What I've done is look at the forecasts and compared them to
each other. I haven't correlated whether the weather they
forecast actually happened, just how often the forecasts changed
(since a 5 day forecast that changes the very next day can't
be relied on, so isn't any use).

As the weather got more changeable after the summer, so the
accuracy of the forecasts dropped. Compared with August's 50%
likelihood of the next-day forecast being accurate, Spetember's
40% (i.e. it missed the mark on 3 more days) is disappointing.

The basic problem of having too many categories is even more
pronounced this time, as when I reclassified the 9 types of
weather in Septemer's forecast down to just the basics:
sun, cloud, rain the chances of being correct next day rise
to 77% and the forecast for +4 days goes from a lower than
random chance to a usable 11 days out of 30

forecast forecast on: times num of days
-- date -- on day D-1 D-2 D-3 D-4 correct changes ahead
Wed 1 Sep S S S S S 4 0 4
Thu 2 Sep S* SI SI SI SI 0 1 0 !
Fri 3 Sep SI S WC SI SI 2 3 0
Sat 4 Sep S SI S SI WC 1 4 0
Sun 5 Sep LRS SI SI S SI 0 3 0 !
Mon 6 Sep HR HR LRS SI SI 1 2 1
Tue 7 Sep HRS HRS HRS HR SI 2 2 2
Wed 8 Sep D LR LRS HRS HRS 0 3 0 !
Thu 9 Sep SI S SI SI HRS 2 3 0
Fri 10 Sep GC GC WC SI LR 1 3 1
Sat 11 Sep SI LR SI LR HR 1 4 0
Sun 12 Sep S SI SI S S 2 2 0
Mon 13 Sep SI SI SI SI S 3 1 3
Tue 14 Sep LR LR LR HR LR 3 2 2
Wed 15 Sep SI S S SI SI 2 2 0
Wed 15 Sep SI* S S SI SI 2 2 0
Fri 17 Sep S GC WC SI S 1 4 0
Sat 18 Sep SI SI SI HR SI 3 2 2
Sun 19 Sep SI* LR LR S HR 0 3 0 !
Mon 20 Sep SI* SI SI SI S 3 1 3
Tue 21 Sep SI* SI S LR S 1 3 1
Wed 22 Sep S S S S LRS 3 1 3
Thu 23 Sep HRS HRS HRS LRS LRS 2 1 2
Fri 24 Sep HRS* HRS LR HRS S 2 3 1
Sat 25 Sep S SI LRS SI GC 0 4 0 !
Sun 26 Sep SI GC SI LRS GC 1 4 0
Mon 27 Sep SI* HRS GC GC LRS 0 3 0 !
Tue 28 Sep GC SI SI WC SI 0 3 0 !
Wed 29 Sep LR HR HR LR GC 1 3 0
Thu 30 Sep SI S SI SI S 2 3 0

For last 30 days: avg 2.50 different forecasts per day
On average forecasted 0.83 days ahead
Correct 4 days ahead: 1 times
Correct 3 days ahead: 4 times
Correct 2 days ahead: 8 times
Correct 1 day ahead: 12 times (40.0%)
Number of times the weather was same as yesterday(*): 7 times (23.3%)
Number of days every forecast was wrong(!): 7 times (23.3%)

Key:
D: Drizzle 1 occurrences, predicted 0 times under-forecast
GC: Grey Cloud 2 occurrences, predicted 8 times about right
HR: Heavy Rain 1 occurrences, predicted 8 times over-forecast
HRS: Heavy Rain Shower 3 occurrences, predicted 10 times about right
LR: Light Rain 2 occurrences, predicted 12 times over-forecast
LRS: Light Rain Shower 1 occurrences, predicted 8 times over-forecast
S: Sunny 7 occurrences, predicted 26 times about right
SI: Sunny Intervals 13 occurrences, predicted 43 times about right
WC: White Cloud 0 occurrences, predicted 5 times over-forecast

On Oct 1, 5:24*pm, pete wrote:
What I've done is look at the forecasts and compared them to
each other. *I haven't correlated whether the weather they
forecast actually happened, just how often the forecasts changed
(since a *5 day forecast that changes the very next day can't
be relied on, so isn't any use).

