Model Output Discussion

[grab my graupel]

A new Model thread

please remember that this thread is for discussing the model output, and there are

separate threads available for general cold weather chat and ramping/whining etc.

Cold Spell Discussion:

Whining thread :

Ramping thread:

Please continue

[yamkin]

I'm impressed so far

NOGAPS is impressive too

even if that high sinks, it should lead to a northerly, and not the toppler variety either.

S ee why I'm impressed so far

[kold weather]

12z ECM is a much better run then the 0z ECM, not as good as the 12z, not even close and the evolution of the low pressure coming out of Newfoundland at 216-240hrs looks massivly odd to me BUT saying that no doubting thats a good run, would get some mega low temps from the 240hrs chart thats for sure!

Long term evolution though is no where near as good, but the ECM once again has certainly moved back inline with the GFS IMO, which is a good thing for sure!

[cyclonic happiness]

I'm impressed so far

even if that high sinks, it should lead to a northerly, and not the toppler variety either.

[NorthantsSnow]

ECM not brilliant at T240. Pressure too high over the UK still and the high just sort of stalls in the Atlantic. The cold snowy weather is further south and east over France, Belgium and Switzerland.

[disco-barry]

Haha it will rain next week now, Paul Hudson on BBC Look north has just said a cold easterly next weekend....When he usually mentions something it usually doesn't happen.

[nick sussex]

12z ECM is a much better run then the 0z ECM, not as good as the 12z, not even close and the evolution of the low pressure coming out of Newfoundland at 216-240hrs looks massivly odd to me BUT saying that no doubting thats a good run, would get some mega low temps from the 240hrs chart thats for sure!

Long term evolution though is no where near as good, but the ECM once again has certainly moved back inline with the GFS IMO, which is a good thing for sure!

Well to be honest i think the ecm is great, i can see though that it might favour more eastern and se areas, it would be extremely cold here in sw France with that ene flow,considering last winter we had a max of only -2 off a much less potent flow. I think whats really frustrating is that all those wonderful synoptics could implode around the 144hrs mark if we dont get sufficient WAA into the north with subsequent pressure rises to stop any further shortwaves from running east.

[SP1986]

Fi will be FI, and whether you choose to believe it is up to a personal view. At least the easterly is is creeping inside FI. I still have the feeling the models will change their outlook somewhat as generally it's a little different to yesterday but to be fair it would be unreasonable to expect a pattern to stay very similar for days on end. The ECM though I agree has a more potent easterly but the fact it's changed again from the 0z suggests the models are still 'finding their feet'

[TEITS]

I apologise if these have already been posted but the GEFS ensembles are terrific and are finally beginning to agree with the operationals.

Here are the GEFS mean charts at +144 and +180.

http://91.121.94.83/modeles/gens/run/gens-21-1-144.png?12

http://91.121.94.83/modeles/gens/run/gens-21-1-180.png?12

Splendid to see this agreement especially at +144. Also the SLP mean in Iceland has risen considerably and for Cambs the 850s have now dropped to -7C!

[johnholmes]

I will be posting a blog trying to give a balanced view of the pattern change, what caused or is causing it, comparing the models out to T+240 and giving my views on it.

Should be out in about 1 hour-I'm just waiting for the Net Weather Hemisphere charts to update to 12z.

[snowmadchrisuk]

The ECM is going the longer way round though 6-8 deg 850's still on the 14th .

[yamkin]

ECM not brilliant at T240. Pressure too high over the UK still and the high just sort of stalls in the Atlantic. The cold snowy weather is further south and east over France, Belgium and Switzerland.

ECM is showing a trend which is very important which is impressive in my book

GEM, JMA & NOGAPS to follow this impressive trend

[Geordiesnow]

I think with the current charts, we could potentially have something quite "special" or it could end up all horribly wrong. The margins between success and failure for a cold weather fan is so thin at the moment.

Whilst the ecm is pretty good, i would still prefer the models to trend towards the GFS more but i can't help but feel a shortwave will develop(which may help us or blow it up) however UKMO did hint at a shortwave free run yesterday so it is possible.

I'm fully confident a cold snap/spell is certain but the dry type and not the one where we see any white PPN falling.

Edited December 7, 2009 by Geordiesnow

[cyclonic happiness]

The ECM is going the longer way round though 6-8 deg 850's still on the 14th .

But at least we will be clocking up some good frosts and maybe inversions? and getting the ground nice and frozen for any snow that may fall?

Hope this goes well, the 18z is gonna be pure torture lol!

[Iceberg]

ECM isn't great, due mainly to the slightly less WAA at 144Z than GFS, this keeping the HP slightly further south, but that's being really picky.

Still a reload afte 240Z looks good.

[kold weather]

The only problem with this set-up is that it requires quite a lot of small parts to move correctly to get the best of the cold shot. The models today succed however its quite possible that if one part fails we will miss out on he deep cold and instead get stuck in the cold high pressure set-up, which still would be decent enough for the early days of winter, how many legendary cold spells and winters got going this early, even 1962-63 was only showing teases.

