Model Output Discussion 18th Nov.2013-12z onwards.

[Frosty.]

The Ecm 00z op run has some support from the GEFS 00z perturbations...these being my cherry pick

[bluearmy]

the 50 ecm ens running at 50km resolution should be a much better verification than the op. however, there are certain scenarios where the 16km res of the op will make all the difference. often that means the op over amplifies the pattern as it makes more of features than actually happens. i wonder if this complex scenario will be one of those times when the ecm op has its momemt. i will keep my powder dry till after the 12z suites.

[Captain Shortwave]

GFS offering a slightly different solution, it slows the shortwave down, perhaps a movement to the ECM where the shotwave never goes over the top of the high perhaps???

Either way the GFS brings cold air into the UK briefly at day 7, cold enough for snow in Scotland probably before the shortwave develops and moves through Scotland, northerly at day 9 most likely

Edit - There we go

Edited November 28, 2013 by Captain shortwave

[Nick F]

Not much comment on the latest GFS, must be a downgrade.

 

can't see any 'downgrade' so far, northerly kicks in around t+216, trigger low deeper as runs across the UK though,

[radiohead]

Blizzard conditions in Scotland if this came off.

 

[Ali1977]

It looks like a downgrade in FI, uppers are not as cold or widespread in Western Europe, inc us.

[tight isobar]

I'm personaly liking evolve in 6z suite..think the 12 z may just have some wetting there good selves...!!!

[SMU]

Well not 'bad' from the 06z-

 

so extracting the bias of underestimating northern blocking & to much Northern energy that's a pretty good run.

 

People who are gazing their eyes at the GIN corridor theres no need to worry- why?

 

* its not the OLD days of pre 2009 where lows would explode there & flatten the patten

* Any system in that area around 168-192 us going to get crushed- a RARE High pressure over the states- just west of a DEEP - PNA pattern aligned to a ridging atlantic high will slow these systems down & destroy them -

 

No shortwave shockers expected to stop the blocking.

S

the 50 ecm ens running at 50km resolution should be a much better verification than the op. however, there are certain scenarios where the 16km res of the op will make all the difference. often that means the op over amplifies the pattern as it makes more of features than actually happens. i wonder if this complex scenario will be one of those times when the ecm op has its momemt. i will keep my powder dry till after the 12z suites.

 

Its highly unlikely the resolution of the ensembles is better than the operational- you may want to check that.

[Cecil Hogmanay Melchett]

I think many would be pleased if gfs06z came off,bitter arctic northerly with snow potential and a very cold high meaning snowcover maintained for a good 2 or 3 days.

In the run up to christmas it will certainly be very seasonal for most and a damn site better than wind and rain and temps in double figures.

[Steve C]

Hi SB- id imagine with such a deep northerly & with 500MB temps sub -45chttp://www.wetterzentrale.de/pics/Rtavn2161.png The conditions will be ripe for polar low development- or at very least a couple of decent troughs. Just referring to my post above- forecasting via the way I do it will always have the odd miss, no-one will ever be spot on, however long term refining & more examples of the model nuances will only improve my accuracy, where as reporting what the models show will only be as good as that models resolution & bias at that point-S

And let's hope there are pretty decent scientists and computer programmers constantly working on the same models, correcting the nuances and improving the model output too...

[forecaster]

Taking it to the next level in terms of forecasting - is taking the models & removing their bias & nuances to actually generate a forecast which will often deviate to what the model shows.

 

 

Yes, but then you have to be aware of human biases. 

 

Regarding the EC Ensemble Mean this morning, notice that it was too flat with the northerly for this upcoming weekend at the 216hr range:

 

 

 

 

In the end, for this upcoming weekend, at the 216hr range the EC det looks like it caught on better than the EC Ens mean.

Its highly unlikely the resolution of the ensembles is better than the operational- you may want to check that.

 

It doesn't look like bluearmy actually said that?

[snowice]

So we have heard it from Ian ferguson that the cold spell shouldn't last too long. So I would now go along with a 3/4 day toppler before we see us back to something akin to what we have now.