As the weather got more changeable after the summer, so the
accuracy of the forecasts dropped. Compared with August's 50%
likelihood of the next-day forecast being accurate, Spetember's
40% *(i.e. it missed the mark on 3 more days) is disappointing.

The basic problem of having too many categories is even more
pronounced this time, as when I reclassified the 9 types of
weather in Septemer's forecast down to just the basics:
sun, cloud, rain the chances of being correct next day rise
to 77% and the forecast for +4 days goes from a lower than
random chance to a usable 11 days out of 30

* * * * * forecast *forecast on: * *times * num of *days
-- date -- on day * D-1 D-2 D-3 D-4 correct changes ahead
Wed *1 Sep * *S * * *S * S * S * S * *4 * * * 0 * * *4
Thu *2 Sep * *S* * *SI *SI *SI *SI * *0 * * * 1 * * *0 !
Fri *3 Sep * SI * * *S *WC *SI *SI * *2 * * * 3 * * *0
Sat *4 Sep * *S * * SI * S *SI *WC * *1 * * * 4 * * *0
Sun *5 Sep *LRS * * SI *SI * S *SI * *0 * * * 3 * * *0 !
Mon *6 Sep * HR * * HR LRS *SI *SI * *1 * * * 2 * * *1
Tue *7 Sep *HRS * *HRS HRS *HR *SI * *2 * * * 2 * * *2
Wed *8 Sep * *D * * LR LRS HRS HRS * *0 * * * 3 * * *0 !
Thu *9 Sep * SI * * *S *SI *SI HRS * *2 * * * 3 * * *0
Fri 10 Sep * GC * * GC *WC *SI *LR * *1 * * * 3 * * *1
Sat 11 Sep * SI * * LR *SI *LR *HR * *1 * * * 4 * * *0
Sun 12 Sep * *S * * SI *SI * S * S * *2 * * * 2 * * *0
Mon 13 Sep * SI * * SI *SI *SI * S * *3 * * * 1 * * *3
Tue 14 Sep * LR * * LR *LR *HR *LR * *3 * * * 2 * * *2
Wed 15 Sep * SI * * *S * S *SI *SI * *2 * * * 2 * * *0
Wed 15 Sep * SI* * * S * S *SI *SI * *2 * * * 2 * * *0
Fri 17 Sep * *S * * GC *WC *SI * S * *1 * * * 4 * * *0
Sat 18 Sep * SI * * SI *SI *HR *SI * *3 * * * 2 * * *2
Sun 19 Sep * SI* * *LR *LR * S *HR * *0 * * * 3 * * *0 !
Mon 20 Sep * SI* * *SI *SI *SI * S * *3 * * * 1 * * *3
Tue 21 Sep * SI* * *SI * S *LR * S * *1 * * * 3 * * *1
Wed 22 Sep * *S * * *S * S * S LRS * *3 * * * 1 * * *3
Thu 23 Sep *HRS * *HRS HRS LRS LRS * *2 * * * 1 * * *2
Fri 24 Sep *HRS* * HRS *LR HRS * S * *2 * * * 3 * * *1
Sat 25 Sep * *S * * SI LRS *SI *GC * *0 * * * 4 * * *0 !
Sun 26 Sep * SI * * GC *SI LRS *GC * *1 * * * 4 * * *0
Mon 27 Sep * SI* * HRS *GC *GC LRS * *0 * * * 3 * * *0 !
Tue 28 Sep * GC * * SI *SI *WC *SI * *0 * * * 3 * * *0 !
Wed 29 Sep * LR * * HR *HR *LR *GC * *1 * * * 3 * * *0
Thu 30 Sep * SI * * *S *SI *SI * S * *2 * * * 3 * * *0

