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Model output discussion - mid-winter

Paul

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ECM clusters. 

First a reminder that the Scandi heights rise, first championed in the ECM ensembles around the turn of the year 10 days ago, really happened:

ec-ens_nat_z500scenarios_2018011000_072.

Looking at the clusters for the 13th January at the start of the year (T288 and T264 at that time), I'm guessing a mean chart based on these would have been extremely close to the final outcome (Scandi heights on some, Atlantic pushing in on others, possibility of a split trough - just the strength of the vortex over Greenland underdone). Nice-ish work ECM!!

ec-ens_nat_z500scenarios_2018010100_288.  ec-ens_nat_z500scenarios_2018010200_264.

Which can give us some confidence when looking ahead with the clusters, at least for the macro scale if not the micro scale. By T216 on the clusters, we see the familiar tale of the Atlantic trough pushing through the UK but how far north/how quickly??

ec-ens_nat_z500scenarios_2018011000_216.

I would guess a period of WNW followed by NW or even temporarily a N flow coming up around 18-20 Jan. Snowy on hills, lowland areas will need a strong flow through the Atlantic and runner features underneath. An extended gap between troughs (e.g. cluster 1) could help draw cold south. So could happen but not a given and - just to be clear - the main focus is cold rain and wind in this period, not snow.

Once again, beyond T240, only one cluster - which does look a little blocked in the Atlantic - but inspection of the individual members on weather.us reveals like last night, no usable trend passed about D12 - I wouldn't even dare to guess. Perhaps that's a good thing for those wanting something less ordinary - as the ensembles usually cope better in predictable set-ups??

Edited by Man With Beard
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Atlantic making inroads by Monday now into the reliable timeframe, so a spell of cold zonality next week likely. Although the N and NW of the UK favoured for snow, perhaps to lower elevations for Scotland and with elevation further south during the day, one or two secondary waves embedded in the NW flow could bring snow further south and perhaps transitory to lower levels.

Although last night's 18z and now 06z GFS op offers some eye candy synoptic-wise, I'm trying not to fall into the trap of having knee-jerk reactions to each 6 hourly update. There appears to be some discontinuity growing between EPS and GEFS with the northern and southern extent of the lobe of the tropospheric PV extending SE across Atlantic into Europe later next week onwards, and this seems to be tied in with the strength and expanse of the high latitude ridge modelled from Barents Sea across Svalbard and into Greenland. From the 00z day 10 ens below you can see the EPS mean further north with the trough than GEFS (which is stronger with the high latitude ridge too) :

eps_z500a_nh_41_100118.thumb.png.39567dfaba3d2fef67361e322cb3182b.pngEPS mean day 10

gefs_z500a_nh_41_100118.thumb.png.789aa34dcd50088697755fead21d2f7d.pngGEFS mean day 10

The 06z GFS op has the ideal combination of amplification developing from upstream over the Atlantic from days 8-9 which combines with the high lat ridge over Greenland/Svalbard to disrupt the Atlantic trough and push a cut-off low into Europe.

But until there's agreement between GFS and EC on how to evolve the placement and shape of the upper trough extending SE into Europe next week and also modelling any amplification working downstream over the Atlantic plus strength / effect of ridging over Svalbard, then I won't be jumping in bed with the better looking 18z and 06z GFS just yet.

Edited by Nick F
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Thoughts of yesterday further heightened!..

Potent-pm flow with surprise elements, as regards possible transitional/nowcast snow situ's as the flow gains and impacts the uk.

Into next week an alignment of shallow heights in-and around greenland/NW northern-hem...with momentum then exacting, possible transfer of cut off heights around scandinavia- and a more continental feed..

A basic overview for now- as the models decipher, the placements/exactions of the notable polar martime incursion!

Keeping a firm eye on supports for latter prognosis- ens etc.

Some very interesting synoptics/develpoments leaning in now.

Edit;..

Had to use snapshot-format...

A few issues with posting here atm??!!

Screenshot_2018-01-10-11-02-51.png

Screenshot_2018-01-10-11-00-59.png

Screenshot_2018-01-10-10-58-55.png

gfs-0-234.png

Edited by tight isobar
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Most if not all Ensembles dig the Low south east into Europe.
 

Some develop a wave/secondary low that creates the chances of some heavy snowfall.
gens-1-1-144.pnggens-1-2-144.png

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1 minute ago, frosty ground said:

Most if not all Ensembles dig the Low south east into Europe.
 

Some develop a wave/secondary low that creates the chances of some heavy snowfall.
gens-1-1-144.pnggens-1-2-144.png

That shows the midlands getting hammered!!

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GEFS good wrt thin wedge of the scandi high ridging W wards towards Greenland.

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This combined with a more amplified atlantic should result in more members being blocked in the 240 range.

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Big shift SE of the trough at +174 on the 06Z GEFS mean compared to the 0Z.

gens-21-1-174.png

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Massive difference in the ECM/GEFS mean charts

EDM1-168.GIF?10-12  gens-21-1-168.png

A small cluster on the ECM ensembles resembles the GEFS (cluster 3, 21% of members).

ec-ens_nat_z500scenarios_2018011000_168.

