General Model Output Discussion

[tinybill]

i know the country file was giving heavy snow for friday this for saterday

Edited January 3, 2010 by tinybill

[cooling climate]

can anyone answer the above question, BFTP , KOLD, JH, STEVE ?

Or is there nothing in the charts to explain this?

Its really foxed me!

It looks to me that while the dew point and 850 temperatures are within the parameters your surface temperature

is a little on the high side mid morning through to mid afternoon on Tuesday although dropping away sharply

during afternoon and evening.

The 0c isotherm is at about 600metres + during this time period.

Scrap that for some reason I thought you were down in Cornwall but I see you are from Cardiff, my bad.

John or Steve may be able to help as the answer is not obvious, to me anyway.

Edited January 3, 2010 by cooling climate

[Neilsouth]

http://www2.wetter3.de/Animation_12_UTC_05Grad/180_24.gif

29cm+ , almost a new ice age

[kold weather]

I think that's because the op is at a higher resolution and can pick up the precipitation better than the other members.

Yep thats the case for at least the first spike though the set-up progged by the 12z GFS for 144hrs maybe something of a synoptic outlier, but saying all that its an evolution I've seen before from an easterly where the upper low is strong enough in Europe to help spawn a secondary depression.

Regardless there is enough in the chart for even central and western parts to keep a very close eye out.

[SMU]

http://www2.wetter3.de/Animation_12_UTC_05Grad/180_24.gif

29cm+ , almost a new ice age

Sorry to say Neil-- Ive enlarged that image & the 29cm pixel is up towards Gravesend-- I noted tyler hill on the map & you have between 1-3cms...

S

[TEITS]

He is referring to the track of the Low over Spain & how far North & West it gets-

The track has been modified a little south & East since yesterday- hence the WHOLE of the UK not being enveloped by the Easterlies-

In terms of ENGLAND as a whole not to much as changed- the longivity of snowfall under the easterly regime has probably shortened from 4/5 days to 3/4 days-

Again further correction south east cant be ruled out- each time that happens it will shorten the available time of snow threat, & receed the effected areas further South & east along with it-

Deepest darkest Kent looks a sure fire bet, London looks very very probable-- midlands 50/50-

S

Im not entirely sure I agree with your comments about 3/4 days or the 50/50 across the Midlands.

The risk of snowfall actually begins on Tues especially for locations away from the SE (see link below).

http://www.wetterzentrale.de/pics/Rtavn664.png

Looking at the charts for +144 and the risk of snow for many continues especially in the E/SE. So that potentially makes the risk of snowfall at least 5 days and possibly 6 assuming some snowfall is still possible at +168.

At the moment I would say many locations are at risk from snow but of course E/SE is favoured. However the risk starts on Tues whereas the SE have to wait until probably Wed. This is nicely reflected on the Met O warnings.

Just re-read the Met O warning for Tues with 15cm being predicted for Peterborough, Norfolk, Cambs.

Edited January 3, 2010 by THE EYE IN THE SKY

[snowking]

New FAX charts now coming out

Gets rid of the warm sector from mainland britain....just southern ireland now in it

http://www.meteociel.fr/ukmo/fax/fax36s.gif

http://www.meteociel.fr/ukmo/fax/fax48s.gif

SK

[SMU]

Im not entirely sure I agree with your comments about 3/4 days or the 50/50 across the Midlands.

The risk of snowfall actually begins on Tues especially for locations away from the SE (see link below).

http://www.wetterzentrale.de/pics/Rtavn664.png

Looking at the charts for +144 and the risk of snow for many continues especially in the E/SE. So that potentially makes the risk of snowfall at least 5 days and possibly 6 assuming some snowfall is still possible at +168.

At the moment I would say many locations are at risk from snow but of course E/SE is favoured. However the risk starts on Tues whereas the SE have to wait until probably Wed. This is nicely reflected on the Met O warnings.

Just re-read the Met O warning for Tues with 15cm being predicted for Peterborough, Norfolk, Cambs.

