Deriving Basic Wind Speed from a 3-Second Gust Measurement
Sustained wind speeds and 3-second gusts are the two ways wind gets reported. In a forecast line like "Winds out of the southwest at 25 mph with gusts of up to 40 mph," the 25 mph figure represents the sustained speed, while 40 mph is the measured 3-second gust. Building codes, particularly along southern coastlines where structures must endure hurricanes, rely on both 3-second gust and sustained wind speeds as input variables.
By Avery Morgan4 steps
Gulf Coast building codes require standards that account for both sustained wind speeds and 3-second gust wind speeds.
Sustained wind speeds and 3-second gusts are the two ways wind gets reported. In a forecast line like "Winds out of the southwest at 25 mph with gusts of up to 40 mph," the 25 mph figure represents the sustained speed, while 40 mph is the measured 3-second gust. Building codes, particularly along southern coastlines where structures must endure hurricanes, rely on both 3-second gust and sustained wind speeds as input variables.
Step 1
Visit the National Weather Service website and enter your zip code to obtain the 3-second gust speed. The forecast appears on the site, and when predicted winds exceed 20 mph, gust speeds are shown alongside. During a weather emergency, emergency radio carries broadcasts of both gust and sustained wind speeds.
Step 2
If the 3-second gust exceeds 90 mph, subtract 20.
Step 3
If the 3-second gust is 90 mph or less, subtract 15 from the result.
Step 4
Completing either step 2 or step 3 leaves you with the basic wind speed. This value helps determine whether the building you are constructing (or currently inside of) can be expected to survive the wind you are experiencing without major structural damage. The National Weather Service offers guidance on basic wind speeds and degrees of hurricane proofing for a structure.
