Model Output Discussion 12z 04/12/2012

[Southern Storm]

They're compiled on weekdays by the duty forecaster, at weekends though they're computer generated.

OK and nice to know that have that all important human input!

But as others have said, we can't put all our eggs in one basket.

having said that, if people paid more attention

To this type of output we'd have lot less moaning on here!

Many thanks TM24

Edited December 4, 2012 by thunderman24

[snowking]

Full ECM Ensembles:

Mean still sub zero in de bilt in the medium term

Looks like a similar sort of split to last night, so we certainly havn't gone backwards with todays 12z's

SK

[fergieweather]

V V quick comment re snow tonight - tomorrow AM. New output from UKV, MOGREPS, NAE and EC offering varied solution(s) and huge uncertainty now in areal scope and amounts - i.e., SE / Home Counties / London area / SE could see more in some new progs (2cm or more in places) whereas other solutions in the suite suggest more focus to NW of London (Chilterns, over to Cotswolds etc). MOGREPS more widespread across fair swathe of central-S England. Signal now hinting towards a more easterly bias generally, away from W Country other than E Glos / N Wilts, but this detail not to be trusted. Hence much, much to play for. A nightmare forecast frankly. Anyway, gotta dash.

[Zenarcher]

Earlier I done an analysis of the UKMO and the changes it's seen so I've just completed one for the ECM,

GFS 18z is starting to roll out now and after looking at the GFS cluster maps most agreed on the Atlantic looking weaker in FI so lets see what the 18z can do.

Edited December 4, 2012 by weathermaster

[john mac]

V V quick comment re snow tonight - tomorrow AM. New output from UKV, MOGREPS, NAE and EC offering varied solution(s) and huge uncertainty now in areal scope and amounts - i.e., SE / Home Counties / London area / SE could see more in some new progs (2cm or more in places) whereas other solutions in the suite suggest more focus to NW of London (Chilterns, over to Cotswolds etc). MOGREPS more widespread across fair swathe of central-S England. Signal now hinting towards a more easterly bias generally, away from W Country other than E Glos / N Wilts, but this detail not to be trusted. Hence much, much to play for. A nightmare forecast frankly. Anyway, gotta dash.

Great stuff ian thanks for that. Oh well could be some surprises tomorrow morning.

[bluearmy]

Don't be such a grump!

Yes I just did, off to shoot a couple of reindeer now as you've harpooned my Xmas spirit!

Back on topic....... yes they're not always accurate but given current trends they could be if things go well!

Tbh nick, its not the mean lw pattern thats the issue, just how the day to day features set up within it and what that means for our little island. Naefs spreads week 2 are very interesting in placing a mean little feature over the south of the uk for a couple, of days. More noteworthy is the fact that naefs week 2 is the first ext ens output this winter that actually shows the advance of lower uppers via the spreads. thats almost the final confirmation for me that we are gong to see an easterly next week. lets see it repeat on the 00z. Btw, the mean ridge on naefs, not surprisingly headed from scandi to our north later in the run. Signs that the movement of the vortex from canada to siberia may result in a split rather than a displacement.

[Southern Storm]

V V quick comment re snow tonight - tomorrow AM. New output from UKV, MOGREPS, NAE and EC offering varied solution(s) and huge uncertainty now in areal scope and amounts - i.e., SE / Home Counties / London area / SE could see more in some new progs (2cm or more in places) whereas other solutions in the suite suggest more focus to NW of London (Chilterns, over to Cotswolds etc). MOGREPS more widespread across fair swathe of central-S England. Signal now hinting towards a more easterly bias generally, away from W Country other than E Glos / N Wilts, but this detail not to be trusted. Hence much, much to play for. A nightmare forecast frankly. Anyway, gotta dash.

Thanks Ian

And in this post is a lesson to everyone, the models are having problems within the next 48 hours let alone a week away!

We could have some very seasonal weather on our doorstep but are we too focused on fi ?

Good times.

Edited December 4, 2012 by thunderman24

[Paul]

Don't usually do this sort of thing, but anyone wanting to use NW Extra, the NMM model, the 5 minute/weather type radar etc this winter, we've a number of special offers available with the offer code WINTER12

http://www.netweathe...remium.pl?sess=

[Weather Boy]

V V quick comment re snow tonight - tomorrow AM. New output from UKV, MOGREPS, NAE and EC offering varied solution(s) and huge uncertainty now in areal scope and amounts - i.e., SE / Home Counties / London area / SE could see more in some new progs (2cm or more in places) whereas other solutions in the suite suggest more focus to NW of London (Chilterns, over to Cotswolds etc). MOGREPS more widespread across fair swathe of central-S England. Signal now hinting towards a more easterly bias generally, away from W Country other than E Glos / N Wilts, but this detail not to be trusted. Hence much, much to play for. A nightmare forecast frankly. Anyway, gotta dash.

So, interestingly, as was being modelled by the GFS earlier today (and it was promptly slated for not being the best short range model). That run had the greatest concentration/risk of snow in a strip to the north of London from north Essex to Oxfordshire (including me!).

...but it sounds like it could fall anwhere from the Midlands southwards tonight, although presuming the greatest risk to being central parts rather than the south coast.

M4 snow boundary anyone?

