2008 REED’s East Coast Edition - Weather
the normal easterly direction could indicate A significant number of North Atlantic
the approach of a trough or wave. As a tropical hurricanes, however, remain in the low lati-
wave approaches, you will see the wind back tudes and do not curve appreciably north-
from east to northeast and north. As the trough ward. Erratic tracks incorporating complete
passes, the wind will continue to back slowly loops, hairpin turns, and other irregularities
until it reaches a southeasterly direction. sometimes occur. In the North Atlantic, a
Using infrared sensors, weather satellites southeast track is rare, and when it does oc-
continually measure seawater temperature cur, it is only for a short duration.
and send the data back to earth stations. If The majority of hurricanes that move from
the sea surface temperature reaches 80°F the Atlantic into the Caribbean in August
early in the hurricane season, meteorologists and September instead follow a west-north-
at the National Hurricane Center become westerly course in low latitudes, often reach-
justifiably concerned, as this could signal a ing the U. S. East Coast before curving north
very active season. and northeast. In late September and in Oc-
Hurricanes generally cover a smaller area tober and November, hurricanes are likely to
than do extra-tropical depressions at mid- move to the north and east, passing through
latitudes. They range in diameter from less the Yucatan Channel or over Cuba, Florida,
than 100 to more than 500 miles. Centers, or the Bahamas. In October and November,
or “eyes,” range from four to 25 miles in movement of hurricanes is often toward the
diameter. The center is an area of very low north into the open Atlantic.
atmospheric pressure; in the Northern Some severe North Atlantic depressions
Hemisphere, winds spiral inward, or coun- that don’t originate in the tropics develop
terclockwise, around it. Spiral bands of in- sustained hurricane-strength winds and are
tense rain, thunderstorms, and waterspouts/ accorded hurricane status. Like other mid-
tornadoes emanate from the center and are latitude depressions, they are formed differ-
most prevalent at the eye wall. Winds at the ently than tropical hurricanes, but they can
outer edge of a fully formed hurricane are have equally devastating effects.
light to moderate, but gusty. They increase The average forward speed of North At-
toward the center to very high, sustained lantic hurricanes is 10 to 13 knots. However,
winds with even stronger gusts. Air move- this varies considerably according to the
ment within the eye itself is usually fitful location of the storm, its development, and
and sometimes nearly calm. However, seas in the surrounding meteorological conditions.
the eye are heavy and confused because the The highest rates off forward motion usually
winds surrounding the eye are shifting and occur when a hurricane is moving north or
violent. After the eye passes, hurricane-force northeast in mid-latitudes.
winds will resume blowing, this time from Hurricanes that form in the tropics at the
the opposite direction. eastern edge of the North Pacific Ocean tend
Hurricane Areas and Tracks
to follow a westerly path that misses the
North American continent. However, some
In the North Atlantic, most hurricanes form
do curve north, and then northeast, and
between the Cape Verde Islands near Africa
threaten the Baja peninsula and other parts
and the Windward Islands of the Caribbean,
of Mexico’s west coast.
over the western Caribbean, and over the
Gulf of Mexico (see Figure 6, next page).
Signs of Approach
While some North Atlantic hurricanes, One of the earliest signs of a hurricane’s
especially those that form southeast of Ber- approach is the appearance of high cirrus
muda, may initially move northward, the clouds. They will converge toward a point on
majority first move west or northwest. They the horizon that indicates the direction from
then often follow a track forming a large, which the hurricane is approaching. You will
right-hand (clockwise) curve. Some hur- see snow-white “mares’ tails” when the hur-
ricanes pass to the east or north of the larger ricane center is 300 to 400 miles away.
islands of the Caribbean, gradually turning Other early warning signs are long, heavy
to the northeast and east. Others pass over swells that can originate a considerable dis-
(or to the south of) the larger Caribbean tance away and reach you two or three days in
islands and enter the Gulf of Mexico where advance of the storm’s arrival. This swell comes
they curve to the north or northeast. from the general direction of the hurricane.
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