Erroneous Wind Gusts and False Rain Reports?

Hi all. Quick question…this morning the Tempest has been acting a little weird. I have gotten a few rain reports but its mostly sunny with no rain. It is also reporting wind gusts into the mid-40’s mph. While it is a bit breezy here today, it is probably only gusting into the mid 20’s mph. Could both of these issues be caused by the dreaded pole vibration issue? The tempest has been up for a week and this is the first time this has happened. Thanks!

This may be a lengthy list. . .but check for ideas and images at: Rain sensor and vibrations

This may help give you some ideas of how to mitigate “wind-induced” vibrations / oscillations that produce bogus rainfall.

This location may help too: http://community.weatherflow.com/t/data-wind-speed-direction/4730/102

P.S. I like your icon. . .I recognize both items. . .one inside the other. You’re located about 150 miles NE of my station in Bellevue, Nebr.

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because it uses ultrasonic waves to measure the wind speed instead of cups it might record higher wind gust. Cups need to get up to speed, ultrasonic measurement is instantaneous.

To follow up on sunny’s post above. . .look at your Tempest. There are 4 ultrasonic sensors under the top cap. These Should Be aligned exactly in a N-S and E-W configuration. When you look at the blue “north” marker on the back of the cap. . . there Should Be an ultrasonic sensor directly above it. That the North sensor. IF that sensor is slightly off (by just a fraction to as much as 30 degrees off either left or right. . . .that will also affect the direction. The north marker provides the correct orientation for the wind direction. . . but if the sensors and the cap are misaligned. . . that will affect the direction. I’ve seen several images where that is the case of Tempest caps that were not aligned properly.

Have you seen that with the production units rather than the field test units?

misalignment is never good, but the OP isn’t about wind direction, but about wind speed. Of course in never hurts to check the orientation of the sensors.

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Thanks for the replies everyone. Yeah, the wind direction is fine…the issue is the wind speed (specifically gusts) and the erroneous rainfall. I suspect the erroneous rainfall is due to pole vibration from the wind. I guess my real question is would pole vibration also cause exaggerated wind gusts as well?

I totally get that the wind sensors will be more accurate / instantaneous with gusts than cup sensors…but I can’t imagine it would almost double the wind gusts…would it? I have gusts into the mid 40’s mph while all the stations around me were consistently in the mid 20s. I also observed the conditions outside during these gusts and they were no where near the mid 40’s.

Thanks again everyone.

cups need time to get to the speed of the gust, and with a short gust, it might not get to the peak. Differences of 15km/h are possible.

Hi everyone. I have an update. I now believe my tempest may be defective.

Yesterday evening I completely replaced my mounting setup. I am now using a 36" long 1" galvanized pipe, filled with sand, and capped at both ends. It is attached to the peak of my roof at the soffit with new TV antenna brackets. I also used rubber tape where the pole meets the brackets to reduce vibration. It literally can’t get any more stable or secure.

Overnight and this morning it reported wind gusts in the 30’s mph, 40’s and even pushing 50. During this time, the actual winds have been calm to 9 mph. Oh and the tempest also recorded rain which is false.

I have submitted a support ticket. Honestly, between having to reset the Tempest already because it stopped reporting to the hub, occasional data loss, and the wind/rain issue…I am disappointed. If a weather station can’t accurately report two of the three main weather attributes (temp, rain, wind), then what’s the point?

If the field test had gone like you have experienced the Tempest would not have been released yet. There is definitely something amiss with your Tempest. WF support will take care of you.

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Update. Pretty impressed with WeatherFlow customer service. I submitted a help ticket five days ago explaining the issue and I received a replacement Tempest today. Impressive! It already seems like the wind measurements are much more realistic!

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Since receiving my production Tempest I have noticed strange erroneous high wind gusts after the rain has ended during light winds. We had very intense rain for a short duration (0.45" in a 15 minute period around 10 pm last evening). Below are the wind graphs from the production Tempest versus the beta Tempest. The beta was clearly correct as we have light winds. The problem seemed to get worse near sunrise…we had no winds mixing down as they sometimes do at sunrise…light winds the whole time. Not sure if moisture from the rain perhaps in the sonic wind cavity may be an issue in my production Tempest? Thoughts?

