My tempest regularly lists “clear” when its cloudy. Is there any way to make this more accurate?
the cloud cover isn’t actually measured by the device. It is just the same as the hourly forecast. (unless it detects that it is raining in which case it switches to a full cloudy symbol with some drops of rain). What you are asking for is (at this moment) in fact a better forecast.
also double check if the siting of your Tempest is correct in the app. This influences the forecast you get.
Its hardly more accurate if it says clear when its fully cloudy. Is there a way to manipulate the source data from which tempest draws?
the tempest gets the forecast data based on very computational intensive simulations. Those simulations are not always very precise. Sorry but you cannot influence those simulations directly. Having said that, one of the advantages of the tempest is that weatherflow tries to improve on those simulation results and make a better local forecast for your station. At least that is what they guarantee. How much better is hard to tell, but the answer to your question remains no, you cannot influence it.
Since we live 150 feet from the Pacific Ocean in Laguna Beach we are dealing with micro climates and marine layers often. The same Tempest feeding to wunderground is far more accurate in terms of cloud cover info.