Friday, January 4, 2013

What's Up with Waterspouts?

What's up with waterspouts? Sometimes it's fish that go up with them, sometimes periwinkles, and sometimes just clay particles that mix with the condensed water in the funnel cloud and then fall as red water, also known as a "rain of blood." But more on that later...

First, let's take a closer look at this spectacular phenomenon.

Fair-weather waterspout

For as long as humans have observed and recorded events on and around large water bodies, the appearance of waterspouts has evoked superstition, fear, and even contributed to the romance of the sea. Sailors have attributed the phenomenon to sea dragons, sea serpents, and evil spirits. Arabian sailors believed them to be manifestations of Jinees--powerful spirits capable of assuming various forms.
The reality behind the myths and mysteries is twofold: some waterspouts are tornadic, formed from the same factors that result in terrestrial tornados, and others are fair-weather spouts.

Tornadic waterspouts drop down from thunderstorms, squall lines, or the leading edge of advancing cold fronts. Like the typical twisters seen in movies and on episodes of Storm Chasers, tornadic spouts have dark, sinister funnels spawned from large, turbulent "parent clouds."  These are seen most frequently at middle latitudes, off the lee shores of large landmasses where cold continental air sweeps over warmer water. Tornadic waterpouts are often bona fide land tornados that go to sea or cross large inland bodies of water. Tornadic spouts can form over water and come ashore as true tornados, and alike true tornados, they can abate and come back more than once.

Fair-weather waterspouts arise solely over water. They develop at sea level and climb skyward when humid, superheated air circulates convectionally with cooler overhead air. Fair-weather spouts tend to be smaller and of shorter duration than the tornadic variety and are considered relatively harmless. These prevail in equatorial regions, although they do occur in all latitudes during the transition seasons of spring and fall.

In the northern hemisphere, tornadic waterspouts rotate cyclonically (counter clockwise) with wind speeds of up to 130 mph. They can be quite long-lived, lasting on average 15-30-minutes. Their advancing speeds tend to be rather slow (less than 5 mph). Conversely, fair-weather spouts travel faster over a given distance, moving at speeds up to 30 mph, but their rotative speed is much lower. They also dissipate quite quickly, rarely lasting as long as 20-minutes. Fair-weather spouts may rotate in either direction, depending on the nature of the convection currents that form them.

Both types of waterspouts are quasi-seasonal at best. They're seen more frequently in temperate latitudes between May and October, and more in the deep tropics from October through March. Exceptions abound throughout the year in any locale.

String of waterspouts forming over Charlotte Amalie Harbor,
St. Thomas, USVI (2007).
Tornadic waterspouts are more dangerous and destructive since they form from storm clouds. The same dangerous conditions found with severe thunderstorms---strong winds, large seas, hail, and lightening--are commonly found around tornadic spouts. While tornadic spouts are the more dangerous of the two types of spouts, care should be taken when encountering either one of these natural phenomena.

Cool Waterspout Facts

  • The Great Waterspout of 1896 formed off Martha's Vineyard on August 19th of that year. Photographs and first-hand accounts from veteran mariners verified the spout was 144 feet thick and 3600 feet high. The spout formed not once, but three times within 45 minutes.
The Great Waterspout of 1896. (Photo from NOAA Image Library.)

  • A Tampa, Florida waterspout (June 13, 1952) caused over $75,000 in property damage when it came ashore with 100 mph winds. 

  • On September 5, 1935, a tornado/waterspout formed near Norfolk, Virginia and rampaged across Tidewater and Hampton Roads, where it flung railroad cars off their tracks before moving out to sea over the Chesapeake Bay.     

  • Waterspouts can form over freshwater in rivers and lakes, as well as saltwater bodies. Several have formed on the Hudson River over the last 100 years.

  • The longest recorded waterspout occurred off Eden, Australia on May 16, 1898. Theodolite measurements verified its height at 5,014 feet (although it was only 10' in diameter).

  • The widest waterspout on record was 700' wide, formed at Blunt's Reef, California on November 14, 1914.

  • Waterspouts have resulted in "rains" of fish, frogs, lizards, tadpoles, and periwinkles, most likely due to waterspouts coming ashore over low-lying marshlands and swamps.

  • Some waterspouts have resulted in a "rain of blood" when the spout churns up a nearby stretch of red mud or clay, mixing the particles with the spouts condensed water droplets that fall when the spout dissipates.


All At Sea.

Hendrickson, Robert. 1984. The Ocean Almanac. Doubleday Press. 446 pp.

National Oceanic and Atmospheric Administration.

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