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Waterspouts
Mon Aug 15, 2005
Listen in RealAudio 
If it looks like a tornado, sounds like a tornado, and spits out rain like a tornado, it must
be a tornado, right? Well, yes, except if it is a waterspout. Hi, I’m Bryan Yeaton, and this
is The Weather Notebook.
There are actually two different types of waterspouts. The less common, but more
powerful is simply a tornado that forms over land, in the usual way, but finds its way
over water, sucking up H2O instead of dust and cows. But most waterspouts have a
much different life cycle than that of their tornadic cousin.
The waterspout does not need a supercell—or even a thunderstorm—to form. An
interim type of cloud, called cumulus cogestus, can spawn the spout. This classic,
heaping, cauliflower cloud may or may not grow into a cumulonimbus—the
thunderstorm cloud. Since they do not need the energy of such a violent system, these
whirls are often called "fair weather" waterspouts The waterspout spins downward
from this cloud, most often over shallow, warm waters, such as those along the Florida
coasts, although they have been observed off southern California and even in the Great
Lakes. The funnel is formed from water vapor condensing, not from water being pulled
up into the spout. A dark spot, and occasionally, spiraling patterns will form on the
water first, and the spout becomes visible as the funnel tightens, usually when winds
reach about 50 miles per hour.
Although many variations do occur, few waterspouts exceed 3000 feet in height, or
have a funnel greater than 150 feet wide. Most last about 15 minutes before they
become elongated and eventually dissipate.
The Weather Notebook is generously funded by Subaru of America. You can find any of
our past shows and Brainstorms online at www.weathernotebook.org. We are
produced by the Mount Washington Observatory.
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