WRAL WeatherCenter Blog

I recently bought a rain gauge and I am curious if it is similar to what you use. It is a glass tube about 5 inches long and 1/2 inch wide and is marked in 1/4 inches. I live in Garner and it always seems to measure more than what the weather bureau says we had. As of 3 PM today, (Dec 26) it measured 4 inches of rain. I am curious if we are just getting more rain lately than Raleigh, or if the gauge is inaccurate.

Posted December 29, 2007 12:34 p.m. EST

MIKE MOSS SAYS:         Mike,     That is a very small gauge compared to an "official" gauge (the NWS standard gauge has an 8 inch diameter, for example). Also, you don't mention over what period of time the 4 inches you measured was obtained (i.e. are you certain you emptied the gauge after some previous rainfall events?) Assuming you did, it strikes me more as some kind of a location issue than an inaccurate gauge per se. The reason is that very small gauges would often be more subject to undercatch (showing less precipitation than larger gauges) errors due to wind and to outsplash effects than to overcatch errors. You would probably want to make sure your gauge is not in a location where water may be dripping off the edge of a roof or a kink in a tree limb, and that it is not located where water droplets splashing up from surrounding ground or a deck surface, etc around it may find their way into the gauge.

For the date you mentioned, I took a look at precipitation maps based on combined radar and rain gauge estimates for the region, and it did not appear there would be any reason for such a high reading in the Garner area relative to other nearby locations. You can check your readings against other sites across Wake County at this address:

http://www.cocorahs.org/Maps/ViewMap.aspx?state=NC&county=WK

Note that the date can be changed by using the up/down buttons and then clicking "Get Map."