On Jan 31, 8:35*pm, Len Wood wrote:
On Jan 31, 8:14*pm, Dawlish wrote:





On Jan 31, 7:43*pm, Len Wood wrote:

On Jan 31, 6:06*pm, John Hall wrote:

In article ,

*ronaldbutton writes:
Writing as a mere layman ,apart from the ridiculous about turnabouts from
the Met Office

I've thought that the Met Offices 6-15 day forecast has been fairly
consistent for the last few days, though there's likely to be a big
tuirnabout in the one issued tomorrow. But what else can they do when
the weather "changes its mind"? They can't stick with a forecast once
they realise that it is no longer likely to be correct.

what suprises me most is the reliance on the models shown by
the 'experts' on this group.They are pored over and dissected every six
hours with renewed forecasts being issued daily,most of which are wrong
,unless of course we are in a mobile Westerly where models are fairly
irrelevant anyway

I'm certainly no expert, but I find dissecting the models great fun,
which is why I do it. And if you want to forecast, then there's no
alternative to the models, unless you believe in WeatherLawyer's
earthquakes. Of course, the Met Office has one advantage over us, in
that they get to see a lot of data from the ECMWF and their own model
that we amateurs never get to see. (Whereas the GFS seems to go in for
full disclosure.)

It is likely the cost of all this modelling is enormous (although it does
keep a lot of people off the unemployment lists I suppose),

They do produce surprisingly accurate forecasts out to 5-6 days for most
of the time. It's when you try to go beyond that, that it tends to go
pear-shaped. But the marginal extra cost of running the models beyond
5-6 days must be small, and it does quite often produce useful guidance.

so my question is
,what is the point of this slavish reliance on computer models ?, one
forecast issued every 24 hours would more than suffice,and reduce the
chances of getting it wrong by 75% .

Perhaps once every 6 hours, as the GFS does, is a bit excessive. But
things can change a lot in 24 hours, so I think that once every 12 hours
is justifiable.

By the way,is there any of you Met Office employed guys out there ready to
offer an explanation as to why the long *forecasts went so bellyup this
weekend....?

RonB

PS Unless there a satisfactory reply within the next 24 hours I shall set
Lawrence upon you !


--
John Hall
* * * * * *"Acting is merely the art of keeping a large group of people
* * * * * * from coughing."
* * * * * * * * * * * * * * * Sir Ralph Richardson (1902-83)

Looking at model output every six hours in order to get a better idea
of what might happen beyond 5 or 6 days has been shown to be
pointless.
Doing this is verging on suffering from obsessive compulsive disorder..
The six hourly model runs are there to try to put a better feel of how
things might be up to five days ahead.
Beyond that once a day is quite sufficient. Slavishly looking every
six hours at what might happen in 10 days time shows a lack of
understanding of how these models are constructed.

Len Wood
Wembury, SW Devon- Hide quoted text -

- Show quoted text -

All sorts of odd statements in there Len that I don't think are backed
by facts!

1. Where have you seen that "Looking at model output every six hours
in order to get a better idea of what might happen beyond 5 or 6 days
has been *shown* to be pointless",

2. Would you point to someone who has come to that conclusion?

3. Why does looking at 6-hourly output in any way show a lack of
understanding of how these models are constructed?

4. Why should looking at the models once a day be quite sufficient?

PS. We do not suffer from OCD. *We do not suffer from OCD. *We do not
suffer from OCD. *We do not suffer from OCD. *We do not suffer from
OCD. *We do not suffer from OCD. We do not suffer from OCD. We do not
suffer from OCD. We do not suffer from OCD. We do not suffer from OCD.
We do not suffer from OCD. See?- Hide quoted text -

- Show quoted text -

It's only experience Paul, especially looking at the recent scenarios,
(e.g. will the easterlies return or won't they?). There have been
numerous exclamations, OMGs, recently when model output has fluctuated
wildly over the six hour period. The uncertainties involved in
numerical modelling, which I've outlined many times on this ng,
cumulate with time and can be large after 5 or 6 days. So looking
every 6 hours at model output makes no sense.

I like your humour at the end of the post. But note I only said
verging on OCD. I would not be presumptious enough to diagnose it.

Len- Hide quoted text -

- Show quoted text -

It only makes sense if you can use the output at 5/6 days+ to forecast
with reasonable accuracy Len. I appreciate that much of the time that
is impossible and I can understand you mistrust of the models at that
distance - but that is the mistrust of someone who does not watch them
with "dedication" (a euphamism for OCD, of course, but then everyone's
hobby could be termed an OCD by those that don't share it and that
wouldn't be too fair!). I can assure you there are times when it is
possble to forecast, with 75-80% accuracy, at 10 days, using 6 and 12
hour updated output at that distance and if I didn't watch the output,
I wouldn't be able to do it!

