I own the Weatherflow system and it too had the same problem with wind speed under heavy rain. However a modification was made to the surface of the plate right below the ultrasonic sensors. The problem is now totally gone in heavy rain. Winds are accurate under any condition. So the issue is that the plate under the sensors is often very smooth. Weatherflow went to a rough texture that solved the issue.
However accurate rainfall is another story. This is still almost useless.
I had a weatherflow station too. My first anemometer failed badly after a month. A second was sent out and then the problems started with rainfall. A third ultrasonic anemometer was sent out to me for free with the new hydrophilic coating added it. It started off OK, and then the same problem occurred on that too. You can see my posts about it on their forum. In the end, I got fed up with it and sold everything on eBay.
I certainly won't back their new system, as I believe they've gone backwards with it.
Their customer service is excellent, but if you take a look at forum reports, they sent out A LOT of replacements due to failures.
I'd agree their customer service is second to none. Very nice people to deal with and I value that. Where I disagree with you is I think they're making every attempt to improve their product and I've seen it first-hand. Weather seals on the Sky's solar accessory have been improved and new units are not prone to water intrusion. This is reflected in the design of the upcoming Tempest unit.
There was an issue that I had with the Air. I pointed this out to them and it involved a correlation between temperature and barometric pressure that shouldn't have been. As temperature increased, barometric pressure rose rapidly in direct response. This resulted in wild pressure fluctuations that were extremely inaccurate. Not all units were impacted, but when I pointed it out to them they did go back to the manufacturer who addressed it and the new units no longer have the problem. My replacement unit is performing flawlessly.
Otherwise all other parameters are matching very well with my FA Davis VP2. In fact humidity measurements on the Air are better than my Davis, as my Davis is affected by the well-known issue with Davis humidity sensors that are not handled properly during manufacture. My wind measurements are also better on the Sky than they are on the Davis since the new surface coating was introduced on the Sky. The Sky picks up quick gusts as well as low level winds that are both often missed entirely by the Davis.
The only problem I have remaining with my WeatherFlow is the rain measurements. At this point it looks like it's inherent in the ultrasonic design, at least as it's implemented in the Sky. I wish, as do many other owners, that they would offer a tipper that could be integrated into the system. That would make the system near perfect. We'll see if there is any improvement in this area with the Tempest.
I have backed them for the new Tempest unit as I believe in the company. I'm looking forward to its introduction. From what I've seen, even the current Sky/Air units are more accurate for most parameters than the Ambient/Ecowitt/Fine Offset units. I find a stated accuracy of +/- 2 degrees to be unacceptable at this price point. The barometric pressure accuracy also seems to be significantly worse on these units (+/- .08" Hg) than the WeatherFlow.
I also tend to value more frequent wind updates on the WeatherFlow system than the new Ultrasonic Ambient/Ecowitt units. With all that said, I'd give these new units a look if the reports here are good and the specs are simply very conservative and the actual accuracy turns out to be much better. I've always got an open mind, willing to explore new units, since weather is a hobby and is actually my education.
