Model output discussion - into 2018

[Daniel*]

43 minutes ago, Jason M said:

ECM is a decent easterly. Maybe a 6.5 or 7 out of 10. If it verified I'd imagine there would be some snow in favored spots in the south and east given that pressure is not too high and uppers are -7c or thereabouts at their peak. Given continental air mass and time of year, daytime temps of around zero plus or minus a couples of degrees.

 

You’re a harsh marker I’ll give it a 7.5 / 8 out of 10. Let’s not kid ourselves we haven’t seen anything alike since 2013 I would happily take it the uppers are colder than that. That would allow convection.

[SMU]

Evening All

Many many pages on here today driven on at a frantic pace -

FWIW here’s my analyis-

The evolution from mild to cold is pretty much set now all be it with still minor resolution on whether the first batch of cold makes it to the far south at the first attempt - There’s a slight concern that the full deep cold ( sub -6c polar air ) may not make it - before its started to get mixed with the continental air- seen here

It’s not to much to worry about as the continental air will be cold - just not mega cold initially- there is reasonable continuity from the models around this but post 120 they part company.

Post that we have to heavily rely on historic performance in this scenario. For me that stems back of about 13 years - & there is always a couple of consistent themes.

* ECM / ECM operational usually leads the mean but the mean is usually catching the OP up the day after - The mean is also less volatile. 

* GFS is without fail awful in ANY scenario relating to undercutting - so many people have short memories of just how bad it is - *** in particular 06z & 18z ensembles *** the GFS / GEFS will be up to 3 DAYS behind the ECMs correct solution.

* GEM / JMA - are usually a lottery.

* UKMO usually close to the ECM.

 

I think personally we are on the cusp of a classic cold spell in terms of 500MB height appearance - 

The ECM 144 & 168 would certainly not look out of place in the archives

Whats not quite as classical is the upper air temps, we don’t get the full -10c uppers from the East- so convective snow ( at the moment ) looks a bit limited to more granular flurries.

Surface temps will however be very cold circa 0-2c.

Based on the ECM the best opportunity for proper convective snow is day 6 into 7.

Post 7 onwards - undercutting YES.....

Forecast summery:

GFS - will correct throughout Weds- GEFS will correct Weds- Thurs however the meeting point to the ECM may not be all the way to ECM there may be a 70/30 meeting point where the ECM / GEM blend  backtracks slightly.

^^^^ This is more towards the undercutting - don’t waste your emotions or time on your the GFS... The caveat to that is the ensembles will transition towards the expected scenario but it will be jagged & slow with some suites better than others.

The distribution of energy into the Northern arm is expected to gradually be modelled back south.

EXPECT THE UNDECUT....

Best

steve

[Snowman.]

14 minutes ago, Man With Beard said:

Is anyone getting a sense of dejavu with last January?? The ECM op was adamant on an easterly for days - the ECM mean had a source of easterly but never actually took blocking above our latitude - and the op eventually moved towards the mean and further:

here's the op runs from that period:

        

And here's the mean runs (note the difference at the top of Scandinavia):

        

Will be interesting to follow this time! So far...

     

vs

        

I think we can already see two different trends appearing!

 

Lack of low heights to the S/SE last year was what led to our demise. This year is different jet has had no problem heading south so can things go right for once?

[Dennis]

i like this setting 

[SMU]

Just to add to my post I hadn’t seen the ECM 216

convective potential high & getting higher 168-216...

[Allseasons-Si]

9 minutes ago, Steve Murr said:

EXPECT THE UNDECUT....

Best

steve

We all expect the the undercut Steve but will it happen?

looking at the 6-10 day from NOAA i posted ^ does show it though

[fromey]

  I may  have a missed it in the loads of posts since the ECM but has there been a post from NOAA, I think nick normally puts them up, just wondering how they see the models doing especially with the storm they have coming up the east coast as I believe it has a knock on effects for us 

cheers

fromey

[blizzard81]

32 minutes ago, Man With Beard said:

Is anyone getting a sense of dejavu with last January?? The ECM op was adamant on an easterly for days - the ECM mean had a source of easterly but never actually took blocking above our latitude - and the op eventually moved towards the mean and further:

here's the op runs from that period:

        

And here's the mean runs (note the difference at the top of Scandinavia):

        

Will be interesting to follow this time! So far...

     

vs

        

I think we can already see two different trends appearing!

