Model Output Discussion: 12Z (20/11/12) And On...

[bluearmy]

Has anybody set eyes on the rather epic JMA 12z? 1050mb Arctic high + much colder uppers arriving by T192.....

Very similar to the ECM, look at the heights stretching from Greenland to Russia.

http://www.meteociel...&nh=1&archive=0

Jma does have a bias for colder 850's . (Dont shoot the messenger!)

Good pressure upper pattern though

[summer blizzard]

Has anybody set eyes on the rather epic JMA 12z? 1050mb Arctic high + much colder uppers arriving by T192.....

Very similar to the ECM, look at the heights stretching from Greenland to Russia.

http://www.meteociel...&nh=1&archive=0

Thats an interesting one, seems to be caused by the split occurring east of the UK.

[xioni]

Excellent EC ensemble tonight with very good consistency

The N.Atlantic ridge remains very strong all the way to +360h with the NAO index approaching 2 sigma negative in early Dec and the strato becoming more & more disturbed

hopefully some impressive op runs tomorrow

[BLAST FROM THE PAST]

Jma does have a bias for colder 850's . (Dont shoot the messenger!)

Good pressure upper pattern though

And a model that MetO rate highly....

Also a Q for steve Murr...............you said great UKMO run? I have to say I don't see it. Not that it isn't, is there a different view of it?

BFTP

Edited November 20, 2012 by BLAST FROM THE PAST

[chris55]

And extended ensembles none too shoddy either;

I like the cold outlier!

That's the coldest mean for the last 4 days of any run so far.

Edited November 20, 2012 by chris55

[Cloud 10]

And a model that MetO rate highly....

BFTP

The JMA did fairly well for today's pattern at 6 days out although i must confess

its the first time i've ever checked it!

today.. 6 days ago..

UKMO at 6 days out a bit wide of the mark again,seems to be going through a sticky patch

at the moment.

Edited November 20, 2012 by Cloud 10

[snowking]

And a model that MetO rate highly....

Also a Q for steve Murr...............you said great UKMO run? I have to say I don't see it. Not that it isn't, is there a different view of it?

BFTP

And 500mb heights verifying better over 30 day average than the UKMO...

SK

[Thundery wintry showers]

The ECMWF ensemble mean continues to place the trough to the E and SE of the British Isles feeding in a rather cold and showery-looking north to north-easterly airstream from T+168 onwards, rather like the GFS 12Z operational run:

http://www.wetterzen...cs/Reem1921.gif

A fair number of wintry showers (sleet/rain near coasts, possibly snow inland especially in any heavier precipitation) can be expected if that setup comes to fruition- and no sign of significant support for anything with "mild" in the description out to T+240, judging by the mean outputs. It looks like the ECMWF operational run was a bit of an outlier in sending the main centre of the trough south-westwards. Of course with the critical period lying at T+144-192, there is scope for change but at the moment the cold showery north to north-easterly looks like the most likely outcome.

Edited November 20, 2012 by Thundery wintry showers

[fergieweather]

hi ian,you posted earlier that you would give your thoughts on any snow which may or may not occur over the next few weeks???

Sorry - really up to our necks here with a moveable feast and worsening signals from current models and hydrological assessment for tonight's event, let alone worrying about model stuff for the future! I will get back to this with better time allowing - apols Mods - back to topic now (albeit the here-and-now dramatic model output is arguably more compelling to discuss than stuff into the future!!)

Edited November 20, 2012 by fergieweather

[bobbydog]

blocking is coming, fact. where it goes - nobody knows....

i've been model watching for about 3 years now, and still know relatively little. however i can read and do take in what the experts say. i think we have established that the GFS does not show what will happen but what may happen. as has been said countless times- it shows trends not exact details. there are endless posts (including this one now) on a daily basis, stating this fact. so people should realise this fact by now- if not, then some are not reading the thread properly.

each run shows one of wide range of possibilities as to how the weather might turn out.

what people should realise is, the models are not sentient beings, trying to predict the weather, they are computer runs, programmed by real people using a huge amount of data from many different data recording sources. the data is input before each run. if someone inputs a piece of data incorrectly, or one of these sources malfunctions or is showing false data due to local anomalies at the time, this will affect the outcome massively, 15 days down the line. hence the wild variations of each run. even without mistakes or anomalies, there are many different evolutions of the weather, due to natural, even unforseen fluctuations.

therefore when the experts say look for trends, they are telling you to look for things that, despite any errors etc, are unmistakable trends. - in this particular case - greenland blocking. it will happen. to what extent, we don't know yet. neither do the experts.

if a butterfly flaps its wings in siberia....... (its obviously not very cold!)

[legritter]

tonights modell out put and data is where i was hoping it to be at this stage .so alot of very interesting weather taking place in most areas of the UK .looking into next week it does look like the Building blocks of high pressure to our north or n/east will start to take shape .but this is 6/7 days away ,so we will see the modells firm up each day .its great being back on line as i lost internet connection last saturday ,Router problems ,so i got out my collection of ROY Meteorological magazines all 300 ,i would say to new posters etc take a good look at fax charts and dont race to far ahead ,listen to regular posters ,and pop into the learning area .And as we all know looking at charts severall days ahead only gives us the broad pressure pattern ,snow quite often pops up unexpectantly .cheers gang .