For last 30 days: avg 2.50 different forecasts per day
On average forecasted 0.83 days ahead
Correct 4 days ahead: 1 times
Correct 3 days ahead: 4 times
Correct 2 days ahead: 8 times
Correct 1 day ahead: 12 times (40.0%)
Number of times the weather was same as yesterday(*): 7 times (23.3%)
Number of days every forecast was wrong(!): 7 times (23.3%)

Key:
* D: * * * * * * Drizzle *1 occurrences, predicted * 0 times under-forecast
*GC: * * * * *Grey Cloud *2 occurrences, predicted * 8 times about right
*HR: * * * * *Heavy Rain *1 occurrences, predicted * 8 times over-forecast
HRS: * Heavy Rain Shower *3 occurrences, predicted *10 times about right
*LR: * * * * *Light Rain *2 occurrences, predicted *12 times over-forecast
LRS: * Light Rain Shower *1 occurrences, predicted * 8 times over-forecast
* S: * * * * * * * Sunny *7 occurrences, predicted *26 times about right
*SI: * * Sunny Intervals 13 occurrences, predicted *43 times about right
*WC: * * * * White Cloud *0 occurrences, predicted * 5 times over-forecast

Sorry, but have I missed something? Forecasts by who? Are you saying
that the UKMO forecasts are crap?

On Fri, 1 Oct 2010 09:29:10 -0700 (PDT), Len Wood wrote:
On Oct 1, 5:24Â*pm, pete wrote:
What I've done is look at the forecasts and compared them to
each other. Â*I haven't correlated whether the weather they
forecast actually happened, just how often the forecasts changed
(since a Â*5 day forecast that changes the very next day can't
be relied on, so isn't any use).

As the weather got more changeable after the summer, so the
accuracy of the forecasts dropped. Compared with August's 50%
likelihood of the next-day forecast being accurate, Spetember's
40% Â*(i.e. it missed the mark on 3 more days) is disappointing.

The basic problem of having too many categories is even more
pronounced this time, as when I reclassified the 9 types of
weather in Septemer's forecast down to just the basics:
sun, cloud, rain the chances of being correct next day rise
to 77% and the forecast for +4 days goes from a lower than
random chance to a usable 11 days out of 30

