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

[Robbie Garrett]

If only it went further South East, Undercut of the Millennium...

See the purple blob southwest of Greenland - that's the Canadian section of the polar Vortex!!!!

It's going south on holiday!

Otherwise a good undercutting trend compared to the previous run.

[fergieweather]

Only just catching up on all this discussion today, but can I strike major note of caution re any comment on UKMO-GM raw at T+120 etc.... this underwent major amendment at Exeter to reach better consensus with EC/GFS 12Z and for now the broad anticyclonic pattern remains favoured, i.e. mostly dry barring boundary layer developments onto E coasts. There was no support for GM solution and hence Exeter changes, as doubtless reflected in FAX charts (albeit I haven't yet checked) are as per modified model frames as example posted here.

Edited January 13, 2013 by fergieweather

[georgiedre]

Only just catching up on all this discussion today, but can I strike major note of caution re any comment on UKMO-GM raw at T+120 etc.... this underwent major amendment at Exeter to reach better consensus with EC/GFS 12Z and for now the broad anticyclonic pattern remains favoured, i.e. mostly dry barring boundary layer developments onto E coasts. There was no support for GM solution and hence Exeter changes, as doubtless reflected in FAX charts (albeit I haven't yet checked) are as per modified model frames as example posted here.

what do you think are the chances of slider happening at the end of the week like ukmo?? or is this the big question that the mo cant decide?

[karlos1983]

Country Wide Snow at +288 ......from a westerly

[If Wishes made Weather]

Updated UKMO FAX for 120, while nothing like as extreme as the raw computer output is of interest though as it seem to poise a low pressure system for a possible undercut - but it looks like it may go too far south more towards Biscay.

[on the coast]

Thought the Ukmo was on one. Looked great though.

[Froze were the Days]

and at 204z PV sets up shop in it's usual place and a westerly jet ensues. GFS not throwing us a bone at all, even the easterly looks like a maximum of a 1 day event.

[Cloud 10]

Only just catching up on all this discussion today, but can I strike major note of caution re any comment on UKMO-GM raw at T+120 etc.... this underwent major amendment at Exeter to reach better consensus with EC/GFS 12Z and for now the broad anticyclonic pattern remains favoured, i.e. mostly dry barring boundary layer developments onto E coasts. There was no support for GM solution and hence Exeter changes, as doubtless reflected in FAX charts (albeit I haven't yet checked) are as per modified model frames as example posted here.

Thanks for that,shame about those "modifications" though!

120 fax.. ukmo 120..

[johnholmes]

Just another question. Why is it called a Fax chart ? Does FAX stand for something ?

Is this a this weeks fax chart = Seems like there is a high pressure moving towards us on Thursday.

http://www.metoffice...oductId/4419010

facsimile-goes back to the days when weather charts were mostly transmitted that way

[J10]

Its very unlikely , any westerly flow has so much modification that its exceptionally rare to see decent snow and cold off that type of set up.

You'll never get ice days or decent lying snow on low ground unless its from the north round to the east.

Actually NNW surface flow tends to be very good, especially if the source of the air, is northerly.

[Col Berkshire]

Only just catching up on all this discussion today, but can I strike major note of caution re any comment on UKMO-GM raw at T+120 etc.... this underwent major amendment at Exeter to reach better consensus with EC/GFS 12Z and for now the broad anticyclonic pattern remains favoured, i.e. mostly dry barring boundary layer developments onto E coasts. There was no support for GM solution and hence Exeter changes, as doubtless reflected in FAX charts (albeit I haven't yet checked) are as per modified model frames as example posted here.

Does this mean the snow showers feeding in from the North Sea across most of the south is now unlikely? I'm referring to Wednesday.

[Matty M]

Only just catching up on all this discussion today, but can I strike major note of caution re any comment on UKMO-GM raw at T+120 etc.... this underwent major amendment at Exeter to reach better consensus with EC/GFS 12Z and for now the broad anticyclonic pattern remains favoured, i.e. mostly dry barring boundary layer developments onto E coasts. There was no support for GM solution and hence Exeter changes, as doubtless reflected in FAX charts (albeit I haven't yet checked) are as per modified model frames as example posted here.

As expected, too good to be true. Cheers for the update and hopefully it will be found to be a trend setter for the 0z

[fergieweather]

Thanks for that,shame about those "modifications" though!

120 fax.. ukmo 120..

Yup: as expected, and obviously logical (!!), follows modified GM with the FAX. Am about to digest long analysis from Exeter on all the rationale.

[Davey80]

So its confirmed from the Met that Friday's UKMO chart won't happen then!

[Froze were the Days]

Country Wide Snow at +288 ......from a westerly

Can't see that happening at all, maybe towards the north but the uppers will be too high. Just by looking at the synoptic of that it's simply not cold enough.

[nick sussex]

Thanks for that,shame about those "modifications" though!

120 fax.. ukmo 120..

Well take something positive from the modification, its still a good looking chart with enough energy going se to suggest that the cold could hang on for a while longer.

Theres still a chance for some fronts to skirt with the west/sw to produce some frontal snow, theres so much uncertainty so best to really view any post 96hrs output with alot of caution.

[georgiedre]

Did you not read his post? He practically answered that question..

yeah i understand that but there could still be a chance of the low sliding even if its really a remote chance and that why i was asking?

[cyclonic happiness]

Actually NNW surface flow tends to be very good, especially if the source of the air, is northerly.

Didn't we get snow from a westerly a few years ago? It wasn't in that October snow was it?

[karlos1983]

Can't see that happening at all, maybe towards the north but the uppers will be too high. Just by looking at the synoptic of that it's simply not cold enough.

Yeah I know, but couldn't help but post it, crazy charts, there are a few of them actually, I think there was a 945MB low at one point in the Atlantic.

[fergieweather]

As expected, too good to be true. Cheers for the update and hopefully it will be found to be a trend setter for the 0z

I think it's vital to appreciate Exeter can only be pragmatic and at this range, given model uncertainty, only run with what seems largely consensual as outcome. Anyway: it's far off in yonder given present climate of model nuance issues. We shall see.

[ocean]

So much uncertainty from all the models. Is there a certain crunch point within the charts where the models will get a grip and have a good handle on the approximate patern or is it always the same with cold synoptics with wild swings fro run to run ????

[Continental Climate]

I dont fancy our feeble block's chances against that huge 945mb piece of vortex in the atlantic http://www.wetterzentrale.de/pics/Rtavn1681.png!!

[nick sussex]

Actually NNW surface flow tends to be very good, especially if the source of the air, is northerly.

Lol! really you know I've only been on here 8 years, fancy that a nnw sourced in the north being cold!

[Mucka]

No worries, the mighty NOGAPS is showing the way forward

[Stoxs]

well i think

The GFS,ECM,UKMO, T120 PV GH SW going SSW with LP on the JS around the NA sliding round the UK into biscay at T144,

this also

lets the HP over Sc head NNW and the SW head SE into EA.

while the SSW ?

Finally FI is F1 at T 12

P.S the PPn lght at T24 due to snow one having a clue

Edited January 13, 2013 by Stoxs