Model Output Discussion 23/11/2012 18Z onwards

[bluearmy]

Re the 06z gfs suite. Imo it gets the ne greenland/svaalbard heights relationship wrong quite early. The rest is bound to be wrong. Watch the early frames of ukmo and gfs 12z by all means but i am not concerned

[Jason T]

Cheer up folks everything will be just fine by the 12z.

The names Bom... James Bom.

Fergie just tweeted sounds good to me. fergieweather @ UKMO go for cold & blocked into at least 10-15d based on MOGREPS-15 & EC Monthly. They say the 'wobbles' typical in this scenario

18 minutes ago

[lorenzo]

Here are some charts from the model bias page http://www.hpc.ncep.noaa.gov/mdlbias/index.html

Great toy for checking out the variations.

Here are some images using the last 10 runs of the 12z. At 72 hrs and also 144 hrs for the UKMO ECM and GFS.

UKMO / ECM / GFS - 72 hours

UKMO / ECM / GFS - 144 hours

Will leave the dissection to our experts each has it's own little trend. I prefer the ECM overall but that's just me !

[johnholmes]

gawd-too heavy for me L-Steve, phil, Chio perhaps, anyone else?

[Frosty.]

Frosty I don't mean it in a negative way just a general comment for people hoping the 6z was a massive outlier, as I've said I still think we'll get a decent cold spell but think people saying 'bin' it ect is daft because you have to consider every run even if you don't like what it shows. Let's just hope the UKMO is right

Hi Weathizard, it's no problem

Yes lets hope so, the ukmo is excellent for cold prospects, as is the gefs 0z mean, I think we are still firmly on track for a good cold spell with frost, freezing fog and some areas will get snow.

[BorrisB77]

If you follow Joe B astardi on Twitter, in the last 3hrs he has tweeted map of snow/ cold wave for UK and NW Europe within the next 8 days..so it certainly looks like he is singing from the cold hymn book aswell..as for the models like many have said before let's all be patient and enjoy the ride..

[Frosty.]

gawd-too heavy for me L-Steve, phil, Chio perhaps, anyone else?

Bend your knees when you pick it up john, don't strain your back

Latest models look good for a wintry early winter.

Edited November 24, 2012 by Frosty039

[J10]

I have done the latest Alpine forecast, but with some charts outlining the potential outcomes for next week.

Link

[Glacier Point]

The paradox of weather forums much in evidence. When the pattern becomes problematic for NWP, and inter and intra run consistency falls apart, people seem more inclined to buy into operationals rather than less so!

Stick with your ensemble means.

Pretty much a solid trend still there for a substantively and sustained below average period. The models still trying to resolve mean position and residual energy left in the Canadian sector vortex after the split. An interesting little trend within a trend, shift in the block position around Svalbard and AO becoming more negative in time. I can only assume those commentaries on ensembles are being viewed from a Euro-centric view. If there was an issue, would have expected means to become diluted, but not any sign of this.

[nick sussex]

I think we're seeing the lack of observational data re the Arctic high come into play here.

And because the development of shortwaves has a huge effect on how that high ridges south I'd advise people to not look past 96hrs in terms of detail.

If you're going to take one positive from the output its that nearly everything that can go wrong in terms of shortwaves still doesn't stop the majority of models from finding a colder solution.It might not be the deep cold at the moment but still time for this to appear in the outputs.

I'd also view the eastwards progression of energy into Greenland by the ECM operational as an unlikely scenario given comments by NOAA:

A REPETITION OF THE PATTERN SEEN OVER THE PAST FEW WEEKS IS

EXPECTED, WITH AN AMPLIFIED TROUGH MOVING SLOWLY THROUGH THE

EASTERN PACIFIC, WITH DOWNSTREAM RIDGING FORMING ACROSS THE WEST

AND PLAINS, AND RENEWED TROUGHING ANTICIPATED ACROSS THE NORTHEAST

WHICH IS EXPECTED TO CLOSE OFF INTO A DEEP CYCLONE AS IT MOVES

INTO QUEBEC AND ATLANTIC CANADA

Compare the ECM at 144hrs:

To the UKMO for the same time:

You can see here the ECM takes the energy east and not ne this has a big impact on the pattern in Europe.

The ECM operationals have been performing poorly upstream for quite a few days now and so for the moment you have to side with other guidance.

