192 replies to this topic

[Paul]

Model discussion - I'm kind of hoping everyone knows the drill at this point...

Apologies to everyone who made a sane post in the previous thread btw, a clean start was needed though.

[Steve Murr]

I will endeaovour to keep posting to the guidlines-

ECM short ensembles VERY VERY good
S
http://www.knmi.nl/e...M_06260_NWT.png

[cold snap]

Steve Murr, on 14 January 2012 - 20:39 , said:

I will endeaovour to keep posting to the guidlines-

ECM short ensembles VERY VERY good
S
http://www.knmi.nl/e...M_06260_NWT.png

steve there looking very good.ecm 240 is very complex.have you ever seen a chart like it.ive never seen such difference of opinion even by experienced members on here and on other websites

[weathermaster]

My post on the weather models this evening can be found here http://forum.netweat...r/page__st__320 top of the page


This can now be found further down the page.

Edited by Osbourne One-Nil, 14 January 2012 - 20:51 .

[THE EYE IN THE SKY]

ECM mean.

http://www.meteociel...H1-240.GIF?14-0

Im becoming increasingly confident of the outlook now. Simple summary is turning colder next weekend with snowfall possible in some areas. Thereafter remaining cold especially towards the SE but Ireland/NW may turn slightly less cold. Going even further the combination of blocking remainiing to the NE, trough into Europe, PV to the W of Greenland means further undercutting is possible which may lead towards an E,ly developing.

[nick sussex]

The ECM ensemble maps have some very nice looking charts for cold and snow potential, a definite upgrade from the 00hrs run:

http://www.ecmwf.int...t!2009112700!!/

[Steve Murr]

cold snap, on 14 January 2012 - 20:43 , said:

steve there looking very good.ecm 240 is very complex.have you ever seen a chart like it.ive never seen such difference of opinion even by experienced members on here and on other websites

very rare to have a diffluent jet in that locale- its normally a very uniform Easterly flow going across Iceland-

However-
trying to illustrate an example of sorts of the ECM from the past I refer to this-
Even though it will inevitably change what we have on the 12z run is what we SHOULD be discussing-


Without trawling the archives I will post up a similar evolution- NOTE it has SIMILAR COMPONENTS-


* Wedge of high pressure over Iceland moving into Scandi & a strong Southerly jet streak-



http://modeles.meteociel.fr/modeles/reana/1986/archivesnh-1986-1-26-0-0.png

You will see it appears things are toppling- however if the jet axis is VERY North West >> South east ( very accute) then the flow goes like this

http://modeles.meteociel.fr/modeles/reana/1986/archivesnh-1986-1-27-0-0.png

whats to note is the low pressure is sliding south but pressure remains over scandi-

http://modeles.meteociel.fr/modeles/reana/1986/archivesnh-1986-1-28-0-0.png

On this example the jet just gets to the east of the meridian- so we think its all over?


next day-#



http://modeles.meteociel.fr/modeles/reana/1986/archivesnh-1986-1-29-0-0.png

a very elongated pattern


leading to this



http://modeles.meteociel.fr/modeles/reana/1986/archivesnh-1986-1-30-0-0.png

& finally this-



http://modeles.meteociel.fr/modeles/reana/1986/archivesnh-1986-1-31-0-0.png

the basic premise is that with our hemispheric pattern with BIG +VE heights lurking out towards Moscow - any residual HP building over scandi allows another westerly push of the cold-


S

[Matty M]

Quite a spread of ECM postage stamps

Seems a split with around 50% showing a decent easterly flow, 30% showing cool westerlies moving through and the other 20% somewhere in between (Akin to OP)

[Osbourne One-Nil]

weathermaster, on 14 January 2012 - 20:32 , said:

Argh just spent 30 minutes checking the charts and writing this up and can't post it anyway will post it here.


