Transcript Hurricane PPT

*
Weather and Climate Unit
Investigative Science
*Normally peaceful, tropical oceans are capable of
producing one of Earth’s most violent weather
systems—tropical storms and Hurricanes!
*
*During summer and fall, the tropics experience
conditions ideal for the formation of large,
rotating, low-pressure tropical storms.
*In different parts of the world, the largest of
these storms are called hurricanes, typhoons, and
cyclones.
*
*Favorable conditions for cyclone formation exist
in all tropical oceans except the South Atlantic
and the Pacific Ocean off the west coast of South
America. The water in those two areas are cooler
and have nearly permanently stable air.
*
Click here for video: What are hurricanes, typhoons and cyclones?
https://www.youtube.com/watch?v=SSx_gisp24w
*
This map
shows where
every
hurricane (or
cyclone) has
tracked from
1851-2007
across the
Earth’s
oceans.
Click here for video: how hurricanes form https://www.youtube.com/watch?v=ajwUb2yNsvk
*Two conditions are needed to form a cyclone (or
hurricane):
*1) An abundant supply of warm ocean water
*2) Some sort of mechanism to lift warm air and
keep it rising
*Cyclones thrive on the tremendous energy in
warm, tropical oceans.
*
*Latent (stored) heat is stored in water
vapor. This latent heat is later released
when the air rises and the water vapor
condenses.
*This heat fuels the formation of larger and
larger tropical storms and hurricanes.
*
*The air usually rises because of some sort of existing
weather disturbance moving across the tropics.
*Many of these disturbances originate along the equator.
*Only a small percentage of tropical disturbances develop
into cyclones.
*
Warm, humid air
rises from the
surface of the
ocean, then cools
at high altitudes an
falls back to the
surface.
In the center of the
storm, the rising
column of air
leaves a low
pressure area (L)
that is the eye of
the storm.
*The first indication of a building tropical
storm is a moving tropical disturbance.
*A tropical disturbance is a large
thunderstorm with sustained winds of 37-62
km/hour.
*The Coriolis Effect causes the moving air to
turn and spiral.
*
*A tropical storm forms as winds increase to
speeds of 63-117 km/hour, strong
thunderstorms develop and become well
defined.
*
Click here for Hurricane Animation: http://pbs.pandaprod.cdn.s3.amazonaws.com/media/assets/wgbh/ess05/ess05_int_hurrlife/index.html
*With sustained winds of 118 km/hour, an
intense tropical weather system with welldefined circulation is now a cyclone
(hurricane).
*
Click here for video: Hurricanes
101http://video.nationalgeographic.com/video/101videos/hurricanes-101
*The storm develops around a calm center, called
the eye.
*The eye of the cyclone is a span of 30 to 60 km of
calm weather and blue sky.
*The strongest winds of the cyclone are
concentrated in the eyewall—a tall band of winds
that surround the eye.
*
Click here for video of the eyewall of Hurricane Katrina:
https://www.youtube.com/watch?v=eT5K6FR_eVs&feature=related
*A cyclone will last until it can no longer
produce enough energy to sustain itself.
*This usually happens when the storm has
moved over land or over colder water.
*
* There are many dangers associated with hurricanes:
* Storm Surge
* High Winds
* Heavy Rains and Flooding
* Tornadoes
* Rip Tides
*
* Storm surge is water pushed towards the shore by the force of
the winds surrounding a hurricane.
* The storm surge can combine with normal tides and increase
the water level by 30 feet or more.
* Storm surge can cause extensive damage, flooding, and loss of
life.
* Click here for a video about storm surge:
http://oceantoday.noaa.gov/hurricanestormsurge/
*
* n 2005, the storm surge from Hurricane Katrina left some parts
of New Orleans more than 20 feet under water.
* Much of New Orleans was below sea level and protected by
levees, massive earthen flood walls designed to keep high
waters out of the city.
* The surge overtopped the levees, destroying homes and killing
hundreds of people. Engineers caution that Katrina wasn’t even
a direct hit on New Orleans. They are working to protect the
city from the next big storm surge.
*
Click here for video: Hurricane Katrina, National
Geographic:
http://video.nationalgeographic.com/video/news/katrinaformation
*Strong winds are the most common means of
destruction associated with hurricanes. Their
sometimes continuous barrage can uproot trees,
knock over buildings and homes, fling potentially
deadly debris around, sink or ground boats, and
flip cars.
*
SaffirSimpson
Scale of
Wind Speed
and Damage
from
Hurricanes