Model Output Discussion 12z 18/10/2012

[johnholmes]

oh dear my attempt to suggest a man/machine mix is better than simply taking a computer model output is leading to a rash of unexpected comments!

No it does not mean there are good and bad forecasters, some are more talented and perceptive than others is how I would describe it.

Fax charts are the Met O method of, taking all the model outputs at (the time we are talking of is T+120 but for any time), using the forecasters experience and professional training, then portray that in a way (which the British public had grown accustomed to before the dumbing down for a number of years) that showed where the lows and highs were expected to be along with the frontal systems. Superimposed on there, for more professional folk, are the 1000-500mb thickness lines. I'm not sure why they are still kept on there as the 'old' method of gridding and degridding surface and 500mb charts to arrive at the thickness chart which gave a good idea 24 hours ahead of the path the lows might take and just where the active fronts would lie is less in vogue now. One could just as easily draw areas of vorticity although that is a more complex thing to get on a Fax type of chart.

best I shut up before I bore everyone to sleep.

[legritter]

The T+120 Fax could be interesting as it will give a good idea, man/machine mix, better than any model on its own, just where Exeter feel the main thrust of cold air is going.

I suspect that the T+120 from last night could be a bit different tonight and probably not in favour of the cold lovers but not long to wait before it is issued. Copy the current one and see how they compare?

As i,v always said the fax charts are always the interesting charts of the day .in a complete amateur position i have on many occasions back in the 70s and 80s watched professional meteorologists present and prepare these hand drawn works of art .i can remember being present when the charts for the third week of FEB 1978 were being discussed and drawn ,if you look at very old synoptic charts in a run ,you can try and see what happened then look at forecast summary for that day then compare ,another mouth watering day what will pop up tomorrow, cheers all .

[weatherobsuk]

Hard to believe that on Stanage Edge today it was close to 15'c and yet in a weeks time we're talking sub-zero northerlies and chances of snow. Any trend with the ECM, UKMO models as to the westerly encroachment of the cold-pooling. I keep seeing the trend going ever more to the west by each day and if a nice Scandi-High builds then Easterlies could become the predominant flow once more as seen in yesteryears.

[Tim Bland]

It has to be Said more often than not the fax is a replica of the ukmo. So much so I often wonder why they bother redrawing the output

[Frosty.]

Booooo

I think if the arctic air digs in, nowhere in the uk will be immune from wintry precipitation but for northern hills and the scottish mountains, it could be looking like a christmas card scene by the weekend if the ukmo, ecm, gem op runs were to verify, what a stunning early start for the scottish skiing industry it will be if the models don't downgrade by tomorrow 00z.

[Zenarcher]

Here are the snowfall charts from todays 12z ECM,

Around 130 hours nothing much just a bit over Northern Scotland,

168 hours still some snow over Northern Scotland but a good amount over SE Ireland,

Finally at 180 hours the furthest these charts go out to it shows widespread snowfall over Scotland and bits of snow over Ireland and Southern England,

Very far ahead though but thought I'd share them

Edited October 21, 2012 by weathermaster

[nick sussex]

I think people have to be realistic regarding snow in late October.

Although there was a more recent event a few years back its very much the exception.

Theres not even solid agreement on that cold plunge with the GFS pushing the main cold thrust to the east, although the rest of the models do indicate some much colder conditions let's see if the GFS comes on board and then re-evaluate the snow potential then.

An outsider shot for some more interest would be a disturbance running se into the UK after the initial northerly.

[Liam J]

Colder air shunted further eastwards again on the 18z, two successive runs now - this can't be discounted, will the other models follow suit on the 00z runs?!

Edited October 21, 2012 by Liam J

[SnowObsessor90]

Oh dear, if anything the 18z looks like yet another downgrade, it'll be very interesting to see what the upcoming 00z runs bring, I

Edit: Hold on, could a reload be on the cards I wonder?

Edited October 21, 2012 by Anonymous21

[Cheese Rice]

Looking at the various outputs I would favor the ECM/UKMO for the Northerly as they are broadly similar in relation to the trough displacement and the position of the high over the North Atlantic.

Regarding snowfall in October one should factor the cooler, perhaps significantly cooler than normal sea surface temperatures over NW Europe. Surely this will have an adverse effect on daily temperatures, suppressing them significantly under a cooler air stream, aiding any snowfall potential. Of course there are many other factors. For any real tangible snow chances we need a secondary trough to feed down from the north as the 850's will essentially mix out at lower levels, curving chances of wintry precipitation away from high ground in Northern Scotland.

