Local wind conditions

Wind data and offshore wave data are modeled using a 3-parameter Weibull distribution, and probabilities of exceedance are calculated for 30º sectors. Wind waves are calculated using SINTEF’s software HSCOMP, and wind waves are assumed to occur only when the local wind occurs. Wind speeds are adjusted as follows:

1. Adjustments for duration of storms vs duration of measurements; the stated wind speed is the expected highest 10 minute mean wind speed to occur during a storm of three (3) hour duration

2. For calculation of wind waves, the wind speed is adjusted to reflect the required duration for the stated wave height to develop (duration taken at 50 years return period)

3. A manual adjustment of wind speeds based on an assessment of the local topography

4. An (optional) adjustment of wind directions, where the wind is allowed to alter direction category in a conservative direction; i. e. the wind speed assigned to one direction is the maximum of the calculated wind speeds of itself and its two neighboring directions.

The assumed distribution of extreme winds at Gamneset is shown in below figure: