Ask Ellen: How do waterspouts form?


MUSKEGON, Mich. (WOOD) — It can be an eerie scene watching a funnel spanning down from the sky and kicking up spray on the surface of a large lake or sea. West Michigan is no stranger to waterspouts, and one was caught on camera just this past weekend rolling over Muskegon Lake.

Waterspouts come in two varieties: fair weather waterspouts and tornadic waterspouts. Though they can look similar, the way they form is different.

Believe it or not, the first step for a nontornadic waterspout is a dark spot on the water. This dark spot forms even before a funnel can be spotted in the sky. Sometimes nontornadic waterspouts are called “fair weather” waterspouts because they don’t need a strong thunderstorm to form. A fair weather waterspout will start at the surface of the water and climb up to the cloud base due to higher levels of warmth and humidity close to the ground. Usually, because they form in such quiet weather conditions, a fair weather waterspout will not move very fast. They will never produce winds that are stronger than an EF-0 tornado and are usually less than 100 yards wide.

Dr. Joseph Golden, an expert on waterspouts at the National Oceanic and Atmospheric Administration, listed these steps on how a waterspout forms:

  1. Dark spot. A prominent circular, light-colored disk appears on the surface of the water, surrounded by a larger dark area of indeterminate shape and with diffused edges.
  2. Spiral pattern. A pattern of light and dark-colored surface bands spiraling out from the dark spot which develops on the water surface.
  3. Spray ring. A dense swirling annulus (ring) of sea spray, called a cascade, appears around the dark spot with what appears to be an eye similar to that seen in hurricanes.
  4. Mature vortex. The waterspout, now visible from water surface to the overhead cloud mass, achieves maximum organization and intensity. Its funnel often appears hollow, with a surrounding shell of turbulent condensate. The spray vortex can rise to a height of several hundred feet or more and often creates a visible wake and an associated wave train as it moves.
  5. Decay. The funnel and spray vortex begin to dissipate as the inflow of warm air into the vortex weakens.

The other type of waterspout we can see in West Michigan is a tornadic waterspout. This means they form in a similar way to normal tornadoes. Low-level spin inside a thunderstorm will reach down to the ground, creating a funnel and eventually a full column of rapidly rotating air that reaches the surface. When this happens over water, this is considered a waterspout. If the waterspout rolls onto land and survives, it is considered a tornado.

The waterspout that formed over Muskegon Lake on Sunday was a tornadic waterspout. It was created when a strong thunderstorm moved onshore over Lake Michigan to land and happened to track over Muskegon Lake. The rotation was not strong enough to survive once the storm passed over the water and onto dry land.    

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