Â* Â* Â* Â* Â* forecast Â*forecast on: Â* Â*times Â* num of Â*days
-- date -- on day Â* D-1 D-2 D-3 D-4 correct changes ahead
Wed Â*1 Sep Â* Â*S Â* Â* Â*S Â* S Â* S Â* S Â* Â*4 Â* Â* Â* 0 Â* Â* Â*4
Thu Â*2 Sep Â* Â*S* Â* Â*SI Â*SI Â*SI Â*SI Â* Â*0 Â* Â* Â* 1 Â* Â* Â*0 !
Fri Â*3 Sep Â* SI Â* Â* Â*S Â*WC Â*SI Â*SI Â* Â*2 Â* Â* Â* 3 Â* Â* Â*0
Sat Â*4 Sep Â* Â*S Â* Â* SI Â* S Â*SI Â*WC Â* Â*1 Â* Â* Â* 4 Â* Â* Â*0
Sun Â*5 Sep Â*LRS Â* Â* SI Â*SI Â* S Â*SI Â* Â*0 Â* Â* Â* 3 Â* Â* Â*0 !
Mon Â*6 Sep Â* HR Â* Â* HR LRS Â*SI Â*SI Â* Â*1 Â* Â* Â* 2 Â* Â* Â*1
Tue Â*7 Sep Â*HRS Â* Â*HRS HRS Â*HR Â*SI Â* Â*2 Â* Â* Â* 2 Â* Â* Â*2
Wed Â*8 Sep Â* Â*D Â* Â* LR LRS HRS HRS Â* Â*0 Â* Â* Â* 3 Â* Â* Â*0 !
Thu Â*9 Sep Â* SI Â* Â* Â*S Â*SI Â*SI HRS Â* Â*2 Â* Â* Â* 3 Â* Â* Â*0
Fri 10 Sep Â* GC Â* Â* GC Â*WC Â*SI Â*LR Â* Â*1 Â* Â* Â* 3 Â* Â* Â*1
Sat 11 Sep Â* SI Â* Â* LR Â*SI Â*LR Â*HR Â* Â*1 Â* Â* Â* 4 Â* Â* Â*0
Sun 12 Sep Â* Â*S Â* Â* SI Â*SI Â* S Â* S Â* Â*2 Â* Â* Â* 2 Â* Â* Â*0
Mon 13 Sep Â* SI Â* Â* SI Â*SI Â*SI Â* S Â* Â*3 Â* Â* Â* 1 Â* Â* Â*3
Tue 14 Sep Â* LR Â* Â* LR Â*LR Â*HR Â*LR Â* Â*3 Â* Â* Â* 2 Â* Â* Â*2
Wed 15 Sep Â* SI Â* Â* Â*S Â* S Â*SI Â*SI Â* Â*2 Â* Â* Â* 2 Â* Â* Â*0
Wed 15 Sep Â* SI* Â* Â* S Â* S Â*SI Â*SI Â* Â*2 Â* Â* Â* 2 Â* Â* Â*0
Fri 17 Sep Â* Â*S Â* Â* GC Â*WC Â*SI Â* S Â* Â*1 Â* Â* Â* 4 Â* Â* Â*0
Sat 18 Sep Â* SI Â* Â* SI Â*SI Â*HR Â*SI Â* Â*3 Â* Â* Â* 2 Â* Â* Â*2
Sun 19 Sep Â* SI* Â* Â*LR Â*LR Â* S Â*HR Â* Â*0 Â* Â* Â* 3 Â* Â* Â*0 !
Mon 20 Sep Â* SI* Â* Â*SI Â*SI Â*SI Â* S Â* Â*3 Â* Â* Â* 1 Â* Â* Â*3
Tue 21 Sep Â* SI* Â* Â*SI Â* S Â*LR Â* S Â* Â*1 Â* Â* Â* 3 Â* Â* Â*1
Wed 22 Sep Â* Â*S Â* Â* Â*S Â* S Â* S LRS Â* Â*3 Â* Â* Â* 1 Â* Â* Â*3
Thu 23 Sep Â*HRS Â* Â*HRS HRS LRS LRS Â* Â*2 Â* Â* Â* 1 Â* Â* Â*2
Fri 24 Sep Â*HRS* Â* HRS Â*LR HRS Â* S Â* Â*2 Â* Â* Â* 3 Â* Â* Â*1
Sat 25 Sep Â* Â*S Â* Â* SI LRS Â*SI Â*GC Â* Â*0 Â* Â* Â* 4 Â* Â* Â*0 !
Sun 26 Sep Â* SI Â* Â* GC Â*SI LRS Â*GC Â* Â*1 Â* Â* Â* 4 Â* Â* Â*0
Mon 27 Sep Â* SI* Â* HRS Â*GC Â*GC LRS Â* Â*0 Â* Â* Â* 3 Â* Â* Â*0 !
Tue 28 Sep Â* GC Â* Â* SI Â*SI Â*WC Â*SI Â* Â*0 Â* Â* Â* 3 Â* Â* Â*0 !
Wed 29 Sep Â* LR Â* Â* HR Â*HR Â*LR Â*GC Â* Â*1 Â* Â* Â* 3 Â* Â* Â*0
Thu 30 Sep Â* SI Â* Â* Â*S Â*SI Â*SI Â* S Â* Â*2 Â* Â* Â* 3 Â* Â* Â*0

For last 30 days: avg 2.50 different forecasts per day
On average forecasted 0.83 days ahead
Correct 4 days ahead: 1 times
Correct 3 days ahead: 4 times
Correct 2 days ahead: 8 times
Correct 1 day ahead: 12 times (40.0%)
Number of times the weather was same as yesterday(*): 7 times (23.3%)
Number of days every forecast was wrong(!): 7 times (23.3%)

