Model output discussion - 1st December onwards

[Singularity]

Well, we do see signs of that idea of ridging from the SW on the +240 ECM det. chart but by that time a number of questionable developments have been and gone; first the inability of the model to clear an area of low heights away from Svalbard after +144, which GFS has been doing quickly to allow that cross-polar ridging to develop, and second the large, organised low +168 to +192, which requires the smaller disturbances on the previous day to phase near-perfectly. It doesn't often go as cleanly as that.

Anyway, it's worth keeping in mind that blocking to our NW late month may be achieved via a UK ridge, in which case a mid-Atlantic trough and Euro Ridge is a likely precursor. We just need the Arctic profile to play ball, which is where that Siberian trough causes some irritation on the ECM 12z det. - I'm glad it's at the range at which it is.

 

In the meantime, I must admit that the proximity of the cold air to our east at +168 on that run has raised an eyebrow on my face - with so many disrupting troughs I suppose there has to be a chance that one will produce an occluding frontal boundary scenario with the cold air mixing in enough to produce a period of frontal snow, this most likely across the far northeast.

Worth noting that should the disturbances at +144 make a total hash of phasing, further sliders would become a possibility going forward. I've seen it happen before as the assumptions required to keep the computing power from being unreasonable lead to such potential tending to be under-represented. At least, that was the case several years ago - upgrades since then may have changed that for all I know.

[Day 10]

2 minutes ago, nick sussex said:

Keep the faith Phil. At least the cold air is close compared to December when it was on Mars! A few tweeks could make a big difference to the UK in terms of snow.

Totally agree hence my earlier post re: ecm temp charts, like you say at least the cold is A LOT closer and we are still in the game for 'possible snow and cold'. Better than no chance atall, still worth checking the outputs anyway at the present time.

[Methuselah]

3 minutes ago, nick sussex said:

Keep the faith Phil. At least the cold air is close compared to December when it was on Mars! A few tweeks could make a big difference to the UK in terms of snow.

Well, Nick - I, for one, will not be keeping any 'faith'...If cold and snowy easterlies do arrive - it'll be nowt to do with 'faith'!

[knocker]

4 minutes ago, Singularity said:

Worth noting that should the disturbances at +144 make a total hash of phasing, further sliders would become a possibility going forward. I've seen it happen before as the assumptions required to keep the computing power from being unreasonable lead to such potential tending to be under-represented. At least, that was the case several years ago - upgrades since then may have changed that for all I know.

I'm afraid I have no idea what that means. What assumptions are required?

[nick sussex]

Just now, Polar Climate said:

Totally agree hence my earlier post re: ecm temp charts, like you say at least the cold is A LOT closer and we are still in the game for 'possible snow and cold'. Better than no chance atall, still worth checking the outputs anyway at the present time.

I think this morning was a dip in possibilities. This evening overall I think things have edged a little more favourable. Of course it would be great if we were talking of a block further west ,a more traditional Scandi high set up. The issue has always been the block being over Russia so we're reliant on some pressure rises near Iceland and further north.

 

 

[Methuselah]

6 minutes ago, nick sussex said:

I think this morning was a dip in possibilities. This evening overall I think things have edged a little more favourable. Of course it would be great if we were talking of a block further west ,a more traditional Scandi high set up. The issue has always been the block being over Russia so we're reliant on some pressure rises near Iceland and further north.

 

 

I can't agree with that, Nick: the models may be undecided but the weather isn't. I think that that axiom may well be what underlies all the numerical-models, anyhoo?

[DAVID SNOW]

8 minutes ago, nick sussex said:

I think this morning was a dip in possibilities. This evening overall I think things have edged a little more favourable. Of course it would be great if we were talking of a block further west ,a more traditional Scandi high set up. The issue has always been the block being over Russia so we're reliant on some pressure rises near Iceland and further north.

 

 

Nick, I know its way out in la la land, but have you ever seen zero scatter on the precipitation ens  like what the GFS12Z is showing for mid Jan?  (don't think I ever have)

 

[nick sussex]

Just now, Ed Stone said:

I can't agree with that, Nick: the models may be undecided but the weather isn't. I think that that axiom may well be what underlies all the numerical-models, anyhoo?

Have you been on the Christmas sherry again? ! Of course the weather happens and the NWP is just doing its best to anticipate what will happen. As for the axiom bit enough with that sherry! lol

[Grimsby Snow Lover]

8 minutes ago, DAVID SNOW said:

Nick, I know its way out in la la land, but have you ever seen zero scatter on the precipitation ens  like what the GFS12Z is showing for mid Jan?  (don't think I ever have)

 

To add to your post there seems to be quite a pressure rise towards the middle of the month so perhaps that's why.  We might even get the odd air frost!

Edited December 30, 2015 by Grimsby Snow Lover

[Nick F]

Sneaky peak at the EC day 8 for the 6 hour snowfall - better potential for battleground snowfall even to lower levels, though milder air eventually wins out

 

The ECM ens for London have had quite a few colder members than the det. on recent runs, so be interesting to see where the 12z det. sits ...

 

Edited December 30, 2015 by Nick F

[nick sussex]

3 minutes ago, DAVID SNOW said:

Nick, I know its way out in la la land, but have you ever seen zero scatter on the precipitation ens  like what the GFS12Z is showing for mid Jan?  (don't think I ever have)

 

Yes a bit strange perhaps some bizarre coincidence. I suppose its even a greater shock that no rain might be forecast for a few days in the UK! lol

[Man With Beard]

Funny, looking at ECM T72 and T168 in isolation:

you wouldn't think much had happened in between!

Will be interested in how "certain" the ensembles are on the positioning of the Atlantic trough at T192 onwards. If there's high certainty, then this is a three day cold snap for the Highlands and possibly a one day cold snap for the rest of the UK (South and West coast excepted!) before mega-mild returns on Thursday.

