18z model discussion - models pah, just use the 5 min radar!

[nick sussex]

Hi Yeti, I did suspect that the models would shift the front a little southwards, though in this set-up it wouldn't matter to much hopefully because it'll take several systems it appears to shift this cold air.

I myself coulsn't be more happy with todays runs as the shift southwards means I'm right where the heaviest snowfall would be possible and in the borderline of the mild air where the front should be the strongest, hopefully!

As for the GEM, its quite different from the other models but we shouldn't rule it out, esp given the 0z GFS isn't that far off what it actually suggests, just not as strong in terms of high pressure:

http://www.wetterzentrale.de/pics/Rtavn1201.png

GEM is stunning though, coldest month since 91 if that were to occur I dare say.

finally in the longer term be very careful, I think the models are over-doing that jet quite a bit by 240hrs and is going to be quite a lot more amplified then that...nearly every ensemble member has a decent HP to our east by 264hrs, while the 0z op doesn't at all so be careful wit hthe op runs, don't think they are picking out that high very well myself.

Unlike the ECM which appears to show it quite nicely. not only that but note that large LP complex is slowly decaying southwards and yes there is another deep depression in its wake but the movementr of LP's SE is a bvery good thing n the long term.

Morning KW well I agree with your thoughts regarding the progressive nature of some of the models, the key this morning is the ecm which sticks to its guns, as you said the gem is sensational but IMO a bit over the top. I wonder whether NOAA will be slating the operational runs of quite a few of the models today as they did yesterday. They expect the PV to remain over canada and the east pacific ridge to hold whilst transferring slightly further ne with energy going into the STJ, if we get pressure rises to the north and east then that would be a great outlook.

[Polar Continental]

Morning Folks- Back on UK Terra Firma!!!

regards

S

Hi Steve, hope you had a good time in Iceland, lets hope you’ve brought their weather with you lol, thanks for your excellent analysis of the models this morning, still very difficult to really know what will come out of this, but in a way I find this very complex situation more interesting, it adds the element of surprise, something not really experienced since the 70’s.

You never know, we could end up with a chart like this next week.

Paul

[The PIT]

Just looked at ECM which isn't a good run. So it's all up in the air.

[mushymanrob]

You never know, we could end up with a chart like this next week.

Paul

thats not a good chart, the air is scourced too far south so im not sure itll be that cold but even if it was it'd be dry.

interestingly, the more those lows sink into france the longer the cold spell will last which draws in the cold air longer on the easterly which should highten the eventual snow risk. surface temps of 3c or above just isnt good enough for settlement, ive seen snow melt on freezing ground so for a decent dumping id be looking at sub-zero temps for any snow to be of any use.

ps... louise leer just said 'we are confident of some disruptive snow on thursday for southern england'..... erm, that supports the models? (lol tenuous topic connection)

[kold weather]

Be careful mushy, note where that air is actually coming from in the first place and you'll see its sourced in the arctic as you can see on the 120hr chart before that:

http://85.214.49.20/wz/pics/Rgem1201.gif

http://85.214.49.20/wz/pics/Rgem1202.gif

the only thing that would limit that set-up is the cloud cover but it would probably turn out cold I suspect if that was right.

In terms of the snowfall on Thursday, every single model has a period of snow for nearly everybody Wed-Friday, even if it is just a breif snowfall before it turns to rain.

Edited February 6, 2007 by kold weather

[Nick F]

Potential for snow on Thurs seems to have shifted slightly further South on the 00z GFS output, so S'ern England at risk of some snow initially on Thursday morning, this transfering North to Midlands, E Anglia, Wales and perhaps N. England during morning, turning to rain perhaps South of M4 by late afternoon particularly South coast, but remaining as snow from the S Midlands/E anglia Northwards - where 10-15cm possible more over highground.

BBC forecasts this morning seem to think S'ern England is at greatest risk of snow with rain along South coast, not sure how far North yet, looking at faxes for Thursday suggests greatest ppn potential along S'ern England where occlusion(s) lie:

http://www.wetterzentrale.de/pics/brack1a.gif

[Frosty.]

Unlike the ECM which appears to show it quite nicely. not only that but note that large LP complex is slowly decaying southwards and yes there is another deep depression in its wake but the movementr of LP's SE is a bvery good thing n the long term.

Is this the same ECM that sucked on sunday into monday, suddenly it's the CHAMPION MODEL.. Hopefully the Scandi High will keep it cold up north for a good while.