Hi TEITS- Sorry I meant 3/4 days of the frontal snowfall from the SE- its still as you say from t72 onwards --- which yes could be 5-6 days-

SO in summary-- light snow from the north moving to heavier snow from the NE, to very heavy snow from the ESE back to snow snow showers from the NE-

not bad-

S

[phil nw.]

Continuing cold output for this week from all the models to date.

Fax out for T48hrs.

Showing the arctic air coming south behind the cold front.

Snow fairly widespread according to NAE Pctn. chart.

Just a guide from this range it must be said but shows that starting Tuesday snow fall will become more likely for places that have seen little or none.

[pyrotech]

It looks to me that while the dew point and 850 temperatures are within the parameters your surface temperature

is a little on the high side mid morning through to mid afternoon on Tuesday although dropping away sharply

during afternoon and evening.

The 0c isotherm is at about 600metres + during this time period.

Scrap that for some reason I thought you were down in Cornwall but I see you are from Cardiff, my bad.

John or Steve may be able to help as the answer is not obvious, to me anyway.

Yes like you said can understand cornwall but not my location. I can see no reason and unless someone else can will have to asume its something we do not have access too that they have to predict this.

[TEITS]

Hi TEITS- Sorry I meant 3/4 days of the frontal snowfall from the SE- its still as you say from t72 onwards --- which yes could be 5-6 days-

SO in summary-- light snow from the north moving to heavier snow from the NE, to very heavy snow from the ESE back to snow snow showers from the NE-

not bad-

S

I see what you mean.

Summary sounds spot on. I will take that.

[Duane S.]

We are on the brink of what could go down in history as one of the greatest cold/snowy spells in the past 50 years.

You shouldn't wish days away I know, but it is going to be fairly agonising over the coming couple of days for sure as we scrutinize each run, looking for spoilers and downgrades (and they will be there). For once there is a little bit of leeway (in terms of the eventual placement/track of the low pressure system etc) for me to profit from this. Obviously the SE and E stand to do the best but I really think there is a fair chance of receiving quite a dumping over the next 7 days from this. ('Quite a dumping' in my neck of the woods=5cm BTW )

I was heartened by that incredible BBC forecast earlier and tonight's charts have done nothing but improve our chances of something special. The METO looks excellent once more and again the GFS seems keen to develop a little system just off Normandy (albeit a bit later on than the 06z progged it). As I said earlier, I still think that even if it doesn't develop a closed circulation, the air will be plenty disturbed enough to set of numerous heavy snow showers around Wednesday into Thursday that will affect the far South as well as the usual suspects. Gotta have hope anyway!

Edited January 3, 2010 by s4lancia

[john w]

SK you beat moi to it.

Was awaiting those faxes on weatheronline. your sources obviously had them quicker.

Pushing the warm sector to the west certainly now making the snow risk rather less marginal the further east you are. Wonder if Meto will update to reflect this.

Also...and belated...thats to JH and Ian Ferguson for answering my questions earlier. we are gifted with a number of model outputs at work and we also receive a number of models extra outputs that do seem to be available online. It strikes me how open the internet is for these forecasts which is good IMO.

I do have to say the potential for the south has massively improved in the past 36 hours of outputs with now snowy and cold the more likely as opposed to dry and cold. I expect to see a meto change to reflect this come their next update.

[Nick F]

New FAX charts now coming out

Gets rid of the warm sector from mainland britain....just southern ireland now in it

http://www.meteociel.fr/ukmo/fax/fax36s.gif

http://www.meteociel.fr/ukmo/fax/fax48s.gif

SK

The period from 12z tomorrow until 00z Wednesday could see snow for many as that cold front moves south from Scotland. Then behind the front, the unstable northerly veering northeasterly in the east will bring further snow showers across the north and east and down the Irish Sea, and the snow showers not really stopping in the east for the rest of the week and into next weekend. Could be the most interesting wintry 7 days or so for years for some. The Countryfile forecast for this week could be a forecast for the week ahead back in the wintry spells of mid-80s.

[Michael Fishermans Friend]

JMA and GME 12zs get there in the end with quite a strong NE/ENE wind but the GEM still reluctent.

