Model Output Discussion - 18z 31/10/15 onwards

[johnholmes]

what do the last 2 paragraphs mean for the uk?cold or mild?

 

beware of trying to read too much into the NOAA daily assessments. Obviously they are top notch, their equivalent to our senior man at Exeter. But remember what they write is about their neck of the woods as is that from Exeter. Sadly, other than snippets from Fergie we have no access to a similar professional input as they do in America. 

Watch the long wave patterns for hints of changes downwind into the Atlantic and western Europe/UK. It takes time to be confident in how to use them but it does give a decent insight into what the upper pattern, which is what largely governs the surface patterns evolving, may do in the 5-15 day period.

[phil nw.]

The downward trend still very much on from the latest London ens graph

 

a cold 2-3days off the expected northerly and then a slight rise to near or just below normal to month end.

Indications of the UK lying more on the polar side of the jet after this week.

Edited November 15, 2015 by phil nw.

[Man With Beard]

Well the upcoming cold spell has progressed 24-36 hours since my last comment, and although some of the more extreme options seem less likely, I do see a broad consensus on a couple of cold days next weekend, and though I was initially sceptical of snow away from the north, I think there is actually potential for a shock snowfall over central areas and high ground in the south, as most output seems to have upgraded the cold, with the 850s reaching the magic -8C mark in many places.

Further on, small depressions get over the top of the flow and force a sinker - to me that is to be expected, I always find that the models see the block first and the disturbances later - what is necessary to turn it into a longer cold spell is the block getting directly north of us and a lower heights to the south west - some output has done this on the ensembles, so its not impossible. But for now, the favoured scenario is 2 days of snow potential especially north, a further couple of cold/frost and then a gradual warm-up - but no FI outcome being set in stone.

[SMU]

So as we start the engines on yet another 12z run I fully expect to see the UK upgrade to the full potential of the 850's in the northerly

Thats touching -10 for scotland & -7/-8 for the south -

Remember the 06z + 18z never get the polar heights as good as the 12 & 00z's

So as a result they are generally just slightly less amplified ( esp the 06z)

Also with this highly unusual blocking scenario from canada cojoining with an atlantic high - dont expect your run of the mill toppler....

S

[Polar Maritime]

So as we start the engines on yet another 12z run I fully expect to see the UK upgrade to the full potential of the 850's in the northerly

Thats touching -10 for scotland & -7/-8 for the south -

 

Sounds like you are describing last night's 00z run Steve. So more of the same perhaps?

Edited November 15, 2015 by Polar Maritime

[Costa Del Fal]

So as we start the engines on yet another 12z run I fully expect to see the UK upgrade to the full potential of the 850's in the northerly

Thats touching -10 for scotland & -7/-8 for the south -

Remember the 06z + 18z never get the polar heights as good as the 12 & 00z's

So as a result they are generally just slightly less amplified ( esp the 06z)

Also with this highly unusual blocking scenario from canada cojoining with an atlantic high - dont expect your run of the mill toppler....

S

Can you offer an explanation as to why this is the case please? Just interested as I thought the runs have the same parameters etc but fed with the newest/latest initial conditions?

[SMU]

I cant any more

* there was 2 reasons - 1 was that the 06z + 18z dont have the same amount of upper air data as the other 2

* but the main one was ( you have to just trust me on this one - the old model performance statistics page had the x4 GFS runs but RMS score at day 5 & 6 divided up into areas

It was sbout 7 or 8

* SHem

* Arctic

* Atlantic

* Russia

* States

* asia

* Africa

& maybe one or 2 others

I reviewed the arctic scores daily over 2-3 years & the 06z & 18z always scored very poor on the arctic area...

Hence my distain for these 2 runs in particular the 06z

Best

Steve

( yes PM the same)

Edited November 15, 2015 by Steve Murr

[bobbydog]

So as we start the engines on yet another 12z run I fully expect to see the UK upgrade to the full potential of the 850's in the northerly

Thats touching -10 for scotland & -7/-8 for the south -

Remember the 06z + 18z never get the polar heights as good as the 12 & 00z's

So as a result they are generally just slightly less amplified ( esp the 06z)

Also with this highly unusual blocking scenario from canada cojoining with an atlantic high - dont expect your run of the mill toppler....

S

to be fair though, a "run of the mill toppler" wasn't even on the cards for winter a couple of weeks back. now we're looking at a potential UK-wide (albeit brief) snow event, before winter has even started. things are looking up... Edited November 15, 2015 by bobbydog

[Polar Maritime]

An interesting read here re GFS fed data pre upgrade. So note Steves word.. http://www.americanwx.com/bb/index.php/topic/32149-gfs-12z-and-0z-runs-compared-to-6z-and-18z-runs/ Although i look at all runs i only use the 00z 12z data.