[cooling climate]

Even if we were to get a half way house between the GFS and the ECM we would still

be in for a very cold and quite possibly wintry spell ( at least several days).

The way I see it is that even if the shortwave does develop at t120( I am not sure it will)

because we have the Arctic high to back up the ridging the shortwave would not have

the effect that it normally does, IE collapse the block.

The Arctic high is dictating the whole pattern but yes I agree another two days just to

put it beyond doubt.

[Frosty.]

ECM not brilliant at T240. Pressure too high over the UK still and the high just sort of stalls in the Atlantic. The cold snowy weather is further south and east over France, Belgium and Switzerland.

I'm a bit concerned that the very cold air only slowly edges SW'wards towards the uk on the ecm 12z, there is no real momentum and the main thrust of frigid icy air is further southeast as mentioned, however, it would still bring a wintry spell to the uk just after the middle of next week.

[TEITS]

But at least we will be clocking up some good frosts and maybe inversions? and getting the ground nice and frozen for any snow that may fall?

Hope this goes well, the 18z is gonna be pure torture lol!

If the ECM verfied then on the 16th Dec (+216) you would find snow showers across E areas from around Humberside to Kent with these lasting only around 24hrs. I don't agree with Steve M about -15C upper temps because IMO the +216 chart would bring upper temps between -5C & -10C (-10C in the SE).

Whilst the 12Z ECM is undoubtedly better than the 0Z I would much prefer the GFS outcome especially after +240.

Edited December 7, 2009 by THE EYE IN THE SKY

[mcweather]

I seem to remember a number of those on here with far greater scientific and meteorological knowledge than myself telling us that if there is fairly good agreement between the control and the operational run on the GFS ensembles then things are more likely to come off. tonights 12z GFS ensenmbles seem to me to show pretty good agreement.

[Cecil Hogmanay Melchett]

If the ECM verfied then on the 16th Dec (+216) you would find snow showers across E areas from around Humberside to Kent with these lasting only around 24hrs. I don't agree with Steve M about -15C upper temps because IMO the +216 chart would bring upper temps between -5C & -10C (-10C in the SE).

Whilst the 12Z ECM is undoubtedly better than the 0Z I would much prefer the GFS outcome especially after +240.

I think ecm op run will be one of the cold pack for De bilt Dave,its certainly a massive improvement on the

0z run.

ECM ens awaited with a bit of interest!!

[TEITS]

if this was to come off would western wales/ south west england get any white stuff?

If I was honest the details will never be sorted out until we are +72hrs away. However I will repeat what I said earlier about potential blizzards in the SW/Wales. If we do see a Greenland block with LP systems tracking to the S then locations such as SW/Wales could be at risk. Many people think that the SW England escapes cold, snow which at times is true. However some of the most famous blizzards to hit the UK have actually occured in SW England/S Wales.

Before anyone accuses me of ramping this scenario has been shown on the GEFS ensembles which isn't surprising considering the overall synoptics.

[Andy_]

the best part about this -predicted- cold spell of weather is the comparison to this years easterly in february,

http://www.wetterzentrale.de/archive/ra/2009/Rrea00220090202.gif

notice the lack of 'mega' cold in europe compared to the +192 GFS

http://charts.netweather.tv/gfsimages/gfs.20091207/12/192/h850t850eu.png

in my opinion i would take this easterly over the feb '09 one as it could be more influential later on after the initial blast, whereas in feb '09 after a northerly later on that was pretty much it. i knoww this is still in f.i, but the difference is sooo much better in the +192 GFS even if it doesnt show that extent of -10 upper air reaching the country ( i realise it does to southern england later in the run - but i'm more concerned about my doorstep lmao). Also in the case of the 12Z GFS the cold will stick around for much longer - especially in europe - where tiny significant changes in the position of high pressure could more cold our way, and the low pressure systems which could affect the very southern edge of europe on that southerly jet makeing for a veryy attractive situation with huge snowfalls for the majority of the country if everything goes right.

yess f.i i know but still, with all the major models on board, the ECM 12Z today and yesterday have been awesome, along with the UKMO. and the JMA doesn't count ha its a nobody

[kold weather]

Eye, I think actually it'd be between both your figures, the thickness is around 515-518 so I'd expect as you say something between -8 and -12C. Still as Feb 09 showed, 24hrs really is all you need in a good easterly flow!

Overall I agree totally with Ian, there is something a little odd about the 12z GFS evolution, it can happen but it does seem a rather unusual evolution, make no mistakes though, it would be the best evolution. The UKMO is slap bang in the middle of them, and *importantly* agrees with the GFS over the angle of the jet, unlike the 12z ECM which is less keen on developing cut-off lows as soon as the others do.

So in conclusion, all the 12z runs are good and I think the charts could be a million times worse in a top end moderate El nino believe me!

[johnholmes]

the blog I've promised is in the link below-its a pdf file so you need to open it to find out what it contains!.

http://forum.netweather.tv/topic/57953-the-predicted-pattern-change/

consider it a jh Xmas present come early!