Model Output Discussion 29th December - Into mid-Winter.

[BLAST FROM THE PAST]

7 minutes ago, Froze were the Days said:

 

 

Don't curse it Fred - you were pretty 'hot' on a cold spell come mid-December which never materialised, fingers crossed and anything that can be...we need some luck on our tiny Isles!

 

 

Cursing nothing, we had exact opposite mid Dec, quite extreme really but I kept with the original thoughts, as wrong is wrong.  But we have zero consistency generally as run for run rolls out.  I suppose that is the rollercoaster.  

Now for the 18z.......

 

BFTP

[northwestsnow]

Just a quickie.

BA is right- this Low pressure movement around the azores will not be entirely resolved yet.

00Z runs tomorrow will be important.

 

[Purga]

Interesting where this run is going to!

Quite a bit different isn't it,,,,

[northwestsnow]

1 minute ago, Purga said:

Interesting where this run is going to!

Quite a bit different isn't it,,,,

Its going welll.... for coldies!!

Cmon UKMO, you know you want to !! Im doing an all nighter!!! 

Edited December 30, 2016 by northwestsnow

[Nick F]

Despite the differences in the microscale re: the position of the Atlantic high towards the end of the week/next weekend when the flow re-amplifies,which is causing much angst, in the broadscale its interesting to see how persistent the N Pacific and N Atlantic ridges are in the means from now right through to day 15. This persistence of the ridges and the anticyclonic wave breaking could impact the upper strat too, the 12z EC day 10 strat forecast for 10 hPa suggests a sPV split by wave 2. Already the N Pac and Atlantic ridges are apparent in strat forecast lower down at 150 hPa.

With regards to the N Pacific/ E Asia area of interest where the changes appear to have originated, there is a weak La Nina / low AAM base state. Indeed, the most recent NOAA Climate Prediction Centre ENSO analysis (26th Dec) indicated La Nina conditions are present, with negative sea surface temperature (SST) anomalies present across most of the central and eastern equatorial Pacific.

Despite the weak La Nina / low AAM base state, atmospheric wave breaking off the eastern Asian continent combined with wave propagation from anomalous tropical convection over the Pacific, as depicted by an MJO wave progressing eastwards on vertical velocity (CHI-200hPa) charts (albeit depicted at low frequency on RMM charts) – is likely behind developing a strong ridge northwards in the dateline area over Alaska and far west of Canada. This in turn amplifies the flow downstream over N America (deep trough) and the north Atlantic (ridge) and Europe (deep trough). Such a wavy configuration of course creates cold arctic air to surge south into the troughs (N America and Europe).

The position of these troughs and ridges to me that looks showing little signs of shifting to at least mid-month and perhaps well beyond looking at the extend EPS and GEFS. So don't get too worked up because the second northerly fails on the 12z, because eventually things may work in our favour and we strike lucky at the surface over the next 15 days which show little signs of budging in the upper levels.

Edited December 30, 2016 by Nick F

[mulzy]

3 minutes ago, northwestsnow said:

Just a quickie.

BA is right- this Low pressure movement around the azores will not be entirely resolved yet.

00Z runs tomorrow will be important.

 

Where have I heard that before?

Edited December 30, 2016 by mulzy

[Ali1977]

Slightly better application of the Alaskan heights too, this may help weaken PV a tiny bit more which could allow an increase in WAAs northward projection further down the line. 

[Met4Cast]

Massive differences between the 12z and 18z, tonights 18z seems to be backtracking back to where we want things to go. The ensemble scatter is massive beyond the 6th so it's not worth worrying about what happens beyond that. Crucial time is between & T132. If we can keep the two lows beneath the high from phasing together, we'll keep the amplification and get the second blow Northerly. 

Those two low pressure systems are key. UKMO has been phasing them and the later output isn't as good. No phasing on the 18z, it's heading for a good run. Until this is resolved, anything that happens beyond that is pure speculation.

[Ali1977]

Next weekends rapid cool down is back - happy with that. 

[Allseasons-Si]

This is a much better run,more height's  southern tip of Greenland forcing more WAA up there,net result ,forcing more CAA south

18z at 138hrs on the left and 12z at 144 on the right

 

[Iceberg]

Well 18z has gone from southerlies. Back to cold nw and then northerlies. We've seen this before where the models suddenly over react to a signal only the cancel out the reaction again over the next few runs. 

Not saying yet that this is happening but it's possible 

[Seasonality]

Talk about inter run variability. Chalk and cheese.

