Winter Model Discussion - 12/01/13 06z Onwards

[Timmytour]

Disappointing ECM but GFS 6z much better

[irony] And don't forget, the ECM is well known for overblowing the influence of the Atlantic [/irony]

[phil nw.]

This pattern reminds me more and more of classic cold spells of the 60-80`s where the weakening jet cannot breakdown the entrenched cold block.

As Chiono.said the split vortex reduces energy going into the jet as it comes this side of the Atlantic.Therefore it takes an easier route under the heights to the north.

The low pressure over Europe looks an ever increasing trend which will ensure the pattern remains a cold one.

As this run goes we will some very low temps- especially over the snowfields as pressure rises later.

http://modeles.meteo...gfs-0-114.png?6

Edited January 12, 2013 by phil n.warks.

[mcweather]

I personally feel that the 06z can only really be used for trending and giving some idea as to how the next run will unfold.

With its missing balloon data, its obviously not the full bag of spanners, but its certainly handy to get some "idea" of what the next runs can be like.

I always take the 06 with a pinch of salt. If it manages to get to grips and output similar to other models that evidently there is a strong signal hidden in the data somewhere.

Missing ballon data or not at least its consisitent

[Dampdorset82]

Missing ballon data or not at least its consisitent

The difference will be if its consistantly right or wrong. Consistancy is not always good its more about trends

[kev238]

ECM should def not be disregarded in my opinion, even if it does not match the background signals. It is the best performing model if you look over long periods of time. Much as gfs could not be discounted when it was showing something different a few days ago.

Put simply, when there is a divergence with the big three proceed with caution. This means that up to Tuesday seems fairly clear, after that less so. Luckily with have snow in the reliable, for a lathe percentage of the country.

[bluearmy]

ECM should def not be disregarded in my opinion, even if it does not match the background signals. It is the best performing model if you look over long periods of time. Much as gfs could not be discounted when it was showing something different a few days ago.

Put simply, when there is a divergence with the big three proceed with caution. This means that up to Tuesday seems fairly clear, after that less so. Luckily with have snow in the reliable, for a lathe percentage of the country.

but the temps in the ens mid/latter period dont match the op. hence the ecm has a mean blocked latter period rather than a mobile one. not out of kilter with gfs - just depends where the blocking is centred.

[Met4Cast]

ECM should def not be disregarded in my opinion, even if it does not match the background signals. It is the best performing model if you look over long periods of time. Much as gfs could not be discounted when it was showing something different a few days ago.

Maybe this will change your mind

The Op was an outlier with little support. One of the best set of ECM ensembles I've seen so far actually with the mean not getting above freezing in the short term!

[johnholmes]

A number of folk understandably commenting on the jet having difficulty shifting the cold bloc.

I’ve been involved with the weather for over 50 years and’nowt has changed. In those days no computer models were around. The same rules of thermal dynamics apply whether it is a human or a computer trying to predict one day, 5 days or 55 days ahead. Yet we still have the same problem. Why, I have no idea-answers on a post card please, and I would imagine the senior man at Exeter would love to get one!

The difference will be if its consistantly right or wrong. Consistancy is not always good its more about trends

not quite true Dd

It is actually a mix with both being required

[EML Network]

Well I am very confused now, having just watched the BBC Forecast for Monday, it seems Monday that we have 2 separate ''rain / snow'' bands passing down the country , the first is likely to be more of a snow event, the second and the one that they are ''watching'' appears (at least going by the BBC graphics) to be mostly rain in the SE Corner (London included), but snow across E Anglia / Lincs , which falls in line pretty well with Netweathers own PPN type chart for the same period.

you can see the first band here running down the spine of the country ,(mostly all snow)...the main band is following behind it

here's the PPN charts for Monday evening

and the PPN Type charts for the same period

It's a close call, and my heart would love to see this all falling as snow, (if would be after dark and there will be snow preceding it)....time will tell, but I have a really bad feeling that those South of London.. Southern and Western.Kent / Eastern East Sussex / West Sussex / Southern and Western Surrey might get more of a mix of rain / sleet / wet snow as opposed to proper snow, a bit of IMBY-ardism I know but that's how I see things panning out for the SE Quadrant of the UK.

Folkstone and the extreme SE Tip look set for a real dumping as do more central areas on Monday.....AS THINGS STAND !!!

Edited January 12, 2013 by EML Network

[stainesbloke]

It's not really to do with the Scandi high pushing back - it is to do with the split vortices. Crossing the bridge from one to tother requires a big jump and that is why I suspect the ECM is wrong. As soon as the jet reaches mid Atlantic it loses the potential vorticity element of the Canadian sector and strong thermal gradient that this brings and will lose power immediately - hence the block appears to hold.

Interesting. Would you say then that it looks likely that the jet will sink SE and keep heights to our NE, rather than ride over the top of the Scandi high as often happens?

