Weather Watch:  Spotting Waterspouts

Waterspouts tend to be associated with rapidly growing cumulonimbus
clouds.  The first sign that a waterspout may be forming is a
light-colored disc surrounded by a dark spot on the water surface.  A
funnel cloud may or may not be visible during the early stages of the
waterspout.  Later, a mature waterspout, a complete funnel cloud from
water surface to cloud base, forms a spray ring around the dark spot.
The waterspout usually dissipates once cool downdrafts form from a
nearby rain shower.  Although most waterspouts don't cause any damage
since they tend to occur over open water, boaters and paddlers should
avoid being in the path of a waterspout by being weatherwise.

-David Schultz, NOAA/National Severe Storms Laboratory