Model Output Discussion

[LomondSnowstorm]

Last one from me

2 histoic charts from the archives- take note of the dates & what historic weather occured just days later-

http://www.wetterzen...00119870107.gif

http://www.wetterzen...00119850101.gif

http://www.wetterzen...slp19470118.gif

Now look at this......

http://www.wetterzen...cs/Rtavn841.png

This is why we are hoping & praying this doesnt fall apart-

S

Not to blow my own trumpet too much, but I believe I did post some of those charts when the high first came on the scene

It does look very solid at the moment, but we still have a day or two before we can say it will occur for certain (or at least around 80-90%).

Hope this does come off, I don't think I've ever seen charts with such potential in my short weather watching life.

Just hope it isn't gone by the 12Z tomorrow, if not, I'll be ecstatic.

LS

[BLAST FROM THE PAST]

OK here's the gist from my perspective. A winter beckons where the jet wants to and will readily be on southerly track with northern blocking however, a strong jet will make for chopping and changing set ups. The colder feed starts from Friday onwards...cooler first getting progressively colder...I agree with JH that the COLD setup WILL occur. Now IMO and method this isn't the real deal.....yet, a sudden much milder outbreak occurs say after 7-10 days so 12-21/2 [i think 5 -7 days of potent cold in there]. Renewed cold surge forms early New Year.

I may be wrong as the cold seems to start before the initial midmonth RJS and I mention in our LRF, but basically the longevity of cold looks the same just 3-4 days earlier in its commencement. However, i am mindful that when a pattern like this does happen it is hard to get rid of. The sun has gone into another deep sleep so it will be interesting to see if it sparks up...that may signal the mild insurgence.

regards

BFTP

[Stu_London]

I think people should perhaps prepare themselves for some disappointments

Given that the situation as shown on the 18z operational is a little bit marginal, and given the inevitable last minute downgrades, I think this event (which is probably now a shade of odds on to occur) is likely to deliver to the few rather than the many. We may see snow falling thorugh the air or sleet especially at sea level.

I have witnessed -10C 850s and an easterly deliver temps of 1C and wet non settling snow. This event is progging 850s around -7C

What is in our favour is for once we might get something at the time of minimal solar radiance and there will be time to look at things like ground and air temps, dewpoints etc when we are +72 and below.

However, extreme caution advised, this is likely to be a MARGINAL event.

[Tom Montalbano]

Hi reef,

They really are an impressive set of ensembles. Like you, I wont be happy until we're inside t96.

I remember how gutted we all were with the example Steve M. often quotes, from a few years ago. The 18z on the Saturday night had a fantastic 18z showing a prolonged bitter easterly after days of similar charts, only to wake up to a horror show with high pressure over the UK not linking to high pressure to our NE, scuppered by shortwaves and that was at t96. So a fair way to go yet. Steady as she goes!

Regards,

Tom.

[Guest North Sea Snow Convection]

Last one from me

2 histoic charts from the archives- take note of the dates & what historic weather occured just days later-

http://www.wetterzen...00119870107.gif

http://www.wetterzen...00119850101.gif

http://www.wetterzen...slp19470118.gif

Now look at this......

http://www.wetterzen...cs/Rtavn841.png

This is why we are hoping & praying this doesnt fall apart-

S

Identity shiver comparison Steve!

Does rather make the significance ever bigger!

Warnings always heeded by me - I started from a position of just wanting an end to the atlantic onslaught and that has not changed

Edited December 7, 2009 by North Sea Snow Convection

[Stu_London]

Pretty good ensembles too tonight with the majority of the ensembles now going for some sort of cold spell in the south:

http://www.wetterzentrale.de/pics/MT8_London_ens.png

Further north and its delayed slightly but theres better agreement. Less potent overall however:

http://www.wetterzentrale.de/pics/MT8_Aberdeen_ens.png

I have to stress though, we've been in situations where theres been 100% ensemble support at this range and its still not come to fruition. I wont be happy until its inside T+96.

The best set of ensembles to date on this spell. The warmer runs to the north of the UK are mostly as a result of warm sectors via shortwave activity so these areas may see cold rain (for a while at least). The situation further south is more on a knife edge, but a couple of significant upgrades to the strength of the cold would be needed for a cast iron guarantee of settling snow.

[snowmadchrisuk]

Pressure Ensembles for Iceland , Most members have high pressure in the region from Thursday night onwards .