[stainesbloke]

Well I am very confused now, having just watched the BBC Forecast for Monday, it seems Monday that we have 2 separate ''rain / snow'' bands passing down the country , the first is likely to be more of a snow event, the second and the one that they are ''watching'' appears (at least going by the BBC graphics) to be mostly rain in the SE Corner (London included), but snow across E Anglia / Lincs , which falls in line pretty well with Netweathers own PPN type chart for the same period.

you can see the first band here running down the spine of the country ,(mostly all snow)...the main band is following behind it

here's the PPN charts for Monday evening

and the PPN Type charts for the same period

It's a close call, and my heart would love to see this all falling as snow, (if would be after dark and there will be snow preceding it)....time will tell, but I have a really bad feeling that those South of London.. Southern and Western.Kent / Eastern East Sussex / West Sussex / Southern and Western Surrey might get more of a mix of rain / sleet / wet snow as opposed to proper snow, a bit of IMBY-ardism I know but that's how I see things panning out for the SE Quadrant of the UK.

Folkstone and the extreme SE Tip look set for a real dumping as do more central areas on Monday.....AS THINGS STAND !!!

That would be crap if it happened Though the BBC use MO data and that doesn't mention rain for anywhere other than Wales/SW England.

[IDO]

Well I am very confused now, having just watched the BBC Forecast for Monday, it seems Monday that we have 2 separate ''rain / snow'' bands passing down the country , the first is likely to be more of a snow event, the second and the one that they are ''watching'' appears (at least going by the BBC graphics) to be mostly rain in the SE Corner (London included), but snow across E Anglia / Lincs , which falls in line pretty well with Netweathers own PPN type chart for the same period.

Latest warning from the Met. Just snow in south; 5cm low and 10cm higher.

http://www.metoffice.gov.uk/weather/uk/se/se_forecast_warnings.html

[Dampdorset82]

A number of folk understandably commenting on the jet having difficulty shifting the cold bloc.

I’ve been involved with the weather for over 50 years and’nowt has changed. In those days no computer models were around. The same rules of thermal dynamics apply whether it is a human or a computer trying to predict one day, 5 days or 55 days ahead. Yet we still have the same problem. Why, I have no idea-answers on a post card please, and I would imagine the senior man at Exeter would love to get one!

not quite true Dd

It is actually a mix with both being required

If for example the ECM had consistantly predicted mild sw weather and last min changed to cold that would have been consistantly wrong however if the ECM was forecasting every 2 out of 3 runs cold you would say its trending towards cold.....which I would be happier with

I agree a mix of the 2 would be best but that never happens........unfortunately

[Southern Storm]

Latest warning from the Met. Just snow in south; 5cm low and 10cm higher.

http://www.metoffice...t_warnings.html

Yes but its only for the next 24 hours

I would guess that they will update warnings for the rest of the country later tonight after having more data.

And to be honest, there is no point taking any notice of warnings until much closer the time especially when it comes to snow.

Edited January 12, 2013 by thunderman24

[Cecil Hogmanay Melchett]

uh uh gfs 06ens have shifted to an ecm type evolution mid range.

[Ian Williams]

Paul Blight over on UKww has done an excellent synoptic summary with what we can possibly expect over the next 4 or 5 days http://www.ukweatherworld.co.uk/forum/index.php?/topic/95683-synoptic-discussion-mid-january-2012-cold-or-mild/page__pid__838204#entry838204

[IDO]

uh uh gfs 06ens have shifted to an ecm type evolution mid range.

Yes the op is a cold outlier from mid-week and most members trend to the ECM milder scenario:

short GEFS:

[Buzz]

uh uh gfs 06ens have shifted to an ecm type evolution mid range.

Not quite - with the GFS op the jet splits, energy goes over and under the 'block', so it doesn't sink and we are left with cold temps. With the ECM op the energy ONLY goes OVER the block.

Edited January 12, 2013 by Buzz

[kev238]

Fair enough that the ECM seems to be a milder run. However, it has shown something similar last couple of runs and so def cannot be discounted. I hope it is wrong as love the cold weather with snow on the ground!!

My main point is that when the models show vastly different outcomes, neither is likely to be correct and a blend will occur, or something completely new.

[Cecil Hogmanay Melchett]

yes a big switch on the 06z suite hmm could ecm be leading the way???

[Craigers]

What I like about this mornings output is the growing trend of the low pressures from the Atlantic to undercut the block. This keeps me happy :-)

[bluearmy]

Yes the op is a cold outlier from mid-week and most members trend to the ECM milder scenario:

short GEFS:

Have u looked at surface temps and sypnotics ?

[Froze were the Days]

Noticed the GEM 0z is very similar to the UKMO at 144z and goes only one way and that is to undercutting and very cold conditions thereafter.

[bradymk]

Have u looked at surface temps and sypnotics ?

yes southern half of the UK still struggling to get above freezing on 2m temp. Spread at 180 is huge, in a key area for developments for us

Edited January 12, 2013 by bradythemole

[Southern Storm]

Yes the op is a cold outlier from mid-week and most members trend to the ECM milder scenario:

short GEFS:

They are not bad at all!

at day 5 the mean is around -7 and the cluster is tightly grouped compared to of late.

Edited January 12, 2013 by thunderman24