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

[Man With Beard]

EC46 fun time again ... really keen on the Scandi height anomaly tonight and has finally given up on the Canadian one - takes until week 4 to get uppers below average though. It's all just for fun though folks.

 

[SMU]

Im surprised by the lack of posts ! the models are moving closer to something special , for here that may be a 2 week coldspell as this week the SE CET will be about 0c

The 18z are known for their resolution however lets see what they can drag out the fire...

[bluearmy]

1 minute ago, Steve Murr said:

Im surprised by the lack of posts ! the models are moving closer to something special , for here that may be a 2 week coldspell as this week the SE CET will be about 0c

The 18z are known for their resolution however lets see what they can drag out the fire...

'As I said earlier steve - all bets are off for the time being. The gfsp 12z dribbling out and getting to the first disruption point. Not sure if you saw the 18z para from yesterday . Definitely worth checking out the archive version! 

[Zakos]

9 minutes ago, Steve Murr said:

Im surprised by the lack of posts ! the models are moving closer to something special , for here that may be a 2 week coldspell as this week the SE CET will be about 0c

The 18z are known for their resolution however lets see what they can drag out the fire...

Me too!

We are pretty close to a snowfest on the 18Z GFS

Very far out obviously, but both ECM and GFS have been toying with heights to the NE for a while now

both ECM and GFS anomaly at 144 screams "battleground " to me

We can only hope the block is as stubborn to remain here as it was over the UK.

Edited January 19, 2017 by Zakos

[SMU]

19 minutes ago, bluearmy said:

'As I said earlier steve - all bets are off for the time being. The gfsp 12z dribbling out and getting to the first disruption point. Not sure if you saw the 18z para from yesterday . Definitely worth checking out the archive version! 

Yeah 18z(p) nice yesterday nice

12(p) nice @ 168 not bad but all GFS runs moving in the right direction- we just need a bit more amplification in the atlantic at 168 with the low exiting the states - more of a horsehoe shape will see lower heights sliding under the block but also sharpening the angle of the deep cold out to the east...

Edited January 19, 2017 by Steve Murr

[Ice Day]

6 minutes ago, Steve Murr said:

Im surprised by the lack of posts ! the models are moving closer to something special , for here that may be a 2 week coldspell as this week the SE CET will be about 0c

The 18z are known for their resolution however lets see what they can drag out the fire...

I think after 7 weeks of viewing every run, mid winter fatigue has set in for many members. However, if the upgrades continue tomorrow they'll all be flocking back.  This chart at 210 is getting closer to something special.....and not far from a 1991 chart!

!  

Feels like something is brewing, but I've had that feeling a few times this winter to no avail. Maybe, just maybe.......

 

 

[booferking]

6 minutes ago, Steve Murr said:

Im surprised by the lack of posts ! the models are moving closer to something special , for here that may be a 2 week coldspell as this week the SE CET will be about 0c

The 18z are known for their resolution however lets see what they can drag out the fire...

There not much excitment over in Ireland after the failed northerly steve been cloudy for the last week i think a lot have giving up on so many false dawns. 

It would need to be something special to turn this winter around.

[Pembroke Dangler]

This has got January 2013 written all over it in that the trough will have nowhere to go but under and a snow event will take place over southern Britain. The models can't work it out this far out so they revert to climatology and try to force the block away to easily. But could the Atlantic win? It's knife edge stuff but intriguing never the less.

[Trom]

1 hour ago, Steve Murr said:

So once again another full day of moves towards a 'continental solution' I think for the time being that should be the phrase as opposed to 'Easterlies' as theres a general perception that Easterlies are going to be action packed bitter cold winds bringing snow-

In order to remove the emotion the 'continental solution' should stoke us up enough to believe there maybe enough in the tanks to get to easterly, however we have to move the dial to get there.

As per the update last night the models are 'generally' in a state of catch up at the moment, which for me signifies the point along the timeline in the suites where patterns can be changed with repercussions more especially for the UK, ive tried to highlight before generally at 144 - 192 the models especially the euros have a grip on the longwave pattern & are starting to develop the shortwave ones- well today I think that arena is -24-36 hours so the longwave resolution is sitting around 108-156 & shortwave accuracy sub 120-

As a result, the refinements that each runs are making are a huge difference for the surface temps over the UK, the means over the last 48-72 hours have been woeful, so much so that this is the difference between day 5 & day 9 just days before - I cant get the mean now however the Op was fairly reflective -

Anyone forecasting via 'means' needs to really ask what the point is as every single time there is model change @120-144 the means will be hopeless...

