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Model output discussion-mid Autumn and beyond

Paul

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Latest (06z) gefs for days 10/15 and 5 day 2m temp.anomalies (days 11-15)

gfs-ens_z500aNorm_nhem_41.thumb.png.b86402fb810111b7967eaaf6e0e9c6e2.pnggfs-ens_z500aNorm_nhem_65.thumb.png.4d0f0e0fa31cfc779c2370a25bf8419e.pnggfs-ens_T2maMean_nhem_11.thumb.png.29335084798c67bced5f2dd3c5059a1e.png

Pretty much on the same lines as the above eps with the core of the ridging retreating west with signs of a developing trough heading into Scandinavia.Temperatures not far from average with the Atlantic flow picking up again as the high moves with perhaps more of a north westerly flow.

Edited by phil nw.
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According to this evening's gfs the high pressure doesn't have things entirely it's own way. On Friday a small low and associated front sneak around the northern flank to bring some rain and lively winds to Scotland

gfs_z500_vort_natl_21.thumb.png.5d14c4250989b802135a46a5166bcb54.png

And then over the weekend another much deeper low near Iceland and associated fronts brings some patchy rain and fresh winds to much more general area of the country albeit not the south  Temps above average and up to 13C in Scotland on Sunday

gfs_z500_vort_natl_28.thumb.png.eac816ed14ef3f3a27bca25f58df5abf.png

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The ecm is on the same page as the gfs at T120 but thereafter not. It amplifies the HP over the UK and has more success rebuffing the east bound energy and then girds it's loins for the next round. That is still not to say the position of the surface high cell effectively blocks every thing and bits and bobs of systems do nip around the northern flank bringing some cloud and patchy rain to Scotland on occasion. A fair bit of regional variation vis cloud and temp,

ecmwf_vort_500_natl_21.thumb.png.0fb5aab164c82702f45f8a2b31e4a65e.pngecmwf_vort_500_natl_28.thumb.png.98ded28aeee8cfbc7ad653ad0739d085.png

On another note I've heard disturbing rumours of discontent in the other thread, Just to say I feel their pain.

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Although the ext GEFS and EPS are certainly in the same ball park there are some significant differences.We are looking at low pressure over the Aleutians with twin vortex lobes Franz Joseph and N. Canada and a fair bit of amplification over North America courtesy of the west/east ridge trough combination. Still a very strong upper flow exiting the eastern seaboard across the Atlantic but this where the difference becomes relevant

The EPS now has less amplification and thus retains a pretty strong westerly flow over the UK as the ridge relaxes somewhat.,The gfs on the other-hand is still quite amplified with the ridge/European trough taking on a positive tilt. Thus portending a different orientation of the surface high cell with greater blocking potential. Either way neither are showing any indication to amplify north west at this stage, Certainly a reduction of the upstream energy supply is needed to facilitate this.

10-15.thumb.png.1b8dcf7023e3a759fbaf080eea10433f.pnggefs_z500a_5d_nh_61.thumb.png.d97d09c68341966eb80a993e2cc2e280.png

 

 

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Had my occasional scoot through the individual ECM ensembles tonight. By D15, by far the majority maintained the status quo of strong pressure through West Europe, and the typical low pressure train between Iceland and Greenland. With the UK High likely to slip to our south slightly, above average temperatures are favored. Probably less than 25% of runs giving a realistic chance of UK snow in the first third of January, and given where the runs all end up, not a much higher number with a realistic chance of snow even by mid month. 

The caveat is - this is D15, and so set in sand rather than stone - however, there's a clear signal in the ensembles (not always there by D15), and therefore confidence has to be higher than usual. 

Or will the potential SSW cut it all down to shreds? 🙂

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This morning's ECM ensembles are little different. By January 8th, 75% ensembles have the UK in a flow between west and south, with average temps or above. Of the remaining ensembles, generally heights building west or north west, leading to a northerly flow (or incoming northerly behind), but even in the colder runs, no particularly strong blocks in wintry positions. 

This is not to say there will not be cold weather before 15 days time. An optimally positioned UK high could produce very cold surface conditions at this time of year. That is a fair possibility in the days leading up to 8th.

Edited by Man With Beard

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Apropos nothing at all really but just looking at the warming at 10mb at some places over ten days or so

853659463_zeja1.thumb.JPG.cb7539c5f7b1462632fb23bfd0978e3e.JPG2043211912_zeja2.thumb.JPG.d3a59c080a9db7dc63e87395674ebf87.JPG

 

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50 minutes ago, I remember Atlantic 252 said:

may be negative, but GFS still going for unreal mild weekend, 15 degrees in NE?  such a mild Dec it's unreal

gfs-0-126.png?6gfs-0-150.png?6

Temps could be well above average at times next Sunday could see temps widely in double digits if the chart below on the right comes off

ANOM2m_mean_europe.thumb.png.cb2c371ac37b9113b749442902e531a9.pngANOM2m_trend_europe.thumb.png.37bbd56eded65b136b3ced2cd5014ce0.png

 

Edited by Summer Sun

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Hi fellow net weather friends. I am lurking about and do read the posts on model discussion forum .I wish you all a good Christmas and New year to you all. STELLAS  all round  cheers. 

