Model Output Discussion - 8th December Onwards

[cooling climate]

Obviously the 06Z does not want to send energy SE but if you flick between +96 and +144 you will see the HP to our E is actually backing W and slowly winning this fight.

http://modeles.meteo.../gfs-0-96.png?6

http://modeles.meteo...gfs-0-144.png?6

In these situations if the HP continues to back W then eventually you will see the undercut, its just a case of when!

Starting to happen.

http://modeles.meteo...gfs-0-162.png?6

At +162 the 06Z is actually better than the 0Z!

Comparing the 06z to yesterday this run has continued the trend in holding the energy in the

Atlantic back further west and south. As you say flicking back from the 0z to the 06z the high

to the east is trending further west.

These changes should make for an interesting afternoons model watching hopefully.

[Davey80]

We just need something now to drag in the colder air out east

[TEITS]

Seen enough of this run to make my summary. Im going to use my options again to clarify this.

Option 1. Mild returns with little resistance and little transtional snowfall.

Option 2. Snow at first before turning milder although maybe the far N remains cold.

Option 3. Remains cold with snow but possibly turning milder in the extreme SW.

Now 24hrs ago option 1 looked likely but now option 2 is certainly possible. Option 3 remains possible but is the outsider at the moment.

However we could return back to a cold outlook with all 3 options but this would occur much faster if option 2 occured rather than option 1.

Hope this basic summary clarifies things.

Edited December 9, 2012 by THE EYE IN THE SKY

[Just Before Dawn]

I'm really not liking the look of these shortwaves developing, from a purely IMBY perspective I'm beginning to get visions of another storm!

Yep, another dartboard low spawning a second centre further SW than the 18z run, pushing the strongest winds into the Bay of Biscay, though there'll still be gales in The Channel. Looks nasty too. 06 brings it east slightly earlier too. Definately one to watch from your point of view Nick.

Edited December 9, 2012 by Just Before Dawn

[Methuselah]

And this kind if 'dead zone' (should it happen) http://nwstatic.co.uk/viewimage.pbx?type=gfs;date=20121209;time=06;ext=165;file=h850t850eu;sess=470e9039858712a06df8614fc4349946; often occurs immediately prior to a major shift in weather pattern...

I'm not sure whether putative shortwaves really matter; don't they nearly always develop in zones where two massive (but psychrometrically-contrasting) airmasses collide?

[Timmytour]

T189...Siberia looking poised to plunge!

[TEITS]

Some peachy charts coming out after this.

[UV-RAY]

Seen enough of this run to make my summary. Im going to use my options again to clarify this.

Option 1. Mild returns with little resistance and little transtional snowfall.

Option 2. Snow at first before turning milder although maybe the far N remains cold.

Option 3. Remains cold with snow but possibly turning milder in the extreme SW.

Now 24hrs ago option 1 looked likely but now option 2 is certainly possible. Option 3 remains possible but is the outsider at the moment.

However we could return back to a cold outlook with all 3 options but this would occur much faster if option 2 occured rather than option 1.

Hope this basic summary clarifies things.

There's a possibility that any mild could push as far the Midlands whilst those to the North remain cold, I'm using my experience of 78/79 which saw attacks from the SW stalling over Northern England, before being pushed South again.

[Thundery wintry showers]

The upcoming cold snap now looks like delivering next to nothing on low ground re. North Sea convective snowfalls- there will be wintry showers in the east tomorrow but only cold enough for a sleety mix on low ground, with snow on high ground, then a cold dry sunny day for almost all of us on Tuesday and again on Wednesday. However, I see a lot of uncertainty post-Wednesday.

The GFS sends a shortwave eastwards over northern Britain on Thursday which would bring rain and sleet and bring milder air in, such that the widespread frontal precipitation on Friday/Saturday would then fall as rain:

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121209/06/96/h500slp.png

However, the ECMWF and UKMO do not have this feature and as a result the frontal attack from the S and SW would be likely to see rain turning to snow as the belt penetrates north and east.

http://cdn.nwstatic.co.uk/ecmimages/20121209/00/ecm500.096.png

The ECMWF operational run then has near-average temperatures sweeping in from a cyclonic south-westerly flow, but the UKMO keeps the cold continental air hanging on for longer over the north and north-east of Britain, so all of this is well work keeping an eye on. Meanwhile there remains the possibility of significant flooding particularly towards south-western Britain.

This morning's model outputs maintain a fair amount of northern blocking into the foreseeable future. A few days ago, I overstated the length and intensity of the upcoming cold snap (on the basis of the strong ensemble support for an east to north-easterly outbreak) but noted that in the long-term, high pressure would stay extensive to the north and probably retrogress towards Greenland, but with the caveat that the UK will end up relatively mild if we get a slow-moving trough in the eastern Atlantic. At present, it looks like this scenario will arise and any future cold snowy weather will rely upon the trough shifting from the position that it is currently shown at for the end of next week.

