I am *not* a weather expert and never will be :-)

But - I do have a Davis wireless VP2 weather station. My anemometer is
mounted on a pole above an outbuilding in the garden - 15 ft ? Trees in the
garden but not too near. Although we live at the highest point of our
village, the readings from my anemometer seem *much* lower than the nearest
*proper* weather station - e.g. Humberside says 25 mph - mine says 10 mph.
Also when I go walking on a windy day and get into the fields just ½ mile
away the wind seems *much* stronger than in my garden.

I'm thinking of getting the Wireless anemometer transmitter unit for the
VP2 and mounting the anemometer on the chimney of my house - 40 ft ?.

Worth it or not ?

TIA,
--
Regards,

Hugh Jampton

On 3 Mar, 21:30, Hugh Jampton wrote:
I am *not* a weather expert and never will be :-)

But - I do have a Davis wireless VP2 weather station. My anemometer is
mounted on a pole above an outbuilding in the garden - 15 ft ? Trees in the
garden but not too near. Although we live at the highest point of our
village, the readings from my anemometer seem *much* lower than the nearest
*proper* weather station - e.g. Humberside says 25 mph - mine says 10 mph.
Also when I go walking on a windy day and get into the fields just ½ mile
away the wind seems *much* stronger than in my garden.

I'm thinking of getting the Wireless anemometer transmitter unit for the
VP2 and mounting the anemometer on the chimney of my house - 40 ft ?.

Worth it or not ?

TIA,
--
Regards,

Hugh Jampton

The higher the better, simply put to get you into as free a flow of
air as possible. If you can get it 2 m above the ridge line of your
house, and assuming there are not too many higher obstructions (such
as trees) taller than this, you'll probably find your mean wind speeds
double or even treble, and your gust speeds will be 50% higher.

'Official' sites have the anemometer at 10 m above ground, but ideally
with no obstructions for 10-15x this distance in all directions ...
even up on the roof, you'll probably still be 10-20% below such sites,
but it's arguable that yours is the more representative urban/suburban
measurement than that remote airfield outside the city in any case ...

HTH.

--
Stephen Burt
Stratfield Mortimer, Berkshire

Hugh Jampton wrote:

Name = Huge Hampton?

I am *not* a weather expert and never will be :-)

But - I do have a Davis wireless VP2 weather station. My anemometer is
mounted on a pole above an outbuilding in the garden - 15 ft ? Trees in the
garden but not too near. Although we live at the highest point of our
village, the readings from my anemometer seem *much* lower than the nearest
*proper* weather station - e.g. Humberside says 25 mph - mine says 10 mph.
Also when I go walking on a windy day and get into the fields just ½ mile
away the wind seems *much* stronger than in my garden.

I'm thinking of getting the Wireless anemometer transmitter unit for the
VP2 and mounting the anemometer on the chimney of my house - 40 ft ?.

Worth it or not ?

TIA,

.....................

" You must be spontaneous, with meticulous planning "

" Northern Rock directors should have their arms amputated,
and then they'll really have have their jerk cut out! "

On Mon, 3 Mar 2008 14:31:28 -0800 (PST), wrote:

The higher the better, simply put to get you into as free a flow of
air as possible. If you can get it 2 m above the ridge line of your
house, and assuming there are not too many higher obstructions (such
as trees) taller than this, you'll probably find your mean wind speeds
double or even treble, and your gust speeds will be 50% higher.

'Official' sites have the anemometer at 10 m above ground, but ideally
with no obstructions for 10-15x this distance in all directions ...
even up on the roof, you'll probably still be 10-20% below such sites,
but it's arguable that yours is the more representative urban/suburban
measurement than that remote airfield outside the city in any case ...

Thanks for that Stephen - exactly the kind of advice I was looking for -
much appreciated. Certainly looks as if I'll need it above my roof to get
anywhere near accurate wind speeds.
--
Regards,

Hugh Jampton

On 4 Mar, 18:40, Hugh Jampton wrote:
On Mon, 3 Mar 2008 14:31:28 -0800 (PST), wrote:
The higher the better, simply put to get you into as free a flow of
air as possible. If you can get it 2 m above the ridge line of your
house, and assuming there are not too many higher obstructions (such
as trees) taller than this, you'll probably find your mean wind speeds
double or even treble, and your gust speeds will be 50% higher.

'Official' sites have the anemometer at 10 m above ground, but ideally
with no obstructions for 10-15x this distance in all directions ...
even up on the roof, you'll probably still be 10-20% below such sites,
but it's arguable that yours is the more representative urban/suburban
measurement than that remote airfield outside the city in any case ...

Thanks for that Stephen - exactly the kind of advice I was looking for -
much appreciated. Certainly looks as if I'll need it above my roof to get
anywhere near accurate wind speeds.
--
Regards,

Hugh Jampton

More from Andy Overton's AWS siting guide (full document at below
ref): you might also find this useful when you do come to do the move.

http://myweb.tiscali.co.uk/awsguide/AWS%20Guide.doc

Wind speed and direction

The anemometer and wind vane should be capable of mounting separately
from the screen and raingauge. Some professional AWS do have the
anemometer/ wind vane/ screen/ raingauge mounted on the same mast
assembly around the same height but it is to be noted that it is
intended that this equipment will be used at a well exposed site where
correction can be made. Within the average amateur site any wind
readings from such an assembly are likely to be useless and it cannot
be recommended.

The standard height for meteorological wind measurements is 10 metres
above ground level, but some agricultural or environmental
applications may require the use of lower heights. If there are
obstructions above 8 metres in the vicinity (i.e. closer than 20
metres) the anemometer/ wind vane should be at least 2-3 metres above
them. Both wind speed and direction vary with height above ground
level and any variation from the standard height will cause
significant errors in reading, which may also vary significantly with
wind direction.

Having laid down the standard the vast majority of amateurs will be
quite unable to meet these requirements. In a suburban site, even
were it physically possible to accommodate a 10+ metre high mast with
associated guying, it would likely raise a storm of protest from
neighbours demanding a Planning Application be processed to which they
would object. Reason must prevail and it must be left to individual
judgement as to what an individual thinks will be acceptable to
surrounding residents. The option of mounting to the chimney of the
house is unlikely to be controversial but to give good exposure the
anemometer/ wind vane should ideally still be mounted 2 metres or more
above roof level to avoid turbulent effects from the roof itself. It
should also be borne in mind that extremely hot gases from the chimney
will cause considerable damage to the plastic components and bearings
of an anemometer and wind vane so careful positioning will be
necessary if the chimney is still in use. The disadvantage of chimney
mounting to most people is that professional help will be needed for
installation and for any subsequent maintenance. A well designed,
ground-mounted mast should be capable of lowering by an individual,
possibly with another helper. A possible alternative, depending on
house design, is mounting a pole to the gable end etc., projecting 2
metres or more above roof level. With careful design this should be
capable of installation and lowering without a professional roofer
(depending on your head for heights!). However, most TV aerial/
satellite dish fitting companies will often fit masts and anemometers
for a reasonable fee. There are several issues to consider here and
it must be left to the individual to find the best solution to meet
their individual circumstances.

As with other instruments, it is very important to ensure the
anemometer and wind vane are truly level once fitted as an instrument
off-level will lead to higher than usual anemometer start-up speeds
and a very clear bias in indicated wind direction, especially with
light winds. Careful mounting of roof positioned masts will be
necessary and it may be necessary to have some means of adjustment in
the fixing system to allow for this. Ground mounted, guyed masts can
be made true by careful tensioning of the guy wires.

Hi Hugh

It is very difficult to site an anemometer mast, particularly in a garden
setting, to get representative wind speed readings. The best you can do is
to try to achieve the most exposed position (an effective height so called)
and then apply a correction factor to give a wind speed reading that be
representative of the speed at the standard height of 10m above level
unobstructed surface. Details of the calculations are in the Observer's
Handbook or an internet search under Hellmann's formula might yield some
results. Failing that, a simple solution would be to monitor your wind speed
with Humberside and then work out the correction factor from that.

We have our anemometers positioned above the highest building on the school
site, which also happens to be the highest point above ground level.
However, neighbouring trees still require us to do some 'correcting'.

Remember, maximum gust readings should never be corrected.

Mike

Pitsford Hall weather station
www.northantsweather.org.uk



"Hugh Jampton" wrote in message
. ..
I am *not* a weather expert and never will be :-)

But - I do have a Davis wireless VP2 weather station. My anemometer is
mounted on a pole above an outbuilding in the garden - 15 ft ? Trees in
the
garden but not too near. Although we live at the highest point of our
village, the readings from my anemometer seem *much* lower than the
nearest
*proper* weather station - e.g. Humberside says 25 mph - mine says 10 mph.
Also when I go walking on a windy day and get into the fields just ½ mile
away the wind seems *much* stronger than in my garden.

I'm thinking of getting the Wireless anemometer transmitter unit for the
VP2 and mounting the anemometer on the chimney of my house - 40 ft ?.

Worth it or not ?

TIA,
--
Regards,

Hugh Jampton

On Tue, 4 Mar 2008 20:29:47 -0000, Mike Lewis wrote:

It is very difficult to site an anemometer mast, particularly in a garden
setting, to get representative wind speed readings. The best you can do is
to try to achieve the most exposed position (an effective height so called)
and then apply a correction factor to give a wind speed reading that be
representative of the speed at the standard height of 10m above level
unobstructed surface. Details of the calculations are in the Observer's
Handbook or an internet search under Hellmann's formula might yield some
results. Failing that, a simple solution would be to monitor your wind speed
with Humberside and then work out the correction factor from that.

We have our anemometers positioned above the highest building on the school
site, which also happens to be the highest point above ground level.
However, neighbouring trees still require us to do some 'correcting'.

Remember, maximum gust readings should never be corrected.

Thanks for that Mike - even more complicated than I thought :-)
--
Regards,

Hugh Jampton

On Tue, 4 Mar 2008 11:01:29 -0800 (PST), wrote:

More from Andy Overton's AWS siting guide (full document at below
ref): you might also find this useful when you do come to do the move.

http://myweb.tiscali.co.uk/awsguide/AWS%20Guide.doc

Wind speed and direction

snipped but read - quite a few times

Thanks again Stephen. My chimney is not in use so no problems there. I
don't like heights so a professional aerial installer *will* be needed.
I'll go on thinking about it for a couple of weeks. If I do go ahead then
expect very light winds for a few months :-)
--
Regards,

Hugh Jampton