Model output discussion - 1st December onwards

[forecaster]

13 minutes ago, s4lancia said:

As others have quite rightly said, the Ens as a whole are as prone to flipping as the op, which naturally somewhat negates their usefulness! 

 

There's no solid evidence to back up such opinions.

 

You need to be careful with netweather forum folklore. Not specific to NW of course; it's a human trait. 

 

http://journals.ametsoc.org/doi/abs/10.1175/2009MWR2960.1

 

One thing the EC always try to drum home is that model jumpiness does not correlate to accuracy. That's important but doesn't make our job muchy easier.

Edited December 25, 2015 by forecaster

[Duane S.]

11 minutes ago, forecaster said:

 

There's no solid evidence to back up such opinions.

 

You need to be careful with netweather forum folklore. Not specific to NW of course; it's a human trait. 

 

http://journals.ametsoc.org/doi/abs/10.1175/2009MWR2960.1

 

One thing the EC always try to drum home is that model jumpiness does not correlate to accuracy. That's important but doesn't make our job muchy easier.

Good grief, it's hardly 'folklore', I have seen it with my own eyes on countless occasions. Your previous comment that probably 100-200 members are ideally required speaks volumes...

Happy Christmas to everyone! 

[forecaster]

Just now, s4lancia said:

Good grief, it's hardly 'folklore', I have seen it with my own eyes on countless occasions. Your previous comment that probably 100-200 members are ideally required speaks volumes...

Happy Christmas to everyone! 

 

That's called "confirmation bias". Ensembles aren't perfect and they are underdispersive. That's what you  need 100-200 members for. They are NOT "as prone to flipping as the op". Science backs this up. 

[swilliam]

33 minutes ago, forecaster said:

 

That's called "confirmation bias". Ensembles aren't perfect and they are underdispersive. That's what you  need 100-200 members for. They are NOT "as prone to flipping as the op". Science backs this up. 

Ensembles and their means are averages so as you say are not prone to swings. They are extremely useful if the weather turns out to be near average as of course it often does. However when the weather deviates far from average then ensembles are well pretty average at predicting this. This has been highlighted IMO by this month which has been exceptional by any standards. However I do not recall any extended products predicting this level of extreme temperature excursion. Extended range forecasting based on ensembles is good at saying it will be a bit colder/warmer wetter/drier etc but in terms of predicting significant deviations from this are currently fairly poor. So if you are looking for any kind of significant deviation from the norm the ensembles IMO are not that helpful - only in identifying trends. I tend to use them as many do on here as to what the possibilities are going forward are rather than what they are showing as a mean as that is nearly always not far from average (or the default zonal set up). The current situation is a good example of this. There is clearly potential; for a significantly colder/drier spell but based on ensembles you would not state this publicly in forecast  (if that is what you do professionally).  Hence the current forecast from Meto but to most people what is stated means there will not be any significantly colder weather in the next month. So if it transpires that there is then this will be a busted forecast as far as most people are concerned.

On a separate note as  a physical scientist in another field it seems strange to me that modelling is done by feeding in what is effectively adjusted (or duff) data and seeing what the result would be (i.e. the ensembles) and then take an average as prediction.

 

 

Edited December 25, 2015 by swilliam
Added something else

[bobbydog]

16 minutes ago, forecaster said:

 

That's called "confirmation bias". Ensembles aren't perfect and they are underdispersive. That's what you  need 100-200 members for. They are NOT "as prone to flipping as the op". Science backs this up. 

so the models might be wrong.

they might be... but they might be right.... its now christmas day. i've just got to bed after a hectic day and putting all the kids presents under the tree (and half way across the room!) as its christmas, at least let us believe there is a chance of seeing the elusive wonder that is snow. it brings the kid out in us all. science could prove to our kids that Santa doesnt exist but we wouldnt tell them. why ruin the magic just because we can? 

science cant prove however, that it wont snow in a couple of weeks time. lets just enjoy the fact that it might.

merry christmas to you and everyone on netweather (and here's to a snowy new year!)