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Looking at the GEFS 6z mean, next week shows progressively colder zonality with increasing chances of snow through next week, especially higher up and further north but a strong blast of cold zonality is indicated so it would feel wintry everywhere..as I've said before, next week looks a lot more interesting..for coldies!:):cold:

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Main GFS & Control not too far apart in the latter frames with heights building to the North.

gfsnh-0-240.thumb.png.8028fbff14fbebceadce841593d3dca7.pnggensnh-0-1-240.thumb.png.59c4533f854c85aa56e1c1e4cec27d31.png

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Interesting comments because at the moment this isn't GEFS/GFS Vs ECM.

I shall try and explain later when I have more time using one of my drawings because there is one key factor that everyone has missed today in the output so far!

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20 minutes ago, Man With Beard said:

Massive difference in the ECM/GEFS mean charts

EDM1-168.GIF?10-12  gens-21-1-168.png

A small cluster on the ECM ensembles resembles the GEFS (cluster 3, 21% of members).

ec-ens_nat_z500scenarios_2018011000_168.

I always wait for next ec suite before jumping on a change - the eps often follow the op trend, only to switch back later 

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4 minutes ago, TEITS said:

Interesting comments because at the moment this isn't GEFS/GFS Vs ECM.

I shall try and explain later when I have more time using one of my drawings because there is one key factor that everyone has missed today in the output so far!

The x factor:rofl:

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1 minute ago, bluearmy said:

I always wait for next ec suite before jumping on a change - the eps often follow the op trend, only to switch back later 

Absolutely BA - I think the current eps would suggest not getting carried away with the GEFS - yet!

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7 minutes ago, TEITS said:

Interesting comments because at the moment this isn't GEFS/GFS Vs ECM.

I shall try and explain later when I have more time using one of my drawings because there is one key factor that everyone has missed today in the output so far!

Oh go on give us a clue! :)

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Morning all :)

Birthday watch got delayed last night which may have been no bad thing.

We're well into high-res for next Monday's chart so you'd think the models would be firming up in agreement:

So let's see:

GFS 06Z OP for T+126:

gfs-0-126.png?6

Control at the same time:

gens-0-1-126.png

GEM 00Z OP at T+132:

gem-0-132.png?00

NAVGEM 06Z at T+126:

navgem-0-126.png?10-12

Finally, ICON 00Z at T+126:

icon-0-132.png?10-00

ICON stands out as a slight exception (though ECM isn't far removed from it) otherwise we're pretty much in agreement. A vigorous extremely powerful LP storm develops the day before off the south east coast of Greenland as a lobe of PV energy is ejected SE and this deepens sharply to 935-945MB before starting to move ESE for most - at present, most models are taking the storm as a weakening feature ESE into Europe though there are a number of complex iterations within that.

The resilient HP block over Scandinavia has "slowed down" this development - the models from five days ago were showing the LP across the British Isles on the 15th but that has been put back 2-3 days because, I would argue, the block has intervened. What it does show for model forecasting purposes, is that, irrespective of whether the block directly impacts the UK weather, it has considerable upstream implications if it proves to be more resilient.

Here's a thought - the California storm modelled on the GFS 00Z OP at T+54 (so Saturday's output):

gfsna-0-54.png

The same storm four days earlier (00Z OP output for 3/1/18 at T+150)

gfsna-0-150.png

Still out in the Pacific - I don't know but has the behaviour of the block and the weakness of the Atlantic over here had ramifications in terms of the progress of the Pacific storm systems or is there no causal relationship at all ?

 

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There are some stunningly wintry GEFS 6z perturbations in the mid / longer range which makes me think something really wintry could be brewing in the next few weeks.this is just one of them which shows the cold block getting mighty close.:cold::)

9_318_850tmp.png

9_318_2mtmpmax.png

9_342_2mtmpmax.png

9_342_850tmp.png

Edited by Frosty.
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Afternoon all :)

It's all gone quiet...

The 06Z GEFS are an interesting bunch:

gensnh-21-1-288.png

The majority (I would contend) weaken or lift the PV out of Canada completely by T+288.

Here's Control (which oddly enough retains a chunk of PV in its usual habitat):

gens-0-1-288.png

So it begins - first hints in the ENS followed by appearances in the OP and some stellar output at T+168 and T+144 only for the whole thing to be watered down from then.

Maybe, maybe not.

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Hey frosty on that last picture it looks like two thumbs (S/W UK) trying to push the block back.:rofl: Are they strong enough ?

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3 minutes ago, Fozfoster said:

Hey frosty on that last picture it looks like two thumbs (S/W UK) trying to push the block back.:rofl: Are they strong enough ?

iTS A SNAIL.

Hopefully it will come into the cold air (slowly) and stall then slide.

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Come on Dave (TEITS) hurry up and put us all out of our misery? :yahoo::cold:

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I rarely do well at all IMBY from NW’ly but the NWP are giving me hope. A very unusual set up indeed. Climate change? Or is that for another thread? 

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I would say a spell of generally cold zonality / cyclonic weather is in the bag as far as next week is concerned (after monday) feeling increasingly cold and wintry even in places that don't see any lying snow but I expect there will be lying snow for some next week, especially further north and with elevation and most of us should see overnight frosts / icy patches.:):cold:

Edited by Frosty.
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