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Old September 15th 18, 06:25 AM posted to uk.sci.weather
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Default Conflicting forecasts

The Met Office forecast for the Peak District for Tuesday issued this
morning reads

------------------------------------------------
A yellow warning has been issued as Storm Helene moves northeast over
the UK. She will bring a risk of very strong winds with severe gale or
storm force winds over the hills and coupled with prolonged spells of
heavy rain and extensive low cloud. Drier and brighter conditions with
easing winds will follow.
------------------------------------------------

Despite this, the Peak District is not included in the current yellow
warning area.

A further conflict is that the current automated forecast for Tideswell
predicts a dry day on Tuesday with no more than Force 4-5 winds.

I appreciate the great uncertainty at this stage but I don't know what
Joe Public would make of all the conflict in the forecasts. Anyone who
relies on only one of the forecasts could end up being very badly
misinformed.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.

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Old September 15th 18, 07:54 AM posted to uk.sci.weather
RJH RJH is offline
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Default Conflicting forecasts

On 15/09/2018 07:25, Norman Lynagh wrote:
The Met Office forecast for the Peak District for Tuesday issued this
morning reads

------------------------------------------------
A yellow warning has been issued as Storm Helene moves northeast over
the UK. She will bring a risk of very strong winds with severe gale or
storm force winds over the hills and coupled with prolonged spells of
heavy rain and extensive low cloud. Drier and brighter conditions with
easing winds will follow.
------------------------------------------------

Despite this, the Peak District is not included in the current yellow
warning area.

A further conflict is that the current automated forecast for Tideswell
predicts a dry day on Tuesday with no more than Force 4-5 winds.

I appreciate the great uncertainty at this stage but I don't know what
Joe Public would make of all the conflict in the forecasts. Anyone who
relies on only one of the forecasts could end up being very badly
misinformed.


As a Joe Public, I have 6 weather apps on my phone. When I can be
bothered, I just do an average and hope. The rest of the time they don't
serve as much more than entertainment.

'Windy' is the best for short-term forecasts and real time info.

--
Cheers, Rob
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Old September 15th 18, 08:03 AM posted to uk.sci.weather
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Default Conflicting forecasts

On 15/09/2018 07:25, Norman Lynagh wrote:
The Met Office forecast for the Peak District for Tuesday issued this
morning reads

------------------------------------------------
A yellow warning has been issued as Storm Helene moves northeast over
the UK. She will bring a risk of very strong winds with severe gale or
storm force winds over the hills and coupled with prolonged spells of
heavy rain and extensive low cloud. Drier and brighter conditions with
easing winds will follow.
------------------------------------------------

Despite this, the Peak District is not included in the current yellow
warning area.

A further conflict is that the current automated forecast for Tideswell
predicts a dry day on Tuesday with no more than Force 4-5 winds.

I appreciate the great uncertainty at this stage but I don't know what
Joe Public would make of all the conflict in the forecasts. Anyone who
relies on only one of the forecasts could end up being very badly
misinformed.


Has anyone seen the algorithm for the auto-generated?
Perhaps its just the modal group, found in the real-world weather for
that day, over the last 10 years in that area.
What is the success rate of the forecast for tomorrow, simply repeating
the weather experienced today?
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Old September 15th 18, 08:09 AM posted to uk.sci.weather
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Default Conflicting forecasts

On 15/09/2018 09:03, N_Cook wrote:



Has anyone seen the algorithm for the auto-generated?
Perhaps its just the modal group, found in the real-world weather for
that day, over the last 10 years in that area.
What is the success rate of the forecast for tomorrow, simply repeating
the weather experienced today?

Back in the 90s it was about 60% IIRC. I would assume that it wouldn't
change all that much. But then using that method would have got nearly
100% during the hot spell!!
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Old September 15th 18, 09:46 AM posted to uk.sci.weather
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On Saturday, 15 September 2018 09:03:52 UTC+1, N_Cook wrote:
On 15/09/2018 07:25, Norman Lynagh wrote:
The Met Office forecast for the Peak District for Tuesday issued this
morning reads

------------------------------------------------
A yellow warning has been issued as Storm Helene moves northeast over
the UK. She will bring a risk of very strong winds with severe gale or
storm force winds over the hills and coupled with prolonged spells of
heavy rain and extensive low cloud. Drier and brighter conditions with
easing winds will follow.
------------------------------------------------

Despite this, the Peak District is not included in the current yellow
warning area.

A further conflict is that the current automated forecast for Tideswell
predicts a dry day on Tuesday with no more than Force 4-5 winds.

I appreciate the great uncertainty at this stage but I don't know what
Joe Public would make of all the conflict in the forecasts. Anyone who
relies on only one of the forecasts could end up being very badly
misinformed.


Has anyone seen the algorithm for the auto-generated?
Perhaps its just the modal group, found in the real-world weather for
that day, over the last 10 years in that area.

No, it's not a statistical model. It works by being given the starting point of the atmospheric state, and then applying complex mathematics to each grid point in the model atmosphere. For features that are less than a few grid points in size, interpolation and parameterisation is used. In the early part of the forecast, weight is given to current conditions to "nudge" the model solution towards that. The weight decreases quickly in the first hours of the forecast.
Note that this is a very simplified explanation - but the key point is that it doesn't involve historical statistics for individual timesteps.

--
Freddie
Ystrad
Rhondda
148m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/YstradRhonddaWx for hourly reports (no wind measurement currently)


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Old September 15th 18, 06:35 PM posted to uk.sci.weather
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Default Conflicting forecasts

Norman Lynagh wrote:

The Met Office forecast for the Peak District for Tuesday issued this
morning reads

------------------------------------------------
A yellow warning has been issued as Storm Helene moves northeast over
the UK. She will bring a risk of very strong winds with severe gale or
storm force winds over the hills and coupled with prolonged spells of
heavy rain and extensive low cloud. Drier and brighter conditions with
easing winds will follow.
------------------------------------------------

Despite this, the Peak District is not included in the current yellow
warning area.

A further conflict is that the current automated forecast for
Tideswell predicts a dry day on Tuesday with no more than Force 4-5
winds.

I appreciate the great uncertainty at this stage but I don't know what
Joe Public would make of all the conflict in the forecasts. Anyone who
relies on only one of the forecasts could end up being very badly
misinformed.



The latest forecast for the Peak District for Tuesday, issued at 1729
this evening reads as follows

------------------------------
Very windy with southerly or southwesterly gales, perhaps severe,
slowly easing. Otherwise rather cloudy start with outbreaks of rain
then brighter, mainly dry afternoon. Freezing level above the summits.
------------------------------

Yet we are still outside of the yellow warning area for strong winds.

Either the forecast will br right, or the warning will be right or
neither will be right. They cannot both be right.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
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Old September 15th 18, 09:59 PM posted to uk.sci.weather
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Default Conflicting forecasts

On Saturday, September 15, 2018 at 7:35:32 PM UTC+1, Norman Lynagh wrote:
Norman Lynagh wrote:

The Met Office forecast for the Peak District for Tuesday issued this
morning reads

------------------------------------------------
A yellow warning has been issued as Storm Helene moves northeast over
the UK. She will bring a risk of very strong winds with severe gale or
storm force winds over the hills and coupled with prolonged spells of
heavy rain and extensive low cloud. Drier and brighter conditions with
easing winds will follow.
------------------------------------------------

Despite this, the Peak District is not included in the current yellow
warning area.

A further conflict is that the current automated forecast for
Tideswell predicts a dry day on Tuesday with no more than Force 4-5
winds.

I appreciate the great uncertainty at this stage but I don't know what
Joe Public would make of all the conflict in the forecasts. Anyone who
relies on only one of the forecasts could end up being very badly
misinformed.



The latest forecast for the Peak District for Tuesday, issued at 1729
this evening reads as follows

------------------------------
Very windy with southerly or southwesterly gales, perhaps severe,
slowly easing. Otherwise rather cloudy start with outbreaks of rain
then brighter, mainly dry afternoon. Freezing level above the summits.
------------------------------

Yet we are still outside of the yellow warning area for strong winds.

Either the forecast will br right, or the warning will be right or
neither will be right. They cannot both be right.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.


We are in the yellow warning area Norman.
We are warned of very strong winds. No mention of gales.
Presumably the impact on us is likely to be greater than in Tideswell.
Hence no warning for you.
We are a soft lot down here in Devon.
Met Office is down here after all.

Len
Wembury
SW Devon
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Old September 16th 18, 04:14 PM posted to uk.sci.weather
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Default Conflicting forecasts

On Saturday, September 15, 2018 at 10:59:42 PM UTC+1, wrote:
On Saturday, September 15, 2018 at 7:35:32 PM UTC+1, Norman Lynagh wrote:
Norman Lynagh wrote:

The Met Office forecast for the Peak District for Tuesday issued this
morning reads

------------------------------------------------
A yellow warning has been issued as Storm Helene moves northeast over
the UK. She will bring a risk of very strong winds with severe gale or
storm force winds over the hills and coupled with prolonged spells of
heavy rain and extensive low cloud. Drier and brighter conditions with
easing winds will follow.
------------------------------------------------

Despite this, the Peak District is not included in the current yellow
warning area.

A further conflict is that the current automated forecast for
Tideswell predicts a dry day on Tuesday with no more than Force 4-5
winds.

I appreciate the great uncertainty at this stage but I don't know what
Joe Public would make of all the conflict in the forecasts. Anyone who
relies on only one of the forecasts could end up being very badly
misinformed.



The latest forecast for the Peak District for Tuesday, issued at 1729
this evening reads as follows

------------------------------
Very windy with southerly or southwesterly gales, perhaps severe,
slowly easing. Otherwise rather cloudy start with outbreaks of rain
then brighter, mainly dry afternoon. Freezing level above the summits.
------------------------------

Yet we are still outside of the yellow warning area for strong winds.

Either the forecast will br right, or the warning will be right or
neither will be right. They cannot both be right.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.


We are in the yellow warning area Norman.
We are warned of very strong winds. No mention of gales.
Presumably the impact on us is likely to be greater than in Tideswell.
Hence no warning for you.
We are a soft lot down here in Devon.
Met Office is down here after all.

Len
Wembury
SW Devon


How can a wind be very strong if it isn't gale force?
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Old September 16th 18, 04:38 PM posted to uk.sci.weather
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On Sunday, 16 September 2018 17:14:21 UTC+1, wrote:

How can a wind be very strong if it isn't gale force?

Gale force has a strict definition: https://www.metoffice.gov.uk/guide/w...beaufort-scale
So a wind with a mean speed of 33 knots is still very strong but it is not a gale by definition.

--
Freddie
Ystrad
Rhondda
148m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/YstradRhonddaWx for hourly reports (no wind measurement currently)
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Old September 16th 18, 07:12 PM posted to uk.sci.weather
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On 16/09/2018 17:38, Freddie wrote:

Gale force has a strict definition: https://www.metoffice.gov.uk/guide/w...beaufort-scale


I know it's a quibble, but for all its apparent detail that table still
doesn't specify what period the mean speed relates to. I see at least 3
periods in fairly common use, eg:

1 min (NHC for instance; maybe it's used more widely in the US?)

2 mins (isn't this the period typically used for aviation reports -
METARs etc?)

10 mins (UKMO preferred period possibly, but others will be able to
confirm/correct)



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