[nick sussex]

Yep, another dartboard low spawning a second centre further SW than the 18z run, pushing the strongest winds into the Bay of Biscay, though there'll still be gales in The Channel. Looks nasty too. 06 brings it west slightly earlier too. Definately one to watch from your point of view Nick.

Yes this brings back bad memories as the major storm in January 2009 developed off similar synoptics with the shortwave developing to the south of the main troughing.

Five days without power is certainly something I don't want to revisit! This puts me in a quandary, as for you guys to have a better chance of snow and turning colder again you do need a trigger low to head into France, I'm just hoping its a weak affair!

[Ian Brown]

I'm not convinced by this feature that the 06z has across Northern parts on Weds/Thursday. Clearly the timing and the angle of attack is still open to further changes.

Beyond that, some great blocking on the 06z and if that verifies then the Atlantic can't make any more progress further East, and that then progresses to the charts that we see in the low res.

[492]

High pressure from Siberia to Greenland this morning apart from the low near to Scotland which is moving southeast. I think the models were correct at forecasting this but to see it in reality is quite impressive.

http://www.uni-koeln.de/math-nat-fak/geomet/meteo/winfos/arcisoTTPPWW.gif

[EML Network]

Collecting my toys back in the pram, ready to throw them back out again, when this DOESN'T materialize !!

Let's just all hope and pray that following runs ditch this idea so we don't get disappointed again at + 144...sorry to be such a non believer, but I just don't believe it any more, not until the same chart is within + 96 with full model agreement shall I even get excited !

[TEITS]

Impressive consistency from the GFS because although obviously their are slight differences between the 0Z/06 in distant FI the overall trend of blocking is the same with a resulting E/NE,ly flow.

Fasinating spell of model watching to come I feel regardless of the outcome.

[IDO]

The synoptics in FI are brilliant and I would settle for an early breakdown if that materialised:

http://cdn.nwstatic....ctypeuktopo.png

However we are all a bit older and wiser now and know better than to fall for this.

Edited December 9, 2012 by i'm dreaming of...

[Methuselah]

Even a suggestion of an Arctic HP nosing-down? Probably gone, by the time I post this: http://nwstatic.co.u...f8614fc4349946;

And what a wonderful Christmas Day this would be! http://nwstatic.co.uk/viewimage.pbx?type=gfs;date=20121209;time=06;ext=384;file=h850t850eu;sess=470e9039858712a06df8614fc4349946;

la la la la

Edited December 9, 2012 by Rybris Ponce

[Catacol]

Hmmm - interesting 06z GFS. Are we beginning to see a trend? Have the models gone from underestimating the energy in the vortex shard to then overestimating it?

Very finely balanced. A raging easterly - no. That's gone for this week in a pretty amazing turn around, but battleground snow certainly on the cards.

GFS FI is absolutely stunning for cold, though of course we have been here before and lulled into getting excited. However atlantic energy may well dissipate quickly with the vortex moving to Siberia, so it is quite possible that the atlantic might suddenly hit empty and at that moment the underlying signal for retrogressing high pressure will win the day.

Much still to play for here.

[chionomaniac]

I do believe that the bookies could be a little bit poorer.......

First Christmas Day chart.

[The Weather Dragon]

Latest model trends - goodbye to atlantic dominance - and a trigger low along the south coast / channel could open the floodgates.....third bite of the cherry anyone!!!!!

[Severe Siberian icy blast]

The back track continues this morning, the 06 is better than yesterday's 06 , that's what we look for, the shortwave that appears over northern Britain on this run is what kills it early , but the mod still wants to bring back cold , so I think in the long term cold will win , I don't think us run is right, I think it's slowly coming to terms with the backtracking , and I think this evenings runs will be very interesting , and I think a further shift southwest will be most evident.

[Chess01]

Im Kinda glad that the breakdown is forecast now because europe seems to get alot colder so we would have a more potential later on and it will be closer to xmas

[Methuselah]

I do believe that the bookies could be a little bit poorer.......

A nice-enough present, in itself!

[Iceberg]

By 180-192 the cold air from the easterly is back in the east of the North Sea only 100-150 miles from our shores.

As long as the models continue to push the energy southwards I see no reason why the trend doesn't continue.

The breakdown is now only limited to 3-4 days for some.

This is still probably far from the final solution though.

[bobbydog]

I do believe that the bookies could be a little bit poorer.......

First Christmas Day chart.

or richer... i wouldn't bet on it yet.....

mind you, showing a snowfest from 240 onwards, 6 days and beyond... could be worth a quid....

Edited December 9, 2012 by bobbydog

[chris55]

Short term details will obviously effect our little patch of the world with regards to snowfall and the extent of the Atlantic influence into the end of next week. However the broader long term pattern is trending towards continued blocked pattern with much interest in terms of potential cold weather.

The Pvs journey towards Siberia has caused the models some inconsistency's but as has been pointed out in the start thread height rises towards Greenland "may" be on the cards. Certainly zero sign of the PV in GFS low res over our patch. Best case scenario would be the eventual retrogression of the Russian/Scandi high into this location and plenty of cold uppers about to move with it!!!!