The crucial timeframe for 'upgrades' to any wintry potential via the battle of West meets the ' continental flow' ideally will come from the 138-168 timezone with more energy diving south & a more amplified high- I think the models have overcooked the northern jet & as seen over many days this week will continue to move favourably over the forthcoming runs-

More on the SSW later -

S

PS I think the ECM day 10 pattern is great about 1000 miles east of us with significant troughing, expect that to move west over the next few Op runs 

 

This goes back to the point I've made a few times on here, that mean without some kind of dispersion measure is an odd way to describe a data set.  I know of no other field of study other than this website that mentions one without the other.  It's just bizarre  to describe distributions without a volatility measure.

But of course if runs tightly cluster around a mean it tells us that there is a trend.  By their very definition mean charts wont be able to sniff out a model change (as the positive and negative deviations will cancel out to some extent), but when the standard deviation of ensembles increases it tells you that there is greater uncertainty and hence the mean becomes less significant relative to volatility as the important measure.  Of course when the standard deviation of runs is low relative to the mean then it becomes useful.  

I'm not having a go at any individual posters but really think that if you are going to post a mean then you need to post the ensembles so give it some kind of context, so that forum users can glean whether they are looking a significant trend or just a sign of uncertainty - both useful to know when interpreting the models.  Observing frequencies of particular outcomes can also be useful to determine implied probabilities in the forecast data so get looking for clusters.  

Edited January 19, 2017 by Trom

[SMU]

^ I only use the mean for one purpose to compare the 120 v 126 or the 138 v 144 - All Im ever interested in is the trending because within all that data if the ops are trending like they are now towards amplification then the means will 'nudge' that way- they are often 24-36 hours behind the complete turn around because there is always 'stragglers' that really miss a pattern muting the signal 'as you say' -

This is especially important with the GFS as they always display the 'same old story' every time theres a developing cold spell ... Always a day late & a dollar short..

[Nick F]

35 minutes ago, Steve Murr said:

Im surprised by the lack of posts ! the models are moving closer to something special , for here that may be a 2 week coldspell as this week the SE CET will be about 0c

The 18z are known for their resolution however lets see what they can drag out the fire...

I think many have been put off by the growing advance of the Atlantic trough into western Europe over recent runs, which is fair enough. But what I see is an increasing trend for Atlantic trough disruption against the blocking to the east over Scandi/E Europe and western Russia. Certainly evident from the ECM high res and EPS and also hints in the 18z GFS too.

Longer term, as we head into beginning of February, as well as the mean Atlantic trough not really advancing much past the meridian, there are hints from GEFS/EPS on recent runs of the block to the east building north over Scandi and further toward the pole, even a EPO/Scandi 'ridge bridge' - which would force the trop PV south from the pole as the -AO develops. Hence a more southerly track jet advertised by EPS in the extended.

This is without knowing the potential impacts of the wave 1 warming on the strat and the PV displacement forecast. Should the PV get displaced to E Europe/W Russia, it is not quite certain where the trop PV will be displaced. I have read today that it may get displaced to eastern Canada - which is not all bad - as it may re-inforce the Scandi block.

Edited January 19, 2017 by Nick F

[bobbydog]

23 minutes ago, Steve Murr said:

Im surprised by the lack of posts ! the models are moving closer to something special , for here that may be a 2 week coldspell as this week the SE CET will be about 0c

The 18z are known for their resolution however lets see what they can drag out the fire...

Battle fatigue steve. The models have been moving closer to something special for weeks. However this time we might have reinforcements....

[weirpig]

something may be brewing 

[Tim Goffer]

1 hour ago, Steve Murr said:

18z out to 114 has a direct Easterly flow over England & lower heights which again supports building a cold pool over the UK in situ- 

The theta E charts the continental air growing in 'depth' again & heading downwards as opposed to the 12z

18 v 12

Can we handle another easterly chase?? 

Ah go on then! 

[Zakos]

ECM mean anomaly for the 25th over the last 5 days. I do believe means can be useful to spot possible trends, but really are meaningless, in terms of forecasting UK weather, beyond 192.I think some people believe that the ensemble spread represents probability of cold/mild.

For example. If the GFS ensembles have 90% of the members showing south westerlies, this would mean roughly a 90% chance of mild weather.Beyond day 5 or so -  this is simply not true. The ensembles will almost always follow the operational.

Others may feel we have been let down several times and that this is just another march up the garden path. 

The reason models "default" to zonality, is because this is always the most likely scenario for the UK in winter.

That doesnt mean we cant see cold or snow. Were always odds against for significant cold here in the UK.  But just because a horse is 8/1 to win the race, doesnt mean you wouldn't watch the race if you'd bet on it .