[Troubleatmill]

thats not a good chart, the air is scourced too far south so im not sure itll be that cold but even if it was it'd be dry.

interestingly, the more those lows sink into france the longer the cold spell will last which draws in the cold air longer on the easterly which should highten the eventual snow risk. surface temps of 3c or above just isnt good enough for settlement, ive seen snow melt on freezing ground so for a decent dumping id be looking at sub-zero temps for any snow to be of any use.

ps... louise leer just said 'we are confident of some disruptive snow on thursday for southern england'..... erm, that supports the models? (lol tenuous topic connection)

Mushy ? Mushy ? , was that you mushy? saying its not a good chart because it would be mild & not cold enough ?

Edited February 6, 2007 by arron123

[yamkin]

Hi All

Not strictly on topic, but Everton Fox was, for the second day running, ramping a snow event for Thursday across Southern England, although today he dropped the 'even the London area' part of the ramp. I still think this is going to be marginal regarding snow in the south, having said that for the first time this winter driving from Southend to London the external temp gauge in the car finally registered a minus figure for about 8 miles before going positive again.

My guess, with my un-trained eye, from the current charts is sleety rain south of the Thames unless the colder air can push further south, still time for a few more changes though

Cheers all

FC

Models are gearing up for significant snowfall across many parts of the UK. Even the S/SE including London will get snow late Wednesday onwards.

[VillagePlank]

My t'pence worth . . .

It starts, for me, late Wednesday, early Friday. The first thing I looked at were the heights, below. As you can see on the 1000-500hPa chart the whole of the UK is behind the 528 dam line which, although not a great indicator, it's certainly cements the notion that snow might be able ot form and fall. It's not a great indicator because it describes 18,000ft of atmosphere, we can look at the 850hPa charts to find out what is going on much nearer the surface. Here I'd suggest that the 128 dam line is a reasonable indicator, and you can see that from (about) the Lakes down to London, and London to Cardiff and then follow the -5C isotherm gives a nice neat area of risk. Shame the far south coast, and the south-west appear to miss out here, though.

What about temps at the ground? A bit marginal perhaps. The chart I've posted is the Minimum C, the maximums are not sub-zero, unfortunately. However, the dew-points are. Things are boding well . . .

Now what we need to know is is it going to precipitate. Well the front certainly seems quite active from the 700hPa vertical velocity, and the precipitation charts, I think, might actually be OK (rather than the normal GFS overcook):

Some good chance of snow, I'd say just in time for Thursday mornings rush-hour around London. I wouldn't see GFS as the final solution, though, I would concur reasonable thoughts and map them onto the FAX output, as this seems the stable model at the moment.

I hope I haven't made a pigs-ear of this

[nick sussex]

Is this the same ECM that sucked on sunday into monday, suddenly it's the CHAMPION MODEL.. Hopefully the Scandi High will keep it cold up north for a good while.

No one said its the champion model! all models go through good and bad patches, the ecm is primarily used for medium term forecasting, for accuracy upto 72hrs the ukmo and its fax charts IMO are the best, the ukmo have never in all my years of model watching modified their data towards the ecm upto 72hrs and because of the human input garnered from years of experience the fax charts are head and shoulders above any model as they take into account alot more than just simply the output from the model.

The ecm has picked a trend post 144hrs and has stuck with it this morning with growing support albeit from a few of the cannon fodder models. The most slating over the last few days by NOAA has been reserved for one model and thats the gfs, however all the models have been too progressive and all have some criticisms aimed at them, they're not perfect thats why forecasters have to use their best judgement in seeing where they could be going wrong.

And anyway it looks like you'll be staying cold for the foreseeable future which hopefully will mean you're not too grumpy in here!

Edited February 6, 2007 by nick sussex

[BLOKEINSTOKE]

Snow falling in stoke this morning, nice covering on a thick frost, and good to see the models still trending in the right direction for later in the week

[Frosty.]

Models are gearing up for significant snowfall across many parts of the UK. Even the S/SE including London will get snow late Wednesday onwards.

And then the mild air pushes in melting it all.

[MisfitDog3]

"And then the mild air pushes in melting it all." Yes, but then it gets cold again. I see a serious risk of black ice developing across many areas at the end of this week. It's going to be very interesting.....

[johnholmes]

My t'pence worth . . .

It starts, for me, late Wednesday, early Friday. The first thing I looked at were the heights, below. As you can see on the 1000-500hPa chart the whole of the UK is behind the 528 dam line which, although not a great indicator, it's certainly cements the notion that snow might be able ot form and fall. It's not a great indicator because it describes 18,000ft of atmosphere, we can look at the 850hPa charts to find out what is going on much nearer the surface. Here I'd suggest that the 128 dam line is a reasonable indicator, and you can see that from (about) the Lakes down to London, and London to Cardiff and then follow the -5C isotherm gives a nice neat area of risk. Shame the far south coast, and the south-west appear to miss out here, though.

