On Sat, 19 Jan 2008 01:35:17 -0000, "Stuart Brooks"
wrote:

I think it is a great limitation of most (if not all) AWS weather software
interfaces that you are stuck with a non-standardised 00-24 daily cycle,
though perhaps that means it is the new standard....

Remember though that it is often readily possible to analyse your
logged AWS data to generate summary data covering different station
days (eg 09-09 if you wish). I know that a number of people do this
with eg an Excel spreadsheet. I've got a utility that does this
directly for Davis VP/VP2 data and it's a feature offered by some
other third-party software packages.

John Dann
www.weatherstations.co.uk

Stuart Brooks wrote:

I think it is a great limitation of most (if not all) AWS weather software
interfaces that you are stuck with a non-standardised 00-24 daily cycle,
though perhaps that means it is the new standard....

My software, Cumulus, allows the use of an 09z-09z day.
--
Steve Loft
Sanday, Orkney. 5m ASL. http://sanday.org.uk/weather
Free weather station softwa http://sandaysoft.com/

On 19 Jan, 09:09, Paul Hyett wrote:

What is the official way of recording max & mins anyway? Should they
both be read at 9am GMT, and the max ascribed to the previous day,
with
the min to the current day?

Yes - max read at 0900 is 'thrown back' to the previous day (as is
rainfall), the min read at 0900 is entered to the day of reading.

--
Stephen Burt
Stratfield Mortimer, Berskhire

"Paul Hyett" wrote:

... can be a total PITA, as you can never tell what time of day or night
they will occur!

I've always kept separate 09-09 and 09-21-09 figures, and some
time ago I needed to tabulate them, so I now have 25 years' worth
of records for Luton using both methods. The figures below show
day max minus 24h max, and night min minus 24h min (degC):

Month MeanMin MeanMax
Jan -0.55 +0.29
Feb -0.42 +0.15
Mar -0.20 +0.07
Apr -0.05 +0.04
May -0.02 +0.02
Jun -0.03 +0.04
Jul -0.01 +0.02
Aug -0.01 +0.03
Sep -0.08 +0.03
Oct -0.16 +0.06
Nov -0.47 +0.19
Dec -0.60 +0.34
Year -0.22 +0.11

The biggest difference in mean min was -0.94degC in Jan 2001
The biggest difference in mean max was +0.66degC in Jan 1992

Philip

wrote :
On 18 Jan, 20:36, Mike Tullett wrote:
On Fri, 18 Jan 2008 19:39:51 +0000, Trevor Harley wrote:

I really hate it when the temperature soars between 8 and 9 am. Quite
often in winter the maximum is 8.59 a.m. December 21st here was very
cold - a maximum of -2.4C during the day, dropping to -6.8C around 2
am, then climbing rapidly to -1.4C at 8.59, thus spoiling my record
lowest maximum. And there have been several occasions where an
otherwise "frost day" has been ruined by rising temperatures around
dawn (which is 8.45 a.m. here).

The most notable occasion that happened here was in the early 80s. The
daytime max was about -11C but by 0900 next day the temp was up to +3C.

I can remember in the cold spell at the end of January 1972, the
morning of 31 Jan was bitterly cold (my min that morning, in
Warwickshire, was -12.2°C, around 8.30 am). At around a third of
climatological sites in the Midlands, the lowest temperature occurred
a little after the (nominal) 0900 UTC observation, so the minimum
thermometer reading was, following standard practice, credited to the
following morning - i.e. 1 February. However, milder air spread in
quickly during the day on 31 January, and February was a mostly mild
month, resulting in most places seeing their official lowest February
(and annual) minimum occurring ... erm, in January.

snip
I remember that one too! At the time (and until approx 1983) the
MWR tabulated climatological stations with terminal hours of
09-09 alongside synoptic stations with terminal hours of 09-21-09,
leading to apparent huge differences between neighbouring sites -
eg in Nottinghamshire, Watnall -3.4°C and Warsop -13.8°C -
the first recorded overnight 31st/1st, and the second at 09z on
the 31st (presumably).

Philip

"Stuart Brooks" wrote :

For many years figures from Met Office sites were based on 0900-2100 max
and 2100-0900 min (these are still calculated from NCM reports) precisely
to avoid singleton cold nights counting twice. Average differences between
monthly averages worked out from 09-21/21-09 stations and 0909 stations
were as much as 0.7C for December minima, though depending on the
character of the month the figure could be even higher.

The standardisation on 0909 was presumably to make it easy for once a day
stations, though there is no ideal time of day for a reset that would be
valid all year.

In the Monthly Weather Report, MO synoptic (and auxiliary synoptic)
stations were tabulated with 09-21-09 terminal hours from 1945 to
1983 inclusive, but used 09-09 from 1984 until it was so rudely
terminated in 1993.

Before 1945, synoptic stations (or whatever they were called then) used
terminal hours of 18 and 07 (or in some instances 06), but climatological
stations have always been predominately 09-09 though there were more
exceptions in earlier years (some 07-07, 06-06, 18-18, for instance).

Clearly, 09-09 has to be accepted for conventional practice, although
my opinion is that 09-21-09 gives a better feel for the climate of a
particular place. However, there are are still disadvantages with
09-21-09 .... you have to make special arrangements (or be very
careful) when tabulating highest maxes and lowest mins for the
month because these can occur at night (for maxes) and by day
(for mins). Also, a night minimum can easily occur between
sunset and 21z ... something I've noticed very frequently here at
Whipsnade during this particular winter.

Philip

Philip Eden wrote:

"Stuart Brooks" wrote :

For many years figures from Met Office sites were based on
0900-2100 max and 2100-0900 min (these are still calculated from
NCM reports) precisely to avoid singleton cold nights counting
twice. Average differences between monthly averages worked out
from 09-21/21-09 stations and 0909 stations were as much as 0.7C
for December minima, though depending on the character of the
month the figure could be even higher.

The standardisation on 0909 was presumably to make it easy for once
a day stations, though there is no ideal time of day for a reset
that would be valid all year.

In the Monthly Weather Report, MO synoptic (and auxiliary synoptic)
stations were tabulated with 09-21-09 terminal hours from 1945 to
1983 inclusive, but used 09-09 from 1984 until it was so rudely
terminated in 1993.

Before 1945, synoptic stations (or whatever they were called then)
used terminal hours of 18 and 07 (or in some instances 06), but
climatological stations have always been predominately 09-09 though
there were more exceptions in earlier years (some 07-07, 06-06,
18-18, for instance).

Clearly, 09-09 has to be accepted for conventional practice, although
my opinion is that 09-21-09 gives a better feel for the climate of a
particular place. However, there are are still disadvantages with
09-21-09 .... you have to make special arrangements (or be very
careful) when tabulating highest maxes and lowest mins for the
month because these can occur at night (for maxes) and by day
(for mins). Also, a night minimum can easily occur between
sunset and 21z ... something I've noticed very frequently here at
Whipsnade during this particular winter.

Philip

Also here at Chalfont St Giles, Philip. Last night, for example, the
overnight "low" of 11.7 occurred at 1905z.

--
Norman Lynagh
Chalfont St Giles, Buckinghamshire
85m a.s.l.
(remove "thisbit" twice to e-mail)

On Sat, 19 Jan 2008 at 13:09:38, Philip Eden
wrote in uk.sci.weather :

"Paul Hyett" wrote:

... can be a total PITA, as you can never tell what time of day or night
they will occur!

I've always kept separate 09-09 and 09-21-09 figures, and some
time ago I needed to tabulate them, so I now have 25 years' worth
of records for Luton using both methods. The figures below show
day max minus 24h max, and night min minus 24h min (degC):

Month MeanMin MeanMax
Jan -0.55 +0.29
Feb -0.42 +0.15
Mar -0.20 +0.07
Apr -0.05 +0.04
May -0.02 +0.02
Jun -0.03 +0.04
Jul -0.01 +0.02
Aug -0.01 +0.03
Sep -0.08 +0.03
Oct -0.16 +0.06
Nov -0.47 +0.19
Dec -0.60 +0.34
Year -0.22 +0.11

Thanks - that saved me asking which months would be most/least affected.
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

Stuart Brooks wrote:
For many years figures from Met Office sites were based on 0900-2100 max and
2100-0900 min (these are still calculated from NCM reports) precisely to
avoid singleton cold nights counting twice. Average differences between
monthly averages worked out from 09-21/21-09 stations and 0909 stations were
as much as 0.7C for December minima, though depending on the character of
the month the figure could be even higher.

The standardisation on 0909 was presumably to make it easy for once a day
stations, though there is no ideal time of day for a reset that would be
valid all year.

I think it is a great limitation of most (if not all) AWS weather software
interfaces that you are stuck with a non-standardised 00-24 daily cycle,
though perhaps that means it is the new standard....

I must say that, with my VP2, I took the easy way out and told it that
it was in Alaska, GMT-9. So I read the data for the previous day at
09GMT, when the VP2 is telling me that it's midnight. (It curiously
actually calls it '12a' as opposed to noon which it says is '12p'. But
then it is not a Latinist.)

Hugh

--

Hugh Newbury

Running Linux Suse 10.1 in deepest Dorset