Spring Model Discussion 18Z 9/3/13 onwards....

[Tim Bland]

Can't help but feel it won't be cold enough for snow in most areas after Thurs. Pennines and moors etc could see some along with Scotland but for the populous areas of the midlands south, it looks too marginal.

[Gustywind]

I agree tim, I get the fact that dew points may be ok but surely at this time of year we need better upper air temps than -4 for snow away from high ground? Cold rain or sleet I'd have thought, with snow on northern hills only.

[chris55]

A random question...where in London is the ensembles taken? It has 100% snow risk for te next 48hrs and a high precip spike..I'd presume it's south of the Thames? I very much doubt the precip will get north of the m4 / Thames

This has often come up in discussions over the years, usually we hear that the Wetter ensembles have a grid point way south of London. If we compare the Meteoceil set with the Wetter set you can clearly see the difference in ppn spikes, with the Wetter version with up to 10mm showing!! This suggests that the Wetter version is a lot further south than London City centre. So overall I am not really sure how accurate either are at locating London "right in the middle" so to speak.

Wetter

http://www.wetterzentrale.de/pics/MT8_London_ens.png

Meteo

http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=306&ext=1&y=141&run=12&ville=Londres&runpara=0

[winterof79]

http://www.meteociel...M1-120.GIF?10-0

An awsome chart if you want snow for central & North/ North western Areas-

S

Thats what we are here for Steve.Long way to go though.

Not sure about the snow theory though http://www.meteociel.fr/modeles/ecmwf/runs/2013031012/ECM0-120.GIF?10-0

[lord stratus]

Thats what we are here for Steve.Long way to go though.

Not sure about the snow theory though http://www.meteociel.fr/modeles/ecmwf/runs/2013031012/ECM0-120.GIF?10-0

If that chart verified it would be a mainly rain event uk wide with hill snow.

[The Northern Ramper]

But if that corrected south & west I would be dancing a happy dance as it would mean snow for most.

No it wouldn't, south west and that's it.

[-uksnow-]

http://en.vedur.is/weather/forecasts/atlantic/#type=prec

ECM actually gives the South coast a fairly good event.

[snowking]

I agree tim, I get the fact that dew points may be ok but surely at this time of year we need better upper air temps than -4 for snow away from high ground? Cold rain or sleet I'd have thought, with snow on northern hills only.

Hi GW

The only requirement for snowfall from the 850mb temps is sub zero, its all to do with the context.

The reason the -6c figure is usually bounded around is due to the average lapse rate as you move down the atmosphere to the surface. However, the flow, thicknesses and heights (along with countless other variables) affect the temperature lapse as you move down the troposphere.

Whilst under a long sourced northerly, with a lot of track of the flow over warmer seas in the atlantic, there is more modification of the flow, meaning that in order to get the right conditions for snow at the surface, the temps higher up have to be colder (as this air mass warms as we get closer to the surface), under a flow sourced from a close-by landmass, and a shallow flow at that (indicated by low heights), not only is our weather based closer to the surface overall, but it means that the temperature warms less quickly as you move down the atmosphere (given less modification from a sea track).

So, as long as you have sub zero 850mb temps, its then down to the conditions closer to the surface

SK

[bluearmy]

I agree tim, I get the fact that dew points may be ok but surely at this time of year we need better upper air temps than -4 for snow away from high ground? Cold rain or sleet I'd have thought, with snow on northern hills only.

Low thicknesses and slack flow will promote snowfall. However, it will be pretty marginal midlands south. In dec/jan/early feb, this would be an absolute snowfest of a period upcoming. C'est la vie. Methinks the scots are looking at a pretty extended wintry spell.

[shotski]

No it wouldn't, south west and that's it.

If you say so Buddy

[ITSY]

If that chart verified it would be a mainly rain event uk wide with hill snow.

No it wouldn't. i Don't know your location, but for the midlands northward (given thicknesses, dps, air temps, intensity - not just uppers, which will be fine in any case north of brum) it would be snow.

it wont happen like that but people really need to think twice before posting useless comments.

[Gustywind]

Thanks snowking for the explanation, fingers crossed you're right.

[bluearmy]

No it wouldn't. i Don't know your location, but for the midlands northward (given thicknesses, dps, air temps, intensity - not just uppers, which will be fine in any case north of brum) it would be snow.

it wont happen like that but people really need to think twice before posting useless comments.

No need to feed 'the troll'.

i wonder how much further sw the shortwave from the nw can trend?

[Captain Shortwave]

No need to feed 'the troll'.

i wonder how much further sw the shortwave from the nw can trend?

Same, wouldn't take much correction and then we could have another channel low on our hands. Though of course things would be more marginal than the low crossing to our south now.

[bluearmy]

The ecm ens trough is fantastically deep for march. sub 528 mean heights across most of he uk throughout. Waiting to see it on meteociel with the purples.

