How to get accurate wind speeds
At the Hurricane Research Division (HRD) of the National Oceanographic and Atmospheric Administration (NOAA) on Key Biscayne, Florida, they have dozens of photographs of anemometer installations to demonstrate why all wind speed measurements " are not created equal. ".
Their work underlines the need for accurate weather observations. As a volunteer weather observer we thought you might like the following information.
A new report from the American Society of Testing Materials (ASTM) defines in great detail standard techniques for measuring wind speed.
When discussing siting of wind sensors it says, " The anemometer and wind vane shall be located at a 10 meter (33 ft.) height above level or gently sloping terrain with an open fetch of at least 150 meters (500 ft.) in all directions, with the largest fetch possible in the prevailing wind direction. Compromise is frequently recognized and acceptable for some sites. Obstacles in the vicinity should be at lest ten times their own height distant from the wind sensors."
Unfortunately very few volunteer weather observers possess an isolated thirty foot tower. Roof installations are most common. Wind flow may be influenced by a variety of factors: a sloping roof, vertical surfaces and structures such as chimneys. Sam Houston, of HRD suggests a goal would be to have the anemometer fifteen feet above these elements. While we would all like to position our anemometers in an ideal location the realities of cost, real estate and home construction often makes this difficult.
As proposed in the ASTM standard, we would very much like to incorporate photographs of your anemometer installation in our files. The research group would like one shot looking up, from the ground, at the anemometer. This should show roof shape, chimney etc. If possible, they suggest four additional photographs at ground level. These should indicate wind exposure to the north, east, south and west.
Material may be mailed to Amateur Radio Station WX4NHC % National Hurricane Center, 11691 SW 17 Street, Miami, FL 33165
Please remember to provide all of your information, Name, Address, Email Address, equipment descriptions, etc.
During the last hurricane season many valuable reports were received from observers. The most common cause of missing observations were mast failure and loss of backup power.
We look forward to your support during the Hurricane Season. The Atlantic Hurricane Season runs from June 1 to Nov30.
If you have any questions please contact us at
Thank you for your help,
John McHugh, KU4GY
Amateur Radio and ON-NHC Coordinator
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