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Model Output Discussion 25/11/2012 12Z onwards


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Posted
  • Location: Banned from Posting, Not happy
  • Location: Banned from Posting, Not happy

Yes

http://www.wetterzen...s/Rtavn1741.png

as long as you see that patch of 552 Pressure were fine. looksing good for FI

S

If anything the Arctic high has pivoted and aligned more SW.. having been more NW / SE previously. I think this is the most significant development.

As the ridge SW keeps the low to the west of the greenland southern tip, sending any breakaway lows SSE down towards madeira.

post-6128-0-10257600-1353862568_thumb.jp

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Posted
  • Location: Bedford
  • Location: Bedford

there always has to be a party pooper and today its the GEM, how can that be so different, if that were to happen it would be just bog standard weather and all this fuss will be for nothing

also nogaps is shocking too, thank god GFS and UKMO don't show this, i bet gavin hopes the GEM is right lol

Edited by Snowy Easterlies
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Posted
  • Location: st albans
  • Location: st albans

Note the increasing arctic blocking as time is ticking down. Ukmo at day 6 seems to have all avenues blocked around svaalbard. Given how poorly this area is likely to be modelled, I suspect we have more upgrades to come!!!

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Posted
  • Location: hertfordshire
  • Location: hertfordshire

Well it looks like Mr.Murr was right

The gfs has backed down this afternoon and followed the UKMO

The UKMO is coming out of all this very very well and is leading the way!

The 06z operational was a closer match to the UKMO at t144 than the 12z I think.

But no matter the trend is the same HLB to our north with a northeasterly airflow

becoming increasingly more east,northeasterly and also becoming colder and

colder.

The UKMO is the model to watch I think with the other two playing catch up,

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Posted
  • Location: Ribble Valley
  • Location: Ribble Valley

Note the increasing arctic blocking as time is ticking down. Ukmo at day 6 seems to have all avenues blocked around svaalbard. Given how poorly this area is likely to be modelled, I suspect we have more upgrades to come!!!

If it's poorly modelled then how do we know it's being modelled correctly now BA, a genuine question by the way.
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Posted
  • Location: Liphook
  • Location: Liphook

Note the increasing arctic blocking as time is ticking down. Ukmo at day 6 seems to have all avenues blocked around svaalbard. Given how poorly this area is likely to be modelled, I suspect we have more upgrades to come!!!

As I've been saying, the models nearly always under-estimate the extent of blocking up there. A slow brewer but after several half-baked efforts, the GFS 12z does give us the full beans and surface cold to boot.

PS, we don't 7 of 9, but if we know that current conditions higher in the atmosphere are supportive of a fractured PV and heights building at frequant bursts, then you've got to think that its more likely to upgrade on that front than downgrade.

Edited by kold weather
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Posted
  • Location: Gilesgate Moor, Durham City
  • Location: Gilesgate Moor, Durham City

What conditions would we be seeing from the UKMO 120 and 144? As there are fewer types of charts available compared to GFS, for example, I find it harder to tell.

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Posted
  • Location: Nr Chelmsford, Essex
  • Weather Preferences: Hurricanes, Thunderstorms and blizzards please!
  • Location: Nr Chelmsford, Essex

next 5 days will involve viewing the models from behind the sofa then....

That's where I am now!!!

What I find amazing having frequented here for many years, is that every modelled cold spell usually involves one of the major three models going off on it's own! Still, all adds to the roller coaster I suppose. To my very much untrained eye, I think the UKMO has remained the most consistent over the last few days, it's not wobbled much at all and hopefully that trend will continue

Edited by Ice Day
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What conditions would we be seeing from the UKMO 120 and 144? As there are fewer types of charts available compared to GFS, for example, I find it harder to tell.

Hi Nick at 144 on the UKMO

http://www.meteociel.fr/ukmo/runs/2012112512/UW144-21.GIF?25-17

See the line across the the UK ( dark blue ) that runs along the 1010MB contour so thicknesses around 522 DAM

THe 522 thickness at 500 MB is historically what the METOFFICE used to forecast snow for the uk ( before partial thicknesses came in at 850 MB)

I would say snow showers or longer spells of sleet/snow- for you

S

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Posted
  • Location: Gilesgate Moor, Durham City
  • Location: Gilesgate Moor, Durham City

Hi Nick at 144 on the UKMO

http://www.meteociel...44-21.GIF?25-17

See the line across the the UK ( dark blue ) that runs along the 1010MB contour so thicknesses around 522 DAM

THe 522 thickness at 500 MB is historically what the METOFFICE used to forecast snow for the uk ( before partial thicknesses came in at 850 MB)

I would say snow showers or longer spells of sleet/snow- for you

S

Much appreciated, Steve. I'm still learning to interpret those UKMO ones without 850 charts!

Trying to read from the 120 to 144, would I be right in thinking that the 120 would have little snow, (too N'ly and uppers not quite there), with the snow arrivind maybe on 132?

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Much appreciated, Steve. I'm still learning to interpret those UKMO ones without 850 charts!

