Message of the Day

Message of the Day:  CoCoRaHS Blog | Go to end of message

Blowing Rain . . . sideways!

An Alabama observer wrote us several years ago asking: "With the remnants of a tropical storm passing through Central Alabama the rain seems to be blowing sideways so hard that it doesn't "fall" into the rain gauge. Does the size of the rain gauge somehow compensate for this or is there more rain falling than gets measured?”

Great Question! Here's our answer: Strong winds complicate rainfall measurement. It is not the angle of the rain that matters, but the fact that wind will deflect around the gauge (just as air moves around a fast-moving car). As the air is deflected around the gauge, some of the rain that was otherwise headed for the opening of the gauge may bend it's path and miss. To improve gauge catch it is good to have irregular obstacles around the gauge like bushes and shrubs that are approximately the same height as the gauge. Another option is to have the gauge installed close to the ground where the wind speed is lowest will help improve the gauge catch (assuming taller obstacles farther away aren't already blocking the rain).


The current "CoCoRaHS Message of the Day" automatically displays on your screen 
after you enter your daily observation on the data screen.