Production Tempest:

Beta Tempest:

Closest nearby AWOS report:
image

I’m seeing the same type of erroneous wind readings on my Tempest. In fact, this is the second time I have seen readings that seem to be incorrect - both times after heavy rain showers. In this latest case, I was seeing sustained winds reported in the 3-4 mph range while the real wind was dead calm.

I looked at my Tempest and saw that there was a pool of water on the lower surface where the ultrasonic wind sensors are located. I turned the Tempest on its side and dumped the water. The problem seems to be solved and the wind readings seem much more reasonable.

This seems like a design flaw and I’m wondering why it wasn’t caught during field testing.

There really has been quite a bit of testing on this very issue. The original SKY units had no coating in the wind gap which resulted in false rain, even after the algorithms to discard erroneous readings. I know I sent photos and videos of the wind gap when false readings were recorded. This eventually led to testing various coatings from hydrophilic to hydrophobic. It turned out that the super-hydrophobic coating worked best and that was then applied to all SKY units and eventually the Tempest units when they started field testing them. This means that hundreds, if not thousands, of units have been in the field for a long time. Still, it is possible to miss specific scenarios.

That being said, there are always trade offs with one technology vs another. Spinning cups have the issue of inertia where they cannot react to wind speed changes like a massless device such as a sonic anemometer. Bearings are also a maintenance item. Propeller anemometers have a similar issue. In addition both need a wind vein, which also has inertia. There are other sonic anemometer designs but a quick internet search showed stand-alone units start at around $400 for a design similar to the Tempest and go up from there.

I’m not trying to say there isn’t an issue, just trying to bring some perspective to things. I know where I live, the superhydrophobic coating has nearly eliminated false wind readings, but then there is usually wind blowing enough to blow the water puddles out of the wind gap leaving only small ones which the software can filter out the results of and keep the signal which reflects properly of the lower plate.

I knew my statement was going to raise a spirited response. :wink:

First, I’m a real fan of the Tempest, so let’s get that out of the way. My comment stems from the fact that something seems to have changed from field test units to production. @hlulofs has both a field test Tempest and a production Tempest and one had an issue (production) and one didn’t. What’s changed? Is one lower surface concave and the other convex? I don’t know, but it does seem that there is an issue on at least some of the production units.

LOL, not sure how spirited my response was. I was up 'till too early this morning typing up an app documentation post. It is sort of like programing, I have to get it out before I lose the thoughts.

I was wondering if maybe there was a mold issue as a possibility, too. Another thing might be how level the units are compared to each other. If one is perfectly level and the other is ever so slightly tilted, would that make a difference? If the superhydrophobic coating wasn’t so delicate I’d say put a straight edge across the base plate and check.

EDIT: I wonder if a collection of serial numbers on units with the issue might point to a different production run?

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Here’s another thing. My Tempest lower plate is a little dirty with pollen gunk. I’ve been reluctant to clean it off because of the coating. So, at the very least the surface isn’t as slick as a clean unit, either.

I’m still waiting for the best way to clean that. All I have heard is light spray of water. Once the coating is gone, there is nothing to fix it as it isn’t a user appliable coating. During field testing I used a ceramic nanocoating on one SKY and it reduced the spurious error readings which had to be rejected but it wasn’t as good as the superhydrophobic coating.

I took my Tempest down to see if I could observe any issues. Overall it was in pristine condition but I did notice a slight imperfection on the bottom plate. I little “droplet” of coating sticking up…frozen in place. It is the high spot on the plate…could such a small imperfection cause this? When it rains is this enough for water to collect?

That won’t cause an issue. The software rejects values that aren’t consistent with other ones, which is why small drops aren’t an issue. It is when there is a large puddle that the system can’t determine what is correct and what is not.

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