Trying to read from the 120 to 144, would I be right in thinking that the 120 would have little snow, (too N'ly and uppers not quite there), with the snow arrivind maybe on 132?

yes winds swinging NE - a trough arriving from the East.- rain turning to snow by 132-

I am actually not fussed by either runs for the SE tonight as the GFS will get the Surface temps very low by the weekend from the Northerly...

then the PPN arrives.

S

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GFS ensembles are still a complete mess beyond just +144. Some are looking like the GEM and NOGAPS. Big scatter suggesting considerable uncertainty still. The 12z are warmer at day 7 than the 06z ensembles.

06z

gens-21-0-174_dsz2.png

12z

gens-21-0-168_wys4.png

Quite a bit warmer.

(upper air mean)

Edited by Barb-
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Posted
  • Location: Gilesgate Moor, Durham City
  • Location: Gilesgate Moor, Durham City

GFS ensembles pretty useless this evening. So many different divergences from the op run between 96 and 120 hrs.

Isn't that in itself far from useless though? In the sense that it could be seen as showing how many options there still are? As ever, caution needed. ;)

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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

obessions with sortwaves creeping in again.

this run is heading in a perfect direction game on.

some have permanent obsessions with short waves in winter!

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I'm not buying it personally until we get at least some ensemble and NAEFS agreement.

Isn't that in itself far from useless though? In the sense that it could be seen as showing how many options there still are? As ever, caution needed. tease.gif

Well that's the main point of ensembles, to determine the level of uncertainty and at the moment they are suggesting a high degree of uncertainty.

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Posted
  • Location: Bexleyheath (south), Kent
  • Location: Bexleyheath (south), Kent

some have permanent obsessions with short waves in winter!

When is a short wave a short wave and not a low pressure system?

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Posted
  • Location: Co Dublin, Ireland
  • Location: Co Dublin, Ireland

Isn't that in itself far from useless though? In the sense that it could be seen as showing how many options there still are? As ever, caution needed. tease.gif

I am being cautious. The GFS op run is brilliant but there are so many other outcomes on the ensembles at such a short time frame they can't be used for guidance to any great extent.

Also my "concern" on the UKMO is that the block to the west looks like it's not going to hold after 144hrs.

UN144-21.GIF?25-17

Too much energy south of GL.

Edited by The Eagle
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Posted
  • Location: Longwell Green, near Bristol
  • Weather Preferences: Storms, Gales, frost, fog & snow
  • Location: Longwell Green, near Bristol

Before the cold spell, we have one more rain event to watch for.

The GFS suggests the heaviest rain to be across North Wales & Northern England this time , with lighter, but still unwelcome rain across the south;

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121125/12/12/ukprec.png

The UKMO similar, with most if the country seeing some rain in the next 12 hours.

http://www.meteociel.fr/modeles/ukmo2.php?nh=0&ech=12&carte=1594

http://www.meteociel.fr/modeles/ukmo2.php?nh=0&ech=18&carte=1594

Then once that system clears into the North Sea, things quieten down somewhat, with dry weather for most of us for the most part of the upcoming working week;

http://www.meteociel.fr/modeles/ukmo2.php?nh=0&ech=96&carte=1021

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=96&mode=0

Just a few showers towards the south & east likely. Temperatures at this point slowly coming down towards something below the seasonal average;

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121125/12/96/ukmaxtemp.png

Then as we progress into next weekend things really start becoming interesting for a cold lovers point of view.

Temperatures becoming colder & colder as lower thickness values and lower 850's encroach from the N/NE;

http://www.meteociel.fr/modeles/ukmo2.php?carte=1021&ech=144&nh=1&archive=0

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=144&code=code&mode=0&mode3h=0&runpara=0&carte=1

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=144&code=0&mode=1&carte=1

Temperatures just above freezing in the south, Ice days possible for some in the north;

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121125/12/144/ukmaxtemp.png

Along with a band of rain & sleet around coasts, snow inland moving slowly S/SE;

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121125/12/144/prectypeuktopo.png

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121125/12/144/uksnowrisk.png

This still lingering in the south & south west 24 hours later;

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121125/12/168/uksnowrisk.png

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121125/12/168/prectypeuktopo.png

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121125/12/168/hgt500-1000.png

Notice a strong jet stream way south of the UK, down in the Med, allowing the colder air to sink south over the UK;

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121125/12/168/hgt300.png

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121125/12/168/npsh500.png

I won't go no further now as we are entering a very unreliable FI period from there onwards.

So a slow decline in temperatures likely throughout the working week, with the potential for snow increasing as we enter next weekend just about sums it up for now.

Specific snow threats for specific locations are likely to change throughout the week, so don't look too much into the threat for your back yard for now, just focus on the potential for the UK in general.

Enjoy all. Interesting times ahead. :)

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Posted
  • Location: Straiton 145m asl
  • Location: Straiton 145m asl

Hi I am a new member of the forum, I hope all are well.

A question for Steve Murr are we looking at a NE/E winds towards the weekend or more of a Northerly, here in SE Scotland in the central belt we need more of a NE feed for showers to come inland?

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