HANDS-ON SAILOR99november/december 2016cruisingworld.comare actually quite common in tropical
waters. In fact, we were to encounter two
more of them weeks later, of the south
coast of St. Thomas in the U.S. Virgin
Islands.
Even so, I had no idea of which
conditions are conducive to waterspout
formation, how dangerous they are,
how long they typically last, or, most
importantly, how to avoid them when
sailing. None of the fellow cruisers I
spoke with could help either. So I decided
to call a few experts to get their thoughts
on the subject.
Joseph Golden is a retired National
Oceanic and Atmospheric Administration
meteorologist who is said to know
more about waterspouts than anyone
else in the world. Beginning in
1967, he helped document hundreds of
waterspouts in the Florida Keys over
roughly a decade-long period, even taking
measurements inside them from the
cockpit of a ruggedized World War II
training vessel.
While incidents of damage and loss of
life at sea from waterspouts are rare, there
are occasional documented examples.
Golden says that waterspouts can be found
virtually all over the world. Their “capital”
is Key West, where 100 to 500 of them
form each year from about mid-May to late
September within a 35-nautical-mile radius
of the city. Other waterspout hot spots
include the Bahamas and the Caribbean.
Most are “fair-weather” waterspouts,
tending to be relatively small. These are
usually short-lived, lasting no more than
about 12 minutes from formation to
demise. By contrast, tornadic waterspouts
are larger and can live up to 30 minutes,
Golden says.
The typical waterspout is between 10
and 20 meters in diameter, but the largest
of them can be 100 meters across. “Those
big ones are almost invariably going to be
the most dangerous,” he says.
Their destructive power is measured
with the same yardstick used for land-
based tornadoes: the Enhanced Fujita, or
EF, scale. Waterspouts are often weaker
than their land-based cousins, ranging
from EF0 to occasionally as high as EF2.
That’s still plenty dangerous, Golden
notes. At the top end, wind speeds can
reach more than 175 knots.
For fair-weather waterspouts to form,
all you need is sui ciently cool air over
warm water. Tornadic waterspouts
thrive on warm, humid conditions that
would normally produce thunderstorms,
explains Wade Szilagyi, director of the
Toronto-based International Centre for
Waterspout Research.
“Larger weather systems do not neces-
sarily have to be present,” Szilagyi says.
“However, cold fronts and squall lines are
favorable for waterspout development.”
Golden says large waterspouts usually
occur in a slightly disturbed environment.
“For example,” he says, “there may be
a weak tropical wave that’s af ecting
the Keys. The largest waterspouts that
I have documented occurred in those
conditions.”
Waterspouts develop most often
from about noon until late afternoon
or early evening, going through several
phases as they do so. They start out as a
dark spot on the water, distinguishable
from the air but not easily noticed from
the deck of a sailboat. The fi rst feature
noticeable from sea level is a swirling
column of wind-driven surface water
known as a “spray ring,” which precedes
the distinctive funnel vortex. Winds at
the base of the waterspout, even the
smallest ones, reach at least 45 knots,
Golden says. “Any sailing craft that is
caught in even a smaller waterspout is in
signifi cant danger,” he adds.
“It isn’t the winds that are going to hurt
you; it’s the fl ying debris from your own
boat,” Golden says. “I have seen reports
from cargo ships in the channel between
Taiwan and mainland China that have
been hit broadside and have had large
containers thrown around the decks,
doing a lot of damage.”
What should you do if you encounter
a waterspout at sea, as we did aboard
Symbiosis?
“Always move at right angles to the
apparent direction of a waterspout,”
Szilagyi advises.
But determining the direction of
travel takes a bit of skill. “If you hold your
index fi nger in front of the funnel and
it’s looming larger, sail or motor at 90
degrees, either right or left,” Szilagyi says.
“Keep in mind the relation of the spout to
any neighboring showers (at the water’s
surface). The funnel will tilt away from the
showers — that’s the direction it’s moving.”
Waterspouts’ speed of motion — 10
to 15 knots — is slower than land-based
tornadoes, but still much faster than
most of us can sail or motor. So don’t try
to outrun a waterspout along its axis of
forward motion.
If you should be so unlucky as to fi nd
yourself in imminent contact with a
waterspout, you could be dismasted, andk0RXQW*D\'LVWLOOHULHV/WG0RXQW*D\p
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Always move at right angles to the
apparent path of a waterspout. The
funnel of the spout will tilt away
from the accompanying showers,
which is in the direction it’s moving.