Hi all,

This morning my max/min thermometer showed that last night the temperature
dropped to minus 3 - it was minus 3 at the time I do my observations too
(8am), so when I came home from work I realized that because tonight is
likely to be less cold, I will get a 'false' reading from my max/min
thermometer. It will say the coldest temp in the last 24 hours was minus 3,
but what I really want to know is tonights minimum - I have reset the
thermometer so I can know, but was wondering what the standard convention is
if the minimum (or indeed maximum) temperature coincides with the time of
observations?

Regards,

Jeremy

(Hope this post doesn't get swallowed up by all the excitement!)

Jeremy Handscomb wrote in message ...
: ... was wondering what the standard convention is
:if the minimum (or indeed maximum) temperature coincides with the time of
bservations?

Assuming you record one max. and min. temp. for each period of 24 hours, it
counts twice. Your -3°C was the min. temp. for the 24 hours ending 8 a.m.
today and will be the min. temp. for the 24 hours ending 8 a.m. tomorrow -
unless the temperature has fallen/falls below -3°C before 8 a.m.tomorrow.

Colin Youngs
Brussels

Jeremy Handscomb wrote:
Hi all,

This morning my max/min thermometer showed that last night the
temperature
dropped to minus 3 - it was minus 3 at the time I do my observations
too
(8am), so when I came home from work I realized that because tonight
is
likely to be less cold, I will get a 'false' reading from my max/min
thermometer. It will say the coldest temp in the last 24 hours was
minus 3,
but what I really want to know is tonights minimum - I have reset the

thermometer so I can know, but was wondering what the standard
convention is
if the minimum (or indeed maximum) temperature coincides with the
time of
observations?

Regards,

Jeremy

(Hope this post doesn't get swallowed up by all the excitement!)

The standard convention in most places is that the max and the
min for the previous 24 hrs is read at 0900Z. This isn't possible for
anyone working, particularly during the summer, as that would be 10 am.
Colin Youngs has correctly said that your minimum for the 24 hrs to 8
am tomorrow will be -3°C. It's just too bad, you have to stick to the
system. Alternatively you can adopt a different system, one that I
use, which is to measure the max from 8 am to 8 pm and the min from 8
pm to 8 am the following day. This avoids the problem and also that of
a low max being wiped out by the temperature already being above that
max when you read it the following morning. But there are faults in
this system too in that you will miss a max if it occurs after 8 pm
and, less often, a min after 8 am, both of which are not that uncommon
in the winter. This system leads to the mean diurnal range being less
than that obtained from a 24-hr system, though in summer the difference
is neglible. You have to adopt one system and stick with it despite
the occasional absurdities.

Tudor Hughes, Warlingham, Surrey.

In article , Jeremy Handscomb
writes
Hi all,

This morning my max/min thermometer showed that last night the temperature
dropped to minus 3 - it was minus 3 at the time I do my observations too
(8am), so when I came home from work I realized that because tonight is
likely to be less cold, I will get a 'false' reading from my max/min
thermometer. It will say the coldest temp in the last 24 hours was minus 3,
but what I really want to know is tonights minimum - I have reset the
thermometer so I can know, but was wondering what the standard convention is
if the minimum (or indeed maximum) temperature coincides with the time of
observations?

Regards,

Jeremy

(Hope this post doesn't get swallowed up by all the excitement!)



Hi Jeremy,

Like many I've been with this dilemma myself a few years back. The 24-hr
convention dates back over a century when manual readings were even
difficult to do once a day in some parts of the world and had to be done
at a reasonable time too. Of course for the sake of records this
convention has stuck, nothing will change in that regard. However as you
have experienced it has great big holes in it as far as accuracy is
concerned, you have very nicely highlight this. On the 16th at obs time
you read -3.0C, on the 17th, this a.m you probably have read something
like +1 or 2 degC (like here in Coventry for instance) this was the TRUE
minimum on this day Thursday 17th Feb 2005. But the 24-hour system would
have shown it as a -3.0C for today. ABSOLUTE RUBBISH!!

In real accuracy terms it was indeed rubbish, but in met office protocol
terms it was in fact correct according to the 24 hr format. You have
come across this problem from a temperature point of view, have you
thought about rainfall?? In fact it was my rainfall recording which
really got my beef up. Many a time I was recording rain say for example
this a.m from 0400-0800, this day the 17th. But because of the 0900-0900
convention that rain actually is to be recorded on YESTERDAY'S date,
CRAZY!!
I got so disillusioned from an accuracy point of view I changed as I
know others do also, like Tudor who has responded in this thread to
another time scale. I do my readings from 0900-2100 for max temps, and
2100-0900 for minimum temps. Using this system, MOST of the time you
will have the correct min for example and also the correct max. Of
course this also is not perfect, esp in winter when after a cold spell a
warm front moves in and night time temps are rising to a max after 2100,
but on the whole it is far more accurate than the 24-hour format the WMO
use to compile their statistics.

Most times a 24-hr and a split 12-hr will show exactly the same
readings, in years to come wouldn't it be nice to look back on the 17th
Feb 2005 and see that the min was in fact 1.4C and not the 'official'
false figure of -3.0C which in fact belonged to the day before.

Don't forget you can keep both systems going for a while and see how
many times anomalies occur. My personal pref of course is to use a
split 12-hour format. Sorry if I've gone on a bit here, this was
causing me great moral anguish in times past, recording false data and
for the wrong days record too!

Just my tuppence,

Keiron Carroll
--

In article , Keiron Carroll
writes
In article , Jeremy Handscomb
writes
Hi all,

This morning my max/min thermometer showed that last night the temperature
dropped to minus 3 - it was minus 3 at the time I do my observations too
(8am), so when I came home from work I realized that because tonight is
likely to be less cold, I will get a 'false' reading from my max/min
thermometer. It will say the coldest temp in the last 24 hours was minus 3,
but what I really want to know is tonights minimum - I have reset the
thermometer so I can know, but was wondering what the standard convention is
if the minimum (or indeed maximum) temperature coincides with the time of
observations?

Regards,

Jeremy

(Hope this post doesn't get swallowed up by all the excitement!)



Hi Jeremy,

Like many I've been with this dilemma myself a few years back. The
24-hr convention dates back over a century when manual readings were
even difficult to do once a day in some parts of the world and had to
be done at a reasonable time too. Of course for the sake of records
this convention has stuck, nothing will change in that regard. However
as you have experienced it has great big holes in it as far as accuracy
is concerned, you have very nicely highlight this. On the 16th at obs
time you read -3.0C, on the 17th, this a.m you probably have read
something like +1 or 2 degC (like here in Coventry for instance) this
was the TRUE minimum on this day Thursday 17th Feb 2005. But the
24-hour system would have shown it as a -3.0C for today. ABSOLUTE RUBBISH!!

In real accuracy terms it was indeed rubbish, but in met office
protocol terms it was in fact correct according to the 24 hr format.
You have come across this problem from a temperature point of view,
have you thought about rainfall?? In fact it was my rainfall recording
which really got my beef up. Many a time I was recording rain say for
example this a.m from 0400-0800, this day the 17th. But because of the
0900-0900 convention that rain actually is to be recorded on
YESTERDAY'S date, CRAZY!!
I got so disillusioned from an accuracy point of view I changed as I
know others do also, like Tudor who has responded in this thread to
another time scale. I do my readings from 0900-2100 for max temps, and
2100-0900 for minimum temps. Using this system, MOST of the time you
will have the correct min for example and also the correct max. Of
course this also is not perfect, esp in winter when after a cold spell
a warm front moves in and night time temps are rising to a max after
2100, but on the whole it is far more accurate than the 24-hour format
the WMO use to compile their statistics.

Most times a 24-hr and a split 12-hr will show exactly the same
readings, in years to come wouldn't it be nice to look back on the 17th
Feb 2005 and see that the min was in fact 1.4C and not the 'official'
false figure of -3.0C which in fact belonged to the day before.

Don't forget you can keep both systems going for a while and see how
many times anomalies occur. My personal pref of course is to use a
split 12-hour format. Sorry if I've gone on a bit here, this was
causing me great moral anguish in times past, recording false data and
for the wrong days record too!

Just my tuppence,

Keiron Carroll


Just a follow-up to what I've just written, I must make clear re the
rainfall above that in split obs i.e 0900-2100 & 2100--0900 any rainfall
after 2100 is accredited to the following day!

Keiron
--

Hi guys,

Just wanted to thank you all for your contributions. I think that I am going
to try and take each circumstance when I have issues such as this
individually and consider what's been going on. For instance I have decided
to record the minus 3 deg only once (for the 15th) and allow last night's
minimum of minus 0.5 deg to stand as the minimum for the 24-hour period 0800
(16th) - 0800 (17th). I know that this is not accurate to the convention,
but for my own personal records, I feel that I would like to know that the
temperature didn't fall to minus 3 deg two nights in a row (as Keiron
pointed out). Thanks for your comments too, Colin and Tudor - very helpful
and informative indeed! Here's to some interesting statistics in the coming
week!

Kind regards,

Jeremy

"Jeremy Handscomb" wrote in message
...
Hi all,

This morning my max/min thermometer showed that last night the temperature
dropped to minus 3 - it was minus 3 at the time I do my observations too
(8am), so when I came home from work I realized that because tonight is
likely to be less cold, I will get a 'false' reading from my max/min
thermometer. It will say the coldest temp in the last 24 hours was minus
3, but what I really want to know is tonights minimum - I have reset the
thermometer so I can know, but was wondering what the standard convention
is if the minimum (or indeed maximum) temperature coincides with the time
of observations?

Regards,

Jeremy

(Hope this post doesn't get swallowed up by all the excitement!)

In article ,
Jeremy Handscomb writes:
For instance I have decided
to record the minus 3 deg only once (for the 15th) and allow last night's
minimum of minus 0.5 deg to stand as the minimum for the 24-hour period 0800
(16th) - 0800 (17th). I know that this is not accurate to the convention,
but for my own personal records, I feel that I would like to know that the
temperature didn't fall to minus 3 deg two nights in a row (as Keiron
pointed out).

Why not maintain two sets of data so you can record it both ways, and
get the best of both worlds as it were? Or would that be too much work?
--
John Hall "[It was] so steep that at intervals the street broke into steps,
like a person breaking into giggles or hiccups, and then resumed
its sober climb, until it had another fit of steps."
Ursula K Le Guin "The Beginning Place"

Just a follow-up to what I've just written, I must make clear re the
rainfall above that in split obs i.e 0900-2100 & 2100--0900 any
rainfall
after 2100 is accredited to the following day!

Keiron
--




Now *that* is definitely wrong and there is no justification for
it and will lead to your records not being comparable with others
nearby, or anywhere. It would not be acceptable if you sent your
records to COL. At least with max's and min's we are measuring two
different types of temperature for which there is a plausible night/day
difference but rainfall is just all rainfall and should be measured at
the standard time, or as close to it as you can get. Of course you may
keep a private record in the manner described but anything "published",
in the broadest sense, should be measured once a day, at 0900 or as
near as practicable.

Tudor Hughes, Warlingham, NE Surrey, 556 ft.