[Lee Smith]

is a split vortex better than a displacement guys

[snowking]

Tbh nick, its not the mean lw pattern thats the issue, just how the day to day features set up within it and what that means for our little island. Naefs spreads week 2 are very interesting in placing a mean little feature over the south of the uk for a couple, of days. More noteworthy is the fact that naefs week 2 is the first ext ens output this winter that actually shows the advance of lower uppers via the spreads. thats almost the final confirmation for me that we are gong to see an easterly next week. lets see it repeat on the 00z. Btw, the mean ridge on naefs, not surprisingly headed from scandi to our north later in the run. Signs that the movement of the vortex from canada to siberia may result in a split rather than a displacement.

Yep the first hints of the retrogression of the HP to Greenland now from the NAEFS

Also a pretty obvious signal for an undercut

SK

[karlos1983]

So, interestingly, as was being modelled by the GFS earlier today (and it was promptly slated for not being the best short range model). That run had the greatest concentration/risk of snow in a strip to the north of London from north Essex to Oxfordshire (including me!).

...but it sounds like it could fall anwhere from the Midlands southwards tonight, although presuming the greatest risk to being central parts rather than the south coast.

M4 snow boundary anyone?

I am going to request the M4 is relocated to N.France, drives me mad!!

[TheGrittersAreOut]

Hi all,

I don't ever post on here but this comment from OldMetMan caught my eye:

... the models are showing very high pressure developing over N Russia - common enough this time of year - but the cooling in that part of the world is continuing apace (judging by the way the Russians were caught out by very heavy snow over the weekend, when they are supposedly well geared up to deal with, so it must be unusual).

I travel a lot with my job and last week I was in Moscow when all the snow fell. It started snowing on the Wednesday and then snowed (a very fine snow but continuous) for 2 days solid. While it's true this caused chaos on the St Petersburg to Moscow motorway the traffic in Moscow is always chaotic and actually seemed quieter than normal on the Thursday when the snow was well over 40cm throughout the city. They have 12,000 snow ploughs in Moscow so they keep the streets clean!

But why is this useful for the Model Output Discussion - in talking to the Russians who were hosting our visit they said such snow was very common 15-20 years ago but since then Moscow has had little snow before Christmas. They viewed this year's weather as similar to 1990s and earlier. It's clear this winter's weather (as demonstrated by the models) is quite unusual.

By Friday it started raining ice (it seemed to be water in the air but was ice by the time it hit the ground). Something I have rarely seen in the UK. On another note, two weeks ago I flew across the Atlantic and the jet stream was further south than I have ever seen it at this time of year (I go to the US in the same week of November every year).

Cheers,

TheGrittersAreOut

P.S. Excellent, fascinating forum by the way

Edited December 4, 2012 by TheGrittersAreOut

[Timmytour]

Lows a bit deeper over Iceland at T81...stil to far north for me but with slightly higher pressure over Greenland hopefully it will get bounced further south east on this run and pull in the cold air quicker and with more conviction

[karlos1983]

Lows a bit deeper over Iceland at T81...stil to far north for me but with slightly higher pressure over Greenland hopefully it will get bounced further south east on this run and pull in the cold air quicker and with more conviction

Struggling to spot the diff at +96, if anything it seems slightly further east?

[-uksnow-]

Struggling to spot the diff at +96, if anything it seems slightly further east?

To my untrained eye everything seems to be (although not by much) a bit further west?

[Paul]

Struggling to spot the diff at +96, if anything it seems slightly further east?

You can compare directly on the GFS viewer - just load up the same chart on the right hand side drop down and click the prev run button to display the 2 most recent runs next to eachother

http://www.netweathe...tion=nwdc;sess=

[snowking]

Struggling to spot the diff at +96, if anything it seems slightly further east?

Id say the opposite

gfsnh-0-108.png

gfsnh-0-114.png

Things in our part of the world slightly further NW

SK

[Ice BIast]

To my untrained eye everything seems to be (although not by much) a bit further west?

Agreed, and the high near the UK is postioned differently ridging NW rather than NE, so a bit different to the ECM and UKMO.

Could be a good run this.

Edited December 4, 2012 by lce Blast

[pyrotech]

Just seen complete 18z GFS and its a perfect example of why you compare run to run not different times.

Difference in fi is High Scandi moves Slightly further North East but stronger, and Low iceland / Greenland much deeper.

But this run is very similar to last nights 18z and 12 z yesterday and today very similar. Looking at 16th for this.

GFS is consistant for each run time, but each different run is completely different.

Choose your run time, I suggest to see which run most resembles ECM . Lots of uncertainty over a just a few days but consistancy in runs if compared time v time

[Mucka]

Latest NAE upgrades the snow risk early hours through tomorrow morning with an area of snow moving Se through the Midlands and into SE England.

[Southern Storm]

Sorry on tablet so unable to post charts but one thing I have notice is that the 850 temperatures out to the east are often underestimated By the models,

even as early as +12 you can see this, hence the met having a hard time atm.

Edited December 4, 2012 by thunderman24

[Cheshire Freeze]

Don't usually do this sort of thing, but anyone wanting to use NW Extra, the NMM model, the 5 minute/weather type radar etc this winter, we've a number of special offers available with the offer code WINTER12

http://www.netweathe...remium.pl?sess=

Hi Paul, what sort of discounts are you offering. I'm very interested in the 6 month lite subscription.

Thanks!

[karlos1983]

Agreed, and the high near the UK is postioned differently ridging NW rather than NE, so a bit different to the ECM and UKMO.

Could be a good run this.

Yep, looking much better at +114, my bad.

[ITSY]

an upgrade by +120!!

better, earlier linkup, higher heights, low more south.