[Duane S.]

54 minutes ago, forecaster said:

 

That's called "confirmation bias". Ensembles aren't perfect and they are underdispersive. That's what you  need 100-200 members for. They are NOT "as prone to flipping as the op". Science backs this up. 

Thanks, I am familiar with confirmation bias. I can't argue that the fact that the mean of the ENS suite fluxuates to the same degree as Op runs do, of course not, but (perhaps poorly) the point I was trying to make is that on numerous occasions the ensembles have proved as useful as a chocolate fireguard, predominately clustered (with or without the Op) for days on end only for them to switch, job lot, overnight and point to a completely different scenario. 

Don't get me wrong, when looking out for the next cold spell I always take in the Ens data, they very much have their place but I would take op + control over the ens every day of the week. By which I mean if the op and control show one thing and the main Ens cluster another, I know where my money is going.

Edited December 25, 2015 by s4lancia

[Cheshire Freeze]

UKMO looks to be on board this morning.....

No Atlantic steam roller there...

GFS 180 hrs....

Very, very close

204 hrs we have trough disruption and cold pool backing West

 

Edited December 25, 2015 by CreweCold

[Swave Snow]

Merry Christmas. 

[radiohead]

Whatever about cold potential further down the line, look at what is creeping into the reliable time-frame now.

 

[knocker]

As expected not looking brilliant vis rainfall for the NW in the next 48hrs. Impossible to be exact regarding rainfall amounts but they could well exceed this in some areas.

Edited December 25, 2015 by knocker

[knocker]

6 hours ago, bluearmy said:

Incidentally, the very end of the ec32 manages to bring a Scandi trough.  The parallel ec46 is fairly tedious from a coldies perspective. 

 

Regarding the latter a tweet from Ryan Maue "Recently, ECMWF upgraded from 32 to 46 days based on justification of MJO phase/evolution skill"

I have to say I had a feeling of deja vu looking at the anomaly for Feb 1st-8th.

[Polar Maritime]

This mornings GFS continues to show a cool down of sorts into the new year as the Jet slowly drops South as blocking takes hold slowing the Atlantic. And again towards the end of the run its showing some form of cold Easterly. Very interesting model watching over the Christmas period as they continue to toy with background signals.

 

Edited December 25, 2015 by Polar Maritime

[Captain Shortwave]

At this point, it does seem like we will see an area of high pressure form over Scandinavia, but as of yet it is highly likely that the battleground will occur somewhere over central Europe.

GEFs

 

Moving on and to be honest the GEFs keep that high pretty much in the same spot until the end of the extended range.

 

I would put a cold spell around the turn of the year as a low possibility, but there is scope for a second or third chance from this pattern if further areas of cold air are chucked underneath the high, this along with chances for the high to back westwards to influence the UK more robustly.

Merry Christmas everyone and it does look like we might be turning a corner in terms of where our weather is going.

Edited December 25, 2015 by Captain Shortwave

[knocker]

There is nothing in the GEFS anomalies this morning to suggest any imminent change to the weather pattern effecting the UK. There are changes upstream where the trough digging down the eastern side of N. America is removed but this was forecast to be a temporary affair. It continues to push the Russian and Alaskan HP polewards but it's on it's own with this at the moment and in any case the implications are unclear.

So generally speaking the UK remains in a westerly regime with periods of wet and windy weather with temps remaining just above average but obviously this will vary latitudinally and with the passage of low pressure systems which could produce snow on the hills up north.

As a side note I listened to the natural history programme on R4 this morning and it included a poem by Wordsworth. You'll never guess the poem.

Edited December 25, 2015 by knocker

[East_England_Stormchaser91]

Have to agree with Captain Shortwave here. Eastern Europe is certainly looking like it's going to be slammed into the freezer sooner rather than later. This is the key to get some teeth into the possible beasterly later on! 

