I’m just curious... someone posted a link showing the wind speed at various altitudes. Such as 10 meters, 100 meters, 250 meters, 1000 meters etc., and on up to higher altitudes.
It appeared to me that the wind velocity was higher at high altitudes, but not so high at ground level.
Does anybody know... when they say a wind speed of 150 mph, does that mean at ground level, or at high altitude?
There is friction close to the ground. Especially if there is topography and trees.
I would presume that the speeds shown or announced were at ground level. But that means nothing here or there, just my take on it.
A wind speed of 150 kts. or as was recorded yesterday during landfall at Marsh Bay of 185 kts, gust to 220 kts, is measured at essentially ground level. (The height of the anemometer above the ground may be 4 to a 100 feet.)
I remember that a wind gauge broke during Camille in Biloxi/Gulfport back in ‘69 at 200mph and it wasn’t to high up so........
Wind speed 150 MPH is at ground level. The hurricane hunters measure wind speed at various altitudes when they fly into the storm. They use dropsonde to obtain measurements near the surface. They also obtain wind speed at various higher altitudes and extrapolate to the surface wind speed.
It depends on the source.
Most codes depend upon simulation models, which use the “Basic Wind Speed” or “V” as a 3-second gust speed at 33 ft (10m) above the ground in Exposure C (say open countryside grasslands with few scattered obstructions less than 30 ft, say over 1500 ft apart.)
Some codes further stipulate design wind speeds must be made by simulation, vice anemometers in hurricane prone regions.
If reported from an anemometer in an suburban or urban area with obstructions such as trees, poles, towers, bldgs, hills over 30 ft, and taken at ground level, then the 10 meter reading might be 30% greater.
Bldgs such as fire departments and police stations are designed for V=150mph generally throughout the east coast, and upwards of 200mph on the southern tip of Florida.
But if you have a short hill on a plain, the wind speed would increase at the top.