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chionomaniac

Model Output Discussion 13/11/13 >

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It might sound to many like blowing my own trumpet but you will never find I use terminology like 'warm sectors' in my analysis as I always reflect that the vast majority know nothing of such terms and just at the end of the day want to know what the hard facts of the weather are likely to be over their heads. If I used those terms on my website my inbox would be full of requests to explain what I meant. However, I do concede that many on here are very knowledgeable folk and it seems fine if terms are used when in discussion with other likely knowledgeable folk. Sorry for being off topic.

 

P.S. Thanks to Summer sun for posting my analysis across each night and morning. it saves me a lot of time.

 

Yes but are you not chiefly concerned with giving weather forecasts on your site rather than discussing the model output in a specific thread dedicated for such things in a weather discussion forum?

And if you explained what a warm sector was you would be educating people rather than confusing them would you not?

After all it has been discussed here and now people will know, that's the whole point of coming to forums such as this to discuss and learn. If people just want a dumbed down forecast they can go to any number of weather sites including the BBC.

I really don't think people here should be concerned about how such discussion would go down on an individuals web site. 

Edited by Mucka

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Looking at the ensembles this up and coming cold spell doesn't look too prolonged maybe a week max

 

From the 25th all ensembles agree on a steady rise to slightly above average for the 850's, it looks pretty dry over the next 2 weeks as well

 

Posted ImagePosted ImagePosted ImagePosted Image

 

So chilly this week before a steady rise back towards average or maybe slightly above average temperatures the closer we get to December

 

The 2 week temperature outlook shows a recovery in temperatures from the 25th, the south west and west wales could be back in double figures with temperatures between 10 and 15c here and between 5 and 10c else where

 

Posted Image

Edited by Summer Sun

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GFS 6z doesn't even end bad.

 

Posted Image

PV is still disrupted heights making it into the pole.

Yep and we know how accure the T+384hr is.  Really do not see any point in posting charts more than a fortnight hence, in fact the only thing guaranteed about the T+384hr is it's guaranteed to be totally different in 5hrs time.

 

As for the 06 GFS it maintains the general theme of steering Weds shortwave ever eastwards and then building a fairly robust looking cell of high pressure pretty much on top of the UK....these synoptics now look close to a given. So once it goes cold on Tuesday there's no sign of mild or even average temps, with some very chilly air likely to become trapped close to the surface later next week.  Thereafter though the waters become increasingly muddied, but what is again as clear as crystal is what folk want to see is dominatiing the overall debate in here.  Yes of course HLB remains a possibility as we close out the month, but it's a long way from being the favourite and a huge way from being a given imo, with a gradual return to zonality probably more likely than not at this stage as we move into official Winter.

Edited by shedhead

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I've taken a snapshot at T+96 hours from the GEFS 06z control run /  perturbations & mean...very interestingly there is a risk of heavy snow due to temps being close to or just below freezing with low pressure close to the east and the atlantic high held back further west, a nice ne/sw alignment and a tight squeeze in the isobars as the high pushes up against the trough, heavy snow and strong NNE'ly  to NE'ly winds..there is a good chance.

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Edited by Frosty.

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Bobbydog, i couldnt hav put it better. The long term trend following bext week may be a return to avg temps but the Atlantic is nowhere to be seen right now.

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Looking at the ensembles this up and coming cold spell doesn't look too prolonged maybe a week max

 

From the 25th all ensembles agree on a steady rise to slightly above average for the 850's, it looks pretty dry over the next 2 weeks as well

 

Posted ImagePosted ImagePosted ImagePosted Image

 

So chilly this week before a steady rise back towards average or maybe slightly above average temperatures the closer we get to December

 

The 2 week temperature outlook shows a recovery in temperatures from the 25th, the south west and west wales could be back in double figures with temperatures between 10 and 15c Posted Image  here and between 5 and 10c else where

 

Posted Image

Simplistic view on my part I admit but comparing these two ECM 00z op charts would it seem to suggest the ensembles prediction of a rise in temps as highlighted above by the 25th could be on the money?

 

In theory, how reliable are the ensembles?

Shades of yellow and orange seem to be drawing very much closer by the 27th for sure.

post-17830-0-17361600-1384692299_thumb.p

post-17830-0-35045400-1384692322_thumb.p

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Wow after all this time and its like a gfs love fest in here...Are people still using it .... Wheres the headbang smiley....The ECM is now back on board where the ensembles were last night and I fully expect it to continue-I have to laugh at the posters on here that keep saying its flattening / toppling & the atlantic is getting in- they have been saying it would happen after day 1, day 2 , day 3 , day 4, day 5 & even day 6- now were back to the mid term gfs ensembles again.Some days its utter chaos on here.

 

 

I don't know Steve, in a way you are being consistent, follow the model that shows the most amplified pattern (last night it was MetO) because you believe the block will win out but there has been no model consistency whatsoever so I can't put any faith in the latest ECM run just as you didn't put any in last nights. (and even the latest ECM though cold and showing promise still has a flattening of the pattern at the end - sure we can ignore that but would we if it were a Greenland high?)

 

The MetO forecast (if I am deciphering it correctly) is for a mid latitude block just to the north of the UK to slowly be weakened from the NW and that seems to be pretty much what the output is going for.

 

Are you saying you think all the models are sending too much energy NE and that you are expecting some form of HLB to set up or are you saying that you don't know other than mid latitude blocking will continue to offer possibilities as long as it is around?

 

 

Thanks

Edited by Mucka

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Simplistic view on my part I admit but comparing these two ECM 00z op charts would it seem to suggest the ensembles prediction of a rise in temps as highlighted above by the 25th could be on the money?

 

In theory, how reliable are the ensembles?

