Winter Model Discussion 18Z 16/1/13 onwards.

[Mini tiger]

Still a lot of uncertainty over the snow on Friday. Latest News 24 forecast has 8oC just south of Bristol and the worst of the snow

in a line from Brighton up to Liverpool. Why are the temps so high when the 528 dam line is not far to the east over the eastern half of

England

[chionomaniac]

All rain to snow ratio posts will be deleted

Please keep on topic

[Cloud 10]

Come on guys,size isn't everything!

The 18z has backed everything west a bit,with the front stalling over the western half of the UK,before

dying out which means more places stay cold.

[pages]

At 18z still different to the euros with that massive low. The more knowledgable no doubt will spot small improvements In the medium term.when the gfs is wrong it takes small steps back towards the rest over a few runs rather than a big jump in my opinion

[Snowly does it]

-5 850s are retreating north at t96, from the Wash across - presumably still cold enough in a continental flow for those south if the line??

[Mini tiger]

GFS 18z a much better run for keeping the cold locked in, it shoots off to the south quickly. However the snow may not reach as far east ?

Also latest fax for Sunday is a huge upgrade for southern england, with a lot of snow in the south east

Edited January 16, 2013 by Mini tiger

[swfc]

at 96-hours i see this going the way of the 12z.pv and low orientation at the tip of greenland almost identical

[Timmytour]

Saturday evening....impressive looking chart iro snow for London......

BUT.........that's a chart that tells you the chance of any precipitation being snow. So that tells us that whatt falls in London will be snow...the next question is how much..Precipitation chart for the same time...

Not much!

So don't go confusing the pinks on the snow charts for loads of snow for your area!

[Don]

Still a lot of uncertainty over the snow on Friday. Latest News 24 forecast has 8oC just south of Bristol and the worst of the snow

in a line from Brighton up to Liverpool. Why are the temps so high when the 528 dam line is not far to the east over the eastern half of

England

I think that 8oc max is for Plymouth. Will be much colder than that in Bristol!

[Basil_Fawlty_Walks_On_Water]

in a situation like this, with fairly cold uppers and in many places a non-marginal situation, 1mm=.8cm is probably roughly right.

In more marginal situations, it can be more like 1mm=.5cm. All depends on the dendritic growth... Ratios of 1mm=1cm will need 850mb temps of <-8 in most cases. Colder than that and you can see ratios as high as 1mm=2cm.

[BARRY]

I think that 8oc max is for Plymouth. Will be much colder than that in Bristol!

net weather temp for plymouth is 2 max

[Ice Day]

Low appearing to the SW of Ireland at 120. Nice to see that head into the channel!

[Paul T]

GFS 18z a much better run for keeping the cold locked in, it shoots off to the south quickly. However the snow may not reach as far east ?

Also latest fax for Sunday is a huge upgrade for southern england, with a lot of snow in the south east

That doesnt show a massive upgrade with a lot of snow in the SE. Bit misleading for some.

Its does indicate a decent angle of attack of the approaching low however.

[Matty M]

NAE and GFS 18z both take the front further west.

Lets hope this trend continues in the morning (IMBY )

[samadamsuk]

evening all

latest gfs looks like it's reloading the pattern from monday and atempting to reinforce the block, with deep cyclogenesis to our NW again - looks like another slider for early next week then a renewed easterly from what i can tell. Pretty amazing jet configuration at t84 though, the jet being shredded north and south as it comes up against the block, so any breakdown or reset is just one option i supose.

Happy sledging all!

Sam

[Don]

net weather temp for plymouth is 2 max

Maybe, but the temperature on that BBC weather map is showing 8oC for Plymouth. Lets hope that Netweather's temp prediction ends up being closer to the mark! This is all subject to change anyway (Netweather, BBC/Metoffice etc).

Edited January 16, 2013 by Don

[Snowly does it]

I may be being a bit simple, but isn't it rather marginal by Sunday for those in the South and SE and EA? 850s are at -3 or -4, and whilst the dew points will be low, could there not be a wintry mix? Or is snow under those circs more likely?

[Mini tiger]

That doesnt show a massive upgrade with a lot of snow in the SE. Bit misleading for some.

Its does indicate a decent angle of attack of the approaching low however.

oh sorry.. I was looking at the low over E Sussex.

[Ice Day]

Looks a bit of a mess at 138. Not sure where this is going?

[Paul T]

That Low is heading in a slightly different (North East) direction that the 12z, as attached...

Edited January 16, 2013 by Paul T

[Ian Brown]

Having sent the shortwave to Biscay at T126, the GFS is trying to work out how to get the Azores High into the UK. Bin.

[dbaloo]

Hi all.i thought as it was quiet in here i would take the chance to ask that on the wales discussion board there is talk and apparently Ian F has suggested this as well that there may be a "breakpoint" as the front moves in?i am just wondering if anybody has any info on this from the charts as I have no idea where to look.

Many thanks and sorry if this is posted in the wrong place

[Cloud 10]

New 120hrs fax= undercutmageddon!

[swfc]

Third gfs run showing poor pressure towards iceland and atlantic on the door step at 144-hours?im sceptical of its speed westwards but not to be totally ignored imo

[snowice]

NAE and GFS 18z both take the front further west.

Lets hope this trend continues in the morning (IMBY )

yes across to Dublin!