Edited November 15, 2015 by Polar Maritime

[SMU]

Gfs 850s through 120

06z scotland (126 ) was 0- -2c

12z scotland (120 ) is -8 - -10c !!!

Upgrades ðŸ˜

[peborant]

And even better than the upgrades is the fact that cold comes down our way earlier, which makes it more reliable. Ahhh Only a 100 odd hours to go! 

[Mucka]

This shortwave runner would give snow to the South but the sort of detail that changes run to run.

 

[Allseasons-Si]

What's this little chappie doing heading into to the SW of the BI,could be a snow dumper

 

 

this run is at least a 100 miles further west than the 06z,UPGRADES

Edited November 15, 2015 by Allseasons-si

[Costa Del Fal]

This shortwave runner would give snow to the South but the sort of detail that changes run to run.

 

Indeed it does, dumping a few cm for Wales, SW Mdlands into CS England. All rather conjecture at this stage anyway but certainly confidence starting to increase now of something cold enough for snow. Just 5 days really till it begins. With these setups things can change right up to the last minute though. However with low pressure just to our east, the probability of disturbances running around it are good.

[Mucka]

UKMO still having none of it.

 

[Mucka]

Some interesting changes upstream, both near and far.

Is this the start of a repeat attempt?

 

Edited November 15, 2015 by Mucka

[Man With Beard]

UKMO still having none of it.

 

Doesn't look as pretty as GFS 12Z but there still seem to be disturbances with a northerly flow following - probably wintry for some on Saturday going by this?

[shaky]

UKMO still having none of it.

 

to be fair mucka that ukmo chat looks much better than this mornings!!also with each run it keeps amplifying the high in the atlantic!!playing catch up i think!!

[MR EXTREMES]

very interesting runs tonight but the most striking is the heights around siberia massive squeeze on the vortex still looking cold at the end of the week but even though the coldest air departs after a couple of days the surface air wont bring temps above more likely to be slighty below.

 

but the most interesting part is watching the vortex get a beating ala over the place.

 

still very possible the cold at the end of the week could shift the coldest air to our east although i dont think the outputs are nailed got a sneaky feeling the heights near greenland could either be placed to the north between greenland or iceland or topple over the uk.

 

either way the heights to our south are being squeezed southwest back towards the azores.

 

but both ukmo and gfs have the cold here by t120 but the siberian high looks like a growing monster high.

 

i wonder if this will be good going into winter proper.

 

 

and the squeeze is on

 

looking again surely the Siberian high is going to push the vortex back towards Canadian side?

Edited November 15, 2015 by emotional rollercoaster

[Mucka]

Doesn't look as pretty as GFS 12Z but there still seem to be disturbances with a northerly flow following - probably wintry for some on Saturday going by this?

 

I think you could forget any chance of snow for low lying England with that UKMO run, it never gets a good Northerly flow to drag the cold upper air down and the eventual flow is NW so not cold enough. The far East would see air a little colder but very doubtful it would support snow to low lying areas ,

 

 

 

Back to something more encouraging. GFS 12z attempting to quickly rebuild heights toward Greenland. 

 

 

and check out the amplification upstream, very encouraging if it becomes a trend.

 

Edit.

@shaky re UKMO. yeah very slow improvement but still poor for snow prospects IMO

 

GFS FI

 

Polar Vortex under assault.

 

 

Doesn't necessarily mean a cold pattern setting up for UK end Nov early Dec but it would massively increases the chances,

I'm sure Steve and a few others will be very pleased with this NH profile if it becomes a trend. May well mean the upcoming cold snap is a mere apertif before the main event.

Edited November 15, 2015 by Mucka

[Allseasons-Si]

Yes Mucka,i can see that that trough would dive SE into Spain allowing a easterly feed into the uk,a much better run

[Ice Day]

At 238 and this chart is stacked full of potential.  The PV is all over the place with the majority over the Asian side, which is different from last year if nothing else!

 

[Summer Sun]

GFS gives the chance of snow right down to the south on this run

 

 

Day time maximum temps still below 0c at 15:00 for some parts

 

 

[Allseasons-Si]

Easterly incoming

 

 

all just for fun of caurse at this stage but it is nice to look at though.

Edited November 15, 2015 by Allseasons-si

[pip22]

Easterly incoming

 

gfsnh-0-300.png

 

all just for fun of caurse at this stage but it is nice to look at though.

That Easterly came from the mild source straight from the Med.