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Model output discussion - proper cold spell inbound?

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1 hour ago, ICE COLD said:

I know it's right at the end and unlikely but that's impressive -17 850s hitting the uk ūüėĀ. Let's have some of that .¬†

IMG_1326.PNG

I think some posters and people just viewing the thread  should realise that this run is very much a distinct possibility in a couple of weeks time. Virtually on par with Jan 87.

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3 hours ago, Singularity said:

So let's see... all 00z runs had Arctic height rises by day 5 but ECM and GFS keep a trail of low heights through Svalbard that prevents a linkup to the W. Asia height rises and leaves us waiting for the Atlantic zonal winds to tumble before we can get that continental flow set up (with only ECM delivering in this regard).

Given the forcing from above I would have though the models in general would be more keen to break down that trail of low heights but as it is, UKMO is the only one doing this within the next 5 days while GEM takes two days longer and the others even longer than that.

UN120-21.GIF?09-06 gemnh-0-168.png?00

 

I will admit that this reluctance is surprising me; I was anticipating a stronger, clearer model response to the first phase of warming that's focused a little NE of the UK. 

Obviously I have overestimated either the model's ability to handle the process prior to the SSW date (Sunday) or the SSW's ability to force strong blocking high development in the face of pre-existing troughs. Hopefully the former of the two as otherwise it's much harder to establish a long-fetch easterly that has the right alignment of flow to bring deep cold air from the likes of Siberia.

I think you will find that the problem is the smaller daughter vortice which splits on the Asian side. One chunk rotates clockwise around the polar block and instead of heading towards Europe (which was originally modelled on gfs fi - remember the consistent ops showing HLB)  it heads closer to the pole in the mid strat (and obviously lower down too) and phases with the Canadian vortex extension. hence, no room for high heights over the pole within 7/8 days and possibly a few after that. 

 

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GFS 06z was a little more encouraging as it at least picked up the potential for an Atlantic ridge.

It does seem that if we get substantial blocking this is currently the route the models are looking at rather than undercutting a block to our East.

GFS's recent wobbles may just be a case of it moving across no-mans land - moving away from one blocking scenario and moving toward another.

If so we can look forward to a stronger Atlantic ridge on future runs more in line with ECM.

Any potential ridge is now just  getting into range of UKMO so the next few runs may at least give us a general idea of how blocking may take hold.

If past experience is anything to go by though, the tribulations only really begin once we have model agreement on a cold spell - so save some energy!

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1 hour ago, TEITS said:

I see a sub -15C ensemble member has appeared. Anyone know which perb this is as my eyesight isn't what it used to be.:sorry:

 

You mean the one that has got it spot on Dave? ūüßź

 

BFTP

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10 minutes ago, BLAST FROM THE PAST said:

You mean the one that has got it spot on Dave? ūüßź

 

BFTP

  • There have been quite a few January 1987 style GEFS perturbations during the last few days..I'm in no way saying it will happen but we must be in with a chance..for me it's nervous excitement wondering what we will end up with from this SSW.:):cold:
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I know it has (quite rightly) been posted about (and drooled over) several times already but here it is again. P15 really is something to behold.:cold:

GFSP15EU06_348_1.thumb.png.39a2c5c79825db720ac1cf2d28cf214c.png

I'd much rather the ens keep on showing (as they have done) favourable HLB set ups than the Op being consistent with no ens support.

It would be nice to see a bit of consistency now with the ECM Op over the coming days. That's a big ask though with a setup like this but it will be interesting to see which model op nails it first with the trend to the eventual initial set up, as the upper warming starts to influence the troposphere.

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44 minutes ago, bluearmy said:

I think you will find that the problem is the smaller daughter vortice which splits on the Asian side. One chunk rotates clockwise around the polar block and instead of heading towards Europe (which was originally modelled on gfs fi - remember the consistent ops showing HLB)  it heads closer to the pole in the mid strat (and obviously lower down too) and phases with the Canadian vortex extension. hence, no room for high heights over the pole within 7/8 days and possibly a few after that. 

 

Thanks for that assessment.

So now I remain surprised but for a new reason; that a vortex lobe is able (or at least modelled as able) to head poleward so soon after a major SSW.

I don’t think that fits the script of the most similar SSWs (in terms of position of peak warming) of past. Most puzzling.

 

Edit: Using 30 hPa as guidance I can see that it remains more separated on the GFS 06z compared to 00z at +8 days:

npst30.png npst30.png

 

Differences are then more considerable a day later:

npst30.png npst30.png



There also seems to be a link to the strength of the attack on the Canadian vortex which is stronger on the 06z, so hopefully the migration of the weak Scandinavian vortex was just a wobble.

Of course a greater bridge of higher heights than what the 06z shows is desirable but there's enough time for such adjustments.

Edited by Singularity
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so... we're looking for the low thats over us here-

gfsnh-0-132.thumb.png.575e7df907266bf7cfa343222c99675e.png

to split from the main vortex and not drag another one with it around the 144-168 timeframe. if that happens we can at least briefly breathe a sigh of relief...

Edited by bobbydog
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19 minutes ago, karlos1983 said:

Whilst we impatiently wait to see what the SSW delivers our little island, we will see nationwide sub -8 850's from Sunday evening into Monday... from a Westerly !! :shok: With it will be plenty of wintry showers!

 

In need I would urge folks to occasionally look up from their computer on Sunday while they are looking at T240 T384 charts and SSW.

Sunday 6pm

prectypeuktopo.png

sunday.jpg

Edited by stewfox
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Those who were excited by p15 on the gefs 06z, that chunk of low heights is an actual piece of discarded e Asian vortex - work out the chances of it arriving on our doorstep from many thousands of miles away in a neg AO environment 

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UKMO looks pretty good to me upstream.

UN144-21.GIF?09-17

Think we would see the Atlantic ridge developing at 168 so I will be interested to see that when someone posts it.

GEM getting there.

gemnh-0-210.png?12

Edited by Mucka
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1 hour ago, bobbydog said:

i would agree that sunday is when we should start to see a clear path. by tomorrow, we see a complete stratospheric split-

gfsnh-10-30.thumb.png.85e5ebbe6e6f27b0b20ef605f1aa343c.png

then on sunday, zonal winds are slammed into reverse-

u_65N_10hpa_gefs.thumb.png.dce28836416d3fb9740b76d1eca80bd6.png

and the polar vortex meets its final oblivion of the season.

if that doesn't get us a decent end to winter then...

avoox.thumb.jpg.0e84ae30cacbe1bf3019e20a8791d036.jpg

And according to this Tweet from @MetmanJames, it’s the most significant reversal at this time of year on record. 

‚ÄúIf the GEFS ens mean is to be believed (and the spread is small enough to support this), this will be the most easterly the stratospheric winds have been on the 10hPa layer in mid February in the period 1980-2016.‚ÄĚ

A1F9C5E6-25CC-42BB-AEC1-E81D30E0DE96.thumb.jpeg.90d1e1dbad1c6e5347d516435a7e9267.jpeg

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3 minutes ago, bluearmy said:

Those who were excited by p15 on the gefs 06z, that chunk of low heights is an actual piece of discarded e Asian vortex - work out the chances of it arriving on our doorstep from many thousands of miles away in a neg AO environment 

which is it!!

Image result for so you're telling me there's a chanceImage result for it's a no from megensnh-15-1-372.png

Edited by karlos1983
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GFS12z looks pretty poor to me, everything seems to be getting messier and messier on the GFS. Troughs phasing across the Atlantic...

IMG_0103.PNG

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Just now, Weathizard said:

GFS12z looks pretty poor to me, everything seems to be getting messier and messier on the GFS. Troughs phasing across the Atlantic...

IMG_0103.PNG

yes... where's Trump's big red button?...

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7 minutes ago, bluearmy said:

Those who were excited by p15 on the gefs 06z, that chunk of low heights is an actual piece of discarded e Asian vortex - work out the chances of it arriving on our doorstep from many thousands of miles away in a neg AO environment 

Ian F retweeted this yesterday so make lf of it what you will. 

 

Highlighting for part about cold pooling from Asia.

 

 

Screenshot_20180209-162618.png

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4 minutes ago, ALL ABOARD said:

Ian F retweeted this yesterday so make lf of it what you will. 

 

Highlighting for part about cold pooling from Asia.

 

 

Screenshot_20180209-162618.png

I actually found that gif rather underwhelming in terms of depth of cold that comes west when i saw it.  

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12 minutes ago, karlos1983 said:

which is it!!

Image result for so you're telling me there's a chanceImage result for it's a no from megensnh-15-1-372.png

Its been hinted at in the operationals too as i posted yesterday 

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GFS 12z has high pressure slowly building up from the south 06z had a deep low

gfs-0-198.thumb.png.8b252f755e7b8f63204339d3a0f79999.pnggfs-0-204.thumb.png.6071c976868ab833fdd68b1fee345171.png

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19 hours ago, winterof79 said:

This is worth the entry fee alone the lump of PV across the ARCTIC may feed and support our HLB as the weather starts flowing in reverse in the NH

tempresultdub1_mini.png

Here you go it's a recurring theme the Eastern Asian lobe feeding under the block westward

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3 minutes ago, Summer Sun said:

GFS 12z has high pressure slowly building up from the south 06z had a deep low

gfs-0-198.thumb.png.8b252f755e7b8f63204339d3a0f79999.pnggfs-0-204.thumb.png.6071c976868ab833fdd68b1fee345171.png

And still she goes Northward

Screenshot_20180209-164221.png

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Distinct lack of low heights to our North East, WAA to the Pole , opportunities for height rises to the north east perhaps...

gfsnh-0-216.png?12gfsnh-1-216.png?12

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