Model Output Discussion - 30th November onwards

[bluearmy]

Worth pointing out everyone that due to the time of year we will not require a Scandi HP to be perfectly placed and bring colder uppers to actually experience very cold temps. Any continental flow is likely to bring max temps around freezing and mins well below freezing. The only exceptions are those locations away from the continental influence. So for example it is possible that whilst Cornwall and Dublin are experiencing max temps of 11C, the Midlands/SE could see max temps of 0C!

 

Thanks for the comments everyone as I decided I would feel better by indulging in my favourite hobby.

 

and the updated london ecm ens are probably the coldest set thus far into the distance.

 

http://www.weathercast.co.uk/services/ensemble-forecast.html

[phil nw.]

I have noticed a change in the anomaly charts over the last couple of days with a signal building in week 2 for some ridging towards our NE rather than the Atlantic.

 

http://www.meteociel.fr/modeles/ecmwf/runs/2013120100/EDM101-216.GIF?01-12

http://176.31.229.228/modeles/gens/naefs/run/naefs-0-0-216.png?12

 

As the Scandi.trough is severed it leaves that cold upper pool over C.Europe.

 

The lower stratosphere 100hPa forecast also shows some ridging-

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/gif_files/gfs_z100_nh_f240.gif

 

I think it's maybe too soon to see which way this will go -with a large chunk of vortex heading towards Canada it does leave an opportunity for some height development around NW Europe/Scandinavia.

 

Welcome back Dave(teits)good to see you posting again.

 

[SMU]

I may have time to do a longer post later on the model bias & evolution but for now-

Why is the UKMO EPIC today- well apart from the SUB 510 thickness in Northern Scotland we have the following:

 

UKMO 144

http://www.meteociel.fr/ukmo/runs/2013120100/UN144-21.GIF?01-06

Note the angle of the flow / advection is NNE across Greenland

 

BOM 144

http://modeles.meteociel.fr/modeles/bom/runs/2013120100/bomnh-0-144.png?00

Note the angle of the flow / advection is ENE across Greenland

 

The 500 MB height profiles are the same, so the subsequent evolution is the same barring the fact that the UKMO will have everything further North-

 

Now run the BOM Evolution

http://www.meteociel.fr/modeles/bome_cartes.php?ech=6&code=0&carte=1&mode=0&archive=0

 

Look at the 168 Chart

http://modeles.meteociel.fr/modeles/bom/runs/2013120100/bomnh-0-168.png?00

 

See the jet- digging way south in the atlantic & the elongated high towards Scandi- classic building blocks of the Scandi High

 

Now look at 240

http://modeles.meteociel.fr/modeles/bom/runs/2013120100/bomnh-0-240.png?00

 

PErfect 500 Height Scandi high- all be it to far south- the UKMO would be further north...

 

 

All in all- Scandi high changes 70-80%, deep cold to come back from the East around 40-50%.... however surface cold up with the 80% mark.

 

Gone are the zonal charts from yesterday..... long live the post m*dern winter.S

 

PS if the NAEFS charts are GFS builds then bin them now- or at least watch them change over the next 48 hours.

Edited December 1, 2013 by Steve Murr

[tight isobar]

My thoughts exactly, and as you say, any disturbances, which could make a big difference, won't even show up for a while yet.

..yes my personal favours scenario "nowcasting" with a certain few suprises, for some no doubt!?. Plenty of good model viewing, upon us.

I may have time to do a longer post later on the model bias & evolution but for now-Why is the UKMO EPIC today- well apart from the SUB 510 thickness in Northern Scotland we have the following: UKMO 144http://www.meteociel.fr/ukmo/runs/2013120100/UN144-21.GIF?01-06Note the angle of the flow / advection is NNE across Greenland BOM 144http://modeles.meteociel.fr/modeles/bom/runs/2013120100/bomnh-0-144.png?00Note the angle of the flow / advection is ENE across Greenland The 500 MB height profiles are the same, so the subsequent evolution is the same barring the fact that the UKMO will have everything further North- Now run the BOM Evolutionhttp://www.meteociel.fr/modeles/bome_cartes.php?ech=6&code=0&carte=1&mode=0&archive=0 Look at the 168 Charthttp://modeles.meteociel.fr/modeles/bom/runs/2013120100/bomnh-0-168.png?00 See the jet- digging way south in the atlantic & the elongated high towards Scandi- classic building blocks of the Scandi High Now look at 240http://modeles.meteociel.fr/modeles/bom/runs/2013120100/bomnh-0-240.png?00 PErfect 500 Height Scandi high- all be it to far south- the UKMO would be further north...  All in all- Scandi high changes 70-80%, deep cold to come back from the East around 40-50%.... however surface cold up with the 80% mark. Gone are the zonal charts from yesterday..... long live the post m*dern winter.S PS if the NAEFS charts are GFS builds then bin them now- or at least watch them change over the next 48 hours.

.good stuff SM..sums things nice as they stand..

[sundog]

 

 The only exceptions are those locations away from the continental influence. So for example it is possible that whilst Cornwall and Dublin are experiencing max temps of 11C, the Midlands/SE could see max temps of 0C!

 

I more often then not find Scandi HP frustrating as that type of situation can often happen with ireland being too far west and being on the wrong side of the cold .

 

Still i would rather a scand HP then say zonal weather as there is always a chance of the cold air moving further west.

[Skyraker]

Ensemble watch.

 

[bluearmy]

 

 

PS if the NAEFS charts are GFS builds then bin them now- or at least watch them change over the next 48 hours.

 

actually steve, i thought it quite notable for that very reason that the naefs anomolys (gem ens/gefs) built a decent scuero anomoly with the spreads indicating the margin for error further north)

 

06z gefs, have four or five members going for a cold easterly by T300 with the uppers spread finally getting a signal as far as the uk, despite the mean looking 'average'.  the scandi ridge looking a near certainty now (did i really write that?)

Edited December 1, 2013 by bluearmy

[radiohead]

06Z GFS operational wasn't an outlier, but I'd like to see more support from the ensembles. 18/20 members less cold than the operatinal on the 6th/7th. A slightly less cold 12Z wouldn't be a surprise, but the majority do go for a cold shot of some kind rather than a milder option.

 

http://www.meteociel.fr/cartes_obs/gens_display.php?x=298&y=2&run=6&runpara=0&type=3&ext=1

[Downpour]

I don't think it is so much that, rather people don't believe it can happen; having spent most of their model watching lives watching downgrades and topplers, it is hard to move on to the more recent paradigm, where expectations can be increased.I remarked the other day that recent weather patterns would indicate it be unlikely that such a deep trough would not leave a cut-off upper low behind and with LR modelling pointing to low heights in Iberia we could be more optimistic.

I think that's right, but after four winters of cold being the form horse maybe some members need to change their view. Decent charts this morning although now I am wondering where any ppn will come from - even though I am in the most exposed part of London, next to the cool of Epping Forest, with nothing much to capture any showers between me and the North Sea.

[Thundery wintry showers]

The main issue that I have with the Scandinavian HP bringing surface cold but relatively mild temperatures at 850hPa is that the result tends to be prolonged spells of dry cloudy weather, as the track over the North Sea produces moisture but the lack of instability results in stratocumulus trapped underneath an inversion.  For widespread snowfall you either need frontal activity or instability (as generated by cold air flowing over warm seas, preferably with the 850hPa temperature around 15C or more lower than the North Sea temperature).

 

There has been more backtracking towards the ECMWF this morning than I expected- I am still expecting the northerly not to last much, if anything, beyond 36 hours, but the potent nature of the blast looks like it could well result in snow showers becoming quite widespread for a time, with Ulster (Ireland), Wales, the Cheshire Gap zone, and north-eastern parts of Scotland and Norfolk currently looking most prone.  Away from coastal parts of the SW I'd expect showers to fall generally as snow given the temperature profiles.  However, a lot still depends on the duration of the northerly and the wind direction.

[Bristawl Si]

A proper Winter High showing its hand from the depth of Russia. Lovely jubbly

Yes.....

and to think some on here we're fretting over the land mass to our East not being cold enough the other week. It didnt take long, did it?

[Jason M]

06z ensembles are out and there is a real step change in longer term. Some very cold charts starting to show at days 10 and 11. A stronger signal for scandi heights. A couple show heights building to Greenland, but I'd ignore those completely as that would go against all the background signals and GEFS have form on that.

Obviously nothing to get excited about at that range but its nicer to look at than the last set.

Jason

[bluearmy]

06Z GFS operational wasn't an outlier, but I'd like to see more support from the ensembles. 18/20 members less cold than the operatinal on the 6th/7th. A slightly less cold 12Z wouldn't be a surprise, but the majority do go for a cold shot of some kind rather than a milder option.

 

http://www.meteociel.fr/cartes_obs/gens_display.php?x=298&y=2&run=6&runpara=0&type=3&ext=1

 

the ensembles are still struggling with the sw of greenland area. its clear that it required a very high resolution model to sort this out and the ens at 50km +, never mind the non ecm ops at 27 km +  seem unable to sort it.   i expect that by tomorrow, we will see some decent ens agreement re the depth and duration of the northerly.

[tight isobar]

06z ensembles are out and there is a real step change in longer term. Some very cold charts starting to show at days 10 and 11. A stronger signal for scandi heights. A couple show heights building to Greenland, but I'd ignore those completely as that would go against all the background signals and GEFS have form on that.Obviously nothing to get excited. about at that range but its nicer to look at than the last set. Jason

06z ensembles are out and there is a real step change in longer term. Some very cold charts starting to show at days 10 and 11. A stronger signal for scandi heights. A couple show heights building to Greenland, but I'd ignore those completely as that would go against all the background signals and GEFS have form on that.Obviously nothing to get excited about at that range but its nicer to look at than the last set. Jason

.agreed, all signals pointing n/nw. Against the grain regards Greenland (atm) ne,block's.going to be intresting to watch evolve through Scandinavia/ east euro region!!!

[Cecil Hogmanay Melchett]

So,those trumpetting a return to zonailty with the jet barrelling into Scandy may well have to think again this morning.

As the old saying goes, 'the weather can make fools out of us '...

 

Just as an aside,im still thinking a block around the UK maybe extending into the southern portion of Scandy meaning very very cold surface conditions as we head into the second week of December.  

NScotland NIreland and wales look the sweet spots for some decent accumulations AS THINGS STAND..

For those who miss out on snow at the end of the week some very seasonal weather on offer much better than Atlantic dross for the season of goodwill.

PS welcome back teits from you NW buddies.

 

Wind | Atlantic ocean forecasts | Weather forecasts | Weather | Icelandic Meteorological office

 

Hope thats not copyrighted but its the link to the  ECM 850's and precip charts.

If it is can a mod delete the link.

Edited December 1, 2013 by happy days

[johnholmes]

Especially for new folk and for those wanting to learn more about the weather, what may be a good insight into how the low at the surface will be the means of swinging deep cold air south is to watch the Fax charts. Currently the trough off the eastern side of Greenalnd is where the activity will show. The first cold front having not much effect on any major temperature change. The second one shown on the Fax charts will bring the deep cold air south. So we can all watch this actually occurring from about Wednesday onwards, look at the actual charts available and see how this works out.

Very interesting even for those not having a cold bias to learn how the atmosphere behaves, look also at the upper air charts, the jetstream charts, to see how it all fits in a 3 dimensional manner.

 

As the old saying goes, 'the weather can make fools out of us '...

 

 

very very true, amatuer and professional alike

[nick sussex]

My optimism that we will see a cold extension is now hitting 7/10!

