Model Output Discussion 25/11/2012 12Z onwards

[Duane S.]

The most important model run of the winter is coming up (not refering to the GFS 18z of course) and if it shows what its sister 12z run did then, unfortunately, the possibility of it occuring (although I still struggle to see that much energy bulldozing on through) will have gone up a bit.

Don't forget its hardly unpresidented that the ECM goess 'off on one' inside the more reliable timeframe. Yes a worry other minor models are hinting that way as well but I live in hope this will turn out very well for us (and that may mean having to wait a little bit longer for the good stuff).

Edited November 25, 2012 by s4lancia

[Mr Frost]

ECM Ensembles arent incredibly bad.

50-60% hold the low back at T144hrs

30-40% hold us in a cold/very cold flow at T168hrs

Yes, you get the feeling that if the Ensembles above go to a weather models related swingers party tonight they would have a go with the GFS, UKMO, JMA, NOGAPS, GEM, GME, BOM but of course leave the CFS to sort themselves out.

[LomondSnowstorm]

The ensembles are just as clueless as the rest of us in this instance.

[nick sussex]

Looking at the upstream patterns over in the USA theres really not a big difference between the big 3 over the mainland but just as this low leaves the eastern seaboard..

The point of disagreement is really how much they develop that low and the speed which it exits the east coast.

In terms of this the following from the diagnostic discussion at NOAA:

OVERALL FAVOR A BLEND AMONG THE ECMWF/UKMET/GEFS MEAN ALOFT GIVEN

VARIOUS QUESTION MARKS IN THE NAM/GFS/CMC. GUIDANCE HAS BEEN

SUFFICIENTLY VARIABLE OVER RECENT DAYS TO FAVOR A WRN ATLC SFC LOW

A LITTLE SLOWER THAN THE 12Z ECMWF... AS PER A UKMET/GEFS MEAN/00Z

ECMWF COMPROMISE.

We still though have the problem of whether it develops and runs ne/n rather than just east.

This is the latest aviation forecast for New Hampshire, bearing in mind that if it develops as the UKMO/GFS it should effect the coastal fringes.

AS AN UPPER TROUGH REACHES THE EAST COAST ON WEDNESDAY... LOW

PRESSURE WILL STRENGTHEN AS IT MOVES EAST. WITH THE UPPER LOW

CATCHING UP TO THE SURFACE LOW... THERE MAY BE SOME ATTEMPT TO

PULL THE SURFACE LOW BACK TOWARD THE COAST A BIT ON WEDNESDAY...

OR AT LEAST FORM AN INVERTED TROUGH TOWARD THE COAST. THIS WOULD

PROVIDE THE BEST CHANCE FOR ANY PRECIPITATION ACROSS THE FORECAST

AREA FROM THIS SYSTEM... WITH A CHANCE OF LIGHT SNOW ON THE

MIDCOAST.

This would indicate some deepening of the system which is preferrable.

Now looking at the ECM versus GFS/UKMO i think what it boils down to is whether we see an interaction of this shortwave engaging some energy heading out of Arctic Canada.

In a nutshell if we don't get that deepening Canadian low far enough to the west we're going to have to go to plan B which I'm still trying to work out!

Edited November 25, 2012 by nick sussex

[SMU]

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

not pretty reading im afraid...

S

[10 Days Away]

http://www.knmi.nl/e...M_06260_NWT.png

not pretty reading im afraid...

S

Good, Plenty of time for cold in Jan and Feb. Heating costs !!!

[ITSY]

http://www.knmi.nl/e...M_06260_NWT.png

not pretty reading im afraid...

S

massive downgrade on those ens. Worth waiting now for the next bunch of GFS updates and the midnighters. If we still have a split this time tomorrow then I give up. that's right Ian (TMW), my first official the winter is over post.

JOKE.

Edited November 25, 2012 by ITSY

[cyclonic happiness]

http://www.knmi.nl/e...M_06260_NWT.png

not pretty reading im afraid...

S

It's not all that bad, at least there's alot of divergence at the far end, looks ok(ish) up until Saturday, then the guessing starts proper.

[iowpompeylee]

As always the dream come crashing down....after one bad run.2 weeks of good runs then the Big Bang.at midday it was snow for most of us now its sun cream and deck chairs.wont know for sure for 2 to 3 days yet.keep the faith :-)

[nick sussex]

At the moment I'd say the ships taking on water but we still might plug the leak!

If the worse happens then its a case of yet another shortwave drama to add to the many!

For newer members this is a great link and explains longwaves/shortwaves and loads of other very useful info:

http://www.wxonline.info/topics/waves.html

[Frosty.]

Lets hope the Gfs 18z is not as scary as nightmare on ecm street

In the meantime, there is still a lot more rain to come, especially across northern england with an extra 50-70mm, nearly 2½ inches which nobody needs, too much rain already...at least the models show a drier trend through the week with the persistent rain being replaced with showers, the west becoming mainly dry, most of the showers on the eastern side of the uk, more wintry by thurs/fri.

[bluearmy]

to my eye, the ecm ens have gone with the op and shifted the energy well east of what has gone before. its not a surprise to see the ens react to the op. we've seen whole ecm suites skewed and be wrong before (generally when they showed cold). i would wait for the 00z runs before making a judgement. there is no need to do so tonight so, given the disagreement over what is a 'knife edge' feature quire early on plus modelling in an area of the hemisphere with poor data coverage, i'm not going to.

i would make the point that often in these situations, a half way house turns out to be the solution. not sure that this will be the case given the canadian low will be either a generator of WAA or a zonal train. if it were a half way house, then this mornings 06z gfs op wouldnt be too far away. if this turns out to be a chunk of the canadian vortex being dispensed to the eurasian side as the remains of the said split vortex are left to drift off towards alaska, then i'll put up with the disappointment as being worth it in the long run.

