Flight Training - September 2013 - 39

maximum sustained surface winds reach
39 mph, a depression becomes a tropical
storm and hurricane forecasters give it a
name from a predetermined list. If a tropical storm’s sustained winds top 74 mph, it
becomes a hurricane.
Global-scale winds in the surrounding atmosphere, from the surface to
higher than 30,000 feet—called steering
currents—push tropical storms and hurricanes across the ocean and land until the
storm dies. Tropical storms and hurricanes
in the tropics or the subtropics move generally east to west or toward the northwest
from roughly 10 to 20 mph, with the path
often curving toward a more northerly
course. When hurricanes move north of
Cape Hatteras, North Carolina, they usually pick up forward speed.
A fully formed hurricane could be 300
miles across with a central eye usually
from 20 to 40 miles in diameter. The
nearly calm eye in the center is where
winds are light and the sky can be clear.
The storm’s strongest winds are in the ring
of thunderstorms around the eye—called
the eyewall. Rain bands spiral inward
toward the eyewall.
Winds blowing into a Northern
Hemisphere hurricane follow a counterclockwise path into the hurricane, with air
rising in the thunderstorms that make up
the spiral bands and the eyewall. This air
follows a clockwise path as it flows out of
the hurricane’s top.
If you own an airplane and live within
100 or so miles of the
U.S. Gulf of Mexico
or Atlantic Ocean,
monitor reports
from the National
Hurricane Center
during the hurricane
season. From June 1
to November 30, think
about what you would
do if a hurricane
threatens your area.
The closer you are to
the coast, the more
you should worry.
A hurricane’s winds

usually begin losing speed soon after
the storm hits land, but not always. On
September 22, 1989, Hurricane Hugo came
ashore at Isle of Palms, South Carolina,
as a Category 4 hurricane with 140-mph
winds. When Hugo’s eye crossed Charlotte, North Carolina, roughly 150 miles
inland, it was still a Category 1 hurricane
with 87-mph winds at the Charlotte
airport. A NOAA report says Hugo’s winds
“resulted in a nearly 50-mile-wide swath
of downed trees and power lines in this
portion of North Carolina. Pleasure boats
on Lake Norman, north of Charlotte, were
piled into a heap like toys.”
Consider whether a hangar that’s
available to you is likely to stand up to a
hurricane’s winds. A hangar that collapses could do more damage than an
airplane tied down would sustain from
flying debris. Your best choice might be to
fly your airplane to an airport far enough
inland to be safe. Your insurance policy
may cover the costs of moving the airplane
out of harm's way.
And you need to worry about flooding
as well as winds. When they move ashore,
hurricanes bring storm surge—water that
the wind pushes ashore. This can cause
major flooding, not only along the coast
but also on bays and rivers near an ocean.
Hurricanes also move ashore with heavy
rain that can cause floods far inland, especially in hills or mountains.

Before deciding to fly to an inland
airport you should check to see whether it
has a history of floods. You don’t want to
return to the airport to find your airplane sitting in six feet of water. You will
find links to information about storms
with graphical and text discussions and
forecasts on the Hurricane Center website
(www.nhc.noaa.gov). One of the most
useful set of products you’ll find on the
NHC website are the forecast maps such
as the one issued at 11 p.m. on October 26,
2012—three days before Hurricane Sandy
came ashore just north of Atlantic City,
New Jersey (below). The NHC produces
updated forecasts, including maps, every
six hours during a storm with more frequent updates as a storm nears land.
Using hurricane predictions is a matter
of playing the odds. Even though forecasts
have been getting better, you can’t count
on any one being perfect.
If you decide to fly to safety, you need
to realize that the hurricane might miss;
damaging winds might not hit your airport. Look at it this way: You are playing
the odds. You need to weigh the possible
costs of not flying the airplane away with
the potential costs of leaving it tied down
at an airport a hurricane could hit.
Jack Williams is an instrument-rated private pilot.
His latest book is The AMS Weather Book: The Ultimate
Guide to America’s Weather.

HURRICANE SANDY'S STORY
THIS IS THE National Hurricane Center forecast for Hurricane Sandy,
three days before it came ashore on September 29, 2012. The red dot
near the bottom is the location of the storm’s eye at the time the
forecast was issued. The black dots are the forecast eye locations at
the times noted. Those with an “S” show that the storm should be a
tropical storm with winds ranging from 39 to 73 mph. “H” shows it’s
forecast to be a hurricane with 74 mph and faster winds. The white
area is where the odds are 60 to 70 percent that the storm’s eye will
be during the first three days of the forecast. The area outlined with a
white line with white hatching is where the odds are 60 to 70 percent
that the eye will be on days four and five of the forecast. If Sandy’s
eye was on the western edge of the white area late Sunday and early
Monday, hurricane-force winds could hit North Carolina’s Outer Banks
and Norfolk, Virginia. The blue along the coast from South Carolina to
the North Carolina shows a tropical storm warning is in effect, which
means winds up to 73 mph are expected to hit this part of the coast.

SEPTEMBER 2013 FLIGHT TRAINING

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Flight Training - September 2013

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