Key:
Â* D: Â* Â* Â* Â* Â* Â* Drizzle Â*1 occurrences, predicted Â* 0 times under-forecast
Â*GC: Â* Â* Â* Â* Â*Grey Cloud Â*2 occurrences, predicted Â* 8 times about right
Â*HR: Â* Â* Â* Â* Â*Heavy Rain Â*1 occurrences, predicted Â* 8 times over-forecast
HRS: Â* Heavy Rain Shower Â*3 occurrences, predicted Â*10 times about right
Â*LR: Â* Â* Â* Â* Â*Light Rain Â*2 occurrences, predicted Â*12 times over-forecast
LRS: Â* Light Rain Shower Â*1 occurrences, predicted Â* 8 times over-forecast
Â* S: Â* Â* Â* Â* Â* Â* Â* Sunny Â*7 occurrences, predicted Â*26 times about right
Â*SI: Â* Â* Sunny Intervals 13 occurrences, predicted Â*43 times about right
Â*WC: Â* Â* Â* Â* White Cloud Â*0 occurrences, predicted Â* 5 times over-forecast

Sorry, but have I missed something? Forecasts by who? Are you saying
that the UKMO forecasts are crap?

These are the 5 day forecasts supplied to the BBC website for my postcode
area.

"pete" wrote in message
...
On Fri, 1 Oct 2010 09:29:10 -0700 (PDT), Len Wood wrote:
On Oct 1, 5:24 pm, pete wrote:
These are the 5 day forecasts supplied to the BBC website for my postcode
area.


What is your postcode Pete?

E-mail me if it is a secret!

TIA

Will
--

On Oct 1, 5:29*pm, Len Wood wrote:
On Oct 1, 5:24*pm, pete wrote:





What I've done is look at the forecasts and compared them to
each other. *I haven't correlated whether the weather they
forecast actually happened, just how often the forecasts changed
(since a *5 day forecast that changes the very next day can't
be relied on, so isn't any use).

As the weather got more changeable after the summer, so the
accuracy of the forecasts dropped. Compared with August's 50%
likelihood of the next-day forecast being accurate, Spetember's
40% *(i.e. it missed the mark on 3 more days) is disappointing.

The basic problem of having too many categories is even more
pronounced this time, as when I reclassified the 9 types of
weather in Septemer's forecast down to just the basics:
sun, cloud, rain the chances of being correct next day rise
to 77% and the forecast for +4 days goes from a lower than
random chance to a usable 11 days out of 30

* * * * * forecast *forecast on: * *times * num of *days
-- date -- on day * D-1 D-2 D-3 D-4 correct changes ahead
Wed *1 Sep * *S * * *S * S * S * S * *4 * * * 0 * * *4
Thu *2 Sep * *S* * *SI *SI *SI *SI * *0 * * * 1 * * *0 !
Fri *3 Sep * SI * * *S *WC *SI *SI * *2 * * * 3 * * *0
Sat *4 Sep * *S * * SI * S *SI *WC * *1 * * * 4 * * *0
Sun *5 Sep *LRS * * SI *SI * S *SI * *0 * * * 3 * * *0 !
Mon *6 Sep * HR * * HR LRS *SI *SI * *1 * * * 2 * * *1
Tue *7 Sep *HRS * *HRS HRS *HR *SI * *2 * * * 2 * * *2
Wed *8 Sep * *D * * LR LRS HRS HRS * *0 * * * 3 * * *0 !
Thu *9 Sep * SI * * *S *SI *SI HRS * *2 * * * 3 * * *0
Fri 10 Sep * GC * * GC *WC *SI *LR * *1 * * * 3 * * *1
Sat 11 Sep * SI * * LR *SI *LR *HR * *1 * * * 4 * * *0
Sun 12 Sep * *S * * SI *SI * S * S * *2 * * * 2 * * *0
Mon 13 Sep * SI * * SI *SI *SI * S * *3 * * * 1 * * *3
Tue 14 Sep * LR * * LR *LR *HR *LR * *3 * * * 2 * * *2
Wed 15 Sep * SI * * *S * S *SI *SI * *2 * * * 2 * * *0
Wed 15 Sep * SI* * * S * S *SI *SI * *2 * * * 2 * * *0
Fri 17 Sep * *S * * GC *WC *SI * S * *1 * * * 4 * * *0
Sat 18 Sep * SI * * SI *SI *HR *SI * *3 * * * 2 * * *2
Sun 19 Sep * SI* * *LR *LR * S *HR * *0 * * * 3 * * *0 !
Mon 20 Sep * SI* * *SI *SI *SI * S * *3 * * * 1 * * *3
Tue 21 Sep * SI* * *SI * S *LR * S * *1 * * * 3 * * *1
Wed 22 Sep * *S * * *S * S * S LRS * *3 * * * 1 * * *3
Thu 23 Sep *HRS * *HRS HRS LRS LRS * *2 * * * 1 * * *2
Fri 24 Sep *HRS* * HRS *LR HRS * S * *2 * * * 3 * * *1
Sat 25 Sep * *S * * SI LRS *SI *GC * *0 * * * 4 * * *0 !
Sun 26 Sep * SI * * GC *SI LRS *GC * *1 * * * 4 * * *0
Mon 27 Sep * SI* * HRS *GC *GC LRS * *0 * * * 3 * * *0 !
Tue 28 Sep * GC * * SI *SI *WC *SI * *0 * * * 3 * * *0 !
Wed 29 Sep * LR * * HR *HR *LR *GC * *1 * * * 3 * * *0
Thu 30 Sep * SI * * *S *SI *SI * S * *2 * * * 3 * * *0

