Download Hurricanes - Cobb Learning

Hurricanes
2010
Hurricanes
 A tropical cyclone that
occurs in the Atlantic.
 Also a generic term for
low pressure systems
that develop in the
tropics.
 Starts as a tropical
depression (winds less
than 39mi/hr).
 Becomes a tropical
storm and is given a
name when the winds
exceed 39mi/hr.
 Finally becomes a
hurricane when the
winds reach 74mi/hr.
How Hurricanes Form
 Form in warm, tropical waters.
 Water must be at least
80°F(27°C).
 Needs warm, moist air and
converging winds.
 Has a large difference in air
pressure.
 Formed by the heat energy and
as long as the water is warm are
self-sustaining.
 The moist, warm air circulates
around a well defined center.
 The lower the pressure at the
center, the faster the winds
will rush in to try to fill it.
Hurricane Formation
Parts Continued
 Eye: center of the hurricane.
Weather is calm, may be
clear, and will have no rain.
 Winds will come from the
opposite direction after the
eye passes.
 Rain bands will move counterclockwise around the eye.
These bands with hurricane
force winds can extend over
300 kilometers from the eye.
So the storms can affect a
wide area.
Parts of a hurricane

Hurricane
Movement
Hurricanes are steered
by the global winds.
 So the storms in the
tropics are steered to
the west by the trade
winds. When they get
far enough north the
westerlies take over
and steer them east.
 Once over land (or cold
water), they lose
strength as they no
longer have a source of
warm water to draw
energy from.
 Friction with the land
can slow the winds down
also.
Hurricanes die out when over
land or cold water as they have
no energy to sustain them.
Saffir-Simpson Hurricane Scale
 The Saffir-Simpson Hurricane Scale is a 1-5 rating
based on the hurricane's present intensity (wind speed).
 This is used to give an estimate of the potential
property damage and flooding expected along the coast
from a hurricane landfall.
 Wind speed is the determining factor in the scale
 Called Categories (Katrina was a Category 5 hurricane.)
Hurricane Damage
 Hurricane can cause
enormous damage when
they come ashore.
 While high winds do a
lot of damage, flooding
is more serious.
 Heavy rains cause
flooding, especially if
the hurricane is slow
moving.
 Storm surge is even
more serious. It is a
dome of water caused
by low pressure and high
winds. If it coincides
with the high tide, many
coastal areas will be
devastated.
Hurricane Names
 Since at least 1945, the
US Navy and later the
Air Force started
naming tropical cyclones.
 At first they used
exclusively English
female names, but since
1978 have started to
alternate male and
female names
(alphabetically).
 Different areas of the
world tend to use local
names for their areas.
Hurricane Names
 There is a six year
list.
 If they run out of
names in a year they
use the Greek
alphabet.
 Hurricanes that do
significant damage
will have their name
retired.
Atlantic Hurricane Names
Typhoons and Cyclones
Tropical Storm Warnings
 TROPICAL STORM
WATCH - Tropical Storm
conditions with sustained
winds from 39 -74 mph are
possible in your area within
the next 36 hours.
 TROPICAL STORM
WARNING - Tropical
Storm conditions are
expected in your area
within the next 24 hours.
Hurricane Warnings
 HURRICANE WATCH Hurricane conditions
with sustained winds of
74 mph or greater are
possible in your area
within the next 36
hours. Time to think
about evacuating!
 HURRICANE
WARNING - Hurricane
conditions are
expected in your area
within 24 hours. Past
time to evacuate!