Review on the weather models this evening,

GFS

The GFS has shown a sign of improvement at 120 hours. Comparing it with other models it has moved the ridge up in the Atlantic closer to Greenland this is an improvement overall however most models suggest it should be a little bit more North. The GFS is slowly getting there. If we look further down in the Atlantic we see some things the GFS lacks support on. The other models have the high pressure more South West. At 144 hours it just shows high pressure over the UK a rather flat outlook but the GEM model has stepped over and agrees with the GFS on this not by 100% but they do look alike. Going into FI on the GFS that's the last week of the month it continues to show colder weather which would give snowfalls for most of the UK. Overall the GFS has shown some signs around 120 hours with the ridging but in general is still with out much support tonight.

JMA

I think I've read people saying this is the best run of the night for cold weather fans and it does look very good. One interesting thing about the JMA tonight is its very similar to the ECM giving it excellent support. In the JMA FI it does look colder than the ECM's with a cold pool of air over Europe.

ECM

At 120 hours the ECM has downgraded the blocking slightly once again but it still shows excellent charts tonight and overall does stick to what it has been saying for the past few days. It has good support tonight from the JMA, NOGAPS and most importantly the UKMO. GEM has backed off from the ECM's idea though and moved towards the GFS. Still the ECM is seeing better support than the GFS tonight. So the ECM does still bring colder weather in for later next week and its FI is an improvement from this morning showing plenty more chances of cold weather at the end of the month.

GEM

Not really a great run tonight as it supports the GFS more than the ECM. But because it looks similar to the GFS it would probably bring in colder weather at the end of the month eventually.

NOGAPS

Doesn't show a strong blocking but does support the ECM tonight. In the NOGAPS FI the blocking doesn't last long but there is plenty of cold weather around the UK.

UKMO

It's almost identical to the ECM so again the ECM has very good support tonight. The UKMO does show a stronger blocking than the ECM and would last much longer while the UK gets its cold weather.

Overall the GFS has moved towards the ECM side of things early in the run but at longer range still goes with mild settled weather eventually getting colder later. GEM has jumped over to the GFS tonight. Despite the GFS gaining some support the JMA and UKMO completely back up the ECM and even NOGAPS shows support. At the moment its 4 against 2.

Tonight to Wednesday Summary: For the rest of the weekend settled and cold for most but some windy weather over Western parts. Monday should continue this and as we head into Tuesday it will remain settled in the South but unsettled in the North. Wednesday will be mainly settled only in the far South of England meanwhile most will see wet and windy weather with severe gales over Northern Scotland.

Thursday to Saturday Summary: On Thursday the South seeing settled weather but the North unsettled and getting much colder possibly wintry at times. On Friday the cold weather should push down South its unclear if wintry weather will come with this though. Saturday becoming settled and temperatures should rise in the North meanwhile the South unsettled and cold.

Saturday and Beyond: Unsure exactly what we can expect but at the moment cold weather could stay with us until the end of the month.

[bluearmy]

the ecm ens mean is complex. looking through the postage stamps, there are more than just a few members that look more akin to the gfs op and then drop the trough just to our east T192. i think thats why the mean is reinforced with mean troughing at that point in time. clustering is also confusing with as many members seeming to want a deep depression around iceland T168 as building heights. spread at T144 still shows the risk for the initial trough to be further west remains. the spread on uppers is very difficult to work out but running through the later timescales it isnt certain by any means hat the flow will not be noreast.

http://www.ecmwf.int...anner/page.html

the Reading epsgram showing that the run is cold but not frigid as per this morning.

[nick sussex]

bluearmy, on 14 January 2012 - 21:01 , said:

the ecm ens mean is complex. looking through the postage stamps, there are more than just a few members that look more akin to the gfs op and then drop the trough just to our east T192. i think thats why the mean is reinforced with mean troughing at that point in time. clustering is also confusing with as many members seeming to want a deep depression around iceland T168 as building heights. spread at T144 still shows the risk for the initial trough to be further west remains. the spread on uppers is very difficult to work out but running through the later timescales it isnt certain by any means hat the flow will not be noreast.

http://www.ecmwf.int...anner/page.html

the Reading epsgram showing that the run is cold but not frigid as per this morning.

That still looks very good though compared to the GFS, and the maps show of course some good, bad, ugly and excellent outcomes!

I think if we get the trough to drop down favourably and displace the Azores high with strong block to the east then its going to be down then to the PV and where that energy goes.

[OldMetMan]

I'm finding the model progression over the last week fascinating.

Two things that are catching my eye still. The intense HP over Russia is still being forecast by all the main models, and has a potentially significant role to play if the ECM end-of-run pans out - linking to HP near the UK as LP pushes towards Greenland with the chance of cold air filtering SW towards us. It was this kind of development I had in mind yesterday to happen sooner but with more model consensus today for the current block to dissolve, seems we'll have to wait a bit longer.

The other is the continuing amplification of the upper trough in the E Pacific which I still think could have a significant downstream effect - a ridge/trough pairing that could allow for an upper ridge to the NW and N of the UK and a European trough extending SW..

The GFS seems to have kept to a fairly consistent theme up until around 120Z but seems to have gone off in various directions after that in its different runs but it basically once more carries on relentlessly with the mobile development, in stark contrast to the ECM.

Once again, I shall look to the UK Met charts for the longer term trends.

Edited by OldMetMan, 14 January 2012 - 21:23 .

[nick sussex]

I think given the timeframes involved we really need to see some movement from the GFS 18hrs run. NOAA did talk about a large spread of solutions at T-84hrs regarding the speed of low pressure towards the ne USA.

Even if we see some trend towards the Euros without a big leap that would be a positive, I do sense the need for this opportunity to be taken as once we get troughing into the heart of Europe and with that block to the east this can at least put up a fight against that PV.

Anyway all will be revealed shortly!

[happy days]

18Z GFS coming out now i must say the divergence between the American European models at such a close range is staggering.
It may well be this is not resolved until tomorrow!!
ECM continues to offer varying solutions in later frames as to be expected i suppose but that anticyclone over NWRussia on the 12z run looks absolutely huge im not sure that would budge very easily at all.

[JonMillar]

GFS-ECM Comparison spreadsheet from the last 3 runs.

Attached Files

•  2012-01 500hpa + SLP GFS-ECM Comparison.xls   3.12MB   86 downloads

[kold weather]

As others have said already, the 12z ECM probably would lead to a Continental flow, now whether that translates to an easterly is a slghtly different story but I'd feel confident that the 12z run would go cold.

ensembles seem to be in better agreement on the 12z ECM.

[Cloud 10]

At just +60hrs the 18z has changed the angle of the jet to much more of a NW-SE direction compared
to the 12z.

This should mean low pressure doing the same later in the run,which would be more in line
with ecm/ukmo.

[bluearmy]

the jet at T84 with the low exiting the eastern seaboard slightly weaker and bit more energy into the southern arm. will this be enough to slow it down ????

T96 - the answer is probably yes as i doubt the jet streak at T114 will be as strong, the vortex is slightly further west and there is a bit more amplification. nearer to home, the flow tends se as mentioned above and heights more pronounced around svaalbard. hhmmmm

maybe not then. how i hate commentating on a run .................... i'll get my coat !!

Edited by bluearmy, 14 January 2012 - 22:19 .

[Grimsby Snow Lover]

http://cdn.nwstatic..../93/h500slp.png gfs +96

http://cdn.nwstatic..../ecm500.096.png ecm 12z +96

Well up to this point in the run the 18z has moved a lot closer to the ECM run, pretty identical really. The jet position has shifted and there appears to be a build of pressure between Scandi and Greenland. Fingers crossed for some cross model agreement.

Edited by Grimsby Snow Lover, 14 January 2012 - 22:20 .

[damianslaw]

I've said before in set ups when the ECM and GFS offer very different outlooks - eyes should be on UKMO and today it is firmly siding with ECM. Met office update suggest cold and wintry conditions next weekend as well - the met office forecasts have been very good all winter and the fact the met are saying colder and wintrier evolution next weekend, makes me question GFS today as I have been doing all week.


I said yesterday how I expected ECM to back down from its quick evolution to an easterly but in its longer output continue to suggest a cold flow off the continent of NE flow and this has happened, I was also right with GFS backing down slightly from the over the top zonality it was showing yesterday - I'm still thinking both models will finally grow closer together but it will be GFS that has to make the biggest climb down.

Longer term trends are for much colder conditions as head into february and certainly not a blow torch atlantic of westerly dominance.