For last 30 days: avg 2.50 different forecasts per day
On average forecasted 0.83 days ahead
Correct 4 days ahead: 1 times
Correct 3 days ahead: 4 times
Correct 2 days ahead: 8 times
Correct 1 day ahead: 12 times (40.0%)
Number of times the weather was same as yesterday(*): 7 times (23.3%)
Number of days every forecast was wrong(!): 7 times (23.3%)

Key:
* D: * * * * * * Drizzle *1 occurrences, predicted * 0 times under-forecast
*GC: * * * * *Grey Cloud *2 occurrences, predicted * 8 times about right
*HR: * * * * *Heavy Rain *1 occurrences, predicted * 8 times over-forecast
HRS: * Heavy Rain Shower *3 occurrences, predicted *10 times about right
*LR: * * * * *Light Rain *2 occurrences, predicted *12 times over-forecast
LRS: * Light Rain Shower *1 occurrences, predicted * 8 times over-forecast
* S: * * * * * * * Sunny *7 occurrences, predicted *26 times about right
*SI: * * Sunny Intervals 13 occurrences, predicted *43 times about right
*WC: * * * * White Cloud *0 occurrences, predicted * 5 times over-forecast

Sorry, but have I missed something? Forecasts by who? Are you saying
that the UKMO forecasts are crap?- Hide quoted text -

- Show quoted text -

It's really the kind of thing the MetO should be doing for its
customers. The analysis of model accuracy that is produced by NOAA,
doesn't reflect what happens on the ground and analyses like this do.
I'm always grateful to Pete for doing this, as it takes time and
effort.

On Oct 2, 8:09*am, Dawlish wrote:
On Oct 1, 5:29*pm, Len Wood wrote:





On Oct 1, 5:24*pm, pete wrote:

What I've done is look at the forecasts and compared them to
each other. *I haven't correlated whether the weather they
forecast actually happened, just how often the forecasts changed
(since a *5 day forecast that changes the very next day can't
be relied on, so isn't any use).

As the weather got more changeable after the summer, so the
accuracy of the forecasts dropped. Compared with August's 50%
likelihood of the next-day forecast being accurate, Spetember's
40% *(i.e. it missed the mark on 3 more days) is disappointing.

