Wind speed run amok

Late yesterday, we had very heavy rain, and around 5:30am this morning, the wind speed went from near zero to about 10 – all 3 values (gust, avg and lull). With little variation, that lasted for a couple of hours, until 9am, when suddenly the gusts went up to 25-30, the avg around 20, and the lull in the upper teens. I did a visual inspection (it is 20’ off the ground) and just noticed lots of water droplets around the sides. Just before 10am, the speeds all dropped to a more reasonable 2-5mph. During the entire time, the actual speed was less than 5mph according to my nearby, old anemometer…

Is it possible water got onto the transducers and messed up the sensing? Or something else? Thanks for any insight!

Yes, unfortunately this is completely possible. The transducers do have a special coating to help stop this from happening, but with heavy rain, light winds, and high humidity, water can interrupt the sonic paths leading to spurious wind speeds. As you saw though, when the water is eventually blown away the readings should return to normal.

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@tomw_mail is this on a SKY or Tempest? If it is a SKY, is it one with the super hydrophobic coating in the wind gap or is it shiny smooth like the rest of the unit?

I took some video showing the behaviour of water on the special coating. This is on a ‘Sky’ but I assume the Tempest will be similar. There is lots of discussion about the problem on this forum, you could use the search to find it. If your pole is easy to give a swing from the ground you might be able to move the water drops and see if the wind reading changes. In very strong wind they get blown off but light wind they can bobble around sitting on the lower surface. Here is one example:


cheers Ian :slight_smile:

gizmoev – this is a Tempest…just installed 2 weeks ago

iladyman – thanks, Ian…interesting stuff – I had hoped to be “maintenance-free”…so it’s on a 10’ pole attached to an unused chimney…not too easy to get at…

During different coating field testing I found that puddling of water, as @iladyman shows, was the main culprit of strange wind behavior. I also found that sometimes a bubble of water would adhere to one of the sonic transducers, creating a lens effect, which would throw things off. The coating on the Tempest is a result of that earlier testing. My SKYs and field test Tempests have largely been maintenance free since the coating but your rain patterns and mine might be one of the differences. Hopefully it doesn’t happen too often for you.