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Model output discussion - Winter approaches


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12 minutes ago, northwestsnow said:

18z ushers Dec in with a cold flow . .

It very nearly ushered in Dec with a right pasting but the trough didn't slide enough, too much energy went NE - rain for Western Britain.

Edited by feb1991blizzard
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Hi all . I’m back from my summer hibernation . A warm welcome to all the new members . It’s hard to believe we’re back again chasing those hard to come by good winter charts . It’s true the older

This is the ECM at 96 hrs v's the reanalysis for the 3rd of Nov 2010 and bears similarities in our part of the world now you wouldn't think that the epic winter of 2010 would come from that

Time to start wheeling out the ECM snow depth charts then 😍. Please remember it is mandatory to reply with how unreliable they are and how it accumulates all falling snow even if it doesn’t settle bla

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Got to say the 18z doesn't evolve the way we really want it, however there are a fairly high number of ECM ensemble members that aren't that different by 240hrs with LP strengthening either to our NW or N. 

Some move it close enough to pull in a decent WNW, some get it far enough east to drag down some form of cold air, others end up us back in a net W/SW type airflow. Plenty to get through before that point however.

Its not a bad run later on, but its certainly not a great one either past a marginal easterly airflow.

Edited by kold weather
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13 minutes ago, Zak M said:

Just flicked through the 12z GEM ensembles and quite a few perturbations are showing some colder options on the table. The GFS is also showing some colder perturbations too.

gens-9-1-336.thumb.png.1fa79357a11559af614a6c967672a7f8.png   gens-9-0-372.thumb.png.c8aae06dd7f25795f4dc0c02ba1924a2.png

ECM mean @240 is showing the building blocks of a northerly, with height rises in the N Atlantic:

 

And look at the ECM clusters... 👀

ec-ens_nat_z500scenarios_2020112312_240.thumb.png.a8d376fdfbe2f9d482b72927a1911eba.png

33/51 of them are showing some sort of northerly at around day 10-11 - some agreement there but we need this to be in the reliable timeframe (<5 days)

Having looked through the actual ECM ensembles there really is quite alot of disagreement actually despite what the clusters suggest, though quite a few do have some sort of N/NW influence at day 10, but many are what I'd describe as at best glancing blows, or limpet northerlies/north-westerlies that won't be nearly cold enough aloft for any all that interesting outside of maybe high ground in the north.

Below average though still favoured on the ensembles, but its cool rather than cold on a great many of them.

Edited by kold weather
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7 minutes ago, Mr Frost said:

Here are the more interesting charts from the latest ECM Monthly Temperature (T2m) anomalies - weekly breakdown below:

30/11 to 06/12:

729F12D0-CA3A-4FA6-BE09-0A248FF0EC83.thumb.png.cf3df86d3d943371432ac133c313e8c2.png

 

07/12 to 13/12:

8121539F-5809-40A0-B667-25F7A9B38D4C.thumb.png.b9c0966ba8c5bffc9faf463ffb9c180f.png

 

14/12 to 20/12:

4561E736-E5BB-4869-A4FB-FA3432479CA0.thumb.png.0e2a4b927da86cf91626fb3c29fdcce2.png
 

Looks like we will end up in a weak Atlantic situation with the upper trough axis being probably close by to the UK with the main frontal zones probably being to our south which is reflected in the precip maps above. Also means the worst of the above average air is kept to the east, but whilst we keep this pattern there is only limited chances for anything beyond cooler than average to show up, probably from the NW in that type of set-up.

The worry has to be that this period is as good as the background synoptics are going to get, especially if we do not any stratospheric disruption for the 2nd half of winter. I know its somewhat decoupled right now, but I always worry about how long such a situation can hold for.

Edited by kold weather
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The day ten mean18z is an improvement on the 12z where it was flat across the Atlantic,more of a trough digging down from the NW into the UK

GEFS mean at 240 v's the ECM

gensnh-31-1-240.thumb.png.7a5be65ff569db341dcf48e39423c72e.pngEDH1-240.thumb.gif.34efbdcd4748e3e0b36e6b39d5086d00.gif

There is still quite a few options on the table in the gefs ens at day ten,heights are stubborn to are NE forcing trough to drop down in the vicinity of the UK,some heights are stronger/further north to our NE with easterly winds,some have higher heights to our west forcing a northerly of sorts and some with heights over the UK with some chilly nights with fog and frost

i feel a standoff is still on the cards with the Scurasian high and Atlantic high,which will become the strongest will determine the weather,IE:-

stronger the Scurasian block,possible easterlies

stronger the Atlantic block,possible northerlies

my gut is the Atlantic block winning out,just my opinion looking at the anomalies.

 ecmwf-ens_z500a_nhem_11.thumb.png.ec8ec23650e11902d2f5186d949a2304.pnggfs-ens_z500a_nhem_41.thumb.png.2267d8e8bddc3d722b652edb05c8543f.png

610day_03.thumb.gif.6d2df1f71d22713d7a456a554a00fed8.gif814day_03.thumb.gif.917ce279a025b44070a258064eeb4b2a.gif

but we need this Atlantic block further north and more amplified otherwise we would just get a cool possibly cold polar maritime nw'ly flow.

Edited by Allseasons-si
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Now here is an irony for you

gefs ens for my local and for London

graphe3_1000_263_30___.thumb.png.79bdf734ce759341ab568a24c0712110.pnggraphe3_1000_309_144___.thumb.png.2dfe3a97895b79a772229a5cee00d21a.png

some of the London ens are trending colder by next weekend with more of a snow row than here

this suggests to me that the se of the UK will have more of an influence from a continental source of cold air

but i must stress,look how much scatter there is from days 4-5.

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I don’t for one minute think it’ll be there on the next run but this is an interesting FI. Low pressures filling up the med and a high pressure building to our E/NE.

1C8E6047-27BA-415E-9864-9EBFC0F3FDF7.png

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17 minutes ago, Ali1977 said:

Cracking day 10 on the way with heights Diminishing any LP to the NE of Canada. If those heights near Newfoundland head North we’ll be in BOOOOOOM territory 

3D93DF18-A5B7-4AC6-B8E5-D99E050A0C17.png

It looks like a west based nao could follow on from that imo. Hope not. Would love a potent northerly.

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