Model Output Discussion 4th Dec.2013-12z onwards.

[Allseasons-Si]

 

that looks scary now@ t138

 

snow in hi res too

 

 

really interesting stuff to talk about up to the festive season that's for sure.

[TSNWK]

18z even from around 138 there appear to be more heights building over the pole and the vortex is far more enlongated, this has continued out to 156 so far a postive step I would have thought... Lets see

[weirpig]

gfs-0-138.png

 

that looks scary now@ t138

 

snow in hi res too

 

gfs-2-138.png

 

really interesting stuff to talk about up to the festive season that's for sure.

yep wait for the express headlines

[UKWeatherman]

Wow.......

 

If the 18z verifies then battern down the hatches because this is a MONSTER!!!! 

 

 

[bradymk]

This run demonstrates the changes we are likely to see run to run. This pattern is likely to result in development of secondary lows and rapid cyclogenesis etc which may have a big effect on future timeframes. That's a nasty low on the GFS 18z

[Captain Shortwave]

Vicious low there, but it's a movement towards the UKMO from the GFS, better ridging northwards ahead of the low which slows the progress of the Atlantic train later on. Maybe the UKMO is onto something here.

[nick sussex]

The GFS 18hrs run develops a hideous looking low pressure,  with this type of set up these rapid developments off the main trough are possible. It interestingly makes less of low heights to the ne so perhaps a small shift there to the UKMO.

[R.P. McMurphy]

The GFS 18hrs run develops a hideous looking low pressure,  with this type of set up these rapid developments off the main trough are possible. It interestingly makes less of low heights to the ne so perhaps a small shift there to the UKMO.

Yes Nick, That would be some force there, very windy indeed, wouldnt like to be on top of the hills during that.

 

UKMO looks to be onto something.

[bluearmy]

Yes Nick, That would be some force there, very windy indeed, wouldnt like to be on top of the hills during that. UKMO looks to be onto something.

Really ! Bit premature to say that. I rather doubt the 00z will repeat the output.

[nick sussex]

Yes Nick, That would be some force there, very windy indeed, wouldnt like to be on top of the hills during that.

 

UKMO looks to be onto something.

I do very much hope so, lets hope that low disappears tomorrow and we end up more with the UKMO trend.

 

This is the UKMO T144hrs, the main PV relocating towards Canada has solid support, the area of uncertainty is really to the ne of the UK, to force some changes to the jet axis its key to get some pressure rises there, this might add enough forcing to disrupt some energy to the se off the main troughing rather than this all spilling ne.

 

 

The UKMO seem to have gone with their raw output in the T120hrs fax chart, certainly I don't see a modification to the ECM there:

 

 

 

Edited December 13, 2013 by nick sussex

[Ali1977]

Scandy high maybe !!!

[Cloud 10]

The 18z is rampant with these LP''s and turbo-charged jetstream,another one for

christmas day/boxing day.

 

[TSNWK]

Much better fi on the 18z - vortex in two, with the main part enlongated from the uk to northern Canada, heights building to north east.

Boxing Day snowstorm for the north at the very least.. Yes I know it's fi etc.. But it's fun to look at

[R.P. McMurphy]

Really ! Bit premature to say that. I rather doubt the 00z will repeat the output.

The models were also predicting the quite large storm we had a few weeks back at least a week in advance, and it verified perfectly.

 

I also Echo Nick's thought's in his above post.

[OldMetMan]

Today's GFS has some bewildering changes, particularly the 12Z but before I go on, here's part of the NWS discussion earlier today:

"A RESHUFFLING OF THE UPPER PATTERN ACROSS THE PACIFIC/NORTH

AMERICA IS IN ORDER OVER THE NEXT WEEK AS THE HIGH LATITUDE VORTEX

REORGANIZES OVER THE CANADIAN ARCHIPELAGO. CONCURRENTLY... RIDGING

THE PACIFIC SHOULD BUILD ALONG 150W WHICH FAVORS WESTERN CONUS

TROUGHING AND EVENTUALLY EASTERN CONUS RIDGING. A RATHER QUIET

START EARLY NEXT WEEK SHOULD STEADILY BECOME MORE ACTIVE BY WEEK'S

END."

