Model Output Discussion 25/11/2012 12Z onwards

[Duane S.]

John, I'm only commenting on the NWP tonight and reflecting how similar experiences in past years have gone - generally to Paraphrase Mr Murr - the way of the pear.

The long term evidence may support a PV split with displacement to mid-latitudes, they may show all manor of reasons as to why there should be a pattern change - many times over recent years the actual has defied these probabilities and the +ve NAO has ruled.

The AO/NAO forecasts are neither here nor there because they are reflective of the general NWP.

Nothing wrong with posts like that Ian but your post of a few pages ago was a complete joke. You do know your stuff but why do you have to constantly let yourself down with trying to wind up people saying it's 'game over' when quite obviously, right here and now, it is not? Oh and I wish there was a way to ignore posters AND their quoted posts as it sort of defeats the object...

Back to the models and that really was a "WOW I wasn't expeting that !" moment at around 6:20pm with the ECM's interpretation of affairs. I suspect it is just displaying the worst case scenario. Which unfortuantely means it IS possible but would completely blow away the anomaly charts of late. I'm going for a halfway house, more UKMO then ECMEF. I honestly don't think we will see a chart that bad inside +120 from the major models for another 7 - 10 days at least.

[Snowman.]

What is wrong with ECM yes it does show a zonal pattern but towards the end heights begin to build north with a cold pool over Scandinavia if anything I would rather have the ECM shows some real potential it's more than likely not to happen but still you have 3 months of winter and this year is looking good for cold weather it only one run and here enjoy this ray of sunshine.

You can see on that chart that Height build over Greenland and stretch out with the two troughs sinking south it looks good!

[chionomaniac]

Some interesting info on the (excellent) TWO thread, that I'd thought I'd pop in here.

Verification stats are interesting to say the least,

ECM verifying on par with NOGAPS at the moment, with GFS leading and UKMO second.

Also to note is the 500mb anom charts, big differences between ECM and GFS

http://www.meteo.psu...2z/hgtcomp.html

Please note that just because a model has been better in its verification 6 days ago this has no influence of whether it will verify better in the next 6 days. So daily fluctuations in these stats mean didly squat. We are better looking at the verification rates over a longer period of time - and we all know which model comes out on top there - the ECM by a country mile!

Edited November 25, 2012 by chionomaniac

[xioni]

Unfortunately EC ensemble is making a significant move towards its op run with 40-50% of its members backing up more energy passing though eastwards.

The mean obviously will still show the op as a warm/flat outlier but it will have a much flatter pattern

It's still al up for grabs and at these time ranges op runs are more important anyway so here's to a very different EC run tomorrow morning!

[snowstorm445]

What is wrong with ECM yes it does show a zonal pattern but towards the end heights begin to build north with a cold pool over Scandinavia if anything I would rather have the ECM shows some real potential it's more than likely not to happen but still you have 3 months of winter and this year is looking good for cold weather it only one run and here enjoy this ray of sunshine.

You can see on that chart that Height build over Greenland and stretch out with the two troughs sinking south it looks good!

That looks good for rebuilding the ridge once the Icelandic depression has moved eastward, and potentially linked with the one over Northern Europe. We saw this on the GFS yesterday (albeit in FI). I know its unlikely, but its an interesting pattern to observe.

[Downburst]

http://www.emc.ncep....aphics/acz6.gif

I did say previously that I backed the ECM (basically because it's normally so reliable at t96), but I'm having second thoughts - the above model accuracy at 6 days indicates that it's been really struggling in the last few days. Additionally, thinking about it a bit more, the ECM is best at picking out medium range trends, the differences now are to do with the handing of a low pressure system at fairly close range (between t72 and t96) - which is not necessarily one of its strengths.

So it's wrong? you'll have 10 post here with people now telling us to ignore the ECM, it doesn't handle this and that and of course "it struggles" with this and that. Better to admit its the best model you have and that at times like this with a lot of new variables the operational on all models will have inaccuracies. I take your point but wait for the ensembles and a couple more days. No straw clutching on computer programs you can't control.

[UV-RAY]

Am I the only one here who finds the differences between how the UKMO, GFS, and ECM have this weeks cold spell or not modelled. It's fascinating stuff watching all this unfold and more fascinating watching people's angst ridden posts.

[Frosty.]

At least countryfile forecast looked good, a bit of a wobble as the low moves in from the west, it gets close but is then pushed back west further into the atlantic as the cold block flexes it's muscles and begins to march towards the uk from northern scandinavia and this leads into a much colder weekend with snow showers to the northern and eastern side of the uk, especially bordering the north sea, indeed, showers from midweek in the east become more wintry in nature as max temps drop to 5 or 6c and with chilly nights. Even though things look tighter this evening and more problematic, on balance it still looks like cold from the north and east will ultimately win out.

Edited November 25, 2012 by Frosty039

[Mr Frost]

I think everyone just needs to relax a bit...