Edited October 21, 2012 by Cheese Rice

[SMU]

Weather master can I have the Link to the ECM charts above ^^

It lines up with the KNMI ensembles as theres a few spikes on the snowfall predictor!

18z whilst east is moving towards the Euros-

the key is the trough axis of the low pressure over the central states at 132-

on the 12 z its moving ENE-

http://modeles.meteo...12-0-132.png?12

On the 18z the energy is moving North supporting the blocking-

http://modeles.meteo...nh-0-132.png?18

So a better run around the 70N-

its just the early stages of the inital blast with the discrepancy against the euros-

tomorrow will reveal all as T72 is fast approaching-

S

Edited October 21, 2012 by Steve Murr

[BLAST FROM THE PAST]

Look at the synoptic pattern on the run, initial cold thrust is a tad less but at t120 18z is very much better placed for a more severe follow up and a sustained blocking and cold pattern. 18z at t120 smells heavily of reload

BFTP

[Cheese Rice]

Arguably a shunt east may be better for the UK in the long run, there is a strong correlation between extensive snowcover over North East Europe and cold spells for the UK.

[Geordiesnow]

There might be a re-load possibility but I don't care about that to be honest, that detail will change but the trend still remains the same and the question how far south and west any proper cold air will travel still remains a question without a certain answer yet sadly.

Not sure what to expect with the 00Z runs, the UKMO may backtrack but this model has been consistant in delivering the cold quite far south and west so we have to bear that in mind I suppose. Chasing down cold set ups is never easy it seems!

[Cloud 10]

The 18z looks to be lining up quite a strong cold front at 144hrs.

[BLAST FROM THE PAST]

And there we have it at t144.....GFS now back with Euros, much stronger block and northerly.......good night and await 00z now as the moving around of the GFS now takes me away from that model.....look for consistency...

BFTP

Edited October 21, 2012 by BLAST FROM THE PAST

[bobbydog]

Arguably a shunt east may be better for the UK in the long run, there is a strong correlation between extensive snowcover over North East Europe and cold spells for the UK.

exactly my thoughts earlier today

[shedhead]

Colder air shunted further eastwards again on the 18z, two successive runs now - this can't be discounted, will the other models follow suit on the 00z runs?!

Think the coldest air was always going to get shoved south across Scandi, no real surprises there, but perhaps what's more important is the emerging trend on GFS to develop a milder (relatively of course) NW'erly flow for the weekend. This may or not represent the start of a trend to unwind the depth of the cold, but given the time of year it is starting to look like an increasingly plausible evolution....lets see if UKMO and ECM pick it up tomorrow.

[Cloud 10]

Updated fax chart for friday looks to be close to the raw UKMO output,cold front just about

clearing the south coast,the 528 dam line pushing into Northern England.

http://www.meteociel.fr/ukmo/fax/fax120s.gif

[Geordiesnow]

And there we have it at t144.....GFS now back with Euros, much stronger block and northerly.......good night and await 00z now

BFTP

But its not though really, any re-load is coming via a shortwave from Greenland, the Euros don't show that at all! The initial Northerly does not back as far south and west as the ECM/UKMO either.

I think tomorrow morning runs will decide whether or not the UK will get a more full on force Northerly or not at the end of the week and anything after that is subject to change regardless whether tomorrow morning runs favour a colder shot by the end of the week.

[Zenarcher]

One positive thing on the GFS 18z is the high pressure doesn't get flattened down like on the 12z.

Exact same times 28th October 2am,

12z

18z

Edited October 21, 2012 by weathermaster

[Cheese Rice]

Already up to T177 we are seeing potential for another northerly, reload after reload after reload on the 18z.

Edited October 21, 2012 by Cheese Rice

[Suburban Streamer]

Weather master can I have the Link to the ECM charts above ^^

S

They are on Wunderground Steve

[SMU]

One positive thing on the GFS 18z is the high pressure doesn't get flattened down like on the 12z.

Exact same times 28th October 2am,

12z

18z

weather master you images show the difference in trough axis over the states on 12z V 18z

S

[weather_it_will]

what's more important is the emerging trend on GFS to develop a milder (relatively of course) NW'erly flow for the weekend. This may or not represent the start of a trend to unwind the depth of the cold, but given the time of year it is starting to look like an increasingly plausible evolution

Looks more North Easterly by Sunday @T162 on the 18Z and much colder than the 12Z and then back to a northerly on Monday@T192

Nothing milder about the 18Z

Edited October 21, 2012 by snow is falling