Today, however, is not one of those days!

Will's analysis yesterday looks excellent. It does allow some
understanding of what's happened, because there are the lows, on the
12z ECM, slipping underneath northern blocking and producing an
easterly at T240 - more potent in the north, than the south. There
were hints of another change on the yesterday's 12z and that's why you
saw no forecast from me. The gfs doesn't agree at 10 days and we are
back into no-man's land for a while, looking through lime to see the
weather future!

Evens a cold easterly at 10 days. This thread is aptly titled Ronald!

In article
,
Dawlish writes:
snip
Evens a cold easterly at 10 days. This thread is aptly titled Ronald!

It certainly is. The one model that seems to have stuck to its guns over
the last few days is the UKMO, but that may be because it only runs out
to six days (or at least we only get to see its output that far ahead).
If it went out to 10 days (as in the ECMWF operational run) or 16 days
(GFS), maybe more flips would be evident.
--
John Hall
"Acting is merely the art of keeping a large group of people
from coughing."
Sir Ralph Richardson (1902-83)

On Sunday 31 Jan 2010 19:43, Len Wood scribbled:

Looking at model output every six hours in order to get a better idea
of what might happen beyond 5 or 6 days has been shown to be
pointless.
Doing this is verging on suffering from obsessive compulsive disorder.
The six hourly model runs are there to try to put a better feel of how
things might be up to five days ahead.
Beyond that once a day is quite sufficient. Slavishly looking every
six hours at what might happen in 10 days time shows a lack of
understanding of how these models are constructed

I think it can show the exact opposite. By looking at all runs instead of,
say, one run per day, you can get a better idea of the variation between the
runs and hence, perhaps, the reliability of a particular forecast - a bit
like a mental ensemble. A problem with looking at one run per day might be
that the run you pick is always a little biased.

A similar statement that I heard some time ago was regarding the frequency
that you should weigh yourself. It said that daily weighing was obsessive
and that once a month was ample. What this took no account of is daily
fluctuations in weight. If you weigh every day, you become aware of these
fluctuations and don't worry about them. If you only weigh yourself once a
month, you may get two extreme readings and worry about having put on a
couple of kilos. It's a bit like arguing that the climate has cooled since
1998. ;-)

--
Graham P Davis, Bracknell, Berks., UK. E-mail: newsman not newsboy
"I wear the cheese. It does not wear me."

On Feb 1, 11:02*am, Graham P Davis wrote:
On Sunday 31 Jan 2010 19:43, Len Wood scribbled:

Looking at model output every six hours in order to get a better idea
of what might happen beyond 5 or 6 days has been shown to be
pointless.
Doing this is verging on suffering from obsessive compulsive disorder.
The six hourly model runs are there to try to put a better feel of how
things might be up to five days ahead.
Beyond that once a day is quite sufficient. Slavishly looking every
six hours at what might happen in 10 days time shows a lack of
understanding of how these models are constructed

I think it can show the exact opposite. By looking at all runs instead of,
say, one run per day, you can get a better idea of the variation between the
runs and hence, perhaps, the reliability of a particular forecast - a bit
like a mental ensemble. A problem with looking at one run per day might be
that the run you pick is always a little biased.

Agreed.

A similar statement that I heard some time ago was regarding the frequency
that you should weigh yourself. It said that daily weighing was obsessive
and that once a month was ample. What this took no account of is daily
fluctuations in weight. If you weigh every day, you become aware of these
fluctuations and don't worry about them. If you only weigh yourself once a
month, you may get two extreme readings and worry about having put on a
couple of kilos.

Agreed.

It's a bit like arguing that the climate has cooled since
1998. *;-)

Agreed.

--
Graham P Davis, Bracknell, Berks., UK. *E-mail: newsman not newsboy
"I wear the cheese. It does not wear me."

On Feb 1, 10:24*am, John Hall wrote:
In article
,*Dawlis h writes:

snip

Evens a cold easterly at 10 days. This thread is aptly titled Ronald!

It certainly is. The one model that seems to have stuck to its guns over
the last few days is the UKMO, but that may be because it only runs out
to six days (or at least we only get to see its output that far ahead).
If it went out to 10 days (as in the ECMWF operational run) or 16 days
(GFS), maybe more flips would be evident.
--
John Hall
* * * * * *"Acting is merely the art of keeping a large group of people
* * * * * * from coughing."
* * * * * * * * * * * * * * * Sir Ralph Richardson (1902-83)

gfs 06z ploughs a milder furrow....., yet it is close to the gfs
ensemble mean right out past 10 days.

http://www.netweather.tv/index.cgi?a...nsviewer;sess=

Whereas the cold 00z ECM was very much on the colder side of the mean
past next weekend.

http://www.netweather.tv/index.cgi?a...nsviewer;sess=

On Feb 1, 12:28*pm, Dawlish wrote:
On Feb 1, 10:24*am, John Hall wrote:





In article
,*Dawlis h writes:

snip

Evens a cold easterly at 10 days. This thread is aptly titled Ronald!

