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Chapter 11
Hurricanes
Hurricane Katrina Flooded 80% of New Orleans
The US’s deadliest hurricane in terms of deaths
happened in 1900 in Galveston, Tx. with 8000
who died. Due to continued developments along
the coastal areas, we see increased damages and
deaths.
Hurricane formations
• A hurricane must have sustained
wind speeds of at least 74 mph.
• The North Pacific has the greatest
number of storms per year
averaging 20.
• meteorological satellites have been
the greatest advancement in
observing tropical cyclones.
Equator lacks hurricanes
• Because the Coriolis effect is too
weak to create rotation.
What’s in a name?
• Hurricane – Hurricanes in the
Atlantic Ocean
• Typhoon – hurricanes in the western
Pacific Ocean.
• Cyclone – hurricanes in Indian
Ocean and Arabian Sea.
Tracks of Major Hurricanes
Form in the tropics where warm water
temperatures are found.
Storm Ratings intensity
•
•
•
•
Tropical storm– most intense
Tropical depression –
Tropical disturbance –
Tropical water – least intense
The Major Hurricane Formation Regions
are associated with the trade winds as a
general circulation wind belt.
Locations
• Most hurricanes form between the
latitudes of 5° and 20° over all tropical
oceans except the South Atlantic and
eastern South Pacific.
• Hurricanes do not generally strike the
west coast due to the colder water
currents.
Highest Winds at Eye-Wall
Lowest Pressure and Weakest Winds in Eye
Conservation
of
Angular
Momentum
is why the surface
wind speeds
increase toward the
center of a
hurricane.
Causes
• A steep pressure gradient generates the
rapid, inward spiraling winds of a
hurricane.
• As the warm, moist air approaches the
core of the storm, it turns upward and
ascends to form the eye wall.
• At the very center of the storm, called the
eye, the air gradually descends,
precipitation ceases, and winds subside.
Cross Section of a Hurricane
Development
• A hurricane is a heat engine fueled by the latent
heat when huge quantities of water vapor
condense.
• They develop in late summer when ocean
waters have reached temperatures of 80°F or
higher and are able to provide the heat and
moisture to the air.
• The initial stage of a tropical storm’s life cycle
is called a tropical disturbance.
• Tropical disturbances begin as large ripples in
the trade winds known as easterly waves.
The eye is the
warmest
part of the
hurricane, and
is free of
clouds due to
sinking air
motion.
Hurricane Intensity
• Hurricanes diminish in intensity
whenever they
• (1) move over cool ocean waters that
cannot supply warm, moist tropical air,
• (2) move onto land, or
• (3) reach a location where large-scale
flow is unfavorable.
Wind Speeds are highest at the eye-wall.
Fast winds are due to very strong
pressure gradient force.
Hurricane Damage
• Depends on the storms strength.
• The Saffir–Simpson scale ranks
the relative intensities of
hurricanes.
• A 5 on the scale represents the
worst storm possible, and a 1 is
the least severe.
Divisions of Hurricane Damage
• storm surge, is most intense on
the right side of the eye where
winds are blowing toward the
shore,
• wind damage, and
• inland freshwater flooding.
Storm
surges lead to the
greatest number of
hurricane related
deaths. Continued
damage is due to
the development
along the coastal
areas.
North Atlantic Hurricanes
• develop in the trade winds, which
move these storms from east to west.
• because of early warning systems
that help detect and track
hurricanes, the number of deaths
associated with these violent storms
have been greatly reduced.
Dropsonde Released
from Aircraft
into a
Hurricane used
for measuring
wind speeds
throughout every
level of a hurricane
Pilots Fly through Hurricanes Measuring Weather Elements
Doppler Radar
Image
3-D
Satellite
Image ..
The
conveyor
belt model.
meteorological data
• Collected by satellites.
• aircraft reconnaissance,
• radar, and
• data buoys.
Hurricane announcements
• hurricane watch, aimed at specific coastal
areas threatened by a hurricane, generally
within 36 hours.
• hurricane warning is issued when
sustained winds of 119 kilometers per hour
or higher are expected within a specified
coastal area in 24 hours or less.
• Two important factors in the watch and
warning decision process are (1) adequate
lead time and (2) attempting to keep overwarning at a minimum.
Chapter 11
END