[blizzard81]

2 hours ago, Nouska said:

It is a tropical cyclone genesis view - NOAA and NHC don't focus on beasts from the east when hurricane forecasting, their interests are focused on ocean beasts.

Hurricane season is over. It is now beasterly season so their focus needs to shift east

[Banbury]

Just now, Seasonality said:

Talk about inter run variability. Chalk and cheese.

Indeed , wise to bring FI down to 96-120 id say

[Hotspur62]

Still not convinced by GFS,swinging too wildy from run to run.History tells me that UKMO will be on the money for next week and i still think we will see a Scandi/Icelandic High develop as opposed to a GH. Only imho and if i knew how to post charts i would but my PC skills are C--P i am afraid as not very techno minded.

[Allseasons-Si]

Well i can not believe it,we get the northerly but the height's are not as good as the 12z at 180,though still happy in the short term.

[Cheshire Freeze]

Just now, Allseasons-si said:

Well i can not believe it,we get the northerly but the height's are not as good as the 12z at 180,though still happy in the short term.

So after all that, we may end up with a UK high anyway 

This island is cursed I tell thee

[IDO]

At D7 more uncertainty of phasing with height rises and the Azores trough. On this run a wave from the SE cuts the flow and we get an Azores cut off low with two sources of WAA building the Atlantic High:

A cold northerly on this run; D8:

Looks very complicated with all sorts of different scenarios within the unfolding pattern and that is not counting the D4 shenanigans that remain unresolved despite this flip-flop!

Edited December 30, 2016 by IDO

[Nouska]

7 minutes ago, Iceberg said:

Well 18z has gone from southerlies. Back to cold nw and then northerlies. We've seen this before where the models suddenly over react to a signal only the cancel out the reaction again over the next few runs. 

Not saying yet that this is happening but it's possible 

The more detailed ensemble mean on from the EPS also show the northerly next weekend is not off the menu just yet.

MSLP   T850

The people with access to Weatherbell might have more info but it all looks pretty cold right out to 360 hours on the latest run.

[SMU]

Ignoring the 18z which is a standard topper - the overall day has been a step back & step away from the potential displayed yesterday, our best case is a delay in the cold > reload cold to very cold scenario -the worse case is cold to mild to continued mild ( via a vee UKMO ) 

lets hope tomorrow lands on a more positive perspective.... however the trend from 12z UKMO & 18z GFS is to increase the jet speed across the Atlantic in the 144-168 arena forcing any block into submission- that's not a good sign...

Edited December 30, 2016 by Steve Murr

[Mucka]

4 minutes ago, Hotspur61 said:

Still not convinced by GFS,swinging too wildy from run to run.History tells me that UKMO will be on the money for next week and i still think we will see a Scandi/Icelandic High develop as opposed to a GH. Only imho and if i knew how to post charts i would but my PC skills are C--P i am afraid as not very techno minded.

Just right click on the image you want. Then left click "copy image address" from the drop down menu and then right click in your post and from the drop down menu selct paste and you wills ee the link appear and magically transform into an image when you post.

 

Sorry admin, should of PM'd

Edited December 30, 2016 by Mucka

[radiohead]

By the end of next weekend, the 18Z GFS gives a dusting of snow to a lot of low lying areas, with higher ground obviously getting a bit more.

 

[stewfox]

2 minutes ago, Mucka said:

Just right click on the image you want. Then left click "copy image address" from the drop down menu and then right click in your post and from the drop down menu selct paste and you wills ee the link appear and magically transform into an image when you post.

 

Sorry admin, should of PM'd

I did it a long way around ,thanks 2nd northerly back on

GFS 18z

GFS 12Z

 

[Mucka]

1 minute ago, Steve Murr said:

Ignoring the 18z which is a standard topper - the overall day has been a step back & step away from the potential displayed yesterday, our best case is a delay in the cold > reload cold to very cold scenario -the worse case is cold to mild to continued mild ( via a vee UKMO ) 

lets hope tomorrow lands on a more positive perspective....

Not sure that is nailed on as the case yet Steve. If we had seen a better upstream we would have got at least some trough disruption and more amplifed pattern as seen previously or even some undercut and the holy grail charts reappear.

Could well be that upstream is faster and flatter but I would rather get that Northerly and take my chances from there than just hope things fall our way in deep FI.

[Cheshire Freeze]

Well, if we still somehow get an E'ly from here I really will start to think that is the ultimate destination