THE 00Z ECMWF IS QUICK WITH A SHORTWAVE MOVING THROUGH THE

EAST/WESTERN ATLANTIC EARLY IN THE PERIOD AND OUTPACES THE

REMAINDER OF THE GUIDANCE LATE IN THE PERIOD NEAR THE WEST COAST,

INCLUDING ITS OWN 12Z ENSEMBLE MEAN. ALOFT, THE NON-ECMWF

GUIDANCE FITS THE 12Z ECMWF ENSEMBLE MEAN BEST ACROSS EASTERN

CANADA FROM THURSDAY ONWARD (AND PLAYS INTO THE SLOWING/WESTWARD

SHIFT SEEN IN THE OPERATIONAL ECMWF NEAR THE EAST COAST OVER ITS

PAST COUPLE DAYS OF RUNS), THOUGH THE ECMWF ENSEMBLE MEAN SURFACE

LOW NEVER COUPLES WITH ITS 500 HPA CIRCULATION (WHICH SEEMS

UNLIKELY), SHOWING MINIMAL INTERNAL CONSISTENCY. BASED ON THE

ABOVE, THE PRESSURES WERE BASED ON A 40/30/30 BLEND OF THE 00Z

UKMET/00Z GFS/00Z CANADIAN THROUGH FRIDAY BEFORE SWITCHING TO A

50/50 BLEND OF THE 00Z GFS/00Z GEFS MEAN SOLUTION THEREAFTER.

WHILE THIS MAINTAINED GOOD CONTINUITY NEAR THE WEST COAST, IT LED

TO A MORE COASTAL CYCLONE TRACK LATE TUESDAY AND WEDNESDAY WHEN

COMPARED TO FRIDAY AFTERNOON'S PROGS AND A GREATER SNOW THREAT FOR

THE NORTHEAST.

Edited November 24, 2012 by nick sussex

[lorenzo]

Nick have you got a link for these aviation updates from NOAA?

[pyrotech]

Can also pass on a tweet that Ian Fergusson has just made regarding the models

This is what meto are looking at model wise and what they are thinking at the moment, regarding each model and the rollercoaster ride we have watching them

UKMO go for cold & blocked into at least 10-15d based on MOGREPS-15 & EC Monthly. They say the 'wobbles' typical in this scenario

[Mark Bayley]

Thought i would copy some of my post from the strat thread seen as though its relevant to this thread as well

Edit: corrected zonal mean chart

Another good set of charts today with a continued forecast decrease in zonal mean winds

Current: http://wekuw.met.fu-...2&var=u&lng=eng

While stratospheric temperatures, at the 30hpa level, continue to rise

Current: http://wekuw.met.fu-...2&var=t&lng=eng

Looking at the geopotential height charts we see a split in the vortex by day 10 at the 100hpa

With sighs of splitting right up to the 10hpa level

This to me would suggest, as others have pointed out, a period of blocking lasting well into December. I see no organised and strong polar vortex. Despite the models chopping and changing on whether the coldest air will get us, i would suggest at some point, over the next few weeks, that there is a high chance it would. Other teleconnective factors, such as the MJO, support this.

UKMO predicts an eventual move to phase eight

GFS predicts an eventual move to phase one

The NAEFS also keeps blocking through its run, albeit to me more of a west based -NAO. Although i would have thought based on the stratospheric output and MJO that this would be further east.

The above would cast suspicion any long term charts suggesting the reorganisation of the PV, and removal of blocking around Greenland (i.e. the long term GFS). I think, as others have alluded to, that it is a safe bet to expect some sort of blocked pattern well into December.

In the more immediate term we have strong winds and heavy rain to look forward to, the rainfall charts look particularly concerning for those already experiencing flooding.

Edited November 24, 2012 by Mark Bayley

[Methuselah]

Looks like I will have to forget about this then;

http://cdn.nwstatic....300/h500slp.png

Judging from the shape of that, there's most-likely a 'glitch' in there somewhere?

[syed2878]

a qs guys isn't it only rite to compaire the runs with runs? E.g 0z to 0z, 6z to 6z and 12z to 12z. I would of thot this way would give a better idea or have i got that wrong.

[TAFKAP]

The paradox of weather forums much in evidence. When the pattern becomes problematic for NWP, and inter and intra run consistency falls apart, people seem more inclined to buy into operationals rather than less so!

Stick with your ensemble means.

Pretty much a solid trend still there for a substantively and sustained below average period. The models still trying to resolve mean position and residual energy left in the Canadian sector vortex after the split. An interesting little trend within a trend, shift in the block position around Svalbard and AO becoming more negative in time. I can only assume those commentaries on ensembles are being viewed from a Euro-centric view. If there was an issue, would have expected means to become diluted, but not any sign of this.

GP the voice of experience and reason once again. I always sit up and pay attention when the big man makes his thoughts known. Lessons to be learned here for the headless chicken panic that seems to accompany even the most promising of model runs.

[Frosty.]

For anyone concerned about poor ensembles etc, take a look at the latest meto update..it's taken the cold outlook to a higher level now with more mention of wintry heavy showers arriving later next week and then more so during the following week with widespread frosts, drier in western areas but cold everywhere by the start of december, all this ties in with the latest GEFS mean and some other excellent modelling, there will and always have been model wobbles, especially with individual op runs, but these problems tend to get ironed out as the cold spell looms large.

Edited November 24, 2012 by Frosty039

[January Snowstorm]

We have seen time and time again over what must be 10 years or more now where a trend is picked up by the models and an Easterly fails to materialise. In particular Easterly's have proven time and time again to fail to occur when modelled in FI.

