 104 ASL
  • Location: Cyprus and North east Swindon. 104 ASL

    A few ENS showing the WAA possibilities around Xmas eve which will lead to a cold Xmas day, P23 and 27 are the best of the bunch

    78238016-17E3-48C6-8571-E30AF259581E.png

    D6F18309-EAC7-4258-94E9-E4148C1AFCAC.png

    6D38B21C-85DD-48FC-95EA-F921C3FC6EA0.png

    7C5BCBEB-A713-4080-B947-86CE46DE5442.png

    1DA1279B-DFDE-4F46-B849-3807901D6F69.png

    Edited by Ali1977
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