The basic problem of having too many categories is even more
pronounced this time, as when I reclassified the 9 types of
weather in Septemer's forecast down to just the basics:
sun, cloud, rain the chances of being correct next day rise
to 77% and the forecast for +4 days goes from a lower than
random chance to a usable 11 days out of 30

* * * * * forecast *forecast on: * *times * num of *days
-- date -- on day * D-1 D-2 D-3 D-4 correct changes ahead
Wed *1 Sep * *S * * *S * S * S * S * *4 * * * 0 * * *4
Thu *2 Sep * *S* * *SI *SI *SI *SI * *0 * * * 1 * * *0 !
Fri *3 Sep * SI * * *S *WC *SI *SI * *2 * * * 3 * * *0
Sat *4 Sep * *S * * SI * S *SI *WC * *1 * * * 4 * * *0
Sun *5 Sep *LRS * * SI *SI * S *SI * *0 * * * 3 * * *0 !
Mon *6 Sep * HR * * HR LRS *SI *SI * *1 * * * 2 * * *1
Tue *7 Sep *HRS * *HRS HRS *HR *SI * *2 * * * 2 * * *2
Wed *8 Sep * *D * * LR LRS HRS HRS * *0 * * * 3 * * *0 !
Thu *9 Sep * SI * * *S *SI *SI HRS * *2 * * * 3 * * *0
Fri 10 Sep * GC * * GC *WC *SI *LR * *1 * * * 3 * * *1
Sat 11 Sep * SI * * LR *SI *LR *HR * *1 * * * 4 * * *0
Sun 12 Sep * *S * * SI *SI * S * S * *2 * * * 2 * * *0
Mon 13 Sep * SI * * SI *SI *SI * S * *3 * * * 1 * * *3
Tue 14 Sep * LR * * LR *LR *HR *LR * *3 * * * 2 * * *2
Wed 15 Sep * SI * * *S * S *SI *SI * *2 * * * 2 * * *0
Wed 15 Sep * SI* * * S * S *SI *SI * *2 * * * 2 * * *0
Fri 17 Sep * *S * * GC *WC *SI * S * *1 * * * 4 * * *0
Sat 18 Sep * SI * * SI *SI *HR *SI * *3 * * * 2 * * *2
Sun 19 Sep * SI* * *LR *LR * S *HR * *0 * * * 3 * * *0 !
Mon 20 Sep * SI* * *SI *SI *SI * S * *3 * * * 1 * * *3
Tue 21 Sep * SI* * *SI * S *LR * S * *1 * * * 3 * * *1
Wed 22 Sep * *S * * *S * S * S LRS * *3 * * * 1 * * *3
Thu 23 Sep *HRS * *HRS HRS LRS LRS * *2 * * * 1 * * *2
Fri 24 Sep *HRS* * HRS *LR HRS * S * *2 * * * 3 * * *1
Sat 25 Sep * *S * * SI LRS *SI *GC * *0 * * * 4 * * *0 !
Sun 26 Sep * SI * * GC *SI LRS *GC * *1 * * * 4 * * *0
Mon 27 Sep * SI* * HRS *GC *GC LRS * *0 * * * 3 * * *0 !
Tue 28 Sep * GC * * SI *SI *WC *SI * *0 * * * 3 * * *0 !
Wed 29 Sep * LR * * HR *HR *LR *GC * *1 * * * 3 * * *0
Thu 30 Sep * SI * * *S *SI *SI * S * *2 * * * 3 * * *0

For last 30 days: avg 2.50 different forecasts per day
On average forecasted 0.83 days ahead
Correct 4 days ahead: 1 times
Correct 3 days ahead: 4 times
Correct 2 days ahead: 8 times
Correct 1 day ahead: 12 times (40.0%)
Number of times the weather was same as yesterday(*): 7 times (23.3%)
Number of days every forecast was wrong(!): 7 times (23.3%)

Key:
* D: * * * * * * Drizzle *1 occurrences, predicted * 0 times under-forecast
*GC: * * * * *Grey Cloud *2 occurrences, predicted * 8 times about right
*HR: * * * * *Heavy Rain *1 occurrences, predicted * 8 times over-forecast
HRS: * Heavy Rain Shower *3 occurrences, predicted *10 times about right
*LR: * * * * *Light Rain *2 occurrences, predicted *12 times over-forecast
LRS: * Light Rain Shower *1 occurrences, predicted * 8 times over-forecast
* S: * * * * * * * Sunny *7 occurrences, predicted *26 times about right
*SI: * * Sunny Intervals 13 occurrences, predicted *43 times about right
*WC: * * * * White Cloud *0 occurrences, predicted * 5 times over-forecast

