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!