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uk.sci.weather (UK Weather) (uk.sci.weather) For the discussion of daily weather events, chiefly affecting the UK and adjacent parts of Europe, both past and predicted. The discussion is open to all, but contributions on a practical scientific level are encouraged.

BOM/Extended MetO GM



 
 
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  #1  
Old February 15th 11, 12:16 PM posted to uk.sci.weather
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Posts: 3,030
Default BOM/Extended MetO GM

http://www.meteociel.fr/modeles/bome...mode=0&carte=0
Well blocked out to T+fantasy on the 00Z run with a strengthening E to SE'ly
flow at the surface by the end of the sequence.
IIRC, it offered a similarly blocked scenario yesterday too.

Could this variation on the world's best global model be one step ahead of
the rest.... confused, you will be.

Jon.

  #2  
Old February 15th 11, 01:01 PM posted to uk.sci.weather
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Posts: 1,467
Default BOM/Extended MetO GM

On Feb 15, 1:16*pm, "Jon O'Rourke" wrote:
http://www.meteociel.fr/modeles/bome...mode=0&carte=0
Well blocked out to T+fantasy on the 00Z run with a strengthening E to SE'ly
flow at the surface by the end of the sequence.
IIRC, it offered a similarly blocked scenario yesterday too.

Could this variation on the world's best global model be one step ahead of
the rest.... confused, you will be.


You bloody salesman, Jon...

Anyhow - this is fascinating - have you noticed when typically the
model diverges from the UKMet's output? Comparing BoM to UKMet is
quite a nice example of showing impact of initial conditions separate
from different model formulation (i.e. this is Meto GM vs Meto GM
rather than Meto GM vs, say, ECMWF).

Richard
  #3  
Old February 15th 11, 02:12 PM posted to uk.sci.weather
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Posts: 1,467
Default BOM/Extended MetO GM

On Feb 15, 2:01*pm, Richard Dixon wrote:
On Feb 15, 1:16*pm, "Jon O'Rourke" wrote:

http://www.meteociel.fr/modeles/bome...mode=0&carte=0
Well blocked out to T+fantasy on the 00Z run with a strengthening E to SE'ly
flow at the surface by the end of the sequence.
IIRC, it offered a similarly blocked scenario yesterday too.


Could this variation on the world's best global model be one step ahead of
the rest.... confused, you will be.


You bloody salesman, Jon...

Anyhow - this is fascinating - have you noticed when typically the
model diverges from the UKMet's output? Comparing BoM to UKMet is
quite a nice example of showing impact of initial conditions separate
from different model formulation (i.e. this is Meto GM vs Meto GM
rather than Meto GM vs, say, ECMWF).


Can compare he

http://91.121.84.31/modeles/bom/run/bom-0-144.png
http://www.meteociel.fr/ukmo/run/UW144-21.GIF

BoM has a bigger build of high pressure than the UKMet over
Scandinavia - interesting but not unexpected given the comedy see-
sawing of the models of late.

Richard

Richard
  #4  
Old February 15th 11, 05:00 PM posted to uk.sci.weather
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Posts: 6,314
Default BOM/Extended MetO GM

In article ,
Jon O'Rourke writes:
http://www.meteociel.fr/modeles/bome...mode=0&carte=0
Well blocked out to T+fantasy on the 00Z run with a strengthening E to
SE'ly flow at the surface by the end of the sequence.
IIRC, it offered a similarly blocked scenario yesterday too.

Could this variation on the world's best global model be one step ahead
of the rest.... confused, you will be.

Jon.


Well it had support from the ECMWF 00Z operational run, if not from that
model's ensemble or from the GFS.
--
John Hall

"The covers of this book are too far apart."
Ambrose Bierce (1842-1914)
  #5  
Old February 15th 11, 05:05 PM posted to uk.sci.weather
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Posts: 3,030
Default BOM/Extended MetO GM

"Richard Dixon" wrote in message
...

Anyhow - this is fascinating - have you noticed when typically the
model diverges from the UKMet's output?


Must admit I've only been comparing the two outputs in recent weeks and even
then not every day but when I have the general broadscale ideas were often
reasonably consistent even out to T+144. As you've pointed out they, not
surprisingly, tend to differ with the discrete pressure centre values at the
surface.

Jon.

  #6  
Old February 15th 11, 05:14 PM posted to uk.sci.weather
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Posts: 7,463
Default BOM/Extended MetO GM


"Richard Dixon" wrote in message
...
On Feb 15, 1:16 pm, "Jon O'Rourke" wrote:
http://www.meteociel.fr/modeles/bome...mode=0&carte=0
Well blocked out to T+fantasy on the 00Z run with a strengthening E to
SE'ly
flow at the surface by the end of the sequence.
IIRC, it offered a similarly blocked scenario yesterday too.

Could this variation on the world's best global model be one step ahead of
the rest.... confused, you will be.


You bloody salesman, Jon...

Anyhow - this is fascinating - have you noticed when typically the
model diverges from the UKMet's output? Comparing BoM to UKMet is
quite a nice example of showing impact of initial conditions separate
from different model formulation (i.e. this is Meto GM vs Meto GM
rather than Meto GM vs, say, ECMWF).

