You may have noticed that at times rainfall totals in the Almanac section or History page suddenly shift, usually downward. That’s because the automatic rain gauge runs a little wet. Oftentimes, I circle back and correct the amount with what I’ve measured in the manual gauge (~ 6′ away and 3′ lower).
Well, through the wonders of technology (a.k.a. Microsoft Excel), I was able to finally calculate the error and program a correction for it. Over the last 12″ of rainfall, it’s a pretty consistent 4-8% overage. It averages out to +6.5%. So I am subtracting that from realtime readings now. I’ll keep an eye on it to see if it changes over time.
For small events, it may not have any effect whatsoever. But in larger rain storms, it should allow for fewer corrections and, thus, less confusion.