Transcript Slide

Pg. 47
Hurricanes are a type of cyclone that form in subtropics –
use heat energy from ocean evap. at low latitudes= storm
(called typhoon in western Pacific) Low pressure system
NEED 1) WATER 80o in upper 200’-surface
2) Warm and humid air-unstable
3) upper level weak winds-same direction system is
already moving
4) wind at ground > 74 mph=hurricane
REMEMBER
Coriolis Effect-Winds in N. Hemisphere move
counterclockwise
Add pg. 47
STAGES OF DEVELOPMENT
GENERAL FORMATION-ND pg. 338 fig. 12.3
STEPS
1.) Tropical disturbance -low pressure zone that draws in
a poorly organized cluster of thunderstorms w/ weak
surface winds
2.) Tropical depression – surface winds intensify, receives
identifying number, storm begins to rotate counter
clockwise
a.) center air rises
b.) water vapor (lots of energy remember specific
heat) releases heat as condenses
c.) this heat is released and contributes to
further updrafts
Add pg. 47
STAGES OF DEVELOPMENT (continued)
3.) Tropical storm- when surface wind speeds reach 39mph
4.) Hurricane - when surface wind speeds reach 74 mph
Form at low latitudes, but not TOO low.
About 5o or closer to equator the Coriolis Effect is not
large enough to produce adequate rotation
ADD pg. 47
SO HOW MUCH HEAT WE TALKIN’?
The average hurricane generates energy at a rate
200 times greater than out worldwide capacity to
generate electricity
ADD pg. 47
ND pg. 338 fig. 12.3 again
THE EYE
1.) As more and more wind converges (now this is at the
surface) /comes rushing in at the center it becomes
difficult for all wind to reach the very center
2.) at 74 mph the eye forms hence hurricane status.
3.) Air in the center cools at altitude and sinks, but warms
as it descends-backwards/opposite-clear skies
4.) THE EYE WALL has the highest speed winds.
Pg. 47
Produce winds up to 150 mph and create storm
surge (raising sea level up to 20 feet) DEMO
Courtesy of
NOAA
Magazine
ADD Pg. 47
SO….
There are two components or ways to create storm surges
1.) low pressure (rising air) sucking up the ocean surface
2.) the storm system (cyclone) “bulldozing” the
ocean surface in front of the cyclone system
Here is a new site and animation describing storm
surge- Thanks Elizabeth
ADD pg 47
Different wind speeds at different points
DEMO
Storm motion
20 mph
Wind speed
120 mph
Right hand side
Storm Surge?
Bulge at center
Low pressure
Wind speed
80 mph
Left-hand side
Storm Surge?
Wind speed
100 mph
ADD pg. 47
Saffir-Simpson Hurricane Damage Potential Scale
LINK
1.) barometric pressure-why is this so important?
2.) wind speed
3.) storm surge
4.) damage
HOW are each of these things related?
THESEWILL BE ON THE TEST
STRONG AND WEAK HIGHES AND LOWSND pg. 340/ Table 12.1
DEMO
ADD pg. 47
HURRICANE ASPECTS
1.) Latent heat release from condensation of water vapor
inside a hurricane system is its main source of energy
2.) Hurricane weaken rapidly over land. WHY?
3.) Fronts are NOT associated with hurricanes. WHY?
4.) The weaker high altitude winds the stronger the
hurricane becomes. WHY?
5.) Hurricane centers are warmer than their
surroundings. WHY?
6.) Air in the very center sinks downward.
Air rises up eye wall. WHY?
Pg. 47 CASE HISTORY
ANDREW August 1992
Initially formed in Africa - moved over Atlantic and came
aground in Florida
Tornado-like vortices
Storm surge 17’-why so high? Predictable?
33 dead, 80,000 buildings destroyed
moved over Gulf of Mexico and hit Louisiana
killed 15 more
building codes had been in force.
Pg. 47 Continued
CASE HISTORY
ANDREW August 1992 Most destructive in US history
until???
30 billion dollars damage
Much of the loss could have been prevented if higher
standard
Pg. 48
CASE HISTORY
KATRINA
Evacuation dilemmas?
Population relationship?
NS pg. 351-knew of the problem.
Sept. 2004 Hurricane Ivan Cat. 4 caused evacuation
1 million people fled
72,000 in Superdome
But Ivan just missed we are safe now, whew!!!
SOCIAL-POLITICAL TIMELINE- I know, politics.
Liberal
Conservative
Another interesting take
Pg. 48
We knew the levees wouldn’t hold a Cat.4+to 5
We knew Cat. 5 are possible AND how hurricanes
destroy-storm surge New Orleans below sea level.
We knew Katrina was coming days in advance
(Governor, President, Mayor, Citizens)
We are the richest nation in the world.
WHAT IS/WAS THE PROBLEM??
CONSIDER AN EQ IN LOGAN HOW WOULD
YOU FEEL IF….
Pg. 48
HUGO - ATLANTIC COASTLINE 1989
Charleston, South Carolina
Hit land and moved north as tropical-storm intensity
11 people died
$7 billion in damage
ADDITIONAL CASE HISTORIES IN BOOK?
DON’T WORRY ABOUT IT
JUST FOCUS ON THESE
(IN NOTES AND SLIDES)
CROSS OUT IN NOTES
Pg. 48
BANGLADESH
1.) Densely populated-big numbers little area
2.) Country is low elevation delta
3.) nation of water
35% of nation is lower than 6m elevation
20% of land floods annually-rivers during wet season
1988-67% of nation was covered by river floods
THEN can cyclones and the 6m storm surges.
Bad set-up
Pg. 48
BANGLADESH continued
4.) Coastline is a funnel that catches and directs
cyclones up the Bay of Bengal
ND pg. 356 fig. 12.24
5.) Up to 400,000 people have died in cyclone
weather (single event)
VIDEO
THEN A COUPLE MORE EXAMPLES/PUZZLES
IF YOU UNDERSTAND THESE YOU WILL
DEFINITELY BE ON THE RIGHT TRACK