 

Well as Steve Murr  said this weeks westerly never materialised ,so as good as Ian is nobody can

call it this far out.You have to look at trends and what the models are showing and i dont think

anybody knows how long the cold spell will last from this range. 

[BornFromTheVoid]

We've see an upper ridge gradually push north from the end of October/early November, bringing mild conditions at first and gradually more settled and cooler conditions during the month.

Below is the 500hPa geopotential height anomalies in 7 day averages, and shows the progression of the upper ridge which is currently dominating our weather.

 

Now that the ridge has reached out to our west and toward southern Greenland, I think this may become a strong feature of the next few weeks, with repeated ridging toward Greenland and the potential of opening the northerly floodgates.

Indeed, the ECM shows the ridge never moving too far from it's mid Atlantic/southern Greenland position, right out to the end of the run

 

t0 ............................................. ................................ t72

 

t144 ........................ .................... ........................ t216

 

The 8-10 day mean height comparison shows the situation well, with the GFS not too dissimilar to the ECM

 

The CFS has reaffirmed it's prediction of moderate blocking to our north in December, too, which further backs up the cold spell potential. (explanation for the chart below is here http://forum.netweather.tv/topic/77743-winter-20132014-forecastshopesdiscussion-thread/page-117#entry2806211)

 

 

 

Let the individual runs do what they will do, and keep an eye on the broader picture. As long as we maintain the ridge nearby, but especially close to Greenland (and the polar vortex remains away from Greenland) the potential for northerlies remains strong imo.

 

[Captain Shortwave]

Good news is the GFS yet again produces the northerly, most important bit.

The GFS is starting to smell that block to the north east of the UK, but snatches defeat from the jaws of victory, but that's really not a surprise.

As long as the GFS/ECM keep producing that deep Euro trough and corresponding northerly then the ensembles should slowly move into line. Then we can start to think of bigger and better things. Promising signs though.

[BLAST FROM THE PAST]

Its FI but at t216 to t240 a howling N to NE'ly with -10 uppers covering whole of Scotland and the whole of northern England, the eastern side of England down to and including eastern Home Counties.....yep some downgrade. 

 

A mere NW'ly with -5 uppers at best is a downgrade otherwise its just hair splitting? .

 

 

 

BFTP

[forecaster]

Looking at an EC ensemble 850hPa temperature plume, both the control and deterministic are serious cold outliers within the ensemble. The control (32km) and det (16km) track near together. I'm no modeller, but that would suggest to me that the differences between the EC ens mean and det are perhaps more down to sensitivity to initial conditions and less to do with modelling resolution of the individual members.  

[SMU]

Yes, but then you have to be aware of human biases. 

 

Regarding the EC Ensemble Mean this morning, notice that it was too flat with the northerly for this upcoming weekend at the 216hr ra 

 

It doesn't look like bluearmy actually said that?

 

BA is implying that the ECM ENS have a higher vertical resolution than the operational- 50KM V 16km- I doubt that.

 

Im sure the ECM op has been upgraded to 90KM Vertical- but I may be wrong.- whatever though it should be more than than the ENS

 

nice spot for this weekends northerly- V the MEAN also highlights there poor resolution on the shortwave pattern.

[Ian Brown]

Well not 'bad' from the 06z-

 

so extracting the bias of underestimating northern blocking & to much Northern energy that's a pretty good run.

 

People who are gazing their eyes at the GIN corridor theres no need to worry- why?

 

* its not the OLD days of pre 2009 where lows would explode there & flatten the patten

* Any system in that area around 168-192 us going to get crushed- a RARE High pressure over the states- just west of a DEEP - PNA pattern aligned to a ridging atlantic high will slow these systems down & destroy them -

 

No shortwave shockers expected to stop the blocking.

S

 

Its highly unlikely the resolution of the ensembles is better than the operational- you may want to check that.

 

To say that we should not be worrying about the GIN (corridor of death) area is unbelievable Steve, pre-2009 or not, cyclogenesis in this area is the well established quick fire route to end a Northerly. The most important thing to remember here is that shortwaves developing at the Eastern end of the jet streak will not be picked up until this is around T120 on the NWP.

The GFS has a better formation of pressure rise in the first place than the ECM, and there will be changes to come from both models as this comes into the higher resolution but remember when LP has broken the link between HP in the Atlantic and Greenland OR when lower heights have crossed the Greenland plateau, it’s game over for our Northerlies.

[Frosty.]

Interestingly, the Gfs 06z op run.... even before the Arctic blast hits the uk, the days leading up to it don't look very mild do they

[Nick L]

Not much comment on the latest GFS, must be a downgrade.

 

Can I just point out (I'm not specifically aiming this at you) that posts like these add nothing to the discussion. That also goes for posts along the lines of "next run out soon, eyes down" etc.

[Barry12]

The weather will do what it wants, the models do not know what will happen yet, so don't worry about a thing!

 

[shedhead]

'Be wary' of projected N'erlies at 120hrs, 'be very wary' of projected N'erlies at 168hrs, but beyond 192hrs 'be exceptionally wary' of projected N'erlies doesn't even come close.

[UV-RAY]

To say that we should not be worrying about the GIN (corridor of death) area is unbelievable Steve, pre-2009 or not, cyclogenesis in this area is the well established quick fire route to end a Northerly. The most important thing to remember here is that shortwaves developing at the Eastern end of the jet streak will not be picked up until this is around T120 on the NWP.

The GFS has a better formation of pressure rise in the first place than the ECM, and there will be changes to come from both models as this comes into the higher resolution but remember when LP has broken the link between HP in the Atlantic and Greenland OR when lower heights have crossed the Greenland plateau, it’s game over for our Northerlies.

I have to agree with Ian here as this isn't about pre 2009 as one can view the archives and find similar patterns which failed to materialise  back in 60s, 70s and 80s due to cyclogenesis  in the corridor of death. Fascinating model watching all the same and as enjoyable as ever reading Steve's reasonings.

[gottolovethisweather]

Not much comment on the latest GFS, must be a downgrade.

 

I too   came on here expecting to see a few charts and some analysis and wondered whether this was the "who's my favourite weather forum celebrity" discussion thread.   Let's have some further discussion around the outputs of the models, not around the people producing the inputs.  Or else, "get me out of here",   before I go mad.

 

It's like a personality ping-pong in here at times.

 

Please respect all members, no matter how extreme their views may seem to be.

 

Many Thanks extended to those folk whom have provided something to be glossed over, as I was preparing my post, you know who you are.

Edited November 28, 2013 by gottolovethisweather

[johnholmes]

We've see an upper ridge gradually push north from the end of October/early November, bringing mild conditions at first and gradually more settled and cooler conditions during the month.

Below is the 500hPa geopotential height anomalies in 7 day averages, and shows the progression of the upper ridge which is currently dominating our weather.

 

 

Now that the ridge has reached out to our west and toward southern Greenland, I think this may become a strong feature of the next few weeks, with repeated ridging toward Greenland and the potential of opening the northerly floodgates.

Indeed, the ECM shows the ridge never moving too far from it's mid Atlantic/southern Greenland position, right out to the end of the run

 

 

 

 

The 8-10 day mean height comparison shows the situation well, with the GFS not too dissimilar to the ECM

 

 

The CFS has reaffirmed it's prediction of moderate blocking to our north in December, too, which further backs up the cold spell potential. (explanation for the chart below is here http://forum.netweather.tv/topic/77743-winter-20132014-forecastshopesdiscussion-thread/page-117#entry2806211)

 

 

 

 

Let the individual runs do what they will do, and keep an eye on the broader picture. As long as we maintain the ridge nearby, but especially close to Greenland (and the polar vortex remains away from Greenland) the potential for northerlies remains strong imo.

 

I am quite intrigued by this use of data and comparisons and what the actual may show so you can do a real comparison. it is probably unlikely but you never know it may show some promise as something to use for longer term(1-2 months ahead) forecasting. Well worth trying in my view-thanks