What about temps at the ground? A bit marginal perhaps. The chart I've posted is the Minimum C, the maximums are not sub-zero, unfortunately. However, the dew-points are. Things are boding well . . .

Now what we need to know is is it going to precipitate. Well the front certainly seems quite active from the 700hPa vertical velocity, and the precipitation charts, I think, might actually be OK (rather than the normal GFS overcook):

Some good chance of snow, I'd say just in time for Thursday mornings rush-hour around London. I wouldn't see GFS as the final solution, though, I would concur reasonable thoughts and map them onto the FAX output, as this seems the stable model at the moment.

I hope I haven't made a pigs-ear of this

not at all, a pretty good summation using a good mix of charts.

[Shunter]

http://ukie.accuweather.com/ukie/laminate floori-europe-blog.asp?

Not sure if this has already been posted but Joe B******* on Accuweather seems to think Northern Europe is in line for a cold late Winter / Early Spring with the demise of El Nino. This would seem to coincide with the METO late winter forecast.

Incidentally wasn't the METO seasonal update meant to be published testerday ??

[mushymanrob]

Be careful mushy, note where that air is actually coming from in the first place and you'll see its sourced in the arctic as you can see on the 120hr chart before that:

http://85.214.49.20/wz/pics/Rgem1201.gif

http://85.214.49.20/wz/pics/Rgem1202.gif

the only thing that would limit that set-up is the cloud cover but it would probably turn out cold I suspect if that was right.

In terms of the snowfall on Thursday, every single model has a period of snow for nearly everybody Wed-Friday, even if it is just a breif snowfall before it turns to rain.

morning kold..

yeah i might be wrong, but i think that air would have warmed up abit, cold-yes, but dry and that trough looks too shallow enough to produce much precipitation on its leading edge. but its all semantics. lets just see!

[loafer]

Always interesting to look at another model.

http://pages.unibas.ch/geo/mcr/3d/meteo/nmm22/PCP0360.PNG

Meteoblue shows Luton as the furthest south for snow.

Regards.

Loafer

[VillagePlank]

Always interesting to look at another model.

http://pages.unibas.ch/geo/mcr/3d/meteo/nmm22/PCP0360.PNG

Meteoblue shows Luton as the furthest south for snow.

Regards.

Loafer

Yes. I've just looked at the Fax output and I'd say that a line from N Wales to Southend is the bottom end line for snow from that chart. Perhaps somewhere betwixed and between, perhaps?

[edit] I'll rephrase: that line is the line of equiprobable distribution of snow and rain, so go further North if you want snow. [/edit]

I guess it's a waiting game to see which model wins for Thursday. GFS has the whole country (near-enough) under potential snowy conditions, and the MetO are only going for the Northern half.

Edited February 6, 2007 by VillagePlank

[James M]

Incidentally wasn't the METO seasonal update meant to be published testerday ??

No today, but I cant see any update yet.

[Polar Continental]

thats not a good chart, the air is scourced too far south so im not sure itll be that cold but even if it was it'd be dry.

interestingly, the more those lows sink into france the longer the cold spell will last which draws in the cold air longer on the easterly which should highten the eventual snow risk. surface temps of 3c or above just isnt good enough for settlement, ive seen snow melt on freezing ground so for a decent dumping id be looking at sub-zero temps for any snow to be of any use.

ps... louise leer just said 'we are confident of some disruptive snow on thursday for southern england'..... erm, that supports the models? (lol tenuous topic connection)

I tell you something if this chart came off, it would feel dam cold, those -10c 850's aren’t far away, and wouldn’t take to long to get here, look at those height rises beginning over Greenland, the air source would be of continental arctic origin, good enough for me at any rate.

Paul

[johnholmes]

No today, but I cant see any update yet.

usually done latish am

[Stuart]

it soon be time for the 6Z run

[carinthian]

I tell you something if this chart came off, it would feel dam cold, those -10c 850's aren’t far away, and wouldn’t take to long to get here, look at those height rises beginning over Greenland, the air source would be of continental arctic origin, good enough for me at any rate.

Paul

Hi Paul,

Well spotted. I think GP mentioned about to look to the NW for the block to strengthen. Thats even better for snow events. A feed of Ac is what is needed. By the way snow shower has deposited 2 cm here. Any in the Trent Vale ?

C

[Paul]

Locking this one down in 10-15 mins ready for the 06z.

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