If air isn't currently moving it obviously doesn't have a current direction of movement, so to report a current direction of movement would be wrong. It is extremely rare for outdoor air to not be moving, but not so rare for it to be moving at speeds that are too slow to be measured by ordinary weather station sensors. There are different degrees of "wrong ways" to report wind direction in those "not-so-rare" cases.
Wind that is varying between "too slow to measure" and "barely fast enough to measure" is more apt to continue moving generally in the same direction it was moving at a last measurement than in any other direction, so reporting the last known direction during speed measurement gaps, though wrong in the sense that speed wasn't measured, is a reasonable guess and far "less wrong" than reporting some arbitrary direction, such as North. Furthermore, wind speed and direction are measured by different sensors. A direction sensor may still be reporting accurately at speeds too low for a speed sensor to measure, so is it reasonable to assume direction sensor data is wrong merely because a speed sensor wasn't sensitive enough to measure the speed? The SteelSeries wind-gauge has a data-field labeled "Latest". The meaning of "latest" is different than "current", such as in "What is the latest information about the suspect's heading?" To arbitrarily report a suspect is moving from North to South when his current heading is unknown would be misleading and absolutely wrong. However, reporting the latest information known about his movement, such as "last seen heading East," wouldn't be wrong, even though he might now be moving in some other direction. The same is true for the wind gauge. Reporting the wind as coming from North when the direction isn't known is misleading and absolutely wrong, because there is no reasonable basis to believe it is true. Reporting the latest known direction is "far less wrong," because it is the best guess of current direction and the data display is labeled "Latest" (*information*). Bob -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
