Model Output Discussion

[NorthNorfolkWeather]

We have to prepare for some serious downgrades and not get disheartened when, inevitably, they hit. The word you can't use enough when viewing charts in 'trends', nothing else counts for much and what we have been seeing is a trend for HP retrogression (how often do we see that happen?), Cold air to spill out of the Arctic and into Europe (Note I said Europe and not the UK ) and the jet to act very favourably in due course.

I stick by my original belief that we are going to get a short-lived relatively cold blast in 8-10 days time but it will be a precursor to a bigger one 4 to 7 days after that.

Great comment, I'll try to keep it in mind :-)

You are spot on, downgrades all the way if we are not careful

[LomondSnowstorm]

I often think an indicator of a cold shot, or at least a near miss arriving is a big spread on the ensembles - I think it's fair to say we have this tonight (in the latter part of the run at least):

http://www.netweathe...ensviewer;sess=

Yes, a huge range tonight, although both the control and the operational stay fairly close together, making the difference with the parallel run even more interesting! It does look to be very much a hit or miss, with not all that much between -10 and +5 upper air temps! Also, most of the ensemble lines dip well below the -5 850hpa temp line at some point in the run, which is rather positive, though most go cold at different points in FI! It could all turn to nothing but a brief dry spell, but a very cold spell is still potentially on the cards.

Edited December 4, 2009 by LomondSnowstorm

[Snowstorm1]

Lol, we had enough of this last winter - there is always something or another missing from a run, it's seldom relevant though - if there are data issues you will see it here:

http://weather.noaa.gov/tgstatus/

The messages you're linking to are technical bulletins and generally aren't relevant to the validity of the output.

Just saying lmao

[NorthantsSnow]

The pressure ensembles for Iceland:

http://209.197.11.115/c9s4a5k3/cds/ensimages/ens.20091204/18/prmslReyjavic.png?dopvhost=charts.netweather.tv&doppl=0f36092b442f94c9447f949995ba9fd2447f947d&dopsig=3e1eb1cc168d99f6e1375972dc412aa9

Not much change compared to the 12z data in terms of the mean, peaking at a fraction under 1020mb.

[Welsh_Weather]

Can't help but look at the moscow ensembles,control and operational both well off the bottom of the chart.

good post there cloud! its well worth a mention, there are a lot of members sub -20 there and if anything is coming from the east that has to be good news. The building blocks are in place

[Cloud 10]

If it happens, I'll take some time off work and go to stay with mum for a week! :whistling:

Karyo

Great example of an outlier there on the athens ensembles.

[SP1986]

If it happens, I'll take some time off work and go to stay with mum for a week!

Karyo

It shows literally there would be -15C in Serres, I think I'd go with you just to experience that

[swilliam]

Great example of an outlier there on the Athens ensembles.

Excellent - as Stephen Prudence said earlier maybe this is implausible but with a good reason to say so this time. Do you think the Greek weather sites are discussing this evolution with a lot of enthusiasm - or do you think they are not as sad as us Brits who are always talking about the weather. Gosh - I hope this does not happen now!

Edited December 4, 2009 by swilliam

[LomondSnowstorm]

Great example of an outlier there on the athens ensembles.

That is one heck of an outlier, about 10C away from the nearest run!

[karyo]

It shows literally there would be -15C in Serres, I think I'd go with you just to experience that

Yes, we'll be ice skating in lake Kerkini! It is one hell of an outlier though!

Regarding the UK, I'll be happy to experience inversions under a high pressure spell until the situation becomes more favourable for a wintry outbreak!

Karyo

[TEITS]

Wow some stunning ensemble members which remind me of Dec 31st 1978.

A simple summary of the models is there is likely to be two outcomes. We either see HP being centred near the UK bringing settled, chilly conditions or a real blast from the E/NE. The perfect outcome would be an E,ly followed by a N,ly as HP transfers from Scandi over to Greenland with the PFJ running to the S i.e 1978/79.

However a word of caution. If some of those ensemble members actually verified your preparations for xmas could be severely hampered. The combination of -15C upper temps spreading across a relatively warm N Sea, combined with the very weak sun would cause absolute chaos. I actually think the convective snowfall would be even heavier than Jan 1987.

Personally I would be happy with a settled, frosty spell and any blast from the E would be a bonus. However due to xmas even im a little unsure whether I would want some of those ensemble members to verify!!

[SP1986]

Inversions seem to occur when a night goes below freezing, fog forms as a symptom and the next day temperatures don't rise above freezing (or struggle to). However this can be a slow process which rarely occurs within the first day of the high. Much of the process involved needs pollution to work to form the inversion, so whilst inversions conditions would happen eventually, they wouldn't happen straight away, and of course it depends on how long the high is around for.

Even High pressure sitting over the country doesn't always guarantee an inversion, it's one of those things where it probably occurs as much by chance as it does owing to a specific set of conditions.

[Nights King]

Wow some stunning ensemble members which remind me of Dec 31st 1978.

A simple summary of the models is there is likely to be two outcomes. We either see HP being centred near the UK bringing settled, chilly conditions or a real blast from the E/NE. The perfect outcome would be an E,ly followed by a N,ly as HP transfers from Scandi over to Greenland with the PFJ running to the S i.e 1978/79.

However a word of caution. If some of those ensemble members actually verified your preparations for xmas could be severely hampered. The combination of -15C upper temps spreading across a relatively warm N Sea, combined with the very weak sun would cause absolute chaos. I actually think the convective snowfall would be even heavier than Jan 1987.