[Cheese Rice]

I think people should perhaps prepare themselves for some disappointments

Given that the situation as shown on the 18z operational is a little bit marginal, and given the inevitable last minute downgrades, I think this event (which is probably now a shade of odds on to occur) is likely to deliver to the few rather than the many. We may see snow falling thorugh the air or sleet especially at sea level.

I have witnessed -10C 850s and an easterly deliver temps of 1C and wet non settling snow. This event is progging 850s around -7C

What is in our favour is for once we might get something at the time of minimal solar radiance and there will be time to look at things like ground and air temps, dewpoints etc when we are +72 and below.

However, extreme caution advised, this is likely to be a MARGINAL event.

Agree, even if this setup did downgrade it would more than likely bring significant snowfall to many areas, although temps will not be anything to shout about i do think the snow would be there. But as you said a marginal affair, but i would side on the right side of marginal in most cases.

If we looked at the Feb event that was downgraded quite alot but many areas saw there fair share of snow, granted it was always the wrong side of marginal on the coasts.

[kold weather]

When this set-up does take hold as you say Blast its a nightmare to get rid of. The ensembles are still really good but they are overall just a little further south with the upper high this run but its not too bad, certainly another step forward though IMO towards a cold spell.

Hopefully this holds for a while, quite a few runs dfo show a southerly jet and if that occurs this could be a long lasting, still early days however and the key evolution still a little bit too far away to be all that confident.

Still, a cold inversion high looks a certainty, that is right now the worst case set-up...which IMO is quite a good one really!

[reef]

Further to my last post, this is why I wouldnt be getting too excited until before T+96. Lets look at the ensemble agreement for the December 2005 easterly (not a dissimilar pattern).

The cooldown was to start on late christmas day, as the ensembles for christmas eve show:

T+24

T+48 - finally agreement.

T+72 - still massive scatter, but easterly looking likely.

T+96

And for fun, T+168 - no sign at all:

Notice how even at T+72 it was still up in the air. Puts it isnt perspective a bit when we're looking at T+144 and beyond for this one. A note of caution needed I feel.

[SP1986]

lasting, still early

Still, a cold inversion high looks a certainty, that is right now the worst case set-up...which IMO is quite a good one really!

Hmmmm I see where you coming from, but I wouldn't say it's 100% certainty yet re: inversion. With the air that is shown on the 18z at the time the high comes in, I think inversions will be localised rather than widespread. I also think any inversion will be shallow. The lower atmospheric temperature profile looks a little shaky for widespread inversions.

[kold weather]

Quite right there Reef, but I remember with that one the models progged a fairly zonal flow with the high pressure being shunted to out SE. Eventually they built the high up and then keyed into a easterly flow. As you say though I wouldn't be too confident just yet, esp with the models slowing down the evolution of this pattern.

Stephen, yeah its not a certainty thats for sure, but if the high does settle over the UK instead we'd have a good 5-7 days at least with HP over us so I think it would be quite possible that it would develop even if not right away. Also fog has to be major concern with such a wet ground.

Edited December 8, 2009 by kold weather

[nick sussex]

Regarding the ensembles as we've seen from Reefs post just how useful were they, its often the case with easterlies they're poorly modelled and often appear out of nowhere. Which definitely reflects the recent output, it was only when the models started hinting at the euro high ridging north that they went the next step.

[swfc]

Given the high has not even built over the uk i find some posts quite strange regarding the vsituation next week.????.Just see how it pans out because its certain the outcome will be quite aways from the current output.The outlook is good compared to the last few weeks and at worst it will be more seasonable.

[Iceni]

18z GFS, the days before xmas = Jan 63!

ok, lets come back to the reality of the t120 shortwave?

Watching these charts and listening to the Beatles and winter of 62/63 when they exploded onto dull 50s Britain (on BBC4) is bringing it all back home… feel quite emotional actually. Where do I find the 18z GFS parallel run — I want more chart porn <_<

[SMU]

Regarding the ensembles as we've seen from Reefs post just how useful were they, its often the case with easterlies they're poorly modelled and often appear out of nowhere. Which definitely reflects the recent output, it was only when the models started hinting at the euro high ridging north that they went the next step.

& after I mentioned feb 09 fiasco from last year the ensembles work badly is reverse as well-

image courtesy of Darren ( retron on TWO)

LOL- All because of a shortwave in a VERY similar situation.... thats a 13 degree swing on the 18z operational run over 24 hours-

lets be cautious......