[kold weather]

Very good fax charts, the thing to notice is the low pressure system is moving SSE which means the front isn't going to be moving too fast, therefore a few hours of moderate snowfall seems quite probable, esp further north where the system looks a little stronger...though the time of day may make things a little more marginal for the Midlands...

[J10]

can anyone answer the above question, BFTP , KOLD, JH, STEVE ?

Or is there nothing in the charts to explain this?

Its really foxed me!

I'm have already sort of answered this in the Wales thread. But latest (BBC) forecast go for snow. The latest Fax chart has removed the warm sector, and with the embedded cold, and the time of night, the front is set effect, I would expect snow apart from maybe on the far western coasts. This is far less marginal than the event before Christmas for a number of reason/.

Slight problem we see on the NAE Snow/Rain limit on Weatheronline is the lack of detail shown.

[snowking]

Very good fax charts, the thing to notice is the low pressure system is moving SSE which means the front isn't going to be moving too fast, therefore a few hours of moderate snowfall seems quite probable, esp further north where the system looks a little stronger...though the time of day may make things a little more marginal for the Midlands...

Yep, the 12z GFS certainly certainly keen on the idea of a very slow moving front.....infact as it heads south of the midlands it has it almost slowing completely with a fair bit of vortical lift associated with it by the time it reaches just north of the M4

It wouldnt suprise me to see one or two areas around the M4 corridor seeing some snowfall through much of the afternoon and evening on tuesday

SK

[Michael Fishermans Friend]

NOGAPS (For what its worth) partially there with the easterly but HP only just to the north, be interesting to see if ECM is still similar to GEM.

[johnholmes]

can anyone answer the above question, BFTP , KOLD, JH, STEVE ?

Or is there nothing in the charts to explain this?

Its really foxed me!

not seen the NAE charts so best you post a link or show a couple, with the usual thank you, and I'll take a look.

On the other evidence it does seem a bit unlikely but I need to see what you are talking about first-thanks?

[TEITS]

+60 dax chart shows a trough from Lincs to Mid wales.

So in summary for Tues a cold front moves S bringing possibly some snow. We then see snow showers becoming heavier and more frequent during Tues night into Wed morning.

http://www.meteociel.fr/ukmo/fax/fax60s.gif

Also highly recommend you read the forecast on BBC teletext pg 403 for Wed!

[Ian Fergusson]

Yep, the 12z GFS certainly certainly keen on the idea of a very slow moving front.....infact as it heads south of the midlands it has it almost slowing completely with a fair bit of vortical lift associated with it by the time it reaches just north of the M4

It wouldnt suprise me to see one or two areas around the M4 corridor seeing some snowfall through much of the afternoon and evening on tuesday

SK

Hi SK,

Interesting analysis - thanks - and supported by the last set of UKMO NAE modified fields (attached as showing rain/wintry PPN discrimination albeit with a somewhat earlier timeline focus for M4 corridor than GFS), so it will be interesting to see how the next run handles this in consort (or not!) with the 12Z GFS prog.

Cheers

Ian

Edited January 3, 2010 by Ian Fergusson

[yamkin]

ECM 12Z is rolling out and so far is showing good agreement with GFS 12Z. It's game on

[Neilsouth]

ECM 12Z is rolling out and so far is showing good agreement with GFS 12Z. It's game on

Lets just hope it agrees with friday - saturday , so far looking good... noticing some good kinks in the flow and a little convective low across the south east

[johnholmes]

Hi SK,

Interesting analysis - thanks - and supported by the last set of UKMO NAE modified fields (attached as showing rain/wintry PPN discrimination albeit with a somewhat earlier timeline focus for M4 corridor than GFS), so it will be interesting to see how the next run handles this in consort (or not!) with the 12Z GFS prog.

Cheers

Ian

thanks Ian

that does explain what Pyro was asking about.

Sea temps in the far SW seem as being suggested to be high enough to give a wintry mix for the SW other than on the Moors. A similar thing being shown on the last chart for adjacent to the east coast.