Personally I would be happy with a settled, frosty spell and any blast from the E would be a bonus. However due to xmas even im a little unsure whether I would want some of those ensemble members to verify!!

jan 1987. hmm i remember that well as my first winter that i can remember as a child and probably the one that started my snow obsession.

Only thing is i lived in the south east back then in high wycombe so had a far higher chance of seeing ppn in an easterly. Sadly all it means to me now is a cold wind with mainly clear skys. Only a couple of tiny flurrys make it this far at best. Charts look great in Fl as usual although probably wont get a sniff. I think we will get high presure over the uk towards xmas period and maybe at least a cold crisp xmas with a nice inversion giving us a couple of ice days with it.

[SP1986]

no wonder people are getting over-excited

[damianslaw]

As I stated yesterday, the building blocks for a colder settled spell as we head toward the middle of the month could easily come quite unusually from heights building from the south. These heights are beginning to show their hand in the reliable timeframe.. the overall outlook is a good one for cold from mid month onwards.

[swilliam]

no wonder people are getting over-excited

what do you mean?

[Cecil Hogmanay Melchett]

what do you mean?

Yes i was thinking that???Anyway,i might try to stay up for the 0z,in fact on 2nd thoughts i won't.If an Easterly

gets to within 144 i might though.

[Snow Queen one]

Eye if things pan out like Jan 87 then i will be very happy. I loved the snow that year even though i was in a house with no central heating. But i still doubt the models are getting it right yet.

There is loads of time though so all to play for.

[SP1986]

I meant that when 1981, 1987 and 1978 etc are being quoted no wonder people are getting excited. I wouldn't be that confident until the suggested pattern comes into the reliable timeframe on both the ensembles (at least 50% agreement), all of the big models and on the GFS operational 144 hours or closer... if all these are met then we have a very good chance of it occurring, at the moment however it's all very much a soup of uncertainty even though it appears to look promising (which is does I accept that )

[Cecil Hogmanay Melchett]

I meant that when 1981, 1987 and 1978 etc are being quoted no wonder people are getting excited. I wouldn't be that confident until the suggested pattern comes into the reliable timeframe on both the ensembles (at least 50% agreement), all of the big models and on the GFS operational 144 hours or closer... if all these are met then we have a very good chance of it occurring, at the moment however it's all very much a soup of uncertainty even though it appears to look promising (which is does I accept that )

Yes i agree steve.

Long way to go before we can even think about 1987 etc.

I wouldnt be suprised to see the models rubbish again in the morning,in fact im expecting it.

[swilliam]

I meant that when 1981, 1987 and 1978 etc are being quoted no wonder people are getting excited. I wouldn't be that confident until the suggested pattern comes into the reliable timeframe on both the ensembles (at least 50% agreement), all of the big models and on the GFS operational 144 hours or closer... if all these are met then we have a very good chance of it occurring, at the moment however it's all very much a soup of uncertainty even though it appears to look promising (which is does I accept that )

Ok thanks - that is much clearer- and yes I agree

Edited December 5, 2009 by swilliam

[MR EXTREMES]

Wow some stunning ensemble members which remind me of Dec 31st 1978.

A simple summary of the models is there is likely to be two outcomes. We either see HP being centred near the UK bringing settled, chilly conditions or a real blast from the E/NE. The perfect outcome would be an E,ly followed by a N,ly as HP transfers from Scandi over to Greenland with the PFJ running to the S i.e 1978/79.

However a word of caution. If some of those ensemble members actually verified your preparations for xmas could be severely hampered. The combination of -15C upper temps spreading across a relatively warm N Sea, combined with the very weak sun would cause absolute chaos. I actually think the convective snowfall would be even heavier than Jan 1987.

Personally I would be happy with a settled, frosty spell and any blast from the E would be a bonus. However due to xmas even im a little unsure whether I would want some of those ensemble members to verify!!

id be very very unsure i cant see this even close to that setup.

but right now its Swearing AGAIN i*g down big time i mean total flooding.

Edited December 5, 2009 by badboy657

[pyrotech]

That is very true, but still its good to see a bit of consistancy in the models, i think Europe will get the cold now, but it will be up in the air till 48hrs for us in UK. But would anyone not agree that even if just Europe for now would be a huge upgrade from what we have all had in last few weeks. Its a definite heading in the right direction although i understand that if it does not effect us directly some will see it as a huge disapointment. We need to look at the big picture. This euro cold is a great start to what has bn a mild wet period so far. GFS will upgrade and downgrade on every run, but looks good for Northern Europe and 20% chance for uk which is 19% better than anything so far.

I still think 80s winter but thats from research into solar minimum. Not latest GFS charts.

[SP1986]

I do definitely agree that if the cold air does flood into Europe it helps somewhat, but it would only help if the UK were to receive a southerly high pressure spell afterwards or a northerly low pressure spell. If the Atlantic comes in then the potential is ruined for a while.

[Eugene]

Personally I would be happy with a settled, frosty spell and any blast from the E would be a bonus. However due to xmas even im a little unsure whether I would want some of those ensemble members to verify!!

Yes my thoughts exactly just some nice inversion type cold would be good for starters and anything better would be a bonus, its silly to expect the holy grail all the time in the UK as it very rarely occurs, GFS 18Z looks strange in building a strong HP cell just to our north then quickly collapses it, looks completely wrong to me that the atlantic would get in as easy and as quick as 18Z says.