Will any ensembles slip another depression through the gap between Atlantic low and Euro low though? Now that's when things would get interesting. We have, of course, seen instances in the past where, day after day, the Scandi High is modelled to "die" at T144/T168 but by T96/T120 it's back (N.B. LOW PROBABILITY WARNING!!!!!!!).

 

[phil nw.]

26 minutes ago, nick sussex said:

Keep the faith Phil. At least the cold air is close compared to December when it was on Mars! A few tweeks could make a big difference to the UK in terms of snow.

It still there Nick as the NH pattern is certainly changing. Such a near miss for us as that cold skims the far NE though.

I think we now have to see what happens upstream again rather than to the fading Russian block.The ens going with the Greenland/Atlantic vortex weakening later on

http://modeles7.meteociel.fr/modeles/gens/run/gensnh-21-5-300.png?12

so we will have to hope we get some decent ridging over the Atlantic which may bring something colder from the north/north west.

 

[Methuselah]

6 minutes ago, nick sussex said:

Have you been on the Christmas sherry again? ! Of course the weather happens and the NWP is just doing its best to anticipate what will happen. As for the axiom bit enough with that sherry! lol

Well, were it not for that axiom, wouldn't all numerical models be bunk? If the weather is, as you seem to be suggesting, impossible to predict - what is the point? We may, as well, all go home?

[nick sussex]

1 minute ago, Ed Stone said:

Well, were it not for that axiom, wouldn't all numerical models be bunk? If the weather is, as you seem to be suggesting, impossible to predict - what is the point? We may, as well, all go home?

I wasn't suggesting that but merely musing on how things would be less complicated if the block had been over Scandi rather than Russia. Enough with that sherry get the coffee out and put a few spoons in!

[booferking]

4 minutes ago, Man With Beard said:

Funny, looking at ECM T72 and T168 in isolation:

you wouldn't think much had happened in between!

Will be interested in how "certain" the ensembles are on the positioning of the Atlantic trough at T192 onwards. If there's high certainty, then this is a three day cold snap for the Highlands and possibly a one day cold snap for the rest of the UK (South and West coast excepted!) before mega-mild returns on Thursday.

Will any ensembles slip another depression through the gap between Atlantic low and Euro low though? Now that's when things would get interesting. We have, of course, seen instances in the past where, day after day, the Scandi High is modelled to "die" at T144/T168 but by T96/T120 it's back (N.B. LOW PROBABILITY WARNING!!!!!!!).

 

What time does the ensembles come out at . Thanks for replys

[Man With Beard]

Just now, booferking said:

What time does the ensembles come out at . Thanks for replys

Won't see the individual ECM ensemble members past T120 except on a line graph, unfortunately (unless you pay for them). Ensemble mean charts out in a few minutes on Meteociel.

[Methuselah]

But that's what I mean, Nick - the block isn't over Scandinavia. Ergo, we all need wait a while before we see any meaningful cold? 

[booferking]

3 minutes ago, Man With Beard said:

Won't see the individual ECM ensemble members past T120 except on a line graph, unfortunately (unless you pay for them). Ensemble mean charts out in a few minutes on Meteociel.

Cheers Ensembles mean has been trending colder than the op hope it keeps it up will soon find out thanks.

Edited December 30, 2015 by booferking

[nick sussex]

Some tasty ECM postage stamps at T120hrs, a mix of solutions for T120hrs. Theres still uncertainty as to whether we'll see the elongated shortwave energy or a single low heading ese.

I think judging by the low orientation and what we can see of the pattern to the nw that theres some support for the NAVGEM solution.

Of course at this timeframe you'd factor in the operational run more but still as far as the ensembles are concerned a lot of uncertainty with the all important detail for the UK in terms of shortwave/low.

http://old.ecmwf.int/samples/d/inspect/teasers/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!120!pop!od!enfo!enplot!2015123012!!/

Looking at the short De Bilt ensembles theres a cluster that brings the colder air much quicker to Holland, the operational is in a decent cluster later that support its solution to bring some of that deeper cold westwards around T144 to T168hrs. The ensembles are at the present time resolute in pushing the Atlantic in at days 9/10.

http://cdn.knmi.nl/knmi/map/page/weer/waarschuwingen_verwachtingen/ensemble/detail/ensemble-verwachtingen-detail10.png

 

Edited December 30, 2015 by nick sussex

[winterof79]

Snow at 192z on ECM ?? For how long

http://www.meteociel.fr/modeles/ecmwf/runs/2015123012/ECM0-192.GIF?30-0

[karlos1983]

What I find amazing is I'm sure today it was supposed to rain all day in the north west England and south west Scotland and to my eye, it did not. And here we are arguing about day 6. 

[knocker]

If you look in detail at the ecm output all of that snow occurs in the 12 hours from T180 as the front approaches from the west and it's also very borderline. At this stage I don't think it warrants much discussion.

Edited December 30, 2015 by knocker

[winterof79]

Love a pincer move on the vortex from Russia and Canada

http://modeles.meteociel.fr/modeles/gfs/runs/2015123012/gfsnh-0-144.png?12

[Paul_1978]

8 minutes ago, karlos1983 said:

What I find amazing is I'm sure today it was supposed to rain all day in the north west England and south west Scotland and to my eye, it did not. And here we are arguing about day 6. 

I am currently in Portpatrick, south west Scotland Coast and whilst I can say it did not rain particularly much here, you only had to go a few miles in land (Newton Stewart) to find the worst floods for 50 years. So it most definitely did rain in south west Scotland as a general rule. 

 

As as for the models, I'm finding the overall Northern Hemisphere pattern very interesting. It's not like it has been for the last 6 weeks or so.