 

What a top post. Post of the day imo. This illustrates my post earlier with regards to the ecm ops maybe underestimating the northern arm. It also helps to temper expectations. 

[A.J]

until the SHAKY model suite throws up a 10 exclamation marks out of ten in one post, then I'm not convinced.....The very fact an earlier post only showed 6 out of 10 should set alarm bells ringing....ignore at your peril 

[SMU]

4 minutes ago, Allseasons-si said:

We all expect the the undercut Steve but will it happen?

looking at the 6-10 day from NOAA i posted ^ does show it though

Yes modified to the ECM - GFS not even in the mix.

There will be a point in the next 24 hours where the GFS operational suddenly wakes up-

probs 12z tomorrow but 18z may start the ball rolling-

[snowice]

2 minutes ago, ajpoolshark said:

until the SHAKY model suite throws up a 10 exclamation marks out of ten in one post, then I'm not convinced.....The very fact an earlier post only showed 6 out of 10 should set alarm bells ringing....ignore at your peril 

 

!!!!!!!!!! There you go 10

[shaky]

7 minutes ago, ajpoolshark said:

until the SHAKY model suite throws up a 10 exclamation marks out of ten in one post, then I'm not convinced.....The very fact an earlier post only showed 6 out of 10 should set alarm bells ringing....ignore at your peril 

Well lets start with the 18z then buddy!!hope for a better run!!here goes!!!

[johnholmes]

16 minutes ago, Allseasons-si said:

We all expect the the undercut Steve but will it happen?

looking at the 6-10 day from NOAA i posted ^ does show it though

Where on earth do you get that idea from if I may ask, please?

[shaky]

First things first get the low pressure across the uk less deep at 72 hours!!

[mulzy]

Already significant changes at 48 hrs on the GFS 18z!!!

[shaky]

5 minutes ago, mulzy said:

Already significant changes at 48 hrs on the GFS 18z!!!

For the better?

[Ice Day]

GFS 18z at 66 vs 72 of ECM.  Looking like a move to the Euro to me?

GFS   ECM  

[shaky]

6 minutes ago, Ice Day said:

GFS 18z at 66 vs 72 of ECM.  Looking like a move to the Euro to me?

GFS   ECM  

Wow!!!!massive changes and i assume for the better!!how the heck was it so wrong at such a time frame!makes me laugh sometimes!!hmm nothing from steve murr yet!!making me nervous!!

Edited January 2, 2018 by shaky

[Allseasons-Si]

3 minutes ago, johnholmes said:

Where on earth do you get that idea from if I may ask, please?

To my untrained eye,it looks like -ve heights disrupting SE into Europe,it does look like an undercut to me.

if i am wrong then i stand corrected

[Dennis]

1 minute ago, Allseasons-si said:

To my untrained eye,it looks like -ve heights disrupting SE into Europe,it does look like an undercut to me.

if i am wrong then i stand corrected

yes that right

[Wilxy]

heights are not as far north unless i'm blind! haha

[feb1991blizzard]

The 6-10 day chart - you cant really tell because its a mean chart, but any mean of 5 days that has a scandi high and any kind of dig on Atlantic troughing surely could possibly contain an undercut?

[That ECM]

3 minutes ago, tomjwlx said:

heights are not as far north unless i'm blind! haha

It's slower rather than lower. The key time has yet to come out, we are looking for most of the energy to go under as opposed to over.

[danthetan]

5 minutes ago, Allseasons-si said:

To my untrained eye,it looks like -ve heights disrupting SE into Europe,it does look like an undercut to me.

if i am wrong then i stand corrected

I think what John is getting at is the green lines indicate the flow and the blue and red indicate anomaly heights. 

[johnholmes]

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Posted 2 minutes ago

  4 minutes ago, Allseasons-si said:

To my untrained eye,it looks like -ve heights disrupting SE into Europe,it does look like an undercut to me.

if i am wrong then i stand corrected

yes that right

sorry but that is not right, as posted above it is a mean chart and having studied these charts for almost 10 years daily I would not think of suggesting that.

Take a look, from another angle, at how the 12z GFS deals with what you suggest would be an undercut, it does not, IF the run turns out to be near the mark, the surface feature is turned roughly north. It may well be wrong in which case back to the drawing board. It MIGHT happen but it is too far to suggest it will in my view.

Also remember the green lines are contour lines at 500 mb.

 

Edited January 2, 2018 by johnholmes