In a way it is good for learning when some models suddenly flip to a completely different outcome, questions are then asked. However, the only downside is people get really depressed and then post knee jerk responses and this is down to their own bias of weather. It is only natural to feel elated or despondent but maybe rather than posting they could hang back, wait for the run to finish and then explain why they think it is good or bad? It would cut out all the unnecessary sniping,

Let's all respect each other's posts, we are all here for the same reason and that is we are all obsessed with different types of weather! Whether mild, cold, rain or sunshine be your thing, each to their own. But let's keep it friendly!

Edited November 25, 2012 by Mr Frost

[snowstorm445]

Some interesting info on the (excellent) TWO thread, that I'd thought I'd pop in here.

Verification stats are interesting to say the least,

ECM verifying on par with NOGAPS at the moment, with GFS leading and UKMO second.

Also to note is the 500mb anom charts, big differences between ECM and GFS

http://www.meteo.psu...2z/hgtcomp.html

If that Icelandic low moves out of the way we could have a very strong ridge rebuilding over the Atlantic. Certainly not a zonal pattern by any means. Look how powerful that Arctic High is.

[chris55]

The fax charts won't follow the ECM tonight. The 0z runs tomorrow will crucial and Exeter will make a judgement tomorrow.

John - we will have to see - but we are talking about the direction of a shortwave that will determine matters - the height anomalies will not be relevant.

You have hit the nail on the head there Terry "Exeter will make a judgement tomorrow" If you think (and I agree) the pro's will wait for tomorrows runs to make a call, then surely we should be doing the same, and not writing any solution off just yet.

[beng]

So it's wrong? you'll have 10 post here with people now telling us to ignore the ECM, it doesn't handle this and that and of course "it struggles" with this and that. Better to admit its the best model you have and that at times like this with a lot of new variables the operational on all models will have inaccuracies. I take your point but wait for the ensembles and a couple more days. No straw clutching on computer programs you can't control.

It's the best medium range model for sure. It's not always the best at handling features in the closer range - the feature in question that is causing the problem is around t72-t96 - it's quite possible for ECM to mishandle that - which due to a massively complex and chaotic pattern (much more so than normal) results in a very different medium range output. We'll find out tomorrow either way.

[chris55]

Please note that just because a model has been better in its verification 6 days ago this has no influence of whether it will verify better in the next 6 days. So daily fluctuations in these stats mean didly squat. We are better looking at the verification rates over a longer period of time - and we all know which model comes out on top there - the ECM by a country mile!

Chinio I do agree over a broader more "normal" synoptic period this is the case, however since the major northern blocking has been showing up in the charts ECM does look to have struggled more than GFS UKMO.

It may mean nothing but worth mentioning. Is it the unusual synoptics ECM is having trouble with or is it just a blip regardless? Who knows.

[Zenarcher]

For anyone interested in the difference between the ECM's 00z and 12z run I've made up a image of the pressure system at 6am Friday,

The center of the low on the 00z ECM is very close to where both the 06z and 12z GFS placed it as well. Only time will tell who's right.

[bobbydog]

there are only so many ways you can say "its only one run" "the ABC always wobbles" "the XYZ is most reliable" "the A,B and C, will jump on board with the D" etc.... etc.... etc....

i think i'll come back later when everyone's got it out of their system..... maybe March!!

[The Northern Ramper]

At least countryfile forecast looked good, a bit of a wobble as the low moves in from the west, it gets close but is then pushed back west further into the atlantic as the cold block flexes it's muscles and begins to march towards the uk from northern scandinavia and this leads into a much colder weekend with snow showers to the northern and eastern side of the uk, especially bordering the north sea, indeed, showers from midweek in the east become more wintry in nature as max temps drop to 5 or 6c and with chilly nights. Even though things look tighter this evening and more problematic, on balance it still looks like cold from the north and east will ultimately win out.

I can't help but feel the countryfile forecast is a red herring and not taking the ECM into account due to the time the Ecm comes out just before the show.

[Gibby]

Good evening. Here is the report from the 12zs from the models of GFS, UKMO and ECM for tonight Sunday November 25th 2012.

All models show Low pressure near to SW England moving slowly Eastwards over Southern Britain over the coming 24-36 hours. By Tuesday it has moved offshore to the East of Britain with a colder and thankfully drier Northerly flow affecting the UK through midweek. At that point a small ridge and an equally weak trough sequentially cross East soon after midweek, the latter strengthening the Low pressure zone out to the East towards the end of the week. the week will start decidedly unsettled with more rain or heavy showers in the areas that least need it. From Tuesday on though the trend will be for drier conditions to slowly develop with some showers near Eastern coasts giving some snow over the hills of these areas. Further West a lot of dry weather will develop and with clearer skies by night frosts will become much more likely and with surfaces still very wet ice could become a major problem.