Shades of yellow and orange seem to be drawing very much closer by the 27th for sure.

 

While it's looking more likely our weather will be more high pressure dominated, that doesn't necessarily mean a rise in temps is inevitable; an anti-cyclonic set up drawing in cold air off the continent is still the form horse in my book for at least the next week or so.

 

Here is the upper profile for the second chart you quoted:

 

Posted Image

Pretty chilly, with plenty of cold pooling starting to build up in eastern europe!  If the HP cell remains in play and holds off the atlantic (this is all way into FI, there's no real way of telling what will happen in this regard yet), we're well placed to tap in to that air somewhere down the line.

 

Edit: The main concern I have though is how that PV lobe off greenland interacts with the ridge...It could simply flatten our block, but it's simply a case of wait and see for now.

Edited by weatherguy

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Ukmo frosty its ok pretty much the same as last night give or take its slight SE correction - the reason it doesnt look as good as yesterday on meteociel is the heights to our S & E are not quite as low as yesterday but essentially uts the sameAt144 the greenland trough has a slight positive tilt which is not so good- 

 

Yep but at t120 it looks as though at least some of the energy ought to be going south of the block - by t144 it seems to push a lot more north.  I just think it's the bias in the model - underestimating the trough disruption that should occur.  With ECM we've been seeing this almost everyday at t168 energy going south, then at t192 - it's all going north.

 

GFS doesn't bear comment - other than it agrees with UKMO and ECM and t72 now - which is something.  

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The latest update from the 6z gfs ens project a neutral/weak positive NAO. Just a couple of days ago, the forecast was for a weak negative. Changes afoot!

Posted Image

conversely, the ECM disagrees

Posted Image

ECM ens 0z NAO outlook.

Edited by draztik

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The latest update from the 6z gfs ens project a neutral/weak positive NAO. Just a couple of days ago, the forecast was for a weak negative. Changes afoot!

Posted Image

conversely, the ECM disagrees

Posted Image

ECM ens 0z NAO outlook.

these graphs are just derived from the model output though and are just reflective of the latest model run so if the model run has the wrong pattern, these graphs will be wrong. GFS graphs would show a completely different AO/NAO graph this evening if the 12z run is different to 6z. I may be wrong so someone correct me if I am.

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these graphs are just derived from the model output though and are just reflective of the latest model run so if the model run has the wrong pattern, these graphs will be wrong. GFS graphs would show a completely different AO/NAO graph this evening if the 12z run is different to 6z. I may be wrong so someone correct me if I am.

You'd be correct, the forecast is based on the data from each run of the model, and that of course is subject to change. Like any model, we look for trends, and the trend from GEFS was for a negative NAO if you averaged the 4 run, consistently just a couple/ few days ago. Now there are fluctuations, run to run.The ECM ens have been forecasting a negative NAO for some days now, and the fluctuations aren't as pronounced compared with GEFS. Still, its of interest, that the consistency of a negative NAO has been lost from the gfs ens, meaning they cant get a handle of what is to come. Be their stats correct or not, we should take onboard what they are currently showing

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UKMO remains stuck back to last Thursday for t6 to t36 so once runs get below this timeframe we won't be able to see them on UKMO as it stands

 

t42 to t144 is fine

 

As well as UKMO's issue with not updating the GFS ensembles are stuck at the 12z update from yesterday

Edited by Summer Sun

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Excellent post Steve. I will concur he doesn't just favour cold and has often been right when 90% of the models are going against his predictions. Not to say he calls it right every time but for those who haven't been around long its always worth taking into account Steve's view.

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Great post from Steve.  It is always a breath of fresh air when people don't treat the models as gospel, and it is surely entirely sensible that people (rather than algorithms) evaluate the strengths and weaknesses of the models?

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Hi Mucka- certainly a response worth a reply.

 

Snip.....

 

 

cheers

S

Wow what a fantastic post.. probably the best explained and informative post ive seen on this site...

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Steve's post is excellent and it's great he's taken the time to explain his rationale.

 

At the end of the day he's doing what all weather forecasters do I assume, and that is to read the models and then apply the human touch to firm matters up in ones own mind and then produce a forecast.

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12z GFS coming up, I expect a far better run than the dreadful 06z. It has to start taking this vortex split into account. I expect to see a much slower west-to-east movement of the Atlantic lows (vortex over that area actually moves east-to-west on the stratospheric charts) and subsequently a much better opportunity for the nearby high pressure to build North. A zonal pattern in the next couple of weeks just wouldn't fit with any of the background signals. The increasingly likely pattern is some form of blocking in the high latitudes, that's not to say the UK will get a cold spell though and it's pointless to look for something as specific as affecting our tiny island. The Northern Hemispheric pattern as whole though should become more blocked in 7-10 days time.

Edited by Snowy L

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12Z GME

 

Posted Image

Posted Image

Well I might pick up a snow shower or two tuesday afternoon here before the wind swings westerly prior to the incoming low from the north. Probably the only real chance at low levels unless the cold behind Wednesdays low upgrades over the coming runs.

One thing I do wonder about is whether the models will upgrade that low, the GFS has upped the ante over the runs today, lets see whether it continues.

Wednesday looks like a pretty awful day

Posted Image

Heavy rain and strong to potentially gale force North/North westerly winds.

Edited by Captain shortwave

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anyway I hope this helps you & a few others who might not understand my rationale.... its not all make believe people- its sound thinking......

 

 

cheers

S

 

 

hi Steve, i have to admit being sceptical of your reasoning in the past but credit where its due. an excellent explanation of your methods. thanks for taking the time to do so and maybe shutting up some of the doubters like myself.

 

i may have slipped in the occasional snipe at you in the past and i apologise for having done so

 

regards,

Rob

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