Now this is likely different because the background signals overwhemingly support height rises to our North.

However, the following is a very plausible outcome and is more or less what the 06z suggests:

1) the cold spell gets delayed as shortwaves are now being picked up. Friday was meant to be the heart of the cold spell, now it looks more like the starter day

2)the cold spell doesn't happen as height rises are in the wrong place and the UK doesn't benefit before the atlantic kicks off again (albeit most likely short term anyway)

Now folks to deem the operational run of the gfs and ecm as being a waste of time is a tad unreasonable

Yes let's stick to the ensembles but even they are clearly backing down on where they were 3days ago.

So as I said earlier let's wait and see what the 12's throw up and see does the picture become clearer then

But please let's not rubbish either view because there is plenty on both camps here at the moment to claim victory

By both camps I mean the coldies and those who like to take each run as very important ( as I dont think mildies actually exist on here)

[london-snow]

Afternoon Folks.

Just a quick question with a idea floating around my head -

Is the gfs and ecm struggling with the pattern because its a unusual pattern and also because it is using more of a wider range of data than the ukmo?

UKMO - Goes up to 144h.

ECM & GFS goes further and into fi.

Just a thought.

[Frosty.]

GP the voice of experience and reason once again. I always sit up and pay attention when the big man makes his thoughts known. Lessons to be learned here for the headless chicken panic that seems to accompany even the most promising of model runs.

That's a tad unfair, there are a lot of sensible posters on here apart from the oracle that is GP

I now think the upcoming cold spell will last at least 15 days before it comes under any atlantic threat but even then, with such amazing blocking to the northeast, north and northwest, any mild attack may result in a blizzard with the cold air beating the mild air back with a big icy stick.

Edited November 24, 2012 by Frosty039

[Alan Medlock Valley]

As Steve Murr and I think a few others have said the GFS has a mild Atlantic bias to it - it ALWAYS struggles with the idea of bringing in the cold from the east or north east.

[TAFKAP]

That's a tad unfair, there are a lot of sensible posters on here apart from the oracle that is GP

I now think the upcoming cold spell will last at least 15 days before it comes under any atlantic threat but even then, with such amazing blocking to the northeast, north and northwest, any mild attack may result in a blizzard with the cold air beating the mild air back with a big icy stick.

I wasn't disparaging anyone, just that I really respect GP, there are so many other members I respect and appreciate too, for example Chionomaniac whose technical knowledge is astounding and yourself (shameless flattery intended lol). Many others I haven't named here, but my comment re: some posts reverting to mindless panic and flapping still stands. I'm with you and I think this winter will be EPIC.

[Wadey]

That's a tad unfair, there are a lot of sensible posters on here apart from the oracle that is GP

I now think the upcoming cold spell will last at least 15 days before it comes under any atlantic threat but even then, with such amazing blocking to the northeast, north and northwest, any mild attack may result in a blizzard with the cold air beating the mild air back with a big icy stick.

sounds good too me got my snow socks for the car on order

[VillagePlank]

GEFS 850hPa Ensemble Analysis,

[LomondSnowstorm]

We have seen time and time again over what must be 10 years or more now where a trend is picked up by the models and an Easterly fails to materialise. In particular Easterly's have proven time and time again to fail to occur when modelled in FI.

Now this is likely different because the background signals overwhemingly support height rises to our North.

However, the following is a very plausible outcome and is more or less what the 06z suggests:

1) the cold spell gets delayed as shortwaves are now being picked up. Friday was meant to be the heart of the cold spell, now it looks more like the starter day

2)the cold spell doesn't happen as height rises are in the wrong place and the UK doesn't benefit before the atlantic kicks off again (albeit most likely short term anyway)

Now folks to deem the operational run of the gfs and ecm as being a waste of time is a tad unreasonable

Yes let's stick to the ensembles but even they are clearly backing down on where they were 3days ago.

So as I said earlier let's wait and see what the 12's throw up and see does the picture become clearer then

But please let's not rubbish either view because there is plenty on both camps here at the moment to claim victory

By both camps I mean the coldies and those who like to take each run as very important ( as I dont think mildies actually exist on here)

They're not completely useless, I don't think anyone is arguing that, it's simply the case that, when there's a large degree of disagreement between the models, the ensemble guidance should have a far greater weighting than the operational runs. The GEFS has, I'll grant you, shifted around a bit but the ECM ensembles and the NAEFS have been rock solid and we should be very sceptical of any model which is not inline with this guidance. That does of course allow for variations over the details of shortwave placement etc. and as the difference between the UKMO and the ECM shows there is a lot of scope for variation even within those parameters but I would urge anyone to be wary of taking any operational output as gospel ever, and especially not at the present moment.

People can choose to live and die by the latest GFS if they wish to, and I like to comment on how the latest run looks as much as the next guy, but without actually looking at the bigger picture they won't get a fair representation of what's actually likely to happen.