[Isolated Frost]

It's obvious that there is great uncertainty- even amongst the ensemble means.. the GEFS goes for an amplified trough with waa up Greenland- and an amplified arctic high- the modelling of the canadian low is vital and it's resulting amplification will define whether the arctic-azores linkup will occur or the atlantic breaks through- the H5 anomalies obviously disagree with the progressive ECMWF solution-

[Fozfoster]

There has been a frankly ridiculous over reaction about the ecm, its only 1 op run, is the ukmo suddenly useless? and what about the uk met office update, will 1 ecm op run trash their outlook tomorrow?

Bang on Frosty, and one Ian Brown comment in to the mix and bingo!!!! model thread goes MAD. Do like i do and block Terry Michael woods posts and the ride would be a lot smoother.

[Matty M]

The ECM Ensembles can be viewed run by run, there is a ~50/50 divergence.

They are not a nightmare and not too much different to this morning. Den Haag is quite far south and east also so it would be always vulnerable to the warm sector of the Euro Low.

[chionomaniac]

Does anyone see any potential in the following chart?

I do.

This chart smacks of Greenland height rises and a west based negative NAO.

One could be forgiven for thinking that this chart is poor given the state of affairs - but looking at the bigger picture, any Atlantic interlude could be quite brief with the background signals coming back into play.

[Iceberg]

German ens re not very good in this set up, gfs is a good example as even the gfs keep Germany quite a bit warmer than the uk.

Re the ECM ens a quick example at t144 the pressure for me on the ECM ops is 1023mb, the avg for the ECM ens is 1012mb. It shows you how little support it has.

[johnholmes]

i would make the point that often in these situations, a half way house turns out to be the solution. not sure that this will be the case given the canadian low will be either a generator of WAA or a zonal train. if it were a half way house, then this mornings 06z gfs op wouldnt be too far away. if this turns out to be a chunk of the canadian vortex being dispensed to the eurasian side as the remains of the said split vortex are left to drift off towards alaska, then i'll put up with the disappointment as being worth it in the long run.

I had typed a long reply to Ian but the magic of pc's and it disappeared so I in answer to Ian first I have not enough evidence to believe your view.

ba

I suspect if there is this half way house then the idea of the vortex itself being on the move does have credence but its the speed with which ECMW at the synoptic level is suggesting this will happen. IF again it does turn out that ECMWF is at least partly right then the overall upper air signal is that the block will re establish, well that is my view.

Does anyone see any potential in the following chart?

I do.

This chart smacks of Greenland height rises and a west based negative NAO.

One could be forgiven for thinking that this chart is poor given the state of affairs - but looking at the bigger picture, any Atlantic interlude could be quite brief with the background signals coming back into play.

pretty much what I've just posted in reply to Ian and ba chio

[Timmytour]

A lot of doom and gloom about arising from the ECM mainly I see since my last visit.

Personally I'm a GFS fan....not for the consistentcy it shows from run to run but for the way it seems to pick up on things early and then even though it drops them, comes back to them.

My hopes of a really cold prolonged spell coming up were downgraded a while ago because of what the GFS was showing, not today because of the ECM.

Of course nothing is verified yet. But I expect to see temps in the second week of December get into double figures in the south, something I had hoped, and began to expect a while ago we wouldn't see. I think GFS deserves a lot more credit than it seems to get at times.

But this is just the first skirmish of winter and there will be other occasions to come. I hope for a better one than last year though I'm pretty certain that the hope of seeing a repeat of two years ago have all ut disappeared.

[bluearmy]

so to put everyones mind at rest, even if ecm is on the right track, the end result will be an even weaker canadian vortex. short term pain for long term gain. (and the scottish ski resorts will be well happy anyway).

[Mark Neal.]

Good video done by Steve looking at the potential cold snap forthcoming hes done a weekly update to his videos.

[ChartViewer]

Even if this beautiful synoptic pattern is scuppered at the last minute by a pesky shortwave/low whatever you want to call it ill still say hats off to the experts GP, Chio etc on the Strat thread for calling this so bullishly....Doesnt matter if the end result shows a cooler zonal or as said lovely HLB i think it could be called as like Lampards disallowed goal against Gernany....beautiful long range chip, hit the bar, went in but was disallowed at the last minute!!!!

[nick sussex]

I think if you look at the last 3 sets of ECM ensemble maps at 168hrs you can see how more energy has spilled east from the Atlantic, the problem isnt so much the energy but where its being directed, with ensembles you will get sudden shifts because theres no halfway house with this situation , you either get energy under the block or its game over.

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2012112512!!/

I think given the timeframes involved if the GFS 18hrs shows a shift to the ECM then I would take that as a bad sign.

Bear in mind that the differences are starting within 96hrs and that eastern seaboard doesn't suffer from a lack of observational data like the region in which we see the Arctic high.

If the GFS 18hrs holds firm then that would certainly be very welcome!

[Ian Brown]

Does anyone see any potential in the following chart?

I do.

This chart smacks of Greenland height rises and a west based negative NAO.

One could be forgiven for thinking that this chart is poor given the state of affairs - but looking at the bigger picture, any Atlantic interlude could be quite brief with the background signals coming back into play.

It's a pretty dreadful chart for getting cold to the UK - the block cannot orientate favourably for the UK from there - and potentially worrying in terms of rainfall quantities.

The ECM ensembles are not a disaster - the OP is an outlier in the speed of the evolution but many members do support what the 0z run showed this morning by T192 onwards.

[xioni]

means can be deceiving but it has to be said that ECM ensemble mean is pretty poor at 192h

http://www.wetterzentrale.de/pics/Reem1921.html