Hydra Home FAQ

Wind direction codes

Wind direction is reported in units of 10 degrees, starting from 10 to 360. The wind direction is always an average over the last 10-min preceding the full hour. There are two special codes: 0 and 990. Code 0 applies to calms. You may find records, however, with non-zero wind speed and direction 0 for the following reason. The wind speed at our web site is computed from the hourly averaged wind speed (FH). The wind direction, however, is averaged only over the last ten minutes preceding the full hour. If the wind speed in that period (FF) is zero, then the wind direction will be zero as well. The hourly averaged wind, however, is not necessarily zero. Code 990 applies to variable wind direction. This means that the standard deviation is larger than 30 degrees.