Yes today is the autumn equinox, and as Carol Kirkwood pointed out on the Breakfast TV weather the start of the 'astronomical' autumn, which to me is much more preferable to the 'meteorological' autumn. They are both 'astronomical' in reality, it's just that in the days before computers it was much easier for climaticians (?) to calculate the mean value for a particular season by adding up just three numbers rather than 90 which entailed a bit more work - well that's my theory. The astronomical season isn't without its problems though, because as you know equinoxes don't always happen on the same day each year, so this year for instance the Autumn equinox starts on the 23rd of September and next year it's the 22nd, and that's why when I generate any seasonal stats that I use a fixed 21st of December, March, June and September as the start of Winter, Spring, Summer and Autumn. In these days of fast computers there is no reason why I shouldn't use the exact date of the equinox to compute seasonal means from my various climate stats though, but although I am a purist when it comes to climate stats I am not that daft!

See blog for a graph of daily CET values, anomalies and spells and a chart grid of UK MSLP analysis for Summer 2015 (21 June - 20 September)

https://xmetman.wordpress.com/2015/0...day-of-autumn/

On Wed, 23 Sep 2015 02:30:27 -0700 (PDT)
xmetman wrote:

Yes today is the autumn equinox, and as Carol Kirkwood pointed out on
the Breakfast TV weather the start of the 'astronomical' autumn,
which to me is much more preferable to the 'meteorological' autumn.
They are both 'astronomical' in reality, it's just that in the days
before computers it was much easier for climaticians (?) to calculate
the mean value for a particular season by adding up just three
numbers rather than 90 which entailed a bit more work - well that's
my theory.

You may be right in it being the lazy solution but it's also the better
one as it matches the seasons better than the astronomical one.

In the northern hemisphere, the maximum temperature occurs near the end
of the third week of July and the minimum near the third week of
January. These are only a few days from the mid-point of the
meteorological seasons.

If the astronomical calendar is used, the middle of summer would be at
the end of the first week of August with mid-winter's day being at the
end of the first week of February. Also, December would be largely an
Autumn month and March would be a Winter one. The astronomical calendar
just doesn't tally with climatological reality.

--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
http://www.scarlet-jade.com/
I wear the cheese. It does not wear me.
Posted with Claws: http://www.claws-mail.org/

On 23/09/15 11:41, Graham P Davis wrote:
On Wed, 23 Sep 2015 02:30:27 -0700 (PDT)
xmetman wrote:

Yes today is the autumn equinox, and as Carol Kirkwood pointed out on
the Breakfast TV weather the start of the 'astronomical' autumn,
which to me is much more preferable to the 'meteorological' autumn.
They are both 'astronomical' in reality, it's just that in the days
before computers it was much easier for climaticians (?) to calculate
the mean value for a particular season by adding up just three
numbers rather than 90 which entailed a bit more work - well that's
my theory.

You may be right in it being the lazy solution but it's also the better
one as it matches the seasons better than the astronomical one.

In the northern hemisphere, the maximum temperature occurs near the end
of the third week of July and the minimum near the third week of
January. These are only a few days from the mid-point of the
meteorological seasons.

If the astronomical calendar is used, the middle of summer would be at
the end of the first week of August with mid-winter's day being at the
end of the first week of February. Also, December would be largely an
Autumn month and March would be a Winter one. The astronomical calendar
just doesn't tally with climatological reality.


And of course, the common name for the winter solstice does not suggest
the beginning of the season given that it is widely known as midwinter
while the summer solstice is midsummer.

All the historical celebrations of seasonal events have the equinoxes
and solstices as mid-points of the seasons. Midsummer is still a major
event worldwide. The festivals are not called that by mistake.

I have not previously heard anyone suggest those points as the
beginnings of seasons not least because they so obviously cannot be.

--
AS
pour encourager les autres

In the northern hemisphere, the maximum temperature occurs near the end
of the third week of July and the minimum near the third week of
January. These are only a few days from the mid-point of the
meteorological seasons.

If the astronomical calendar is used, the middle of summer would be at
the end of the first week of August with mid-winter's day being at the
end of the first week of February. Also, December would be largely an
Autumn month and March would be a Winter one. The astronomical calendar
just doesn't tally with climatological reality.

--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
http://www.scarlet-jade.com/
I wear the cheese. It does not wear me.
Posted with Claws: http://www.claws-mail.org/



'In the northern hemisphere, the maximum temperature occurs near the end
of the third week of July and the minimum near the third week of
January. These are only a few days from the mid-point of the
meteorological seasons.'

------------------------------------------------------------------------
I am not sure this statement is true in general for the N Hemisphere.

For example, Helsinki has on average its lowest temperatures in February.
Even more so the further north you go.

http://www.worldclimate.com/cgi-bin/...24+1102+02974W

Also, people's perception of the seasons varies greatly.
You try telling a Fin in Finland that Spring begins on 1st March or 21st March for that matter.

Len Wood
Wembury, SW Devon

--------------------------------------------------------------------------

"Graham P Davis" wrote in message
news:20150923114125.5ad899d2@home-1...
On Wed, 23 Sep 2015 02:30:27 -0700 (PDT)
xmetman wrote:

Yes today is the autumn equinox, and as Carol Kirkwood pointed out on
the Breakfast TV weather the start of the 'astronomical' autumn,
which to me is much more preferable to the 'meteorological' autumn.
They are both 'astronomical' in reality, it's just that in the days
before computers it was much easier for climaticians (?) to calculate
the mean value for a particular season by adding up just three
numbers rather than 90 which entailed a bit more work - well that's
my theory.

You may be right in it being the lazy solution but it's also the better
one as it matches the seasons better than the astronomical one.

In the northern hemisphere, the maximum temperature occurs near the end
of the third week of July and the minimum near the third week of
January. These are only a few days from the mid-point of the
meteorological seasons.

If the astronomical calendar is used, the middle of summer would be at
the end of the first week of August with mid-winter's day being at the
end of the first week of February. Also, December would be largely an
Autumn month and March would be a Winter one. The astronomical calendar
just doesn't tally with climatological reality.


Well up here on Dartmoor September is the driest month of the year and very
much a summer month. December is a change over month, first half autumn,
second half winter, likewise March which is mostly a winter month. Snowiest
month is February and Junes can be quite cold still with summer not really
starting until the end of June. So the equinoxes fit the seasons quite well
here.

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

This ol' perennial chestnut.

Both the astronomical and the meteorological calendars are not that good
'fit'.

Spring is well under-way by March 21st with it usually starting around
the 3rd week of February (though there's often a 'touch' of spring even
in mid-winter). I think the 1st of March is better suited for spring's
start.

September 1st can hardly be called the start of autumn especially when
you consider that June on average is no warmer than September despite
the longer days and more sunshine.

If you use nature as a guide then it follows along these lines in most
years:
Winter = December to mid-February
Spring = mid-February to mid-May
Summer = mid-May to end of September
Autumn = October to end of November.

Summer being the longest season with autumn the shortest.

As Len says, big differences depending on where you are in the northern
hemisphere; even quite large differences within the British Isles.

In Orkney if felt rather autumnal by mid-August, generally around 6
weeks earlier than here!

--
Nick Gardner
Otter Valley, Devon
20 m amsl
http://www.ottervalley.co.uk

On Wed, 23 Sep 2015 09:13:46 -0700 (PDT)
Len Wood wrote:





In the northern hemisphere, the maximum temperature occurs near the
end of the third week of July and the minimum near the third week of
January. These are only a few days from the mid-point of the
meteorological seasons.

If the astronomical calendar is used, the middle of summer would be
at the end of the first week of August with mid-winter's day being
at the end of the first week of February. Also, December would be
largely an Autumn month and March would be a Winter one. The
astronomical calendar just doesn't tally with climatological
reality.


'In the northern hemisphere, the maximum temperature occurs near the
end of the third week of July and the minimum near the third week of
January. These are only a few days from the mid-point of the
meteorological seasons.'

------------------------------------------------------------------------
I am not sure this statement is true in general for the N Hemisphere.

For example, Helsinki has on average its lowest temperatures in
February. Even more so the further north you go.

http://www.worldclimate.com/cgi-bin/...24+1102+02974W

Also, people's perception of the seasons varies greatly.
You try telling a Fin in Finland that Spring begins on 1st March or
21st March for that matter.


Those dates are correct (within plus or minus 5 days) as an average of
stations in the northern hemisphere which have at least one month per
year with a mean temperature near or below 0C. How do I know that?
Because it's those stations that I used when working out those dates
fifty years ago. Unless global warming has somehow added a delay
factor, I think they should still hold true. ;-)

The reason for +/-5 days is that the dates had to coincide with the last
day of ten-day periods beginning on 1st January. This means that the
date for July should have been the 19th and not the 20th. The reason
for calculating these dates was that we needed fixed dates for the
start of the positive degree-day season after mid-winter and the same
for the negative degree-day season after mid-summer.

--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
http://www.scarlet-jade.com/
I wear the cheese. It does not wear me.
Posted with Claws: http://www.claws-mail.org/

"Graham P Davis" wrote in message
news:20150923114125.5ad899d2@home-1...
On Wed, 23 Sep 2015 02:30:27 -0700 (PDT)
xmetman wrote:

Yes today is the autumn equinox, and as Carol Kirkwood pointed out on
the Breakfast TV weather the start of the 'astronomical' autumn,
which to me is much more preferable to the 'meteorological' autumn.
They are both 'astronomical' in reality, it's just that in the days
before computers it was much easier for climaticians (?) to calculate
the mean value for a particular season by adding up just three
numbers rather than 90 which entailed a bit more work - well that's
my theory.

You may be right in it being the lazy solution but it's also the better
one as it matches the seasons better than the astronomical one.

In the northern hemisphere, the maximum temperature occurs near the end
of the third week of July and the minimum near the third week of
January. These are only a few days from the mid-point of the
meteorological seasons.

If the astronomical calendar is used, the middle of summer would be at
the end of the first week of August with mid-winter's day being at the
end of the first week of February. Also, December would be largely an
Autumn month and March would be a Winter one. The astronomical calendar
just doesn't tally with climatological reality.

--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
http://www.scarlet-jade.com/
I wear the cheese. It does not wear me.
Posted with Claws: http://www.claws-mail.org/



You may find this graph of average daily max/min temperature for the period
1976 to 2005 at Wokingham of interest.

http://www.woksat.info/wwp/graav7605.gif

--
Bernard Burton

Wokingham Berkshire.

Weather data and satellite images at:
http://www.woksat.info/wwp.html



---
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Generally I would say Autumn starts here in September, usually after the first week.
Winter from the last week of November.
March is still a winter month, until maybe the last week.
Spring from end of March until the first week of June.
Having said that, the dates can be fairly flexible as I'm still waiting for summer.

DM. Langtoft. ERofY.

On Wednesday, 23 September 2015 23:23:14 UTC+1, David Mitchell wrote:
Generally I would say Autumn starts here in September, usually after the first week.
Winter from the last week of November.
March is still a winter month, until maybe the last week.
Spring from end of March until the first week of June.
Having said that, the dates can be fairly flexible as I'm still waiting for summer.

DM. Langtoft. ERofY.

David,
Summer started on 30th June and ended 1st July, followed by the customary thunderstorm.
You must have blinked and missed it!
Ken
Copley
Teesdale