Model Output Discussion - Sunday 20:35--->

[Cal]

http://91.121.94.83/modeles/gfs/run/gfsnh-0-360.png?12 Synoptic heaven? .

[Iceberg]

Looks like the alternative GFS concurs at the crucial 120-144 time range.

[mountain shadow]

Widespread white Christmas guaranteed if this chart verified (which it won't)

http://209.197.11.115/c9s4a5k3/cds/gfsimages/gfs.20091207/12/372/airpressure.png?dopvhost=charts.netweather.tv&doppl=841a626ccf0753e0cf5753b01e9258fbcf575354&dopsig=320b4e4a800582f0fe80a346348cb634

[Cal]

Probably the finest run i've seen in F.I. truly remarkable those synoptics.

http://91.121.94.83/modeles/gfs/run/gfsnh-0-384.png?12 The finale'

[Thundery wintry showers]

I think from the T+144 GFS, irrespective of shortaves, there's only one way that evolution is really going to go, with the warm air advection up western Greenland, the Atlantic systems way out west and the high to the north sinking southwards.

The "crunch period", for me, lies between T+72 and T+144. If we can get that large high extending right up to the north, without interference from the Atlantic, we should get some kind of cold easterly, though the T+168-T+192 stages of the 12Z hint that a brief 36-hour easterly with a wintry mix of showers is a possibility particularly the further north you go. But if we get shortwaves repeatedly running through the block, as per the ECMWF 00Z today, then the high over the Arctic will be prevented from slipping south and the "window of opportunity" will be lost.

I agree that FI on the 12Z does look like a snowfest for most as the easterly flow gets going across the whole country again (lol at the northerly at T+384 as well!)

[snowmadchrisuk]

It does turn into an absolute snow fest for the south 19/20th of December. Far to far away for anything but dreams though.

However since we have LP's tracker through southern Europe the chances of one of them come up further north and hitting the colder air must be quite high.

It actually shows at least for Eastern Uk Snow from +156 , What I can see from the charts is the initial Cold is getting closer to time , what happens on the 18th/19th is to far , I'm concentrating on the 13th-15th as it is likely that once we get into that flow Showers would form and spread inland at least to the midlands and they would be of snow at least by the 14th.

Edited December 7, 2009 by snowmadchrisuk

[mountain shadow]

Probably the finest run i've seen in F.I. truly remarkable those synoptics.

http://91.121.94.83/modeles/gfs/run/gfsnh-0-384.png?12 The finale'

That will be the Met Office "Brisk Northerly".

[NorthantsSnow]

I can't believe this run is actually being criticised for not being cold & snowy enough. Goodness, if this one doesn't cut the mustard what will? By far the best run I have seen recently for long lasting cold and snow prospects and would set us up nicely for a white Christmas in some areas, if not from already accumulated snow then fresh snowfall!

Good to see some of these mouth watering charts entering the high-res part of the run as well. Overall, simply delighted with tonight's GFS.

[phil nw.]

That was an amazing run for prolonged cold.I would bank it if i could.An easterly followed by a northerly ala 1960`s style.

Nice to look at and dream.

Still back to reality let`s get to the weekend with this High and see if things change.

[Thundery wintry showers]

Again, some caution. The period we really need to be focusing on is 10-12 December. If the omega block looks set to form (and it does look remarkably similar to the one at the beginning of January 1985), then we can start thinking of pinning down the details on some kind of showery E'ly or NE'ly. But the GFS and UKMO could be failing to pick up shortwaves running to the north of the UK as per the 00Z ECM. If said shortwaves scupper the omega block then we might just end up cold and dry with high pressure.

My pessimism early in the run was based on the fallacious assumption that the "toppling" high at T+168-T+192 might topple south across the whole country, rather than sticking around to the N and NW.

Edited December 7, 2009 by Thundery wintry showers

[TEITS]

Another astonishing run.

I know im referring to F.I but the 12Z is a perfect illustration of how this pattern can become locked in with alternating E/NE/N,lys like it did in the famous winters of 47, 63.

Lets hope this huge brick wall around Greenland actually becomes reality.

[Snowly does it]

Taken as a whole, about the best possible outcome for extended cold as a run - the only missing ingredient for the 'ultimate' is -15 850s hitting a bullseye but regardless shows a 10 day cold spell with repeated snow chances and a lovely retrogression. Would anticipate this (were it to occur on reality) extending into a 3 week cold spell that would rival anything since certainly 95/96 - a synoptic set up such as shown which allowed some of the -15s in before the coldest air is cut off would be 1987 redux, or an extended 1991.

Better than the post Christmas near miss of last year, but a nervous 48 hours ahead.

Enjoy the anticipation.

[Harsh Climate]

The entire evolution upto 180h is good, so we are another small step in the right direction. Really no need to worry about the second page (192h+), because that is just one possibility out of dozens of what might actually happen. If I was to nit pick though, I dont like how the artic high has started to dissapear on the last couple of runs.. The artic high was the catalyst to the spectacular chart we got the other night, without its influence I feel that the shortwaves are more of a threat to ruining everything...

[D KARLSON]

A check through the models shows that GFS T+144 today is almost identical to UKMO T+144 yesterday. Those who said the UKMO at T+144 had considerable potential were right and I think if we get to the GFS T+144 then some kind of cold easterly or north-easterly is very likely.

But the ECMWF shows how this setup could be scuppered. If the shortwaves don't "behave themselves" then they could keep on coming through resulting in our high staying south instead of merging with the developing Arctic/Siberian/Scandinavian high and retrogressing towards Greenland as per the GFS runs and yesterday's ECM/UKMO.

Personally I am backing the ECM as I've seen this kind of thing happen all too often- February 2005, January 2006 for instance. A cold easterly or north-easterly is IMHO about 30% likely.

As thet say the truth hurts and the very cold scenario has always been the outsider thats not to say it wont happpen ,but if your looking for this ,we need the output verified within the reliable timeframe.

just an update on things and the meto outlook was this morning forecasting easterlies followed by a possible breakdown from the south west ,this has been altered to north easterlies with showers turning increasingly wintery in the north and east and this pattern continuing for the forseeable furture.

As the above reads thats a classic example of how quickly they change there tune thats not to say it wont change yet again tomorrow,but what can be read from this is the percentage chance of this very cold scenario materialising ,so now for the great Steve Murr and his 30% we could now perhaps increase this chance to 40% and that would be realistic and continue to increase this possibility if the models continue to verify the

SAUSAGE CASSEROLE SCENARIO !!!!!!!

[Iceberg]

The alternative brings the snowfest for the south forward a couple of days to the 17/18th of December.

Maybe not quite as good a run, but the LP's pushing up from the south and hitting the colder air, seems to be a reoccuring theme.

[Cheese Rice]

A bit off topic but when was the Feb easterly forecasted by the models (as in how long before, e.g. a week before), it justs seems a bit odd that members are talking about charts in FI when usually we are advised to take this far out with a pinch of salt.

Edited December 7, 2009 by 10123

[snowmadchrisuk]

The Parallel has gone exactly the same way , and even colder 850's even earlier . The Op and the Parallel seem to be following each other lately .

[Frosty.]

http://91.121.94.83/modeles/gfs/run/gfsnh-0-360.png?12

A very wintry scene

Still over a week away until the real cold is progged to arrive so a lot can and probably will go wrong, this being the uk..everything has to be perfect. One step at a time though, lets get the high here from thursday onwards and see if we end up with an easerly or northerly or both, being greedy it would be nice to have both and the meto mention a Northerly with increasingly wintry showers and frosts which is quite an upgrade from them.

Edited December 7, 2009 by Frosty039

[Snowmad79]

The 00z charts this morning showed what a struggle it was going to be to get that retrogression north but the 06Z and 12Z have followed on to show an improvement from 00z in the respect of WWA north and the vital link up and it appears the charts still arnt sure whether the HP core retrogresses north or stays over or just above us and so that easterly tap still looks a little bit of a struggle. Never the less some good runs again today even though the cold is still in FI but as ever these type of senarios take ages to gather momentum.

Be interesting to see what the other two models show on the 12Z's.

Ps. Gratz on the 348 thread member count

Edited December 7, 2009 by Snowmad79

[Iceberg]

METO coming out, and what will it do ?. out to 48Z atm.

[Thundery wintry showers]

Yes I think it was only about a week before.

As for the likelihood of a cold snowy easterly or north-easterly incursion I think 40% is a fair estimate, though I could add another 20% for a brief moderated burst with wintry showers but marginal temperatures. Then I'd award the other 40% to a cold dry spell.

[bluearmy]

the options for the block forming over us at the w/end are beginning to reduce. it looks as though the southerly jet will take lower heights across to our south preventing it from sinking. ecm op 00z would have you believe that shortwaves to our north will prevent it from ridging to its arctic cousin providing us with a ne or e flow. if the WAA up the west side of greeny courtesy of the eastern canadian depression late this week doesnt have enough oomph, then the atlantic will be knocking from the west and it wont be able to retrogress to a greeny block. it may well turn out that it just sits there, above us for a fair old while. thats what the ensembles have been telling us but we've talked ourselves into believing that they are just slow on the uptake when it comes to an easterly. if we can bear the wait, we will find out in a couple of days when the track of that low out of canada interacts with the blocking from the arctic. WAA or not WAA, that is the question.

[mountain shadow]

This time tomorrow we will be inside T+144, that's when the real nail biting begins as the models pick up on smaller shortwave features, however if that initial northerly WAA gets as far as Svalbard, we are definetly in business.

[snowmadchrisuk]

UKMO +144 .. Still looks good to me .

[Iceberg]

Meto out to 144 is out and has a bizarre little SW out over Scandy land, I don't think this would stop the high goes north due to the WAA up over western Greenland, and might help to advect the cold air SW more.