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The hunt for cold - Model discussion (late November)


Paul
Message added by Paul

If you're hunting for cold potential in the model output, this thread is for you. But if you'd like to look more widely at the models, please head over to the general model discussion thread.

This is a model related thread, so a general, frequent theme of the model output is a given, but it will not be strictly enforced:

  • Some topic drift, humorous responses etc are fine
  • Posts likely to lead the thread off on an entirely off topic tangent are not ok. For example (but not solely limited to): Posts entirely or mainly about Met Office, BBC or media forecasts with little or no model context, and posts solely asking for a weather forecast in a specific location.
  • Posts which start with something like 'I know this is off topic but ...' are not ok.
  • Posts which break the forum guidelines are not ok (eg trolling, troll-hunting, weather guilt tripping, overly defensive/aggressive, abusive, disrespectful to others)

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Posted
  • Location: st albans
  • Location: st albans
10 minutes ago, TomSE12 said:

Hi b81,

That GFS Control run would be a lovely 39th Anniversary and a nod to your Avatar name.

GFS CONTROL RUN 8th DEC.2018

gens-0-1-240.png

Rain to snow event for many parts of the U.K, I would've thought! :whistling: As was December 8th, 1981.

8th DECEMBER 1981.

archives-1981-12-8-0-0.png

Lived in Camberwell, S.E.London at the time. Early heavy rain turned to heavy now around breakfast time, despite thev rain soaked ground, the snow eventually settled to give around a 2 inch wet covering, not bad for an Inner London location. It caused transport chaos during the rush hour, in the S.E. It was my day off from work. I can remember watching the University Varsity Rugby match on TV, between Cambridge/Oxford. The match went ahead with a couple of inches of snow on the pitch, at Twickenham. 

As someone mentioned earlier snow before Xmas is not a usual visitor, especially in the south of the U.K. I'm 63 and can't remember that many occasions of snow pre-Xmas. Even the severe Winter of 62/63 didn't get snowy until Boxing Day. Patience, is the watchword!!

Regards,

Tom.  :hi:

Dutch ens are the eps control Tom ......

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Posted
  • Location: Gillingham, Kent
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Gillingham, Kent
8 hours ago, Daniel Smith said:

Good question. 

I've not stated that I'm expecting deep cold, I'm with Bluearmy sitting on the 50/50 fence. But there's a few reasons why I think the Atlantic onslaught is going to be temporary and why I think a return to a more blocked pattern come mid-December is likely.

Reason 1: EPO/NAO

EPO is currently expected to go more negative and this supports troughing across the Eastern Seaboard and a more active Atlantic Jet (this is being seen currently/forecast on most models) In response we also see the NAO trending more positive

EPO.thumb.png.5de9d50573a9da000312a604d66f3590.pngNAO.thumb.gif.b6f3143379a0da2ce291dde7093332c9.gif

The AO is expected to remain negative throughout, for what it's worth, even becoming more negative than it currently is

ao.sprd2.thumb.gif.8ddfb3686b434e6ef1504355d059863a.gif

14 day EPO forecast is suggestive of a return to neutral/positive after a short negative dip, I expect the NAO forecast to trend more negative once again when that takes place.

Reason 2: MJO

Phasing through 8-1 as we go into December, whilst amplitude should be enough to at least trigger the Atmsophere to produce some sort of blocking response, add the lag and that takes us to around December 15th

MJO.thumb.gif.edddfbe11cc88cf57081871df1cf219e.gif

Reason 3: EPS/GEFS ensembles (EPS left)

427436732_Screenshot2018-11-28at12_55_00.thumb.png.bbc75c504a5c05ac681f6058d01304fe.pngGEFS.thumb.png.72495886072ebf4884d10c4dabe7fe47.png

I know I said the ensemble means are useless at that range in this situation in a previous post and to a large extent, they are. However, there's agreement between both models for heights towards Northern Scandi/across much of the Eastern Arctic days 10>16. The Atlantic trough more prominent on the EPS is almost non-existent on the GEFS means = huge uncertainty. 

However, what is rather certain in the Arctic blocking and heights towards the Scandi region. EPS also has a clustering of colder solutions in the extended, though given the spread not much can be gleamed from that

ECM11.thumb.gif.8c98936edb2575192d8e9cd598d2e7e0.gif

Comparing all the Deterministic runs, there's a clear though not major signal for a cooling trend towards the end of the first week of December, also note the reduced PPN signal suggesting an Atlantic onslaught is unlikely to continue

mgram_London.thumb.png.c76b5b8be327c3f035acb882f11de174.png

So.. deep cold? I'm not sure, that of course depends where the blocking sets up/if we can tap into the cold air, as others have said there's not really a signal for "deep cold", however. 

Neither is there a signal for a continuation of mild, Atlantic, wet dominated weather, either..

That's my reasoning/why I expect a blocking theme is more likely going towards mid-December, away from the Operationals I'm struggling to see a prolonged zonal signal within the models/background signals.

Going from GP's posts too (a little above my pay grade), various other signals other than the ones I've mentioned in this post are also suggesting zonal weather through December is unlikely.

 

As the 18z rolls out I just want to re-post this. Nothing has changed as far as i’m concerned, if anything the 12z suites have taken a slight step back from zonal now.

No deep cold signal.. yet..

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Posted
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
  • Weather Preferences: Sunshine and 15-25c
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
26 minutes ago, TomSE12 said:

 

. Even the severe Winter of 62/63 didn't get snowy until Boxing Day. Patience, is the watchword!!

Regards,

Tom.  :hi:

ha ha i wondered how long before this classic 62/63 line made an appearance..was only a matter of time esp after somebody mentioned putting the building blocks in place another usual phrase..once we get past Xmas it will be 78/79 didn't get going until the end of the year and then once into Jan ...47 didn't start until the last week of January etc etc

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Posted
  • Location: Cambridge, UK
  • Weather Preferences: Summer > Spring > Winter > Autumn :-)
  • Location: Cambridge, UK

67E41601-D8A7-485F-927A-B8F416DC4591.thumb.jpeg.d4c173a33cc918846f2fea1a3927ee99.jpeg

ECM ensembles look classic zonal out to mid December sadly, big Aleutian and Icelandic troughs with strong westerly momentum. Going to take some shifting now we’re in this situation.

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Posted
  • Location: NW LONDON
  • Weather Preferences: Sun, sleet, Snow
  • Location: NW LONDON
4 minutes ago, cheeky_monkey said:

ha ha i wondered how long before this classic 62/63 line made an appearance..was only a matter of time esp after somebody mentioned putting the building blocks in place another usual phrase..once we get past Xmas it will be 78/79 didn't get going until the end of the year and then once into Jan ...47 didn't start until the last week of January etc etc

lol last winter didn't get going until spring  all this hunt for cold in here, has anybody found any yet?

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Posted
  • Location: Wyke regis overlooking Chesil beach.
  • Weather Preferences: Snowfall
  • Location: Wyke regis overlooking Chesil beach.
10 minutes ago, cheeky_monkey said:

ha ha i wondered how long before this classic 62/63 line made an appearance..was only a matter of time esp after somebody mentioned putting the building blocks in place another usual phrase..once we get past Xmas it will be 78/79 didn't get going until the end of the year and then once into Jan ...47 didn't start until the last week of January etc etc

The reason they,re 'classic' Cheeky monkey is because they're true.

'

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Posted
  • Location: Southside Glasgow (135m)
  • Weather Preferences: Beginning with S ending with W ;)
  • Location: Southside Glasgow (135m)
9 minutes ago, mb018538 said:

67E41601-D8A7-485F-927A-B8F416DC4591.thumb.jpeg.d4c173a33cc918846f2fea1a3927ee99.jpeg

ECM ensembles look classic zonal out to mid December sadly, big Aleutian and Icelandic troughs with strong westerly momentum. Going to take some shifting now we’re in this situation.

