• waterspout
    Waterspouts are common in warm, humid areas, such as the Bahamas, above.

    Photograph by Patricia Vazquez, MyShot

    Landspout
    A landspout, officially called a "dust-tube tornado," is similar to a waterspout. Unlike a true tornado, landspouts do not form from a mature mesocyclone. Like a waterspout, a landspout forms with a slow-moving (nor not-moving), developing cloud system.

    Snowspout
    In January 1994, a waterspout near Whitby, Canada, off the shore of Lake Ontario, provided a rare example of a snowspout—a waterspout in winter conditions. The air moving over the water to produce snowspouts can be so cold that steam rises from the surface.

    A waterspout is a column of cloud-filled wind rotating over a body of water. 
     
    Despite its name, a waterspout is not filled with water from the ocean or lake. A waterspout descends from a cumulus cloud. It does not "spout" from the water. The water inside a waterspout is formed by condensation in the cloud. 
     
    There are two major types of waterspouts: tornadic waterspouts and fair-weather waterspouts.
     
    Tornadic waterspouts get their start as true tornadoes. Influenced by winds associated with severe thunderstorms, air rises and rotates on a vertical axis. Tornadic waterspouts are the most powerful and destructive type of waterspout. 
     
    Fair-weather waterspouts, however, are much more common. Fair-weather waterspouts are rarely dangerous. The clouds from which they descend are not fast-moving, so fair-weather waterspouts are often static. Fair-weather waterspouts are associated with developing storm systems, but not storms themselves.
     
    Both tornadic and fair-weather waterspouts require high levels of humidity and a relatively warm water temperature compared to the overlying air. Waterspouts are most common in tropical and subtropical waters, such as the Florida Keys, the islands of Greece, and off the east coast of Australia.
     
    There are five stages of waterspout formation:
     
    1. Dark spot. The surface of the water takes on a dark appearance where the vortex, or column of rotating wind, reaches it.
     
    2. Spiral pattern. Light and dark bands spiral out from the dark spot.
     
    3. Spray ring. A swirling ring of sea spray called a cascade forms around the dark spot. It appears to have an eye at the center, similar to that seen in a hurricane.
     
    4. Mature vortex. The waterspout is now at its most intense stage, visible from the surface of the water to the clouds overhead. It appears to have a hollow funnel and may be surrounded by vapor.
     
    5. Decay. When the flow of warm air into the vortex weakens, the waterspout collapses.
     
    The average spout is around 50 meters (165 feet) in diameter, with wind speeds of 80 kilometers per hour (50 miles per hour), corresponding to the weakest types of tornadoes on land. The largest waterspouts can have diameters of 100 meters (330 feet) and last for up to one hour, though the average lifetime is just 5 to 10 minutes. 
     
    The National Weather Service recognizes the dangers posed by waterspouts as part of its "severe local storm" warning list. Waterspouts not only put swimmers and boaters at risk, they also pose a threat to aircraft. Helicopters flying near waterspouts can be damaged and thrown off-course by such intense winds.
  • Term Part of Speech Definition Encyclopedic Entry
    air Noun

    the layer of gases surrounding Earth.

    Encyclopedic Entry: air
    axis Noun

    an invisible line around which an object spins.

    Encyclopedic Entry: axis
    cloud Noun

    visible mass of tiny water droplets or ice crystals in Earth's atmosphere.

    Encyclopedic Entry: cloud
    condensation Noun

    process by which water vapor becomes liquid.

    Encyclopedic Entry: condensation
    correspond Verb

    to match or be similar to.

    cumulus Noun

    type of large cloud with a flat bottom and fluffy tops.

    decay Verb

    to rot or decompose.

    descend Verb

    to go from a higher to a lower place.

    diameter Noun

    width of a circle.

    endanger Verb

    to put at risk.

    eye Noun

    center of a tropical cyclone, characterized by a roughly circular area of light winds and rain-free skies.

    fair-weather waterspout Noun

    column of rotating, cloud-filled wind that forms over water.

    humidity Noun

    amount of water vapor in the air.

    Encyclopedic Entry: humidity
    hurricane Noun

    tropical storm with wind speeds of at least 119 kilometers (74 miles) per hour. Hurricanes are the same thing as typhoons, but usually located in the Atlantic Ocean region.

    lake Noun

    body of water surrounded by land.

    National Weather Service Noun

    branch of the National Oceanic and Atmospheric Association (NOAA) whose mission is to provide "weather, hydrologic, and climate forecasts and warnings for the United States, its territories, adjacent waters and ocean areas, for the protection of life and property and the enhancement of the national economy."

    ocean Noun

    large body of salt water that covers most of the Earth.

    Encyclopedic Entry: ocean
    storm Noun

    severe weather indicating a disturbed state of the atmosphere resulting from uplifted air.

    subtropical Adjective

    bordering the tropics, just north of the Tropic of Cancer and south of the Tropic of Capricorn.

    temperature Noun

    degree of hotness or coldness measured by a thermometer with a numerical scale.

    Encyclopedic Entry: temperature
    thunderstorm Noun

    cloud that produces thunder and lightning, often accompanied by heavy rains.

    tornadic waterspout Noun

    column of rotating, cloud-filled wind that forms as a tornado moves over water.

    tornado Noun

    a violently rotating column of air that forms at the bottom of a cloud and touches the ground.

    tropical Adjective

    existing in the tropics, the latitudes between the Tropic of Cancer in the north and the Tropic of Capricorn in the south.

    vapor Noun

    visible liquid suspended in the air, such as fog.

    vortex Noun

    column of rotating fluid, such as air (wind) or water.

    waterspout Noun

    column of rotating cloud-filled wind that descends to an ocean or lake.

    Encyclopedic Entry: waterspout
    wind Noun

    movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.

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