Model Output Discussion:

[cooling climate]

How realistic this is is impossible to judge just from the GFS/Extra output. You have to read CAREFULLY the 3-5 day and 6-15 day outlook from UK Met. NAE obviously is not out far enough yet to make a direct comparison. Perhaps we may get an insight into their thinking if Ian F posts in sometime this afternoon or evening.

From what I have seen this winter you will learn nothing from the met or anywhere else that you

can not see for yourself at a three to seven day range.

There ideas change with the models. Forcasts out to two days or so thats different that is where

there expertise lies.

[kpm62]

Up to about Tuesday/Wednesday the model are fairly consistent with each other,and its pretty much a cert that the UK is in for a cold blast that could turn out to be a prolonged cold spell with much snow.Seems the SE is going to cop it most,what do you think?

[kold weather]

Looking through the ensembles most have a good 24-48hrs period where we have easterly winds and possible disturbances coming through, depending on the strength of any wave/low that forms within the cold pool. After that there is decent variation though quite a few of the runs I've seen thus far actually hold onto a weak easterly flow much like the 12z run.

Keep an eye on any possible disturbances developing around 120hrs, the 12z GFS does show something and that may well pop up from time to time in the models in general as well I suspect as its what introduces the second phase of colder air.

[TEITS]

Up to about Tuesday/Wednesday the model are fairly consistent with each other,and its pretty much a cert that the UK is in for a cold blast that could turn out to be a prolonged cold spell with much snow.Seems the SE is going to cop it most,what do you think?

I would love to give you an answer but unfortunately Mon, Tues, Wed are currently +72,96,120. We shall have to wait until Sunday when this comes into range of the NAE model.

The problem with pinning detail at this stage is a slight shift in the pattern can be the difference between a NNE/ENE,ly and this changes the distribution of showers. Also any disturbances within the flow might not yet be picked up.

Based on the 12Zs then I would agree the SE is most favoured for the simple reason of being further away from the HP. However at this stage much can change and most probably will wrt detail.

Sunday is looking particularly chilly with max temps only around 3-4C.

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

This will feel rather raw in E areas with cloudy skies and light drizzle.

[Ian Fergusson]

How realistic this is is impossible to judge just from the GFS/Extra output. You have to read CAREFULLY the 3-5 day and 6-15 day outlook from UK Met. NAE obviously is not out far enough yet to make a direct comparison. Perhaps we may get an insight into their thinking if Ian F posts in sometime this afternoon or evening.

Hi John

My blog entry updated early today reflected very closely the latest thoughts from the UKMO's medium range guys at Ops Centre at 12z - in summarised fashion. See http://bbc.co.uk/ianfergusson

Their continuing rather muted 'concerns' regarding anythingly significantly snow-laden remains one of the most consistent aspects (e.g., note the low % PROB they've offered for risk of snow on the anticipated frontal incursion around 14/15th).

But it should be self-evident to anyone on this forum how all this remains subject to considerable change and no intepretation of PPN detail at a regional (let alone sub-regional) level is frankly worth the effort for now, save from the safer bet of some accumulations in the east (indeed, latest UKMO GM keen to paint snow feeding into eastern England / East Anglia Tues/Wed, for example, but with somewhat limited amounts presently expected).

Cold and mostly dry remains the overwhelming thrust of things from UKMO for most western / southern-central districts into the 6-15 day outlook.

Best

Ian

[Geordiesnow]

Nice few upgrades in the models but once again, unless the ECM backs away from its own output regarding a quick showery airflow followed by high pressure being pretty much near us then we can't take anything for granted unfortunately, especially when you see both the GFS and UKMO backed away from there stunning cold charts yesterday.

I think some may be surprised by Monday as i think there could be more PPN than the charts suggest. I also like to think there be more sunshine by Monday and looking at Monday's charts, it would suggest more sunshine and showers than cloudy with snow flurries/drizzle which is what we are likely to have on Sunday.

