I have been an advocate of probability forecasting on here for a few years
now. I have however been giving it some more thought and do have some
misgivings. What I have noticed in a forecast such as, say, "90% confidence
dry and mild, 10% cold and heavy snow" is that the interpretation by some of
the outcome is:-
1. If it is dry and mild then it was a good forecast.
2. If it is cold and there is heavy snow then there is the comment along
the lines "brilliant forecast, only a 10% chance and he/she was the only one
to spot it." (Not 90% inaccurate!)

This is happening to some extent, I feel, with the UKMO winter forecast. In
the overall expectation of 66% chance of being colder than average, people
that think it hasn't been that cold are saying it was good because it never
really said it would be and people that think it has been cold are saying it
was good because there was a 66% chance.

Perhaps the best option is to give a confidence in a particular forecast
with no other scenarios or their associated confidence.
(Which of course, the Met Office has in effect)
This is just some thoughts I've been having and am quite open to other
viewpoints as there is clearly more to it (or at least it's intrepretation)
than meets the eye.

Dave

Frankly, I didn't have a clue what the Met Office winter forecast
really meant. They were trying to baffle the public with
pseudo-science, made money out (that day's presentation to industry at
several hundred £££), meanwhile leaving the tabloid press with the
impression that it was going be a really bitter season.

You might just as well issue a forecast that says:
There is a 3 in 10 chance that March 2006 will be warmer than March
2005, a 3 in 10 chance that it will be colder, and a 4 in 10 chance
that it will be about the same.

Jack

In message , Dave.C
writes
I have been an advocate of probability forecasting on here for a few years
now. I have however been giving it some more thought and do have some
misgivings. What I have noticed in a forecast such as, say, "90% confidence
dry and mild, 10% cold and heavy snow" is that the interpretation by some of
the outcome is:-
1. If it is dry and mild then it was a good forecast.
2. If it is cold and there is heavy snow then there is the comment along
the lines "brilliant forecast, only a 10% chance and he/she was the only one
to spot it." (Not 90% inaccurate!)

This is happening to some extent, I feel, with the UKMO winter forecast. In
the overall expectation of 66% chance of being colder than average, people
that think it hasn't been that cold are saying it was good because it never
really said it would be and people that think it has been cold are saying it
was good because there was a 66% chance.

Perhaps the best option is to give a confidence in a particular forecast
with no other scenarios or their associated confidence.
(Which of course, the Met Office has in effect)
This is just some thoughts I've been having and am quite open to other
viewpoints as there is clearly more to it (or at least it's intrepretation)
than meets the eye.

Dave

As I have said a couple of times recently a single probability forecast
cannot be judged to be either accurate or inaccurate. Accuracy, or
perhaps better described as reliability, can only be judged by
evaluating a representative sample of probability forecasts. I would
think that a minimum of something like 20 forecasts would be needed.

If an event occurred, on average, on 3 occasions out of every 4 in which
it was forecast to have a 75 percent probability of occurrence then that
probability forecasting would have been spot on.

The Met Office forecast of a 2-1 probability of a colder than average
winter cannot, on its own, be evaluated as being either accurate or
inaccurate.

Norman.
(delete "thisbit" twice to e-mail)
--
Norman Lynagh Weather Consultancy
Chalfont St Giles 85m a.s.l.
England

wrote:
Frankly, I didn't have a clue what the Met Office winter forecast
really meant. They were trying to baffle the public with
pseudo-science, made money out (that day's presentation to industry at
several hundred £££), meanwhile leaving the tabloid press with the
impression that it was going be a really bitter season.

You might just as well issue a forecast that says:
There is a 3 in 10 chance that March 2006 will be warmer than March
2005, a 3 in 10 chance that it will be colder, and a 4 in 10 chance
that it will be about the same.

