Waterspout Weather

September 21, 2012

Waterspout moves across the Manitou Passage in the Sleeping Bear Dunes National Lakeshore

Waterspout moves across the Manitou Passage, photo by farlane

I don’t usually blog my own photos to Michigan in Pictures, but yesterday afternoon I had the good fortune to see a waterspout above the Manitou Passage in the Sleeping Bear Dunes National Lakeshore. If you look closely, you can see the turbulence on the water in front of South Manitou Island towards the center.

Meteorologist and Science and Operations Officer Bruce B. Smith of the National Weather Service in Gaylord writes the following about Waterspouts:

Persons living in northern Michigan are well aware that the Great Lakes have a profound impact on local weather patterns. Examples include heavy lake effect snows in winter, and cooling lake breezes in summer. As the end of the summer season approaches, another type of unique Great Lakes weather phenomena is possible — the waterspout.

Dr. Joseph Golden, a distinguished waterspout authority with the National Oceanic and Atmospheric Administration (NOAA), defines the waterspout as a “funnel which contains an intense vortex, sometimes destructive, of small horizontal extent and which occurs over a body of water.” The belief that a waterspout is nothing more than a tornado over water is only partially true. The fact is, depending on how they form, waterspouts come in two types: tornadic and fair weather.

Tornadic waterspouts generally begin as true tornadoes over land in association with a thunderstorm, and then move out over the water. They can be large and are capable of considerable destruction. Fair weather waterspouts, on the other hand, form only over open water. They develop at the surface of the water and climb skyward in association with warm water temperatures and high humidity in the lowest several thousand feet of the atmosphere. They are usually small, relatively brief, and less dangerous. The fair weather variety of waterspout is much more common than the tornadic.

He says that waterspouts occur most frequently in northern Michigan during the months of August, September, and October, when the waters of the Great Lakes are at their warmest and cold air moves in. If a spout develops, you can expect it to move at 10 to 15 knots (5-8 MPH make that 11-17 MPH) and last from two to twenty minutes. How about the 5 stages of waterspout formation from Dr Golden? Why not:

  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.

Click through for more including how the NWS forecasts tornados and also see this Michigan in Pictures post from 2008 with some more Great Lakes Waterspouts.

Check this out on black and see more in my surprisingly cool You Can’t Change the Weather slideshow. I also captured a three waterspouts over North Manitou Island in September of 2008. Click the link to get it background big.

More weather on Michigan in Pictures.

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