 

I think whats been interesting this week is how this little mystery tour has developed, for newbies I hope its highlighted model bias especially regarding the GFS. Also I think it shows that everything is not always as it seems.

 

In terms of a Scandi high this was rubbished earlier in the week but we've seen these little hints come and go for a few days, because of the movement of the PV west towards Canada the next thing we were looking out for is where the energy went from that over in the eastern seaboard of the USA, the models seem to want now to send this south into the mid Atlantic and as soon as this happens then zonal sw talk hits the buffers, the evolution towards a Scandi high is actually quite straightforward with this type of set up, as long as you get the energy splitting north/ne and se underneath the high.

 

I think the issue at the moment is how far north any high can get, Scandi highs are really one of the hardest because they can offer up lots of different weather, its not like a northerly where you can say sunshine and snow showers especially for windward coasts. You can get the grey murky type Scandi high, the one with a more clearer se/east flow, the more sausage shaped high named by Mr Murr ! which often sends this thread into meltdown as its more associated with the very deep cold uppers and snow showers outcome.

 

At the moment I think high pressure edging towards Scandi is a decent bet but what exactly that finally delivers is still very much open to debate.

[Summer Sun]

06z ensembles show a steady rise in the 850's from Monday 9th still looking at 3 or 4 days for the coldest weather (either Thursday to Sunday could well be the coldest period)

 

Edited December 1, 2013 by Summer Sun

[legritter]

Yes plenty of possibilitys thurs to saturday ,if it all comes off there will be good events not even on the radar yet .very pleased with todays ECM and our friend GFS ,we all knew the little rascal would turn up trumps ,but probably plenty of prozack moments and STella runs yet to come .Certainly a good week for New learners to pop into the learning area ,take note of updated charts and especially Fax charts .well tonights ECM and Met office critical but there again i think every run lately seems critical ,lets all enjoy and learn from each other .Perhaps the Russian express next to take on the Atlantic ,as some longer range charts are hinting at ,cheers 

[Skyraker]

Ensemble watch.

 

Remember all those years where it took until Feb to get the 528DAM line into northern England?

 

Hah!.. I genuflect in your general direction.

 

Edited December 1, 2013 by A Boy Named Sue
Was that really necessary, SR?

[Summer Sun]

Here is the day time temperatures from Thursday according to ECM

 

London

 

 

Birmingham

 

 

Darlington (7c and snow looks suspect to say the least)

 

 

Edinburgh (5c and snow looks marginal)

 

 

So as we can see there it looks fairly sunny snow is shown for some northern parts but with temperatures of 5c and 7c I wouldn't be so certain

 

The north starts to see temperatures relax by the 9th  (Edinburgh's average high for December is 7c so only just below average by the 9th)

Edited December 1, 2013 by Summer Sun

[Gael_Force]

06z ensembles show a steady rise in the 850's from Monday 9th still looking at 3 or 4 days for the coldest weather (either Thursday to Sunday could well be the coldest period)

 

 

Might be time to post the T2m ensembles as well Gavin - with projected synoptics, upper air alone is very misleading.

[phil nw.]

Ensemble watch.

 

Remember all those years where it took until Feb to get the 528DAM line into northern England?

 

Hah!.. I genuflect in your general direction.

 

No argument there-a building trend from earlier in the week towards a very cold shot.

Aberdeen for a full house soon  wrt -10c uppers?

[SMU]

Ensemble watch.

 

Remember all those years where it took until Feb to get the 528DAM line into northern England?

 

Hah!.. I genuflect in your general direction.

 

 

 

Great work- now by 18z close watch how the green catches the yellow- I think 20/20 by 18z tomorrow...

 

S

[topher41]

As a very amateur mod watcher over the last three year's. I have noticed that weather events forcast for 5 days or more hardly ever come to the exact first conclusion. Either they fizzle out to nothing or get extended .getting extended seems to be a theme when the Atlantic strength seems to be over estimated .am I alone in thinking this if not why is this so is there a lack of data in the Atlantic or other areas ?