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.
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| 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.
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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.
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| 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.
Sources
All At Sea. http://www.allatsea.net/caribbean/water-spout-are-they-dangerous/
Hendrickson, Robert. 1984. The Ocean Almanac. Doubleday
Press. 446 pp.
National Oceanic and
Atmospheric Administration. www.noaa.gov