It's clear from today's 500mb chart how the main vortex is transferring from NE Canada to the Atlantic, hence the prolonged run of deep lows forecast to be heading our way in the next 10 days. Fair enough, but today's early GFS runs showed a slow down in cyclonic development with a very large upper vortex over much of the N Atlantic and progressively colder air coming our way from the NW. Further W, HP was shown to be predominating over much of the E of North America, which would seem to match the eastern ridging mentioned in the above guidance.

So far, so good, but then the 12Z GFS goes a bit mad, generating yet another massive, deep low pushing back the SW flow over us once again. This doesn't look right to me and certainly doesn't appear to have much relation to earlier runs.

Obviously, I shouldn't pay much heed to these variations in end of run developments but it seemed to me that the GFS had been following quite a logical progression earlier then suddenly overturns it. I see that the 18Z is more in keeping with earlier runs!

However, all the GFS weirdness apart, other models seem to be settling on this major N Atlantic vortex at the end of their respective runs, and a more direct, colder polar maritime flow as mentioned above. If this verifies, then, as the earlier GFS showed, there would be a very large and broad area of LP gradually sinking S and SE and filling, whilst new cyclogenesis originating off the Eastern Seaboard and heading our way would temporarily stop, maybe with a deeper, more slow-moving LP forming there and helping to build HP north of it.

Note too that over N Europe and Asia HP is shown gradually pushing NW towards the Pole. As I mentioned before, I still think that a HP build-up to our N could happen long term.

I am encouraged that the NWS guidance is recognising that, in the sort- to medium term at least, the upper flow is changing. We most likely might have to wait until New Year, but I will be interested to see if the GFS in particular revisits the earlier development in future runs.

Northerly blocking or not, the prospect of much colder (thickness less than 528) air coming our way seems more likely by Christmas or right after, with wintry precipitation accompanying it.

[kumquat]

Thursday 19th a day to keep an eye on. Waning Full Moon. Storm surge up the Severn?

[R.P. McMurphy]

The 18z is rampant with these LP''s and turbo-charged jetstream,another one for

christmas day/boxing day.

 

gfs-0-288.png

It's not too hard to imagine, especially with the active systems out west. I think we will see more in the way of LP systems pushing though quite rapidly as we head towards the big day, the question is, will it get cold enough to snow?

 

We need to see more of this getting colder.

 

[on the coast]

The storm shown next week is a very worrying feature. It looks very nasty. 

[Allseasons-Si]

The 18z is rampant with these LP''s and turbo-charged jetstream,another one for

christmas day/boxing day.

 

gfs-0-288.png

What a interesting 18z,shift this a few hundred miles west and we are talking,look at those hights to our east,plenty of options there to be had,i know it's fl,but ukmo could have this sooner,if it's right of cause

 

will this undercut,time will tell as always,more runs needed.

[Cloud 10]

The 18z NAVGEM has picked up on the gfs storm.

 

120 hrs..

 

 

great post by oldmetman. 

Edited December 13, 2013 by Cloud 10

[fergieweather]

Thursday 19th a day to keep an eye on. Waning Full Moon. Storm surge up the Severn?

This was precisely why the 00z EC of yesterday bothered us. As I noted here yesterday, albeit the 12z runs then 'lost' it, the potential couldn't be discounted.

[R.P. McMurphy]

This was precisely why the 00z EC of yesterday bothered us. As I noted here yesterday, albeit the 12z runs then 'lost' it, the potential couldn't be discounted.

 

Thanks Ian,

 

It's worth keeping an eye out for now... Albeit FI, but cannot be ignored.

[Gael_Force]

Good grief! that looks hideous...

 

[Long haul to mild]

I see the pub run is off on one tonight! Comparison between 18z and 12z below; considerably different!

[OldMetMan]

The 18z NAVGEM has picked up on the gfs storm.

 

120 hrs..navgem-0-120.png

 

 

great post by oldmetman. 

Thank you Cloud 10!