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The Diablo wind is created by the combination of strong inland high pressure at the surface, strongly sinking air aloft, and lower pressure off the California coast. The air descending from aloft as well as from the Coast Ranges compresses as it sinks to sea level where it warms as much as 20 °F (11 °C), and loses relative humidity.
Diablo, a Spanish word which translates to devil in English, is also the name of a mountain in Contra Costa County, which is where these winds originate."Mount Diablo is an actual mountain peak ...
The wind profile power law relationship is = where is the wind speed (in metres per second) at height (in metres), and is the known wind speed at a reference height .The exponent is an empirically derived coefficient that varies dependent upon the stability of the atmosphere.
The wind triangle is a vector diagram, with three vectors. The air vector represents the motion of the aircraft through the airmass. It is described by true airspeed and true heading. The wind vector represents the motion of the airmass over the ground. It is described by wind speed and the inverse of wind direction.
"Diablo wind" is the local name for hot, dry winds from the northeast that sometimes hit the San Francisco Bay area and central coastal of California, especially in the spring and fall.
Roughness length is a parameter of some vertical wind profile equations that model the horizontal mean wind speed near the ground. In the log wind profile, it is equivalent to the height at which the wind speed theoretically becomes zero in the absence of wind-slowing obstacles and under neutral conditions. In reality, the wind at this height ...
Then the average wind direction is given via the four-quadrant arctan(x,y) function as θ a = arctan ( c a , s a ) . {\displaystyle \theta _{a}=\arctan(c_{a},s_{a}).} From twenty different functions for σ θ using variables obtained in a single-pass of the wind direction data, Yamartino found the best function to be
Hsu gives a simple formula for a gust factor (G ) for winds as a function of the exponent (p), above, where G is the ratio of the wind gust speed to baseline wind speed at a given height: [28] G = 1 + 2 p {\displaystyle G=1+2p}