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Distribution of energy and a certain fluidity of the ridge,

Some frontal rain on Friday on a decaying front. Then another intense upper trough dropping south in the western Atlantic and more amplification. And then the pinver movement around the ridge

gfs_z500_vort_natl_17.thumb.png.5efcda1f1163d0d25552a74bf56323ff.pnggfs_z500_vort_natl_29.thumb.png.b9a7b35195438f9a216bc65c875dee72.pnggfs_z500_vort_natl_37.thumb.png.f4f18e6239f17a57e60229ac3129fac8.png

And an idea of the airmass characteristics involved

gfs_t850a_natl_29.thumb.png.20595ed25401de52edaa5def62de4639.png

Edited by knocker
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If the EPS remains constant it will be along these lines

gefs_z500a_5d_nh_65.thumb.png.efb11213ff21b5c6423e4bfb5615ed9d.png

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Looking at this evening's ecm one is struck once again at the amount of energy swilling about around the high pressure continually forcing it to adjust it's orientation, but that's all, illustrating it's strength

Early Saturday morning the frontal wave brings rain and quite strong winds to Scotland and the north of England. In fact quite breezy in many areas as the winds veer north west. The high then rebuilds but another front associated with a major trough in mid Atlantic just impinges on Scotland as it tracks north east And then back to the battle

t114.thumb.png.4e8c912bc6a5846b83e29f720c2d6160.pngt144.thumb.png.4817a7abe1143ef77624a64df393d2b9.pngindex.thumb.png.a4171b423df5e8cf2c985526ab58d15c.png

And of course over the Pacific

pacific.thumb.png.8b578db7133185076d4e5408b9e5a22d.png

Edited by knocker

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Thanks knocker..

The  last chart is an illustration of the jet strength?

Edited by northwestsnow

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25 minutes ago, northwestsnow said:

Thanks knocker..

The  last chart is an illustration of the jet strength?

Yup. a lot of forcing

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1 hour ago, knocker said:

If the EPS remains constant it will be along these lines

gefs_z500a_5d_nh_65.thumb.png.efb11213ff21b5c6423e4bfb5615ed9d.png

If anything it's a tad flatter

Edited by knocker
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wrong thread

Edited by The Eagle

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The EC46 update.

15-20 Atlantic amplification gone; some suggestion of the week ridge Iceland/ western Greenland. Temp a tad below average

20-25 Still pretty much a zonal westerly but stronger ridging Iceland/Greenland. Temps below average

25-30 More positive anomalies Iceland Greenland but still vortex lobe/trough N, Canada and a strong westerly upper flow, perhaps backing a tad over the UK.Temps below average.

30-25 Very similar

The trough remains to  the east throughout this period

 

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24 minutes ago, knocker said:

The EC46 update.

15-20 Atlantic amplification gone; some suggestion of the week ridge Iceland/ western Greenland. Temp a tad below average

20-25 Still pretty much a zonal westerly but stronger ridging Iceland/Greenland. Temps below average

25-30 More positive anomalies Iceland Greenland but still vortex lobe/trough N, Canada and a strong westerly upper flow, perhaps backing a tad over the UK.Temps below average.

30-25 Very similar

The trough remains to  the east throughout this period

 

Predominently NW airstream then Knocker? Sounds like a chilly month, perhaps a -0.5-1.0c variance from the average a possibility. 

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10 minutes ago, Radiating Dendrite said:

Predominently NW airstream then Knocker? Sounds like a chilly month, perhaps a -0.5-1.0c variance from the average a possibility. 

No I wouldn't say that RD. It's tricky with a basic westerly upper flow that weakens and backs a tad so transient surface winds from the NW >NE with passing systems quite likely but the tricky bit, for me anyway, is then how how the surface features pan out vis the Iceland ridging and increasing positive anomalies over that area and Greenland

Edited by knocker
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Here's how Brian Gaze from TWO sees the EC46 update

Quote

Out to Jan 20th it offers virtually nothing cold at all apart from a 1C anomaly in Scotland and Northern Ireland during week 4. Weeks 5 and 6 may be more promising but by then we're into Feb and it means the cold has been pushed back yet again.

1

https://www.theweatheroutlook.com/twocommunity/default.aspx?g=posts&t=19543&find=unread#post1065053

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4 hours ago, Summer Sun said:

It’s a mean of 51 runs ..... those feb returns are pretty impressive considering ........ without spreads you can’t deduce much from the mean T2 anomolys 

need to either wait for the pattern to get within eps or gefs range or rely on Exeter. - who’s current language (and has been for quite a while now) is ‘much colder’ for mid jan period and beyond 

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And the subtropical jet enters the fray but it's some block.  Be afraid, be very afraid

gfs_uv250_nh_39.thumb.png.f582c91a7daf0b440b8c0485ce5f644c.pnggfs_z500a_nh_39.thumb.png.3e9f4fe48f5b4e5a9aef9d74bb6afac0.png

Edited by knocker

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2 hours ago, bluearmy said:

It’s a mean of 51 runs ..... those feb returns are pretty impressive considering ........ without spreads you can’t deduce much from the mean T2 anomolys 

need to either wait for the pattern to get within eps or gefs range or rely on Exeter. - who’s current language (and has been for quite a while now) is ‘much colder’ for mid jan period and beyond 

You are talking about February I'll give you a tip forget about it. Trust me I saved you a millions.

Knocker enlighten me what is there to be afraid off . To me it looks like if there is a block we are too far west for any effect here. Different story for Europe.

 

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