[tinybill]

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

 

plenty  of scope fantasy world is pretty grim  looking for the uk at the  moment could large scale flooding problems  well in to the new  year

[snowice]

Well well well

[northwestsnow]

At last we have some interest !! Plenty of room for upgrades over the coming days and the euros have been playing catch up with GFS.

Scandy High looking a good punt and all bets are off medium term, the cold pool to the east on GFS looks brutal - majorpattern change coming for Europe in the new year and hopefully something more seasonal for the UK..

[phil nw.]

ECM still not on board wrt the easterly this morning and until it is i would remain cautious.

There is certainly signs though that changes to undermine the strength of the pv are underway with a pincer movement of warm air on both sides of the hemisphere so understandably the GFS evolution is quite possible at some point in January.

I said the other day i have seen these easterly teases before and sometimes any success may need more than one attempt for the pattern to retrogress.Some exciting charts to come i think.

Happy Christmas to everyone,have a great day.

[northwestsnow]

3 minutes ago, phil nw. said:

ECM still not on board wrt the easterly this morning and until it is i would remain cautious.

There is certainly signs though that changes to undermine the strength of the pv are underway with a pincer movement of warm air on both sides of the hemisphere so understandably the GFS evolution is quite possible at some point in January.

I said the other day i have seen these easterly teases before and sometimes any success may need more than one attempt for the pattern to retrogress.Some exciting charts to come i think.

Happy Christmas to everyone,have a great day.

Merry christmas phil, looking like a big swing towards GFS from euro models  this morning

Edited December 25, 2015 by northwestsnow

[John Badrick]

32 minutes ago, knocker said:

There is nothing in the GEFS anomalies this morning to suggest any imminent change to the weather pattern effecting the UK. There are changes upstream where the trough digging down the eastern side of N. America is removed but this was forecast to be a temporary affair. It continues to push the Russian and Alaskan HP polewards but it's on it's own with this at the moment and in any case the implications are unclear.

So generally speaking the UK remains in a westerly regime with periods of wet and windy weather with temps remaining just above average but obviously this will vary latitudinally and with the passage of low pressure systems which could produce snow on the hills up north.

As a side note I listened to the natural history programme on R4 this morning and it included a poem by Wordsworth. You'll never guess the poem.

Not- I Wandered Lonely As A Cloud because I think that has no relation to the weather we will experience for a while yet. A whirl-Blast from behind the Hill is more apt for the weather we are currently experiencing and will experience for the next few weeks

[Liam J]

I'm not seeing a big swing towards the GFS? The ECM 00z is a very disturbed run firing depressions into the UK right up to day 10, so unfortunately more flooding misery to come looking at those charts and very windy at times. 

[knocker]

10 minutes ago, John Badrick said:

Not- I Wandered Lonely As A Cloud because I think that has no relation to the weather we will experience for a while yet. A whirl-Blast from behind the Hill is more apt for the weather we are currently experiencing and will experience for the next few weeks

But yes

I wandered lonely as a cloud

That floats on high o'er vales and hills,

When all at once I saw a crowd,

A host, of golden daffodils;

Beside the lake, beneath the trees,

Fluttering and dancing in the breeze.

[SMU]

Morning -

Merry christmas to all & your families 

The run of the day goes to the UKMO this morning - at 144 the atlantic jet is developing that kink ( an 'n' shape ) rather than a 'u' shape that gives the jet some directional energy SE rather than NE

we need this type of energy profile to get some undercutting ....

cheers

s

[northwestsnow]

1 minute ago, *Sub*Zero* said:

I'm not seeing a big swing towards the GFS? The ECM 00z is a very disturbed run firing depressions into the UK right up to day 10, so unfortunately more flooding misery to come looking at those charts and very windy at times. 

Iam

I feel ecm has not been at all interested in a scandy high until this morning?