Recently the Sheiling Tow AWS had been reporting an unusually high frequency of suspected anemometer icing when the SSC Hut and Loch Morlich weather stations were not. An inspection of the weather station on my last visit to the mountain showed that the anemometer cups were no longer spinning freely and was sometimes snagging the wind vane housing - giving the anemometer an abnormally high resistance to be overcome before the cups would spin, greatly increasing the threshold wind at which an actual wind speed would be reported.
The anemometer was swapped out on Saturday (13th March) and replaced by a brand new one. This is not permanently installed until it’s determined if the old one is fixable, reason being not wanting to cut the long wind vane cable to the length needed for this installation unnecessarily as it could render the vane useless for other sites.
Unfortunately the long cable being bundled up is picking up electrical interference, which has been giving some nonsense wind speed readings on Saturday evening. If gust speed or current wind speed is reported far in excess of other recent speeds or those from other AWS’s on the mountain, it is likely to be false. Will try and fix the Sheilings own anemometer and if this is not possible will shorten the cable and permanently install the new one.