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Hurricane Hazards and Society 1
A. Hazard and RiskB. Hurricane formationC. Comparing hurricanes and seasons
1. In this cartoon, what are the hazards?
2. How could the person minimize her risk from these hazards?
A. Hazard or Risk?
Geologic Hazard• Phenomenon capable of causing harm to
humans– Tsunami– Flood– Volcanic ash– Lahar– Fire– Liquefaction– Landslide
…. Can you think of others?
Primary Hurricane Hazards- Wind- Storm Surge- Rain- Waves
Secondary Hurricane Hazards(caused by a primary hazard)- Flooding- Fire - Landslides- Coastal Erosion
Risk
The likelihood of a hazard happening to YOUFactors: • Cost – human life– damage to property and infrastructure
• Probability– dependent on location– large events are generally less likely than small
ones Recall: Question for today…
B. Hurricane Formation:Ocean and atmosphere systems interact to
create hurricanes
• Make a list of hurricane characteristics:
What is a hurricane?
What is a hurricane?
• Formal definition:An intense low pressure system with sustained winds >74 mph
What makes a hurricane?
• 4 essential ingredients
What makes a hurricane?
1) Warm SST >26.5°C (80°F) over large area
What makes a hurricane?
1) Warm SST (>26.5 C) over large area
2) Instability in atmosphere (rising air mass)
What makes a hurricane?
1) Warm SST (>26.5 C) over large area
2) Instability in atmosphere (rising air mass)
3) Little/no vertical wind shear through troposphere
(Klotzbach and Gray, 2010)
What makes a hurricane?
1) Warm SST (>26.5 C) over large area
2) Instability in atmosphere (rising air mass)
3) Little/no vertical wind shear through troposphere
4) Sufficient latitude >5-10o off equator
Hurricanes are powered by
• latent heat stored in water vapor– released when water condenses
1. Warm water supplies sensible heat & humidity to overlying air
2. Air decreases density; rises3. Air cools; H2Ovapor condenses
4. Latent heat released-- Heat warms air; rises faster
5. P gradient increases -- Faster winds-- More water vapor into system!
Feedback between the ocean and atmosphere systems!
So… Can hurricanes cross the equator?
• Discuss with the person next to you. • Why or why not?
– Discuss with the person next to you. – Why or why not?
Can hurricanes cross the equator?
(Hurricane tracks 1851-2012; NASA)
North Atlantic Hurricane Season is June-November
Most storms occur in which month?
January
Febru
ary
Marc
hApril
May
June
July
August
September
October
November
December
0
0.5
1
1.5
2
2.5
3
3.5
4
Tropical StormsHurricanesHurricanes w/US Landfall
Ave
rage
num
ber p
er m
onth
, 185
1-20
11
Which of these things would cause a hurricane to lose energy?
a) Moving over colder waterb) Moving over warmer waterc) Making landfalld) Crossing the ocean
As a hurricane approaches land
Wind and rain
Storm surge
As hurricanes make landfall, they decrease in strength
Why?
Remember what fuels hurricanes…
Warm water!
SummaryHazard and riskWhat is a hurricane?
- What 4 conditions are necessary for hurricane formation?- What happens as hurricanes approach land?
Draw:
• the relationships between the ocean, atmosphere, and people in a hurricane