It certainly is. The one model that seems to have stuck to its guns over
the last few days is the UKMO, but that may be because it only runs out
to six days (or at least we only get to see its output that far ahead).
If it went out to 10 days (as in the ECMWF operational run) or 16 days
(GFS), maybe more flips would be evident.
--
John Hall
* * * * * *"Acting is merely the art of keeping a large group of people
* * * * * * from coughing."
* * * * * * * * * * * * * * * Sir Ralph Richardson (1902-83)

gfs 06z ploughs a milder furrow....., yet it is close to the gfs
ensemble mean right out past 10 days.

http://www.netweather.tv/index.cgi?a...nsviewer;sess=

Whereas the cold 00z ECM was very much on the colder side of the mean
past next weekend.

http://www.netweather.tv/index.cgi?a...sviewer;sess=- Hide quoted text -

- Show quoted text -

Presently we've got the 00z ECM showing easterlies at T240, the 12z
gfs showing easterlies at T240 and the GEM showing westerlies at T240,
with the UKMO showing easterlies at T144. All these 4 are just about
the *exact opposite* of what they were showing at this time yesterday.

This is Olympic class tumbling, never mind somesaults! I don't think
I can ever remember this happening and two up the models (gfs and ECM)
have had upgrades during January. *O

Fascinating, fun and pretty useless for getting a 10 day forecast
correct!

On Feb 1, 4:51*pm, Dawlish wrote:
On Feb 1, 12:28*pm, Dawlish wrote:





On Feb 1, 10:24*am, John Hall wrote:

In article
,*Dawlis h writes:

snip

Evens a cold easterly at 10 days. This thread is aptly titled Ronald!

It certainly is. The one model that seems to have stuck to its guns over
the last few days is the UKMO, but that may be because it only runs out
to six days (or at least we only get to see its output that far ahead).
If it went out to 10 days (as in the ECMWF operational run) or 16 days
(GFS), maybe more flips would be evident.
--
John Hall
* * * * * *"Acting is merely the art of keeping a large group of people
* * * * * * from coughing."
* * * * * * * * * * * * * * * Sir Ralph Richardson (1902-83)

gfs 06z ploughs a milder furrow....., yet it is close to the gfs
ensemble mean right out past 10 days.

http://www.netweather.tv/index.cgi?a...nsviewer;sess=

Whereas the cold 00z ECM was very much on the colder side of the mean
past next weekend.

http://www.netweather.tv/index.cgi?a...wer;sess=-Hide quoted text -

- Show quoted text -

Presently we've got the 00z ECM showing easterlies at T240, the 12z
gfs showing easterlies at T240 and the GEM showing westerlies at T240,
with the UKMO showing easterlies at T144. All these 4 are just about
the *exact opposite* of what they were showing at this time yesterday.

This is Olympic class *tumbling, never mind somesaults! I don't think
I can ever remember this happening and two up the models (gfs and ECM)
have had upgrades during January. *O

Fascinating, fun and pretty useless for getting a 10 day forecast
correct!- Hide quoted text -

- Show quoted text -

..............and thinking about that over a rather nice tea, I think
that yesterday, each model was showing almost the exact opposite of
what it was the day before that, which actually means that each model
is now showing, to a greater, or lesser extent, what it was 2 days
ago!

I think you are on to something Len, but instead of daily, maybe we
should restrict ourselves to dipping into the models once every 2 days
(or restrict model runs to once every 2 days, thus saving a fortune,
as Ronald wished). If we'd done that, we'd never have had any of this
silly and unnecessary excitement.

*))

In article
,
Dawlish writes:
On Feb 1, 4:51*pm, Dawlish wrote:

Presently we've got the 00z ECM showing easterlies at T240, the 12z
gfs showing easterlies at T240 and the GEM showing westerlies at T240,
with the UKMO showing easterlies at T144. All these 4 are just about
the *exact opposite* of what they were showing at this time yesterday.