Sorry, but have I missed something? Forecasts by who? Are you saying
that the UKMO forecasts are crap?- Hide quoted text -

- Show quoted text -

It's really the kind of thing the MetO should be doing for its
customers. The analysis of model accuracy that is produced by NOAA,
doesn't reflect what happens on the ground and analyses like this do.
I'm always grateful to Pete for doing this, as it takes time and
effort.- Hide quoted text -

- Show quoted text -

I am grateful too.
Although the results look a bit alarming.
Must reflect the difficulty in trying to forecast for a specific
location. Something we all know is a tall order.

Len
Wembury

"Dawlish" wrote in message
news:d54d02f2-3715-457a-9d59-

It's really the kind of thing the MetO should be doing for its
customers.

In terms of the Public Weather Service (PWS) verification relevant to this
thread - extensive verification is carried out for 139 UK locations
throughout the year and form part of the overall Key Performance Targets
(KPTs).

More here http://www.metoffice.gov.uk/corporat...tion/city.html

With the results from 2009/10 here
http://www.metoffice.gov.uk/about-us...ecast-accuracy

Jon.

On Fri, 1 Oct 2010 21:17:46 +0100, Will Hand wrote:

"pete" wrote in message
...
On Fri, 1 Oct 2010 09:29:10 -0700 (PDT), Len Wood wrote:
On Oct 1, 5:24 pm, pete wrote:
These are the 5 day forecasts supplied to the BBC website for my postcode
area.


What is your postcode Pete?

E-mail me if it is a secret!

No it's no secret ....... I know what it is :-)

The link on the BBC website that I source this data from
is http://news.bbc.co.uk/weather/forecast/4276?area=SL7


--
http://www.thisreallyismyhost.99k.or...2110528946.php

In article ,
says...
With the results from 2009/10 here
http://www.metoffice.gov.uk/about-us...ecast-accuracy


What's with the picture? The one marked "A hand writing on a pad with
performance graphic overlaid."

It is so important that we get to enlarge it, so I suspect there must be
relevant information contained within it somewhere. Just looks like a
hand writing on a pad with performance graphic overlaid to me.

--
Alan LeHun

On Sat, 2 Oct 2010 10:01:37 +0100, Jon O'Rourke wrote:
"Dawlish" wrote in message
news:d54d02f2-3715-457a-9d59-

It's really the kind of thing the MetO should be doing for its
customers.

In terms of the Public Weather Service (PWS) verification relevant to this
thread - extensive verification is carried out for 139 UK locations
throughout the year and form part of the overall Key Performance Targets
(KPTs).

More here http://www.metoffice.gov.uk/corporat...tion/city.html

With the results from 2009/10 here
http://www.metoffice.gov.uk/about-us...ecast-accuracy

Jon.

It's worth bearing in mind that I am not measuring how often any
particular forecast comes true, which seems to be what the links
above are concerned with. The best I can do is see how frequently the
forecasts change - since a forecast for 4 days hence is not worth
much if by the next day it's been changed, and then again for the
day after that ...

As I've said before, the basic problem I see with these forecasts
put on the BBC website is that they try to portray too much detail,
too far ahead. For example: there are 7 different descriptions for
wet weather. So whereas it's reasonable to say with a fair degree
of confidence that the weather today will be "Sunny intervals",
that same statement is used to forecast the weather for 4 days in
advance, where something like "probably dry" would better
convey the degree of confidence[1]. Although forecasting anything
as sunny doesn't work for night time, which for 6 months of the
year is the dominant case.

Now I appreciate that when you have a sub-twitter number of characters
to use, it's difficult to come up with anything better than a
"mostly harmless" style summary - but maybe that's part of the
problem, too. It's a difficult path to walk, between worthlessly
vague and misleadingly over-confident.


[1] it would be refreshing to see a few "we simply don't know"
forecasts when any forecast is below a particular quality
threshold, though I can't ever see that happening.