Wind gradient

[Paddington]

We have a Davis weather station mounted four foot above our garage roof and wondered if, in the recent gales we are getting a correct windspeed?

We are at the bottom of a three hundred foot valley and the garage like most of our buildings is built into the side of the hill so six feet to one side of the weatherstation its height becomes ten feet above ground which I think is the recommended height, but going up the hill by the same amount the height of the weatherstation decreases to around six feet. Is there any rule of thumb for correcting windspeed with measurement height?
There are higher barns but the garage roof gives a line of sight to the kitchen where the console is situated.

 

[ukmoto]

Always difficult to get the correct readings, especially when in a valley etc. Do you have any other official/unofficial weather stations near you to compare ? I don't know about other software, but I use Cumulus wherein you can apply a multiplier to rain and wind values to aid correction. Same with temp etc. Don't forget you need to apply corrections for altitude, but that won't affect much except pressure. Here's mine online:

http://landrakemotoparc.com/weather/index.htm

and a realtime (10 secs update):

http://landrakemotoparc.com/weather/CumulusRealtime.html You may have to let your computer install MS Silverlight for this one, but it's interesting to see the gauges swing, especially in this weather.

Do you have the Vue or Pro2 as a matter of interest?

 

[MrNoo]

You will always get inaccurate data when on the side of a hill or in a valley, mainly depending which way the wind is blowing and any curlover/turbulence

 

[Paddington]

Always difficult to get the correct readings, especially when in a valley etc. Do you have any other official/unofficial weather stations near you to compare ? I don't know about other software, but I use Cumulus wherein you can apply a multiplier to rain and wind values to aid correction. Same with temp etc. Don't forget you need to apply corrections for altitude, but that won't affect much except pressure. Here's mine online:

http://landrakemotoparc.com/weather/index.htm

and a realtime (10 secs update):

http://landrakemotoparc.com/weather/CumulusRealtime.html You may have to let your computer install MS Silverlight for this one, but it's interesting to see the gauges swing, especially in this weather.

Do you have the Vue or Pro2 as a matter of interest?

Nearest official weather stations are RAF Shawbury (40miles) and Lake Vyrnwy (40 miles), Shawbury is only 70m ASL and open terrain and we are 250m ASL and very hilly terrain! As you say it seems difficult to compare readings, in the recent gales we were only getting max speeds of 40mph where I thought it should be higher, local radio were quoting 60mph (presumably they were using Shawbury for their data). Perhaps need to look in the Davis Vue manual if I can find it for more info.

 

[einstein]

This might help
http://wiki.sandaysoft.com/a/Wind_measurement#Compensation
standard height for anometer is 10 metres.
Does this mean that when the met office issue wind speed forecasts are these the speed expected at ground level or at 10 metres??

 

[Paddington]

Thanks, Einstein, there is a link for Davis instruments but can't get it to work at the moment.