Already been put in the bin by guys over in US forum along with them siding with GEFS over EPS, due to continued backtracks by EPS in past month. Initial warm up expected to last no more than one week over in states. With majority of background signals pointing towards renewed blocking around mid-month, think is more of a case of human input being more reliable in next week or so. Didn't help with MO extended changing after only 2 days - uncertainty at highest level of computer input? Should add the weeklies belong in same category as CFS.

Edited by Bullseye
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Posted
  • Location: Tyrone
  • Location: Tyrone

Clear sign the jet is moving further south each run early on as day 5 could be some snow for northern hills next week watch for wedges to appear to are north later on.

gfs-5-156.png

gfs-1-126.png

gfs-2-156.png

Edited by booferking
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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

CFS watch, the long range much maligned model still resolute with the negative AO picture for December, here the last 8 runs, average sea level pressure anomaly:

image.thumb.jpg.2a8602a39865011ec55efbed35187a0b.jpgimage.thumb.jpg.257fe5ff4e771924b28fc5d8cd481168.jpgimage.thumb.jpg.2906d4450dcd98f792b117b63e1ede86.jpgimage.thumb.jpg.cbc27bdb1c34192de19f2c58f8ac1f67.jpgimage.thumb.jpg.f61ccf1f441f878fda648a4556acdb01.jpgimage.thumb.jpg.d44060f0f5f7098a5de2e51c4661d2a6.jpgimage.thumb.jpg.32d4b0e71430b4673916a6ac001239b9.jpgimage.thumb.jpg.f98fbdb64c2b6e588aaadb941da2dbe1.jpg

CFS only makes sense probabilistically, hence the need to show multiple runs.  One caveat, is that -AO as shown in the charts doesn't always equal -NAO, what we're looking for.

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Posted
  • Location: st albans
  • Location: st albans

18z slower again upstream......less defined upper ridge but higher heights spread around in general via some wedges ........Asian upper ridging looking more interesting in general ..... time for the clusters .......will that small one which the 12z control resembled somewhat  have grown ......

Edited by bluearmy
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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.

There's loads of uncertainty - you can see that by the run to run variability of the ops, even at a relatively early stage in the run, however, there are not bucket loads of runs (ens included) that either bring deep cold or look like bring deep cold as a percentage, so its almost a case of not being confident about what will happen but being very confident of what wont happen, not out of the question that a brief snow event could pop up from nowhere out of a mini-undercut situation,but more than likely nothing special and washed away quickly.

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Posted
  • Location: Gillingham, Kent
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Gillingham, Kent

“Mild Zonal” on the charts has become “cold zonal” today.. give it a couple of days and we wont be using the word “zonal” at all to describe what the models are showing..

All ticking along very nicely 

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

GFS 18z, T240:

image.thumb.jpg.9a704c7eb251537381d35def679367c9.jpg

image.thumb.jpg.e13ab3fa42fdfa0ec170e5b7a0d37a00.jpg

Two fingers stuck into the vortex, ours the smaller one at the moment, the bigger one, more a thumb actually, into the Arctic high.  As others have said, a more southerly track of the jet stream is evident.  Lots to like.

Edited by Mike Poole
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Posted
  • Location: Hertfordshire
  • Weather Preferences: SNOW AND FREEZING TEMPS
  • Location: Hertfordshire

And the gfs hits low res and blows up the Atlantic . The cold goes to the east . 

F73B360D-D6CE-413E-AF63-D6A74CBE5EED.png

E6FC77CB-D3DB-43B2-A70B-98D878041AF4.png

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Posted
  • Location: STEVENAGE, HERTS (100M ASL)
  • Location: STEVENAGE, HERTS (100M ASL)
8 minutes ago, Steve Murr said:

GFS 18z developing rather like the control that develops the greenland high in situ..

DACB594C-5422-4B6E-BD4A-D1CA8C3F7756.thumb.png.9e2a2e779d4aec29ed72da7bc8afb98c.png

Can’t see a Greenland high ? Siberian high Is huge though ...

AB3C4E9E-459A-41A0-89C5-3F473F9E7AB0.png

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

May not be cold but that high is a monster.

gfsnh-0-360.png?18

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