[bluearmy]

comment re naefs 12z. Second run that expands the euro trough over us as the scandi trough develops in two weeks. This as the n atlantic high anomoly drifts towards canada somewhat. stewart has commented on a ridge that drifts to and fro so no worries. Strangley, as the anomoly retrogresses, so a mean ridge becomes more apparent over greenland and the downstream trough sharpens near us. I'm not too confident in gefs fi at the moment so not sure whether to take too much from naefs but its a model that rarely lets me down so i feel like i'm abandoning a mate! if we can get surface cold in then a trough expanding over us from the continent would be fine. still no firm indication from 850 spreads that we are likely to see any rush of very low uppers headed our way.however, under low heights with a slack flow, that is less important. I'm rambling now so i'll sit back and have a laugh watching th 18z trying to work out how to resolve the vortex split in fi.

[Matty M]

People must remember how our 2010 once in a 50 year cold period developed. From a situation very alike what is forecast in 7 days.

2010 20th November

Projected Forecast 27th November 2012

Edited November 20, 2012 by Matty M

[January Snowstorm]

Well the 18z is trickling out and there is already better ridging into Greenland at 114hrs.

I sense an absolute cracker of a run could come this evening!

[Continental Climate]

not sure about this run could be a bit of a GFS stinker coming up http://www.wetterzentrale.de/pics/Rtavn1201.png!!

[london-snow]

The 18z is up to 126 now and looking a lot better than previous. In fact the contrasts between the 132 earlier run and the 126 now is amazing to say the least.

Apologies as i was not looking properly - Actually very similar chance of some back edge snow from that system that is clearing the south east monday morning maybe?

Edited November 20, 2012 by london-snow

[chionomaniac]

I'd like you guys to explain what you are seeing that is better or worse.

Thanks

(PS otherwise posts that suggest a run is better or worse may disappear due to the confusing contrast of opinions)

Edited November 20, 2012 by chionomaniac

[swfc]

I'd like you guys to explain what you are seeing that is better or worse.

Thanks

lol,its virtually identical!!!!!

[Geordiesnow]

I'd like you guys to explain what you are seeing that is better or worse.

Thanks

Yes two completely opposite views on the model output just then which no doubt will make it confusing for new members!

As it happens, I think this run is more or less identical to the 12Z, you will get slight variation but all in all, upto 132 hours, its hard to split the 2 model output runs. Most certainly nothing like the ECM is showing regarding a low pressure in the bay of biscay coming into play for example.

In fairness, I rather the GFS runs being more accurate than the ECM run in the medium term, much brighter weather(for some) and cooler weather with some wintry showers potentially in the NW! The ECM looks cold and for some wet.

[BLAST FROM THE PAST]

What 18z shows is Atlantic ridge west of UK/Ireland at t144 is slightly centred further north and trough sinking to SE quicker. Should bring a NE/E flow quicker. Yes a slight neartime upgrade.

BFTP

[SMU]

Cough- JMA - I recall punting the JMA being at the top of the tree a few days ago-

Ok, so we cannot say here nor there on that- however the JMA looks great tonight-

The runs that are showing the UK uppers in the long term getting very cold-

JMA, ECM ensembles ( SOME ) will ALL come from some form of trough dropping down the western flank of the stationary vortex over russia to keep it creeping west-

As siad though theres 2 ways to skin a cat & theres still the option on the table for cold coming around the pole.

another 48/72 hours to get us a clearer picture of what will happen- in terms of UK cold this is a CLASSIC pattern where LUCK & timing is needed. I would say theres a 90% chance of the -10c uppers coming across europe in the next 10-13 days-

however those final 200 miles or so across the north sea is always the biggest stumbling block- although to offset that & where Ians even mod dern win ter has been somewhat tempered is the fact that the boundary may have been shunted back west in the last 5 years where the jet has been slower....

& BFTP on the UKMO-

http://www.meteociel...44-21.GIF?20-18

Allignment of russian high & trough below looks good for westward advection out of russia.,.....

S

Edited November 20, 2012 by Steve Murr

[Backtrack]

If my memory allowed me I could quote at least 3 winters when pretty much that happened, in the teens to snow overnight in one instance, I think, January 1955, and at least two others.

Yes John of course it can happen easily, but what I'm saying is if there's no cold air source to tap into, how can it snow? For it to snow uppers need to be -5C or below for snow at sea level, they can be significantly higher in a frontal event but it can't snow with no cold air aloft at all, can it?

[Matty M]

The overall upper pattern looks very positive on the 18z run. Important not to pay too much attention to SLP at this point.

[Continental Climate]

I just thought there was less ridging up to greenland when i initially posted and being a relative newby myself i thought we wanted more ridging up to greenland (mental note, dont comment until run is out)

[Ian Brown]

The teapot is not the issue Steve because in those days, these projected synoptics would be unthinkable anyway.

The imponderable is getting the cold uppers here and maintaining the block, we need the upstream pattern to remain favourable, it's difficult for a block to hold around Svalbard unless you get an excess of energy going into the Southern arm.