Interesting output and one that can easily upgrade into something more interesting whilst it can easily downgrade aswell.

[Thundery wintry showers]

I think the only way precipitation will end up as sleet or rain for most from Tuesday onwards will be if the setup downgrades significantly. However before the easterly is progged to come in it does look marginal for anything significant lying on the ground. Sunday & Monday look like a wintry mix though.

ECM will be important but I don't think this morning's ECM was as "dry" a run for eastern England as some are implying.

[johnholmes]

Hi John

My blog entry updated early today reflected very closely the latest thoughts from the UKMO's medium range guys at Ops Centre at 12z - in summarised fashion. See http://bbc.co.uk/ianfergusson

Their continuing rather muted 'concerns' regarding anythingly significantly snow-laden remains one of the most consistent aspects (e.g., note the low % PROB they've offered for risk of snow on the anticipated frontal incursion around 14/15th).

But it should be self-evident to anyone on this forum how all this remains subject to considerable change and no intepretation of PPN detail at a regional (let alone sub-regional) level is frankly worth the effort for now, save from the safer bet of some accumulations in the east (indeed, latest UKMO GM keen to paint snow feeding into eastern England / East Anglia Tues/Wed, for example, but with somewhat limited amounts presently expected).

Cold and mostly dry remains the overwhelming thrust of things from UKMO for most western / southern-central districts into the 6-15 day outlook.

Best

Ian

thanks for that Ian-trying to forecast precip more than 24 hours ahead is almost always fraught-when its a possible turn to wintry type then its even more so. Their suggestion of snow for eastern then some central and SE'ern areas is what posters on here must accept as the realistic view at the moment.

[Ben_Cambs]

GEM 12z quite similar to UKMO at T+144 this evening: http://www.meteociel...&carte=0&mode=0

ECM will be key tonight IMO. Also the GEFS ensembles were also very good tonight too A cold outlook

Edited February 5, 2010 by Snowman0697

[Cheshire Freeze]

I remember just before the cold spell in January that some posters were worrying there would be no precipitation......look at the reality and how quickly features popped up then

[kold weather]

The flow being shown is fairly weak and with a lack of deep cold at HPA plus a warm North Sea we shouldn't assume that PPN anywhere will be of snow at this range.

Not convinced by the way the GFS meanders the HP around.

Take a look at the SST's anomalies Ian and you'll find the North Sea and the Balatic are pretty cold for the time of year and in any decent easterly will only get colder still!

I think the models have real shades of Feb 86 at the moment however I'd be something of a fool to suggest it'd go either that cold or as sustained!

Ian F, very good post, the fact you mention Tues/Wed doesn't surprise me though looking at the models its something I've mentioned on this thread. All I'll say is more often then not those sorts opf situations get upgraded as the models latch onto different aspects...I've seen it in fact countless times this winter already.

[TEITS]

The flow being shown is fairly weak and with a lack of deep cold at HPA plus a warm North Sea we shouldn't assume that PPN anywhere will be of snow at this range.

Not convinced by the way the GFS meanders the HP around.

Upper temps currently suggested are around -8/9C for Mon/Tues dropping to around -11C for Thurs. Now upper temps during our previous cold spells in Dec/Jan were similiar around -11/-12C although these values were shortlived.

The N Sea certainly isn't as warm as it was in Dec. I wouldn't fancy dipping my toes in Hunstanton.

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

So the combination of both means I strongly disagree.

[Nick F]

The flow being shown is fairly weak and with a lack of deep cold at HPA plus a warm North Sea we shouldn't assume that PPN anywhere will be of snow at this range.

Not convinced by the way the GFS meanders the HP around.

I echo what other have said, the uppers do become sufficiently cold and thicknesses sufficiently low on GFS progs for snow next week, perhaps even light snow flurries as early as late Sunday/early Monday - though dew points do look marginal along east coast until Tuesday ... the threat of heavy snow showers more likely to come mid-week onwards as the upper and surface flow becomes more cyclonic and the uppers grow colder.

[LomondSnowstorm]

http://www.meteociel...CM1-72.GIF?05-0

ECM coming out now.

Decent agreement with the UKMO http://www.meteociel...72-21.GIF?05-18

LS

edit: http://www.meteociel.fr/modeles/ecmwf/run/ECM1-96.GIF?05-0

At +96 the high is too close to northern Scotland.

Edited February 5, 2010 by LomondSnowstorm

[kold weather]

ECM now coming out by the way guys, out to 72hrs with a weak easterly airflow c oming in.

Ensembles for the GFS are very good on the whole, pretty much all of them are cold/very cold at least out to 192hrs, some keep the cold going at the surface right through to the very end of the runs, with quite a few sinking the upper high but propping it by an undercutting jet close to the UK.

[Ian Fergusson]

Ian F, very good post, the fact you mention Tues/Wed doesn't surprise me though looking at the models its something I've mentioned on this thread. All I'll say is more often then not those sorts opf situations get upgraded as the models latch onto different aspects...I've seen it in fact countless times this winter already.

Oh absolutely - it's one of those periods where we'll see innumerable tweaks of emphasis on an almost daily basis and especially with the PPN signal remaining so effectively ambivalent. Obviously from a UKMO perspective given their PWS responsibilities, they're (understandably) honing their medium range briefings based around potential for disruptive snowfall, versus the mere 'interest value' prospects of snow per se. As someone else commented on here a little while ago, I'm also inclined to await the NAE's grasp on developments from around Sunday's runs onwards because the PPN details currently expressed at longer range by GFS, UKMO-GM or whatever are so open to very elastic interpretation!!

Incidentally, worth adding that ARPEGE has tended to tally quite closely with UKMO on recent evolution and it will make for important comparison into next week.

Edited February 5, 2010 by Ian Fergusson

[snowray]

T72 ECM, could this be a Thames Streamer I wonder, wheres SM?

Great start, and nothing like the GEM, or the GFS Control Parallel run that seems to be very similar to GEM's 12z.

Edited February 5, 2010 by snowray

[Polar Continental]

Evening everyone,

Well another cold to very cold run from the 12z GFS and UKMO. It is notable how far south the jet stream goes on some charts again, dipping well south of the Azores on quite a few. This has been a repeated pattern through out this winter. December 2009

After the early runs suggesting the high would sit very close to the UK, there are some indications now that the high will sit a little further north west, so a better chance of the very cold uppers being advected in to the country from the north east. At this stage Wednesday in to Thursday looks to be the time when –10c hpa gets pushed westward from off the continent.

Lets see what the ECM says.

[Tomomcd]

Well the pattern seems to be remaining good on the 12z ECM, High is probably slightly better positioned than the 00z run

[Bobby]

ECM is very different to UKMO and GFS already. Not in a good way if you like snow.

[MisfitDog3]

which model has broken ranks on the ensemble out of interest?! The thin red line indeed!

[loopydreamer]

Well the pattern seems to be remaining good on the 12z ECM, High is probably slightly better positioned than the 00z run

yep! this is looking much better for us! its taken a while to learn how to read these models but im finally understanding it more now, i think

[kold weather]

Mainly a more SE event from the ECM in keeping with its last few runs, still very cold for all pretty much though it seems.

Ian, will be interesting to see what the 144hrs chart shows, I think the upper high will probably build further north given the med low is deepening and the upper low further west is becoming much better alinged but who knows of course, its all just guess work!

Any developing upper high may well break off the easterly though, remians to be seen!

Edited February 5, 2010 by kold weather

[MisfitDog3]

maybe but the ECM would give some pretty low night temps elsewhere! Record breakers?

[SnowBallz]

+144...

Hmmm, pretty potent