When waterspouts have been detected by Doppler Radar or reported by local law enforcement or spotters, the NWS issues a Special Marine Warning. The NWS strives to provide this information to the public 12 to 24 hours prior to waterspout occurrence. Once the NWS has determined that waterspouts are possible, the threat is outlined in the Nearshore Marine Forecast and Hazardous Weather Outlook. What forecasts and warnings are issued by the National Weather Service to warn of waterspouts? Waterspouts become favorable when water temperatures are warm, the air is cold and moist, and wind speeds are relatively light.ģ. Water temperature, air temperature, moisture, and wind speed in the lowest several thousand feet of the atmosphere are among the parameters forecasters assess when determining the likelihood of waterspouts. National Weather Service (NWS) meteorologists consider forecasting waterspouts during the late summer and fall whenever large, cool air masses overspread the waters of the Great Lakes. How does the National Weather Service forecast waterspouts? The funnel and spray vortex begin to dissipate as the inflow of warm air into the vortex weakens.Ģ. 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. Its funnel often appears hollow, with a surrounding shell of turbulent condensate. The waterspout, now visible from water surface to the overhead cloud mass, achieves maximum organization and intensity.
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. A pattern of light and dark-colored surface bands spiraling out from the dark spot which develops on the water surface. 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. Joseph Golden distinguishes five stages of waterspout formation: They tend to last from about two to twenty minutes, and move along at speeds of 10 to 15 knots.ĭr. Waterspout formation typically occurs when cold air moves across the Great Lakes and results in large temperature differences between the warm water and the overriding cold air. Waterspouts occur most frequently in northern Michigan during the months of August, September, and October, when the waters of the Great Lakes are near their warmest levels of the year. The fair weather variety of waterspout is much more common than the tornadic. They are usually small, relatively brief, and less dangerous. 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. Fair weather waterspouts, on the other hand, form only over open water. They can be large and are capable of considerable destruction. Tornadic waterspouts generally begin as true tornadoes over land in association with a thunderstorm, and then move out over the water. The fact is, depending on how they form, waterspouts come in two types: tornadic and fair weather. 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 following photo is of a waterspout over the Great Lakes.ĭr.
As the end of the summer season approaches, another type of unique Great Lakes weather phenomena is possible - the waterspout. Examples include heavy lake effect snows in winter, and cooling lake breezes in summer.
Persons living in northern Michigan are well aware that the Great Lakes have a profound impact on local weather patterns.
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