Jack

The forecast was perfectly clear to me. In effect it said "We
think it's going to be colder than recent winters but we're not too
sure". It was an honest statement and if that's "pseudoscience" give
me more of it.
The tabloid press did not get the impression that it was going
to be a "really bitter season" unless they can't read. What they did
was to say to themselves "How can we sensationalise this?" Thus the
*public* were given the impression of a severe winter. It wasn't just
the tabloids either; the Independent was as guilty as any. Whatever
the Met Office had said would have been either misunderstood or
distorted. That's the press for you. I don't know what the answer is.

Tudor Hughes, Warlingham, Surrey.

"Tudor Hughes" wrote in message Thus the*public*
were given the impression of a severe winter. It wasn't just the tabloids
either; the Independent was as guilty as any.

..... and still is as recent as this Saturday, had pictures of parts of
Europe and said of the "Siberian freeze" , "... and it's heading our way".
Of course it could still, but there was no current evidence or Met office
report to that effect.

Dave

Felly sgrifennodd Dave.C :
This is happening to some extent, I feel, with the UKMO winter forecast. In
the overall expectation of 66% chance of being colder than average, people
that think it hasn't been that cold are saying it was good because it never
really said it would be and people that think it has been cold are saying it
was good because there was a 66% chance.

That wasn't my reading of the forecast. My reading of it was that much of
Europe stood a 66% chance of being colder than average (it has been), and
that this was likely to have an effect on temperatures in the south,
leading to the probability of a colder than average winter there (i.e.
50%). That's probably right too isn't it?

Adrian
--
Adrian Shaw ais@
Adran Cyfrifiadureg, Prifysgol Cymru, aber.
Aberystwyth, Ceredigion, Cymru ac.
http://users.aber.ac.uk/ais uk

In article ,
Norman Lynagh writes:
As I have said a couple of times recently a single probability forecast
cannot be judged to be either accurate or inaccurate. Accuracy, or
perhaps better described as reliability, can only be judged by
evaluating a representative sample of probability forecasts. I would
think that a minimum of something like 20 forecasts would be needed.

If an event occurred, on average, on 3 occasions out of every 4 in
which it was forecast to have a 75 percent probability of occurrence
then that probability forecasting would have been spot on.

The Met Office forecast of a 2-1 probability of a colder than average
winter cannot, on its own, be evaluated as being either accurate or
inaccurate.

I can't really add anything to that except to say that I agree 100%.
--
John Hall
"Honest criticism is hard to take,
particularly from a relative, a friend,
an acquaintance, or a stranger." Franklin P Jones

"Dave.C" wrote in message
k...
I have been an advocate of probability forecasting on here for a few years
now. I have however been giving it some more thought and do have some
misgivings. What I have noticed in a forecast such as, say, "90%
confidence
dry and mild, 10% cold and heavy snow" is that the interpretation by some
of
the outcome is:-
1. If it is dry and mild then it was a good forecast.
2. If it is cold and there is heavy snow then there is the comment along
the lines "brilliant forecast, only a 10% chance and he/she was the only
one
to spot it." (Not 90% inaccurate!)

This is happening to some extent, I feel, with the UKMO winter forecast.
In
the overall expectation of 66% chance of being colder than average,
people
that think it hasn't been that cold are saying it was good because it
never
really said it would be and people that think it has been cold are saying
it
was good because there was a 66% chance.

Perhaps the best option is to give a confidence in a particular forecast
with no other scenarios or their associated confidence.
(Which of course, the Met Office has in effect)
This is just some thoughts I've been having and am quite open to other
viewpoints as there is clearly more to it (or at least it's
intrepretation)
than meets the eye.

Dave



For me the UKMO forecast was just a red herring. Okay possibly at the end of
the winter we may finish up slightly below average temp for the last six
years but that ain't exactly spectacular is it?
When I see very respectable able people on here blaming the media hyperbole
for creating ice age scare stories it really does grind a tad.
UKMO are IMO increasingly being used as another prop in the governments
"smoke & mirrors" trick. Are some of you telling me that UKMO were not aware
that the media would hyper ventilate with that forecast?
Nope it's my opinion that the good folk at UKMO did realise that the pre
would use up many a page on this story. I truly believe the UKMO were told
to release that forecast. Now I've never worked for or had any insight into
UKMO, but I would hazard a guess that more and more government interference
has crept into to their decreasing autonomy.
I know that many here will feel that it has nothing to do with politics.
Well I would argue how else can you explain the ridiculous over[-reaction to
what was once normal weather for many of us in the 60's, 70's and 80's.
You see when you warn about something that's unlikely to happen you can then
harvest the credit for being prepared if it happens or not.
I mean look at this from UKMO
http://www.met-office.gov.uk/health/...ptember05.html

What does it mean? Read some of the hocus pocus

"Clinicians Packs
The clinicians pack is now with the printers and 1000 will be ready for
circulation soon.

These packs include:

a.. a project folder containing a guide to delivering anticipatory care in
response to COPD forecasts. Resources will be made available on the COPD
forecasting web pages that can be added to the folder;

b.. a poster for displaying the COPD forecast in the surgery;

c.. a quick reference guide to delivering forecast driven anticipatory
care.
The patient and clinicians packs were put together by staff from the NHS and
the Met Office, many thanks to everyone involved."

What over exaggerated poppy cock. What's the GP going to do an Dan Corbet
impersonation? Maybe those clinician's pack will burn well on the fire.

How about this



"Colder-than-average winter forecast

The Met Office has given advanced warning to plan for a 'colder-than-average
winter'. Using a traffic light analogy, the organisation has written to
contingency planners in the Government - including the NHS - to put them on
Amber Alert.

This advice is based on the latest output from our seasonal forecasting
models. This forecast is produced using a combination of statistical models,
such as the North Atlantic Oscillation (NAO), and complex climate models,
with interpretation by operational forecasters.

Our latest predictions indicate a colder-than-average winter for much of
Europe. If this holds true, parts of the UK - especially southern regions -
are expected to have temperatures below normal.

The last eight winters have been relatively mild and may have given the
impression that these are 'normal'. The balance of probability is for a
winter colder than those experienced since 1995/6."



Okay we've temperatures in the south slightly below normal but I'd hardly
call it hypothermia inducing bitter winter weather, would you?

Nope with crime figure even worse than when I last ranted on this topic and
they've been massaged to hide the true extent. In fact the only people that
seem to be serving their time in prison are the once law abiding pensioners
who know feel so angry they have refused to pay their Council Tax.

Don't forget it's these suffering elderly that cannot be out after dark in
towns or cities , who have to sell their homes to pay for their care and are
frightened of going into to hospital for fear of MSRA and general neglect.
It's these very people that the government are claiming via UKMO to be
concerned about when exaggerating heat waves and cold spells that don't
happen. What ajoke.

Of course it's good to be pre warned of a serious weather event, but do me
favour.

I'll say it again UKMO are now part of the spin/diversion machine

All this tosh about 'amber' warnings, let me tell you "I've seen the light
brother".

"Tudor Hughes" wrote in message
oups.com...

The tabloid press did not get the impression that it was going
to be a "really bitter season" unless they can't read. What they did
was to say to themselves "How can we sensationalise this?" Thus the
*public* were given the impression of a severe winter. It wasn't just
the tabloids either; the Independent was as guilty as any. Whatever
the Met Office had said would have been either misunderstood or
distorted. That's the press for you. I don't know what the answer is.

Tudor Hughes, Warlingham, Surrey.

Tudor the answer is to stop buying newspapers. It's so liberating I tell you!

Will.
--

"John Hall" wrote in message
...

I can't really add anything to that except to say that I agree 100%.

Quite. This is a concept that even I can understand and have tried
to point out on more than one occaision.

Col
--
Bolton, Lancashire.
160m asl.