Looks like your getting turbulence from the surrounding tree hence the spinning of the wind director,getting it up higher would cure that.
Yeah,, well If I could do it myself, it would be on the chimney breast with a proper pole, as that square bit of wood the anemometer is screwn on isnt helping things either.
The wind can be blowing in one area and nearby, just a couple of feet away, not blowing at all. I've stood at the base of my anemometers and watched them almost motionless while feeling a strong breeze and the opposite, seeing them spin and not feeling a thing. It's like how rain fall can be so different in close areas.
Yeah the wind is odd, I would of thought with it higher now, it would catch the wind more easily but that doesn't seen to be happening as expected, as quite often the grass, flowers and trees move about nearby, but anemometer either not spinning or doesn't look like its spinning fast enough for the amount of wind. It does get a higher reading now, when it spins in light winds, but the direction still goes mental as "daman" has mentioned.