Late in the week GFS has Low pressure anchored in Scandinavia with a wrap around of cold air over the UK with coastal showers around the UK wintry on the hills. Still frosty nights inland in any clear skies given the light winds. Over the weekend sees wind turn more direct Northerly with colder uppers allowing wintry showers to pepper all Northern and Eastern coasts with snow possible to modest levels by this stage. Through FI tonight the cold pool continues to sit over the UK and to other areas of NW Europe too with wintry showers near windward coasts and inland at times as small disturbances move through. Settling snow would be unlikely to be too troublesome other than over the hills and in the North. Late in FI the pattern that emerges is one that could deliver more widespread snow in the SW as low pressure buffers up against the cold air sitting over the UK and NW Europe in a strengthening SE wind as High pressure remains strong over Greenland.

The GFS Ensembles shows the operational as a major cold outlier for much of the run while the more supportive pattern shows a rather cold period before less cold conditions are more likely with time. To balance the report there are also a few mild members taking uppers above +5C in London as early as the turn of the month so with such spread between the members things are very much unresolved in the details of where we go from the end of this week. Other than the operational and a few other members there is no suggestion of any major cold outbreak, as with unsettled weather so much in evidence later there would doubtless be milder air around too. Nevertheless there are also a lot of marginal uppers shown which if coincided with the right atmospherics at the surface could produce some snowfall for the lucky few.

The Jet Stream shows the ridging over the Atlantic breaking the flow down in the coming days with a weak arm travelling South to the West of the UK with a suave of strong jet current travelling NE over Southern Europe in a week or so.

UKMO for midday on Saturday shows Low pressure stretching from Germany to Italy with High pressure to the NW of Norway to Iceland and South through the Atlantic. The UK lies in an unstable NE flow promoting wintry showers, heavy at times in the Northeast. Towards the West and South conditions would of become rather drier with few if any showers and cold frosty nights compensated for by bright crisp days.

ECM shows the cold North flow collapsing away late in the week as the Atlantic ratchets up a few gears to the NW sending a ridge of High pressure East over the UK with frost by night to be followed by milder Westerly winds and rain East across the NW of the UK into the start of the following week. With Low pressure then established to the North of the UK towards the middle of next week a more conventional pattern of strong winds and rain mixed with brighter weather with showers, wintry on Northern hills would develop.

In Summary tonight there is a lot of uncertainty between the models on how things develop beyond this week. This week does look in agreement that a spell of rather cold conditions will develop with some showers in the North and East falling as snow on the hill, moors and mountains. Further South and West a lot of drier weather will develop from midweek with frosty nights under clearer skies. then things get much more complex with the GFS operational offering a very wintry spell though with very little support from its member colleagues. ECM on the other hand is keen to bring in the Atlantic after next weekend with a return to windy and unsettled conditions with rain at times, heaviest in the North. Which one is right is hard to call but ECM has been totally bullish in recent runs about bringing the Atlantic back into play quite quickly and with the GFS Ensembles showing a slow warming trend with more precipitation towards the long term mean beyond this week you wouldn't count against it happening. It's going to be a long and torturous week of model watching for cold and snow lovers this week. Good luck.

Don't forget if you want to read my summaries they are on my website up to an hour of them appearing here as I don't have access to my desktop at an earlier time.

[lorenzo]

A little something from 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.

[Iceberg]

ECM is the best global model IMHO, the ECM at this range is not normally wrong, the ECM twice in a row doubly so.

However and this is where we have the caveat, its like a game of poker and one of the few hands that beats a double ECM is a ens full house. If you plot the pressure as the high falls over at t144 the ECM has no support for its synoptic set up on any gfs ens. Nor does it have more than 10% on its on ECM 12z ens.

For this reason the Synoptics can be disregarded for now on the ECM 12.

However the trend should not be ignored and snow for next weekends now less likely than it looked to be

[The Eagle]

12z ECM ensembles roling out now if anyone's interested. Any straws to clutch?

http://meteociel.com/modeles/ecmwf.php?ech=72&mode=1&map=0&type=1

.

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

VARIOUS QUESTION MARKS IN THE NAM/GFS/CMC.

Code for "we don't have a clue" so we will just favor everything.

[lorenzo]

Code for they thought the ECM a little progressive.

[The Northern Ramper]

ECM is the best global model IMHO, the ECM at this range is not normally wrong, the ECM twice in a row doubly so.

However and this is where we have the caveat, its like a game of poker and one of the few hands that beats a double ECM is a ens full house. If you plot the pressure as the high falls over at t144 the ECM has no support for its synoptic set up on any gfs ens. Nor does it have more than 10% on its on ECM 12z ens.

For this reason the Synoptics can be disregarded for now on the ECM 12.

However the trend should not be ignored and snow for next weekends now less likely than it looked to be

I love the Poker reference, made me chuckle.

[Matty M]

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

Edited November 25, 2012 by Matty M

[Jonan92]

[LomondSnowstorm]

Fairly obvious which region the models are having difficulty with: