Grade 12 Climatology. SA curriculum. Hurricanes.

1. What are the causes and effects of hurricanes?
Hurricanes
Click here for a playlist on hurricanes
By the end of this section, you will:
Know how hurricanes are formed.
How Hurricanes are named.
Weather patterns of Hurricanes.
Factors necessary for their
development.
The stages of development.
Long and short term effects.
Characteristics of a Hurricane.
Case study Hurricane Katrina.
Scoop It

2. FAMILY OF TROPICAL CYCLONES INFRARED SATELLITE PHOTOGRAPH

3. Hurricanes
What is a hurricane?
A violent cyclonic storm that develops in the tropical region
with wind speeds are > 74 mph lasting for several days.
In which direction does
a hurricane rotate?
Counterclockwise (NH)
Clockwise (SH)
Is the pressure inside the
hurricane high or low?
Low

4. How are hurricanes classified?

5. How do hurricanes form?
Source: http://www.boardworks.co.uk/

6. Hurricane formation
Source: http://www.boardworks.co.uk/

7. Naming of Hurricanes

8. Tropical Cyclone Structure
• Doppler radar showing
hurricane main parts:
– Eye
– Eyewall
– Rainbands.
• Counter-clockwise
rotation. (NH)
• In very center of the
storm, air sinks, forming
an "eye" that is mostly
cloud-free.

9. Necessary factors for the formation of Hurricanes
Complete the following details! Go into editing mode to do so.
Factor or Condition
Sea temperature of at least 27
Influence on formation process
C
Heat is needed for convection
High Humidity
Latent heat is released during condensation
Unstable Air
Unstable air to cause rising / convection of air
Little Surface Friction
Friction slows down the movement of the Tropical Cyclone
Light Variable Winds
Strong winds inhibit the development of the vortex
Low air pressure
Rising air associated with a LP is required for cloud formation
Divergence of air in upper levels
Stimulates circulation and the formation of votices

10. TROPICAL CYCLONE: DEVELOPMENT
Formative
Stage
pressure
ABOVE
1000 hPa
MATURE
Stage
pressure
WELL
BELOW
1 000hPa
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Developing
Stage
Pressure
BELOW
1 000 hPa
Degenration/
Dissipation
Stage
pressure
RISES

11. TROPICAL CYCLONE: ASSOCIATED WEATHER CONDITIONS
FORMATIVE STAGE
Complete the following details! Go into editing mode to do so.
AIR PRESSURE
TEMPERATURE
CLOUD COVER, RAIN
LP develops over the sea. Pressure is above 1000 hPa’s. Convergence of air. Vortex
forms
High temperatures and humidity that release latent heat and strengthen the LP.
Cirrus and Cumulus clouds. Light rain.
WIND
Winds in active quadrant reach speeds of gale force winds.
AREA INFLUENCED
Small area is influenced,20 km from the “eye”.

12. TROPICAL CYCLONE: ASSOCIATED WEATHER CONDITIONS
DEVELOPING STAGE
Complete the following details! Go into editing mode to do so.
AIR PRESSURE
TEMPERATURE
CLOUD COVER, RAIN
WIND
AREA INFLUENCED

13. TROPICAL CYCLONE: ASSOCIATED WEATHER CONDITIONS
MATURE STAGE
Complete the following details! Go into editing mode to do so.
AIR PRESSURE
TEMPERATURE
CLOUD COVER, RAIN
WIND
AREA INFLUENCED

14. TROPICAL CYCLONE: ASSOCIATED WEATHER CONDITIONS
DEGENERATION STAGE / DISSIPATING STAGE
Complete the following details! Go into editing mode to do so.
AIR PRESSURE
TEMPERATURE
CLOUD COVER, RAIN
WIND
AREA INFLUENCED

15. Stages of Development
How do you know a Hurricane is in the dissipating stage?
(Go into editing mode and complete the following:
1)
2)
3)

16. Most dangerous part of the Hurricane

17. Eye of a Hurricane

18. “Eye” of a Hurricane.

19. Development of Tropical Cyclones
3) As air rises, moisture
condenses out, warming air
and allowing it to continue
rising
1) Warm, moist
air spirals
towards center
of Hurricane
5) As pressures decrease,
winds intensify and even
more warm moist air is
forced to converge and
rise
2) Convergence of air
forces air to rise
L
4) As air rises, it causes even
lower pressures at the surface

20. In the short-term
Short-term effects will normally only last a few days or weeks.
They will not cause any lasting or permanent damage.
Examples may include:
slight damage to
land and/or buildings
temporary migration
of the population
a disruption to power
supplies.
Can you think of any other short-term
effects that might arise?

21. The long run
Long-term effects can include large-scale destruction of
property, or a complete alteration of the physical landscape.
These pictures show
the Chandeleur islands
in the USA before and
after Hurricane Katrina.
As you can see, their
geography has been
permanently altered by
the hurricane.
Can you think of any other long-term
effects that might arise?

22. Long and short term effects of Hurricanes
Fill in the Short and
Long-term effect!

23. Characteristics of a Tropical Cyclone
Equator/Ewenaar
From EAST to WEST
EYE
No wind, rain
& Clouds
DESTRUCTION
•Storm winds
•Torrential rain
•Flooding
Turns EAST at 30°
source: http://sageography.myschoolstuff.co.za
DISSIPATES
•No Moisture
•No warm air
•Friction

24. Characteristics of a Tropical Cyclone
NAME
Alphabet
Andrew
Bonny
Carl
Debora
MOVEMENT
ORIGIN
From E to W
In tropics
Away from
OCEANS
Equator
Not nearer
Turns east
than 5°N/S from at 30°
equator
IN EYE
No :
Wind
Clouds
Rain
DISSIPATION
Over land
No Moisture
No Warm air
Friction
WEATHER
Before eye
During eye
After eye
source: http://sageography.myschoolstuff.co.za
DESTRUCTION
Storm winds
Very hard
rain
Flooding
MANAGED
Sand bags
Early warning
Track storm
Services
Inform people
Evacuation

25. Characteristics of a Hurricane!
Complete the following details! Go into editing mode to do so.
Originate (Latitude):
Movement (direction):
Rotation:
Wind belt:
Diameter:
Weather:
Named:
Caused by:

26. TROPICALCYCLONE - MANAGEMENT
source: http://sageography.myschoolstuff.co.za

27. Preparing for the worst!
What precautions should be taken when there is a Hurricane warning!
Avoid crossing strongly-flowing rivers at causeways /drifts.
Dwellings very close to rivers / floodplains should be evacuated.
Farmers should move pumps away from rivers.
Small / medium sized fishing boats should return to port.
Small fishing boats should be moved well above the high water mark.
Listen to the radio / television for weather reports.
Listen to the advice of the local disaster risk management officials.

28. Hurricane Katrina
Hurricane Katrina was the most
powerful hurricane to hit the USA
in known history.
It hit New Orleans on the morning
of the 29th August 2005 bringing
with it terrible destruction.
New Orleans
Winds of over 250
kilometres per hour were
recorded as Katrina hit the
coast, causing a storm
surge 8.5 metres high.

29. Devastation
At first New Orleans seemed
to have weathered the worst
of the hurricane, but later
storm surges breached the
city’s protective levees.
People that had not left their
properties were stranded
and had to wait to be
rescued or wade through
polluted floodwater.
It was a hugely devastating natural disaster.

30. The aftermath
How badly did Hurricane Katrina affect New Orleans?
Flood levels were over six metres high.
80% of the city was flooded.
Over a million homes were left without electricity.
There were 700 deaths in New Orleans.
Over a million people had to leave their homes.
Damaged oil refineries spilt 24 million litres of crude oil.
Over $81 billion worth of damage was done.
Click here for a PowerPoint on Hurricane Katrina

31. In the news
Source: http://www.boardworks.co.uk/

32. You are the mayor
Source: http://www.boardworks.co.uk/

33. EXAMINATION QUESTION
Tropical
easterlies
•Coriolis force
•Warm water
•Moisture
•Land
•No warm
water
•Friction
1 Give ONE similarity between Hurricanes and Tropical cyclones on the map.
2
3
4
5
Explain the point of origin of both hurricanes and tropical cyclones on the map.
Why do these tropical cyclones move from east to west?
Why do tropical cyclones weaken as they move over Madagascar.
Why is the impact of tropical cyclones more severe in developing countries?
source: http://sageography.myschoolstuff.co.za