Steve

Edited December 8, 2009 by Steve Murr

[nick sussex]

Watching these charts and listening to the Beatles and winter of 62/63 when they exploded onto dull 50s Britain (on BBC4) is bringing it all back home… feel quite emotional actually. Where do I find the 18z GFS parallel run — I want more chart porn

Well luckily here i've got a satellite dish so have had Xmas songs playing all day on that cheesy station Bliss, how about this as their on screen Xmas logo, Merry Blissmas! tacky but i just love it! :smiliz19: Talking about emotional try December Song by George Michael on you tube, that will have you in tears, a brilliant Xmas song but the video is really quite sad!

Back on topic yes the parallel run is superb for the se, stuff of dreams, i wonder whether the parallel run can improve the gfs verification stats in the future, it still seems to be lagging behind the ecm.

I see SM has talked about that traumatic Feb shortwave drama, well that surely shows why we can take nothing for granted!

Edited December 8, 2009 by nick sussex

[Guest North Sea Snow Convection]

There was no real -AO pattern back in Dec 05. It actually yielded, relative for the synoptic set-up an excellent 3 day easterly (and some days of fun in the snow!)

There is no blanket comparison imo in terms of outcome from one synoptic set-up to the next. Yes we have to look out, as usual, for shortwaves in all the expected areas - but we must also try and take each set up on its merits. We haven't had the sort of current set up with a modelled arctic high in early Dec for quite a while and whilst it still might not deliver for the UK, we should equally caution against predicting/expecting the same outcome in every scenario. That can get as unrealisitically over cautious/pessimistic as expecting an ice age with every pretty cold synoptic chart that the models try and seduce onlooksers with.

Ian B to his great credit, has been very objective in his analysis in that regard in the last few days and made some very balanced posts.

Last winter was not an exceptional freeze, but it did enough to exemplify the point i make above. No situation is the same, irrespective of what any 20 year trend may appear to suggest.

Watching these charts and listening to the Beatles and winter of 62/63 when they exploded onto dull 50s Britain (on BBC4) is bringing it all back home… feel quite emotional actually.

I'm not quite old enough - but I am old enough to appreciate and agree with what you are saying there !!

[snowray]

& after I mentioned feb 09 fiasco from last year the ensembles work badly is reverse as well-

image courtesy of Darren ( retron on TWO)

LOL- All because of a shortwave in a VERY similar situation.... thats a 13 degree swing on the 18z operational run over 24 hours-

lets be cautious......

Steve

It has to be said that the models that week were disgusting!

[The Eagle]

FWIW 18z NOGAPS is the final model tonight and probrably the best at 144hrs.

http://www.meteociel.com/modeles/nogapse_cartes.php

Edited December 8, 2009 by The Eagle

[Duane S.]

Another day, no downgrades. This is equivilent in my book to an upgrade as we edge nearer the 'reliable time frame' whenever the heck that is.

I still refuse to believe we can just sail day by day towards this potentially huge event without any serious blips. But the fact the 3 main models are producing runs so similar to eac other and other factors like the steady day on day mean air pressure increases over Iceland plus the ensembles in general make me wonder if we can do it this time!??

What about the parellel charts then? If this happens then we should all be taking off our collective hats to this model which has been consistently and relentlessly telling us that this WILL happen!

But as SM says above, so much can change and with very little time left too. Long way to go...

[kold weather]

Thats very true steve, I remember that because at one point it really looked like we were going to have an exceptional month...however each situation is different and as I said before we do have the added backup of a decent high that should be getting quite cold if it hangs around. Still things can and quite possibly will go wrong, we shall see, each passing day gets us closer to where we need to be.

[ScottSnow]

I've been model watching since 2002 so have been through all the 'letdowns' that we have had in the past. I said nearly a week ago that a cold spell was on the cards and it looks as though that this is still the case.

I'm trying not to get too excited but it is difficult. Like KW said the possible worse case scenario is inversion cold which can only be a good sign.

Hopefully it won't go pear shaped and it will prove that we can still have a good cold spell in the 'even larger teapot'.

[Guest]

As people have said, a dry high, though with some cloud getting mixed up in it at some stage.

[PersianPaladin]

http://www.wetterzen...s/Rtavn2521.png

Non-stop Easterly from Russia to Newfoundland :smiliz19: We've seen these before tho in FI!

Reverse-zonality. I can't quite remember the last time we had that.