[Chris W]

GFS going through cold phases and then ending up with a bit of a Spanish plume right at the end, from a brief glance I've just had.

[bluearmy]

Following the ecm ens mean run thru to day 10 on a hemspheric view, you'd be hard pushed to draw much better sypnotically.

[lord stratus]

No need to feed 'the troll'.

i wonder how much further sw the shortwave from the nw can trend?

How can my post be regarded as trolling just because it doesn't suit certain cold fans. I comment on what I see and use past experience. The more experienced members in here know that the uppers will not be that cold in the set up shown, hence my comment.

[winterof79]

This may be deleted,but i would just like to emphasise how cold the temperature/wind will be over the next 12/24 hours.

It has become common place to use terms like"extremely and bitterly" cold over the last few years .When really it has not been.Generally the media through t.v.

The METO have worded it correctly this time

Bitterly cold, with a widespread frost and risk of snow.

This Evening and Tonight:

Snow, accompanied by a strong and bitterly cold northeasterly wind, will affect some southernmost parts of England, bringing a risk of significant falls to parts of Devon in particular. Scattered snow showers elsewhere, heaviest and most frequent further east.

Monday:

Further snow is likely affect southern counties of England, with snow showers continuing elsewhere. A significant, even severe windchill, is likely in the south. Less windy, and brightest further north.

Outlook for Tuesday to Thursday:

Remaining cold, with the focus of the snow showers transferring to eastern coasts. Winds will also slowly ease as the week progresses. Many areas should see some sunshine too.

Issued at: 1600 on Sun 10 Mar 2013

Hopefully in future we may reserve the extreme terms for when they are needed.

http://expert-images.weatheronline.co.uk/daten/proficharts/en/nae/2013/03/10/basis12/ukuk/t850/13031118_1012.gif

[Ian Brown]

How can my post be regarded as trolling just because it doesn't suit certain cold fans. I comment on what I see and use past experience. The more experienced members in here know that the uppers will not be that cold in the set up shown, hence my comment.

I'm not sure how you can be sure of that given that the PFJ cannot progress very far North given the synoptics and cold air is already in place at the surface.

[bluearmy]

How can my post be regarded as trolling just because it doesn't suit certain cold fans. I comment on what I see and use past experience. The more experienced members in here know that the uppers will not be that cold in the set up shown, hence my comment.

Because you repeatedly make incorrect statements. doesnt matter if its mild or cold. If they are incorrect, they are incorrect. I recall the other morning a post which consisted of something like 'you lot get sucked in every time'. That wasnt very constructive in a mod discussion thread and it wasnt right in any case. When conditions become wintry, we get new people reading this thread who are inexperienced and wont know who's info is more/less reliable. Thats why now more than ever, ts important that incorrect statements are highlighted.

latest naefs just as impressive with the mean trough as ecm. knife edge stuff for snowfall and i suspect local variations will be evident, especially where any altitude is involved. The further north , the more likely you are to hang on to wintryness throughout the next 10 days and perhaps beyond.

[bradymk]

A severe event over the next 24 hours for the Channel and Northern France. Some places in northern France may see 40cm, maybe even 50cm locally. This together with a v strong NE wind makes the event even more severe, sig wind chill and travel disruption significant. 100/150 miles north and this would of been southern england. Embedded cold and low thickness on EC det and ens, if only it was January if your a cold lover. Cold weather looks to prevail for a while according to GEFS and EC ens although not as cold as the next couple of days. Could be cold and wet, but cold and white for higher ground, especially central and north.

[LomondSnowstorm]

Because you repeatedly make incorrect statements. doesnt matter if its mild or cold. If they are incorrect, they are incorrect. I recall the other morning a post which consisted of something like 'you lot get sucked in every time'. That wasnt very constructive in a mod discussion thread and it wasnt right in any case. When conditions become wintry, we get new people reading this thread who are inexperienced and wont know who's info is more/less reliable. Thats why now more than ever, ts important that incorrect statements are highlighted.

latest naefs just as impressive with the mean trough as ecm. knife edge stuff for snowfall and i suspect local variations will be evident, especially where any altitude is involved. The further north , the more likely you are to hang on to wintryness throughout the next 10 days and perhaps beyond.

Yes, for Scotland the outlook is one which would qualify for a prolonged cold spell in the depths of winter, never mind mid-March:

Not a single run has uppers above 0C until the evening of the 20th of March some ten days away, with the mean held below -5C through to the 23rd:

[Snowman.]

Looking good if you want a reload!

[mushymanrob]

reload?we appear to be struggling to get much snow from-12 uppers, cant see -5delivering. its mid march, not mid winter, the outputs might look wintry but itll be hard to deliver now. but the outlook is cold, below average and unsettled.

of course i might wake up tomorrow and find a countrywide dumping!lol. c'est la vie.