This is Olympic class *tumbling, never mind somesaults! I don't think
I can ever remember this happening and two up the models (gfs and ECM)
have had upgrades during January. *O

Fascinating, fun and pretty useless for getting a 10 day forecast
correct!- Hide quoted text -

- Show quoted text -

.............and thinking about that over a rather nice tea, I think
that yesterday, each model was showing almost the exact opposite of
what it was the day before that, which actually means that each model
is now showing, to a greater, or lesser extent, what it was 2 days
ago!

I think you are on to something Len, but instead of daily, maybe we
should restrict ourselves to dipping into the models once every 2 days
(or restrict model runs to once every 2 days, thus saving a fortune,
as Ronald wished). If we'd done that, we'd never have had any of this
silly and unnecessary excitement.

*))



At last we seem to have some agreement between the main models, with
today's 12Z operational runs from GFS, ECMWF and UKMO all suggesting
that an easterly will set in as early as this weekend though, at least
initially, it doesn't look like being particularly cold.

A new feature is that from about a week out the 12Z GFS has a
substantial number of very cold ensemble members, with 850mb temps for
London at or below -10C. They're still in the minority, though, with the
ensemble mean no more than a degree or two belong the long-term mean.
--
John Hall
"Acting is merely the art of keeping a large group of people
from coughing."
Sir Ralph Richardson (1902-83)

On Feb 1, 6:54*pm, John Hall wrote:
In article
,





*Dawlish writes:
On Feb 1, 4:51*pm, Dawlish wrote:

Presently we've got the 00z ECM showing easterlies at T240, the 12z
gfs showing easterlies at T240 and the GEM showing westerlies at T240,
with the UKMO showing easterlies at T144. All these 4 are just about
the *exact opposite* of what they were showing at this time yesterday.

This is Olympic class *tumbling, never mind somesaults! I don't think
I can ever remember this happening and two up the models (gfs and ECM)
have had upgrades during January. *O

Fascinating, fun and pretty useless for getting a 10 day forecast
correct!- Hide quoted text -

- Show quoted text -

.............and thinking about that over a rather nice tea, I think
that yesterday, each model was showing almost the exact opposite of
what it was the day before that, which actually means that each model
is now showing, to a greater, or lesser extent, what it was 2 days
ago!

I think you are on to something Len, but instead of daily, maybe we
should restrict ourselves to dipping into the models once every 2 days
(or restrict model runs to once every 2 days, thus saving a fortune,
as Ronald wished). If we'd done that, we'd never have had any of this
silly and unnecessary excitement.

*))



At last we seem to have some agreement between the main models, with
today's 12Z operational runs from GFS, ECMWF and UKMO all suggesting
that an easterly will set in as early as this weekend though, at least
initially, it doesn't look like being particularly cold.

A new feature is that from about a week out the 12Z GFS has a
substantial number of very cold ensemble members, with 850mb temps for
London at or below -10C. They're still in the minority, though, with the
ensemble mean no more than a degree or two belong the long-term mean.
--
John Hall
* * * * * *"Acting is merely the art of keeping a large group of people
* * * * * * from coughing."
* * * * * * * * * * * * * * * Sir Ralph Richardson (1902-83)- Hide quoted text -

- Show quoted text -

There's some agreement this morning John; both the gfs and the ECM now
agree on us *not* having easterlies at 10 days!! shakes head

The gfs 00z ensemble mean suddenly looks mild right out to the edge of
reality - with a fairly tight plume out past 10 days and only one
member below the 30-day mean for a 4-day period from 7 Feb to 11 Feb.
Staggeringly mild compared to last night's ens.

http://www.wzkarten3.de/pics/MT8_London_ens.png

This was the ECM ensembles from the 12z yesterday, with the gfs 12z
operational close to the mean right the way through.

http://www.meteogroup.co.uk/uk/home/..._forecast.html

In years of Internet model watching and a dreadful case of OCD in
monitoring them ( *)) ), I think I can confidently say that I've
never seen such a level of inconsistency, from all the major models,
over a 4-day period. That's why 10-day forecasting is *so* difficult
and is simply not possible, with reasonable accuracy, most of the
time.

In article
,
Dawlish writes:
There's some agreement this morning John; both the gfs and the ECM now
agree on us *not* having easterlies at 10 days!! shakes head

snip

In years of Internet model watching and a dreadful case of OCD in
monitoring them ( *)) ), I think I can confidently say that I've
never seen such a level of inconsistency, from all the major models,
over a 4-day period. That's why 10-day forecasting is *so* difficult
and is simply not possible, with reasonable accuracy, most of the
time.

Yep. The only model out of the three I monitor not to have done a volte
face between yesterday's 12Z run and today 00Z in the UKMO, which still
brings in an easterly this weekend.
--
John Hall
"Acting is merely the art of keeping a large group of people
from coughing."
Sir Ralph Richardson (1902-83)