Richard
===========

In the early 1980s I did experiments swapping analyses with ECM and
vice-versa. i.e. running UKMO model from ECM analysis and ECM model from
UKMO analysis and from their own analyses and forecasts. The conclusion was
that runs from the same analysis were similar. This is no real surprise as
NWP is an initial value problem, so provided your model is capable of
solving the Navier Stokes equations sensibly then main variation will stem
from analysis differences. Not entirely true, it does depend on physics
parametrizations and integration methods as well, but world leading model
differences are likely to stem from analysis.

This, of course, is why Dawlish's selective forecasts work as he picks times
when analysis differences are small and predictive skill is increased. This
was all known in the 1980s of course when difference maps became all the
rage, I developed some of those for UKMO in the course of my work. Things
have moved on a lot since then with ensembles and time-lagged ensembles
giving insights into analysis difference contribution with exotic
diagnostics like "Shannon entropy". Stuff available to the public is very
limited in that regard.

Better stop now :-)

Will
--

  #7  
Old February 15th 11, 08:06 PM posted to uk.sci.weather
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Posts: 6,314
Default BOM/Extended MetO GM

In article ,
Jon O'Rourke writes:
http://www.meteociel.fr/modeles/bome...mode=0&carte=0
Well blocked out to T+fantasy on the 00Z run with a strengthening E to
SE'ly flow at the surface by the end of the sequence.
IIRC, it offered a similarly blocked scenario yesterday too.

Could this variation on the world's best global model be one step ahead
of the rest.... confused, you will be.

Jon.


It's sticking to its guns with the 12Z run. Mind you it was the most
enthusiastic of the models for extreme cold in its runs of a week or two
back, and that time it failed to materialise.
--
John Hall

"The covers of this book are too far apart."
Ambrose Bierce (1842-1914)
  #8  
Old February 17th 11, 08:28 AM posted to uk.sci.weather
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Posts: 7,878
Default BOM/Extended MetO GM

On Feb 15, 6:14*pm, "Will Hand" wrote:
"Richard Dixon" wrote in message

...
On Feb 15, 1:16 pm, "Jon O'Rourke" wrote:

http://www.meteociel.fr/modeles/bome...mode=0&carte=0
Well blocked out to T+fantasy on the 00Z run with a strengthening E to
SE'ly
flow at the surface by the end of the sequence.
IIRC, it offered a similarly blocked scenario yesterday too.


Could this variation on the world's best global model be one step ahead of
the rest.... confused, you will be.


You bloody salesman, Jon...

Anyhow - this is fascinating - have you noticed when typically the
model diverges from the UKMet's output? Comparing BoM to UKMet is
quite a nice example of showing impact of initial conditions separate
from different model formulation (i.e. this is Meto GM vs Meto GM
rather than Meto GM vs, say, ECMWF).

Richard
===========

In the early 1980s I did experiments swapping analyses with ECM and
vice-versa. i.e. running UKMO model from ECM analysis and ECM model from
UKMO analysis and from their own analyses and forecasts. The conclusion was
that runs from the same analysis were similar. This is no real surprise as
NWP is an initial value problem, so provided your model is capable of
solving the Navier Stokes equations sensibly then main variation will stem
from analysis differences. Not entirely true, it does depend on physics
parametrizations and integration methods as well, but world leading model
differences are likely to stem from analysis.

This, of course, is why Dawlish's selective forecasts work as he picks times
when analysis differences are small and predictive skill is increased. This
was all known in the 1980s of course when difference maps became all the
rage, I developed some of those for UKMO in the course of my work. Things
have moved on a lot since then with ensembles and time-lagged ensembles
giving insights into analysis difference contribution with exotic
diagnostics like "Shannon entropy". Stuff available to the public is very
limited in that regard.

Better stop now :-)

Will
--


Amazing. So if it was "all known in the 1980's" how come it is not
applied today and some amateur can find times when 10-day model output
can actually be used for confident prediction, whereas the MetO gives
no indication of probabilities, for the public, whatsoever? Is that
the result of 30 years of progress? "If things have moved on a lot"
since then, why hasn't predictive accuracy at 10 days plus moved with
it? That's exactly why I've done what I've done for the last 6 years;
to show that there really are times when it is possible using model
output - which has come on much further and has incorporated a finer
and finer, grid for the numerical input. Maybe some forecasters still
*think* they can do a better job at 10 days+ than the models their
agency has developed? Maybe because they still hang on to old
forecasting values and have not moved with the times; still applying
what they were taught as the baseline? That's a hypothesis for
explaining why forecast accuracy at 10 days has almost stood still
over the last 30 years; the small advances that there have been have
been due to better numerical input - as you've intimated above and
have little to do with other, dynamic and more "holistic" forecasting
techniques.

Better stop now, as the question hits at the heart of medium-term
forecasting, (which really has hardly improved in the last 30 years
and that's a fact that frustrates me to death) and thus is unlikely to
be answered and I've criticised something..........

If that 00z gfs comes to pass, a European high will have developed to
give a very mild end to February. *3.* perhaps from yesterday, gents?
(Pure speculation on my part ATM, as the ECM doesn't agree, but your
colleagues will be looking at those ensembles and seeing that the
operational is close to the mean. I wonder how much they'll take that
on board, in today's 6-15 day precis - which, hopefully, will give a
little more insight into conditions and temperatures than the present
one does!) *))
 




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