But isnt that what this thread is essentially about in the winter? the chase for cold. Its always odds against... but that doesnt mean it cant happen. That said I am considering spending next winter in northern siberia if I dont see a decent cold spell soon.

 

Edited January 19, 2017 by Zakos

[Man With Beard]

21 minutes ago, Steve Murr said:

^ I only use the mean for one purpose to compare the 120 v 126 or the 138 v 144 - All Im ever interested in is the trending because within all that data if the ops are trending like they are now towards amplification then the means will 'nudge' that way- they are often 24-36 hours behind the complete turn around because there is always 'stragglers' that really miss a pattern muting the signal 'as you say' -

This is especially important with the GFS as they always display the 'same old story' every time theres a developing cold spell ... Always a day late & a dollar short..

Steve the ECM mean in particular floored the ECM op when it came to the easterly last week - but it's times like these when I feel the ops will lead, when there is a serious chance of a tipping point.

I still think there just about isn't enough in the tank though. There always appears just a little bit more in the northern jet at the last minute. But maybe on the next attempt??

[SMU]

29 minutes ago, Nick F said:

I think many have been put off by the growing advance of the Atlantic trough into western Europe over recent runs, which is fair enough. But what I see is an increasing trend for Atlantic trough disruption against the blocking to the east over Scandi/E Europe and western Russia. Certainly evident from the ECM high res and EPS and also hints in the 18z GFS too.

Longer term, as we head into beginning of February, as well as the mean Atlantic trough not really advancing much past the meridian, there are hints from GEFS/EPS on recent runs of the block to the east building north over Scandi and further toward the pole, even a EPO/Scandi 'ridge bridge' - which would force the trop PV south from the pole as the -AO develops. Hence a more southerly track jet advertised by EPS in the extended.

This is without knowing the potential impacts of the wave 1 warming on the strat and the PV displacement forecast. Should the PV get displaced to E Europe/W Russia, it is not quite certain where the trop PV will be displaced. I have read today that it may get displaced to eastern Canada - which is not all bad - as it may re-inforce the Scandi block.

Yes & if you look at the 18z ENS - any of them that have a decent enough disruption at 144 dropping heights SE lead to a very stagnent cold pattern at 240 with heights building to the NE- & this is the tip of the iceberg really-

if we look at ECM 168 V GFSop / GFSens 168 the GFS is smooth & with the windflow  where as ECM creates that acute pattern of undercutting - watch the 00z start to develop more acute angles along 144-168 as the resolution improves ...

[Seasonality]

43 minutes ago, Steve Murr said:

Im surprised by the lack of posts ! the models are moving closer to something special , for here that may be a 2 week coldspell as this week the SE CET will be about 0c

The 18z are known for their resolution however lets see what they can drag out the fire...

Hi Steve. There have been a few of us discussing an evolution to something special. Glad to see you back with your valued contribution. Look at that intense cold that could march west. Staying cold over Europe too might I add.

[Panayiotis]

It would probably be better to have a side-by-side of the mean, and the uncertainty at a particular time if there are posts using ensemble data. Example at 180hrs from 18z GEFS:

There is clearly more uncertainty of pressure over SW UK, and less so to the W of Newfoundland, and N of Norway. This highlights the fact, in this case, that there are some members of the GEFS, that make more of an undercut proposed by the low pressure to the SW of the UK. This therefore has implications on the northern extent of the heights over northern Norway, where an undercut would mean higher pressure over this region. 

This is just an example where a reader can deduce a bit more from just the ensemble mean and come to the conclusion that it shouldnt be taken literally. 

Edited January 19, 2017 by Panayiotis

[snowflakey]

Good to see something of interest after a zonal spell was mentioned. Still some way to go before everything falls into place, let's hope this time it materialises. Like others have mention we need a lot more energy going south under the block, hopefully tomorrow things will be a bit clearer.

[Man With Beard]

UKMO T144 ... we nearly have a closed high, Atlantic stalling...

[mb018538]

Atlantic delayed by another day on todays UKMO run....at 144 hours we still have high pressure holding on!

[winterof79]

GEFS throwing out some medium/high level blocking solutions

Undercut coming to a place near you soon.......

Loving 12

 

Edited January 20, 2017 by winterof79

[Great Plum]

The ecm 144hr chart has also stalled the Atlantic...

[That ECM]

Just when you think you are getting a handle on what the models are showing and what the outcome would be you then read posts from people I respect on here and you think jeez what am I missing. I can see the Atlantic stalling but I can't see it going under. All I see is this high gradually being pushed east and us being more influenced by the low coming from the west. I am not trying to be clever or disagreeing to wind up, it just what I see. Happy for someone to show me what I am missing.