FALSE WATERSPOUTS—A true waterspout—in other words, a tornado over a body of water—is a vortex in the atmosphere that in all cases forms at the cloud-level and works downward, says Charles Fitzhugh Talman, in his Science Service feature, “Why the Weather?” (Washington). As soon as the vortex reaches the water, the latter becomes violently agitated, sending up a rotating mound of spray, often before the spout as a whole becomes visible through the condensation of moisture from the air where a partial vacuum is formed by the centrifugal action of the vortex. He proceeds:

“Occasionally small whirlwinds start from the surface of lakes and other bodies of water in calm weather. Tho observers are likely to describe them as ‘waterspouts’ they are of quite a different nature from the phenomenon above described. They may build up a column of spray and vapor to a considerable height, but rarely extend to the clouds, and are sometimes seen when the sky is cloudless. These formations are similar in their mechanism to the little dust whirls that form over dry roads and the larger columns of dust and sand formed in deserts. On land such whirls are due to the overheating of the ground and the formation of a layer of stagnant warm air at the surface, which suddenly breaks through a colder layer above it.  A water surface does not heat up to any such degree as does a land surface, but it may remain warm while the air a few feet above it is rapidly cooled, giving the same unstable condition— warm-light air next to the water, and cold, heavy air at a higher level. In the moist air lying over water these surface whirls may form cloud columns by the condensation of water vapor, while similar whirls on land are made visible merely by the dust, dry leaves, etc- they carry.”

Source: The Literary Digest for October 29, 1927